Given in Loving Memory of
Raymond BraisUn Montgomery
Scientist, R/V Atiantis maiden voyage
2 July - 26 August, 1931
Woods Hole Oceanographic Institution-
Physical Oceanographer
1940-1949
Non-Resident Staff
1950-1960
Visiting Committee
1962-1963
Corporation Member
1970-1980
Faculty, New York University
1940-1944
Faculty, Brown University
1949-1954
Faculty, Johns Hopkins University
1954-1961
Professor of Oceanography,
Johns Hopkins University
1961-1975
i □
: D
D
m
a
THE BIOLOGICAL EFFECTS
OF
ATOMIC RADIATION
THE EFFECTS OF ATOMIC RADIATION ON
OCEANOGRAPHY AND FISHERIES
C.3
Report of the
Committee on Effects of Atomic Radiation
on Oceanography and Fisheries
of the
National Academy of Sciences
Study of the Biological Effects
of Atomic Radiation
MAHiNE
BIOLOGICAL
L'^BORATORY
LIBRARY
WOODS HOLE, MASS.
W. H. 0. I.
Publication No. 551
National Academy of Sciences — National Research Council
Washington, D. C.
4i. /IJ\ "(^
)9M
Library of Congress Catalog Card No.: 57-60049
COMMITTEE ON THE
EFFECTS OF ATOMIC RADIATION
ON
OCEANOGRAPHY AND FISHERIES
Roger Revelle, Chairtnan, Scripps Institution of Oceanography.
Howard Boroughs,
Hawaii Marine Laboratory.
Dayton E. Carritt,
The Johns Hopkins University.
Walter A. Chipman,
U. S. Fish and Wildhfe Service.
Harmon Craig,
Scripps Institution of Oceanography.
Lauren R. Donaldson,
University of Washington.
Richard H. Fleming,
University of Washington.
Richard F. Foster,
General Electric Company.
Edward D. Goldberg,
Scripps Institution of Oceanography.
John H. Harley,
U. S. Atomic Energy Commission.
BosTwiCK Ketchum,
Woods Hole Oceanographic Institution.
Louis A. Krumholz,
University of Louisville.
Charles E. Renn,
The Johns Hopkins University.
MiLNER B. ScHAEFER,
Inter-American Tropical Tuna Commission.
Allyn C. Vine,
Woods Hole Oceanographic Institution.
Lionel A. Walford,
U. S. Fish and Wildlife Service.
Warren S. Wooster,
Scripps Institution of Oceanography.
Consultants: Theodore R. Folsom,
Scripps Institution of Oceanography.
Theodore R. Rice,
U. S. Fish and Wildlife Service.
George A. Rounsefell,
U. S. Fish and Wildlife Service.
FOREWORD
The studies of the biological effects of atomic radiation, of which the report published
in this volume is a part, were undertaken by the National Academy of Sciences in 1955.
The first formal reports issuing from the study were published by the National Academy
of Sciences — National Research Council in June 1956 as "The Biological Effects of
Atomic Radiation — Summary Reports." These noted briefly the findings of six com-
mittees established to review broadly the status of knowledge in this field of vital im-
portance to the welfare of man at the threshold of the atomic age. They considered the
problem from the points of view of genetics, pathology, agriculture and food supplies,
oceanography and fisheries, meteorology, and the disposal and dispersal of radioactive
wastes.
The Academy study is a continuing one. Each of the Committees in a manner appro-
priate to its area of concern is pursuing its work.
The Committee on the Effects of Atomic Radiation on Oceanography and Fisheries
held two meetings prior to the publication of its "Summary Report": the first on March
3-5, 1956 and the second on April 13-16, 1956. Rough drafts of most of the materials
published in this volume were prepared at the second meeting. These reports, which
give the detailed technical background of the committee's findings and recommendations,
have been completed during the past year. Although the different chapters are signed
by individual authors, all members of the committee participated in planning and out-
lining the materials covered. Valuable editorial assistance was given by Dr. George A.
Rounsefell and Mr. Charles I. Campbell.
A similar report was prepared by the Committee on Pathologic Effects of Atomic
Radiation and published in the Fall of 1956 by the NAS-NRC as Publication Number
452. The Committee on the Disposal and Dispersal of Radioactive Wastes has nearly
completed a similar detailed report of its considerations.
After the publication of its Summary Report in June 1956, the Committee on the
Effects of Atomic Radiation on Oceanography and Fisheries met informally with scien-
tists from the United Kingdom on September 27 and 28, 1956. The discussions centered
around the recommendations that could be made on the basis of existing knowledge and
the nature of the research needed in planning disposal of radioactive waste at sea.
Members of this Committee have also participated in the preparation of a report by
Unesco to the UN Scientific Committee on the Effects of Atomic Radiation, concerning
the oceanic disposal of radioactive wastes.
As the use of atomic energy becomes more and more a part of our daily life it is
essential that thoughtful attention in broad perspective be paid to the often subtle and
perhaps profound effects of this new technology on man and his environment. The
Academy study will continue to provide this review and to report its findings to the
public when appropriate.
The facts upon which the study's conclusions are based result from more than two
decades of research which has been sponsored by the Academy and other private or-
ganizations as well as by various government agencies. The current study has been
financed by a grant from the Rockefeller Foundation. It has been greatly assisted by
the generous and whole-hearted co-operation of the U. S. Atomic Energy Commission
and other government agencies.
Detlev W. Bronk,
President, National Academy of Sciences.
TABLE OF CONTENTS
PAGE
Foreword vii
Contents ix
General Considerations Concerning the Ocean as a Receptacle for Arti-
ficially Radioactive Materials,
Roger Revelle and Milner B. Schaejer 1
Chapter 1. Physical and Chemical Properties of Wastes Produced by Atomic
Power Industry.
Charles E. Remi 26
Chapter 2. Comparison of Some Natural Radiations Received by Selected
Organisms.
Theodore R. Folsom and John H. Harley 28
Chapter 3. Disposal of Radioactive Wastes in the Ocean: The Fission Product
Spectrum in the Sea as a Function of Time and Mixing Char-
acteristics.
Harmon Craig 34
Chapter 4. Transport and Dispersal of Radioactive Elements in the Sea.
Warren S. Wooster and Bosttvick Ketchum 43
Chapter 5. The Effects of the Ecological System on the Transport of Ele-
ments IN the Sea.
Bostwick H. Ketchum 52
Chapter 6. Precipitation of Fission Product Elements on the Ocean Bottom
BY Physical, Chemical, and Biological Processes.
Dayton E. Carritt and John H. Harley 60
Chapter 7. Ecological Factors Involved in the Uptake, Accumulation, and
Loss of Radionuclides by Aquatic Organisms.
Louis A. Krnmholz, Edward D. Goldberg and Howard A. Boroughs . . 69
Chapter 8. Laboratory Experiments on the Uptake, Accumulation, and Loss
OF Radionuclides by Marine Organisms.
Howard Boroughs, Walter A. Chipman and Theodore R. Rice .... 80
Chapter 9. Accumulation and Retention of Radioactivity from Fission Prod-
ucts AND Other Radiomaterials by Fresh-Water Organisms.
Louis A. Krumholz and Richard F. Foster 88
Chapter 10. Effects of Radiation on Aquatic Organisms.
Lauren R. Donaldson and Richard F. Foster 96
Chapter 11. Isotopic Tracer Techniques for Measurement of Physical and
Chemical Processes in the Sea and the Atmosphere.
Harmon Craig 103
Chapter 12. On the Tagging of Water Masses for the Study of Physical Proc-
esses in the Oceans.
Theodore R. Folsom and Allyn C. Vine 121
Chapter 13. Large-Scale Biological Experiments Using Radioactive Tracers.
Milner B. Schaejer 133
ix
GENERAL CONSIDERATIONS CONCERNING THE OCEAN AS A
RECEPTACLE FOR ARTIFICIALLY RADIOACTIVE MATERIALS^
Roger Revelle and Milner B. Schaefer, Scripps Institution of Oceanography
and
Inter-American Tropical Tuna Commission, La Jolla, California
L Introduction
In this report, we have attempted to sum-
marize both the present knowledge and the
areas of ignorance concerning the oceans that
must be taken into account in considering the
biological effects of radiation.
[The oceans of the world furnish essential
sources of food and other raw materials, vital
routes of transportation, recreation, and a con-
venient place in which to dispose of waste ma-
terials from our industrial civilization. These
different ways in which men use the sea, how-
ever, are not always compatible. (The use of
the sea for waste disposal, in particular, can
jeopardize the other resources, and hence should
be done cautiously, with due regard to the pos-
sible effects. jWaste products from nuclear re-
actions require special care: they constitute
hazards in extremely low concentrations and
their deleterious properties cannot be eliminated
by any chemical transformations; they can be
dispersed or isolated, but they cannot be de-
stroyed. Once they are created, we must live
with them until they become inactive by natural
decay, which for some isotopes requires a very
long time.
Waste products from nuclear reactions arise
in two ways: (1) from the slow controlled re-
actions involved in laboratory experimentation,
in the production of materials for nuclear
weapons, the production of reactor fuels, and
the "burning" of fuels in power reactors; (2)
from the rapid, uncontrolled reactions involved
in testing of weapons or in warfare. Up to the
present time, the largest quantities of fission
products introduced into the aquatic environ-
ment have been from weapons tests; most of
the products from controlled reactions have
been isolated on the land, and only relatively
small quantities have been introduced into the
1 Contribution from the Scripps Institution of
Oceanography, New Series, No. 901.
sea or fresh water. In the future, however, in
dustrial nuclear wastes will present difficult dis-
posal problems and the sea is a possible dis-
posal site, particularly for small, densely popu-
lated nations with long sea coasts. We have,
therefore, given particular attention to the long-
range problems that may arise from the large-
scale disposal of both high-level and low-level
industrial wastes, as well as to the effects of
weapons tests.
Among the variety of questions generated by
the introduction of radioactive materials into
the sea, there are few to which we can give
precise answers. We can, however, provide con-
servative answers to many of them, which can
serve as a basis of action pending the results of
detailed experimental studies. The large areas
of uncertainty respecting the physical, chemical,
and biological processes in the sea lead to re-
strictions on what can now be regarded as safe
practices. These will probably prove too severe
when we have obtained greater knowledge. It
is urgent that the research required to formulate
more precise answers should be vigorously pur-
sued. Fortunately, the use of radioactive iso-
topes is one excellent means of acquiring the
needed information, and the quantities of these
isotopes required for pertinent experiments are
well within limits of safety. Moderate quanti-
ties of the very waste products we are concerned
with can, therefore, provide one means of at-
tacking the unsolved scientific problems.
II. The Nature of the Ocean and Its
Contained Organisms
The ocean basins cover 361 x 10'^ square
kilometers and have an average depth of 3,800
meters, giving a total volume of 1.37x10^
cubic kilometers. They are characteristically
bordered by a continental shelf, which slopes
gently out to a depth of about 200 meters. In-
side it is a steeper slope extending down to the
Atomic Radiatioti and Oceanography and Fisheries
deep sea floor with depths of 4,000 meters or
more. The average width of the continental
shelf is about 30 miles, varying from almost
nothing off mountainous coasts, such as the
West Coast of South America, to several hun-
dred miles in the China Sea. The shelf is not
everywhere smooth, but is often intersected by
submarine valleys and canyons. In the deep
ocean basins there are high mountains and long,
deep trenches, features larger than any on land.
Some of the deeper parts are isolated by sub-
marine ridges which restrict the exchange of
water between adjacent areas.
The waters of the oceans are stratified. Within
a relatively thin layer at the surface, varying in
thickness in different places but averaging
about 75 meters, vertical mixing caused by
winds is fairly rapid and complete. In conse-
quence, the temperature, salinity and density are
nearly uniform from top to bottom. Relatively
fast wind-driven currents exist in this upper
mixed layer; these are the "surface" currents of
the oceans depicted on many charts. Here also
the horizontal mixing is relatively rapid. The
mixed layer is the region of the sea in which
most of man's activity takes place.
Below the mixed layer is a 2one within which
the temperature decreases and the density in-
creases rapidly with depth. This thermocline,
or pycnocline, separates the surface mixed layer
from the layers of intermediate and deep water,
the latter extending to the bottom, within which
there are gentle gradients of decreasing tem-
perature and increasing salinity and density with
depth. Vertical movement in the intermediate
and deep layers is much slower than in the
mixed layer, and horizontal currents are more
sluggish. The strong density gradient across the
pycnocline tends to inhibit physical transport
across it, because work is required to move wa-
ter vertically in either direction, and thus the
pycnocline acts as a partial barrier between the
mixed layer and the lower layers. There is,
however, some interchange of both living and
non-living elements; indeed the continued ex-
istence of some marine resources depends on
such interchange.
MARINE RESOURCES
Living resources
I The most important extractive industry based
on the resources of the sea is the harvesting of
jits living resources.
On land the cycle of life is relatively simple;
we may describe it in four figurative stages.
First is the grass, which by a subtle and complex
chemistry captures the energy of sunlight and
builds organic matter. Sheep and cows live on
the grass; tigers and men eat them. The cycle
is closed by bacteria, which decompose the dead
bodies and the excreta of all living creatures,
making their constituent substances again avail-
able as building materials for the plants. In the
sea, the cycle is longer. Instead of grass there
are the tiny floating plants called phytoplank-
ton; in place of cows, the zooplankton animals
that eat the plants are small crustaceans, no
bigger than the head of a pin. Many kinds of
tigers eat the cows, but they are mostly also
zooplankton, only a fraction of an inch in
length. Other intermediate flesh-eaters exist
between them and the fishes of our ocean har-
vest. Because every link in this long food
chain is inefficient, we reap from the sea only
a small fraction of its organic production.
Other characteristics of the ocean also tend
to limit the harvest as compared to that from
the land. One is its giant size; more than 70
per cent of all the sunlight that penetrates the
atmosphere falls on the sea; moreover, this
sunlight can act throughout the top 20 to 100
meters, thus the living space for plants and
animals is far greater than on land. This great
areal extent and volume, combined with the
fluidity of the oceans, results in a low concentra-
tion oif organisms per unit volume and therefore
inefficiency in harvesting.
On land, the standing crop of plants and
animals is of the same order of magnitude as
the amount of organic production per year,
while in the ocean the crop is very small, com-
pared to the production, because of rapid turn-
over. The average rate of organic production
per unit area is probably about the same on land
and in the sea, but the efficiency of harvesting
depends more on the size of the crop than on
the total amount of organic matter produced.
The plants of the sea, on which all other liv-
ing things depend, grow only in the waters
near the surface where bright sunlight pene-
trates. These waters diflfer widely in fertility.
Like the land, the ocean has its green pastures
where life flourishes in abundance, and its
deserts where a few poor plants and animals
barely survive.
The fertility of the land depends on four
things: water, temperature, intensity of sun-
light, and available plant nutrients — substances
General Considerations
that usually occur in very small amounts but are
essential for plant growth. In the sea, water is,
of course, always abundant; the plants are well
adapted to the narrow range of temperature;
the intensity of sunlight determines the length
of the growing season and the depth of growth,
but usually not the differences in fertility. These
depend only on the plant nutrients in the wa-
ters near the surface. As in any well-worked
soil on land, the nutrients in the waters must be
replenished each year. They are continually de-
pleted by the slow sinking of plant and animal
remains from the brightly lighted near-surface
layers into the dark waters of the depths.
Men plow the soil to restore its fertility; the
fertility of the sea is restored when nutrient-rich
deeper waters are brought up near the surface.
The "plowing" of the sea is accomplished in
three ways. In some regions winds drive the
surface waters away from the coast or away from
an internal boundary, and nutrient-rich waters
well up from mid-depths. In other areas, the
surface waters are cooled near to freezing in the
winter, become heavy and sink, and mix with
the deep waters. Elsewhere, violent mixing
occurs along the boundaries between ocean cur-
rents, and deeper waters are thereby brought
into the brightly lighted zone.
The influx of nutrients to the upper layer,
and the corresponding loss from this layer by
sinking of plant and animal remains, do not
directly involve the deep waters. Upwelling and
vertical mixing take place only in the upper
few hundred meters. The exchange between
these mid-depths and the abyssal deep is a very
much slower process, of the scale of hundreds
of years.
Most of the commercially important marine
organisms are harvested in coastal waters or in
offshore waters not very far from land. Several
factors are involved: (1) Profitable fisheries
can be conducted more easily near ports and
harbors; (2) the coastal waters are of high fer-
tility, because of greater upwelling and turbu-
lent mixing and the ease of replenishment of
plant nutrients from the shallow sea floor, and
perhaps also because of the supply of nutrients
and organic detritus from land; (3) the stand-
ing crop of plants and animals attached to or
living on the bottom in coastal areas is large,
relative to the total organic production.
None of the animals of the great depths are
the objects of a commercial fishery. Even the
truly pelagic, high seas fisheries, such as the
great offshore fisheries for tuna, herring, red-
fish and whales, harvest animals that live pri-
marily in the surface layer. Some of these ani-
mals, however, do much of their feeding in
the deeper layers. The sperm whales, for ex-
ample, feed on deep-sea cephalopods at great
depths. Moreover, much of the food for com-
mercially harvested organisms consists of small
animals, including crustaceans, squids, and
fishes, that perform vertical diurnal migrations
from several hundred meters depth to the sur-
face.
The sea fisheries produce about 25 million
metric tons per year of fishes and marine in-
vertebrates, in addition to about 4 million tons
of whales. The great bulk of the harvest is
taken, at present, ifrom the waters of the north-
ern hemisphere, despite the fact that the south-
ern oceans constitute 57 per cent of the world's
sea area. The following table indicates the pro-
duction in 1954 by latitude zones:
TABLE 1 Harvest of Fishes and Marine
Invertebrates in 1954, by Latitude Zones
(From FAO, 1957)
Millions of
Zone metric tons %
Arctic region 1.2 5
Northern hemisphere-temperate
zone 17.5 72
Tropical zone 4.1 17
Southern hemisphere-temperate
zone 1.4 6
Antarctic regions 0* 0*
* About 4 million tons of whales were taken in the
Antarctic, but few fish or marine invertebrates.
The disproportionately large yield in the
northern hemisphere is related to three factors:
(1) Human populations are heavily concen-
trated there; (2) the major fishing nations are
the industrialized maritime nations, which are
mostly located in the north; (3) except for
some of the fisheries for tuna, salmon, her-
ring, and whales, the important fisheries are
located in the relatively shallow areas along the
continents, and the extent of these areas is much
greater in the northern than in the southern
hemisphere.
The sessile algae of shallow coasts are also
the object of important industries in Japan, the
United States, the United Kingdom, Norway,
and some other countries. Some of these plants
are used directly for human consumption, while
Atomic Radiation and Oceanography and Fisheries
others are employed indirectly in pharmaceutical
and food products.
Petroleum and natural gas
It is estimated that about 30 million cubic
meters of possible oil-bearing sediments underlie
the 11.8 million square miles of the submerged
continental shelves. These sediments contain
some 400 billion barrels of recoverable crude
oil.
Exploitation of these deposits of petroleum
and the associated natural gas has commenced in
the waters of the Gulf of Mexico; intensive
geophysical prospecting has been conducted off-
shore from California and in the Persian Gulf.
It may be expected that this source of fossil fuels
will be extensively utilized in the near future.
The resource is confined to the subsoil of the
marginal seas, since only there do we find oil-
bearing sediments.
Minerals
Extraction of sea salt for sodium chloride is
an ancient industry, and is now highly developed
also for production of sodium sulfate, potas-
sium chloride, and magnesium chloride. Bro-
mine is extracted directly from sea water for the
manufacture of ethylene dibromide. Magnesium
metal has been produced commercially from sea-
water by chemical and electrolytical procedures
for nearly two decades.
All of these industries use sea water taken
from near the surface at the shore but the
quantity of water utilized is insignificant. For
example, a single cubic kilometer of sea water
contains over a million tons of magnesium,
about five times the peak world annual produc-
tion of this metal.
The floor of the deep sea is known to contain
low-grade deposits of cobalt, nickel and copper
(0.1 to 0.7 per cent by weight of the metals)
associated with deposits of iron and manganese.
The problems of mining these materials, in the
face of the great depths and pressure, have not
been solved, and they certainly will not soon
be economically useable.
\
Ocean transportation
Long-distance transportation of large cargos
by sea is the indispensable basis of international
commerce. The economy of the United States
and of other industrial nations is in large part
dependent on the sea-borne commerce that flows
through the seaports.
Contamination of the sea by nuclear wastes
will certainly not present a hazard to shipping,
since acceptable levels of such materials in the
surface layer of the sea will be limited by other
considerations (such as the effects on the fish-
eries) to much lower levels than would consti-
tute a hazard to ships' personnel. On the other
hand, it is almost certain that nuclear power
plants will be extensively used in merchant ves-
sels; they are already in use in naval craft.
Serious hazards may arise in confined waters
from collisions in which the reactor is damaged
and the fuel elements with their contained fis-
sion products are lost in the water. Suppose for
example that a 50,000 kilowatt reactor (prob-
ably fairly typical for a large fast freighter)
has been in service without refueling for one
year on a ship that has spent half its time under
way. Approximately 10 kilograms of fission-
able material will have been used up and the
total amount of fission products will be ap-
proximately 10^ curies. If, owing to a collision,
the reactor is lost in a harbor, say 8 miles long
by 3 miles wide by 50 feet deep, and the fis-
sion products become uniformly distributed, the
water in the harbor would contain 10'^ curies
per cubic meter giving an almost constant radia-
tion dose of about 0.5 r per day on the surface.
Dock pilings, ship bottoms and other structures
covered with fouling organisms would accumu-
late a much higher level of radioactivity, and
local concentration in the water might be ex-
tremely high.
Recreation
For coastal populations in the temperate, sub-
tropical, and tropical regions, the sea and its
contents provide healthful sports and satisfac-
tion of men's curiosity and their desire for
beauty. Boating, swimming, sport fishing, and
other recreations are engaged in by millions of
people, and are the basis of tourist and service
industries of very considerable monetary value.
JV^aste disposal),
Disposal of domestic sewage and industrial
wastes is often conveniently accomplished near
coastal population centers by running them into
the sea. The large volume and rapid mixing of
the ocean waters dilute the wastes, and the bac-
General Cojisideratiojis
teria in the sea break down the organic con-
stituents. Unless care is exercised, however, this
discharge into inshore sea areas may be dele-
terious to other resources. Dumping of excess
volumes of sewage and industrial wastes, with-
out proper regard to the local characteristics
of the sea bottom, currents, and other factors,
has already resulted in ruining some harbors
and beaches for recreation, damage to the living
resources of adjacent areas, and even serious
problems of corrosion to ships.
The use of the sea for the disposal of atomic
wastes has, fortunately, been so far approached
with great caution and with due regard to the
possible hazards. The problems, because of the
dangerous character of small amounts of atomic
wastes, are of a different order of magnitude
than those of the disposal of other kinds of
wastes.
III. Potential Hazards From Radioactive
Materials
Direct hazards
A direct hazard to human beings from radia-
tion may exist if the levels of radiation in the
environment are sufficiently high.
The natural radioactivity of the sea is very
much lower than that of the land. According to
Folsom and Harley (Chapter 2 of this report) ,
a man in a boat or ship receives only about
half a millirad per year from the radio isotopes
in the sea, compared with about 23 millirads per
year from sedimentary rock or 90 millirads per
year from granite. Thus, it would be necessary
to increase the radioactivity of the sea many
fold to equal the radiation that man normally
receives from the land on which he lives. Due
to the rather rapid mixing in the upper layers
of the sea, and to its very large volume, even
large quantities of activity introduced at the sur-
face in the open sea become sufficiently dis-
persed to constitute no direct hazard after a
relatively short time, as has been shown by the
dispersion of the activity resulting from weap-
ons tests in the Pacific. If the direct hazard were
the only consideration, sea disposal of radioac-
tive wastes would give rise to difficulties only
in small areas near the disposal sites.
Some radioactive wastes have been disposed
of in the sea by placing them in containers de-
signed to sink to the sea bottom. In this way,
the wastes are isolated and not dispersed by the
ocean currents. Direct hazards could arise if
the containers in some manner were to come
into contact with humans, such as through ac-
cidental recovery during fishing or salvage op-
erations or if, through improper design, the
containers were to float to the surface and come
ashore.
Indirect hazards
The most serious potential hazards to human
beings from the introduction of radioactive
products into the marine environment are those
that may arise through the uptake of radio iso-
topes by organisms used for human food. There
are several reasons why these indirect hazards
are more critical than the direct hazards: (1)
The radiation received from a given quantity
of an isotope ingested as food is much greater
than the dose from the same quantity in the
external environment; (2) many elements, in-
cluding some of those having radioactive iso-
topes resulting from nuclear reactions, are con-
centrated by factors up to several thousand by
the organisms in the sea; (3) the vertical and
horizontal migrations of organisms can result
in transport of radioactive elements and thereby
cause distributions diflferent from those that
would exist under the influence of physical fac-
tors alone ; for example, certain elements may be
carried from the depths of the sea into the
upper mixed layer in greater amounts than
could be transported by the physical circulation.
It is quite certain that the indirect hazard to
man through danger of contamination of food
from the sea will require limiting the permis-
sible concentration of radioactive elements in
the oceans to levels below those at which there
is any direct hazard. Any part of the sea in
which the contamination does not cause danger-
ous concentrations of radioactive elements in
man's food organisms will be safe for man to
live over or in.
A reduction of the harvestable living re-
sources of the sea could conceivably occur
through the eff^ects of atomic radiations on the
organisms that are the objects of fisheries, or on
their food. This might result from mortality in-
duced by somatic eflfects, or from genetic
changes. There is no conclusive evidence that
any of the living marine resources have yet suf-
fered from either of these, and they are not
likely to be undesirably influenced at radiation
levels safe from other standpoints. The knowl-
Atomic Radiation and Oceanography and Fisheries
edge of radiation effects on marine organisms is,
however, inadequate for firm conclusions.
Pollution in general
The introduction of atomic wastes into the
aquatic environment is but one aspect of the
general problem of pollution.
Man's record with respect to pollution of
lakes, streams, and parts of the sea by sewage
and industrial wastes has not been good. In
many places, the waters have been ruined for
recreation and useful living resources have been
destroyed or made unfit for human consumption.
This unhappy record results from two factors:
(1) the insidious nature of pollution of the
aquatic environment, and (2) the fact that the
waters and most of their resources are not pri-
vate property, but are the common property of
a large community (in the case of the high seas,
the whole world) ; what is everyone's business
often becomes no one's business.
The ruin of an aquatic resource by pollution
seldom has been rapid. Quantities of waste
products, at first very small, increase year by
year until finally the concentrations become so
large as to have obvious deleterious eflfects. For
example, in the depletion of oxygen by organic
wastes, sharp critical levels of tolerance of low
oxygen content exist for some of the living re-
sources, so that there is little adverse effect until
a critical concentration of pollutant is reached,
whereupon catastrophic mortality occurs. In
other cases, the effects are more or less propor-
tional to the concentrations. The destruction of
a resource may then proceed gradually and it
may not even be clear whether the pollutant
has, indeed, been the cause rather than some
other environmental change. For these reasons,
it is necessary that the introduction of waste
materials of any kind into the aquatic environ-
ment be carefully monitored, so that the effects
may be detected before they become serious.
Unfortunately, such monitoring is seldom the
concern of those who produce the pollutants.
The record of the control and monitoring of
the disposal of atomic pollutants has, so far,
been excellent. We are, however, at the thresh-
old of a tremendous growth of the atomic energy
industry, and it behooves mankind to make sure
that as much caution is exercised in the future
as in the past.
Ordinary pollutants in sewage and industrial
wastes are rapidly neutralized by the chemical
and biological processes in the sea, and when
effects of pollution are detected they can be
rather quickly reversed by the cessation of intro-
duction of the waste. A number of the radio
isotopes, on the other hand, are very long-lived.
Having reached harmful concentrations in the
sea, they will diminish only by very slow decay,
so that the effect of any serious pollution is not
reversible. For this reason, the prevention of
atomic pollution is of paramount importance.
URGENCY OF THE PROBLEM
Estimates of the rate of economic develop-
ment of nuclear power vary widely. This
source of power is already competitive with
conventional sources in some places, and re-
search on reactor development with consequent
reductions in cost is proceeding rapidly. Thus,
we can expect that very large quantities of nu-
clear power will be generated in the quite near
future, even though the relative urgency of
nuclear power requirements differs greatly in
different countries. In countries with high costs
from conventional (fossil) fuels there is en-
couragement to proceed immediately with the
commercial construction of reactors of proved
design. In such countries as the United States,
where conventional power costs are low, major
efforts are being devoted to experimental con-
struction of new types of reactors that hold
promise of economical operation in the future.
One megawatt-year of heat produced by a
nuclear reactor results in 365 grams of fission
products. The Committee on Disposal and Dis-
persal of Radioactive Wastes, also a part of the
National Academy of Sciences' study of the bio-
logical effects of atomic radiation (1956), es-
timates that by 1965 the United States will be
generating about 11,000 megawatts of reactor
heat, some 20 per cent of which will be for
naval vessels. This will result in the produc-
tion of about 4 tons per year of fission products.
According to recent statements of government
officials, reported in Nucleonics (1957), the
United Kingdom has a 1965 target of 6,000
megawatts of electricity from Calder Hall-type
reactors; "Euratom" has a goal of 15,000 mega-
watts by 1967, and Japan will produce 1,000
megawatts by 1965 and 10,000 megawatts by
1975. If the reactors are of 25 per cent ef-
ficiency in conversion of heat to electricity (the
Calder Hall reactor has a net thermal efficiency
of 21.5 per cent. Nucleonics 1956), for each
General Considerations
1,000 megawatts of electrical power there will
be produced 1.46 tons per year of fission prod-
ucts. Thus, the fission products from the fore-
going programs will amount to: United King-
dom 8.8 tons, "Euratom" 21.9 tons, Japan 1.5
to 14.6 tons.
If we further assume that all other areas of
the world will in the next ten years develop
nuclear power equal' to the sum of that gen-
erated in the United States, Japan, the United
Kingdom, and "Euratom," there will be a total
of some 80 tons per year of fission products.
This represents, after 100 days' cooling, accord-
ing to the values given by Renn (see Chapter 1,
Tables 2 and 3), 3.9 x 10* megacuries of beta
radiation and 2.5 x 10* megacuries of gamma
radiation, or over Via of the total natural radio-
activity of all the oceans (Revelle, Folsom,
Goldberg and Isaacs 1955). The annual pro-
duction of the isotope of greatest long-range
hazard, strontium 90, will be 200 megacuries.
Craig (Chapter 3) has shown that a thousand
tons of fission products per year would result
from a 2.7-fold increase in the present world
energy consumption of about five million mega-
watts, if 10 per cent of this energy were derived
from the heat of nuclear fission at 50 per cent
efficiency. World energy consumption is now
doubling once every thirty years and a 2.7-fold
increase would be expected by about the year
2000. An annual production of a thousand tons
of fission products corresponds to an equilibrium
quantity of 7.7 x 10^ megacuries of radiation or
about 1.6 times the total natural radioactivity
of the oceans. The equilibrium amount of
strontium 90, plus its daughter yttrium 90,
would be 2.2 x 10^ megacuries. Carritt and
Harley (Chapter 6) have made calculations
based on an annual production of 4,000 tons of
fission products, corresponding to two million
megawatts per year of nuclear heat production
from fission. If no new sources of power, such
as thermonuclear reactions, become available,
this production would be expected in the very
early part of the twenty-first century because of
the limited world fossil fuel reserves.
Our knowledge of just what share of these
fission products can be safely introduced into the
oceans is woefully incomplete because we simply
do not know enough about the physical, chemi-
cal, and biological processes. If the sea is to be
seriously considered as a dumping ground for
any large fraction of the fission products that
will be produced even within the next ten years,
it is urgently necessary to learn enough about
these processes to provide a basis for engineer-
ing estimates.
As shown in the several chapters of this re-
port, the necessary information can be obtained
only by extensive fundamental research. In the
next decade we should attempt to learn far
more about the ocean and its contents than has
been learned since modern oceanography began
80 years ago.
Some of the required investigations of physi-
cal, chemical, and biological processes involve
the employment of naturally occurring or ex-
perimentally introduced radioactive tracers. Pol-
lution of the seas by the dumping of atomic
wastes, even at levels that are "safe" from the
standpoint of human health hazards, will make
such experiments progressively more difficult
because the presence of introduced pollutants
will add an unknown background variability.
The sooner the work can be commenced and the
cleaner our oceanic laboratory, the more precise
will be the experimental results. At the very
least, it is urgent that the details of any interim
introductions of radio isotopes be carefully doc-
umented, so that researchers can take account of
them in their investigations.
INTERNATIONAL IMPLICATIONS
The oceans and their resources cannot be
separated into isolated compartments ; what hap-
pens in one area of the sea ultimately affects
all of it. Moreover, the greater part of the
oceans and their contained resources are the
common property of all nations. Even the rela-
tively narrow territorial seas are amenable only
to juridical and not physical control; no nation
can effectively modify the natural interchange of
the biological and physical contents of its terri-
torial sea with those of the high seas or of the
territorial seas of other nations. The continuity
of the oceans, and their status as international
common property require that the oceanic dis-
posal of radioactive wastes be treated as a world
problem.
It is, first of all, urgent that the nations of
the earth formulate agreements for the safe
oceanic disposal of atomic wastes, based on ex-
isting scientific knowledge. Second, because of
the vastness, complexity, and immediacy of the
underlying scientific problems, it is important
that pertinent oceanographic research be intensi-
fied on a world-wide basis. Third, from the
Atomic Radiation and Oceanography and Fisheries
standpoint both of research and of proper con-
trol of this new kind of pollution, careful rec-
ords should be maintained of the kinds, quanti-
ties, and physical and chemical states of all
radio isotopes introduced into the seas, together
with detailed data on locations, depths and
modes of introduction. This can probably best
be done by national agencies reporting to an
international records center.
Although we are urgently concerned with
preventing possible deleterious effects of atomic
wastes, atomic radiations can also be of benefit.
Large-scale experiments employing radioactive
isotopes might contribute importantly to our
knowledge of the flux of materials through the
food chains from the phytoplankton to the
harvestable fishes, invertebrates, and whales
(Schaefer, Chapter 13 of this report). Such
knowledge will not only make possible assess-
ment of the ocean's potential for providing food
to mankind, but is a basic prerequisite for the
effective conservation of marine populations, to
permit maximum harvests to be taken year after
year. Other experiments using radioactive trac-
ers could lead to improved knowledge of the
processes of circulation and mixing in the sea
(Folsom and Vine, Chapter 12; Craig, Chap-
ter 1 1 ) . In both types of experiments, inter-
TABLE 2 Elements in Solution in Sea Water (Except Dissolved Gases) ^' 2
mg/kg
Element CI = \9.QQ%o
Chlorine 18,980
Sodium 10,561
Magnesium 1,272
Sulfur 884
Calcium 400
Potassium 380
Bromine 65
Carbon 28
Strontium 13
Boron 4.6
Silicon 0.02 -4.0
Fluorine 1.4
Nitrogen (comp.). 0.01 -0.7
Aluminum 0.5
Rubidium 0.2
Lithium 0.1
Phosphorus 0.001-0.1
Barium 0.05
Iodine 0.05
Arsenic 0.01 -0.02
Iron 0.002-0.02
Manganese 0.001-0.01
Copper 0.001-0.01
Zinc 0.005
Lead 0.004
Selenium 0.004
Cesium 0.002
Uranium 0.0015
Molybdenum 0.0005
Thorium < 0.0005
Cerium 0.0004
Silver 0.0003
Vanadium 0.0003
Lanthanum 0.0003
Yttrium 0.0003
Nickel 0.0001
Scandium 0.00004
Mercury 0.00003
Gold 0.000006
Radium 0.2-3 X 10
1 Sverdrup, H. U., M. W. Johnson
2 Revelle, R., T. R. Folsom, E. D
Total in oceans (tons)
2.66 X 10"
1.48 X 10"
1.78 X 10^
1.23 X 10^^
5.6
Xio"
5.3
Xio"
9.1
X 10'"
3.9
X 10"
1.8
X 10"
6.4
XIO"
0.028-5.6
Xio^
2
Xio'^"
0.14 -9.8
X 10"
7
Xio"
2.8
Xio"
1.4
Xio"
0.014-1.4
Xio"
7
X 10"
7
X 10"
1.4 -2.8
X 10"
0.28 -2.8
Xio"
0.14 -1.4
X 10"
0.14 -1.4
X 10"
7
Xio"
5.6
Xio"
5.6
Xio'
2.8
X 10"
2.1
XIO"
7
Xio«
<7
Xio«
5.6
XIO'
4.2
XIO'
4.2
XIO'
4.2
XIO'
4.2
X 10'
1.4
XIO'
5.6
Xio^
4.2
XIO'
8.4
XIO"
28
-420
Nuclide
K*
Rb^'
T J238
U235
Th===
Natural activities
Total (tons)
6.3 X 10'
56
Curies
4.6 X 10"
2.7 X 10'
1.18 X 10"^
8.4 X 10'
2.8
XIO"
3.8 X 10'
2.1
X 10'
1.1 X 10
1.4
XIO'
8 X 10'
Ra""
and R. H. Fleming, OCEANS (1942).
Goldberg, and J. D. Isaacs (1955).
4.2 X 10^
1.1 X 10"
General Considerations
national scientific cooperation will often be
essential for optimum results.
IV. Chemical Processes and Radioactive
Materials
Elements in sea water
Sea water is a solution of a large number of
dissolved chemicals containing small amounts of
suspended matter of organic and inorganic ori-
gin. The ratios of the more abundant elements
are very nearly constant, despite variations in
absolute concentrations in different parts of the
sea. Lower than average absolute amounts are
encountered in coastal areas and near river
mouths, while higher amounts are encountered
in areas of high evaporation, such as the Red
Sea. Vertical variations are usually small; in
general, in the open ocean in mid-latitudes, the
quantity of dissolved materials, measured by the
salinity, first decreases slightly with depth, then
increases slowly in the deep water.
Table 2 (from Carritt and Harley, Chapter 6)
shows the concentrations of some of the ele-
ments in solution in sea water at a chlorinity
of 19.00^0, which is near average for the sea,
and the total amounts in the ocean as a whole.
Also shown are the total amounts and total
radioactivity of the principal naturally occur-
ring radio isotopes. In addition to the listed
elements, there are variable amounts of dis-
solved gases, including nitrogen, oxygen, and
the noble gases. A range of values is given for
some elements present in small quantities, such
as nitrogen, phosphorus, silicon, iron, and cop-
per. These are substances necessary for living
organisms, and the inorganic phases may be re-
duced to nearly zero in surface waters where
they have been almost completely removed by
organic uptake.
Behavior of introduced materials
A number of things can happen to materials
introduced into the sea either in solution or as
particles. The particles may go into solution.
The dissolved substances may be precipitated as
particles of colloidal or larger size either by co-
precipitation with other elements, by sorption
on organic or inorganic particles already present
in the sea, or by interaction with other sea water
constituents. Both dissolved materials and par-
ticles may be ingested by organisms and enter
into the biochemical cycles.
Particles in the sea are continually removed
by settling out on the bottom. The rates of
settling depend on the size and density of the
particles, as modified by various physical and
biological factors.
Normal removal of elements from sea ivater
The results of geochemical studies provide
very approximate estimates of the fractions of
some elements supplied to the ocean that are
eventually removed from solution. In Table 3
TABLE 3 Geochemical Balance of Some Ele-
ments IN Sea Water (From Goldschmidt,
Quoted in Rankama and Sahama,
1950, Table 16.19)
Amount
Total
present
supplied
in ocean
Transfer
ement
(ppm)
(ppm)
percentage
Na ...
16,980
10,560
62
K ....
15,540
380
2.4
Rb ...
186
0.2
0.1
Ca ...
21,780
400
1.8
Sr ....
180
13
7.2
Ba ...
150
0.05
0.03
Fe ...
30,000
0.02
0.00007
Y
16.9
0.0003
0.002
La ...
11
0.0003
0.003
Ce ...
27.7
0.0004
0.001
are listed a number of elements, including some
of the elements having long-lived fission-product
isotopes, with their concentrations in the supply
to the ocean and in the ocean itself. Assuming
steady-state equilibrium, the ratio of the con-
centration in the ocean to the concentration in
the supply, the transfer percentage, indicates
what share of the supply stays in solution. Large
values of the transfer percentage indicate that
a relatively large fraction remains dissolved;
small values indicate that relatively much is
removed.
These data give no information on the re-
moval processes or on the time rate of removal.
The latter can be obtained from estimates of
rates of natural sedimentation together with
chemical analysis of sediments or from study of
rates of sedimentation of radio isotopes follow-
ing weapons tests or waste disposal operations
(Carritt and Harley, Chapter 6) .
Goldberg and Arrhenius (in press), from a
study of natural sediments, have estimated resi-
dence times in the ocean for several elements.
They conclude that one half the amount of
10
Atomic Radiation and Oceanography and Fisheries
strontium present at a given time is deposited
in the sediments in about ten million years. For
other elements the residence times relative to
strontium are roughly proportional to the trans-
fer percentages. Thus they estimate that the
residence time for iron is of the order of a hun-
dred years.
Introduction of radioactive materials
Radioactive materials in large quantities can
be introduced into the sea from reactor wastes,
from weapons tests, or in warfare.
gradients of specific activity decreasing from
the sites of introduction, and depending on the
mixing characteristics of the ocean.
Nuclear explosions have been the principal
source of fission products introduced into the
sea to date. The total quantity of fission power
from such explosions so far may be estimated
at 40 to 60 megatons of TNT equivalent, from
the data summarized by Lapp (1956). This
corresponds, with 20 kilotons equal to 1 kilo-
gram of fission products (Libby, 1956a), to
two to three metric tons of fission products.
TABLE 4 Fission Product Activity After 100 Days Cooling From 10" Megawatt Hours of Nuclear
Power Production i
Curies at Specific activity
Isotope Half-life Tons (metric) 100 days curies per ton 2
Kr^ 94 y 7.3 3.3 X 10' —
Sr"* 55 d 86 2.3 X 10'' 0.128
Sr^ 25 y 463 7.5 X 10'" 0.0042
Y*° 62 h — 7.48 X 10'" 178
Y"' 57 d 111 2.8 X lO'' 6,660
Zr'' 65 d 152 3.2 X 10" —
Nb"^ 35 d 161 6.3 X lO'" —
Ru'"^ 45 d 46 1.3 X lO'" —
Rh"^ 57 m — 1.3 X 10'° —
Ru'"" 290 d 35 1.5 X 10" —
Rh'"« 30 sec — 5.15X10'° —
I'" 8.0 d — 5.2 X 10' 0.0743
Cs"*' 33 y 705 5.63 X 10'° 20.1
Ba"' 2.6 m — 5.1 X 10'° 0.728
Ba"° 12.5 d 2 1.5 X 10" 2.14
La"° 1.7 d — 2.5 X 10" 595
Ce"' 28 d 45 1.5 X 10" 268
Pr'" 13.8 d 2 1.4 X 10" —
Ce'" 275 d 490 1.6 X 10'° 386
Pr'" 17 m — 2.4 X 10'° —
Pm'" 94 y 7.3 3-3 X 10' —
Sm'" 73 y 0.7 2.0 X 10^ —
1 Adapted from data of Culler (1954) and Revelle et al. (1955).
2 Based on tonnage shown in Table 2.
In Table 4 is a listing of the important fis- The amount of fission products reaching the
sion products, their half-lives, and the quantities sea from nuclear explosions depends on a num-
resulting from 10^^ megawatt hours of nuclear ber of factors such as the location of the burst,
power production (Carritt and Harley, Chapter the distance above (or below) the surface, and
6). The column "specific activity" shows the the size of the weapon or device. For the
ratio of the quantity of radioactivity of a par- smaller devices with a TNT equivalent of
ticular isotope to the total amount of isotopes several kilotons, most of the fallout is immedi-
of that element in the sea for this amount of ate and local, although an appreciable fraction
energy. The specific activity will, of course, remains in the troposphere for a few weeks
be lower for smaller amounts of fission. It is (Libby, 1956a, b). Subsurface explosions will
also obvious that a uniform specific activity in result in local deposition of a larger fraction of
all parts of the sea would be obtained only if the fission products; a deep underwater burst
the fission products were evenly distributed, will deposit practically all of the activity locally,
Since, under any practical method of introduc- with nearly /, being in the surface layer and
tion, this will not occur, there are bound to be about § below (Revelle, 1957). In the case of
General Considerations
11
large, megaton devices, half or more of the total
fission products are injected into the strato-
sphere from which there is a slow leakage into
the troposphere (of the order of 10 per cent
per year) and subsequent fallout fairly evenly
over the entire northern hemisphere, with lesser
amounts in the southern hemisphere (Libby,
1956a, b). Of this long-term fallout, up to 71
per cent falls on the oceans, since this is the
proportion of the earth's surface covered by
them. (The proportion of land to sea is higher
in the northern hemisphere than in the south-
ern, and since most of the long-term fallout
occurs in the northern hemisphere, the amount
entering the ocean will be less than 71 per
cent.) On the other hand, some of the fallout
on the land will eventually reach the sea
through land drainage or river runoff.
Except in the case of deep underwater bursts,
all of the fission products reaching the sea
from weapons tests are deposited in the upper
layer of the ocean. Removal into the deeper
water is relatively slow. Despite the rapid mix-
ing within the upper layer by vertical and hori-
zontal wind stirring, the products from a large
weapon remain in measurable concentrations
over many months. A survey made 13 months
after the 1954 weapons tests in the Pacific
showed low-level activity over a vast area (Har-
ley, 1956).
Radio isotopes in fallout on the land remain
largely in the upper few inches of the soil. Fall-
out on the sea, on the contrary, is rapidly dif-
fused through the upper mixed layer, some 75
meters deep on the average. Consequently, for
conditions of equal fallout, the concentrations
of radio isotopes in the part of the sea from
which they are taken up by man's food organ-
isms are less than in the soil. Thus, even
though the calcium concentration of sea water
is lower than in most soils, the ratio of stron-
tium 90 to calcium in the marine environment
is now much less than in agricultural lands of
the mid-western United States. In 1955 (Libby
1956b) these soils contained about .025 micro-
curies of strontium 90 per kilogram of calcium
available to growing plants. Revelle (1957)
has calculated that for an equal amount of
widely distributed fallout (from approximately
25 megatons TNT equivalent of fission) about
.00015 microcuries of strontium per kilogram
of calcium would be present in the upper mixed
layer of the sea, half of one percent of the
amount in soils.
In addition to fission products, neutron ir-
radiation of elements in the environment im-
mediately after the detonation produces other
radioactive isotopes. With ordinary land or
marine materials, the amounts of this neutron-
induced radioactivity are small (Libby, 1956a).
However, soon after the 1954 tests in the
Pacific, quantities of zinc 65 were discovered in
marine fishes, and subsequently cobalt 60 was
recovered from clams in the Marshall Islands.
These isotopes probably originated from neu-
tron irradiation of metals, other than the fis-
sionable materials, in the test device.
Comparison of table 2 and table 4 demon-
strates that the mass of radioactive isotopes in-
troduced into the sea from weapons tests, or
which might be introduced from disposal of
waste products, will be very small compared
with the amounts of their normal isotopes al-
ready present. The introduction of the radioac-
tive material does not, therefore, appreciably
modify the chemical and physical properties of
normal seawater, so that the chemistry of the
introduced radioactive substances is the same as
for the corresponding non-radioactive isotopes
in the sea.
Introduced radioactive isotopes will partition
into a soluble and an insoluble fraction. The
physical states of a given element under equi-
librium conditions depend upon whether or not
the solubility product of the least soluble com-
pound has been exceeded. Since the ionic ac-
tivities of the elements in the complex chemical
mixture that is sea water are not accurately
known, it is difficult to attack this problem from
theory. Greendale and Ballou (1954) have de-
termined the distribution among soluble, col-
loidal, and particulate states of important fission
product elements by simulating the conditions
of an underwater detonation; their results are
given in Table 5. Elements of Groups I, II, V,
VI and VII usually occur as ionic forms, while
other elements, including the rare earths, occur
as solid phases. Some of these results have been
confirmed by field observations following weap-
ons tests (see Chapter 6 of this report by Carritt
and Harley, and Chapter 7 by Krumholz, Gold-
berg and Boroughs). Those elements in Table
5 that have sufficiently long half-lives to con-
tribute a significant share of the total activity
after one year of decay are marked with an
asterisk. Cesium 137 and strontium 89 and 90
12
Atomic Radiation and Oceanography and Fisheries
remain in solution, while ruthenium 106,
cerium 144, zirconium 95, yttrium 90 and 91,
and niobium 95 are largely in the solid phase.
The solid fractions, whether they be chemi-
cal precipitates or solids produced by accumula-
tion in the bodies of organisms, will tend to
settle out. As they settle, they may encounter
environmental conditions which will prevent or
hinder deposition. There will be, however,
some net transport toward the deeper water and
the bottom from the settling process. Because
of biological uptake, the removal of the par-
TABLE 5 Physical States of Elements in Sea
Water 1 (From Greendale and Ballou, 1954)
Percentage in given
physical state
Element Ionic Colloidal Particulate
Cesium * 70 7 23
Iodine 90 8 2
Strontium * 87 3 10
Antimony 73 15 12
Tellurium 45 43 12
Molybdenum 30 10 60
Ruthenium * 0 5 95
Cerium * 2 4 94
Zirconium * 1 3 96
Yttrium * 0 4 96
Niobium * 0 0 100
1 Elements introduced by simulated underwater
detonation of atomic bomb, Greendale and Ballou,
1954.
* Indicates element has important fission product
isotope.
tides from the upper layers of the sea may be
quite slow. For example, cerium 144, a rare
earth which has a half-life of 275 days, and
which is present in the sea primarily in particu-
late form, and its daughter Pr 144 were found
to account for 80 to 90 per cent of the activity
in plankton samples from the upper layer taken
in the Pacific by the TROLL survey 1 3 months
after weapons tests (Harley, 1956).
A very rough idea of the reduction in ac-
tivity that would eventually be obtained by
removal from the ocean can be gained from the
transfer percentages of Table 3. The fraction of
an introduced fission product remaining in the
sea will, at equilibrium, be equal to or greater
than the transfer percentages for the correspond-
ing element. (The transfer percentage reflects,
in part, retention on land as well as sedimenta-
tion from the sea.) An important factor is
the time required for equilibrium to be reached ;
if it is very long in relation to the half-life of
the element in question, reduction of activity
may be negligible. The long-lived and danger-
ous isotope, strontium 90, has a relatively high
transfer percentage and a long equilibrium or
"residence" time; the same would be expected
for cesium 137, which is an alkali and should
behave somewhat like potassium or rubidium.
Disposal of atomic wastes by deep sea burial
in various sorts of packages has been proposed.
Dispersion of the activity would then be by
slow diffusion from concreted wastes, or would
be delayed until rupture of an impermeable
container occurred. Because the deep ocean
sediments have appreciable exchange capacities,
much of the wastes would be retained in this
highly absorptive environment. The upper lay-
ers of the sediments would, presumably, tend
to become saturated, and the further removal of
radioactive elements by exchange or absorption
would be controlled by the rate of diffusion into
the deeper sediments.
There are wide gaps in our knowledge of
many of the processes mentioned above. These,
and suggestions for research needed to fill them,
are discussed by Carritt and Harley (Chapter 6) .
Much of the required information can be ob-
tained by the use of radioactive tracers, intro-
duced in weapons tests and experimental waste
disposal operations, as well as in purposive
experiments.
V. Physical Processes and Radioactive
Materials
Physical structure of the sea
The physical properties of sea water of im-
portance to the present study are functions of
temperature, salinity, and pressure. The tem-
perature ranges from about 30° C to about
— 2 ° C, which is the initial freezing point. The
highest temperatures occur at the surface or in
the mixed near-surface layer; below this the
temperature decreases to about 5° C at 1,000
meters and to 1° to 2° at greater depths. In
the deepest parts of the ocean there is a slight
increase of temperature due to adiabatic heat-
ing. Hydrostatic pressure increases about one
atmosphere for each 10 meters of depth. In
the open ocean in mid-latitudes the salinity gen-
erally decreases slightly with depth in the upper
few hundred meters, then increases slowly. In
high latitudes the salinity normally increases
with depth throughout the water column.
General Considerations
13
The density of sea water increases with de-
creasing temperature and with increasing sahnity
and pressure. Except in quite dilute sea water,
the temperature of maximum density is lower
than the freezing point. The range of density
in the open sea is between about 1.02 and 1.06.
It may, of course, be lower in inshore waters
in the vicinity of river mouths. At constant
pressure the major changes in density in the sea
are associated with temperature, so that to a
first approximation the change of density (com-
puted for constant pressure) with depth is in-
versely proportional to the change of tempera-
ture.
Many processes in the sea depend on the
density distribution. The ocean basins are
largely filled with water of relatively high
density formed in high latitudes ; overlying this
dense water in middle and low latitudes, and
separated from it by the pycnocline, is the sub-
surface mixed layer, varying from a few meters
to several hundred meters in thickness but
averaging about 75 meters, of water of high
temperature and low density. The relative rate
of change of density with depth may be taken
as a measurement of the vertical stability of
the water (Sverdrup, Johnson and Fleming,
1942, p. 417). Stability in the region of the
pycnocline is much higher than above or below
it, so that exchange of water across it tends to
be small.
All parts of the ocean and its bordering seas
are in communication with each other, and are
in continuous motion. The rates of movement,
however, differ greatly in different areas. Thus,
although there is eventual complete interchange
of water between all oceans and seas, some parts
are partially isolated from others, the exchange
between these parts being much slower than
within them.
Near-surface currents and mixing within the
upper layer
Currents in the upper, mixed layer of the
sea are primarily generated by winds, and, con-
sequently, the major horizontal surface currents
of the ocean correspond to the field of wind
stress (Munk, 1950). The average locations and
velocities of the important surface currents are
well known from numerous observations of
merchant ships and research vessels, and appear
on many charts.
The velocities and volume transports of the
major near-surface currents are large. For ex-
ample, the mean speed of the Florida Current
is about 193 cm/sec. and of the Kuroshio about
89 cm/sec. The volume of water flowing
through the Florida Straits in 15 years is equal
to the volume of the upper 500 meters of the
whole North Atlantic, and the transport of wa-
ter by the Kuroshio between the Northern
Ryukus and Kyushu in 50 years is equal to the
upper 500 meters of the whole North Pacific.
Because of the large surface currents, intro-
duced materials tend to be carried away from
the sites of introduction to other parts of the
upper mixed layer of the sea. Thus, no area of
surface water in the ocean is isolated for long
periods from the remaining areas.
The currents are not steady streams, but have
a complicated fine structure, with many eddies,
jets, and filaments. In consequence of this
turbulence, on both large and small scales, dis-
solved materials in seawater are rapidly dis-
persed horizontally. The rate of dispersion is
about a million times the rate of molecular dif-
fusion, and depends on wind speed, current
shear, vertical and horizontal density gradients,
direction of dispersion, and the dimensions of
the area considered. Because of this large num-
ber of variables and the lack of knowledge of
turbulent processes, it is not possible to predict
accurately the horizontal dispersion in particular
areas. If even moderately precise values are re-
quired, experiments must be conducted in the
area of interest. Some of the results of such
studies are reported by Wooster and Ketchum
(Chapter 4) .
The rate of vertical diffusion in the upper,
mixed layer, although much less than that for
horizontal dispersion, is nevertheless about a
thousand times greater than molecular diffusion.
The extent of vertical stirring in the upper layer
depends on the magnitude and uniformity of
the wind stress and on the vertical density gra-
dient. Convective processes, and, in coastal
areas, strong tidal currents, also contribute to
vertical mixing. The mixing rate in the upper
layer has been measured by changes in the ver-
tical distribution of radio isotopes following
weapons tests. Revelle, Folsom, Goldberg, and
Isaacs (1955) report that in one such test the
lower boundary of the radioactive water moved
downward at about 10"^ cm/sec. until it reached
the thermocline, where it abruptly stopped.
14
Atojjik Radiation and Oceanography and Fisheries
Circulation and mixing within the intermediate
and deep layer
Within the pycnodine and for some distance
below it, it is believed that most of the motion
takes place along surfaces of constant potential
density, so that transport and diffusion in the
lateral direction are very much greater than in
the vertical. This belief has been confirmed by
experiments with radioactive tracers, reported by
Revelle, Folsom, Goldberg, and Isaacs (1955),
in which it was shown that the radioactive wa-
ter spread out over an area of about 100 square
kilometers while maintaining a thickness of the
order of a few meters.
Much of our knowledge of deep and inter-
mediate currents has been inferred from the
distributions of properties. These indicate that
the average velocities of the deep currents are
only a few cm/sec. or less. However, Wiist
(1957) has recently made calculations on data
from the Atlantic which indicate velocities of
meridional currents of 3 to 17 cm/sec. in the
deep sea, along the western margin of the west-
ern trough, in depths between 3,000 and 5,000
meters. The calculated currents on the eastern
side of the deep South Atlantic, especially in
the region of the Angola Basin were, on the
contrary, very weak. Dietrich (1957) has like-
wise computed mean current velocities of about
10 cm/sec. for the deep Antarctic Circumpolar
Current, and for the Subarctic Bottom Current
in the northern North Atlantic, the latter in-
creasing to as much as 40 cm/sec. when flow-
ing across the Greenland-Scotland ridge. He
states, however, that in the largest part of the
ocean the bottom currents are below 2 cm/sec.
Direct measurements of deep currents are
technically difficult. The few successful meas-
urements summarized by Bowden (1954) show
mean velocities from less than a cm/sec. to 13
cm/sec. Recently Swallow (1955 and unpub-
lished data) has measured subsurface currents
by tracking a neutrally buoyant float at a fixed
depth. His measurements in the North At-
lantic give mean resultant velocities of 1.7 to
9.1 cm/sec. Tidal currents of about 10 cm/sec.
have been obtained by Swallow and others in
deep water. It appears that the mean current in
many parts of the deep sea may be less than
the periodic variable currents.
The turbulence of these variable tidal cur-
rents, especially near the bottom, contributes to
vertical and horizontal mixing in deep water.
Mixing should also occur along the boundaries
of the rapid deep resultant currents indicated by
Wiist and Dietrich, where there must be con-
siderable shear.
Dietrich (1957) also suggests that horizontal
spreading of near-bottom water may occur in
regions of turbidity currents, which occur es-
pecially on the continental slopes.
Exchange between the open sea and coastal areas
In coastal areas and estuaries where precipita-
tion and land runoff exceed evaporation, there
is a net seaward drift of dilute surface water
and an inshore drift of sub-surface water from
the open sea. This is superimposed on the flow
of wind-driven currents through the coastal
areas.
Some idea of the average time involved in
interchange of coastal waters can be obtained
from the volume in and transport through vari-
ous areas along the American Atlantic seacoast.
Calculations give a mean age of 2^ years for the
waters over the Continental Shelf from Cape
Hatteras to Cape Cod, about 3 months for the
Bay of Fundy, and 3 to 4 months for Delaware
Bay (Wooster and Ketchum, Chapter 4) .
Exchange between the deep and intermediate
layers and the mixed subsurface layer
Evidence of local cross pycnocline interchange
was obtained from measurements of the vertical
distribution of radioactivity following the 1954
Pacific weapons tests (Japanese Fishery Agency,
1955 and Harley, 1956) ; it is not, however,
clear whether the observed phenomena were en-
tirely the result of physical exchange of the wa-
ter and its contents or were in part due to
settling of particles and to biological transport.
The major exchange between the near-surface
and deeper waters takes place in the following
regions :
In areas where the pycnocline is maintained,
by the distribution of mass related to the gen-
eral circulation, at a sufficiently shallow depth to
be eroded away by wind stirring. Such areas
exist near the equator, along the north edge of
the Equatorial Counter Current, and at the
centers of strong cyclonic eddies.
In regions of upwelling, where vertical cur-
rents carry water toward the surface and stir
the surface and intermediate layers. Water
from as deep as about 500 meters may be
General Considerations
15
brought to the surface by this process. Upwell-
ing occurs along the western coasts of continents
in intermediate and low latitudes, wherever the
wind-driven circulation removes surface water
from the coast. This water is replaced by deeper
water moving upward. Such coastal upwelling
has been found to be of the order of 1 to 3
meters per day. Upwelling also occurs in mid-
ocean where there are surface current diver-
gences, most notably along the equator in the
eastern and central Pacific.
In regions of surface convergence, where
sinking waters may extend to the oceanic depths,
or may spread out at intermediate levels, ac-
cording to their density. In tropical and tem-
perate latitudes such sinking is confined to the
upper few hundred meters, but at high latitudes
the waters may reach great depths. Indeed, it is
in the convergence regions of high latitudes
that much of the intermediate and deep water
of the oceans are formed.
In regions where increase of surface density
by evaporation, freezing out of ice, or cooling,
causes the surface waters to sink and be replaced
by the formerly deeper water. Deep thermal
convection occurs in high latitudes and extends
in some areas to the bottom ; for example, Ant-
arctic bottom water is formed in the Weddell
Sea by the cooling and sinking of the surface
waters, and the Atlantic deep water is formed
in a similar manner east of Greenland. Haline
convection takes place in regions where evapora-
tion exceeds precipitation or where freezing
prevails over melting. The latter in high lati-
tudes increases the intensity of the thermal
convection. Haline convection in winter is re-
sponsible for the characteristics of the deep
water of the Mediterranean Sea. This water
flows out into the North Atlantic at depths of
1,000 to 1,500 meters, and can easily be identi-
fied even on the western side of the ocean.
The exchange between the surface layer of
the ocean and the deeper layers may be either
continuous or discontinuous. Some idea of the
rate of exchange can be obtained from various
estimates of the "age" or average residence time
of the water in the deeper layers. These es-
timates, which differ widely depending on the
data and assumptions used, have been sum-
marized by Wooster and Ketchum (Chapter 4
of this report) and by Craig (Chapter 3) .
Three estimates for the water in the inter-
mediate layer of the Atlantic Ocean give resi-
dence times between 7 and 140 years. Estimates
for the water below 2,000 meters vary from 50
to 1,000 years. An estimated upper limit based
on the measured heat flow through the sea floor
under the Pacific Ocean indicates that the Pacific
deep water is replenished in less than 1,000
years. The deep water in the Pacific may be
older than in the Atlantic because of the larger
volume of the Pacific.
EXCHANGE FROM CONFINED BASINS
The few data available for estimating the age
of water in confined basins have been considered
by Wooster and Ketchum (Chapter 4). These
indicate that the mean residence time of water
in the Mediterranean Sea is about 75 years. In
the Caribbean Sea the mean age cannot be less
than 6 years and, in the deeper part, may be
as much as 140 years. The deep waters of the
Black Sea apparently remain isolated for very
long periods. Transport considerations lead to
an estimated age of at least 2,500 years, while,
from consideration of phosphorus accumulation,
the age has been estimated at 5,600 years.
VI. Biological Processes and Radioactive
Materials
Uptake and accumulation of elements in organ-
isms
Organisms take up from their environment
and their food and incorporate into their bodies
those elements required for their maintenance,
growth, and reproduction. The proportion of
various elements required by the organisms are
different than the proportions in the environ-
ment, and this results in concentrations of some
elements in the biosphere.
The energy that drives the whole life cycle
is the energy of sunlight. This energy is bound
chemically in organic compounds by the photo-
synthesis of plants, and is passed along, through
the food chain, in the food of all the organisms
beyond the plants. The flux of energy, and
hence the flux of carbon, through the various
trophic levels measures the productivity of the
organisms at each level. Since the efficiency at
each stage of the chain is low (of the order of
10 per cent to 30 per cent) the flux decreases
at each step. The standing crop, or biomass,
of organisms at the different levels, or, in other
words, the amount of carbon present in the or-
ganisms at each level, may be greater or less
16
Atomic Radiation and Oceanography and Fisheries
than the amount at the next lower level, de-
pending on the rates of turnover of the popula-
tions involved.
In addition to the abundant elements carbon,
oxygen and hydrogen, the bodies of organisms
contain a number of elements in smaller
amounts, such as nitrogen, phosphorus, calcium,
strontium, copper, zinc, and iron, which are
essential to the life processes. These may be ob-
tained by organisms above the plants in the
food chain either from their ingested food, or
by direct uptake from the sea water. Since the
requirements for different elements are different
in different kinds of organisms, the fluxes of the
of the populations of a particular part of the
sea, and any quantities added will be soaked up
by the biosphere very rapidly.
Both dissolved and particulate materials can
be taken up from the environment. Iron, for
example, occurs in the sea almost entirely in
particulate form and is used in that form by
diatoms. Fishes can take up ionic calcium and
strontium directly from the sea water. Observa-
tions in conjunction with weapons tests, re-
ported in Chapter 7 of this report, have shown
that particulate feeders among the zooplankton
ingest particles of inorganic compounds and
retain them.
TABLE 6 Approximate Concentration Factors of Different Elements in Members of the Marine
Biosphere. The Concentration Factors Are Based on a Lfve Weight Basis
(From Krumholz, Goldberg and Boroughs, Ch. 7 of This Report)
Concentration factors
Concentration
Form in in sea water
Element sea water (micrograms/1)
Na Ionic 10'
K Ionic 380,000
Cs Ionic 0.5
Ca Ionic 400,000
Sr Ionic 7,000
Zn Ionic 10
Cu Ionic 3
Fe Particulate 10
Ni * Ionic 2
Mo lonic-Particulate 10
V ? 2
Ti ? 1
Cr ? 0.05
P Ionic 70
S Ionic 900,000
I 50
* Values from Laevastu and Thompson (1956).
various elements are variable from one to an-
other, and at different trophic levels.
The concentration factors of some of the im-
portant elements in different kinds of organ-
isms are tabulated in Table 6, taken from Krum-
holz, Goldberg and Boroughs (Chapter 7 of
this report). Certain elements, for example,
sodium, occur in some organisms at lower con-
centrations than in the water; they are selected
against. On the contrary, those elements, such
as phosphorus, that are essential to the organ-
isms but occur in low concentration in the sea
water, are concentrated by several orders of
magnitude. In some parts of the sea, the phos-
phorus may be nearly completely removed from
the water by the organisms. Such elements are
often limiting constituents for further increase
Algae
Invertebrates
Vertebrates
(non-cal-
careous)
Soft
Skeletal
Soft
Skeletal
1
0.5
0
0.07
1
25
10
0
5
20
1
10
10
10
10
1,000
1
200
20
10
1,000
1
50
100
5,000
1,000
1,000
30,000
100
5,000
5,000
1,000
1,000
20,000
10,000
100,000
1,000
5,000
500
200
200
100
0
10
100
20
1,000
100
20
1,000
1,000
40
300
10,000
10,000
10,000
40,000
2,000,000
10
5
1
2
10,000
100
50
10
The uptakes of various elements by organ-
isms are not entirely independent of one an-
other. Elements of similar chemical properties
tend to be taken up together very roughly in the
same proportions as they exist in the environ-
ment. This is true, for example, of calcium and
strontium. Sometimes one element has an in-
hibiting effect on another. There can also be
synergistic effects, such as the enhancement of
phosphorus uptake of diatoms by increased
concentration of nitrogen.
Certain elements are deposited, in large part,
in particular organs. Perhaps the best known
examples are the deposition of iodine in the
thyroid glands of vertebrates, or the deposition
of calcium and strontium in the bones of verte-
General Considerations
17
brates and in the shells and other hard parts of
invertebrates.
The length of time an organism retains the
average atom of a given element varies greatly
from one element to another. This is some-
times measured as the biological half-life, al-
though the relative rate of loss is not a simple
linear function of time as is the case with radio-
active decay. Much is known about the reten-
tion times of different elements in man (see,
for example. Handbook 52 of the National
Bureau of Standards, 1953), but there are few
data for most marine organisms. The rate of
excretion of an element and the amount ulti-
mately retained, will be quite different if the
element is taken up quickly from a single dose
or is taken up slowly over a long time.
The processes of uptake, accumulation, and
loss of elements by marine and other aquatic
organisms, are discussed in more detail by
Boroughs, Chipman and Rice (Chapter 8 of this
report), Krumholz, Goldberg, and Boroughs
(Chapter 7), and by Krumholz and Foster
(Chapter 9).
Effects of organisms on spatial distributions of
elements in the sea
Those elements of which a large proportion
is cycled through organisms are modified pro-
foundly in their spatial distributions by the ef-
fects of the biosphere, so that they are quite
differently distributed in the sea than elements
in which the distribution is determined only by
physical and inorganic chemical processes. We
have already mentioned phosphorus as a notable
example. Ketchum (Chapter 5 of this report)
has written a detailed discussion of the general
effects of the ecological system on the distribu-
ticfti of elements in the sea.
The marine biosphere acts as a reservoir for
those elements that are removed selectively
from sea water by organisms. This reservoir is
not stationary in space, however, because many
of the living organisms make both vertical and
horizontal migrations of large extent, while
their dead bodies and fecal materials continu-
ally fall toward the bottom under the influence
of gravitation. The effects of the living reser-
voir in the distribution of elements vary not
only from one part of the sea to another, but
also seasonally in the same area.
Because organisms in the sea are more abun-
dant in the upper layers than deeper down,
those elements in scarce supply that are essen-
tial to life tend to be retained by the biosphere
in the upper layers and to be returned to solu-
tion in the deeper layers. Stationary popula-
tions, such as attached benthic organisms, act
as a fixed reservoir.
Where there are currents at different levels
in opposite directions, the accumulation of ele-
ments by pelagic organisms, together with grav-
ity effects on their dead bodies and fecal ma-
terials, can result in local concentrations of ele-
ments at intermediate depths greater than the
concentrations in either the overlying or the
deeper waters. This pattern, as noted by
Ketchum, is common in estuaries, continental
shelves, and in the vicinity of coastal upwelling.
Migration of organisms may result in a net
transport of elements from areas of high con-
centration to areas of lower concentration. Thus,
for example, the vertical migrations of the or-
ganisms of the deep scattering layer can result
in a transport from the deeper layers into the
upper mixed layer. Salmon which spawn and
die in fresh waters after accumulating elements
in the sea can transport significant quantities of
some elements from the sea to fresh waters.
Finally, the remains of organisms, falling out
as particulate matter, are an important com-
ponent of the sedimentation process in the deep
sea, and are thus important in the geochemical
cycle, as noted by Carritt and Harley (Chapter
6) and others.
Although we have some understanding of
the various processes involved, data for making
useful quantitative assessments are almost en-
tirely lacking.
Effects of introduction of radioactive elements
Since the isotopes of most chemical elements
are similar in chemical behavior, it can be as-
sumed that organisms do not appreciably dis-
tinguish between the radioactive and non-radio-
active isotopes, and that, to a good degree of
approximation, the path of a radioactive element
through the biological system is the same as
that of its non-radioactive isotopes.
The accumulation of radio isotopes in organ-
isms will, therefore, depend on the same factors
as the accumulation of normal isotopes (their
concentration in the water where the organisms
are located, the concentrations of other elements
by which uptake is influenced, the size of the
population of organisms concerned, the concen-
18
At0777'ic Radiation a?7d Oceanography and Fisheries
tration factors of the organisms for each ele-
ment, and the rates of excretion, and in addition
will depend on the decay rates of the radioactive
isotopes) .
The most important radio isotopes from the
standpoint of accumulation in organisms are,
therefore, those which are concentrated in large
degree by organisms, are retained by them for
relatively long periods of time, and have slow
decay rates. An additional consideration from
the standpoint of human hazards is the uptake
and biological half-life of the elements in hu-
mans who may consume the marine organisms
as food.
The most important fission product from all
these considerations is strontium 90 and its
daughter yttrium 90. This isotope has a large
fission yield and a long physical half-life, is
concentrated by organisms, and can be tolerated
in human food only in very low amounts.
Ce 144 is another isotope with a large fission
yield, which is concentrated by organisms (Har-
ley, 1956), and has a moderately slow decay
rate. Due to its small uptake and low retention
by humans, it can, however, be tolerated in
human food in much greater concentrations than
Sr90.
Zn 65 and Co 60, although not fission prod-
ucts, are sometimes produced in relatively large
quantities in weapons tests. They are concen-
trated by very large factors in fish and mollusks
used for human food, but fortunately they
possess a relatively high tolerance level in
humans.
Because of its biological role both in marine
organisms and in humans, strontium 90 dom-
inates consideration of depositing mixed fission
products in the sea. For other radioactive
wastes, and for mixed fission products from
which Sr 90 has been removed, other elements
will be the critical determinants, but in most
cases, prior removal of Sr 90 will permit the
safe disposal in the sea of larger quantities than
would otherwise be possible.
The safe quantity of fission products depends
on the concentrations that reach man's food or-
ganisms. The quantity will be greater if sites
of introduction are chosen to give either long
periods of isolation of the wastes or high dis-
persion (and thus low concentration) of the
fractions that come into the environment (both
physical and biological) of human food organ-
isms.
Somatic and genetic effects on marine organisms
It is sometimes suggested that sufficient quan-
tities of radioactive elements may be accumu-
lated by marine organisms to endanger their
populations, either by direct somatic effects or
through genetic changes. Some aspects of this
problem are discussed by Donaldson and Foster
in Chapter 10 of this report.
So far as somatic eflFects are concerned, ex-
perimental data indicate that primitive forms
are more resistant to ionizing radiation than the
more complex vertebrates. It has not been possi-
ble to demonstrate any large-scale radiation
damage to marine populations in the vicinity of
large weapons tests. Levels of radiation safe
from the standpoint of human hazards are also
probably safe for the populations of marine
organisms that are used as human food.
By analogy with results from genetic studies
on laboratory animals, it may be inferred that
significant genetic population effects will occur
in marine organisms at much lower levels of
radiation than will produce somatic effects.
These genetic effects might be related to the in-
crease in amount of total body radiation above
the natural background. As shown by Folsom
and Harley (Chapter 2), the normal radiation
background of organisms in the deep sea is very
low, so that appreciable quantities of radioactive
wastes would significantly increase the radiation
received by them. Craig (Chapter 3) has shown
that the deposition of 1,000 tons per year of
fission products in the deep sea would, at secular
equilibrium, almost triple the average radiation
level in the deep water. This could, conceivably,
result in genetic effects in the marine popula-
tions in these waters, which might seriously up-
set the ecological system of the oceans. At the
present state of knowledge, however, this is
pure speculation. The matter does require,
nevertheless, serious investigation.
VII. Predicted Effects of Introduced
Radioactive Materials
Prediction of the effects of the introduction
of radioactive materials into the different do-
mains of the oceans must take into account the
various physical, chemical, and biological proc-
esses discussed above. While our knowledge of
these processes is very imperfect, we can make
rough evaluations of the effects of disposal of
fission products in different parts of the sea.
Because of the limitation of knowledge, these
General Considerations
19
evaluations must, of necessity, be conservative.
Under some circumstances this necessity could
involve considerable cost to society. Those sites
and methods of disposal, both on the land and
in the sea, that provide the least hazard may
also involve the greatest disposal costs, so that,
to the extent we must include a safety factor be-
cause of ignorance, there can be economic loss.
In disposing of radioactive materials in the
sea, we aim at two things: (1) isolation of the
materials, so that their entry into the part of the
sea and its contents used by man is limited, (2)
dispersal of the materials that do enter the
domain important to man, to keep the concen-
trations of radioactive elements at tolerable
levels. Depending on the quantity of materials
to be dealt with, we may need to consider either
or both of these possibilities.
Introduction in the upper mixed layer
Radioactive materials introduced into the up-
per mixed layer will, because of the rapid
transport and large horizontal and vertical mix-
ing within this layer, be carried away from the
site of introduction and rapidly dispersed. Dis-
persion may be more rapid in coastal areas than
in the open sea, but in some situations there may
be a net transport inshore, particularly in or
near estuaries, if the materials are introduced
below the surface.
Direct evidence of near-surface transport and
dispersion of fission products in the open sea has
been obtained by the surveys of the "Shunkotsu
Maru" (Miyake, Sugiura and Kameda, 1955)
and the "Taney" (Harley, 1956), respectively
four and thirteen months after the Pacific weap-
ons tests of March 1954. The indicated trans-
port of these products was in good agreement
with current velocities measured by conven-
tional means. These data from the open sea and
earlier measurements on the partially confined
waters of Bikini Lagoon (Munk, Ewing and
Revelle, 1949) demonstrate the rapid dispersal
of fission products in the surface layer.
Dispersion in an inshore situation (the Irish
Sea) was measured with fluorescein by Selig-
man (1955) as a preparatory study for the dis-
charge of low-level wastes from a power reactor
installation. Subsequent experience with libera-
tion of the radioactive wastes (Anon., 1956)
confirmed that they were rapidly dispersed.
Radioactive materials introduced into coastal
waters enter directly into that part of the ocean
most utilized by man, from which he removes
the greater share of his harvest of marine food
organisms. The sessile algae, bottom living in-
vertebrates, and fishes of these waters heavily
concentrate certain of the elements, such as
strontium, cesium, zinc, and cobalt that has
radioactive isotopes most hazardous to man.
While dispersion due to physical transport and
dispersion in these waters is high, they are
usually shallow, so that the volume is limited
and there can also be considerable accumula-
tion in shallow bottom sediments from which
the isotopes can be again taken up by man's
food organisms.
In some coastal areas the combination of
physical and biological processes can result in
local concentrations of radioactivity in the wa-
ters themselves (Ketchum, Chapter 5 ) .
Because of the above considerations, the
quantity of radioactive materials that can be in-
troduced safely into coastal waters near shore
is very limited, of the order of a few hundred
curies per day. The particular physical, chemi-
cal, and biological factors vary so widely from
one coastal area to another, that careful study
is required to determine the safe amount in any
particular locality, and continuous monitoring
should be conducted to guard against efi^ects of
unforeseen variability in environmental factors.
The rather low level of discharge of radioac-
tive products that can be tolerated in coastal
waters imposes the necessity of providing ade-
quate safeguards against discharge of high-level
atomic wastes from accidents to power reactors,
either at locations on the shore or shipborne
reactors.
The quantity of radioactive material that can
be safely deposited in the mixed layer in the
open sea depends on such local characteristics
as the direction and rate of transport, the rate
of horizontal dispersion, the rate of uptake by
organisms, and the contiguity of fishing areas.
However, in general, the quantities will be
much greater than those permissible for coastal
waters. An idea of the order of magnitude of
mixed fission products that can be safely intro-
duced in a fairly typical situation is given by the
results of weapons tests in the Pacific where a
quantity of mixed fission products of the order
of half a ton was introduced into the mixed
layer in a short time period. That this was near
the limit of safety is evidenced by the capture in
adjacent areas of specimens of tunas and other
fishes with sufficient radioactivity to be doubt-
20
Atomic Radiation and Oceanography and Fisheries
ful for human consumption (Kawabata, 1956,
and Hiyama and Ichikawa, 1956).
Deep water introduction
The only place in the ocean in which we can
be confident at this time that radioactive wastes
of the order of some tons a year can be safely
deposited is in the depths of the sea. Knowl-
edge is, however, insufficient to determine
whether radioactive materials of the order of
the expected production from power reactors in
the next few decades could be disposed of in
this way.
Radioactive materials introduced into the
deeper layers will be partially isolated from the
upper layer for time periods related to the resi-
dence time of the water in the deeper layer.
During this time there will be a decrease of
radioactivity due to decay, and dilution due
to dispersion. Since, as we have noted above,
the residence times are variable in different
depths and different locations, a much greater
time of isolation will be obtained in some places
than others.
The longest average time of isolation will be
obtained in deep nearly enclosed basins such as
the Black Sea. It has been suggested by Wiist
(1957) that there may also be a long isolation
period in the abyssal trenches of the central
equatorial regions, such as the Romansch Deep
or the Tonga Trench, but no data on currents in
these deeps are now available.
Craig (Chapter 3 of this report), assuming
an estimated average residence time in the deep
sea of 300 years, the introduction into the deep
sea of 1,000 tons per year of fission products
after 100 days cooling, and complete uniform
mixing within the deep water, has calculated the
activity in the deep and surface layers at secular
equilibrium. This calculation indicates that the
total fission product activity in the mxed layer
would be about equal to that at present from
natural sources (primarily K*°) . The concentra-
tion of Sr 90 would, however, be about 6.5 x
10"^ microcuries per liter, or 0.16 microcuries
per kilogram of calcium in solution in sea water.
Studies of the uptake of strontium by marine
fishes indicate a discrimination against strontium
with respect to calcium approximately by a fac-
tor between 3 and 10. Thus for human popula-
tions such as the Japanese (Hiyama, 1956), in
which much of the dietary calcium is obtained
from marine fishes (including the bones and
skin of some species), the amount of strontium
90 ingested per unit weight of calcium would
be of the order of .04 microcuries per kilogram
of calcium. A human population that obtained
all its calcium from marine fishes after equilib-
rium was established with about 1,000 tons of
fission products per year (1.1 x 10^ megacuries
of strontium 90) in the deep sea would have a
burden, primarily in the bones, of approxi-
mately .005 microcuries of strontium 90 per
kilogram of calcium. This is 5 per cent of the
maximum permissible concentration for the
population at large, estimated by the National
Bureau of Standards (1955).
Weapons tests resulted in an average amount
of .025 microcuries of strontium 90 per kilo-
gram of calcium available to growing plants in
the United States in 1955. By 1970, the amount
will be .08 microcuries per kilogram of calcium
even in the absence of further weapons tests
(Kulp, Eckelmann, and Schulert, 1957). Be-
cause of discrimination against strontium with
respect to calcium in food grains and grasses,
and the additional discrimination in cows' milk
and in human beings, it is expected that by
1970 an average of about .002 microcuries of
strontium 90 per kilogram of calcium will
exist in the United States population, 2 per cent
of the maximum permissible concentration.
From the above considerations it is uncertain
whether reactor-fuel wastes of the order of
1,000 tons a year could be deposited safely in
the deep sea. Craig's calculation is most useful
in orienting our thinking, but is, of course,
very much oversimplified. No account is taken
of the removal of activity from the sea by sedi-
mentation. On the other hand, it does not take
into account any biological transfer of material
across the pycnocline, nor can we assume that
effective concentration of Sr 90 per unit weight
of calcium for some commercially important or-
ganisms will not be greater than the values we
have taken.
Moreover, such a calculation assumes even
distribution of the radioactive materials through-
out the deep layer. This could only occur if they
were evenly distributed when introduced, or if
there were uniform and complete mixing in all
parts of the deep layer.
A priori we should expect that neither the
physical circulation and mixing in the deep sea
nor the transfer between the deep layer and
the mixed layer would be uniform. There is
General Considerations
21
some evidence, however, from carbon 14 meas-
urements made by the Lamont Geological Ob-
servatory that in fact fairly complete mixing
occurs within the deep sea during the average
residence time of a water particle.
Another calculation, based on very conserva-
tive assumptions concerning the mixing proc-
esses, was made in the report of a meeting of
scientists from the U.S. and U.K. (Anon.,
1956). It was assumed that fission products
deposited on the ocean floor in mid-latitudes
would drift and disperse for at least 10 years
before surfacing, at which time the contami-
nated area would be a disc about 2 km. thick
and 70 km. in diameter, which would be sub-
sequently dispersed throughout the surface layer.
Repeated deposits of 1 megacurie of Sr 90 (0.4
tons of mixed fission products) made at the rate
of ten per year would result in an average con-
centration of Sr 90 of not over 10'^ microcuries
per liter in the mixed layer, or .025 microcuries
per kilogram of calcium.
Although we cannot say at this time with any
precision what quantities of reactor-waste prod-
ucts can be safely deposited in the deep sea, it
appears certainly safe to employ quantities up to
a few tons a year in careful experimental studies.
It is not impossible that 1,000 tons a year can
be safely disposed of in deep, isolated basins
where the residence time is much greater than
the 300-year average estimated for the deep sea
generally. For quantities of the order of 100
tons a year or more, effects on the animal popu-
lations of the deep sea, and resulting effects on
the whole ecology of the sea could become im-
portant; as to this no information is at present
available.
VIII. What We Need to Know
Our knowledge of most of the processes in
the oceans is altogether too fragmentary to per-
mit precise predictions of the results of the in-
troduction of a given quantity of radioactive
materials at any particular place. In order to
obtain the necessary knowledge, an adequate,
long-range program of research on the physics,
chemistry, and geology of the sea, and on the
biology and ecology of its contained organisms
is required. Such research must be directed
toward the understanding of general principles,
not simply to the ad hoc solution of a particu-
lar local problem for immediate application.
The latter sort of study is, of course, desirable
in order to provide engineering solutions to par-
ticular waste-disposal problems as they arise.
Such engineering solutions must necessarily be
of limited application and, moreover, they must
always be conservative, at least until sufficient
broad understanding is obtained.
MAJOR UNSOLVED PROBLEMS
Some of the major basic problems that should
be included in the research program can be
briefly outlined:
1 . Dispersion in the upper mixed layer
Fairly extensive information is available on
the mean velocities and transport of the major
surface currents. The transient currents and
eddies that result in dispersion in both the hori-
zontal and vertical directions are, on the con-
trary, not understood. Some empirical param-
eters approximately describing the relationships
of diffusivity to time and to size of area have
been developed, but understanding of the de-
tailed physical principles is lacking. In con-
sequence, it is not possible to predict on the
basis of more elementary properties the disper-
sion of materials introduced into the upper layer
at a given point. Direct measurements must be
made, and these are costly and not necessarily
reliable. Basic research on the turbulent motion
of water in the upper layer is needed.
2. Circulation in the intermediate and deep
layers
For the region of the sea below the surface
layer, we not only do not understand the nature
of the turbulent motion, we do not even have
a description of the mean currents. The chart-
ing of the deep currents, and investigations
toward elucidating the physical principles in-
volved should be vigorously pursued.
3. Exchange between the surface layer and
deeper layers
It is important to determine the average rate
of exchange of water between the surface and
the deep layers, as a basis of estimating average
"hold up" times of dissolved materials deposited
in the deep layer. It is probably even more im-
portant to measure the heterogeneity in the ex-
change system, that is to measure the rates of
exchange in different areas and depths. We
22
Atomic Radiation and Oceanography and Fisheries
know that vertical exchange is much more rapid
in some parts of the oceans than others, but de-
scribing it in quantitative terms can be done
only in a very sketchy manner. Quantitative
data on this subject are required as one basis
of arriving at estimates of the amount of atomic
wastes that can be deposited safely in specified
parts of the deep sea.
4. Sedimentation processes
Sedimentation processes constitute an im-
portant mechanism for removing atomic wastes
from the waters of the oceans. In order to evalu-
ate their role, however, we need to measure the
average times that different elements remain in
the sea before being deposited in the sediments,
the rates of sedimentation in different parts of
the deep sea, and the ability of the sediments to
capture and retain various fission products.
3. Effects of the biosphere on the distribution
and circulation of elements
As we have noted, marine organisms have
profound effects in modifying the distribution
and circulation of elements in the sea. It is
vitally necessary that the biological processes be
studied in sufficient detail to enable their effects
to be quantitatively evaluated. Such investiga-
tions need to include: The flux of various ele-
ments through the different trophic levels, and
the variations in different ecological realms such
as inshore coastal waters, offshore surface waters
and the deep sea; the effects of vertical and
horizontal migrations of organisms on redis-
tribution of elements ; the effects of the uptake,
modification of the physical state, and elimina-
tion of elements by members of the marine
biosphere on their subsequent distribution in
the sea.
6. Uptake and retention of elements by organ-
isms used as food for man
Related to the foregoing, but of separate im-
portance, is the study of the quantities of radio-
active elements deposited in different situations
in the sea that can be expected to be taken up
by organisms harvested for food, the length of
time such elements are retained in the food or-
ganisms, and, consequently, the levels of con-
centration. Some parts of some organisms are
not eaten by man, but are discarded or used for
other purposes. The sites of accumulation of
different radioactive elements in the organisms
must therefore be determined.
7, Ejects of atomic radiation on populations of
marine organisms
In order to determine what quantities of
atomic wastes can be safely deposited in the sea
without upsetting the ecology of the sea through
destruction of important populations of organ-
isms, research is needed on the somatic and ge-
netic effects of atomic radiation on marine popu-
lations. This is especially important for organ-
isms of the deep sea which may come in contact
with very high concentrations of radioactive
elements, if deep sea disposal of large quantities
proves feasible in other respects.
RESEARCH METHODS
Much of this required research can be ac-
complished by the intensive application of
classical techniques of physics, chemistry, ge-
ology, and biology. In addition, however, the
availability of radioactive isotopes provides us
with a powerful new tool, which is especially
valuable for studying processes. The use of
radioactive elements as tracers permits the paths
of various elements, both in the physical en-
vironment and within the biosphere, to be de-
termined, and the fluxes of the elements through
various parts of the system to be measured.
Radioactive tracers are useful both in labo-
ratory experiments and in field studies of vari-
ous kinds. The use of tracers in the laboratory
and in small scale field experiments is already
familiar. Information from the tracers intro-
duced into the sea by weapons tests has provided
valuable information. What has not yet been
done, and what we believe will be a fruitful
approach, is the employment of fairly large
quantities of radio isotopes to study the various
processes in the open ocean in a planned fash-
ion. In Chapters of this report by Folsom and
Vine and by Schaefer, suggestions are made for
some experiments that should be useful and are
currently feasible.
Naturally occurring radioactive isotopes can
also provide a fruitful means of attack. Craig,
in Chapter 11, discusses some of these avenues
of research in detail.
FACILITIES REQUIRED
The Committee has not attempted to draw
up detailed estimates of men, ships, and facili-
General Considerations
23
ties which will be required for an adequate
attack on this problem. These requirements
will, however, be large. The problems outlined
above are among the most difficult in the marine
sciences. Adequate solutions will demand the
collection of much more knowledge about the
sea and its contents than the total obtained in
the past hundred years.
Because of the urgency of these problems,
and because of the large costs involved, it is
essential that research be coordinated on both
the national and international levels. Coordina-
tion among scientists engaged in these studies
should be easier in the future than it has been
in the past.
OTHER BENEFITS OF THE RESEARCH TO
MANKIND
The potential requirement for disposal of
atomic wastes in the sea is sufficient reason for
pursuit of these investigations. However, man-
kind will derive additional, and perhaps even
greater, benefits in other ways. For example,
the flux of materials through the various trophic
levels of the biosphere is the fundamental proc-
ess underlying the harvest of the sea fisheries.
This process must be studied to provide part of
the basis for atomic waste disposal, but its
elucidation will also provide much of the scien-
tific base for the optimum exploitation and con-
servation of the seas* living resources by man.
IX. Conclusions and Recommendations
We repeat here the conclusions and recom-
mendations that were agreed upon by the mem-
bers of the Committee at the time they prepared
the Summary Report published by the Academy
in 1956:
1. Tests of atomic weapons can be carried
out over or in the sea in selected localities with-
out serious loss to fisheries if the planning and
execution of the tests are based on adequate
knowledge of the biological regime. The same
thing is true of experimental introduction of
fission products into the sea for scientific and
engineering purposes.
2. Within the foreseeable future the prob-
lem of disposal of atomic wastes from nuclear
fission power plants will greatly overshadow the
present problems posed by the dispersal of ra-
dioactive materials from weapons tests. It may
be convenient and perhaps necessary to dispose
of some of these industrial wastes in the oceans.
Sufficient knowledge is not now available to
predict the effects of such disposal on man's
use of other resources of the sea.
3. We are confident that the necessary knowl-
edge can be obtained through an adequate and
long-range program of research on the physics,
chemistry, and geology of the sea and on the
biology of marine organisms. Such a program
would involve both field and laboratory experi-
ments with radioactive material as well as the
use of other techniques for oceanographic re-
search. Although some research is already un-
der way, the level of effort is too low. Far more
important, much of the present research is too
short-range in character, directed towards ad hoc
solutions of immediate engineering problems,
and as a result produces limited knowledge
rather than the broad understanding upon
which lasting solutions can be based.
4. We recommend that in future weapons
tests there should be a serious effort to obtain
the maximum of purely scientific information
about the ocean, the atmosphere, and marine
organisms. This requires, in our opinion, the
following steps: (1) In the planning stage com-
mittees of disinterested scientists should be
consulted and their recommendations followed;
(2) funds should be made available for scien-
tific studies unrelated to the character of the
weapons themselves; (3) the recommended
scientific program should be supported and car-
ried out independently of the military program
rather than on a "not to interfere" basis.
5. Ignorance and emotionalism characterize
much of the discussion of the effects of large
amounts of radioactivity on the oceans and the
fisheries. Our present knowledge should be suf-
ficient to dispel much of the overconfidence on
the one hand and the fear on the other that
have characterized discussion both within the
Government and among the general public. In
our opinion, benefits would result from a con-
siderable relaxation of secrecy in a serious
attempt to spread knowledge and understanding
throughout the population.
6. Sea disposal of radioactive waste materials,
if carried out in a limited, experimental, con-
trolled fashion, can provide some of the in-
formation required to evaluate the possibilities
of, and limitations on, this method of disposal.
Very careful regulation and evaluation of such
operations will, however, be required. We,
therefore, recommend that a national agency,
24
Atomic Radiation and Oceanography and Fisheries
with adequate authority, financial support, and
technical staff, regulate and maintain records of
such disposal, and that continuing scientific and
engineering studies be made of the resulting
effects in the sea.
7. We recommend that a National Academy
of Sciences — National Research Council com-
mittee on atomic radiation in relation to ocean-
ography and fisheries be established on a con-
tinuing basis to collect and evaluate informa-
tion and to plan and coordinate scientific re-
search.*
8. Studies of the ocean and the atmosphere
are more costly in time than in money, and time
is already late to begin certain important studies.
The problems involved cannot be attacked
quickly or even, in many cases, directly. The
pollution problems of the past and present,
though serious, are not irremediable. The atomic
waste problem, if allowed to get out of hand,
might result in a profound, irrecoverable loss.
We, therefore, plead with all urgency for im-
mediate intensification and redirection of scien-
tific effort on a world-wide basis towards build-
ing the structure of understanding that will be
necessary in the future. This structure cannot
be completed in a few years; decades of effort
will be necessary and mankind will be fortunate
if the required knowledge is available at the
time when the practical engineering problems
have to be faced.
9. The world-girdling oceans cannot be sepa-
rated into isolated parts. What happens at any
one point in the sea ultimately affects the waters
everywhere. Moreover, the oceans are interna-
tional. No man and no nation can claim the
exclusive ownership of the resources of the sea.
The problem of the disposal of radioactive
wastes, with its potential ha2ard to human use
of marine resources, is thus an international one.
In certain countries with small land areas and
large populations, marine disposal of fission
products may be essential to the economic de-
velopment of atomic energy. We, therefore,
recommend: (1) that cognizant international
agencies formulate as soon as possible conven-
tions for the safe disposal of atomic wastes at
sea, based on existing scientific knowledge; (2)
that the nations be urged to collaborate in
studies of the oceans and their contained organ-
* The President of the Academy, Dr. Detlev W.
Bronk, has requested that the present committee
undertake to develop and carry forward this con-
tinuing program.
isms, with the objective of developing compara-
tively safe means of oceanic disposal of the very
large quantities of radioactive wastes that may
be expected in the future.**
10. Because of the increasing radioactive con-
tamination of the sea and the atmosphere, many
of the necessary experiments will not be possi-
ble after another ten or twenty years. The recom-
mended international scientific effort should be
developed on an urgent basis.
11. The broader problems concerned with
full utilization of the food and other resources
of the sea for the benefit of mankind also re-
quire intensive international collaboration in the
scientific use of radioactive material.
REFERENCES
Anon. 1956. Report of a meeting of United
Kingdom and United States scientists on
biological effects of radiation in oceanog-
raphy and fisheries. Nat. Acad. Sci. — Nat.
Research Council, Oct. 31, 1956, 8 pp.
(mimeographed) .
BowDEN, K. F. 1954. The direct measurement
of subsurface currents in the oceans. Deep
Sea Research, Vol. 2, pp. 33-47.
Culler, F. L. 1954. Notes on fission product
wastes from proposed power reactors.
ORNL Central File No. 55-4-25.
Dietrich, G. 1957. Selection of suitable ocean
disposal areas for radioactive waste. (A
preliminary report with 6 charts.) M.S.,
10 pp.
Food and Agriculture Organization of
UNESCO. 1957. Yearbook of fishery
statistics. FAO, Rome, Vol. 5 (1954-55).
Goldberg, E. and Arrhenius, G. O. S. 1957.
Chemistry of Pacific pelagic sediments. In
press.
Greendale, a. E., and N. E. Ballou. 1954.
Physical state of fission product elements
following their vaporization in distilled
water and sea water. USNRDL Document
436, pp. 1-28.
Harley, John E. (Editor). 1956. Operation
Troll. U.S., A.E.C., N.Y. Operations office
1956. 37 pp.
** As a first step in this direction an informal dis-
cussion was held by members of this committee with
scientists from the United Kingdom at North Fal-
mouth, Massachusetts, on September 27 and 28, 1956.
A brief summary of the meeting was published by the
National Academy of Sciences (Anon., 1956).
General Considerations
25
HiYAMA, Y. 1956. Maximum permissible con-
centration of Sr 90 in food and its environ-
ment. Records of Oceanographic Work
in Japan, Vol. 3, No. 1, March 1957, pp.
70-77.
HiYAMA, Y., and R. Ichikawa. 1956. Move-
ment of fishing grounds where contami-
nated tuna were caught. Japan Society for
the Promotion of Science; Research in the
Effects and Influences of the Nuclear Bomb
Test Explosions, pp. 1079.
Japanese Fishery Agency. 1955. Report on
the investigations of the effects of radiation
in the Bikini region. Res. Dept., Jap. Fish.
Agency, Tokyo, 191 pp.
Kawabata, T. 1956. Movement of fishing
grounds where contaminated tuna were
caught. Japan Society for the Promotion of
Science; Research in the Effects and In-
fluences of the Nuclear Bomb Test Explo-
sions, pp. 1085.
Krauskopf, K. B. 1956. Factors controlling
the concentration of thirteen rare metals
in sea water. Geochim. et Cosmochim.
Acta 9, pp. 1-32.
KuLP, J. L., Eckelmann, W. R., and A. R.
SCHULERT. 1957. Strontium 90 in man.
Science, Vol. 125, No. 3241, pp. 219-225.
Laevastu, T., and T. G. Thompson. 1956.
The determination and occurrence of nickel
in sea water, marine organisms, and sedi-
ments. ]our. dti Cons., Vol. 21, pp. 125-
143.
Lapp, Ralph E. 1956. Strontium limits in
peace and war. Bidl. Atomic Scientists,
Vol. 12, No. 8, pp. 287-289, 320.
LiBBY, W. F. 1956a. Radioactive fallout and
radioactive strontium. Science, Vol. 123,
pp. 657-660.
1956b. Radioactive strontium fallout. Proc.
Nat. Acad. Sci., Vol. 42, No. 6, pp. 365-
390.
MiYAKE, J., SuGiURA, Y., and K. Kameda.
1955. On the distribution of radioactivity
in the sea around Bikini Atoll in June
1954. Pap. Meteorol. Geophys., Tokyo,
Vol. 5, No. 3-4, pp. 253-262.
MuNK, W. H. 1950. On the wind-driven
ocean circulation. Jour. Meteorol., Vol. 7,
No. 2, pp. 79-93.
MuNK, W. H., EwiNG, G. C, and R. R. Re-
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Trans. Am. Geophys. Union, Vol. 30, No.
1, pp. 59-66.
National Bureau of Standards, 1953.
Maximum permissible amounts of radio
isotopes in the human body and maximum
permissible concentrations in air and water.
U.S. Dept. of Commerce, Nat. Bureau
Standards. Handbook 52, 45 pp.
1954. Radioactive waste disposal in the
ocean. Nat. Bureau of Standards. Hand-
book 58, 31 pp.
Nucleonics. 1956. Calder Hall, over-all de-
scription. Nucleonics, Vol. 14, No. 12,
pp. SlO-Sll.
1957. Roundup of key developments in
atomic energy. Nucleonics, Vol. 15, No. 6,
pp. 17-28.
Rankama, K., and T. C. Sahama. 1950. Geo-
chemistry. Univ. of Chicago Press, 1950.
Revelle, R. R. 1957. Statement by Professor
Roger Revelle before the joint Committee
on atomic energy, 28 May 1957. The Na-
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on Man ; Hearings before the Special Sub-
committee on Radiation of the Joint Com-
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the United States, 1957.
Revelle, R. R., Folsom, T. R., Goldberg,
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the Peaceful Uses of Atomic Energy.
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Seligman, N. 1955. The discharge of radio-
active waste products into the Irish Sea.
Part I: First experiment for the study of
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of Atomic Energy, United Kingdom paper
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Sverdrup, H. U., Johnson, M. W., and R. H.
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Swallow, J. C. 1955. A neutral -buoyancy
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Vinogradov, A. P. 1953. The elementary
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Foundation for Marine Research, Memoir
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WiJST, G. 1957. Report on the current veloci-
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Chapter 1
PHYSICAL AND CHEMICAL PROPERTIES OF WASTES PRODUCED BY
ATOMIC POWER INDUSTRY
Charles E. Renn, The Johns Hopkins University
Department of Sanitary Engineering and Water Resources
The ultimate forms and radioactivities of
wastes delivered for sea disposal will be deter-
mined by conditions that have not yet been
fully evaluated. Present and projected wastes
will undoubtedly be modified by requirements
for storage, transport, and economical handling,
and the ultimate form of wastes with which we
may be concerned will be further conditioned
by what we learn in early disposal practice. The
following represents the characteristics of high-
level reactor wastes that now exist, and which
are likely to appear soon.
The primary radioactive wastes result from
the chemical extraction of inhibitory fission
products from metallic reactor elements. A
strong nitric acid solution of aluminum heavily
contaminated with a variety of fission products
is obtained after the useful reactor fuel is re-
covered. To conserve tank space and shielding,
the solutions are concentrated by evaporation.
Where storage is to be made in steel containers,
the solution may be neutralized and made
slightly alkaline with commercial caustic. A
neutral or alkaline salt solution or slurry is
developed — the concentration of salts may ap-
proach or exceed saturation values at storage
temperature. The neutral salt concentration of
the waste determines its density. Some types
of reactor elements are not directly soluble in
nitric acid and require solution in combinations
of other mineral acids and catalysts; most ulti-
mately require conversion to nitrates before
complete extraction, however.
The cladding and alloying metals of the reac-
tor elements are also discarded in the wastes.
Aluminum is the most common and abundant
of the metals used ; it appears in concentrations
as high as 80,000 ppm. in final wastes. Zir-
conium will also be present.
Of the various non-radioactive components in
the wastes, the properties of the high-density-
producing salts, of the high nitrate concentra-
tions, and of aluminum are of greatest interest.
The presence of these at present limit the prac-
tical production of selectively adsorbed fission
waste products. If the wastes are concentrated
for economical storage and transportation and
neutralized to limit corrosion, the densities of
the waste liquids will exceed that of sea water.
The temperatures for precipitation of super-
saturated salts in the various wastes are not
known, but it may be assumed that further
sludges will be formed on cooling to deep sea
temperatures — some corrosion-product sludges
already exist.
The solubilities of both normal and radio-
active components of the waste will be condi-
tioned by the presence of nitrates in concentra-
tions exceeding equivalence. Aluminum nitrate
precipitates as a light floe in sea water at con-
centrations as low as 1 ppm. Al. At present
there are no data on its solubility in a sea water
waste mixture. Neither do we know what the
adsorption characteristics of the aluminum floe
in sea water may be.
The range of physical and radiochemical
characteristics that may be anticipated in con-
centrated fuel re-processing wastes and approx-
imate quantities of wastes produced are indi-
cated in the three tables following.
26
Chapter
Properties of Atomic W^astes
27
TABLE 1 Gross Physical and Chemical Char-
acteristics OF Strong Aqueous Wastes From
Reactor Fuel Recovery Processes ^
(Concentrations of non-radioactive components before
evaporation, neutralization, and treatment for
fission removal.)
Range of Molar
Component Concentrations
H 0.07 - 7.0
Al 0.04 - 1.6
Fe 0.05
Zr 0.03 - 0.5
NH4* 0.05 - 2.0
Cr 0.01 - 1.0
Ni 0.03
Sn 0.02
Mn 0.001
Hg 0.001- 0.01
F 0.05 - 3.0
NO3- 0.14 - 7.0
SOr 0.2 - 0.5
Specific Gravity (unconcentrated) . 1.07 - 1.25
Curies/gal. (100 days cooling).. 80 -5200
BTU/hr./gal. (10 days cooling—
50% gamma, 50% beta) 1.37 - 29.4
1 From Tables 4 and 5, Status Report on the Dis-
posal of Radioactive Wastes, ORNL-CF-57-3-114,
F. L. Culler.
TABLE 2 Short-lived Fission Products per
1000 Gm U""^ Reactor Charge At 100 Days
Cooling with 30 Per Cent Burnup ^
Fission Half Beta Gamma
products life 2 Grams curies curies
Y-90 62 h 4.63 748 —
Rh-106 30 s 0 1,514 515
Ce-144 275 d 4.90 16,332 4,900
Zr-95 65 d 1.52 32,647 62,356
Nb-95 35 d 1.61 63,657 65,657
Y-91 57 d 1.11 28,239 —
Sr-89 55 d 0.86 23,253 —
Ru-103 45 d 0.46 13,236 6,618
Ce-l4l 28 d 0.45 10,004 20,008
Ba-137 2.6 m — — 508
Ru-106 290.0 d 0.35 1,514 —
Pr-143 13.8 d 0.02 1,465 —
Ba-140 12.5 d 0.02 1,222 305
La-140 1.7 d — 1,222 1,331
1-131 8.0 d — 23 29
Total 15.93 195,076 162,227
1 From presentation by F. L. Culler, Oak Ridge Na-
tional Laboratory, before Meeting on Ocean Disposal
of Reactor Wastes, Woods Hole Oceanographic In-
stitution, August 5-6, 1954.
- Abbreviations are s for seconds, m for minutes,
h for hours, and d for days.
TABLE 3 Long-lived Fission Products per
1000 Gm U'^ Reactor Charge At 100 Days
Cooling with 30 Per Cent Burnup 1
Half Beta Gamma
Fission products life Grams curies curies
Cs-137 33 y 7.05 563 —
Sr-90 25 y 4.63 748 —
Pr-144 17 m 4.90 16,333 17,966
Te-129 72 m 0.03 1,217 2,435
Total long-lived 16.61 18,861 20,401
Inactive fission products . . 230.00
2 Short T i 15.93 198,564 152,325
Grand total 262.54 217,425 172,726
1 From presentation by F. L. Culler, Oak Ridge Na-
tional Laboratory, before Meeting on Ocean Disposal
of Reactor Wastes, Woods Hole Oceanographic In-
stitution, August 5-6, 1954.
- Short-term fission products from table 2.
Chapter 2
COMPARISON OF SOME NATURAL RADIATIONS RECEIVED BY
SELECTED ORGANISMS^
Theodore R. Folsom, Scripps Institution of Oceanography, La Jolla, California
and
John H. Harley, Health and Safety Laboratory, U. S. Atomic Energy Co?nmission
In attempting to consider in numerical terms
possible consequences to populations from mu-
tations caused by very low levels of artificial
radioactivity, it is instructive to collect for quick
comparison some estimates of the natural doses
to which certain organisms have been exposed
for geological periods. These data emphasize
that doses from natural sources vary widely and
depend not only upon the habitat but also upon
the physical size of the organism; this natural
radiation background varies particularly widely
amongst aquatic organisms.
A very useful summary of natural and arti-
ficial radiation to which human beings are now
exposed has been published by Libby (1955) ;
it has already been quoted and some of his com-
parisons will be repeated here. Nevertheless,
additional radiological factors must be included
whenever the natural exposures of marine or-
ganisms are to be evaluated.
Only sources contributing substantially to
the average dose to the organisms as a whole
will be listed here. The major contributors are
(a) cosmic rays, (b) radioactivity in local sur-
roundings, and (c) radioactivity spread through
the tissue inside the organism itself.
Cosmic rays
Cosmic ray intensity decreases far more rap-
idly from sea level downward than it increases
with increasing elevation above the earth. Fig-
ure 1 and Table 1 show the trend of the ioniz-
ing component of these rays with elevation
above sea level, and with depth in water. The
absolute dose which is used in Table 3 and
Figure 2 is the average of the two values Libby
1 Contribution from the Scripps
Oceanography, New Series, No. 904.
Institution of
(1955) uses for the geomagnetic equator and
for 55° geomagnetic north latitude. (See Fig-
ure 1 and Table 1.)
External activity
Most organisms live close to either (a) igne-
ous or metamorphic rock, (b) sedimentary rock,
or (c) water. Sea water has a characteristic
natural radioactivity — much lower than that
of terrestrial rocks but quite appreciable when
ELEVATION
(FEET)
20,000 r-
10.000 -
400 MRAD/YR
40 MRAC YR
200 1-
OEPTH IN SEA
(METERS)
Figure 1
28
Chapter 2 Natural Radiation of Selected Organisms 29
TABLE 1 Trend of Cosmic Rays with Distance our comparisons the same average radioactivities
Above and Below Sea Level used by Libby (1955) are used here for granite
Variation with elevation above sea level, values of ^nd sedimentary rocks,
intensity of ionizing component (in mrads/year)
taken from Libby (1955). , , , f ,• •,
Internal sources of activity
Mrad/year
' --^. — — ' The bodies of large animals contain a much
Elevation in feet Equator ^'' (mag) higher concentration of potassium than is found
0 33 37 in sea water. A value of 0.2 per cent is used
5,000 40 60 herein for human tissue (Burch and Spiers,
lO'OOO 80 120 1954) and 0.3 per cent is used for the potas-
15,000 160 240 • . F ^ ^ ^ J
2^000 300 450 ^^""^ concentration ot large nsh (Vinogradov,
1953). Since radio-potassium contributes the
Variation with depth in water values computed ^^- portion, aside from cosmic rays, of the
from average attenuation compiled by George (1952) ,. . ,. -u .• . .i j i.^
Tuu • u 1 * • * •* c ^\r. o^l radiation contributing to the average dose to
using Libby s average absolute intensity tor mean sea o o
level. the total body of any marine organisms, the
Percent of surface character and distribution of this important
Depth in meters Mrad/year value natural activity has been compiled in Table 2.
0 35 100
10 10.1 28.8
20 4.86 13.9 Geometrical factors influencing dose
50 1.40 4.0
100 0.47 1.35 A man standing above a granite plane surface
200 0.15 0.42 receives from the granite roughly one half the
300 0.074 0.21 radiation which might strike him if he were
1,000 '.'.'.'.'.'.'.'.'.'. 0^009 ao25 completely surrounded by granite; likewise a
4*000 .......... 0.007 0.002 man in a row boat receives from the sea only
one half the dose which the sea gives to any
compared to that of most natural fresh waters. submerged organism.
The major activity in sea water comes from Potassium yields both beta and gamma ac-
radiopotassium (Revelle, Folsom, Goldberg and tivity; roughly three fourths of the total energy
Isaacs 1955), and only this constituent will be comes from the beta rays. Nevertheless, because
considered here. Of the metamorphic and igne- of its short range, the beta particle from the
ous rocks, granite has the highest activity; for potassium in the surrounding sea contributes
TABLE 2 Potassium Radiation Data
Distribution and Intensities
Material Potassium content Beta rays Gamma rays
d/m/g mrad/yr d/m/g mrad/yr
Sea water 0.038% (1) 0.66 2.7 0.068 0.9
(35%o salinity)
Man 0.2% (2) 3.5 15 0.36 2.3 (4)
Fish (large) 0.3% (3) 5.8 24 0.3 3.7 (4)
Physical Nature of Potassum Activity
Beta activity = 29 d/s/gram of total potassium
Beta ray energy (average) = 0.5 mev
Gamma activity = 3 d/s/gram of total potassium
Gamma ray energy ^1.5 mev
Sample Calculations for Potassium Activity
Beta d/m/g X 1440 X 365 m/yr X 0-5 mev/d X 1-6 X 10^ erg/mev 1000 ^ ^^^^^^^ ^^^^^ ^j^j^j^ ^^^^^^^
100 erg/rad
to. Beta d/m/g X 4.2 = mrad/yr beta; and correspondingly, Gamma d/m/g/ X 12.6 = mrad/yr gamma.
(1) Sverdrup, Johnson and Fleming (1942).
(2) Sherman (1941).
(3) Vinogradov (1953).
(4) Assume half of the gamma rays from internal activity are absorbed inside the body.
30
Atomic Radiation and Oceanography and Fisheries
very little to the total dose of a large animal.
On the other hand the beta rays from the sur-
roundings can appreciably affect very small or-
ganisms and can in fact become the predom-
inant contributor to dose whenever the organ-
ism has dimensions much smaller than the
range of the beta particles in water and tissue.
The effect of beta rays starting from internal
sources also depends upon the size of the organ-
ism. If the organism is very small the beta
bombardment from the outside sources may con-
tribute much more than does internal activity
even though the source of activity is more con-
centrated in the tissue than it is in the surround-
ing water. It would appear from the character
of beta penetration (Friedlander and Kennedy,
■10,000 feet
/
COSMIC RAYS
RAYS FROM
INTERNAL
POTASSIUM
RAYS FROM LOCAL
EXTERNAL SOURCES
\
^\
\
-' '/ 1
\\A\\r '
\ 90 \ \ \
\GRANITE. \
SEDIMENTARY
ROCK
TOTAL NATURAL DOSES (mrad/year)
Man over
granite
Man over
sedinnentary rock
Man over
sea
Large fish
in sea
Micro-organism
in sea
10.000 m.sJ.
75
52
at surf.
lOOm.
at surf.
lOOm.
207 142
64
30
39
5
Figure 2
Chapter 2
Natural Radiation of Selected Organisms
31
1949) that any potassium beta particle which
originates inside a small organism will deposit
most of its energy outside the organism; appar-
ently less than 10 per cent of the total ioniza-
tion can take place inside a sphere having a
mean radius of 0.1 mm, and perhaps from the
activity concentrated inside a phytoplankter hav-
ing a mean radius of 0.01 mm only 1 per cent
of the energy would be felt by the organism
itself. Thus we see that the constitution of the
surrounding medium dominates the life of the
marine microorganism in a radiological sense as
well as in those other manners more familiar to
biologists.
Units used
For quantitative statements concerning such
feeble radiations as these it is logical to use a
very small unit and preferably one which is
defined in terms of energy absorbed; the milli-
rad per year (mrad/yr) is such a unit and is
used here. The rad unit is only slightly larger
than the more familiar roentgen unit, since 1.0
rad by definition causes 100 ergs to be absorbed
per gram of matter, and this is approximately
the energy deposited by 1.1 roentgen of gamma
rays. For converting beta activity to equivalent
rad dosage the average beta energy of potassium
has been taken as being 0.5 mev.
Comparison of natural doses in several dojnains
Figure 2 attempts to bring into a single pic-
ture the magnitudes of the main components
making up the radiation in each of several do-
mains of interest. The approximate total dose
to the organism is listed below the figure so
that numerical comparisons can be made. In
the sea and in deep lakes the dose to small or-
ganisms must be evaluated separately from that
experienced by large organisms. Circumstances
in each domain are given in more detail in
Table 3. (See Figure 2 and Table 3.)
Discussio7t
Small organisms must be considered sep-
arately from large ones. Only a small fraction
of the energy coming from activity inside a very
small organism can be absorbed by the organ-
ism, whereas a large organism cannot escape so
well from its own radioactivity.
Near the sea surface a large fish receives
about half its total natural exposure from the
rays originating in the radio-potassium in its
own tissues. On the other hand near the sea
surface cosmic rays appear to outweigh all other
radiations received by a microorganism.
At depths of the order of 100 meters the
attenuated cosmic rays no longer contribute sig-
nificantly to marine organisms either large or
small. However, the beta and gamma rays from
potassium in sea water can give small organisms
doses amounting to about ten per cent of the
total dose they receive at the sea surface; the
small marine organism cannot escape this expos-
ure to radioactivity in the surrounding water.
It is the deep fresh water which makes pos-
sible the most extreme variation in natural ex-
posure. In the deeper waters living things can
hide from external bombardment; fresh water
generally contains such small amounts of radio-
activity that this source can be neglected even
in comparison with the feeble effect of cosmic
rays remaining at depths of several hundred
meters or more.
In pure fresh water the total dose from
strongly ionizing rays depends largely upon the
size of the organism and upon its living habits.
If the organism is small in the sense already
discussed, if it lives in deeper waters, if it stays
away from the bottom sediments, if it avoids
the neighborhood of large masses of living tis-
sue or of detritus, and if it avoids as far as pos-
sible accumulating excessive amounts of those
elements which can be radio-active — then it
can remain remarkably free from the ionizing
bombardment received by all other living things.
It would be interesting to find out how the
phytoplankton that seek the deeper portion of
the euphotic zone of clear lakes respond to their
extremely low external dose. If morphological
or other differences are discovered between sur-
face specimens and deep-water specimens, then
one of the origins of these differences might
possibly be the extremely different amounts of
strongly ionizing rays in the two biospheres.
Geneticists should not overlook another as-
pect of the minute cell in feeble radiation; an
individual cell has an extremely small proba-
bility of being struck at all during one genera-
tion. In a deep lake the radiation intensity can
be so low that only one phytoplankter in about
five hundred would experience an ionizing ray
before it divided ; at least this is the probability
of a cosmic ray hitting an area 0.1 mm square
32
Atomic Radiation and Oceanography and Fisheries
at 100 meters depth. Furthermore, should an
individual plankter accidentally concentrate an
excessive amount of radioactive material in its
tissue there is little probability that this indi-
vidual would ever pass along any effect of it;
there would be very little chance of a disinte-
gration occuring before division. Purely physi-
cal reasoning therefore indicates that mutations
leading to a capability for accumulating rela-
tively large amounts of activity might be car-
ried to offspring for ten or more generations
before any nuclear energy would be released in
any cell whatever.
Because of the "patchiness" of the radiation,
the use of a unit like the millirad per year for
feeble doses of strongly ionizing radiation un-
fortunately cannot convey the complete picture
of the interesting bombardments which must be
experienced by the very small organism.
TABLE 3 Radiations in Eleven Radiological Domains
Man over granite
1. At 10,000' elevation
Cosmic rays 100 -f granite 90 + internal 17
2. At sea surface
Cosmic rays 35 + granite 90 + internal 17
Man over sedimentary rock
3. At sea level
Cosmic rays 35 + rock 23 + internal 17
Man over sea
4. Cosmic rays 35 -\- sea 0.5 ^ + internal 17
Large fish in sea
5. Near surface
Cosmic rays 35 + sea 0.9 ^ -finternal 28
6. 100 meters deep
Cosmic rays ^ -f- sea 0.9 ^ + internal 28
Total mrads/year
= 207
= 142
= 75
= 52
= 64
= 30
Micro-organism (mean radius 0.01 mm or less) in water
7. Near sea surface
Cosmic rays 35 + sea 3.6 ^ -j- internal ^ =39
8. 100 meters deep in sea or more
Cosmic rays 0.5 -f sea 3.6 ^ -|- internal 3 =: < 5
9. Buried in deep sea sediments
Cosmic rays 0.000 -f clay 40-620 + internal * = 40-620
10. Near fresh water surface
Cosmic rays 35 + water activity - -|- internal - ^35
11. 100 meters deep in a fresh lake
Cosmic rays < 0.5 -|- water activity - + internal - = < 0.5
1 For every radiopotassium disintegration there are 10 betas having average energy 0.5 mev and also one
gamma ray having 1.5 mev. The man receives half the gammas from activity in the sea; the large fish,
substantially all the gammas; while the micro-organism receives gammas and betas together.
2 In fresh water natural activity is extremely low and little of this energy stays in the cell. For example
(Robeck et al., 1954) in the Columbia River the beta background of the water is at or below 1 X 10"* micro-
curie per ml (2 X 10"* d/m/g) while the activity of aquatic organisms is at or below 1 X 10"* microcuries
per gram (2 X 10"^ d/m/g). For comparison, the beta activity in normal sea water is 0.66 d/m/g.
3 The marine microplankton probably carries more internal activity than does the lake plankton, never-
theless effect can be neglected unless activity is concentrated more than 100 fold.
* All deep-water organisms have not escaped radiations. Micro-organisms buried in true deep-sea sedi-
ments have exceptionally high exposure to radium (Love, 1951); they receive 40-620 mrads/year de-
pending upon the type of sediment.
CONCLUSIONS
1. Some humans actually live under exposure
levels surprisingly near the magnitude, 10 roent-
gen during 40 years, which has been suggested
as a genetic tolerance level, i.e., see Figure 2
and Table 2 (domain 1, high elevation over
granite) .
2. A man may experience 207 mrad/year on
high mountains, or 142 on a sandy shore; he
may reduce this further by half, say, by staying
aboard a ship.
3. A large fish experiences a 50 per cent reduc-
tion in dose when going to a depth of 100
Chapter 2
Natural Radiation of Selected Organisms
33
meters; it carries along its own source of in-
ternal radiation, however.
4. A marine microorganism, having a mean
radius of 0.01 mm, receives only about 10 per
cent of the surface dose at a depth of 100
meters in the sea; most of the dose comes from
sea water activity unless exceptionally high in-
ternal activities are accumulated.
5. In a deep fresh water lake those microor-
ganisms living in deep water (but not right at
the bottom) receive from their surroundings
what is probably the lowest natural ionizing dose
within the biospheres of the earth. It would ap-
pear that geneticists should consider seeking
evidence of abnormal mutation rates amongst
microorganisms which live in deep waters of
clear lakes, particularly amongst those which
have low affinity for radioactive elements.
REFERENCES
BuRCH, P. R. J., and F. W. Spiers. 1954. Ra-
dioactivity of the human being. Science
120:719-720.
Friedlander, G., and J. W. Kennedy. 1949.
Introduction to radiochemistry. J. Wiley
and Sons, New York: xiii-f4l2.
George, E. P. 1952. Progress in cosmic rays.
J. C Wilson, ed. '52 Interscience, North-
Holland Publ. Co.: xviii + 557.
LiBBY, W. F. 1955. Dosages from natural ra-
dioactivity and cosmic rays. Science 112
(3158): 57-58.
Love, S. K. 1951. Natural radioactivity of
water. Ind. Eng. Chem. 43:1541.
Revelle, R. R., T. R. Folsom, E. D. Gold-
berg, and J. D. Isaacs. 1955. Nuclear
science and oceanography. International
conference on the peaceful uses of atomic
energy, Geneva. Paper no. 277:22.
Robeck, G. G., C. Henderson, and R. C.
Palange. 1954. Water quality studies on
the Columbia River. U. S. Dept. of
Health, Education, and Welfare. Robert
A. Taft Sanitary Engineering Center; Cin-
cinnati, Ohio: viii + 294.
Sherman, H. C. 1941. Chemistry of food and
nutrition. 6th Ed., McMillan, New York:
x-f6ll.
Sverdrup, H. U., M. W. Johnson, and R. H.
Fleming. 1942. The oceans, their physics,
chemistry and general biology. Prentice-
Hall, Inc.: x + 1087.
Vinogradov, A. P. 1953. The elementary
chemical composition of marine organisms.
Trans. Julia Efron and Jane K. Setlow,
Sears Foundation for marine research, Yale
Univ., New Haven: xiv-f 647.
Chapter 3
DISPOSAL OF RADIOACTIVE WASTES IN THE OCEAN: THE FISSION
PRODUCT SPECTRUM IN THE SEA AS A FUNCTION OF TIME
AND MIXING CHARACTERISTICS ^
Harmon Craig, Scripps Institution of Oceanography, University of California,
La Jolla, California
I. Introduction: Estimated output of nuclear
heat and fission products at "steady state"
nuclear power production
In two other papers in this report, Wooster
and Ketchum discuss mixing rates in the oceans
on the basis of oceanographic data, and the
present writer reviews the natural isotopic stud-
ies which bear on the problem. In this paper
we attempt to construct a detailed quantitative
picture of the fission product spectrum in the
ocean, in steady state with a given fission rate.
Such an attempt may well be termed premature,
in view of our sketchy knowledge of the in-
ternal mixing rate in the sea. Nevertheless, we
know a good deal more today than was known
five years ago, enough at least to make some
simple model calculations which may well yield
correct results to an order of magnitude. More-
over, the construction of a model and the cal-
culation of its characteristics are often highly
informative, and, at the very least, provide a
basis for the orientation of future studies.
The following figures, available in various
sources, are pertinent to the estimation of fu-
ture consumption rates of nuclear power.
Present U. S. electrical energy:
6x 10^ mwh/yr.
Present world electrical energy:
10^ mwh/yr.
Present world energy consumption (all
sources) is about 4.5 X lO^" mwh/yr, doubling
every 30 years.
For the present calculations, we shall assume
a stationary world fission rate of U--^ equal to
1000 metric tons/yr, supplying all the fission
products to be disposed of in the sea. We
shall then attempt to construct as reasonable a
^ Contribution from the Scripps Institution of
Oceanography, New Series, No. 902a.
picture as possible of the fission product ac-
tivity in the sea, when this activity reaches
steady state with the rate of fission, i.e., when
the decay rate of each fission product in the sea
is equal to the rate at which it is being dumped
into the sea, so that its concentration remains
constant. We shall also make some calculations
for a linear build up to such a fission rate in
50 years.
Since 1 gram of U^^^ is equivalent to 24
mwh, our assumed fission rate of 1000 tons of
U235 pej. ygar is equivalent to 2.4 x 10^° mwh/
yr of nuclear heat. At 50 per cent efficiency,
this is equivalent to a world nuclear power
consumption of 1.2 xlO^** mwh/yr. If this
latter figure represents 10 per cent of the total
world energy utilization, we are then assuming
a world consumption of 1.2x10^^ mwh/yr,
which seems not unreasonable as an estimate
for the year 2000 A. D.
Thus a fission rate of 1000 tons of U-^^/yr
represents a 2.7 fold increase in the present
world energy consumption, 10 per cent being
derived from nuclear heat with 50 per cent
efficiency, which should be reached in about
the year 2000 based on the present trend in
energy consumption (see above) . Our calcu-
lations will all be linear with the fission rate,
so that data for other fission rates are easily
derived from the present calculations.
The build up of fission products in a reaactor
is given by:
where / = fission yield (per cent of fissions
yielding an individual fission product, the sum
equalling 200 per cent) , R is the rate of fission
(atoms U^^Yyr) here assumed constant and
equivalent to 1000 tons of U^^^/yr, and N = the
31
Chapter 3
Effects of Time and Mixing Characteristics
35
number of atoms of an individual fission prod-
uct present in the reactor at any time.-
Integration v/ith appropriate hmits gives the
number of atoms of a given fission product in
the reactor as a function of time:
N
= ^(1
')
(1)
where the build up factor (1— e"^^) varies
from 0 to 1 as / varies from 0 to infinity, and
gives the fraction of the equihbrium amount
attained at any time. At secular equilibrium in
the reactor, dN/dt=.0, and xN = fR; we then
have:
N -B.
^^eqlb — ^
(2)
from which one sees that at any time in the
reactor, N = N,g,s (1-^-^0 •
The assumed fission rate of 1000 tons U-^^/yr
is equivalent to 2.2 x lO*' megacuries of fission
(1 curie=3.7x 10^" disintegrations/sec), and
since the sum of the fission yields is 200 per
cent, at equilibrium the total activity of all
fission products present in the world, in mega-
curies, could be roughly estimated by multi-
plying 4.4x10^ by the average number of
radioactive members per fission chain. The
amount of an individual fission product would
be fR/k, using the appropriate decay constant,
and its activity would simply be fR, using the
appropriate fission yield.
The lengths of the fission chains are diffi-
cult to estimate because of the extremely short
half-lives of the first members. However, Dr.
E. C. Anderson (personal communication) has
2 The above equation actually applies only to the
first member of a fission chain; for the build up of
the second member (y) of a chain with initial mem-
ber (x), the correct expression is:
dt
= [/,(! _^-V )+/,,] R_X,N,
where fx and fy are the individual direct fission yields,
and so forth for the succeeding members of each mass
number chain. However the decay constants are very
large for the first members of a chain, and thus one
can neglect the exponential terms and assume a fission
yield which is the total yield of the isotope under
consideration plus all preceding members of the chain,
for all irradiation times with which we shall be
concerned. The experimental fission yield figures gen-
erally refer to the total chain yield, but because of the
very low production of the later members of a chain
by direct fission, there is no error involved in apply-
ing them to the first significantly long-lived chain
member.
Studied the experimental data on the activity
of fission product mixtures directly after fission,
and concludes that for times beyond one day
after cessation of fission, on the average only
^ of the chains are still active (i.e. from this
time on there are left only about 0.3 radioactive
members per pair of fission chains initiated).
Thus he points out that assuming a fission rate
of 1000 tons U^^^/yr as used above, and taking
one day as an assumed minimum delay between
accumulation and disposal, the steady activity
in the sea for continuous stripping and disposal
after one day would be roughly 7 x 10^ mega-
curies. This is about the same total activity as
that found below for an average irradiation
time of one year with a 100-day cooling period
before disposal, namely 7.7 xlO^ megacuries
(see calculations in Section IV and Table 1).
The rough agreement of these numbers merely
emphasizes the great predominance of the few
long-lived isotopes of high fission yield in the
fission product activity after very short times.
II. Rate of introduction of fission products into
the sea
A more realistic picture is obtained by con-
sidering the irradiation time, or reactor holding
time for uranium slugs, which is limited by
structural weakening from irradiation, poison-
ing by fission products, etc., and the cooling
period necessary for safe handling and for the
growing in of plutonium in breeder piles. We
assume the fission products of the world are
distributed between (1) reactors, (2) cooling
pits, and (3) the oceans (or any gross disposal
site for that matter). The distribution among
these reservoirs and the fission product spec-
trum in each depends on the irradiation and
cooling times.
We shall assume an irradiation time of t^
years, equivalent to any of the following physi-
cal interpretations:
1. The reactors of the world are operated, on
the average, t^ years, then stripped down and
rebuilt.
2. The reactor slugs are continuously pushed
through the reactors, each spending, on the
average, tj. years in the reactor.
3. Continuous stripping into a holding tank
which is opened every t^. years for removal of
fission products.
36
Atomic Radiation and Oceanography and Fisheries
From these sources, the fission products are
assumed to enter the coohng pits, from which
they are dumped into the sea.
At the end of the irradiation time /,., the
amount of a fission product is given by (1) as:
A ^
-X?,-
(3)
Assuming for the moment no coohng time, the
fission products are stripped out every t^ years
and dumped into the sea. Thus the introduc-
tion rate into the sea of a given fission product
is equal to its activity Ag in the sea at steady
state, and is given by Nt,./tr or:
.=£(.-.
)
(4)
where /^ denotes the coohng time, here assumed
to be 0.
The activity of the fission products in the
world reactors at any time, A,., may be evaluated
in the following way. The fission products are
stripped out every /,. years, and N,., the amount
in the reactors, varies from 0 to N(,. in cycles,
as / varies from 0 to t^. For many reactors
operating independently (the sum of the fission
rates being R) with random distribution on the
/,. cycle, we take the average of N^ consistent
with R by integrating equation (1) from 0 to
/,. and dividing by /,.; i.e., the steady state value
of N,. is:
N.=
fR
(l-e-^*)dt
Performing the integration, and setting A,.z=
\Nr, we have for the steady state activity of a
fission product in the reactors of the world:
AJ~lXt,-(l-e^^'r>^-]
A',-
(5)
and from equations (4) and (5) we see that
Ng + N^ = fR/X = N,,j,f„ the total amount of the
fission product in the world, as of course it
must.
Still neglecting cooling time, the fraction of
the world total of a fission product which is
in the sea is given by N,/Np^,5 = /l.,/^c,^;b =Fg,
and:
Fmif-o)-.
(1
-xf,
Xtr
(6)
Neglecting cooling time, the effect of irradia-
tion time may be demonstrated by considering
the long and short-lived radioisotopes of stron-
tium, calculating the fraction of the world
totals, for the assumed fission rate, which is in
the sea, as a function of t^, as given below.
tr (years)
5;-9o (28^)
Sr^^ {5 Ad)
0.1
99.9
79.8
0.5
99.4
38.6
1
98.8
21.2
2
97.5
10.7
10
88.5
2.1
Equation (6) shows the following character-
istics:
For long half-lives (A/r small): Fg = \ — -^
. . .(approaching 1).
For short half-lives (A/;.>5): Fg =
Xtr
For /,. = 1 year, and for any isotope with a half-
life of less than 60 days:
Fg = 0.4/^/0 (where /i/., is here in days, /<,=
0).
Thus, as shown above, increasing the irradia-
tion time from 0.1 to 1 year cuts the fraction
in the sea of a 60 day isotope by ^-, neglecting
cooling time effects, but does not affect the
long-lived isotopes.
We next interpose the cooling time between
the reactor stripping and the disposal in the
sea. The amount of an isotope left after the
cooling period is:
N, = Ntre~^'<'
and from (4), the steady state activity of a
given fission product in the sea, equal to its
introduction rate, now becomes:
■ A/, ^
and F, is reduced to
A. = l^ {I -e-''r>^{e -'''=) (7)
>-t r\ /^->''(
F,=
Xfr
(8)
III. Fission product concentration in the sea as
a junction of linearly increasing fission rate
We can get some idea of the transient char-
acteristics of the fission product spectrum in
the sea by examining the build-up of fission
products with an increasing rate of fission. We
Chapter 3
Effects of Time and Mixing Characteristics
37
\t-XN
shall take R, the world rate of fission, as 0 at
the present time (^ = 0) and increasing linearly
from the present time until it reaches the 1000
ton rate in 50 years. We shall further assume
continuous stripping of fission products into
the sea, and examine the transient character-
istics of long-lived and a short-lived fission
product.
The rate of increase of a fission product in
the sea is given by:
dN ,{R\
where {R/t) is a constant by virtue of the
assumed linear increase from R = 0. N is now
the amount of a fission product in the sea at any
time t. We thus have:
dN+{xN-{jR/t)tyt = 0
Multiplication by e'^^ makes the equation exact,
and the solution is:
Evaluating the constant from N = 0 at / = 0, we
have the general solution:
N, = i|[A/- (1-^-0} (9)
where N^ is the amount in the sea at the time /,
Multiplication by A. to give the activity is seen
to give an equation of the same form as (5)
for the steady state amount in reactors, except
that in (9) both R and / are variables, with
R/t being constant.
We take i?=:0 at the present time, increas-
ing linearly to 1000 tons U-^Yyear in 50 years.
As noted previously, this rate is equivalent to
2.2x10^ megacuries of fission, and thus R/t —
4.4 X 10* megacuries/year. Thus the activity of
a fission product in the sea at any time / is
given by:
At^AAxlO'Uxt-il-e-^t)'] (10)
A
where A^ is in megacuries, A = yrs-^, / is in
years, and / is the fission yield. We tabulate
below the increasing activity in the sea for a
long-lived and a short-lived isotope with con-
tinuous stripping into the sea.
Activity (megacuries) in the sea
SfOO 1131
/i/2 = 28}/ t-,/^_ — Sd
t (years)
/ = 0.05
/ = 0.028
1
26.4
1200
10
2640
12,300
50
4.8x10*
6.2x10*
100
1.4x105
1.2x105
200
3.5x105
2.4x105
1000
2.1 xlO^
1.2x10*5
At 50 years, when the fission rate of 1000
tons/year is reached, the Sr^o activity is half
the amount which would be in steady state with
this fission rate with an irradiation time of 1
year (see below and Table 1 ) . If R continues
to increase at the same rate, the steady state Sr^**
activity for constant R is reached in about 100
years, and thereafter the activity increases lin-
early at a rate given by: At = 2200{t — A0), the
mean life of Sr^o being 40 years. The factor
(l_^-\f) grows in to 95 per cent at 3 mean
lives or 4 half-lives.
With a constant fission rate of 1000 tons
U-^5y'year, irradiation time one year, and no
cooling time, the I^^^ steady state activity in
the sea would be 2000 megacuries (calculated
as in Table 1, but with no cooling time) . With
the linear increase of fission rate and continu-
ous stripping as shown above, this level is sur-
passed in two years. These data illustrate rather
strikingly how rapidly the short half-life iso-
topes build up to secular equilibrium with an
increasing fission rate. Sr^** does not equal the
P^^ activity until after 100 years of dumping
into the sea, under the above conditions. For
all species which have grown into secular equi-
librium with the increasing fission rate, the ac-
tivity ratios in the sea are simply given by the
fission yield ratios.
IV. Steady state fission product spectrum in a
homogeneous, rapidly mixed sea
The first three columns of Table 1 list all
the fission products of any significance, together
with their half-lives and fission yields. Col-
umns 4 and 5 show the total amounts of each
isotope in the sea, in metric tons and mega-
curies of activity respectively, in secular equi-
librium with a fission rate of 1000 tons U-^5
38
Atomic Radiation and Oceanography and Fisheries
per year (2.2 xlO*' megacuries of fission), as-
suming an irradiation time (Z^) of one year, and
a cooling time (/g) of 100 days (0.274 years).
With such conditions, the expression for the
activity of each fission product in the sea, as
given by equation (7), becomes:
A,= ~{l-e-^){e'<^-^-''-^)
X 2.2 X 10*^ megacuries (11)
where A is in years- ^.
For half-lives greater than 1 year there is
essentially no reduction in the oceanic activity
by the cooling time. For all isotopes with half-
lives greater than 5 years, more than 90 per
cent of the isotope will be in the sea at steady
state.
Of the 30 isotopes shown, 22 are independ-
ent and 8 are short-lived daughters which come
quickly into secular equilibrium with their par-
ents, decaying thereafter with the activity of
the parent. Cs^^^ has a branching decay with
8 per cent going directly to the ground state of
Ba^^^; thus the secular activity of Ba^^"'" is only
92 per cent of the parent activity. The activities
listed are beta activities only, for all isotopes
except Bais'"^, Tei^sm, and Cd^^m^ which decay
from their excited states by gamma emission.
The Sm and Eu activities depend on the actual
rate of burn-up in the reactors, and may vary
considerably with different reactor conditions.
In the calculations, the first long-lived mem-
ber of each fission chain was taken, and the
fission yield for the entire chain was used for
this isotope. The direct fission yield for the
11 -day Nd which lies above the 2. 5 -year Pm
in the 147 fission chain is not known, and thus
this isotope has been neglected; the Nd comes
quickly into secular equilibrium in the reactor,
so that the total chain fission yield can be used
for the Pm calculation.
The fission products are listed in order of
decreasing total activity in the sea, with radio-
active daughters paired with their parents. The
total amount of all fission products in the sea
is found to be about 3200 metric tons, cor-
responding to almost one million megacuries of
activity. This represents almost twice the pres-
ent activity in the sea, which is mainly due to
the radioactivity of potassium 40. The figures
for K*" and Rb^^ are shown for comparison,
the activity of the other radioactive elements
in the sea being negligible relative to these
isotopes.
We shall now discuss the effects of the mix-
ing barrier at the thermocline in the sea on the
distribution of the fission products between the
deep sea and the upper mixed layer of the sea.
V. Distribution of fission products between the
deep sea and the mixed layer
We shall assume a simple model, convenient
for calculation, in which we divide the ocean
into two geophysical reservoirs: a mixed layer
above the thermocline, and the bulk of the
ocean, termed the "deep sea," below the ther-
mocline. The exchange of fission products be-
tween these two reservoirs is assumed to be a
first order process, the rate of removal of a
fission product from a reservoir being simply
proportional to the amount of the isotope in
the reservoir. The thermocline is assumed to
represent the boundary across which the hold-up
in mixing takes place.
Thus, for example, the rate of transfer of
water from the mixed layer to the deep sea is
assumed to be k^N^, where N,^ is the mass of
water in the mixed layer and k^ is the exchange
rate constant for transfer of material from the
mixed layer to the deep sea. In general, we
write ki as the fraction of material in reservoir
/ removed per year.
The residence time of a molecule in a reser-
voir, T, is defined as the average number of
years a molecule spends in the reservoir before
being removed by the physical mixing process.
The meaning of t may be shown by the follow-
ing derivation which gives a rigorous definition.
Assume a reservoir with a steady-state fixed
content of N molecules of a substance, and a
continuous flux into and out of the reservoir
of </) molecules/year. At a particular time, / = 0,
we have Ng particular molecules in the reser-
voir, and at some later time /, we have N' of
these original Nq molecules still present. Then
we define the average life of a molecule in the
reservoir in the usual way, as
/=co,N' = 0
t = 0, N' = No
where ni is the number of molecules of the
original Nq which remain in the reservoir for
each time /,-, and dN' is the number of mole-
Chapter 3
Effects of Time and Mixing Characteristics
39
cules removed in the interval / and t-\-dt, i.e.,
the number of molecules with a reservoir life-
time equal to /.
The number of molecules of the original
particular set of N^ which are removed in any
interval dt is simply given by the concentration
of such molecules in the reservoir, multiplied
by the total flux from the reservoir, i.e.:
N'
dN'=--^dt
which yields on integration N =Nq exp
Substituting for dN' and then for N' in the
integral expression for t, and integrating be-
tween t = 0 and infinity, we obtain:
N
and from the expression for N' one sees that
T, the average life, is also the time required
for the original number of N^ particular mole-
cules to be reduced to l/e times the initial
number, r is thus formally equivalent to a
radioactive mean life.
In our particular model we are assuming the
rate of removal to be dependent only on the
total amount of substance, N, in the reservoir,
so that the outgoing flux is given by <^=zkN.
In such cases we see that j—X/k, just as the
radioactive mean life is equal to 1/A. The total
removal rate of a radioactive isotope from a
reservoir is of course the sum of the physical
removal rate and the radioactive decay; t as
defined above refers only to the residence time
relative to physical removal.
The symbols used in the following discussion
are listed below, where / refers to the subscripts
m and d for the mixed layer and deep sea.
N^, Fj.' mass and volume, respectively, of
water in reservoir /.
Nj*=r amount of any fission product in reser-
voir /'.
/ifj = activity of any fission product in reser-
voir / ( = xNi), in megacuries.
^1= activity of any fission product per unit
volume of sea water in reservoir ;',
y^i = exchange rate constant, = fraction of
material in reservoir / removed per
year.
Ti= residence time in reservoir / relative
to physical removal, —l/ki.
w = average depth of mixed layer of the
sea (taken as 100 meters).
D = average depth of the ocean (taken as
3800 meters) .
We assume that the fission products are intro-
duced into the deep sea after the 100 day cool-
ing period, the disposal rate or flux of a given
fission product isotope, termed ^, being equal
to the steady-state total activity in the sea Ag
as given by equation (11) . </> is thus in "mega-
curies of flux," = atoms/sec divided by 3.7 X
10^°. We wish to ask what steady-state activity
per unit volume of water will be in the mixed
layer, as a function of the rate of cross-thermo-
cline exchange of sea water and fission products.
The water balance between the reservoirs is
given by:
k,,N„, = kaNa
or, neglecting density differences which are not
important for these calculations,
^ = — ^ (12)
The fission products are introduced into the
deep sea with a rate of introduction for any
give isotope 0. The radioactive balance in the
two reservoirs is then given by:
Deep sea: 4> + K,Nn, = kJS!i+xN^
Mixed layer : k^N^ = k„,N* + AN,'
Total : </> = A (N,; -}.N*a)=A, = A,^ -f- A,
From (12) and (14)
NJ
(13)
(14)
(15)
— "^"^ _L \
or:
^d _
D-m
A,
+ \ra
Thus for a stable element (A = 0) the partition-
ing is simply statistical. From (15):
-^m =
D/m + \Ta
(16)
which gives the total activity of any fission
product in the mixed layer as a function of
decay constant, relative sizes of the mixed layer
and deep sea, and exchange rate between the
reservoirs as given by ra-
Various estimates of the value to be assigned
to Td may be obtained from the separate papers
by Wooster and Ketchum, and by Craig, in this
report, and are discussed in relation to this
40
Atomic Radiation and Oceanography and Fisheries
particular model in the paper by Craig. From
these discussions, we choose for the present
calculations a value Td=300 years as perhaps
the best guess. As discussed by the writer in a
separate chapter of this report, radio carbon data
indicate a residence time for water of about
1000 years, as a world-wide average. Mixing
in the Atlantic is probably a good deal faster
than in the Pacific, and 300 years is probably a
safe lower limit estimate for the Atlantic, con-
sidering the material to be deposited on the
bottom. Thus the mixed-layer activities we cal-
culate should be upper limits, which would be
approached more closely in the Atlantic than in
the Pacific.
The average world-wide depth of the mixed
layer, w, is taken as 100 meters, and the average
depth of the sea is taken as 3800 meters. The
volume of the sea is 1.4xl02i liters; thus the
volume of the mixed layer is taken as 1/38 of
this or 3.7x10" liters. Putting these nu-
merical values into (16), and noting that ^ =
Ag, we have for the activity of any fission prod-
uct per unit volume of sea water in the mixed
layer:
10-3 A
a^= ^^ dps/liter (17)
'" 300A+38 ^ ' ^ '
in disintegrations per second per liter, where
Ag is in megacuries, as tabulated in column 5
of Table 1, and A is in years^^ From this
equation the values tabulated in column 8 of
Table 1 were calculated, and were converted
to microcuries per liter for column 9.
From the relation aa/a„^= {A^Vm/^mVd) =
(Aa/A,„) (m/D-m) we obtain:
— =At,h-1-1
where Tm> the residence time of a water mole-
cule in the mixed layer, is given by (12) as
1/37 of Td = S.l years. We thus write:
-^=8.1A+1:
(18)
from which, given the values of a^n computed
above, the values of a^ tabulated in column 7
of Table 1 were computed. We call a the
"oceanographic partition factor." It is a func-
tion of the mixing rate of the sea and the decay
constant of the individual isotope, and is a
measure of the effectiveness of the cross-thermo-
cline exchange rate in buffering the mixed
layer from the fission products introduced into
the deep sea. Values of a are tabulated in
column 6 of the table, and range from about
1 for the longest lived isotopes to about 250
for an isotope with a half-life of 8 days. For
stable isotopes A is 0, a is 1, and (18) reduces
to simple statistical partitioning.
From (17) we see that as A, the decay con-
stant of an isotope, increases, the activity in
the mixed layer decreases; i.e., if more of the
isotope can be removed from the deep sea by
decay, less needs to be transferred to the mixed
layer to preserve the steady state. If the half-
life were so long that the radioactivity did not
affect the distribution between the mixed layer
and the deep sea, we would have simply a sta-
tistical partitioning of the isotope between these
reservoirs, such that the activity per unit volume
in each reservoir would be the same. From the
above equations we can derive the ratio of the
activity in the mixed layer for an isotope to the
activity per unit volume which would be ob-
served if the partitioning were statistical:
/ X -- (19)
a^{stat) aTa+Tm a
and we see that a~^ is approximately the frac-
tion of the statistical activity per unit volume
attained by a fission product in the mixed layer.
Equation (19) can be written exactly as:
_ ^1/
a^(stat) /1/2 + 5.5
(20)
where /^/o is the half-life of the isotope in years.
The ratio a„J a^-y^{stat) is plotted in Figure 1
as a function of the half -life, and one reads,
for example, that an isotope with a 5 year half-
life attains about 48 per cent of the activity
per unit volume in the mixed layer which it
would have if its half-life were so long, relative
to the mixing rate in the sea, that its radio-
activity had no effect on its distribution.
The values of a^^, a^, and a are tabulated in
Table 1, in which the isotopes are arranged in
order of their activity in the deep sea. For
comparison, the activities of potassium 40 and
rubidium 87, which provide essentially all the
radioactivity in the sea, are also listed. In the
deep sea, the predicted fission product activity
is 19.3 disintegrations per second per liter, as
compared with the natural activity of 12.2 dps/
liter; thus the fission products in steady state
with the 1000 ton fission rate would almost
triple the deep-sea activity.
Chapter 3
Ejfects of Time and Mixing Characteristics
41
TABLE 1 Fission Product Spectrum in the Ocean At Steady State Disposal into Deep Sea. Calcu-
lated FOR Fission Rate of 1000 Tons U^Vyr (2.4 X lO"' mwh/yr of Nuclear Heat), Irradiation
Time of 1 Yr and Cooling Time of 100 Days. Average Life of a Water Molecule in the Deep
Sea Taken as 300 Years; Average Depth of the Mixed Layer Taken as 100 Meters.
Total amount in ocean Activity (dps/liter)
, A ^ ^ A ^ am
Half- Fission Metric Activity a = aa am Microcuries
Isotope life yield % tons megacuries ad/a™ Deep sea Mixed layer per liter
5oCs"' 33 y 6.3 1750 1.4X10' 1.17 3.64 3.12 8.4X10"'
seBa^'"" 2.6 m — — 1.3X10' — 3.35 2.87 7.7X10"'
ssSr"" 28 y 5.0 780 1.1 X lO' 1.20 2.90 2.42 6.5X10"'
sflY"" 64 h — 0.20 1.1 X 10' — 2.90 2.42 6.5 X 10"'
ssCe'" 280 d 5.3 19 6.0X10* 8.32 1.62 0.19 5.2X10""
BsPr"* 17.5 m — — 6.0X10* — 1.62 0.19 5.2X10""
eiPm"' 2.5 y 2.6 48 4.6X10* 3.24 1.23 0.38 1.0X10"'
62Sm''' 100 y 0.7 630 1.5X10* 1.06 0.40 0.38 1.0X10"'
«,Zr" 65 d 6.4 0.58 1.2X10* 32.5 0.33 1.0X10"= 2.7X10"'
uNb"' 36 d — 0.32 1.2X10* — 0.33 1.0 X 10"" 2.7X10"'
39Y" 60 d 5.9 0.39 9.4 X 10' 35.1 0.25 7.2 X 10"' 1.9 X 10"'
44Ru'°" 1 y 0.5 2.0 6.6 X 10' 6.6I 0.18 2.7 X 10"^ 7.2 X 10"'
isRh^"" 35 s — — 6.6 X 10' — 0.18 2.7 X 10"' 7.2 X 10"'
38Sr"« 54 d 4.6 0.22 6.0 X 10' 38.9 O.I6 4.1 X 10"' 1.1 X 10"'
u^xx^'^ 40 d 3.7 7.2 X 10"' 2.3 X 10' 52.0 6.1 X 10"' 1.2 X 10"' 3.2 X lO"*
ioRh^"' 55 m — — 2.3X10' — 6.1X10"' 1.2X10"' 3.2X10""
ssCe'*^ 32 d 5.7 6.3X10"' 1.8 X 10' 65.0 4.9X10"' 7.6X10"* 2.0X10^
esEu^" 2y 0.03 0.44 5.1X10' 3.8 1.4X10"' 3.6X10"' 9.7X10^
ooTe^"'" 33 d 0.3 3.4X10"' 1.0 X 10' 63.4 2.8X10"' 4.4X10"' 1.2X10""
saTe^" 70 m — — 1.0 X 10' — 2.8X10"' 4.4X10"' 1.2X10""
59Pr"' 13.7 d 5.4 — 40 151 1.1X10"' 7.2X10"" 2.0X10""
BeBa"" 12.8 d 6.1 — 30 161 8.0X10"* 5.0X10"" 1.3X10""
57Lai*" 1.7 d — — 30 — 8.0 X 10"* 5.0 X 10"" 1.3 X 10""
5oSn^ 130 d 1.2 X 10"' — 6.8 16.8 1.8 X 10"* 1.1 X 10"' 3.0 X 10""
Xd"'" 44 d 8 X 10"* — 0.64 47.4 1.7 X 10"' 3.6 X 10"' 9.8 X 10""
B3P' 8 d 2.8 — 0.35 256 9.5 X 10"" 3.7 X 10"^ 1.0 X 10"''
esEu^'" 15.4 d 0.01 — 0.15 134 4.0X10"" 3.0X10"' 8.0X10""
bbCs"" 13.7 d 0.01 — 7.5X10"' 151 2.0X10"" 1.3X10"' 3.6X10""
BoSn^' 10 d 0.02 — 1.7 X 10"' 206 4.7 X 10"' 2.3 X 10"" 6.2 X 10"**
47Ag*" 7.6 d 0.018 — 1.4X10"' 268 3.9X10"' 1.4X10"" 3.9X10"*'
Totals: 3230 7.7 X 10' 19.3 12.1 3.2 X 10"*
Natural potassium and rubidium in the sea:
K*" 6.3 X 10" 4.6 X 10' 1 12 12 3.2 X 10"*
Rb" 1.2 X 10** 8.4 X 10' 1 0.22 0.22 5.9 X 10""
All activity values are Beta activities only, except where isomeric transitions are indicated.
Conversion: 1 disintegration per second ^ 2.7 X 10"' microcuries.
1 curies: 3.7 X 10*" disintegrations per second.
42
Atomic Radiation and Oceanography and Fisheries
0.1
.4 .5
2 3 4 5 iO
HALF-LIFE (YEARS)
Figure 1
30 40 50
100
However, the effect of the internal mixing
rate of the sea in the model adopted, is to cut
the activity in the mixed layer down to 12.1
dps/liter which is, by coincidence, just equal
to the natural activity and which would thus
just double the activity in the mixed layer.
It should be noted that the figures given in
the table for the predicted activities in the
mixed layer refer only to cross-thermocline mix-
ing by physical processes, exclusive of biological
transfer through the thermocline. However,
the figures listed provide a basis for speculation
on the hazardous effects of the mixed layer
activity, in that comparison may be made with
biological concentration factors, discussed else-
where in this report, to predict the activity
levels in marine organisms. In this way, rough
predictions may be made of the hazard to man,
not only by direct exposure to the waters of the
mixed layer of the sea, but by the activity con-
centrated in marine organisms used for food.
Chapter 4
TRANSPORT AND DISPERSAL OF RADIOACTIVE ELEMENTS IN THE SEA '
Warren S. Wooster, Scripps Institution of Oceanography, La Jolla, California
and
BosTWiCK H. Ketchum, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts
The fate of radioactive elements in the sea
differs from that of non-radioactive elements
since they are subject to radioactive decay.
Otherwise, concentrations of radioactive ele-
ments are changed by the same physical and
biological processes as are those of other iso-
topes in the same physical state. Thus the fate
of radioactive material introduced into the sea
depends on:
1. What is introduced — the nuclide, its radio-
active properties (half -life, nuclear reaction,
kind and energy of radiation), its physical state
in sea water (whether particulate, colloidal or
ionic) and its chemical properties (including
its role in biological processes).
2. Where it is introduced — position and depth
with respect to the density and velocity struc-
ture of the sea.
This paper describes the physical processes
whereby radioactive elements in true solution
are diluted by mixing and are carried from one
part of the ocean to another. Although all parts
of the open ocean appear to be in continuous
motion and in communication with each other,
the rates of this motion and exchange cover
such a wide range that it is convenient to con-
sider separately the questions of near-surface
vertical and horizontal exchange, intermediate
and deep circulation, and the exchange between
the deep sea, coastal areas and enclosed basins.
Near-surface circulation
In middle and low latitudes the surface layer
of the ocean, from 10 to 200 meters thick, is
'^ Contribution from the Scripps Institution of
Oceanography, New Series, no. 903. Contribution no.
870 from the Woods Hole Oceanographic Institution.
This paper, in part, represents results of research car-
ried out by the University of California under con-
tract with the Office of Naval Research. Reproduction
in whole or in part is permitted for any purpose of
the United States Government.
separated from the colder deep waters by a
layer of rapid density change and great sta-
bility, the pycnocline or thermocline. This
intermediate layer varies in depth and stability
from time to time and from place to place. At
times there are two such layers, the seasonal
thermocline and a deeper main thermocline.
The surface layer is often called the "stirred"
or "mixed" layer ^ because of its relative uni-
formity in temperature and in concentrations of
dissolved substances.
It is believed that radioactive material in-
troduced into this surface layer will be rapidly
distributed vertically throughout the layer. The
general uniformity of concentrations within this
layer suggests that forces are present which tend
to bring it about. Because density increases
only slightly with depth through the layer,
little energy is required for vertical stirring.
Some evidence of the rapidity of vertical
mixing in the upper layer is given by Folsom
(Revelle, Folsom, Goldberg and Isaacs, 1955),
who observed that when fission products were
introduced at the surface in an area where the
surface layer was about 100 meters thick, the
lower boundary of the radioactive water reached
the bottom of this layer in about 28 hours.
Within this period of time radioactivity had be-
come uniformly distributed vertically through-
out the layer.
Rapid vertical mixing in the upper layer is
brought about primarily by the following two
processes:
1. Convection: When the density of surface
water is sufficiently increased, owing to either
2 A distinction is made here between stirring and
mixing. In stirring, one causes relative motion of
different parts of the liquid, and the average value
of the gradient is increased. Mixing then takes place,
the gradients disappearing and the liquid becoming
homogeneous (Eckart, 1948).
43
44
Atomic Radiation and Oceanography and Fisheries
a decrease in temperature or an increase in
salinity, the surface water sinks and mixes with
deeper water. Convection is maintained by
(a) surface coohng due to long wave radiation
and heat conduction to the atmosphere, (b) the
loss of latent heat and water vapor in evapora-
tion, or (c) the increase of surface salinity from
free2ing of surface water.
2. Wind stirring: Vertical turbulence in the
upper layer results from wind action on the sea
surface. The extent of wind stirring depends
both on the magnitude and uniformity of wind
stress and on the vertical density gradient. Stir-
ring is effective only to a depth where there is
sufficient energy to overcome the effect of sta-
bility. Both the homogeneity and the depth of
the upper layer are affected by wind. Single
gales have been observed to deepen the surface
layer on the average by about 20-30 feet,
(Francis and Stommel, 1953).
Rapid vertical mixing may be brought about
by other processes. Thus in shallow coastal
areas stirring by strong tidal currents is im-
portant. Stirring may also be accomplished by
the vertical component of currents, particularly
in regions of upwelling and sinking.
It should be noted that even above a well-
developed pycnocline there is not complete ho-
mogeneity within the so called "mixed" layer.
Concentrations of those elements affected by
biological activity (such as oxygen and phos-
phorus) may show significant variation within
the euphotic zone. Even so-called "conserva-
tive" concentrations (temperature and salinity)
may not be uniform within the surface layer.
Such heterogeneity may be attributed to in-
complete vertical mixing or to vertical shear in
the surface layer.
When radioactive materials are introduced
into the near-surface layer, they are transported
away from the area of introduction by surface
currents. These currents extend, in general,
through the entire depth of the upper layer
and seem to be driven, directly or indirectly,
by the wind.
The average locations and velocities of the
important surface currents of the world ocean
have been studied for many years and are well
known (see, for example, Deutsche Seewarte,
1942; U. S. Navy Hydrographic Office, 1947
a and b, 1950; Sverdrup, Johnson, and Flem-
ing, 1942, ch. 15). This knowledge comes
primarily from averages of countless ship-drift
observations, and from computations based on
the observed subsurface distribution of density.
These calculations give mean speeds as high
as 193 cm/sec (90 miles per day) in the
Florida Current (Montgomery, 1938a) and 89
cm/sec (41 miles per day) in the Kuroshio
(Koenuma, 1939). The volume of water flow-
ing through the Florida Straits in 15 years is
about equal to that of the upper 500 meters of
the whole North Atlantic. Similarly, between
the northern Ryukyus and Kyushu, the Kuro-
shio transports a volume equivalent to that of
the upper 500 meters of the North Pacific in
about 50 years. It seems likely that there is
no area of surface water in the ocean that can
be considered as isolated from the remaining
surface waters.
Recent intensive studies of the Gulf Stream
and other surface currents, using such modern
instruments as the bathythermograph, electronic
navigational aids, and geomagnetic electro-kine-
tograph (GEK), have revealed complicated fine
structures, with filamentous jets and counter-
currents not apparent in the average picture
(Fuglister, 1951). Characteristic maximum sur-
face velocities measured by GEK and Loran
dead reckoning in the Gulf Stream were found
to fluctuate between 150 and 300 cm/sec or
70 to 140 miles per day (von Arx, Bumpus
and Richardson, 1955). Thus, in estimating
the time at which radioactive materials will be
found at various distances from the area of
introduction, one must be cautious in the use
of average surface current speeds.
Direct evidence of the transport of radio-
active materials by surface currents in the
western Pacific is given by "Shunkotsu-Maru"
survey (Miyake, Sugiura and Kameda, 1955)
and the "Taney" survey (U. S. Atomic Energy
Commission, 1956) four months and thirteen
months respectively after nuclear weapons tests
in the Marshall Islands in March, 1954. The
earlier survey found significant levels of radio-
activity at a distance of 2000 kilometers from
Bikini, suggesting a westward drift of more
than 9 miles per day (about 20 cm/sec) . The
later survey found significant levels of radio-
activity at least 7000 kilometers downstream
from Bikini ; this gives about the same minimum
westward drift.
In addition to being drifted away from the
area of introduction, radio-active materials are
Chapter 4
Transport and Dispersal
45
dispersed by diffusion. Diffusion in the ocean
is caused by turbulence or eddies, and the
coefficient of eddy diffusivity is usually more
than a million times the corresponding molecu-
lar coefficient. The rate of eddy diffusion de-
pends on wind speed, current shear, density
gradient, gradient of the diffusing concentra-
tion, direction of diffusion, and the dimensions
of the phenomenon. The calculated rates de-
pend upon the magnitudes of eddy diffusivity
coefficients used, and they have been estimated
by a number of methods (Sverdrup et al., 1942,
p. 484-485; Munk, Ewing and Revelle, 1949).
Because of both the large number of variables
concerned and the present unsatisfactory state
of our quantitative knowledge of turbulence in
the ocean, it is difficult to predict the diffusion
of radioactive materials under any given cir-
cumstances. The most satisfactory approach at
present is to conduct diffusion studies and ex-
periments at the place and under the conditions
of contemplated release. The results are only
applicable to the particular areas.
During the 1946 preliminary survey in Bikini
Lagoon, the state of turbulence was determined
by a variety of measurements, and the subse-
quent observed distribution of radioactivity was
in close agreement with the predicted values
(Munk, Ewing and Revelle, 1949) . A mean
value for the radius of the contaminated area
was 3 km., which approximately doubled be-
tween the first and second days after the burst.
The initial distribution of radioactivity as de-
posited by the atomic bomb was patchy, and
the turbulent eddies, which spread the con-
tamination over a larger area, did not appreci-
ably reduce this patchiness during the first
three days.
Another pertinent study was made by Ketchum
and Ford (1952) who examined the rate of
dispersion of acid-iron wastes in the wake of
a barge at sea. Computed mixing coefficients
showed a tendency to increase with increasing
time, and thus with the dimensions of the mix-
ing field, and the radius of the contaminated
area was observed to double in time periods
ranging from 0.5 minutes to 35 minutes. It
should be noted that the scale of this phenom-
enon was about 10-- that of Munk, Ewing and
Revelle (1949) ; they show that the ratio of
lateral eddy diffusivity coefficient to the radius
of the area considered is relatively constant
over a range of radius between 10^ and 10^ cm.
A large scale tracer experiment was carried
out in the Irish Sea prior to the discharge of
radioactive effluent (Seligman, 1955). During
each experiment, 10 tons of 6.7 percent fluores-
cein solution were introduced near the surface
during a 20-minute period, and the sensitivity
of subsequent detection was believed to be of
the order of 1 part in 10^. Maximum concen-
trations detected directly after release were 10~*
of the original concentration; 12 hours after
release, they were down to 5 x 10"^ of the
original concentration. The trial area was prob-
ably part of an eddy and was subject to tidal
mixing, so the results may not be generally
applicable.
Exchange hetiveen near-surface and intermediate
xaaters
Since the surface layer is separated from
deeper waters by a layer of rapid density in-
crease, and hence of great stability, vertical
transfer of materials across this layer by eddy
diffusion must be much less rapid than is ver-
tical diffusion in the upper layer. Thus radio-
activity introduced at the surface by fallout may
remain in the upper layer for a long time and
be diluted by only a small part of the total
volume of the sea. Conversely, radioactive ma-
terials introduced below the pycnocline should
only slowly contaminate the upper layer where
they are most likely to endanger human ac-
tivities. However, organisms and particles of
sufficient density may readily cross the pyc-
nocline, due both to gravity and to vertical
migrations.
There are few observations which show di-
rectly the existence of cross-pycnocline exchange
on a local scale. In the western Pacific, both the
"Shunkotsu-Maru" survey (Japanese Fishery
Agency, 1955) and the "Taney" survey (U. S.
Atomic Energy Commission, 1956) reported
patches with significant concentrations of radio-
activity below the thermocline four months and
thirteen months, respectively, after mixed fis-
sion products were introduced at the surface in
the Marshall Island area. It is not known, how-
ever, whether this exchange was effected by
mixing processes, or by particulate or ecological
processes.
Exchange of properties between the near-
46
Atomic Radiation and Oceanography and Fisheries
surface and deeper waters is most likely to take
place under the following conditions:
1. In regions where the pycnocline is suffi-
ciently shallow to be eroded at the top by wind
stirring. In coastal waters the pycnocline is
usually shoaler than in midocean, and shallow
pycnoclines may also be found in high lati-
tudes, at the equator, along the north edge of
the Equatorial Countercurrent, and at the cen-
ter of strong cyclonic eddies. This process is
not effective to great depths, but could serve to
bring radioactive materials into the surface wa-
ters from the pycnocline layer.
2. In regions of up welling, where the pycno-
cline is relatively weak and where vertical cur-
rents not only carry water toward the surface
but also stir surface and deeper waters. It is
unlikely that water from depths of more than
500 meters is ever brought to the surface by
this process. Upwelling is common along west-
ern coasts of continents in the trade wind belt,
such as the coasts of Peru and Northern Africa.
In a simple sense, the persistent trade winds
blowing parallel to or offshore develop an off-
shore component of transport in the surface
waters, and deeper waters upwell to maintain
the volume continuity. Upwelling may also
occur along other coasts when the winds are
suitable. The process has been extensively stud-
ied along the coast of California where it is
not continuous because of the variability of the
winds (Sverdrup et al., 1942, p. 725). The
speed of coastal upwelling has been variously
estimated as 0.6 m/day (McEwen, 1934), 2.25
m/day (Saito, 1951) and 2.7 m/day (Hidaka,
1954) . However, since these estimates are theo-
retical mean values, they may differ significantly
from actual instantaneous upwelling rates.
Midocean upwelling, associated with diver-
gence of the surface currents, occurs in a band
along the equator in the eastern and central
Pacific Ocean (Cromwell, 1953). Observations
indicate that the effects of this upwelling ex-
tend to 50 meters in the eastern Pacific and to
100-150 meters in the central Pacific (Wooster
and Jennings, 1955). Similar but less pro-
nounced upwelling has been observed in the
equatorial Atlantic (Bohnecke, 1936) .
3. In regions of surface convergence, where
sinking waters may fill the depths of the ocean,
or may spread at intermediate depths according
to their density. In tropical and temperate
latitudes such sinking is confined to the surface
layer. In such regions mixing in the upper
layer may be facilitated but exchange across
the pycnocline probably is not, since the sinking
water tends to increase the density gradient in
the pycnocline.
In high latitudes, on the other hand, sinking
waters may reach great depths, and it is in
such regions that most of the intermediate and
deeper water masses of the ocean are formed.
The most extensive and pronounced of these
convergences is the Antarctic Convergence which
occurs at 50 to 60° S in a band around the entire
Antarctic Continent. The cold, low-salinity
water which sinks there forms an identifiable
water mass, the Antarctic Intermediate Water,
which spreads at depths between 800 and 1200
meters in all southern oceans. This water can
be identified everywhere in the South Atlantic
and extends across the equator as far as 22 °N
in the North Atlantic (Deacon, 1933; Iselin,
1936).
In the Irminger Sea, between Iceland and
Greenland, and in the Labrador Sea, warm high
salinity water of the Gulf Stream is partly mixed
with cold low-salinity water flowing out of the
Arctic Ocean. The resulting mixture may spread
in small quantities as Arctic Intermediate Water,
or when sufficiently dense may form the deep
and bottom water of the North Atlantic (the
possibility that the formation of this deep water
is not a continuous process is discussed later) .
Intermediate waters of the North Pacific are
probably formed in winter at the convergence
between the Kuroshio Extension and the Oya-
shio (Sverdrup et al, ch. 15). There is ap-
parently no deep or bottom water formed by
this process in the Pacific.
4. In regions where the density of surface
waters is so increased by evaporation, cooling
or freezing, that they sink to intermediate or
greater depths. Active formation of Antarctic
Bottom Water takes place in the Weddell Sea
due to the freezing of high salinity surface
waters. In the Mediterranean and Red Seas,
bottom water is formed by winter cooling of
waters whose salinity has been greatly increased
by evaporation. Mediterranean water flows out
into the North Atlantic at depths of 1000 to
1500 meters and can readily be identified near
Bermuda, 2500 miles from its source.
In summary, exchange between near-surface
and deeper waters takes place most commonly
(1) in high latitudes, (2) along the equator.
Chapter 4
Transport and Dispersal
47
and (3) in coastal regions, particularly along
the western coasts of continents. Conversely,
such exchange is least likely in temperate and
tropical latitudes in the vast central regions
of the northern and southern oceans.
Exchange betiveen the open sea and coastal areas
In coastal areas or enclosed basins where
precipitation exceeds evaporation, there is a
seaward surface drift of diluted water and a
landward subsurface drift of water derived
from the open sea. If radioactive materials
were released in such a coastal area, the ma-
terial which remained in the surface layer would
be carried seaward, but the part of the material
which mixed or settled to the deeper water
would move toward shore and the estuaries of
rivers. Conversely, if radioisotopes were lib-
erated in the open sea, some would eventually
be carried inshore as a result of the coastal and
estuarine circulation.
It is clear that the ultimate distribution in
coastal areas of radioactive materials added to
the sea would depend on the location of the
release, the vertical distribution of radioactivity
and density in the area of release, the length
of time required for the transport to the coastal
area or estuary, and the location of the source
sea water which provides for the counter drift.
The number of variables involved makes it
difficult to discuss the effects in general terms,
but it is worthwhile to note that the circulation
in coastal areas is rapid, and water bathing the
North Atlantic beaches is not uncommonly 90
per cent sea water even off large rivers such as
the Hudson and Delaware.
An idea of the lengths of time involved in
the coastal circulation can be obtained from the
mean age of waters in various parts of the At-
lantic seacoast. Such mean ages are computed
from the volume of water contained in the
region and the estimated transport of water
through the region. The waters of the con-
tinental shelf from Cape Hatteras to Cape Cod
have a mean age of about 2\ years, those of
the Bay of Fundy about 3 months, and those of
Delaware Bay from the ocean to the height of
tide about 3-4 months (Ketchum and Keen,
1953, 1955). The source sea water for all of
these circulations is the "slope water" which
is formed between the Gulf Stream and the
edge of the continental shelf.
A few data are available for confined basins
and seas from which estimates of the mean
age of the water can be derived. In most cases,
however, the sources of water entering into the
circulation are uncertain, and it should be em-
phasized that in all cases some of the waters
within the basin will be older or younger than
the mean age.
The source waters of the Florida Current
are funnelled through the Caribbean Sea. The
mass transport is 26 million cubic meters a
second (Sverdrup et al., 1942, p. 638), so that
this current carries annually a volume of water
equivalent to one-sixth of the total volume of
the Caribbean. However, there is evidence that
the renewal of the deep water of the Caribbean
proceeds at a much slower rate than the six
year mean age that this ratio implies. Wor-
thington (1955) has calculated, on the basis of
loss of oxygen from this deep water during the
last 30 years, that the age of the deep water
in the various parts of the Caribbean may range
from 93-142 years. The mean age of the
waters above 2000 meters would be reduced to
about 5 years if the deepest \ of the volume
of the basin is isolated from the present
circulation.
The same current passes through the Yucatan
channel into the Gulf of Mexico, before emerg-
ing as the Florida Current. No estimate of the
mean age of the waters of the Gulf of Mexico
is possible, however, since the current data in
the Gulf indicate an anticyclonic eddy in the
western portion, and suggest that the waters
of the Gulf of Mexico are drawn into the
Florida Current to only a slight extent (Die-
trich, 1939, Sverdrup et al., 1942, p. 642).
The Black Sea probably contains the most
isolated and the oldest deep water to be found
anywhere in the oceans. Precipitation and run-
off exceed evaporation, and the surface waters
are dilute (salinities less than 18 per cent) and
isolated from the deep water by an intense
density gradient. The deep waters are anaero-
bic; hydrogen sulfide reaches large concentra-
tions below about 200 meters. The sill at the
Bosporus is only 90 meters below the surface
so that this deeper water is isolated from the
more rapid surface circulation. The inflow of
sea water is so small that it would take about
2500 years to replace the deep water in the
basin (Sverdrup et al., 1942, p. 651). The
mean replacement time for the surface layers
48
Atomic Radiation and Oceanography and Fisheries
to a depth of 200 meters is equivalent to about
200 years. Gololobov (1949) has computed
the mean age of the deep water on the basis of
the annual contribution of phosphorus in the
river inflow and the quantity accumulated in
the depths. This computation indicates an
accumulation time of 5600 years.
The Arctic Basin receives its major inflow
north of Scotland and a much smaller inflow
through the Bering Strait. Additional sources
are from the river runoff and excess of precipi-
tation over evaporation. The outflow is pri-
marily through the Denmark Strait (Sverdrup
et al., 1942, p. 655). These flows would pro-
vide a volume equal to that of the Arctic Ocean
in about 160 years. The Arctic is also stratified
because of the addition of fresh water from
rivers and melting ice, and it is not known how
isolated some of the waters in the deeper basins
may be. However, recent analyses have shown
that the deeper water in the Arctic Ocean is
far from anaerobic, so that it seems unlikely
that this water can be considered as isolated
from the circulation.
The Mediterranean is a basin in which
evaporation exceeds precipitation and runoff^.
Through the Strait of Gibralter there is an
inflow of oceanic surface water and a sub-
surface outflow of high salinity Mediterranean
water. The exchange is sufficiently rapid to
replace the entire Mediterranean in about 75
years (Sverdrup et al., 1942, p. 647). The
Mediterranean is divided into eastern and west-
ern basins by a 500-meter sill between Sicily
and Tunisia, and it is not know to what extent
the deep waters of these basins are involved
in the over-all exchange.
Deep circulation
Most of our present knowledge of the inter-
mediate and deep circulation (see Sverdrup
et al., 1942, ch. 15) has been obtained in-
directly from the observed distribution of prop-
erties. The general uniformity of temperature
and dissolved substances in deep water suggests
that deep currents are very slow, perhaps at
most a few centimeters per second. But deep
currents cannot be computed by the geostrophic
method because only relative velocities can be
thus obtained. Furthermore, small errors in
the measurement of salinity or temperature
produce uncertainties in velocity of the same
magnitude as the currents being computed. The
direction of movement in the deep and bottom
water has been deduced from the observed
distribution of properties such as salinity and
potential temperature, but little can be learned
about current speeds from such observations.
Existing direct measurements of subsurface
currents have been summarized by Bowden
(1954). Such measurements have been made
since the time of the CHALLENGER Expedi-
tion (1873-76), but because of practical diffi-
culties (such as the problem in the open sea
of referring observations to a fixed frame of
reference) they have taught us little about the
deep oceanic circulation. The few successful
measurements at depths greater than 1000 me-
ters reported by Bowden showed mean speeds
ranging from "negligible" to about 13 cm/sec.
At nearly all stations and depths at which
current measurements have been made, semi-
diurnal tidal currents of the order of 10 cm/sec.
have been recorded.
Recently measurements of subsurface currents
have been made in the North Atlantic by track-
ing for three days a neutral-buoyant float sta-
bilized at a given depth (Swallow, 1955 and
unpublished). These measurements show small
resultant speeds (1.7 to 9.1 cm/sec or 0.8 to
4.2 miles/day at depths from 600 to 1900
meters), tidal components of about 10 cm/sec,
and in two successive three-day measurements
at 1900 meters, a change in direction of 124°.
Thus it seems likely that motion below the
pycnocline is characterized by more variation,
periodic or otherwise, than previously supposed
and indeed that the mean drift may represent
only a small part of the total motion.
Little is known about the nature and extent
of lateral and vertical mixing in the deep sea.
It is generally believed, however, that flow and
mixing take place along surfaces of constant
potential density (isentropic surfaces) and that
below the upper layer vertical mixing is very
slow except near coastlines and areas where
upwelling may occur (Montgomery, 1938). An
observation supporting this belief was reported
by Revelle, et al. (1955). Introduction of
mixed fission products below the pycnocline led
to the formation of a lamina of high radio-
activity about one meter thick and 100 or more
square kilometers in area. The radioactive water
apparently spread out along an isentropic sur-
face and resisted destruction by vertical mixing
for at least three days.
Chapter 4
Transport and Dispersal
49
Age of intermediate and deep waters
It is generally accepted that intermediate and
deep waters in most parts of the oceans acquired
their characteristics while at or near the surface.
Thus the low temperature and relatively high
oxygen content of deep water can only be ex-
plained by assuming an exchange between deep
and surface waters. The problem of the dis-
posal of radioactive wastes in the deep sea has
stimulated the oceanographer's natural curiosity
as to the rate of this exchange.
The North Atlantic receives surface waters
from the South Atlantic and loses deep water
to the South Atlantic. Assuming a surface flow
from the South to the North Atlantic of 6
million cubic meters per second (Sverdrup
et al., 1942, p. 685), and considering only
the upper kilometer of the North Atlantic to
be affected, the mean replacement time is about
140 years. The gyral in the North Atlantic,
which includes the Gulf Stream, carries about
ten times the volume of water exchanged be-
tween the South and North Atlantic, so that
the mean circulation time is only about one-
tenth the replacement time.
This surface exchange between the North and
South Atlantic is balanced by a deep current
from North to South. The mean displacement
time for the deep water of the North Atlantic
(2000-4000 meters) is calculated as about 250
years. This time is in reasonable agreement
with more recent estimates of the age of the
deep water discussed below.
Between these surface and deep layers are
the intermediate waters which appear to circu-
late even more rapidly. Deacon (1933) calcu-
lated rapid rates of northward flow of the
Antarctic intermediate water in the South At-
lantic, based upon alternate maxima and minima
in the concentrations of oxygen in the oxygen
minimum layer. These were interpreted as rep-
resenting annual cycles when the waters were
formed at the surface. He estimated a transit
time of about 4^ years between the Antarctic
convergence and the equator. Seiwell (1934)
has similarly computed rapid flows and a mean
transport time of 7-8 years for the drift of the
oxygen minimum layer of the North Atlantic
Ocean. Deacon's and Seiwell's interpretations
have been questioned (see Riley, 1951, p. 77)
on various grounds. However, their rates of
flow agree with direct current measurements
at comparable depths (see earlier) which also
indicate rapid rates of circulation.
The deep outflow from the Mediterranean
sinks from sill depth to 1000-1500 meters in
the North Atlantic Ocean. This water, although
much diluted by Atlantic water, is characterized
by relatively high salinity and temperature, and
spreads out in a sheet which may be identified
in most of the temperate North Atlantic, and
some spreads into the South Atlantic. It can be
readily identified near Bermuda, 2500 miles
from its source. Iselin (1936) computed that
sufficient excess salt would be produced by the
Mediterranean outflow to produce the observed
anomaly in 12-15 years. He pointed out that
the actual replacement would be more rapid
because he neglected admixture of Atlantic
water in the immediate vicinity of the Straits
of Gibraltar. Defant (1955) has evaluated the
mixing processes involved in dissipating the
Mediterranean water within the Atlantic Ocean,
and has concluded that the total accumulation
in the Atlantic Ocean represents the contribu-
tion resulting from six years of flow through
the Straits of Gibraltar. The rapid dissipation
of this large water mass at mid depths suggests
a more rapid circulation than had been gen-
erally accepted for intermediate waters.
During recent years other lines of investiga-
tion have led to the belief that the overturn of
water in the ocean basin takes place in less
than a thousand years and probably in 200
years or less. Evidence supporting this belief
follows. (Carbon-l4 and carbon dioxide ex-
change estimations are discussed in greater
detail by Craig elsewhere in this report.)
1. Heat fiow measurements: Measurements re-
ported by Revelle and Maxwell (1952) have
shown a heat flow through the floor of the
Pacific Ocean of 1.2x10"'' calories per square
centimeter per second, or 38 calories per square
centimeter per year. If not dissipated by circu-
lation and mixing, this heat flow would lead to
warming of the deep and bottom water during
its passage from the Antarctic to the equator.
From considerations of meridional circulation,
observed temperature gradients and mixing in
the deep sea, Revelle and Maxwell estimate
that the deep water is replenished in less than
1000 years.
2. Secular change of oxygen: Worthington
(1954) has shown that the North Atlantic
Deep Water has suffered a loss of dissolved
50
Atomic Radiatio7j and Oceanography and Fisheries
oxygen of about 0.3 ml/L over the last twenty
years. Assuming a steady rate of attrition he
computes that the date at which this water was
saturated, presumably while at the surface, was
about 1810. A further study (Worthington,
1955) suggests that the Caribbean Deep Water
was formed at the same time. Thus it seems
possible that formation of the North Atlantic
Deep Water, which composes about half of
the contents of the Atlantic, is not continuous
but sporadic.
3. Carbon- 14 dating: In recent years the tech-
niques of carbon-l4 age determination have
been applied to deep sea water samples. The
most reliable measurements (Rubin, unpub-
lished), of samples from east of the Lesser
Antilles, show the carbon at 1750 meters to be
about 200 years older than the surface carbon.
Present estimates of the age of deep waters
are based primarily on measurements in the
North Atlantic and on geochemical calculations
for the entire world ocean. That the deep cir-
culation of the Pacific is significantly slower
than that of the Atlantic is suggested by the
apparent absence of regions of deep and bottom
water formation in the Pacific and the rela-
tively high nutrient salt content and low dis-
solved oxygen content of deep Pacific waters.
In order to determine whether the deep waters
of the Pacific would provide a longer period of
isolation for radioactive wastes than elsewhere,
deep Pacific oceanographic data must be care-
fully scrutinized.
REFERENCES
BoHNECKE, G. 1936. Atlas: Temperatur, Salz-
gehalt und Diclite an der Oberflache des
Atlantischen Ozeans. Deutsche Atlantische
Exped. Meteor, 1925-27, Wiss. Erg. 5:
vii + 76 pp.
BowDEN, K. F. 1954. The direct measurement
of subsurface currents in the oceans. Deep-
Sea Res. 2:33-47.
Cromwell, T. 1953. Circulation in a meri-
dional plane in the central equatorial Pa-
cific. /. Marine Res. 12:196-213.
Deacon, G. E. R. 1933. A general account
of the hydrology of the South Atlantic
Ocean. Discovery Rep. 7 :l71-2?>8.
Defant, a. 1955. Die Ausbreitung des Mit-
telmeerwassers im Nordatlantischen Ozean.
Pap. Mar. Biol, and Oceanogr., Deep-Sea
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Deutschen Seewarte. 1942. Weltkarte
zur Ubersicht der Meeresstromungen.
Deutschen Seewarte No. 2802.
Dietrich, G. 1939. Das Amerikansiche Mit-
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Zeitschr., 108-130.
ECKART, C. 1948. An analysis of the stirring
and mixing processes in incompressible
fluids. /. Marine Res. 7:265-275.
Francis, J. R. D., and H. Stommel. 1953.
How much does a gale mix the surface
layers of the ocean. Quart, f. Roy. Me-
teorol. Soc. 79:534-536.
Fuglister, F. C. 1951. Multiple currents in
the Gulf Stream System. Tellus 3(4):
230-233.
Gololobov, Y. K. 1949. Contribution to the
problem of determining the age of the
present stage of the Black Sea (in Rus-
sian). Dokl. Akad. Nauk SSSR 66:451-
454.
HiDAKA, K. 1954. A contribution to the theory
of upwelling and coastal currents. Trans.
Am. Geophys. Union 35(3) :431-444.
IsELiN, C. O'D. 1936. A study of the circula-
tion of the western North Atlantic. Pap.
Rhys. Oceanogr. Meteorol. 4(4): 1-101.
Japanese Fishery Agency. 1955. Report on
the investigations of the effects of radia-
tion in the Bikini region. Res. Dept.,
Japanese Fishery Agency, Tokyo, 191 p.
Ketchum, B. H., and W. L. Ford. 1952.
Rate of dispersion in the wake of a barge
at sea. Trans. Am. Geophys. Union 33
(5) : 680-684.
Ketchum, B. H., and D. J. Keen. 1953. The
exchanges of fresh and salt waters in the
Bay of Fundy and in Passamaquoddy Bay.
/. ¥ish. Res. Bd. Can. 10:97-124.
1955. The accumulation of river water over
the continental shelf between Cape Cod
and Chesapeake Bay. Pap. Mar. Biol, and
Oceanogr., Deep-Sea Res., suppl. to vol. 3:
346-357.
KoENUMA, K. 1939. On the hydrography of
south-western part of the North Pacific
and the Kuroshio. Kobe Imper. Marine
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McEwEN, G. F. 1934. Rate of upwelling in
the region of San Diego computed from
Chapter 4
Transport and Dispersal
51
serial temperatures. Fifth Pac. Set. Congr.,
Toronto 3:1763.
MiYAKE, Y., Y. SuGiURA, and K. Kameda,
1955. On the distribution of radioactivity
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Heat flow through the floor on the eastern
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SvERDRUP, H. U., M. W. Johnson, and R. H.
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1947b. Atlas of surface currents, northeast-
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Chapter 5
THE EFFECTS OF THE ECOLOGICAL SYSTEM ON THE TRANSPORT OF
ELEMENTS IN THE SEA '
BOSTWICK H. Ketchum, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts
Some elements may be profoundly influenced
by the biological cycle and their resulting dis-
tribution in the sea may be quite different from
the distribution of elements that are affected
only by the circulation of the water. Numer-
ous examples of the modification of distribution
by biological activities could be given but it
may suffice to review briefly the vertical distri-
bution of phosphorus in the ocean.
The photosynthetic fixation of carbon is lim-
ited to the surface hundred meters or less of
the sea by the penetration of light, and the
plant nutrients, including phosphorus, are as-
similated there. The surface concentration of
these elements may be reduced to virtually
zero. Below the photosynthetic zone, the con-
centrations of these nutrients increase, reaching
maximum values at depths of 200 to 1000
meters, the actual depth depending upon loca-
tion and the oceanic circulation. These maxi-
mum concentrations are produced by two proc-
esses. The water at intermediate depths is
formed by cooling at high latitudes in the
ocean, where it sinks and spreads out. At the
time of sinking, it contains some inorganic
phosphorus and organic matter which is de-
composed, liberating the plant nutrients and
decreasing the oxygen content. Additions to
the organic matter from the surface waters
occur everywhere, increasing the nutrient maxi-
mum concentration and decreasing the oxygen
minimum. Below the nutrient maximum-oxygen
minimum layer the concentration of phosphorus
decreases again reaching values which are gen-
erally constant and uniform from a depth of
about 1500 meters to the bottom (Redfield,
1942).
The general patterns of distribution of the
elements important in plankton growth on an
ocean-wide scale are thus quite different from
1 Contribution No. 871 from the Woods Hole
Oceanographic Institution.
the pattern of distribution of the major ele-
ments. The processes which must be considered
in order to evaluate biological effects on the
ultimate distribution of radioisotope wastes or
contaminants in the sea include (1) the assimi-
lation or adsorption of the elements by the bio-
logical populations, (2) the effects of gravity,
(3) vertical migrations, (4) horizontal migra-
tions, and (5) the effects of stationary popula-
tions in flowing systems.
It has been shown in another section of this
report that biological populations may concen-
trate by several orders of magnitude various
elements and their radioisotopes. To evaluate
the possible significance of this in the oceans, it
is necessary to determine the quantity of living
material present (the biomass) and the rate of
production of the populations of the ecological
system. The biomass, when combined with the
known concentration factor, will indicate how
much of an element in the water may be com-
bined in the living organisms. The most active
concentration of elements may occur during the
rapid growth of populations; consequently it
is also essential to know the rate of production
of the various populations involved. A few data
on both the biomass and the rate of production
of various populations in the sea are given in
Tables 1 and 2.
The biomass figures indicate that concentra-
tion factors of 12,500 or more would be re-
quired, under static conditions, to incorporate
half of an element in a cubic meter of water
within the ecological system even in the high
concentrations of living material found in red-
tide blooms. However, the biological popula-
tions are not static; those movements which are
independent of the motion of the water can,
by repetition, transport larger proportions of
elements than is indicated by static equilibrium
conditions. The productivity values in Table 2
indicate that several times the standing crop
of phytoplankton is produced annually. Both
52
Chapter 5
Ecological Systems and Transport
53
TABLE 1 Estimates of Biomass of Marine Populations. All Values Have Been Converted to
Volume (Wet Weight) Per Cubic Meter (Parts Per Million)
Population
Phytoplankton .
Zooplankton
cc/m'
10
25
41
18.2
1.2
0.3
0.08 — 1.0
0.08 — 0.8
0.006 — 0.09
1.0
0.042
0.055
0.124
a. Complete utilization of maximum phosphorus concentrations; conversion P = 0.5 per cent of wet
weight.
b. Ketchum and Keen, 1948, 17-21, Table 1. Conversion as in a.
c. Riley, Stommel and Bumpus, 1949, Table VI; conversion C^IO per cent wet weight.
d. Redfield, 1941, drained volumes, vertical tows, assumed mean depth 100 meters.
e. Riley, et al., 1949, Table V, displacement weight.
f. Unpublished data, W. H. O. I., surface tows at night, drained volumes.
g. Unpublished data, S. I. O., oblique tows 200-300 meters to surface, wet plankton volumes.
Location and character
.Maximum Atlantic
Maximum Pacific
Red Tide Blooms
Long Island Sound
Coastal Water
Sargasso Sea
. Gulf of Maine
Coastal Water
Sargasso Sea
N. African Upwelling
Eastern North Pacific
Eastern Tropical Pacific
Peru Current
Source
a
a
b
c
c
c
d
e
f,e
f
g
g
g
the depth of the photosysthetic zone and the
production rate at various depths, are variable,
thus the values for production cannot be re-
duced without excess over-simphfication to a
volume basis which would permit direct com-
parison with Table 1. However, Riley's (1941)
maximum value for the standing crop of phyto-
TABLE 2 Estimates of the Productivity of
Marine Phytoplankton Populations
Location and gC/m"/ cc/m"/
character Source year year i
Sargasso Sea (Atlan-
tic) a 18 180
Coastal Areas (Atlan-
tic) a 1100 11000
Open Ocean (Pacific) . . a 50 500
Equatorial Divergence
(Pacific) a 140 l400
Coastal Areas (Pacific) . a 200 2000
Oceanic Mean a 55 550
Long Island Sound
min b 95 950
max 1000 10000
N. Atlantic 3°-13°N. . b 278 2780
Oceanic Mean c 340 ± 220 1200-5600
a. Steemann Nielsen (1954). Carbon-l4 method.
This is given as gross production, but Ryther (1954)
suggests that it may be net (gross minus respiration)
production in nutrient poor areas.
b. Riley (194l). Gross production, oxygen method.
c. Riley (1944).
1 Conversion assuming one gram of carbon = 10 cc
of wet plankton.
plankton in Long Island Sound, 1.82 gC/m^,
showed a production of 0.187 gC/myday and
the annual production was twenty times as great
as the maximum standing crop observed at any
one time. Estimates of the growth of zooplank-
ton populations have given values ranging up
to 5 per cent of the standing crop per day.
It is a truism in ecology that the total quan-
tity of living material which can be produced
decreases as the trophic level of the organisms
considered increases. In some ecological sys-
tems the biomass reflects this progression, i.e.,
at any one time there will be a larger standing
crop of plants than of herbivores and the stand-
ing crop becomes progressively smaller as one
goes through the various higher steps of the
food web. In the oceans, however, this is not
necessarily true. It is common to find rather
high concentrations of the herbivorous zoo-
plankton when phytoplankton are scarce. Large
populations of herbivores will quickly decimate
the plants on which they feed. A balance may
be maintained as a result of the different lengths
of the life cycle of the various parts of the
food web. A population of phytoplankton can
double in a period of time ranging from hours
to days, whereas the life cycles of zooplankton
are more commonly measured in terms of weeks
or months and the life cycles of the higher
elements of the food web, such as fish, are
54
Atomic Radiation and Oceanography and Fisheries
measured in terms of seasons or years. A com-
paratively small population of phytoplankton
doubling rapidly can provide the energy and
nutrients of an equivalent or even larger animal
population which is increasing more slowly.
The size of various populations and their
rate of production in the English Channel has
been evaluated by Harvey (1950) and his re-
sults are given in Table 3. These illustrate the
above conclusions, since the average biomass of
animals exceed that of the plants, but the rate
TABLE 3 Average Quantity, Throughout the
Year, of Plants and Animals Below Unit
Area of Sea Surface in the English
Channel i
Dry wt of organic matter
Standing crop Production
Organism g-/m^ g./mVday
Phytoplankton 4.00 0.4-0.5
Zooplankton 1.50 0.1500
Pelagic Fish 1.80 0.0016 2
Bacteria 0.04 —
Demersal Fish 1.25 0.0010
Bottom Fauna 17.00 0.0300 ^
Bottom Bacteria 0.10 —
1 From Harvey (1950), depth equals 70 meters.
2 Based on estimated mortality of 30 per cent per
annum.
3 Based on estimated mortality of 60 per cent per
annum.
of production of the plants exceeds that of the
animal populations.
The plankton organisms in the open sea pro-
vide by far the largest quantity of living ma-
terial and by even more the largest organic
absorptive surface. Those radioisotopes which
are adsorbed will become bound to the organ-
isms, and they are as subject to the effects of
gravitation and migration as if they had been
assimilated and utilized.
Gravity affects the organisms in a population
and can thus modify the distribution of ele-
ments which become incorporated in the bio-
logical cycle. Ultimately only two fates await
most of the plankton which grows in the sur-
face layers. It may be eaten by the herbivores
or it may sink out of the illuminated zone and
decompose at greater depths. If the plankton
is eaten by a herbivore, a proportion of the
organic matter is incorporated into the herbivore
body but an even larger proportion is returned
to the water as excretion or faecal pellets. The
excretions may be present in the water inhabited
by the plankton and reused in situ. The faecal
pellets settle into the deeper water where they
decompose. Gravity thus imposes on elements
which become incorporated in the biological
system a modification of the distribution which
would be produced by movements of the water
alone, since they tend to accumulate at some
intermediate depth in the water column, or on
the bottom.
One of the unsolved problems of marine
biology is the definition of the proportion of
organic matter which is decomposed by the time
the particulate material sinks to various depths.
This problem must be solved before an evalua-
tion of the biological effects on the distribution
of radioisotope contamination of the seas can
be made. It may be worthwhile to summarize
some of the present thinking on this problem.
In the first place, everywhere that samples
have been taken in the deep sea, living organ-
isms have been found. Since we know of no
mechanism other than photosynthesis at the sur-
face which can provide the organic material
necessary to support these populations, it is
clear that some of the surface produced material
must reach all depths of the ocean. It may be
argued by some that the bacterial chemosyn-
thetic processes are a source of fixed carbon
which has not been considered, but the condi-
tions in the deep sea are not suitable for the
formation of organic matter by any of these
processes.
The presence of the nutrient maximum-oxy-
gen minimum layer at intermediate depths in
the sea has led to the conclusion that most of
the organic matter formed at the surface must
be oxidized by the time it has sunk to a depth
of 1000 meters (Redfield, 1942). Analyses of
organic phosphorus in the equatorial Atlantic
Ocean showed considerable amounts in the
waters above 1000 meters, but none at greater
depths (Ketchum, Corwin, and Keen, 1955).
There is no present evaluation of the quantity
of organic carbon which can sink to greater
depths, nor is it possible to evaluate whether
this quantity would be sufficient to support the
known populations of archibenthic organisms.
These two extremes thus define the dilemma.
Namely that some organic matter must reach
the great depths, but, at the same time, most of
the decomposition appears to occur above a
depth of 1000 meters.
The secular change of oxygen in the deep
Chapter 5
Ecological Systems and Transport
55
sea which has been found by Worthington
(1954) in the North Atlantic, provides one
means of computing the total quantity of or-
ganic matter required. Worthington observed
a decrease of 0.3 milliliters of oxygen per liter
in thirty years at depths between 2500 meters
and the bottom. In the Atlantic Ocean this
corresponds to an average thickness of 1500
meters and the total quantity of organic matter
required to produce this change in oxygen is
equivalent to the decomposition of 8 grams of
organic carbon per square meter per year in
this layer. This quantity of organic matter is
nearly 15 per cent of the annual mean produc-
tion according to Steemann Nielsen (1954)
and from 1.4 to 7 per cent of the mean sug-
gested by Riley (1944). Part of the secular
change in oxygen may have been produced by
eddy diffusion into the oxygen minimum layer,
which would reduce the quantity of organic
carbon reaching greater depths.
The effects of gravity may be accentuated
when the surface currents are opposed to the
currents in the deeper layers. This type of
circulation pattern is very common in estuaries,
on continental shelves, and in those areas where
offshore winds produce upwelling of the deeper
waters. In all of these cases the nutrient rich
deep water is carried inshore in a sub-surface
drift, and brought to the surface by upwelling
or vertical mixing. The nutrients are assimilated
by the plankton in the surface layers and are
carried offshore in the surface current. "When
the organisms sink, they again reach the on-
shore sub-surface current where they decompose
liberating more nutrients into water which is
already relatively rich. Thus the elements in-
volved in biological processes follow a different
cycle from the circulation of the water and
this cycle leads to an accumulation of elements
greater than can be found in either of the source
waters (Strom, 1936; Hulburt, In press).
Nutrient elements are commonly concentrated
by this type of mechanism in fjords. Where the
deepest water is relatively stagnant and isolated
from the intermediate and surface layers, con-
siderable concentrations of organic derivatives
can be developed. In the Norwegian fjords
with a relatively shallow sill, for example,
anaerobic conditions may be produced in the
bottom water and the nutrients are five to ten
times as concentrated as in either of the source
waters (Strom, 1936). In the Black Sea the
deep water is isolated from the surface by a
strong density gradient and its average age has
been estimated at 2500-5000 years (Sverdrup,
Johnson and Fleming, 1942, p. 651). Very
large accumulations of organic derivatives are
found in this deep water. (Gololobov, 1949.)
Opposed currents can, however, work in the
opposite way and lead to a decrease in the
concentration of elements involved in the bio-
logical cycle. The classic example of this type
of circulation is the Mediterranean, where the
nutrients available for plant growth are less
than half of the concentration available in the
adjacent parts of the Atlantic. In the Mediter-
ranean the supply comes from the surface wa-
ters of the North Atlantic which are already
impoverished by plant growth. Since evapora-
tion exceeds precipitation in the Mediterranean
the water becomes more saline, sinks and is
lost as a deep outflow over the sill at Gibraltar
(Thomsen, 1931). The accumulation of ele-
ments in sinking organisms transfers these ele-
ments from the inflowing surface water to the
outflowing deep water. They are eventually
lost from the Mediterranean. A similar process
apparently applies to the entire North Atlantic.
There is a large inflow of South Atlantic sur-
face water which contains low concentrations
of elements involved in the ecological cycle.
The outflow from the North Atlantic required
to balance the water budget occurs at depths
and this water contains considerable quantities
of the elements which had been returned to the
water (Sverdrup et al., 1942).
In summary the various peculiarities of dis-
tribution which can be attributed to gravitational
effects on the ecological cycle are therefore
(1) the accumulation of elements at inter-
mediate depths as a result of sinking and de-
composition, (2) the concentration of elements
in areas of opposed flow where the deep water
is brought to the surface by upwelling or ver-
tical mixing and (3) the impoverishment of
areas where the supply of water is from the
surface and the loss from greater depths.
In addition to the passive gravitational effects
on organisms, animal plankton forms exhibit
vertical migrations. A considerable literature
has developed in this field over the last ten
years, but the effects of these vertical migrations
on the distribution of elements has not been
studied directly and must be inferred from our
knowledge of the ecological system.
56
Atomic Radiation and Oceanography and Fisheries
Historically, a few studies of the vertical
migration of zooplankton had been made prior
to the war. Great impetus was given these
studies when a false bottom was repeatedly
observed on echo sounding recorders (Dietz,
1948; Hersey and Moore, 1948). This has
been called the scattering layer. Although there
is still controversy as to which organisms are
the principal scatterers in the sea, it has been
established that one or more layers are com-
monly found which migrate vertically over a
depth of as much as 800 meters, being at or
near the surface at night and at great depths
at mid-day.
No observations of the changes of elements
involved in the biological cycle which may be
associated with vertical migrations have been
made. Most of our analytical techniques are
too insensitive to detect the day to day changes
which might be expected in biologically active
elements if our present evaluation of the density
of the populations and their respiration and
excretion rates is correct. It is known, however,
that direct assimilation of some elements is
possible by invertebrate forms and vertical trans-
port of radioisotopes might be expected to re-
sult. Indeed, the transport of radioisotopes
might prove an excellent tool for the study
of vertical migrations if a source were provided
at one depth within the range of the migration.
Ecologically the following effects might be
expected as a result of vertical migration. The
zooplankton are certainly in the area of the
most dense concentration of their food, the
phytoplankton, when they are at the surface at
night. During the hours of darkness they may
therefore be expected to consume the living
material in the water, and some of this, at least,
would be excreted or passed as faecal pellets at
depth in the day time. This process would thus
augment the effects of gravity on those elements
incorporated in the biological system. There
is also evidence that the zooplankton can as-
similate dissolved elements from sea water. If
elements were assimilated at depth they might
be excreted or exchanged near the surface and
thus directly modify the vertical distribution
in the sea.
It should not be neglected that larger or-
ganisms can certainly migrate vertically over
greater distances than we have discussed above.
Certainly whales, tuna and sharks, and pre-
sumably the smaller forms upon which they
feed are known to go to considerable depths
in the ocean. Quantitatively, of course, these
members high on the food chain are propor-
tionally small compared to the plankton or-
ganisms. However, their effects on vertical dis-
tribution of materials may not be negligible
over periods of several decades.
Horizontal migrations of organisms may also
result in the transport of material involved in
the biological cycle and are also independent
of the currents of the ocean. Here again man
does not know enough to assess these quantita-
tively, but their possible effects should not be
ignored.
The migrations of pelagic fishes may be of
considerable interest in this regard. The salmon
for example reach maturity in the open sea,
then migrate in enormous numbers to coastal
areas to breed. Such a horizontal migration
could transport radioisotopes, since the salmon
could accumulate materials from large volumes
of the sea and, by their migration, concentrate
them many thousand-fold in the rivers and
estuaries.
Many other fish also exhibit extensive migra-
tions. Even though some of these do not enter
the rivers to breed, they may enter the areas
where they are available for commercial cap-
ture, thus becoming some of the food supply
of the nation. Unfortunately, in many of these
species we do not know the complete life his-
tory and most of our information concerning
their occurrences and migrations is obtained
only during the period of year when they are
caught. The Atlantic tuna, for example, are
caught in the early spring in the Caribbean and
off the Bahama Banks. As spring and summer
progresses they migrate northward along the
coast, and maximum catches occur in New
England in late summer and early fall. The
winter habitat and breeding area of these large
and important food fish is largely unknown,
though preliminary data suggest that they prac-
tically circumnavigate the North Atlantic Ocean
(Mather and Day, 1954). Similarly the mack-
erel catches are first concentrated in the south-
ern part of the Atlantic coastline in the late
spring and early summer. The large catches
off New England occur in August and Septem-
ber. This species breeds on the Atlantic con-
tinental shelf during its summer northward
migration (Sette, 1943, 1950).
Additional examples of mass migrations into
Chapter 5
Ecological Systems and Transport
57
the coastal regions are found in the Pacific
sardine and the North Atlantic herring. In all
of these cases materials assimilated at sea may
be concentrated in inshore waters as a result
of these migrations, which may cover thousands
of miles. Such migrations certainly make it
difficult to select any area in the oceans as being
sufficiently remote and isolated from human
interest to insure that the discharge of radio-
isotope wastes might not be transported into
those areas man is most interested in protecting.
It should, however, be pointed out that this is
a quantitative problem, and our knowledge is
not sufficiently detailed to permit evaluating
the quantity of radioisotopes which could be
transported in mass migrations of fish.
In addition to the movements of organisms
which are independent of the circulation of the
water resulting from gravity and vertical and
horizontal migrations, many populations remain
stationary in a flowing stream of water. The
organism is thus able to concentrate remarkably
the constituents of the water masses which pass
by. Harvey (1950) estimated, for example,
that the bottom population was nearly 70 per
cent of the total population at a station in the
English Channel (see Table 3) .
The most apparent of these stationary popu-
lations are those which live on or in the bottom.
Much of our knowledge concerning such popu-
lations is confined to those which occupy shal-
low waters such as the clams, the oysters, and
other economically important species. Stationary
populations may be exposed to and feed on
populations in many cubic miles of sea water
during the course of an active growing season.
Although most of our knowledge is confined
to shallow water forms, it is known that such
stationary populations are a main source of food
for many bottom-feeding commercial fishes. The
haddock and cod fisheries of New England and
the halibut fishery of the Pacific Coast, for
example, are ground fisheries. These impor-
tant species of fish feed on sedentary or sta-
tionary populations. Even in the great depths
of the ocean such sedentary populations have
been found wherever man has had the oppor-
tunity to search for them. Although little is
known of their location in the food web and
dynamics of the ocean, it seems certain that
they play a part.
The importance of such stationary popula-
tions is that they can concentrate enormously
the density of organic matter in those locations
suitable for their survival. In unique situations
they may concentrate by several orders of mag-
nitude the available organic matter in the ocean.
Less obvious stationary populations are plank-
tonic and unattached, and one would expect
them to be transported away from a given area
by the currents. It has been found in some
cases, however, that in spite of horizontal cur-
rents of considerable velocity, the centers of
some planktonic populations can remain rela-
tively stationary. Presumably there is a con-
stant drain from these populations as a result
of the currents which carry away some of the
organisms, but the rate of production of the
population is sufficient to maintain the popula-
tion in spite of this drain. Examples of such
populations are to be found in almost all estu-
aries which tend to maintain endemic species
different from those commonly found in the
adjacent sea (Ketchum, 1954; Bousfield, 1955).
Even in the open ocean similar stationary popu-
lations have been found (Redfield, 1939, 1940,
1941 ; Johnson and co-workers, unpublished
observations) . It is necessary to have a rate of
reproduction of the population as a whole suffi-
cient to balance the circulatory drain. This rapid
rate of reproduction will, of course, lead to the
concentration of materials from the v»'ater mass
moving past.
A special case of biological concentration of
materials which probably involves several of
the above phenomena is found in the "red
tide." It has been shown that the concentration
of total phosphorus in the colored water of
these dinoflagellate blooms is commonly ten to
twenty times as great as the concentration which
can be found in any of the adjacent waters
(Ketchum and Keen, 1948). Most of this
phosphorus is combined in the living cells, and
very little is present in the inorganic form.
One of the explanations for these high concen-
trations involves the accumulation of the organ-
isms at the surface because of their buoyancy,
and the subsequent further concentration of
the surface film by convergence of water masses
(Ryther, 1955). In the red tides which have
occurred in recent years off the west coast of
Florida, the organism involved, Gymnodinium
brev}s, produces a toxin which is lethal to the
fish and other organisms in the water, and vast
numbers of fish have been killed as a result
of these dinoflagellate blooms (Gunter, et al..
58
Atomic Radiation and Oceanography and Fisheries
1948). Recent evidence indicates that the or-
ganisms are almost always present in the water
(Collier, A., unpublished), but in such low
concentrations that there is no marked fish
mortality. It is only after the concentration
produced by the biological and hydrographic
system that mortalities result.
In evaluating the discharge of radioisotope
wastes at sea, the factor of safety must be
sufficient so that safe levels of radioactivity can
be maintained, even after the various mecha-
nisms of biological accumulation.
REFERENCES
BousFiELD, E. L. 1955. Ecological control of
the occurrence of barnacles in the Mira-
michi Estuary. Nat. Mus. Canada Bull.
No. 137, Biol. Ser. No. 46, pp. 1-69.
DiETZ, R. S. 1948. Deep scattering layer in
the Pacific and Antarctic oceans. /. Mar.
Res. 7:430-442.
GOLOLOBOV, Y. K. 1949. (Contribution to the
problem of determining the age of the
present stage of the Black Sea) in Russian.
Dokl. Akad. Nauk SSSR. 66:451-454.
GuNTER, G., R. H. Williams, C. C. Davis,
and F. G. Walton Smith. 1948. Cata-
strophic mass mortality of marine animals
and coincident phytoplankton bloom on
the west coast of Florida, November, 1946
to August, 1947. Ecol. Monogr. 18:309-
324.
Harvey, H. W. 1950. On the production of
living organic matter in the sea oflF Ply-
mouth. /. Mar. Biol. Assoc. U. K. 29:
97-137.
Hersey, J. B., and H. B. Moore. 1948. Prog-
ress report on scattering layer observations
in the Atlantic Ocean. Trans. Amer.
Geophys. Union. 29:341-354.
HuLBURT, E. M. In press. The distribution
of phosphorus in Great Pond, Massachu-
setts. (Submitted to /. Mar. Res.)
Ketchum, B. H. 1954. Relation between cir-
culation and planktonic populations in
estuaries. Ecol. 35:191-200.
Ketchum, B. H., N. Corwin, and D. J. Keen.
1955. The significance of organic phos-
phorus determinations in ocean waters,
Deep-Sea Res. 2:172-181.
Ketchum, B. H., and D. J. Keen. 1948.
Unusual phosphorus concentrations in the
Florida "red tide" sea water. /. Mar. Res.
7:17-21.
Mather, F. J., Ill, and C. G. Day. 1954.
Observations of pelagic fishes of the tropi-
cal Atlantic. Copeia, 1954, no. 3:179-188.
Redfield, a. C. 1939. The history of a popu-
lation of Limacina retroversa during its
drift across the Gulf of Maine. Biol. Bull.
76:26-47.
1941. The effect of the circulation of water
on the distribution of the calanoid com-
munity in the Gulf of Maine. Biol. Bull.
80:86-110.
1942. The processes determining the con-
centration of oxygen, phosphate and other
organic derivatives within the depths of
the Atlantic Ocean. Pap. Phy. Oceanog.
Meteorol. 9:1-22.
Redfield, A. C, and A. Beale. 1940. Fac-
tors determining the populations of chae-
tognaths in the Gulf of Maine. Biol. Bull.
79:459-487.
Riley, G. A. 1941. Plankton studies. III.
Long Island Sound. Bingham Oceanog.
Coll. Bull. 7(3): 1-93.
1941a. Plankton studies. V. Regional sum-
mary. /, Mar. Res. 4:162-171.
1944. The carbon metabolism and photo-
synthetic efficiency of the earth as a whole.
Amer. Sci. 32:129-134.
Riley, G. A., H. Stommel, and D. F. Bumpus.
1949. Quantitative ecology of the plank-
ton of the western North Atlantic. Bing-
ham Oceanog. Coll. Bull. 12:1-169.
Ryther, J. H. 1954. The ratio of photosyn-
thesis to respiration in marine plankton
algae. Deep-Sea Res. 2:134-139.
1955. Ecology of autotrophic marine dino-
flagellates with reference to red water con-
ditions. Luminescence of Biological Sys
tems: 387-414.
Sette, O. E. 1943. Biology of the Atlantic
mackerel {Scomber scombrus) of North
America. Part I: Early life history. Fish.
Bull. 38:149-237.
Sette, O. E. 1950. Biology of the Atlantic
mackerel (Scomber scombrus) of North
America. Part II. Migrations and habits.
Fish. Bull. 51:251-358.
Chapter 5
Ecological Systems and Transport
59
Steemann Nielsen, E. 1954. On organic
production in the oceans. /. Con. Internal.
Explor. Mer. 19:309-328.
Strom, K. M. 1936. Land-locked waters. Hy-
drography and bottom deposits in badly
ventilated Norwegian Fjords with remarks
upon sedimentation under anaerobic condi-
tions. Norske Vidensk. Akad. 1. Mat.
Naturv. Klasse No. 7, 85 pp., Oslo.
SvERDRUP, H. U., M. W. Johnson, and R. H.
Fleming. 1942. The Oceans, their physics,
chemistry and general biology, x+1087
pp., Prentice-Hall, Inc., New York.
Thomsen,' H. 1931. Nitrate and phosphate
contents of Mediterranean water. Danish
Oceanog. Exped. 1908-1910. 3:14 pp.
WORTHINGTON, L. V. 1954. A preliminary
note on the time scales in North Atlantic
circulation. Deep-Sea Res. 1:244-251.
Chapter 6
PRECIPITATION OF FISSION PRODUCT ELEMENTS ON THE OCEAN
BOTTOM BY PHYSICAL, CHEMICAL, AND BIOLOGICAL PROCESSES
Dayton E. Carritt, The Johns Hopkins University
and
John H. Harley, Health and Safety Laboratory, U. S. Atomic Energy Commission
Introduction
It has been suggested that naturally occurring
processes will remove radioactive waste mate-
rials from solution or suspension in the oceans,
carrying them to the ocean floor where they will
be kept out of the human environment until
natural radioactive decay destroys them.
In this section we will attempt to define the
processes by which materials may be carried to
the bottom, to note the conditions under which
these several processes can be expected to op-
erate, and to assess the extent to which these
processes have been responsible for the removal
of activity to the bottom in cases where bottom
accumulation has been measured.
It should be noted that the deposition of fis-
sion products on the bottom has not been stud-
ied in such a way as to permit an evaluation of
the mechanisms responsible for the deposition
and retention of the activities. Measurements
of bottom-held activities have been made pri-
marily to estimate the total activity. We will
discuss later the kind of information that might
be obtained in connection with weapons tests
and large-scale tracer experiments, and which
is needed for a better evaluation of the extent
to which deposition processes remove fission
product elements from the ocean.
Sources of Fission Products
The oceans may receive fission products from
two sources, materials from each of which have
unique properties important to deposition. The
two sources are:
(1) Radioactivities resulting from bomb bursts,
either in weapons testing or military use of
bombs in war time. Partial controls can be
put on the location and time of weapons tests
to take advantage of desirable dispersal or con-
centrating properties of the oceans.
(2) Radioactivity obtained from nuclear power
production plants and released to the oceans for
containment or dispersal. The time and location
of introduction of wastes of this type can be
controlled to obtain optimum oceanic charac-
teristics, and the character of the wastes might
be altered by the removal of one or more un-
desirable active or inactive constituents.
In both cases it can be expected that the
fission products will partition into a soluble and
an insouble fraction. An estimate of the ele-
ments that will appear in each fraction is given
in another part of this report.
This division into soluble and insoluble frac-
tions presents essentially two different systems
so far as deposition or dispersal processes are
concerned.
Deposition and Retention Processes
Deposition and retention of fission product
waste on the ocean floor will occur when the
waste is sufficiently denser than sea water to
permit it to settle to the bottom, and when the
stability of a waste-bottom component complex
is sufficiently greater than the stability of soluble
complexes that might form to prevent its re-
dissolving.
Solid formation
The "denser-than-sea-water" requirement can
be met when one of two processes occur: (1)
the formation of insoluble substances by inter-
action of the radioactive components of the
wastes with a sea water component, and (2)
sorption of the radioactive components of the
60
Chapter 6
Precipitation on the Ocean Bottotn
61
wastes by solids naturally occurring in sea water
or by solids formed by interaction of non-radio-
active components of the wastes with sea water
constituents.
Certain generalizations can be made with re-
gard to the formation of a solid phase — a
precipitate, by the interaction of radioactive
constituents with sea water components. Pre-
cipitation may occur when the solubility product
of a substance has been exceeded. Funda-
mentally, in order to be able to predict when
this condition has been met, knowledge of the
ionic activities of the species involved must be
known. Ionic activity is used here in the thermo-
dynamic sense, and is not related to activity in
the radioactive sense. Unfortunately practically
nothing is known about ionic activities of fission
product elements in sea water. The theoretical
approach through this route appears, therefore,
to be impractical.
The mass of radioactive elements that might
be introduced into the ocean from any expected
level of power production or foreseeable use
of bombs, will be small when compared to the
quantities of similar elements already in the
ocean. Thus, it is to be expected that chemical
precipitation of radioisotopes will occur only in
ocean regions where precipitation occurs nor-
mally. This process includes precipitation in
the usual sense and co-precipitation — the proc-
ess in which similar elements are simultaneously
removed from solution. For example, during
the precipitation of calcium carbonate, stron-
tium, a minor element, usually is co-precipitated
and carried along with the calcium carbonate.
Sorption processes involving inactive solids
provide another set of mechanisms that may pro-
duce radioactive solids. The solids that are
present in sea water or might be produced from
inactive waste components are generally finely
divided, have large area to volume ratio, and
are charged. The sorption of radioactive and in-
active dissolved constituents onto the solids, in
the ratio of their relative concentration, is fa-
vored by these characteristics. Thus, in cases
where an element normally present in sea water
is known to be taken up by suspended solids it
can be expected that radioisotopes of the same
or chemically similar elements will also be taken
up.
The oceans contain inorganic and organic,
living and dead suspended solids — all have
sorption properties and may remove active and/
or inactive constituents from solution.
Settling characteristics
The sinking of particles in the sea is usually
described in terms of Stokes' Law which as-
sumes, in its simplest form, smooth, rigid,
spherical particles of a stated diameter and den-
sity, sufficiently widely spaced so as not to im-
pede one another. It provided an adequate de-
scription of the behavior of these solids with a
restricted particle size range. For particles larger
than about 100 microns (0.1 mm) the law must
be modified to take into account turbulence
around the particle that has a net effect of re-
ducing the settling rate. Also, particles of col-
loidal and near-colloidal dimensions, less than
TABLE 1 Settling Velocity of Quartz Spheres
(In Distilled Water)
Settling
Diameter velocity
, '- V Time to settle
(mm) (microns) (m/day) 1000 m
1.0 1000 14,000 0.07 days
0.1 100 800 1.25 "
0.01 10 8 125
0.001 1 0.08 34 years
1/1024 0.98 0.07 39
1/2048 0.49 0.02 137
1/4096 0.25 0.004 685
1/8192 0.12 0.001 2,740
about a half micron, settle at a rate less than
predicted by Stokes' Law, presumably because
of charge interaction between particles and dis-
solved components.
Table 1 gives the settling velocities for par-
ticles of a stated size in distilled water, has been
calculated from Stokes' Law and is subject to
the criticisms noted above.
This table is a highly simplified and idealized
picture of the actual settling properties of solids
that normally occur in the oceans, and especially
of particles in the small size range. Particles in
this range probably will be the main concern
when considering the deposition of fission prod-
ucts. They are also in the size range that will
permit ocean circulation to alter markedly any
predicted location of deposition or of time to
reach the bottom.
The density and shape factors that effect
settling characteristics are important when con-
sidering organic solids or living organisms.
The density approaches that of sea water which
62
Atomic Radiation and Oceanography and Fisheries
reduces the settling rate, and the shape may
vary considerably from the smooth sphere as-
sumed for Stokes' Law.
The particle-size distribution of solids sus-
pended in the ocean as shown by sediments is
broad, varying from over a millimeter in di-
ameter for sands found near shore, to 0.1 micron
or less for sediments taken from the open ocean.
The median diameter of open-ocean particles is
in the range 1 to 8 microns.
The accumulation of solids on the ocean floor
is a relatively slow process. Table 2 (Holland
and Kulp, 1952) indicates the rate of sedimen-
tation on the several parts of the ocean floor.
TABLE 2 Sedimentation Rates
Fraction of sea Sedimentation
Type of sediment water rate x 10'*
gm/cm^ per year
Shelf 0.08 40
Hemipelagic 0.18 1.3
Pelagic 0.74
globigerina\
pteropod I ^-^^ 0-5
red clay 0.28 0.2
diatom "I ^ , ^ „ , ,
J. , . \ 0.10 0.15
radiolarian J
A weighted average gives approximately 0.75
mg/cm2 per year for the oceans. If the area of
the ocean floor is 3.6 x 10^^ cm^, the total depo-
sition will be 2.7 x 10^^ grams or 2.7 x 10^ tons
per year.
Retention
Prior to actual deposition on the bottom,
radioactive solids that have been formed above
the bottom may encounter changes in environ-
ment that will tend to return them to solution
and prevent or hinder deposition. For example,
resolution of precipitates with increasing pres-
sure (calcium carbonate), releases of radioac-
tivity from solids as they fall through uncon-
taminated water, vertical migration of organ-
isms, and vertical components of circulation are
all possible mechanisms that will tend to pre-
vent the deposition of radioactive material on
the bottom and, when coupled with horizontal
circulation features, will tend to disperse the
radioactivity over large areas.
The retention of radioactive material on the
ocean floor once it has been deposited there will
depend upon the stability of the floor relative
to erosion, to further deposition, and to tur-
bidity currents, and upon the chemical features
of the bottom relative to those through which
the solids have settled.
The deep ocean basins are the regions of
greatest stability in all respects. Regions near
shores and shelves are subject to the greatest
variations in deposition and erosion; in regions
where rivers enter the seas, relatively wide
changes in chemical properties take place.
Discussion of existing data
Three sources of information give some
insight into the probable behavior of fission
product elements in sea water. They are: (1)
existing information concerning the solution
chemistry of the elements in question, (2) the
behavior of radioactive debris observed in con-
nection with bomb tests in the Pacific, and (3)
information concerning the geochemistry of the
elements in question.
In utilizing information from these sources
to assess the probable fate of fission product ele-
ments in the oceans the chemical properties of
the oceans are of major importance. Table 3
lists the elementary composition of sea water
together with an estimate of the amounts of
natural activities present.
In Table 4 are listed fission product elements,
together with their half lives and the equilib-
rium quantities that would be in existence after
100 days cooling when formed in connection
with 10^^ megawatt hours per year of nuclear
power production. Also listed are the specific
activities that would result were these activities
to be mixed throughout the oceans. It will be
obvious from a consideration of oceanic prop-
erties, presented in other sections of this re-
port, that under any practical method of intro-
duction of wastes, attainment of uniform specific
activity of any given element throughout the
oceans will not occur. There will be gradients
of radioactivity, decreasing from the region of
introduction. The figures for specific activities
are, therefore, unrealistic and are included only
as a basis for making a better estimate when
the effects of circulation and fractionation can
be provided.
In a few cases, knowledge of the fraction of
an element, that would be normally removed by
geochemical processes will permit an estimate
to be made of the fraction of a radioisotope that
will be removed for a given loading. Con-
Chapter 6
Precipitation on the Ocean Bottom
63
TABLE 3 Elements in Solution in Sea Water (Except Dissolved Gases)1'2
mg/kg ,
Element CI = 19.00% Total in oceans (tons) Nuclide
Chlorine 18,980 2.66 X 10'"
Sodium 10,561 1.48 X 10'"
Magnesium 1,272 1.78 X 10''
Sulfur 884 1.23 X 10''
Calcium 400 5.6 X 10"
Potassium 380 5.3 X 10" K"
Bromine 65 9.1 X 10"
Carbon 28 3.9 X lO'^ C"
Strontium 13 1.8 X 10"
Boron A.6 6.4 X lO'^
Silicon 0.02 -4.0 0.028-5.6 X lO'^
Fluorine 1.4 2 X lO'^
Nitrogen (comp) . 0.01 -0.7 0.l4 -9.8 X 10"
Aluminum 0.5 7 X 10"
Rubidium 0.2 2.8 X 10" Rb*'
Lithium 0.1 1.4 X 10"
Phosphorus 0.001-0.1 0.014-1.4 X 10"
Barium 0.05 7 X 10"
Iodine 0.05 7 X 10'"
Arsenic 0.01 -0.02 1.4 -2.8 X 10'°
Iron 0.002-0.02 0.28 -2.8 X 10'°
Manganese 0.001-0.01 0.14-1.4 X 10'°
Copper 0.001-0.01 0.14 -1.4 X 10'°
Zinc 0.005 7 X 10'
Lead 0.004 5.6 X 10*
Selenium 0.004 5.6 X 10'
Cesium 0.002 2.8 X 10°
Uranium 0.0015 2.1 X 10° U^'
Molybdenum 0.0005 7 X 10' LP'
Thorium < 0.0005 <7 X 10' Th^^'
Cerium 0.0004 5.6 X 10'
Silver 0.0003 4.2 X 10'
Vanadium 0.0003 4.2 X 10'
Lanthanum 0.0003 4.2 X 10'
Yttrium 0.0003 4.2 X 10'
Nickel 0.0001 1.4 X 10^
Scandium 0.00004 5.6 X 10^
Mercury 0.00003 4.2 X 10^
Gold 0.000006 8.4 X 10°
Radium 0.2-3 X 10"'° 28 -420 Ra=='
iSverdrup, H. U., M. W. Johnson, and R. H. Fleming, OCEANS (1942)
2Revelle, R., T. R. Folsom, E. D. Goldberg, and J. D. Isaacs (1955).
Natural activities
Total (tons)
6.3 X 10'
56
Curies
4.6 X 10'^
2.7 X 10'
1.18 X 10"
8.4 X 10°
2.8
X10°
3.8 X 10'
2.1
Xio^
1.1 X 10'
1.4
Xio'
8 X 10
4.2 X 10-
1.1 xio°
versely, observations of the behavior of radio-
active isotopes would lead to a better under-
standing of the geochemistry of a given element.
Operational data
Of the fission products listed several are
either rare earths or rare-earth-like — such prod-
ucts all have very similar chemical properties.
All form relatively insoluble hydroxides of the
type R(OH)3. The solubility products of the
rare earth elements listed by Latimer (1952) all
fall in the range 10"-° to lO'So. Although a
quantitative comparison of the conditions that
actually exist in the sea cannot be made with
these constants, it would appear from the scant
information available concerning the quantities
of rare earth elements in the sea that marine
waters are saturated with respect to these ele-
ments and that a major portion of the rare earth
elements are dispersed in the sea as solids. This
is generally confirmed by American and Japa-
nese observations of the distribution of fission
product activities in the Pacific following bomb
tests. In most cases, however, it is difficult to
differentiate between "solid fractions" that have
been precipitated as solids by chemical processes,
and radioactive solids that have been accumu-
64
Atomic Radiation and Oceanography and Fisheries
lated by microscopic plankton organisms. Both
will be collected by filtration or centrifugation.
Goldberg (1956), however, noted that informa-
tion obtained during Operation WIGWAM
suggests a fractionation of a portion of the
fission product activities into solids that are col-
lected and concentrated by filter feeding or-
ganisms. The activity within the filter feeding
TABLE 4 Fission Product Activity After 100
Days Cooling from 10^^ Megawatt Hours of
Nuclear Power Production i
Specific
activity
Half-
Tons
Curies at
curies per
Isotope
life
(metric^
100 days
ton 2
Kr^^ . . .
94 y
7.3
3.3
Xio"
—
Sr* ...
55 d
86
2.3
Xio'^
0.128
Sr** ...
25 y
463
7.5
Xio"
0.0042
Y^o
62 h
—
7.48 X 10"
178
Y*!
57 d
Ill
2.8
Xio'^
6,660
Zr^ '.'.'.'
65 d
152
3.2
Xio'^
—
Nb"^ . . .
35 d
161
6.3
Xio'"
—
Ru^-^ ..
45 d
46
1.3
XIO'^
—
Rh^*^ ..
57 m
—
1.3
XIO'"
—
Ru^'^ ..
290 d
35
1.5
XlO'^
—
Rh^°« ..
30 sec.
—
5.15 X 10'"
—
T13X
8.0 d
—
5.2
X 10"
0.0743
Cs"'' '. ". '.
33 y
705
5.63 X 10'"
20.1
Ba'^^ ..
2.6 m
—
5.1
X 10'"
0.728
Ba^*° ..
12.5 d
2
1.5
Xio''
2.14
La»° ..
1.7 d
—
2.5
Xio"
595
Ce^*^ ..
28 d
45
1.5
Xio'^
268
Pr^« ..
13.8 d
2
1.4
Xio'^
—
Ce^" ..
275 d
490
1.6
Xio'^
386
Pr^" ..
17 m
—
2.4
Xio"'
—
Pm^^^ . .
. 94 y
7.3
3.3
Xio"
—
Sm^^^ ..
• 73 y
0.7
2.0
Xio^
—
lAdap
ted from
data
3f Culler (1954b) and
Revelle, et al. (1955).
2 Based on tonnage shown in Table 3.
organisms — ones adapted to the removal of
particulate material from suspension — showed
a high percentage of rare earth elements that
previously were noted as probably being pre-
dominantly dispersed as solids in the oceans.
These organisms were collected in the mixed
layer of the sea.
About a year after the 1954 nuclear tests
were completed. Operation TROLL undertook
a survey of the region west from the test site,
including the region just off the Phillipines and
northward off the coast of Japan (U. S. Atomic
Energy Commission, 1956). Seventy water and
plankton samples taken during this cruise were
analyzed radiochemically. When compared on
an equal weight basis (1000 gms wet plankton
vs. 1 liter of water) the plankton contained on
the average 470 times the activity of the water.
Significantly, 80 to 90 per cent of the activity
of the plankton was due to Ce^** (and its Pr^**
daughter) . Cerium is a rare earth. No informa-
tion is yet available concerning the species and
the relative quantities of organisms responsible
for the concentration of activity. A comparison
of the total activity per unit weight of macro-
and micro-plankton indicated approximately a
one and one half times greater concentration by
the micro-plankton.
It is noteworthy that the observations made on
Operations TROLL and WIGWAM revealed
a system in which the properties, with the ex-
ception of radioactive element content, were es-
sentially those of normal sea water. The sys-
tem can be imagined as being essentially sea
water to which had been added the radioactive
material — a procedure which because of the
extreme dilution of the contaminant, in a
chemical sense, would not affect the sea water
properties. Furthermore, these observations were
made on samples taken in the mixed layer (the
upper 100 to 300 m) .
These results, though largely qualitative in na-
ture, suggest the following conclusions regard-
ing the behavior of fission product elements in
the mixed layer of the open oceans:
1. Radioactive material will be retained in the
mixed layer for periods of at least a year during
which time horizontal motion may carry them a
few thousand miles. (Operation TROLL and
SHUNKOTSU-MARU data.)
2. Rare earth elements appear to be dispersed
primarily as solids and accumulated by the
plankton. (Operations TROLL and WIG-
WAM.)
3. The initial accumulation of rare earth ac-
tivities is predominantly by filter feeding or-
ganisms, presumably by retention of finely di-
vided solids in their feeding apparatus.
4. The cycle of rare earth activities through the
biota is unknown. Nevertheless, biological
agencies undoubtedly have an important influ-
ence in the deposition mechanisms.
The physical state of fission product elements
in sea water is important in all of the processes
that have been previously mentioned. Table 5
sets forth several fission product elements, the
percent of total activity present one year after
removal from a reactor and an estimate of the
Chapter 6
Precipitation on the Ocean Bottom
65
physical state of each if dispersed in sea water.
The estimates of physical states have been ob-
tained from oceanographic studies following
bomb tests and from considerations of the
"solution chemistry" of the elements. It should
be emphasized that the terms "solid" and "solu-
tion" are relative terms. Measurements made
during oceanographic studies invariably base
the division upon filterability. Such a division
TABLE 5 An Estimate of Solid and Soluble
Fractions for Fission Products in
Sea Water
TABLE 6 Geochemical Balance of Some
Elements in Sea Water (from Gold-
SCHMIDT, Quoted in Rankama and
Sahama, 1950, Table 16.19)
Element
Sr^«
Sr^o +Y°°
Zr""
Cs^' -f Ba^
Pm"^
Per cent of total
activity at end of Physical state in
one year sea water
3.8 Solution
1.7-1- 1.7 Solution -f solid
7.2 Solid
15 Solid
2.5 -j- 2.5 Mostly in solution
1.5 -f- 1.5
26 -f26
5.6
Solution
Solid
Solid
obviously will place soluble elements that are
utlized by organisms in the solid or solution -{-
solid category. The settling characteristics of
elements so combined will depend upon prop-
erties of the organisms. To what extent anoma-
lies of this kind are in the estimate above can-
not be stated. However, the estimates agree
qualitatively with those made from knowledge
of the behavior of elements in systems where
biological activity is not a major variable.
Culler (1954a), has noted that low level ac-
tivities discharged to White Oak Creek end up
primarily with the clay in a retention basin.
The character of the waste was not noted.
Krumholz (1954), however, found considera-
ble uptake of radioactivity in the biota with
subsequent relocation and dispersion in the
same region.
Geochemical data
An estimate of the behavior of several sea
water constituents can be obtained from the re-
sults of geochemical studies. These studies per-
mit an evaluation of the fraction of an element
supplied to the oceans that is removed from so-
lution. The removal processes may include one
or more of those previously mentioned. The
results permit no choice of mechanisms. Table 6
lists several elements found in sea water, the
Total
supplied
Element (ppm)
Na 16,980
K 15,540
Kb 186
Ca 21,780
Sr 180
Ba 150
Fe 30,000
Y 16.9
La 11
Ce 27.7
Amount
present in
ocean Transfer
(ppm) percentage
10,560 62
380 2.4
0.2 0.1
400 1.8
13 7.2
0.05 0.03
0.02 0.00007
0.0003 0.002
0.0003 0.003
0.0004 0.001
quantities supplied to and present in the oceans
and a quantity, the transfer percentage, which
is the percentage of "present" to "supplied."
Large values of transfer percentage indicate
that relatively large fractions of the elements
supplied to the oceans stay in solution — small
values of transfer percentage that relatively
much is removed.
Using the transfer percentages listed for
cesium, strontium, and cerium, and estimates of
the specific activities that would occur in the
oceans as a result of 10^^ megawatt hours nu-
clear power production, the reduction through
geochemical processes has been calculated. The
figures are given in Table 7.
TABLE 7 Activity Reduction By Geochemical
Processes
Specific
Specific Transfer activity
activity percent- after
(c/gm) age removal
Element (no removal) (c/gm)
Cesium 8.6 X 10"^ 0.005 4.3 X 10"^
Strontium 6.8 X 10"' 7.2 4.9 X IQ-'"
Cerium 1.8 X 10"^ 0.001 1.8 X lO"'"
Laboratory data
Floccing, possible in the disposal of wastes
rich in iron or aluminum, may assist in removal
of fission products. Unless settling times of nat-
ural or artificial floes are short, resolution and
biological uptake may reduce the settling factor
markedly.
Goldberg (1954) has described the copre-
cipitation processes with iron and manganese.
While none of the fission product elements are
treated, analyses show that the amounts of trace
(>e
Atomic Radiation and Oceanography and Fisheries
elements in the sediments are proportional to
the iron or manganese content. In addition, fil-
ter feeders show concentrations indicating up-
take of undifferentiated particulates.
Several experiments have been reported in
which the reactions between fission product ac-
tivities (mixed and individual isotopes) and
suspended solids have been studied. In the fol-
lowing examples both marine and fresh water
experiments are noted.
Gloyna in Goodgal, Gloyna, and Carritt
(1954) noted that 58 per cent of mixed fission
product activity (initially less than 1000 cpm)
could be removed from solution during cen-
trifugation of untreated Clinch River water, 70
ppra solids, pH 8.4 and alkalinity 92 ppm (Ca-
CO3). No attempt was made to determine
which elements were removed.
Carritt and Goodgal (1954) studied the up-
take of phosphate, iodide, iron III, strontium
sulphate and copper II on samples of Chesa-
peake Bay sediments. Measurements were made
under controlled but varied pH, temperature,
salinity, concentration of solids, and specific ac-
tivities. Of the elements studied strontium, io-
dide and sulphate are of interest here — sul-
phate because of the similar chemical behavior
of tellurium. Iodide showed no uptake at con-
centrations applicable to the present discussion.
Under conditions where strontium carbonate
did not precipitate, strontium was absorbed ac-
cording to the following isotherm:
x/m= 0.0032 C"-**
x/m=jug atoms Sr per milligram of solids
C= equilibrium concentration of strontium
in jLtg atoms Sr per liter.
This isotherm was valid over the range 52 to
5200 ^g atoms Sr per liter.
The uptake of sulphate showed strong pH
dependence. At pH above 4.5 very little uptake
was noted. With decreasing pH, uptake in-
creased, suggesting that the bisulphate is more
active than sulphate.
At pH 3.3 (an unlikely marine condition)
the uptake followed the isotherm:
x/m = 0.0013 C0-S2
over an initial sulphate concentration range of
10».
Several proposals on ocean waste disposal
would allow introduction of packaged waste
into the bottom by sea burial. Dispersion of ac-
tivity would be a slow diffusion process as from
concreted wastes or would be delayed until rup-
ture of an impermeable container. In either
case, the activity released would go into the
highly absorptive environment of the sediments.
One form of packaging for the disposal of
active waste has been proposed by Hatch
(1954). He has described the problems en-
countered with the absorption of fission prod-
ucts onto montmoriilonite clays, followed by fir-
ing to 800° C, to produce a high density, high
specific activity, insoluble waste. When given
appropriate pretreatment, it was estimated that
fission products could be removed from reactor
wastes to yield clays with an activity of about
10 curies per gram. The practicability of utili2-
ing solids of this kind apparently depends upon
the demonstration of long term stability under
deep ocean conditions and upon the economics
of production and transportation. It should be
noted that short term stability tests suggest that
the fired montmoriilonite clays would be ex-
tremely stable.
Deep ocean deposits have appreciable base
exchange capacities. Revelle measured this to
be in the range 30-60 millequivalents per 100
gram of solids. Soluble waste components can
be expected to react with solids on the bottom
surface and to be removed from solution by
base exchange reactions, and isotopic exchanges.
No estimate seems possible of the depth into the
sediments that this kind of reaction would take
place. Certainly the surface layer of sediments
would become saturated and reaction with deep
sediments would be controlled by diffusion into
the sediments.
Further data required
A survey of available literature reveals many
gaps in our knowledge in this field. Basic data
on the settling processes of natural sedimenta-
tion are few, and the carrying processes by
which tracer concentrations of isotopes would
be removed from the oceans have been almost
entirely neglected. From a practical point of
view, the data most needed are measures of the
gross sedimentation rate of radioactivity. This
would be an integral of the effects of many
processes — empirical information that would
permit a statement concerning the sedimentation
rate of activity without reference to the many
mechanisms involved.
Chapter 6
Precipitation on the Ocean Bottom
61
Nevertheless, for an understanding of the
overall process — so that predictions for condi-
tions other than those existing at the time of
observations can be made, and to provide infor-
mation useful to other studies, many individual
processes should be studied. The following
studies, grouped according to the primary source
of information, and thought to be pertinent to
the sedimentation and retention problem, would
provide some insight into these processes. Ob-
viously, information obtained from one group
of studies may be of value in the solution of
problems in others.
Data from weapons tests
1. Measurement of the immediate partition of
weapons test debris among large-sized immedi-
ate fallout, water-borne activity and the air-
borne material which may be quite uniformly
distributed over the world.
2. Measurement of partition of individual iso-
topes in sea water between particulate material
and solution. (Dynamic and equilibrium con-
ditions).
3. Mechanism of sorption of radioisotopes on
natural suspended solids under the conditions
existing in ocean water.
4. Measurement of settling rates of natural in-
organic particulates, probably by tracer tech-
niques.
5. Measurement of detrital settling rates, in-
cluding plankton average life.
6. Measurement of uptake and element differ-
entiation in organisms which may become de-
trital material.
Data from waste disposal experiments
Certain studies here can be combined with
tracer studies, designed primarily to give infor-
mation on basic oceanographic problems:
1. Life expectancy of burial containers.
2. Diffusion rate from concreted or sintered
blocks as a function of size, and the concentra-
tion and istopic composition of wastes.
3. Regardless of what disposal system is
adopted, there will be liquid wastes produced,
and studies must be made of liquid waste dis-
persal. The pertinent effects will be more re-
lated to the weapons test data requirements
since this is a surface to bottom transfer.
Tracer experiment data
1 . Coprecipitation of individual fission products
with their stable isotopes normally occurring in
sea water, and the particle size distribution of
the solids formed, and their sedimentation rate.
2. Similar data on coprecipitation by isomor-
phous replacement, for example the carrying of
radiostrontium with inactive calcium.
3. Rate of entry of diffused material into the
basic biological systems. This includes the bot-
tom to surface movement as modified by sedi-
mentation.
4. Exchange capacities of sediments for the ra-
dioisotope ions in sea water medium, and rate
of diffusion of these isotopes into the undis-
turbed bottoms.
In all studies in which dispersion, partition,
concentration and localization occur, measure-
ments that would permit a balance sheet to be
made (all the activity should be accountable)
seem desirable and necessary.
SUMMARY
The only semi-quantitative data relevant to
the problem of activity removal from the ocean
surface are the geochemical data. These indicate
a reduction factor of 14 for strontium, 2,000
for cesium, and 100,000 for cerium (and proba-
bly all rare-earth-type elements). No informa-
tion is available on such elements as ruthenium,
rubidium, and iodine. Other mechanisms de-
scribed may contribute to activity removal, but
their effects cannot be evaluated with present
knowledge.
The reduction factors are for equilibrium con-
ditions, and the high sea water activity found a
year after the Castle tests (Operation TROLL)
indicate that equilibrium is reached slowly.
Activity introduced on the bottom through
sea burial will be subject to entirely different
removal processes. No estimate can be made of
their effectiveness.
Carritt, D. E., and S. Goodgal. 1954. Sorp-
tion reactions and some ecological impli-
cations. Deep-Sea Research 1:224-243.
Culler, F. L. 1954a. Unpublished results.
Culler, F. L. 1954b. Notes on Fission Prod-
uct Wastes from Proposed Power Reac-
tions. ORNL Central File No. 55-4-25.
68
Atomic Radiation and Oceanography and Fisheries
Goldberg, E. D. 1954. Marine Geochemis-
try 1. Chemical Scavengers of the Sea.
/, Geol. 62:249.
Goldberg, E. D. 1956. Unpublished results.
Presented at Princeton, N. J., March 3, 4,
5, 1956 meeting of NAS Study Group on
Oceanography and Fisheries.
GooDGAL, S., E. Gloyna, and D. E. Carritt.
1954. Reduction of radioactivity in water.
]our. Amer. Water Works Assoc. 46, No.
1:66-78.
Hatch, L. P. 1954. Clay adsorption of high
level wastes. Ocean dispersal of reactor
wastes, meeting at Woods Hole Oceano-
graphic Institution, Woods Hole, Mass.,
August 5-6.
Holland, H. D., and J. L. Kulp. 1952. The
distribution of uranium, ionium and ra-
dium in the oceans and in ocean bottom
sediments. Lamont Geological Observatory
Technical Report No. 6.
Rankama, K., and T. G. Sahama. 1950. Geo-
chemistry. University of Chicago Press.
Krumholz, L. a. 1954. A summary of find-
ings of the ecological survey of White Oak
Creek, Roane County, Tenn., 1950-1953.
USAEC-ORO 132.
Latimer, W. M. 1952. Oxidation Potentials.
Prentice Hall, New York.
Revelle, R., T. R. Folsom, E. D. Goldberg,
and J. D. Isaacs. 1955. Nuclear Science in
Oceanography. International Conference
on the peaceful uses of atomic energy. A/
conference 8/P/277. Scripps Institution
of Oceanography contribution No. 794.
Sverdrup, H. U., M. W. Johnson, and R. H.
Fleming. 1942. The Oceans. Prentice
Hall, New York.
U. S. Atomic Energy Commission. 1956.
Operation TROLL. U. S. Atomic Energy
Commission, New York Operations Office,
NYO 4656, ed. by J. H. Harley, 37 pp.
Chapter 7
ECOLOGICAL FACTORS INVOLVED IN THE UPTAKE, ACCUMULATION,
AND LOSS OF RADIONUCLIDES BY AQUATIC ORGANISMS '
Louis A. Krumholz, Department of Biology, University of Louisville, Louisville, Kentucky
Edward D. Goldberg, Scripps Institution of Oceanography, University of California,
La Jolla, California
Howard Boroughs, Hawaii Marine Laboratory, University of Hawaii, Honolulu, T. H.
Introduction
This paper is concerned with the uptake, ac-
cumulation, and loss by living organisms, of
radioactive materials that may be added to or
induced in an aquatic environment. These
aquatic organisms may live in either fresh, salt,
or brackish water and include vascular plants,
algae, protozoans, plankton, all the other in-
vertebrate forms such as aquatic insects, bottom-
living crustaceans and molluscs, and representa-
tives of each of the five classes of vertebrate
animals.
The accumulation and loss of any radioiso-
tope will depend not only upon its own physical
half-life but also upon the biological factors
that contribute to its incorporation in, reten-
tion by, and disappearance from the organism
involved. In general, all isotopes of any one
chemical element are similar in chemical behav-
ior, and thus it can be assumed, when tracing
the paths of most chemical elements through
biological systems, that a radioactive atom will
behave in the same way as a non-radioactive
atom of the same species. However, relatively
little is known about the actual mechanisms of
uptake, accumulation, and loss by marine and
fresh-water organisms of the elements whose
isotopes constitute fission products and other
radiomaterials.
For the purposes of this discussion, the fol-
lowing terms will be defined:
Uptake is the amount of material that enters the
organism in question and the speed at which the
material enters is the rate of uptake.
1 Contribution No. 9 (New Series) from the De-
partment of Biology, University of Louisville. Con-
tribution from the Scripps Institution of Oceanography,
New Series, No. 901a. Contribution from the Hawaii
Marine Laboratory, No. 94.
Loss is the amount of material that leaves the
organism, and the speed at which it leaves is
the rate of loss.
Accumulation is the amount of material that is
present in the organism at a given time, and the
rate of accumulation is the amount accumulated
per unit time. In practice, the accumulation is
the difference between the uptake and the loss.
Metabolic processes include all the chemical
changes concerned in the building up and de-
struction of living protoplasm. During these
changes, energy is provided for the vital proc-
esses and for the assimilation of new materials.
Specific activity is the ratio between the amount
of radioactive isotope present and the total
amount of all other isotopes of that same ele-
ment, both radioactive and stable. Most com-
monly, it is given as the microcuries of radio-
isotope per gram of total element.
Although the higher animal forms are de-
pendent upon the primary concentrators, the
plants, for their source of energy, these animals
may or may not be dependent upon the lower
forms for many elements. Some elements may
enter the bodies of the higher forms directly
from the water, while others must be supplied
from the lower trophic levels through the food
web. These food webs are not the same for all
organisms and may even be different for the
same organism at various seasons of the year.
In some instances certain elements, although
present in the environment, are not in the
proper physical and/or chemical state to be util-
ized by the organisms and thus are not available
for metabolism.
Radionuclides may become associated with an
organism either through adsorption to surface
areas, through engulfment, or through metabolic
69
70
Atomic Radiation and Oceanography and Fisheries
processes; in some instances assimilation may
take place following the engulfment of living
or inert particulate matter. A radionuclide may
also be incorporated into an organism by simple
exchange of the radioactive isotope for the sta-
ble isotope of the same species. It is therefore
important to know the physical and chemical
state necessary for metabolism, the mode of
entry, and the ability of all organisms at each
of the different trophic levels to concentrate the
various radionuclides.
Physical and Chemical Factors Concerned with
the Uptake of Radionuclides by Living
Organisms
a. Acute versus chronic exposure
Chronic exposure of an aquatic organism,
even to low concentrations of radiomaterials,
usually has a markedly different effect on the
organism than an acute exposure; the principal
difference lies in the amount of radiomaterial
accumulated in the tissues. Because many
aquatic organisms have the ability to concentrate
radiomaterials from their environments by fac-
tors up to several hundred thousand, much ra-
diomaterial may be accumulated during a
chronic exposure for a relatively long period of
time. A state of equilibrium is ultimately
reached at which there is a constant uptake and
a constant loss with a resultant constant maxi-
mum level of accumulation. Conversely, in an
acute exposure, such as a single feeding or a
single injection of radiomaterials, only a certain
relatively small fraction of the radiomaterial is
accumulated in the body and the remainder is
lost. In such an instance, the maximum level to
which an organism is capable of accumulating
the radiomaterial in question is seldom reached
and certainly not maintained.
Krumholz and Rust (1954) reported an ac-
cumulation of one microcurie of strontium 90
per gram of bone in the entire skeleton of a
muskrat {Ondatra zibethica) which had been
utilizing foods of its own choice in the area
contiguous to the Oak Ridge National Labora-
tory. Certainly this instance can be presumed to
represent a chronic exposure inasmuch as the
animal was at least two years old and had
probably lived in the area during her entire life-
time. Aquatic organisms in the Columbia River
below the Hanford Works and those in White
Oak Creek, Tennessee, below the Oak Ridge
National Laboratory, have all suffered chronic
exposures to radiomaterials and have accumu-
lated considerable amounts of those materials
in their tissues. Hiatt, Boroughs, Townsley, and
Kau (1955) found that the daily feeding of
strontium 89 to the fish Tilapia for short pe-
riods of time (four days) did not increase the
level of strontium retention after an apparent
steady-state condition had been reached. How-
ever, there are no published reports of the re-
sults of long-term, controlled experiments of
chronic exposures of aquatic organisms to radio-
materials.
The literature contains many reports con-
cerned with acute exposures of aquatic organ-
isms to radiomaterials. Martin and Goldberg
(unpublished data), who gave single feedings
of strontium 90 to Pacific mackerel (Pneumato-
phorus japonic us die go), found that less than
five per cent of the amount fed was retained in
the body after 48 hours. Much of the five per
cent that was incorporated in the skeleton re-
mained there for the duration of the experiment
(235 days). Boroughs et al. (1956) reported
that between only one and two per cent of the
strontium 89 fed to ten yellowfin tuna {Neo-
thunnus macropterus) remained in the body
after 24 hours. The small amount retained in
the body was largely incorporated into the skele-
tal structures. However, other fish {Tilapia)
which had been fed similarly prepared stron-
tium 89 capsules retained about 20 per cent of
the ingested material after 24 hours. After four
days, the amount retained finally levelled off at
values that ranged from 1.5 to 19.5 per cent of
the amount ingested; the average amount re-
tained was about 7.5 per cent. Here, again, the
retained materials were incorporated mainly in
the skeletal structures and integument.
b. Chemical and physical states of the ele-
ments in the environment.
The chemical composition of the marine en-
vironment cannot be rigorously defined. The
concentrations of elements depend upon the
type and location of the water mass. Although
more than 90 per cent of marine waters occur
at depths greater than 1000 meters, the majority
of chemical analyses have been made for shal-
lower waters. Because of the biological ac-
tivity of the oceans and the movements and
origins of water masses, the abundance of cer-
tain elements appears to vary by factors greater
than two orders of magnitude. However, as a
Chapter 7
Ecology of Uptake by Aquatic Organisms
71
first approximation, the chemical constituents
may be considered to be much the same in all
places. Fairly good approximations of the con-
centrations of elements in sea water are listed
in Table 1 as the numbers of atoms per million
atoms of chlorine. The reported values of con-
centrations of elements on which Table 1 is
based frequently fail to distinguish between the
solid and dissolved phases.
Whereas the oceans may be considered very
roughly as a homogeneous mass, most bodies of
fresh water must be examined on an individual
basis because of the tremendous range in their
physical and chemical characteristics. Many of
the elements that occur normally in the oceans
are in concentrations too small to be detected by
present methods or are present in only trace
amounts in fresh water. The pH of fresh waters
ranges from perhaps as low as 2.2 to a high of
about 10.5 although the pH of most lakes and
streams falls somewhere between 6.5 and 8.5.
The total dissolved solids in fresh waters ranges
TABLE 1 Chemical Abundances in the Marine H\'drosphere
mg/1
H 108,000
He 0.000005
Li 0.2
Be
B 4.8
C 28
N 0.5
O 857,000
F 1.3
Ne 0.0003
Na 10,500
Mg 1,300
Al 0.01
Si 3
P 0.07
S 900
CI 19,000
A 0.6
K 380
Ca 400
Sc 0.00004
Ti 0.001
V 0.002
Cr 0.00005
Mn 0.002
Fe 0.01
Co 0.0005
Ni 0.0005
Cu 0.003
Zn 0.01
Ga 0.0005
Ge < 0.0001
As 0.003
Se 0.004
Br 65
Kr 0.0003
Rb 0.12
Sr 8
Y 0.0003
Zr
Nb
Mo 0.01
Tc
Ru
Rh
Pd
atoms/ 10^
atoms CI
202,000,000
50
.002
830
4,300
70
100,000,000
130
0.03
850,000
100,000
0.7
200
4
52,000
1,000,000
28.5
18,000
19,000
0.002
0.04
0.08
0.002
0.07
0.3
0.02
0.02
0.09
0.3
0.01
< 0.003
0.07
0.1
1,500
0.007
2.2
160
0.006
0.2
atoms/ 10'
mg/1 atoms CI
Ag 0.0003 0.005
Cd 0.000055 0.0009
In < 0.02 < 0.3
Sn 0.003 0.05
Sb < 0.0005 < 0.008
Te
I 0.05 0.7
Xe 0.0001 0.001
Q 0.0005 0.005
Ba 0.0062 0.008
La 0.0003 0.004
Ce 0.0004 0.005
Pr
Nd
Pm
Sm
Eu
Gd
Tb
Dy
Ho
Er
Tm
Yb
Lu
Hg
Ta
W 0.0001 0.001
Re
Os
Ir
Pt
Au 0.000004 0.00004
Hg 0.00003 0.0003
Tl < 0.00001 < 0.00009
Pb 0.003 0.03
Bi 0.0002 0.002
Po
At
Rn 9.0 X 10"'^ 8.0 X 10"
Fr
Ra 3.0 X 10"" 2.0 X 10"
Ac
Th 0.0007 0.006
Pa 0.003 0.03
U
72
Atomic Radiation and Oceanography and Fisheries
from very low concentration (less than 5 ppm)
in the "battery-water" lakes to very high concen-
trations (more than 400 ppm) in the "alkali"
lakes. The fertility of fresh waters ranges from
the almost sterile bog lakes to the highly pro-
ductive lakes in the midwestern prairies.
The physical states and ionic speciation of
elements in sea water cannot be as well defined
as their absolute concentrations. However, us-
ing the known physicochemical constants, and
assuming a pH of 8 and a salinity of 35 parts
per thousand for sea water, Krauskopf (1956)
postulated that the principal valence states of
the ions of a number of metals in sea water are
as listed in Table 2. From these data it may
TABLE 2 Calculated Valence States for
Metallic Ions in Sea Water
(From Krauskopf, 1956)
Element Ion
Zinc Zn-f +, ZnCl+
Copper Cu++, CuCI-f
Bismuth BiO-f
Cadmium CdCl-f, CdCU
Nickel Ni+-f , NiCl+
Cobalt Co-f +
Mercury HgClr
Silver AgCIa"
Gold AuCIr (Calculated by
Goldberg)
Chromium CrOr
Vanadium HsVOr, HaVoOr"
Magnesium Mg-| — \-
Calcium Ca+-f-
Strontium Sr-\ — \-
Barium Ba+-|-
be concluded that most monovalent or divalent
ions, except the noble metals, will occur as ca-
tions whereas most metals with valences higher
than two, and the noble metals, will occur as
anions.
The physical states of a given element under
equilibrium conditions depend upon whether or
not the solubility product of the least soluble
species has been exceeded. Greendale and Bal-
lou (1954) have determined the distribution of
elements among the soluble, colloidal, and par-
ticulate states by simulating the conditions of an
underwater detonation of an atomic bomb.
Their data are presented in Table 3.
It is not known whether the elements that
occur in colloidal or particulate phases are
homogeneous entities or are sorbed in other
solid phases. Nevertheless, it appears that ele-
ments of Groups, I, II, V, VI, and VII usually
occur as ionic forms in sea water, whereas other
elements, excluding the rare gases, occur pre-
dominantly as solid phases. These generaliza-
tions have been confirmed in field tests after
underwater detonations where more than 50 per
cent of the resultant radioactivity was associated
with solid phases retained by a molecular filter
of pore size 0.5 micron (Goldberg, unpublished
data) .
Although the data supplied by Greendale and
Ballou (1954) are of value for the physical
states of elements following the detonation of
an atomic bomb, they are at best only suggestive
of the steady-state conditions which might re-
sult from the continuous spilling of fission
product wastes into the sea on a long-term basis.
TABLE 3 Physical States of Elements in Sea
Water
(From Greendale and Ballou, 1954)
Percentage in given physical state
Element Ionic Colliodal Particulate
Cesium 70 7 23
Iodine 90 8 2
Strontium 87 3 10
Antimony 73 15 12
Tellurium 45 43 12
Molybdenum 30 10 60
Ruthenium 0 5 95
Cerium 2 4 94
Zirconium 1 3 96
Yttrium 0 4 96
Niobium 0 0 100
Metabolic processes concerned with the uptake,
accumulation, and loss of radionuclides
There are many factors concerned with met-
abolic processes which are to be considered
among the biological aspects of the accumula-
tion of radiomaterials. It has been demonstrated
that the metabolism of all form.s of life is re-
markably similar at the cellular level even
though the morphological differences among
aquatic organisms range from the bacteria
through the vertebrate forms, and from the
algae through the vascular plants. Nevertheless,
differences do exist. These differences are gov-
erned by the complex anatomies, life histories,
and physiological processes, and the relation-
ships of the organisms with each other and with
their environment. All of these differences must
be considered in the light of the physical and
chemical states of the elements involved.
Chapter 7
Ecology of Uptake by Aquatic Organisms
73
In different organisms, ionized or particulate
fission-product wastes and other radiomaterials
may be either adsorbed, engulfed, or accumu-
lated by metabolic processes. For example,
Rothstein and his associates (1951) demon-
strated that uranium as the uranyl ion was ad-
sorbed by yeast cells. Hamilton and co-workers
(see Hevesy, G., 1948, p. 441) showed that
particulate radiomaterials such as various un-
complexed rare earths at physiological pH's
were adsorbed by the gut lining of rats. In
these experiments practically no accumulation of
these particular radiomaterials by the animal
was observed. On the other hand, Goldberg
(1952) demonstrated with radioactive iron that
a marine diatom assimilated particles of hy-
drated iron oxide, but that these organisms were
unable to take up ionic iron in a complexed
form.
The first biological experiments in which ra-
dioactive atoms were used were performed by
Hevesy in 1923. In those classical experiments
it was demonstrated that plants could take up
lead from solution and translocate it throughout
the vascular system.
The accumulation of radioelements is also de-
pendent upon many chemical characteristics of
the water in question. Among the parameters
affecting accumulation are the salinity, percent-
age composition of the dissolved solids, pH, the
oxygen-carbon dioxide ratio, and the presence
of complexing agents.
a. Chemical composition of marine organisms
A modern systematic study of the inorganic
constituents of marine organisms is yet to be
made. The best summary of existing knowledge
may be found in Vinogradov (1953).
However, certain generalizations can be
drawn from the recent literature on the concen-
tration of metals by marine organisms. Gold-
berg (in Treatise of Marine Ecology, volume II,
edited by J. Hedgpeth, in press) has pointed
out that the marine biosphere tends to concen-
trate such heavy metals as copper, nickel, zinc,
etc., over the marine hydrosphere by factors of
100 to 100,000 on a weight-f or- weight basis
(Table 4) . These metals are strongly bound in
the organisms and cannot be easily removed by
elution. Further, the elements most strongly
concentrated in the biosphere are those that
form the most stable complexes with organic
chelating agents. As an example, copper is con-
centrated over sea water in the soft parts of
most marine organisms by factors of 10^ to 10*
whereas calcium shows concentration factors of
less than 1 to 50. Copper forms very strong
complexes with many organic compounds
whereas calcium does not. Although the exact
role of most metals in the physiology of organ-
isms is not known, nevertheless, one might a
priori expect that some heavy metals introduced
into the ocean from nuclear reactions would
concentrate in the biosphere.
b. Concentration in the etivironment
The concentration of a given radiomaterial
by an organism is sometimes proportional to
the concentration of that material in the en-
vironment. This generalization applies both to
aquatic and to terrestrial organisms. The uptake
of cesium 137 by the oyster (Crassostrea vir-
ginica) has been shown to be dependent upon
the external concentration of cesium in the sea
water (Chipman, et al., 1954). Prosser, et al.
(1945), noted that with the addition of stron-
tium to the environment there was an increase
in the uptake of that element by goldfish {Car as •
sitis auratus). Also, it has been demonstrated
that as the carrier concentration in the nutrient
environment is increased, the concentration fac-
tor for a particular fission product in terrestrial
plants tends to increase (Rediske, et al., 1955).
c. Effect of the presence of one element on
the uptake of another element
The uptake of one radioelement by an organ-
ism may be altered by the relative abundance
of another element in the environment. In
instances in which more than one element is
involved, one of three phenomena may be
observed :
First, elements of similar chemical properties
may substitute for one another. For example,
it has been shown by Prosser, et al. (1945),
that when the amount of calcium in the water
was low, there was an increase in the uptake of
strontium 89 by goldfish. Conversely, as the
amount of calcium was increased, the uptake of
strontium decreased. Rice (1956) observed that
cells of Carteria grown in artificial sea water
took up strontium in proportion to the stron-
tium/calcium ratio in the medium. Bevelander
and Benzer (1948) have shown that a modifica-
tion of the constituents of sea water resulted
in a change in the constituents of the shells de-
posited by mollusks.
Second, some elements may have an inhibi-
tory effect on others. A classical example of this
74
Atomic Radiation and Oceanography and Fisheries
phenomenon is that in which calcium inhibits
the stimulatory action of potassium on heart
muscle.
Third, there may be a synergistic effect of one
element on another. Ketchum (1939) has
shown that the uptake of phosphorus by marine
diatoms was enhanced with increased concen-
trations of nitrogen.
d. Specificity of organisms and tissues for
given elements
The specific activity of a radionuclide in any
present in the flight muscles of some birds and
it has been shown that radiophosphorus is in-
corporated into the flight muscles of migratory
waterfowl (Krumholz, 1954).
Although many different kinds of aquatic or-
ganisms have the ability to concentrate phos-
phorus in their tissues, there are few that show
such a specificity for that element as the various
plankters. The uptake of phosphorus 32 by
plankton algae in a lake has been demonstrated
by Coffin and his associates (1949) and others,
TABLE 4 Approximate Concentration Factors of Different Elements in Members of the Marine
Biosphere. The Concentration Factors are Based on a Live Weight Basis.
Concentration Factors
Concentration Algae
Form in in seawater (Non-cal-
Element Seawater ( micrograms/ 1.) careous)
Na Ionic 10' 1
K Ionic 380,000 25
Cs Ionic 0.5 1
Ca Ionic 400,000 10
Sr Ionic 7,000 20
Zn Ionic 10 100
Cu Ionic 3 100
Fe Particulate 10 20,000
Nil Ionic 2 500
Mo lonic-Particulate 10 10
V ? 1 1,000
Ti ? 1 1,000
Cr ? 0.05 300
P Ionic 70 10,000
S Ionic 900,000 10
I Ionic 50 10,000
1 Values from Laevastu and Thompson (1956).
Invertebrates
Vertebrates
Soft
Skeletal
Soft
Skeletal
0.5
0
0.07
1
10
0
5
20
10
—
10
—
10
1,000
1
200
10
1,000
1
200
5,000
1,000
1,000
30,000
5,000
5,000
1,000
1,000
10,000
100,000
1,000
5,000
200
200
100
—
100
—
20
—
100
—
20
—
1,000
—
40
—
10,000
10,000
40,000
2,000,000
5
1
2
—
100
50
10
—
organism is dependent upon the ability of the
organism or any of its parts to concentrate that
nuclide. If the stable counterpart of the radio-
nuclide does not normally enter into the physio-
logical processes of an organism, neither will
the radioactive material.
It is well known that certain tissues have a
predilection for concentrating specific elements.
For instance, iodine is concentrated in the thy-
roid tissue of animals and hence radio-iodine
will also be concentrated there. Strontium, like
calcium, is a bone seeker and the radioisotopes
of both of those elements will be concentrated
in the bony skeletons of animals. Similarly,
both strontium and calcium are concentrated in
certain parts of vascular plants and so are the
radioisotopes. Phosphorus is one of the princi-
pal constituents of bone and radiophosphorus
is also concentrated in that tissue. The com-
pound adenosine triphosphate is commonly
and Whittaker (1953) showed that phyto-
plankters from the Columbia River concentrated
radiophosphorus by factors as great as 300,000.
Krumholz (1954, 1956) found that attached
fresh-water algae (Spirogyra) concentrated ra-
diophosphorus by a factor of 850,000, and that
many fresh-water zooplankters concentrated that
radionuclide by factors of more than 100,000.
Approximate concentration factors for marine
organisms are given in Table 4.
e. Osmotic and ionic regulation
Osmotic and ionic regulation are known to
occur in a variety of ways. The usual pathways
of excretion are through the urine, feces, skin,
respiration, and particle ejection, and the
method of excretion depends upon the particu-
lar organism and element involved. Ionic regu-
lation may also occur by way of the chloride
secreting cells in the gills of those fishes that
migrate from salt to brackish water (Keys,
Chapter 7
Ecology of Uptake by Aquatic Organisms
75
1931). Unfortunately, no experiments on such
ionic regulation have been performed with ra-
dionuchdes.
f. Reproductive processes
The reproductive processes of plants and ani-
mals range from simple fission among the
unicellular organisms to the very complex rela-
tionships among the gametogenic forms. Dur-
ing reproduction there is a transfer of materials
from the parent to the offspring.
In simple fission, the parent cell splits in
two and each offspring receives approximately
half of the parent material and thus only half
of any radiomaterial that may have been pres-
ent. Under conditions of chronic exposure, the
offspring of organisms that reproduce by fission
will incorporate usable radiomaterials into their
bodies and a state of equilibrium eventually
will be reached.
Among the egg-laying forms, most of the
material received by the offspring is derived
from the contents of the egg. In this form of
reproduction, once the egg is laid there will be
no further loss of radiomaterials from the
mother or gain to the offspring. This applies
even when the environment is contaminated
and there is chronic exposure of the parents,
because the protective coverings of the egg pre-
vent the entrance of radiomaterials.
Among the forms that bear their young alive,
however, there is usually some continuous trans-
port of materials between the mother and the
embryo. In such an instance it is probable that
the embryo will accumulate radiomaterials with
a resultant loss to the mother. If chronic ex-
posure of a mother carrying an embryo con-
tinues during pregnancy, a state of equilibrium
may eventually be reached between the mother
and the environment and between the mother
and the embryo.
During embryological development of all
kinds there is a "biological dilution" of radio-
materials through cell division and growth. This
statement applies primarily if there has been
an acute exposure to radiomaterials or if the ex-
posure has stopped with the commencement of
the embryological development.
g. Molting
In instances where the embryos pass through
a series of metamorphic stages, there is a loss of
radiomaterials from stage to stage as, for ex-
ample, the loss from instar to instar in insects
through molting. Furthermore, it has been
demonstrated by Chipman and coworkers (per-
sonal communication) that there is an increased
accumulation of elemental constituents in crus-
taceans prior to molting, and a loss of such ma-
terials when the carapace is lost.
h. Age and groivth
It has been established (Olson and Foster,
1952) that younger, more rapidly growing
fishes accumulate relatively greater amounts of
radiomaterials than do older, more slowly grow-
ing individuals. This phenomenon is probably
a reflection of the more rapid metabolism that
accompanies the growth of the younger fishes.
It is not known whether the accumulation of
radiomaterials by other aquatic vertebrates and
invertebrates is a function of age and growth.
i. Effect of temperature on cold-blooded and
luarm-blooded animals
In general, the body temperatures of warm-
blooded animals are more or less constant
whereas the body temperatures of cold-blooded
animals largely depend upon the temperature of
the environment. Similarly, the rate of metab-
olism in warm-blooded animals is generally in-
dependent of temperature changes in the en-
vironment while that in the cold-blooded
animals is largely dependent upon external
temperatures. Changes in temperature affect
the rates of chemical reactions and hence chemi-
cal processes that involve the accumulation of
elements in the body tissues are temperature
dependent.
Generally speaking, all cold-blooded aquatic
organisms exhibit seasonal changes in the up-
take and accumulation of radiomaterials from
the environment. Davis, et al. (1953), and
Krumholz (1954, 1956) have shown that there
is a direct correlation between an increase in
temperature and an increase in the accumulation
of radiomaterials in fishes of the Columbia
River, Washington, and of White Oak Lake,
Tennessee, respectively. This increase in accumu-
lation is apparently a reflection of the increase
in the speed of the metabolic processes with
rising water temperatures. However, Krumholz
(1956) suggested that the fishes in White Oak
Lake entered a period of dormancy following
August 1 and lost about two-thirds of their ac-
cumulated radioactivity during the subsequent
two months even though the water tempera-
tures were much the same as they were during
the earlier part of the summer.
In studies of the uptake of strontium 89 by
76
Atomic Radiation and Oceanography and Fisheries
oysters and other shellfish at the Radiation
Laboratory of the Fish and Wildhfe Service
(Chipman, unpublished data) it was found that
the rate of uptake was slowed down and the re-
tention time was extended when the animals
were kept in sea water at low winter tempera-
tures. Conversely, the rate of uptake was
speeded up and the retention time was short-
ened when the animals were kept at summer
temperatures. In other experiments at the same
laboratory, it was found that larvae of the win-
ter flounder {Pseudopleuronectes americanus)
took up strontium 89 much more rapidly at
higher water temperatures than at lower.
So far as is known, there is no demonstrable
seasonal pattern of accumulation of radioma-
terials among the warm-blooded aquatic verte-
brates. It is generally believed that inasmuch as
the body temperatures of those animals remain
more or less constant throughout the year there
will be no marked seasonal changes in the up-
take of radiomaterials based on changes in rates
of metabolism.
j . Effect of light
Light affects the uptake and accumulation of
radioelements by plants. For example, it has
been clearly shown by Scott (1954) that the up-
take of radiocesium by the algae Fucus and
Rhodymenia was greatly enhanced in the pres-
ence of light.
k. Radiation effects
Many aquatic organisms have the ability to
concentrate radiomaterials in amounts deleteri-
ous to their well-being. These deleterious effects
range from those in which only the individual
is concerned to those in which the population
as a whole may be affected. Elsewhere in this
series of reports there is a paper on the effects
of radiation on aquatic organisms.
Aspects of the accumtdation of radionuclides
through, the ecosystem
For purposes of this paper, the aquatic bio-
sphere can be divided into three trophic levels
based on energy sources :
1. Primary producers, such as the photosyn-
thetic plants.
2. Primary consumers, the herbivores, such as
water fleas (cladocerans) .
3. Secondary consumers, the carnivores, such as
the largemouth bass or the tunas.
The community biomass (the total weight of
all organisms in the community) is unequally
divided between the three trophic levels. Usu-
ally there is a progressive decrease in both the
biomass and the number of organisms from the
first trophic level through the third, and a pro-
gressive increase in the size of the organisms.
However, most community populations are con-
stantly changing and are affected by seasonal,
diurnal, and other cycles of abundance. These
changes frequently have a profound effect on
the environment and any changes in the en-
vironment in turn affect the stability of the
community.
Generally speaking, the smaller organisms
have a higher reproductive potential, a shorter
life span, and a shorter time between genera-
tions ; the length of the life span and the time
between generations usually give a fair indica-
tion of the length of the embryological period.
Furthermore, the smaller animals usually serve
as food for the larger ones.
The discussion will consider the following
aspects of the accumulation of radiomaterials in
the three trophic levels: (1) the distribution
of elements among the three levels, (2) the
concentration factors in different organisms
within the same level, and (3) the transport of
radiomaterials from one trophic level to another.
Problems of the distribution of radionuclides
among the trophic levels and the degree of con-
centration of radionuclides by different organ-
isms can be approached most readily through
separate consideration of the effects from an
acute exposure and those from a chronic ex-
posure.
A steady-state condition will be approximated
when the amounts of radiomaterials introduced
into the environment is equal to the amount
that disappears through physical decay. Any
organisms living in such an environment will
suffer chronic exposure to the radioactivity, the
level depending, of course, on their ability to
concentrate the radiomaterials introduced and
on the steady-state concentration of these ma-
terials in the surrounding medium. An approxi-
mation of the concentration factors for some
organisms is given in Table 4.
Davis and co-workers (1952) showed that
there was a progressive decrease in the amount
of radioactivity found in the aquatic organisms
of the Columbia River downstream from the
Hanford Works. There, the principal radionu-
Chapter 7
Ecology of Uptake by Aquatic Organisms
77
elide was phosphorus 32, which has a physical
half -life of about 14 days. It is apparent that
when following the steady-state transport of
radiomaterials through the ecosystem the follow-
ing parameters must be considered: (1) the
physical half-life of the radionuclide, (2) the
distance of the organism from the source of
radioactive contamination, and (3) the dilution
of the radiomaterials between the point of in-
troduction and the area in which the organism
lives.
The results from acute exposure cannot be as
definitely approximated as for chronic exposure.
In such instances, the time element is very im-
portant, and the following must be known: (1)
the rate of dilution of the radioactive water
mass with non-radioactive water; (2) the rate
of transfer of radiomaterials from one trophic
level to another with the concurrent dilutions
and losses or gains in concentration by the or-
ganisms; and (3) the life span of the organ-
isms involved.
In general, the radiomaterials taken up by
organisms of the first trophic level will be pri-
marily in the ionized state although a certain
amount of particulate radiomaterials will be ad-
sorbed to the body surfaces. When uptake oc-
curs, the rate of uptake will probably be more
rapid than the rate of uptake in the other
trophic levels.
Particulate radiomaterials tend to be concen-
trated in the second trophic level. Findings
from the Wigwam and Castle tests (Goldberg,
unpublished data) showed that the principal or-
ganisms which concentrated particulate radio-
materials were the mucous, ciliary, and pseudo-
podial feeders among the zooplankters. These
organisms contained much more radioactivity
per unit weight than either the algae or the setal
or rapacious feeders.
In addition to the differences in concentration
of radiomaterials from one trophic level to an-
other, there are marked differences among spe-
cies in the same level. For instance, it has been
shown by Chipman, et al. (1953), that some
phytoplankters will concentrate radiostrontium
by a factor of about 20 times whereas others
will concentrate the radioelement by factors as
much as 1500 times. Comparable data have been
recorded by Krumholz (1954) for the accumu-
lation of radiophosphorus by the phytoplankters
of White Oak Lake.
Differences also exist between individuals of
the same species. Very large differences in the
amounts of radiomaterials accumulated by indi-
vidual fishes in White Oak Lake were described
by Krumholz (1956) . For instance, he reported
that the amounts of radiostrontium in the bones
of three bluegills {Lepomis macrochirus') dif-
fered by more than five-fold. These three fish
were taken from the same place in the lake on
the same day, August 27, 1952. Comparable
differences were found in the amounts of ac-
cumulated radiomaterials in most other tissues.
The transfer of radiomaterials from one
trophic level to another is not only dependent
upon the concentration of the radiomaterial in
the organism but also is governed by the rate
of growth of the organism and the rate of in-
crease in the size of the population. These fac-
tors of transfer are of particular importance in
the event of an acute exposure because the dilu-
tion brought about through cell division and
growth may well minimize any radiation effect.
In any event, there is always a loss in the total
amount of radiomaterials in the transfer from
one trophic level to another (though not nec-
essarily a decrease in the concentration in indi-
vidual organisms). Such a loss may be rela-
tively small or it may be very great depending
upon the organism and the particular food web
involved.
Not all radiomaterials that enter the first
trophic level are passed on to higher levels. At
each trophic level there are certain species that,
for one reason or another, are not widely used
as food by the organisms of higher levels. Also,
some of the plants of the first trophic level may
die before they are eaten and thus will be re-
turned to the environment as organic matter.
In this case the primary producers may be of
little or no importance as a source of radioma-
terials to the organisms of the second and third
trophic levels.
If relatively large quantities of radiomaterials
are accumulated in certain hard parts of an or-
ganism, such as the shell of an oyster or the
bones of a fish, they will, in all probability, re-
main in those parts during the greater part of
the life of the animal concerned, and will not
be available to other animals in the biosphere
until the animal dies.
Chipman and co-workers (1953) showed
that oysters fed on Cblorella assimilated only
very little of the radiophosphorus from these
78
Afom/c Radiation and Oceanography and Fisheries
algae. On the other hand, oysters fed upon
other phytoplankters that contained no more ra-
diophosphorus than the Chlorella accumulated
relatively large amounts of radiophosphorus and
incorporated that element into their tissues as
organic phosphorus compounds. It appears that
the particular food web used by any organism
is of primary importance in the transfer of ra-
diomaterials from one trophic level to another.
Problems for further research
One of the fundamental questions to be an-
swered concerns the mechanism of incorpora-
tion of the heavier elements, such as the fission
products, in aquatic organisms. To date, no
metal heavier than molybdenum has been shown
to be necessary for metabolic processes. Spe-
cifically, we need to know:
1. How are the radioactive elements passed
through membranes and where and why do they
concentrate in the organisms ?
2. What are their biological half-lives of the
different radioactive elements in different or-
ganisms ?
3. What are the average and extreme concen-
tration levels of these elements in various or-
ganisms and in the biosphere ?
The revolution in biological thought brought
about by the use of labelled atoms is manifest
in all branches of biological research today.
Radioisotopes have permitted the study of rate
processes that could not have been investigated
in any other way. Such processes include the
pumping rates of water and other biological
fluids, and the transfer of molecules or portions
of molecules from tissue to tissue, or, on the
ecological level, from organism to organism.
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Coffin, C. C, F. R. Hayes, L. H. Jodrey, and
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Davis, J. J., R. W. Coopey, D. G. Watson,
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Chapter 8
LABORATORY EXPERIMENTS ON THE UPTAKE, ACCUMULATION, AND
LOSS OF RADIONUCLIDES BY MARINE ORGANISMS ^
Howard Boroughs, Hawaii Marine Laboratory, University of Hawaii, Honolulu, Hawaii
Walter A. Chipman, Fishery Radiobiological Laboratory,
U. S. Fish and Wildlife Service, Beaufort, North Carolina
Theodore R. Rice, Fishery Radiobiological Laboratory, U. S. Fish and Wildlife Service,
Beaufort, North Carolina
What happens to radioactive materials that are
introduced into the oceans may be studied by a
marine biologist from at least two points of
view. As a physiologist, he will be interested in
the uptake, accumulation, and loss of radioele-
ments as a function of the element, and its con-
centration; in the physical factors of tempera-
ture, light, and salinity; and in differences
between species of organisms, as well as their
age and sex, to mention some of the most im-
portant parameters. As an ecologist, he will be
interested in these same parameters under a
steady-state condition. The physiologist would
profit most by exposure of the organism to a
single dose of radioactive material, while the
ecologist must concern himself with the results
of chronic exposure.
Both types of biologists may be interested in
tracing the history of an element through the
food webs of the various trophic levels. Un-
fortunately, the experimental data involving the
metabolism of radionuclides by marine organ-
isms is extremely meager. In this section some
experiments will be described on the uptake,
accumulation, and loss of radionuclides by vari-
ous marine organisms in the three trophic levels.
It must be emphasized that the results of these
few experiments must be extrapolated with ex-
treme caution in predicting what may happen
to radioactive materials introduced into the
oceans from nuclear reactor plants, bomb deto-
nations, or from any other sources.
^ Work performed at the Fishery Radiobiological
Laboratory of the U. S. Fish and Wildlife Service and
the Hawaii Marine Laboratory (Drs. H. Boroughs,
S. J. Townsley, and R. W. Hiatt).
Contribution No. 95, Hawaii Marine Laboratory.
In discussing the uptake of radionuclides by
marine organisms, it is sometimes difficult to
state exactly what constitutes a single or a
chronic exposure. For a unicellular alga, a few
hours may represent chronic exposure, while a
few weeks may be insufficient for a fish to reach
a steady-state condition. No long-term repeti-
tive feeding experiments have been done, so for
the purpose of this report, we will discuss the
metabolism of the various radionuclides solely
on the basis of the trophic level concerned.
The term uptake implies passage through a
membrane. Radioactive material may be pres-
ent in the gut of an organism, but until it enters
the organism through a membrane, it can play
no role in the metabolism of that organism ex-
cept by producing radiation effects or by inter-
fering with a chemical reaction occurring within
the gut. In some of the experiments to be de-
scribed, particularly those involving phytoplank-
ton, it was not established whether or not the
radioisotope was actually incorporated into the
organism, or merely adsorbed to the surface.
For simplicity, we will therefore discuss uptake
in the sense that the radioisotope is associated
with the organ or organism in question.
Isotopes of a given element usually have
similar chemical behavior, so that in tracing the
path of most elements in biological systems, it
can be assumed that a radioactive atom will be-
have in the same way as a non-radioactive atom
of the same species. The only parameters to be
considered in the discussion to follow will be
the species and age of the organism, the ele-
ment, the concentration of the element, the tem-
perature, and the duration of exposure or treat-
ment. No work using radioisotopes has been
80
Chapter 8
Laboratory Experhnents on Uptake
81
done on the mineral metabohsm of marine or-
ganisms relative to sex. The data that will be
presented were collected either at the Fishery
Radiobiological Laboratory of the United States
Fish and Wildlife Service (R.L.F.W.S.) or
the Hawaii Marine Laboratory, University of
Hawaii (HML).
First trophic level
Experiments performed at the R.L.F.W.S.
very clearly show that different species of
planktonic algae have remarkably different abili-
ties to concentrate a particular element from the
sea water medium. Algae were grown in the
presence of radiostrontium obtained from Oak
TABLE 1 The Differential Uptake of Radio-
active Strontium and Yttrium By Algae
Percentage Percentage
activity activity
from from
Species strontium yttrium
Carteria sp 100.0 0.0
Thoracomonas sp 50.4 49.6
Amphora sp 10.0 90.0
Navicula sp 8.5 91.5
Chromolina sp 8.2 91.8
Chlamydomonas sp 6.5 93.5
Nitzschia dosterium 6.0 94.0
Nannochloris atomus 5.7 94.3
Chlorella sp 5.3 94.7
Porphyridium curentum . . . 4.4 95.6
Gymnodinium splendins . . . 4.1 95.9
Gyrodinium sp 2.3 97.7
Ridge. The material used contained both Sr^^
and Sr«»; the latter decays to form Y^^. By
counting the algal samples immediately after
they were removed from the culture medium,
and again after several weeks, in order to allow
the secular equilibrium of the Sr^^-Y^" pair to
be reached, it was possible to determine what
percentage of the original radioactivity was due
to strontium. Table 1 shows that Carteria sp.
accumulated strontium 89 and 90 from the iso-
topic mixture, and that Gyrodinium sp. removed
almost no strontium 89 or 90, but instead ac-
cumulated yttrium 90. It was found that Nitz-
schia closteriujn under an apparent steady state
condition concentrated strontium 17 times over
its concentration in sea water (weight of algae/
weight of water) . The concentration factor for
strontium Carteria sp. was found to vary with
condition of culture but was much greater than
for Nitzschia dosterium.
Experiments using cesium^^^ show that while
different species concentrate cesium to different
degrees (Table 2) none of the nine species
TABLE 2 Concentration of Cesium By Marine
Algae
Concentration
Algae factor ^
Bacillariaceae
Nitzschia dosterium 1.2
Amphora sp 1,5
Nitzschia sp 1.7
Chlorophyceae
Chlamydomonas sp 1.3
Carteria sp 1.3
Chlorella sp 2.4
Pyramimonas sp 2.6
Nannochloris atomus 3.1
Rhodophyceae
Porphyridium curentum 1.3
1 The concentration factor is reported as the ratio
of Cs"^ in the algae (wet weight) to that in an
equivalent weight of sea water at an apparent steady-
state condition.
tested from three families showed any marked
concentration of this element from sea water.
The effect of the concentration of an element
on its uptake by Nitzschia cells is shown in
Figure 1. Nitzschia cells were grown in sea
water to which had been added labelled zinc at
three different concentrations. From the graph
0. 1 mg./^
• 5 irig./i.
m 80-
40 60
HOURS
Figure 1. Uptake of Zinc®^ by Nitzschia Cells
from Culture Medium Containing Different Concen-
trations of Zinc.
O 0.1 mg./l
O 1 mg./l
• '5 mg./l
82
Atomic Radiation and Oceanography and Fisheries
it is evident that at low concentrations all the
zinc was removed after about four days. The
lowest concentration used was still ten times
higher than the average zinc concentration of
sea water.
The rate of uptake of zinc"^ by Nitzschia
cells is shown in Figure 2. At the normal con-
FiGURE 2. Uptake of Zinc^^ by Nitzschia Cells
from Culture Medium Containing 10 Micrograms of
Zinc/Liter.
centration of zinc in sea water, a dividing cul-
ture of Nitzschia depleted the zinc'^'' in a closed
system in less than one day. Apparently phyto-
plankton cells concentrate zinc relative to sea
water and any radioactive zinc present in the
water will be quickly taken up in large amounts.
The radioisotopes so far discussed are very
likely always ionic in sea water. Ruthenium
solution, however, forms colloids and particles
when put into sea water. Ruthenium^o*^ ob-
tained as an acid solution from Oak Ridge was
added to a sea water culture of Nitzschia cells.
Figure 3 shows that the cells continued to take
up the ruthenium for the 12 days of the experi-
ment. Tlie amount of ruthenium per cell de-
creased, however, since the cells of the culture
were dividing continually. One may conclude
from this experiment, that since the ruthenium
concentration in sea water is low, dividing
planktonic algae would take up large amounts
of any radioactive ruthenium present.
Second trophic level
The work reported in this section was also
done at the R.L.F.W.S. Larvae of the brine
shrimp Artemia were put into filtered sea water
containing radiostrontium and the daughter
16
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1 8
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;^
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Figure 3. Uptake of Ru^*^ by Nitzschia Cultures
in the Light.
yttrium^". These larvae rapidly took up the
SR*^-Sr^°Y^° and reached an apparent steady-
state in a few hours. After exposure of the or-
ganisms to the isotopes for one day, it was
found that the amount of radioactivity /g of
Artemia was only 70 per cent of that of an
equal weight of the sea water. A count of the
samples 30 days after their preparation indi-
cated that a considerable amount of Y°^ was
taken up. Other crustaceans used were the
shrimp Penaeus setiferus and the edible blue
crab Callinectes sapidtis. The molluscan shell-
fish studied included oysters (Crassostrea vir-
ginica), clams (Venus mercenaria), and scal-
lops (Pecten irradians) .
All of these organisms accumulated stron-
tium rapidly from sea water. The internal dis-
tribution of strontium in oysters is shown in
Table 3. This table indicates that the bulk of
the radioactivity accumulates in the shell. When
TABLE 3 Distribution of Radioactivity in
Oysters Following Exposure to Sea
Water Containing Sr-'
Per cent Per cent Per cent
of total of total of soft
Tissues weight activity tissues
Mantle 2.5 4.1 25.0
Gills 1.7 3.1 17.5
Adductor
muscle 1.9 2.4 19-2
Other 3.8 5.1 38.3
Total soft
tissues 9.9 14.7 —
Shell 90.1 85.3 —
Per cent
of
activity
of soft
tissues
27.7
21.2
16.2
34.9
Chapter 8
Laboratory Experi7?7ents on Uptake
83
the radioactive shellfish were returned to a nor-
mal sea water environment, the radioactivity
present in the soft tissues declined within one
day to 10 per cent or less of the maximum con-
centration. This residual amount was held by
the tissues for several days.
The uptake of radiostrontium by oysters from
food was studied by growing Carteria cells in
sea water to which Sr®^ was added. Oysters in
Sr^^ sea water served as the controls ; the treated
oysters were kept in Sr*^ sea water to which the
labelled Carteria cells were added. Fresh sea
water and plankton suspensions were prepared
each day. The curves in Figure 4 show that an
^^^ OYSTERS FED WITH ALGAE
'/ ACTIVITY OF SEA WATER t ALGAE
/ UNFED OYSTERS
ACTIVITY OF SEA WATER
Figure 4. The Increased Accumulation of Sr^^ by
Oysters Feeding on Sr''®-Fed Algae.
apparent steady-state is reached in eight days.
In the unfed oysters the concentration of Sr^^
in the soft parts is approximately the same as
the concentration in the sea water. The oysters
which fed on the radioactive algae, however,
concentrated the Sr^^ by a factor slightly greater
than two, based on the radioactivity of the sus-
pension per unit of weight. These filter-feeding
organisms removed the algal cells from many
volumes of water.
The uptake of cesium^^" by clams, Venus
mercenaria L., is shown in Figure 5. At the
end of 20 days the soft parts of clams had con-
centrated the cesium by a factor of six over the
cesium concentration of sea water. Obviously a
steady state had not occurred, so that it is not
possible to say what the final concentration fac-
tor of clams might be for cesium in solution.
Similar experiments using the bay scallop. Pec-
ten irradians L., show that the concentration
factor of cesium is greater than eight, since the
uptake was still increasing at the end of 10
days.
Figure 5. The Accumulation of Cesium^^^ by Clams
as a Function of Time.
Bay scallops immersed for two hours in sea
water containing Zn^^ very rapidly accumulated
this isotope. Table 4 lists the internal distribu-
tion of zinc*'^ in the various tissues. The con-
centration factor for each organ is readily cal-
culated since the activity of the sea water was
10 m/iC/g. This means that the figures given in
the second column divided by 10 equal the con-
centration factors. The over-all concentration
factor of the soft tissues of the bay scallop was
20 for this short interval. Other observations
showed that these scallops contained close to
35,000y of zinc per gram (wet weight) and
thus had a concentration factor for this element
of about 3500.
Oysters that were kept in sea water with
added Zn^^ also quickly accumulated the iso-
tope to very high levels. The zinc content of
fresh oyster tissue measured almost 170,000y
per gram. This represents a concentration fac-
tor of 17,000, since the zinc concentration of
the sea water in which the oysters lived was
about 10 mcgm/1.
Ruthenium^''^ was one of the separated fis-
sion products used to study the uptake of par-
ticulate radioisotopes by organisms in the sec-
ond trophic level. Ruthenium was co-precipi-
tated with calcium carbonate, dried, and ground
TABLE 4 Distribution of Zn*^ in the Organs of
The Bay Scallop After a Two Hour Immersion
Tissue miic Zn®^/g. Total m/tc
Kidney 1384 824
Liver 243 507
Gills 218 857
Testes and ovaries 138 193
Foot 131 25
Rectum 120 8
Heart 105 13
Adductor muscle 100 375
Mantle 92 321
84
Atomic Radiation and Oceanography and Fisheries
to a very fine state. Plutei of the sea urchin,
Arbacia piinctnlata were put into sea water con-
taining the radioruthenium which was kept in
suspension by aerating the culture flask. After
18 hours, the larvae were rinsed and resus-
pended in fresh sea water. Aliquots of larvae
were then removed at intervals and tested for
radioactivity (Table 5). A microscopic ex-
TABLE 5 The Decrease of Ru^°* in Sea Urchin
Larvae as a Function of Time in
non-radioactive water
Radioactivity in 500
Hours larvae (counts/minute)
1 1413
4 179
8 148
amination of the larvae at zero time showed that
the intestines were filled with the radioactive
particulate material, but at 8 hours, very little
material was left in the gut. Apparently little
ruthenium was actually absorbed through the
digestive tract.
The ingestion of the particulate (co-precipi-
tated) ruthenium by the bay scallop, Pecten
irradians, also indicated that the radioactivity
was mostly associated with the digestive tract.
The crystalline style was highly radioactive, al-
though the radioactivity in it decreased during
the five days the scallops were kept in running
water. The hepatopancreas, on the other hand,
showed an increase in radioactivity during this
time. No radioactivity was found associated
with the internal organs other than those in the
digestive tract.
Third trophic level
The uptake, accumulation, and loss of radio-
nuclides has been studied in many fishes by
both the R.L.F.W.S. and the H.M.L. These
fishes include the skipjack tuna {Eiithynnus
yaito), yellowfin tuna {Neothnnntts macrop-
terus), dolphin {Coryphaena hip punts'), papio
{Carangoides ajax), aholehole (Kuhlia sand-
vicensis) , Tilapia mozamhique , menhaden {Bre-
voortia tyratinus), bluefish {Pomatomus salta-
trix) , little tuna (Euthynnus allitteratus) , croak-
ers (Micropogon undulatus) , and king whiting
{Menticirrhus sp.) .
At the H.M.L., strontium^^ in gelatine cap-
sules was fed to skipjack, dolphin, and yellowfin
tuna. These are all fast-swimming pelagic fish.
Figure 6 shows that the excretion of strontium
is very rapid. In 24 hours, only about two per
cent of the dose remains in the fish. Similar ex-
periments with Tilapia, a small, sluggish bottom
feeder, indicate that the strontium is also mainly
excreted, but that the time required to reach a
minimum level of about five per cent of the
dose requires at least four days. This informa-
tion is consistent with the idea that the meta-
bolic rates of these fishes are very much dif-
ferent, and the sluggish fish might be expected
to retain the strontium for longer periods.
HOURS AFTER DOSE
Figure 6.
The Percentage Accumulation by Tuna
Fish of Sr'" Given Orally.
The internal distribution of the total radio-
activity recovered is shown in Table 6. By
plotting the radioactivity of each organ against
time, it is apparent that the soft, visceral tissues
rapidly excrete the strontium, but that the bony
structures, gills, integument, and muscles re-
tain the strontium for a long period. Tilapia
show the same behavior. The data are presented
in Table 7.
The direct uptake of strontium*^ in solution
by Tilapia was also studied at the H.M.L. Fig-
ure 7 shows that after about two weeks, the
Figure 7. The Uptake of Sr^" in Solution by
Tilapia Mozambique.
Chapter 8
Laboratory Experiments on U ptake
85
TABLE 6 Accumulation of Sr^" in the Various Organs and Tissues of Tuna After Ingestion
Percentage of total activity
Dose:
5.55MC
Tissue 1 hr
Heart 0.04
Gall bladder 0.05
Blood 4.21
Gill flesh \i2 AA
Gill bone j
Caecum 37.01
Foregut 0.89
Midgut 2.28
Hindgut 11.78
Gut contents —
Head, operculum . . —
Appendicular skel. . 3.60
Liver 3.34
Spleen 0.20
Tail —
Brain, spinal cord. .1 ^ ,,
Eyes .. I 0-23
Integument 5.28
Integument flesh . . —
(aliquot)
Integument scales . —
(aliquot)
Gonad I 2.40
Kidney J
Light muscle \ i r ?^
Dark muscle ....
Dose:
Dose:
Dose:
Dose:
480|iic
240/iC
51.0/xc
lAOixc
21 hr
6hr
7hr
llihr
0.01
0.03
0.049
0.11
0.04
0.07
0.10
0.08
6.68
15.00
0.85
8.07
J 0.18
11.34
0.91\
6.47 f
8.56
f 5.06^
126.39/
7.67
7.84
2.70
2.64
9.32
1.12
0.74
1.03
14.16
16.50
1.08
1.48
3.98
21.26
2.26
0.11
48.32
12.73
0.056
19.65
0.41
1.09
24.99
6.28
0.40
1.19
36.21
8.45
1.48
3.04
0.39
2.46
0.32
1.39
0.08
0.60
0.42
0.15
—
0.00
fo.oo
\0.04
O.Oll
0.06J
1.24
ro.o5i
\o.6o;
1.69
0.86
10.20
5.89
0.01
0.01
—
0.05
0.02
0.09
0.08
3.23
0.10
0.02
0.47
0.16
8.74
0.86
— 0.11
0.22
4.19
5.25
.08
.09
10.01
0.70
Dose:
464^c
24 hr
0.05
0.03
2.73
0.34
0.20
0.65
0.15
18.33
23.69
0.15
0.03
Dose:
AGAjxc
96 hr
0.028
0.0001
1.14
30.61 25.72
0.15
0.24
0.25
0.024
0.10
24.58
30.32
0.04
0.008
1.66 1.70
7.69 11.37
/0-08| 0.06 f
\0.09/ \0
12.84
0.72
004
027
3.94
0.48
Dose:
464/iC
264 hr
0.01
0.01
0.35
2.42
16.80
0.05
0.04
0.05
0.03
0.013
28.18
29.15
0.03
0.03
Dose:
371^0
480 hr
0.014
0.004
0.51
1.42
19.48
0.04
0.04
0.036
0.015
29.91
30.47
0.04
0.010
0.03
0.07
5.26
0.47
0.023
0.035
5.69
0.63
Dose:
371MC
648 hr
0.007
0.002
0.12
2.21
22.76
0.029
0.018
0.003
0.016
0.0008
24.58
31.43
0.027
0.003
1.33 0.030 0.004
2.02 1.34 1.34
13.73 10.25 10.51
— — 0.065
0.091
0.020
0.022
5.79
0.95
TABLE 7 The Internal Distribution and Per-
centage Recovery of a Dose of 75 mc of Sk^^
By Tilapia
Days after
dose
Tissue
.Skin
Eyes
Visceral organs
Gills
Muscle
Skeleton
Total
.Skin
Eyes
Visceral organs
Gills
Muscle
Skeleton
Total
.Skin
Eyes
Visceral
Gills
Muscle
Skeleton
Total
organs
Percentage
of total
recovered
25.27
0.35
1.82
15.62
5.65
51.30
100.01
24.44
0.18
1.08
8.13
3.10
63.07
100.00
24.56
0.25
1.01
6.42
8.40
59.35
99.99
Days after
dose
TABLE 7 — Continued
Tissue
.Skin
Eyes
Visceral organs
Gills
Muscle
Skeleton
Percentage
of total
recovered
22.79
0.33
1.14
10.11
3.01
62.62
Total
100.01
uptake apparently levels off at a value which
corresponds to a concentration factor of about
0.3. This means that these fish can to some
extent exclude the strontium ion in solution.
Even the skeleton had not yet come to equi-
librium with the radioactivity in the sea water.
This may mean that only about 70 per cent of
the strontium in the bone is readily exchangea-
ble. The remainder may be firmly bound in a
lattice or to an organic matrix which has a slow
rate of turnover. It should be emphasized that
these fish were mature.
Experiments done at the R.L.F.W.S. with
Sr*^ on post-larval flounders indicate that age
86
Atomic Radiation and Oceanography and Fisheries
and temperature influence the uptake of ele-
ments in solution. One group was kept at
20-22° C in sea water containing Sr*^^, and
another group at 8-12° C. The fish in both
groups averaged 0.02 g. each. Figure 8 shows
Figure 8. Uptake of Sr*" by Larval Flatfish.
that strontium was taken up more rapidly at
the higher temperature. Thus at one day, the
fish at the lower temperature had less than one
third of the radioactivity of the fish at the
higher temperature. The graph also shows that
very young fish continue to take up strontium
from solution very rapidly at 14 days, while at
14 days the Tilapia had reached an apparent
steady state condition.
The uptake of zinc^^ by croakers was studied
at the R.L.F.W.S. These fish were fed the iso-
tope in hardened gelatine. After 12 hours only
about 27 per cent of the dose remained in the
fish (Table 8). The distribution of zinc is
quite different from that of strontium. About
90 per cent of the strontium retained by the
various fishes used at the H.M.L. was found in
the gills, bones, and integument. Zinc, how-
ever, is concentrated mainly in the liver and
spleen. The muscle and bone, because of their
bulk accounted for a large part of the total
zinc^^ of the body. The turnover times of the
zinc-containing compounds of the skin, muscle
and bone were slow, whereas those of the in-
ternal organs were relatively rapid.
The uptake of radiocesium by fish was studied
at the R.L.F.W.S. Table 9 shows the distribu-
tion of cesium^^'^ which was fed to little tuna.
It can be seen that the liver, heart, spleen, and
kidney rapidly take up the cesium, but these
organs also lose the cesium during the following
week. Muscle, gonad, brain, and skin, on the
TABLE 8 ZiNc"^ Distribution in Croakers
{Micro pogon undulatus) 12 HouRS After
Oral Administration
^ S -S g a. 3 C O"^
1 issue or u,-^ «ju; cP'C'Ut^'-io.is
rgan a."" ^°" NNfi.
Muscle 80 48.80 1.6 78.1 44.7
Bone 11 6.71 5.5 36.9 21.1
Gills 2 1.22 10.9 13.3 7.6
Liver 0.8 0.49 40.7 19.9 11.4
Gonads 0.4 0.24 17.6 4.2 2.4
Kidney 0.3 0.18 41.5 7.5 4.3
Heart 0.2 0.12 14.0 1.7 1.0
Spleen 0.1 0.06 25.3 1.5 0.9
Remainder . . 5.2 3.17 3.7i 11.7 6.7
Skin, scales
G I tract 60.99 174.8
Blood
Brain
Eyes
etc.
1 Based on skin and scales
Dose per fish — 6,100 myuc
Distribution after 12 hours
Tissues 3 percent
G I tract 24 percent
Loss 73 percent (mostly excreted)
Other hand, continue to accumulate the cesium
faster than they lose it.
The accumulation of cesium in solution was
demonstrated by keeping croakers in Cs^^" en-
riched sea water. The water was changed daily
to maintain a relatively constant concentration.
Figure 9 indicates that during the 29 days, the
heart, spleen, liver, brain, and muscle con-
tinued to accumulate the cesium. The concen-
tration factor for the heart, spleen, and liver,
was about 10, but this value is far below an
equilibrium value.
TABLE 9 The Distribution of Cesium^^^ in the
Tissues of the Little Tuna as a
Function of Time
Cs^^' content in /ic/g. wet wt.
Days after the dose
Organ 1
Spleen 3-46
Liver 9.07
Kidney 3.13
Heart 6.17
Bone 0.41
Eye 0.30
Muscle 0.46
Gonad 0.54
Brain 0.30
Skin 0.29
3
6
8
3.29
3.22
1.57
4.71
3.45
2.59
2.58
1.78
0.95
3.15
2.52
1.57
0.40
0.17
0.26
0.26
0.31
0.30
0.67
0.87
0.79
0.70
1.33
1.34
0.35
0.69
0.66
0.46
0.41
1.01
Chapter 8
Laboratory Experiments on Uptake
87
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/ ^ .^^^^^
U
1 X .^^^
2
n
[ y ^^^"^ SEA WATER CONCENTRATION
12 16 20
DAYS OF EXPOSURE
Figure 9. Accumulation of Cs"^ by Croakers Kept in
Sea Water Containing 5 X 10"* Microcuries/Ml.
The relative concentration of cesium by the
various organs is roughly the same for croakers,
tuna, or bluefish. The same rank order among
the organs is maintained both from ingestion,
and from direct uptake.
Menhaden, a filter feeder, were put into sea
water with ruthenium^o** that had been co-pre-
cipitated with calcium carbonate. Although a
considerable amount of particle settling oc-
curred, the menhaden took up the ruthenium in
the digestive tract, but the tissues of the fish did
not become radioactive to an appreciable extent.
Similar experiments using menhaden fed with
Ruio6 labelled Arbacia plutei, or Ru^o" labelled
Nannochloris cells, gave parallel results. In the
latter experiment the fish were allowed to eat
the labelled cells for four hours, and then they
were put in running sea water. At the time of
transfer about 92 per cent of the ingested dose
was found in the digestive tract. The gills had
0.64 per cent of the dose, and the remainder of
the fish, including the skin, had 0.76 per cent.
At 128 hours, only 0.05 per cent of the ingested
dose remained in the digestive tract. There was
0.25 per cent in the fish body or on the skin
surface, and 0.01 per cent in or on the gills.
At no time was there an appreciable increase in
the radioactivity of the body of the fish.
Chapter 9
ACCUMULATION AND RETENTION OF RADIOACTIVITY FROM FISSION
PRODUCTS AND OTHER RADIOMATERIALS BY FRESH- WATER
ORGANISMS^
Louis A. Krumholz, Department of Biology, University of Louisville, Louisville, Kentucky
and
Richard F. Foster, Biology Operation, Hanford Laboratories, General Electric Company,
Richland, Washington
Introduction
Relatively little is known about the mech-
anisms of uptake, concentration, retention, and
excretion of fission products and other radio-
materials by fresh-water organisms. These or-
ganisms include many biological forms such as
the vascular plants, algae and phytoplankton,
protozoans, zooplankton and other invertebrate
forms, and representatives of each of the five
vertebrate classes.
The complex interrelationships of the fresh-
water biota, together with their diverse indi-
vidual anatomies, physiological processes, and
life histories indicate the enormous scope of the
problem of determining the role of radioma-
terials in the metabolic processes of such a
community. In addition, there is extreme ur-
gency for obtaining information on many as-
pects of this problem within a relatively short
period of time. Within the next 10 years sev-
eral power-producing reactors will undoubtedly
be in operation ; many placed, in all probability,
near the large industrial and/or population
centers of the United States where the only
ready means of disposal of large quantities of
liquid effluent will be into fresh waters. Any
near-by rivers and lakes may be subject to
rather severe contamination by radioactive ma-
terials in the event of accidents.
Owing to the complex interactions of the
factors involved, any estimates of the levels of
radioactive contamination that may occur in a
particular situation may be in error by as much
as one or two orders of magnitude. For purposes
of hazard control, estimates must therefore be
1 Contribution No. 10 (New Series) from the De-
partment of Biology, University of Louisville.
based on pessimistic assumptions with the hope
that field sampling and experimentation will
reveal a more desirable situation.
An estimate of the worst situation can be ob-
tained by comparing the concentration of a par-
ticular element in the water with its concentra-
tion in an organism or tissue under study. Since
the radioisotope of the element will behave in
much the same manner as its stable counterpart
(for purposes of this paper), there will be no
greater concentration of the radioisotope than
of the stable form.
Sources of information
At the present time there are three primary
sources of information available regarding the
uptake, concentration, retention, and excretion
of radiomaterials by fresh-water organisms.
They are:
1 . The long-term program of the Biology Labo-
ratories of the General Electric Company at
Richland, Washington. This program has been
primarily concerned with the accumulation of
radioactive materials in the flora and fauna of
the Columbia River. The effluent water released
to the Columbia from the plutonium-producing
reactors at the Hanford Operation contains ra-
dioelements induced when the "impurities" in
the cooling water pass through the high neutron
flux. The Hanford program was designed as a
radiological-ecological study with four main ob-
jectives: (1) to determine the geographical dis-
tribution of the radioactive materials, (2) to
find out how the radioisotopes became dis-
tributed in the various kinds of aquatic organ-
isms from the phytoplankton on through the
fishes and, to some extent, to the land animals
88
Chapter 9
Uptake by Fresh-water Organisms
89
which feed on fresh- water organisms, (3) to
study the seasonal distribution of the radioac-
tive materials throughout the biota, and (4) to
determine whether the aquatic forms were ad-
versely affected.
2. A three-year study at the Oak Ridge Na-
tional Laboratory, Oak Ridge, Tennessee. That
work was performed by the Fish and Game
Branch, Division of Forestry Relations, Ten-
nessee Valley Authority, under contract to the
Atomic Energy Commission and consisted pri-
marily in an ecological survey of White Oak
Creek and its drainage area. In that study,
principal emphasis was placed on the effects on
the biota and its environment from radioma-
terials that consisted of both fission products
and wastes with induced radioactivity from the
processing of different materials in the prepara-
tion of radioisotopes.
The Ecological Survey of White Oak Creek
was divided into three main categories: botany,
limnology, and vertebrate biology (Krumholz,
1954). Because of a virtual absence of rooted
aquatic plants in the area, the fresh-water bi-
ology was largely covered in the studies on
limnology and vertebrate biology. That program
was designed to find out what radiomaterials
had accumulated in the biota of the drainage
area, in which organisms and tissues they had
accumulated, and what, if any, had been the
effects of such levels of accumulation on popula-
tion balances and on the various types of indi-
vidual organisms.
3. Many studies of lesser magnitude carried on
at other installations of the Atomic Energy
Commission and at different colleges and uni-
versities throughout the United States. Such
studies usually are not integrated with one an-
other but are separate studies designed to an-
swer specific questions.
Rather intensive studies of the phosphorus
cycle in fresh-water lakes have been carried out
by workers at Dalhousie University (Coffin, et
al., 1949, and Hayes, et al., 1952), at Yale Uni-
versity (Hutchinson and Bowen, 1950), and
at Atomic Energy of Canada, Ltd. (Rigler,
1956) . These studies have increased our knowl-
edge of the role of phosphorus in the economy
of fresh-water lakes, particularly at the lower
trophic levels. Much work has also been done
on the economic aspects of such aquatic insects
as the mosquitoes (Bugher and Taylor, 1949;
Hassett and Jenkins, 1951) and also on such
aquatic forms as the frog (Hansborough and
Denny, 195 1 ) . These animals have been tagged
with radioisotopes (usually radiophosphorus)
either by direct feeding of substances which
contained the radioactive material, or by im-
mersing them in radioactive solutions.
Concentration of radioactive materials in aquatic
organisms
-^ ■ r (Mc/g of organism)
The concentration factor ' , — ; — ^ -
^c/ml of water
for any radioelement cannot exceed the ratio
between the normal concentration of that ele-
ment in the organism and the concentration of
the element in the surrounding water. Thus, if
the element in question is not normally used by
a particular organism, it is unlikely that any of
the radioisotopes of that element will be con-
centrated in the tissues.
Each organism in each environment has spe-
cific requirements for the different chemical
elements. However, it is necessary to know the
chemical composition of the organism and its
parts, as well as that of its aquatic environment,
in order to understand those requirements and
to interpret the role played by each element in
the metabolic processes. At present, there is
very little information available on the chemical
composition of any of the fresh-water organ-
isms or their tissues, and consequently there is
virtually nothing known of the concentration
factors to be expected for the different elements
by the organisms. Some data on the chemical
composition of fresh-water lakes and streams
are available, but these waters differ so widely
from one another that no generalizations can
be made. The total dissolved solids in fresh
waters range from less than five parts per mil-
lion to well over 400 parts per million. In
addition, the elements which make up these
dissolved solids seldom occur in exactly the
same percentage composition in any two bodies
of fresh water. The concentration of any par-
ticular element in the water is directly depend-
ent upon the chemical characteristics in the
drainage area. Because of these differences in
the requirements of organisms and in the chemi-
cal compositions of the different fresh waters,
it is necessary to consider each situation as a
separate case.
An indication of the differences in the orders
90
Atomic Radiation and Oceanography and Fisheries
TABLE 1 Concentration (Ppm Wet Weight) of Some Elements in Selected Organisms and in
Some Major Rivers of the United States
Organism i Water 2
, ^ "• ^
Algae Insect larvae Fish , a ^
Element (Spirogyra) (Caddis fly) (Minnows) Low High
Silicon 1,500 20 10 3 20
Iron 6,500 300 1 <0.01 6.0
Calcium 1,500 300 3,000 2 200
Phosphorus 250 2,000 6,000 <0.001 1.5
Strontium 2 0.2 0.3
Sodium 1,500 700 1,000 1 200
These values are only estimates of orders of magnitude. They are recorded here to illustrate differences
which can exist and are not intended for use in precision work.
1 Values are from unpublished results obtained by spectrophotometric analysis at the Hanford Laboratories.
2 Abstracted largely from Moyle (1956) and Clark (1924).
of magnitude of the concentrations of a few of
the common elements in some organisms and in
water is shown in Table 1. However, the con-
centrations of particular elements in specific
structures or tissues of those organisms may
deviate widely from those values. For instance,
the concentration of calcium as calcium car-
bonate in the shells of some molluscs or that of
silicon in the siliceous tests of some diatoms
may be greater than the listed values by more
than one order of magnitude.
Field studies in the Columbia River at the
Hanford Operation and in White Oak Lake at
the Oak Ridge National Laboratory have pro-
vided an opportunity to study the uptake and
accumulation of a variety of radioactive ma-
terials by organisms in those waters under
natural conditions. Omitting those radionuclides
which have half-lives shorter than ten hours,
there are measurable amounts of Na^*, Cr^^,
Cu*'*, F^-, As'^^, and rare earths in effluent
from the Hanford reactors. The composition of
the wastes from the Oak Ridge National Labo-
ratory varies from day to day but there are rela-
tively large amounts of Sr«», Sr^o-Y^o, Cs^",
Ce^**-Pr^**, Ru^f"', and other fission products
present at all times. In addition, there are rela-
tively large amounts of other radionuclides such
as P^~ and Co''*' present on occasion. In spite
of this large variety of radionuclides available
to the organisms of these two aquatic communi-
ties, only a few appear to be utilized to any
great extent. Observed concentrations of the
radionuclides most frequently used by the or-
ganisms through their natural food webs in
the Columbia River and White Oak Lake are
listed in Table 2. From these data it is evident
that some elements are utilized in much greater
quantities than others. Rather large variations
occur from one collecting site to another and
between species, however. For example, the
concentration factor for P"- in filamentous algae
of White Oak Lake is hsted as 850,000. This
figure is for a sample from a large mat of
Spirogyra that lie on the bottom near the upper
end of the lake. In other parts of the lake
Spirogyra contained less radiomaterial. Fur-
thermore, radioactivity in other filamentous
algae, such as Oedogoniinn, was consistently
lower than for Spirogyra. Comparable differ-
ences in the amounts of radioisotopes accumu-
lated by the different phytoplankton and insect
larvae were also found.
Very few data have been published which
indicate the importance of the physical and
chemical states of the various elements in the
TABLE 2 Estimated Concentration Factors for Various Radionuclides in Aquatic Organisms as
Observed From Field Studies on the Columbia River and White Oak Lake
Radionuclide Site
Na^ Columbia River
Cu"* Columbia River
Rare Earths Columbia River
Fe^" Columbia River
P'^ Columbia River
F' White Oak Lake
Sr'^-Y™ White Oak Lake
Filamentous
Insect
Phytoplankton
algae
larvae
Fish
500
500
100
100
2,000
500
500
50
1,000
500
200
100
200,000
100,000
100,000
10,000
200,000
100,000
100,000
100,000
150,000
850,000
100,000
30,000-70,000
75,000
500,000
100,000
20,000-30,000
Chapter 9
Uptake by Fresh-ivater Organisms
91
physiological processes of fresh-water organ-
isms. Coffin, et al. (1949) and other workers
have shown that a large fraction of the P^-
which was added to fresh-water lakes under
natural conditions was quickly fixed in the bot-
tom sediments where it was essentially unavaila-
ble to the organisms. Thus it is apparent that
elements which are introduced into an environ-
ment as insoluble or tightly fixed compounds,
or become parts of such compounds shortly
after their introduction, may be of little or no
use to the organisms even though the particu-
lar element involved normally enters into their
metabolic processes.
Another factor in the concentration of radio-
materials by fresh-water organisms about which
there is only limited information available is
the effect of the presence of one chemical on
the uptake of another. For example, it was
Methods of accumulation of radiomaterials by
organ is 7ns
Radiomaterials may become associated with
fresh-water organisms in one of three ways:
(1) through adsorption to surface areas, (2)
through absorption from the surrounding me-
dium, or (3) through ingestion as food. The
first of these methods is primarily a physical
process whereas the last two are largely bio-
logical in nature and make up an integral part
of the physiological processes necessary for the
metabolism of the population.
In some instances, especially in those organ-
isms which have a large surface-to-volume ra-
tio, adsorption to surfaces is very important. For
example, Foster and Davis (1955), working
with organisms from the Columbia River,
showed that the amounts of radioactivity in
TABLE 3 Absorption of Various Elements from Solution By Fresh-water Fish
Element Organism
Strontium Goldfish
Barium-Lanthanum Goldfish
Sodium Goldfish
Calcium Guppy
Probable
concentration
factor
150
150
30
1000
Investigator
Prosser, et al., 1945
Prosser, et al., 1945
Prosser, et al., 1945
Estimated from Rosenthal, 1956
shown by Prosser and co-workers (1945) that
the amount of calcium present in the water af-
fected the amount of strontium taken up by
goldfish; as the amount of calcium was in-
creased, the uptake of strontium decreased.
The amount of a radionuclide taken up by an
aquatic organism is dependent not only upon
the concentration of the nuclide in the water
(microcuries per milliliter) but also upon its
specific activity.^ As the specific activity is de-
creased by increasing the concentration of "car-
rier" over a certain range, the stable form of the
element becomes more readily available to satisfy
the requirements of the organism, and the
amount of radioisotope taken up by the organ-
ism will generally decrease. Such isotopic dilu-
tion has a non-linear relationship, however, and
may be ineffective in instances where low con-
centrations occur (Whittaker, 1953; Kornberg,
1956).
1 Specific activity as used here refers to the ratio be-
tween the amount of radioisotope present and the
total amount of all other isotopes, both radioactive
and stable, of that same element.
sponges and diatoms remained comparatively
high at a season when the amounts of radio-
activity in other organisms were quite low.
All of the nutrient materials, and thus the
biologically important radioisotopes, that are
metabolized by plants are absorbed directly from
the environment (Rediske, Cline, and Selders,
1955). Direct absorption of a few radionu-
clides by fresh-water organisms has been ob-
served under laboratory conditions. Gross es-
timates of concentration factors which appear
to have occurred in these studies are listed in
Table 3. For the most part, these are short-
term tests in which the particular test organism
was immersed in the radioactive solution. En-
tirely different values would result if the organ-
ism had also acquired the isotope through the
food web.
The principal mode of accumulation of ra-
diomaterials by fishes is through ingestion. Ol-
son (1952) found that young trout which had
been immersed in dilute effluent from the Han-
ford reactors failed to concentrate radiophos-
phorous, whereas similar fish, which were fed
92
Atomic Radiation and Oceanography and Fisheries
organisms that had been grown in the effluent,
accumulated substantial amounts of P^-. Fish
living in the Columbia River downstream from
the reactors and which fed on organisms that
had assimilated the radioactive materials con-
tained over 100,000 times more radiophos-
phorus than the surrounding water during the
late summer. Krumholz (1954, 1956) at-
tributed the high concentrations of Sr^° and
Csi37 in the fishes of White Oak Lake to the
ingestion of contaminated food organisms. In
addition, it was shown that the different kinds
of animals which served as food for the fishes
accumulated different amounts and kinds of ra-
diomaterials. For instance, although a high per-
centage of the radioactivity in the food organ-
isms, such as larval Chaohorus, emanated from
radiophosphorus, only a relatively small portion
of the radioactivity in the fish was traceable to
that radioelement. Similarly, although only a
relatively small amount of radioactivity in the
plankton organisms was attributable to Sr^",
about 80 per cent of the radioactivity in the fish
skeleton emanated from that radioisotope. From
these findings it is apparent that the ability of
the various organisms in the food web to con-
centrate the different radionuclides is of the ut-
most importance to the predatory species. If
the animals which serve as food were unable to
take up the radiomaterials, there would be con-
siderably less chance of the predators becoming
contaminated.
The food habits of fishes and other fresh-
water organisms determines, to a great extent,
which radioelements they may accumulate. In
a study of the food habits of the black crappies
and the bluegills of White Oak Lake (Krum-
holz, 1956) it was found that the diets of those
two species were considerably different. Marked
differences also occurred in the concentration
and relative proportions of the radiomaterials
in the tissues of the two kinds of fish. Greater
amounts of radiomaterials were concentrated in
the soft tissues of the bluegills than in the
crappies, and greater amounts of radiomaterials
were concentrated in the skeleton and other
hard parts of the crappies than in the bluegills.
Furthermore, there were relatively greater
amounts of radiophosphorus in the bones of
the bluegills and relatively greater amounts of
radiostrontium in the bones of the crappies.
These differences may well have resulted from
the dissimilar diets or, perhaps, from diflferent
physiological demands. Unpublished data of
the Hanford Laboratories shows that 50 to 75
per cent of the radiophosphorus ingested by fish
is assimilated and retained. Unfortunately,
there is virtually no other information available
on the efficiency of transfer of radioisotopes
from food organisms to aquatic predators.
Concentration of radioactive materials in dif-
ferent organisms
In unpublished results from the studies at
White Oak Lake, it was shown that bacteria
may have the greatest powers for concentrating
radiomaterials of any of the fresh-water organ-
isms, their concentration factors for certain iso-
topes may exceed 1,000,000. However, it is
not definitely known for all radionuclides
whether or not they actually enter into the
metabolism of the bacteria or are adsorbed to
surface areas. Labaw, Mosley, and Wyckoff
(1950) showed that the measured radioactivity
in Escherichia coli, which had been cultured on
a medium that contained P^^ ^^s Na2HP*04),
was not due to adsorption of the P^^ on the
bacterial surfaces nor to residues from the radio-
active culture.
The data from the Columbia River and White
Oak Lake indicate that the phytoplankton usu-
ally concentrate greater amounts of radiomateri-
als than the zooplankton. Here, again, it is not
known for all species whether the radiomateri-
als actually enter into the metabolism or are
adsorbed to surfaces. Some of the filamentous
algae are known to concentrate P^- at least
850,000 fold (Krumholz, 1954), whereas for
other algae the concentration factor may be as
little as 300,000. Some zooplankton have con-
centration factors for radiophosphorus of as
much as 250,000 but in others it may be less
than 100,000.
Fresh-water invertebrates of all classes studied
in the Columbia River and White Oak Lake ex-
hibited maximum concentration factors which
ranged from less than 100 to more than 100,-
000 depending on the radioelement involved.
It is believed that most of the radioactive ma-
terials accumulated actually enter into the me-
tabolism of these invertebrates. Some of the
insect larvae concentrate radioelements by fac-
tors upwards of 100,000; some of the micro-
crustaceans by factors of nearly 200,000; some
mollusks may concentrate fission products as ef-
Chapter 9
Uptake by Fresh-water Organisms
93
fectively, if not to a greater extent, than some
crustaceans. This may be especially true for
those long-hved isotopes which are incorporated
into the shell.
The length of exposure to water that con-
tains radioisotopes will also greatly affect the
concentration in different organisms. The con-
centration of isotopes in phytoplankton and
other micro-organisms will reach equilibrium
with the water in a relatively short period of
time. For radiophosphorus, this is estimated at
about 15 hours (Whittaker, 1953). The larger
animals, such as fish, will approach equilibrium
much more slowly, however. Coffin, et al.
(1949) found that radiophosphorus introduced
into an acid bog lake did not appear in the fish
until two days later. Several weeks of chronic
exposure to an environment containing long-
lived, bone-seeking isotopes is undoubtedly
necessary before maximum concentrations will
result in large fish.
Variations with season, age, and growth
So far as is known, all cold-blooded fresh-
water organisms exhibit seasonal changes in the
assimilation of radiomaterials through metabolic
processes. There is a direct correlation between
an increase in temperature and an increase in
the accumulation of radiomaterials through
metabolic processes in the invertebrates and
fishes of the Columbia River (Foster and Davis,
1955) and the fishes of White Oak Lake
(Krumholz, 1954, 1956). However, in White
Oak Lake it was found that the amounts of ra-
diomaterials in all fish tissues decreased mark-
edly after August 1, even though the tempera-
tures at that time were similar to those during
the early summer when there was a rapid in-
crease in the accumulation of radioactive ma-
terials. This may well be a suggestion that some
warm-water fishes enter a period of estivation
or summer dormancy. A decline in radioactivity
of Columbia River organisms during the winter
months correlates with cessation of feeding.
No seasonal pattern of change in the ac-
cumulation of radiomaterials has been demon-
strated for any of the warm-blooded aquatic
vertebrates, but this may well occur. It is
known, for example, that the V-^'^ content of
rabbit thyroid glands changes markedly with
the season (Hanson and Kornberg, 1955).
Among the fishes, it has been established by
Olson and Foster (1952) that the younger,
more rapidly growing individuals accumulate
relatively greater amounts of radioactivity than
the older, more slowly growing ones. This
phenomenon is probably a reflection of the more
rapid anabolism that accompanies the growth
of younger fish. It is not known whether any
of the other fresh-water vertebrates or inverte-
brates exhibit this same phenomenon.
Any accumulation of radioactive materials in
an organism is subject to biological dilution.
Such dilution results from cell division and
growth. It is especially manifest in rapidly
growing organisms and is particularly notice-
able following an acute short-term exposure to
the radiomaterials.
Retention and elimination
Radioisotopes will be deposited and retained
in the organisms according to the physiological
behavior of the particular element involved.
Highly mobile isotopes, such as tritium, may be
eliminated in a matter of minutes or hours
(Foster, 1955), but certain bone-seekers, such
as strontium or phosphorus, may be so tightly
fixed that little loss occurs, except by radioac-
tive decay, during the life of the organism. The
metabolism of the radiophosphorus in trout has
been studied by Hayes and Jodrey (1952) and
by Watson (Hanford Laboratories, unpub-
lished). Little information is available on the
metabolism of other isotopes in other aquatic
animals, however.
The recognized methods of elimination of
radiomaterials are: (1) through surface ex-
change, (2) excretion through the natural
physiological channels, (3) through moulting
where this occurs, and (4) through death. In
any of these processes of elimination, the radio-
materials are released into the environment and
can be immediately taken up by other organ-
isms.
Discussio)2
Based on our present knowledge, there can
be no broad statement to the effect that "aquatic
organisms will concentrate radioactivity in their
tissues." Rather, each individual situation must
be appraised separately in the light of the fol-
lowing basic considerations which are concerned
with the accumulation of radiomaterials by
fresh-water organisms: (1) the particular ele-
94
Atomic Radiation and Oceanography and Fisheries
ment involved and its physiological importance
to the organism, (2) the physical and chemical
state of the element and its acceptability to the
organism, (3) the concentration of the element
in the environment and the presence of other
elements which may inhibit or enhance its up-
take, (4) the morphology of the organism, its
life history, and its particular role in the food
web, and (5) the physical and chemical char-
acteristics of the environment.
Even though the great majority of research
with radionuclides in biological fields has been
performed within the past 15 years, enough
data have been gathered to serve as a basis for
the following general statements.
1 . Radioactive materials are taken into the body
of an organism either through physiological
processes and incorporated directly into the tis-
sues or they are attached to the surfaces of the
organisms through adsorption.
2. The concentration of certain radioelements
reaches a higher level in many of the lower
plant and animal forms, such as bacteria, pro-
tozoa, and phytoplankton, than in higher forms,
such as the vertebrates. In such instances, there
is an inverse correlation between the complexity
of body structure and the concentration of the
radioelement in question.
3. Certain plants and animals have a predilec-
tion for concentrating specific radionuclides in
different tissues. For instance, iodine is con-
centrated in the thyroid tissue, silicon is con-
centrated in the tests of some diatoms, calcium
.is concentrated as calcium carbonate in the
shells of some mussels and as calcium phos-
phate in others, calcium and phosphorus are
also concentrated in the bony skeletons of ver-
tebrates, phosphorus in concentrated as adeno-
sine triphosphate in the flight muscles of some
birds, and potassium and other elements are
concentrated in wide variety of tissues.
4. Although certain radioelements may occur in
amounts acceptable for drinking water, many
fresh-water organisms have the ability to con-
centrate them to levels which would be harm-
ful. Such deleterious effects could range from
those in which only the individual organism is
involved to those in which the entire popula-
tion may be affected.
Little information is available on the toler-
ances of the various aquatic organisms to dif-
ferent radioactive materials. Recently, however,
D. G. Watson at the Hanford Laboratories has
determined that a concentration of 65 /i,c P^^
per gram of bone was lethal to trout in about
six weeks. A concentration of 10 /xc P^- per
gram was not lethal in 12 weeks but caused
some radiation damage. This series of experi-
ments is only the first step toward determining
the tolerance levels for all radionuclides in each
of the animals of the fresh-water fauna.
The use of radiomaterials as a research tool
in fresh-water biology has opened new fields
which were almost impossible to explore ade-
quately by other means. Determination of the
metabolism of many of the elements essential
for proper nutrition is now possible. Further-
more, the effects of the radioactivity emanating
from isotopes deposited in the tissues can be
studied. In the field of fresh-water biology, per-
haps the greatest benefits from the use of radio-
active materials can be derived from studies of
the physiological processes of the organisms.
REFERENCES
BuGHER, J. C, and Marjorie Taylor. 1949.
Radiophosphorus and radiostrontium in
mosquitoes. Preliminary report. Science
110:146-147.
Clark, F. W. 1924. The composition of the
river and lake waters of the United States.
U. S. Geol. Survey, Prof. Paper 135.
Coffin, C. C, F. R. Hayes, L. H. Jodrey, and
S. G. Whiteway. 1949. Exchange of ma-
terials in a lake as studied by the addition
of radioactive phosphorus. Canad. Jour.
Research D. 27:207-222.
Davis, J. J., R. W. Coopey, D. G. Watson,
C. C. Palmiter, and C. L. Cooper. 1952.
The radioactivity and ecology of aquatic
organisms of the Columbia River. In Bi-
ology Research — Annual Report, 1951.
USAEC Document HW-2502 1:19-29.
Foster, R. F., and J. J. Davis. 1955. The
accumulation of radioactive substances in
aquatic forms. Proceedings of the Inter-
national Conference on the Peaceful Uses
of Atomic Energy, 13 (P/280) : 364-367.
Foster, R. F. 1955. Tritium oxide absorption
and retention in the body water of some
aquatic organisms. In Biology Research —
Annual Report, 1954. USAEC Document
HW-35917:98-100.
Chapter 9
Uptake by Fresh-water Organisms
95
Hansborough, L. a., and D. Denny. 1951.
Distribution of phosphorus^- in the em-
bryo and larva of the frog. Proc. Soc.
Exptl. Biol. Med. 78 A?)! -441.
Hanson, W. C, and H. A. Kornberg. 1955.
Radioactivity in terrestrial animals near an
atomic energy site. Proceedings of the In-
ternational Conference on Peaceful Uses
of Atomic Energy, 13 (P/281) :385-388.
Hassett, C. C, and D. W. Jenkins. 1951.
The uptake and effect of radiophosphorus
in mosquitoes. Physiol. Zool. 24:257-266.
Hayes, F. R., J. A. McCarter, M. L. Came-
ron, and D. A. Livingstone. 1952. On
the kinetics of phosphorus exchange in
lakes. ]ot/r. Ecol. 40:202-216.
Hayes, F. R., and L. H. Jodrey. 1952. Utili-
zation of phosphorus in trout as studied by
injection of radioactive phosphorus.
Physiol. Zoology 25:134-144.
Hutchinson, G. E., and V. T. Bowen. 1950.
Limnological studies in Connecticut. IX.
A quantitative radiochemical study of the
phosphorus cycle in Linsley Pond. Ecology,
31:194-203.
Kornberg, H. A. 1956. Effectiveness of iso-
topic dilution. In Biology Research — An-
nual Report, 1955. USAEC Document
HW-41 500: 19-28.
Krumholz, L. a. 1954. A summary of the
findings of the ecological survey of White
Oak Creek, Roane County, Tennessee,
1950-1953. USAEC Document ORO-132:
1-54.
1956. Observations on the fish population
of a lake contaminated by radioactive
vv^astes. Bull. Am. Mus. Nat. Hist. 110
(4) :277-368.
Labaw, L. W., V. M. MosLEY, and R. W. G.
Wyckoff. 1950. Radioactive studies of
the phosphorus metabolism of Escherichia
coli. Jour. Bacteriol. 59:251-262.
MoYLE, J. B. 1956. Relationships between the
chemistry of Minnesota surface waters and
wildlife management. /. Wildl. Mgt. 20:
303-320.
Olson, P. A., Jr. 1952. Observations on the
transfer of pile effluent radioactivity to
trout. In Biology Research — Annual Re-
port, 1951. USAEC Document HW-
25021:30-40 (OFFICIAL USE ONLY).
Olson, P. A., Jr., and R. F. Foster. 1952.
Effect of pile effluent water on fish. In
Biology Research — Annual Report, 1951,
USAEC Document HW-25021:4l-52.
Prosser, C. L., W. Pervinsek, Jane Arnold,
G. SviHLA, and P. C. Thompkins. 1945.
Accumulation and distribution of radioac-
tive strontium, barium-lanthanum, fission
mixture and sodium in goldfish. USAEC
Document MDDC-496:l-39.
Rediske, J. H., J. F. Cline, and A. A. Seeders.
1955. The absorption of fission products
by plants. In Biology Research — Annual
Report, 1954. USAEC Document HW-
35917:40-46.
RiGLER, F. H. 1956. A tracer study of the phos-
phorus cycle in lake water. Ecology 37:
550-562.
Rosenthal, H. L. 1956. Uptake and turnover
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571-574.
Whittaker, R. H. 1953. Removal of radio-
phosphorus contaminant from the water in
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search—Annual Report, 1952. USAEC
Document HW-28636: 14-19.
Chapter 10
EFFECTS OF RADIATION ON AQUATIC ORGANISMS
Lauren R. Donaldson, Applied Fisheries Laboratory, University of Washington,
Seattle, Washington
and
Richard F. Foster, Biology Operation, Hanford Laboratories, General Electric Company,
Richland, Washington
I. Somatic Effects of Ionizing Radiation
The effects of ionizing radiations on marine
and fresh-water organisms have been studied by
a few investigators since the early part of the
century. The total volume of such work can
by no means compare with that which has re-
sulted from the intensive studies with more con-
ventional laboratory animals. The value of much
of the early work is impaired by inadequate or
imperfect dosimetry. Nevertheless a sufficient
block of information has been accumulated to
permit several generalizations and at least some
well-defined conclusions.
A. Relative sensitivity of different organisms
A broad review of the results obtained with
the organisms of different phyla indicates that
the lower or more primitive forms are generally
more resistant to ionizing radiation than are the
more complex vertebrate forms. Welander (un-
published data) has summarized much of the
data for which some approximation of dose can
be made. Table 1 is a further condensation of
these data which were obtained in experiments
where whole body doses (usually X-rays) were
administered. Owing to the great variety of
circumstances under which the experiments
were conducted, these data represent only orders
of magnitude of effects.
The algae and protozoa are most resistant
with LD50 values in the order of many thou-
sands of roentgens. The molluscs and crusta-
ceans are somewhat more sensitive, with LDgg
values of a few thousand roentgens (aquatic in-
sects probably also fall in this category) and
the fish are most sensitive with an LD50 of
about one thousand roentgens — in the same
TABLE 1 Relative Sensitivity of Different Groups of Organisms to Radiation
(r)
Dose which caused
Group
Algae . .
507o mortality
8,000-100,000
Protozoa 10,000-300,000
Molluscs
Crustaceans
Fish
Insects 1 . .
5,000- 20,000
500- 90,000
600- 3,000
100% mortality
25,000- 600,000
10,000-
5,000-
370-
50,000
80,000
20,000
1 No data except for Culex and non-aquatic forms.
"Latent'
45 days
18,000-1,250,000 45 min.-40 days
period Investigators
Bonham and Palumbo (1951);
Crowther (1926) Bonham, et
al. (1947).
Ralston (1939); Back (1939);
Back and Halberstaedter
(1945); Halberstaedter and
Back (1943); Powers and
Shefner (1950); Feldman-
Muhsam and Halberstaedter
(1946).
3 weeks-2 years Bonham and Palumbo (1951).
5 days-80 days Bonham and Palumbo (1951).
14-460 days Corbella (1930) ; Welander et al.
(1948); Foster et ah (1949);
EHinger (1939) (1940);
Ssamokhvalova (1938); Sol-
berg (1938).
96
Chapter 10
Radiation of Aquatic Organisms
97
order of magnitude as that of other cold-
blooded vertebrates.
B. Relative sensitivity of different stages of
development
It must be recognized in any consideration of
the relative sensitivity to radiation of different
groups of organisms that considerable varia-
bility exists between similar species. In com-
paring the sensitivity of two species of snails,
Bonham and Palumbo (1951) found that "at
10 kr, approximately one month elapsed before
50 per cent of the Radix died, while in the case
of the Thais it was approximately one-half of a
later stages of development. Unpublished work
by Welander has shown the most radiation-
sensitive period of silver salmon {Oncorhyn-
chus kisutch) egg development to be a par-
ticular stage during the mitosis of the single
cell. For the most sensitive period an LD50 o^
only about 16 roentgens was observed.
The change in sensitivity between different
stages of development has also been shown with
snails. Bonham and Palumbo (1951) showed
that eggs of the fresh- water snail Radix japonica
were more sensitive to radiation than the adults.
Further studies of snails (Helisoma subcre-
TABLE 2 Relative Sensitivity of Different Life Stages of Salmonoids
Stage
irradiated Species
Gametes ^ rainbow trout
Eyed eggs chinook salmon
Fingerlings chinook salmon
Adult rainbow trout
1 In parent fish.
year." Consideration must also be given to the
different developmental stages of the same spe-
cies. Since many investigators (Evans, 1936,
Rugh, 1949) have correlated radiosensitivity
with metabolic rate of the dividing cell, it is not
surprising that dormant eggs of aquatic inverte-
brates should be especially resistant. Bonham
and Palumbo (1951) found that the two-week
LD50 for dry Artemia eggs was about 50,000
roentgens, but after soaking the eggs for a short
time in water, so that embryonic development
was resumed, the radiosensitivity increased more
than twofold.
A review of the results of exposing salmo-
noid gametes, eggs, fingerlings or adults to
X-radiation supports the early concepts (Butler,
1936) that radiosensitivity decreases with age.
Table 2 shows that the LD50 values range from
50-100 roentgens for gametes within the parent
fish to about 1500 roentgens for adult trout.
Welander (1954) studied in detail the effects
of X-rays on different embryonic stages of rain-
bow trout. His results with these aquatic forms
confirmed the work of Russell and Russell
(1954) and others working with mammals that
certain critical periods exist during which the
embryo is most sensitive to radiation. Table 3
shows some of Welander's data.
Trout eggs were much more sensitive to ra-
diation during the one-cell stage than during
Approximate
median effective
dose (LD50)
50- 100 r
1000 r
1250-25001
1500 r
Investigator
Foster, et al. (1949)
Welander, et al. (1948)
Bonham, et al. (1948)
Welander, et al. (1949)
natum) eggs by Bonham (1955) showed that,
in the one- and two-cell stages, resting eggs
withstood from two to four times as much radia-
tion as cells undergoing mitosis, and that later
embryonic stages were less sensitive.
C. Pathology of radiation damage
1. Different organs
While effects of exposure to larger amounts
of radiation than that sufficient to cause death of
the organism have been studied by many investi-
gators, few have studied in detail the physical
and pathological syndromes of damaging but
non-lethal exposures to radiation.
Retardation in the rate of growth of snails ex-
posed to radiation has been reported by Bon-
TABLE 3 Relative Sensitivity of Different
Embryonic Stages of Trout to
X-Irradiation 1
Median eflfective does (LD50)
Stage irradiated At hatching
One-cell 78.3 r it 4.42
Thirty-two cell.. 468 r ± 19-4
Early germ ring . . 524 r ±: 22.1
Late germ ring. . 735 r ± 24.7
Early eye —
Late eye —
1 After Welander (1954).
2S_.
At end of yolk
stage
57.8 r± 3.82
313
r± 12.4
461
r± 15.9
454
r ± 19.4
415
r±22.0
904
r±38.5
98
Atomic Radiation and Oceanography and Fisheries
ham and Palumbo (1951). Growth in length
and weight of fish exposed to radiation is re-
tarded as compared to control populations (We-
lander et al., 1949).
"The growth increment during the fastest
growing period of the experiment was signifi-
cantly less in a fish irradiated with 750 r or more
of X-radiation and proved to be a very sensitive
measurement of radiation damage and directly
proportional to the amount of radiation given."
The effects of X-radiation upon growth are
not confined to the exposed population. Foster
et al. (1949), reporting on the growth of rain-
bow trout fingerlings produced from parent
stock exposed to radiation prior to spawning,
comment :
"The rate of growth of the young during
their first year of life was also found to be di-
rectly affected by the amount of irradiation re-
ceived by the parent fish. While variations in
mortality became less with increasing age of the
fish, variations in size became greater. Parents
treated with 100 r produced progeny in which
growth was slightly impeded, while parents
treated with 500 or more r units produced
progeny which grew appreciably more slowly
than normal."
Damage to specific organs and tissues of sal-
monoid fish as a result of exposure to X-ra-
diation has been studied by the staff of the
Applied Fisheries Laboratory, University of
Washington.
Adult rainbow trout exposed to X-radiation
prior to spawning were examined for gross ra-
diation damage (Welander et al., 1949). The
typical syndromes of radiation such as mass
hemorrhage, petechiae and ecchymosis have
been observed in all trout subjected to 1500
and 2500 roentgens. Gonadal hemorrhage was
observed in fish exposed to 500 r of total body
radiation. Exposures of 750 r resulted in hem-
orrhagic areas in the peritoneum, while all ex-
posures of 1000 r or more produced muscular
hemorrhage.
The eggs of rainbow trout exposed to radia-
tion during early developmental stages (We-
lander, 1954) produced fish showing retarded
development. The eggs exposed during the 32-
cell, late germ ring and early eyed stages tended
to have a more juvenile appearance than the
controls, viz., a larger eye and head in propor-
tion to the size of the body. Other modifications
evidenced in the young produced from radiated
eggs were as follows:
"The number of parr marks was significantly
reduced in all stages after doses of 300 r or
more, with doses as low as 25 r significantly
altering the number in embryos irradiated dur-
ing the 32-cell stage.
"Reduction in number of dorsal and anal fin
rays was general after irradiation of 32-ceIl, late
germ ring and early eyed embryos. Doses from
75 to 100 r were significantly effective in re-
ducing the fin ray number in these stages.
"Gross superficial abnormalities observed in
X-rayed trout were similar, though usually more
numerous, to those found in the controls, with
the exceptions of anomalies of dorsal and adi-
pose fin produced by 200 and 400 r X-rays of
32-cell embryos."
The eggs of chinook salmon {Oncorhynchus
tshaivytscha) exposed to X-radiation during the
eyed stage with the results reported by We-
lander et al. (1948), show somatic damage pro-
portional to the amount of exposure.
Histopathological studies on serial sections of
the kidneys, with included hemopoietic tissue,
the interrenal bodies, the spleen, the gonads
and other organs of chinook salmon embryos
and larvae revealed first the gonads, then the
hemopoietic tissue as most radiosensitive.
Exposure of the eyed eggs to 250 r greatly
reduced the number of primordial germ cells in
the gonads of the chinook salmon. This sharp
reduction (Table 4) in number of cells at 250 r
would indicate a measurable reduction at a
much lower radiation exposure.
The hemopoietic tissue of the anterior por-
tion of the kidney of the chinook salmon pro-
duced from eggs exposed to 250, 500 and 1000
r showed a reduction in number of cells and a
temporary retardation in development, roughly
proportional to the dose. Temporary cessation
of mitosis at 1000 r and permanent cessation at
higher radiations was noted.
Counts of the glomeruli in the kidneys of
young fish indicated a slight reduction in num-
bers at 500 r with definite damage at exposures
of 1000 r (Table 5).
In general, it is observed that the tissues most
sensitive to radiation damage are those in rapid
division and growth. Gonadal and hemopoietic
tissues that are in rapid division are many times
more sensitive than those growing less rapidly.
The very early embryonic stages of an organism
Chapter 10 Radiatioti of Aquatic Organisms 99
TABLE 4 Counts of the Primordial Germ Cells rainbow trout chronically fed P^- died in ap-
iN THE Gonads of Chinook Salmon Compared proximately 6 weeks when the concentration of
By Days After Exposure and By Dosage i ^^^ -^^^^p^ j^ ^^^^^ ^^^ ^i^^^^ ^^ maximum up-
Exposed fish take, reached a level of 18 to 65 iic/g (giving
kradiation Tr" %'50 r 500 r 1000 r a dose of about 1200 rads per day). Other
9 33 42 25 27 trout remained alive during the 12 weeks' ex-
16 46 31 64 27 periment with concentrations of P^- in the bone
23 32 35 108 39 ^s high as 10 fic/g. Although these fish showed
, , 28 42 ^"^ external evidence of radiation damage other
44 ^ 32 124 79 71 than a slight reduction in growth rate, subse-
51 453 83 65 53 quent dissection revealed that some damage
58 2,085 287 55 25 h^d occurred. The syndrome was similar to that
^5 1'058 683 286 47 described for trout damaged by X-irradiation,
79 6,569 380 131 67 • i, .u u i j c ^u i
03 7 206 247 94 69 especially the breakdown or the vascular system
— as evidenced by hemorrhage of the liver and
Average 1,595.4 182.6 89.2 43.1 musculature.
1 Counts of over 1,000 r were arrived at by first In experiments that have taken place at Eni-
making total counts on all five-micron sections and j^ ^^j g-j^j^j ^^^jj^ ^^^ resulting radio-
calculating the actual number or germ cells present us- 1 1 n
ing the average size of the ceil nucleus (9.2 microns) active materials that entered the water usually
and actual cell counts of the other fish as a basis. In provided three types of exposure to the aquatic
cases where every fifth section only was used (as in ^ . ,, v _ r j-u^ _ j.-^i-:^^ ^o^^
the 65th, 79th and 93rd day series) actual counts were organisms: (1) some of the radiation came
obtained by multiplying original counts by five and from contamination of the environment, (2)
then correcting for size of the cell nucleus. Data from particulate matter, such as Specks of radioactive
Welander et al. (1948). \ ^ ■ r. ..i j • ju J <-^
debris often settled on organisms or adhered to
J. ^. .,• ., .. „ „, 1 ^ _^ mucus coverings, etc., or (3) the radioactive
are more radiation sensitive than the older, ma- ., °,' ' .^ ' . ,,, rj
r materials entered the organism through the tood
Tit i.iuj rci-fj- chain where it was absorbed and incorporated
In all respects, the damage effects of radia- '-"'^i" vvi .. .. ,•■,,,,, *^ i
. r . • -1 -J .-• 1 ^ *.u^ f into the organism or eliminated by the usual
tion in fish are similar or identical to the et- ' & ^
facts seen in other vertebrate animals. In gen- biological processes. , ,. .
eral, the syndromes have a similar pattern Although vast amounts of radiation may be
throughout the animal kingdom depending on P^-^sent immediately following a weapons test,
the dose amounts that surely would produce measurable
2. Relative susceptibility of organs to ra- changes in the exposed aquatic forms no spe-
dioactive material ^^^'^ instances were found in which direct so-
For most experiments with aquatic organ- matic damage could be charged to radiation
isms conducted to date radiation from external effects.
sources has been used. In the work of Chipman It must be realized that in as complex an en-
(1955) and Hiatt, Boroughs, Townsley, and vironment as a coral atoll following the fate of
Kau (1955) radiation from isotopic sources in individual populations is very difficult. The
the body was used, but at such low levels so- most sensitive forms, the fishes, undoubtedly are
matic damage was not evident. weakened from somatic and functional damage
The uptake of lethal levels of P^^ is being by radiation. Such weakened forms are usually
studied by Watson (unpublished data) . Adult eaten soon by the large carnivorous fishes that
TABLE 5 Counts of the Glomeruli in the Kidney of Chinook Salmon Larvae After Irradiation
in Eyed Egg Stages ^
Days
Dose ,
inr 23 30 37
0 12 36 42
250 2 38 16
500 8 16 38
1000 0 26 28
1 After Welander et al. (1948), counts on 36 fish.
44
51
58
65
79
93
Average
60
66
98
122
174
282
99.1
41
48
86
144
186
288
94.3
40
51
86
96
162
260
84.1
25
AG
2
70
6A
120
42.3
100
Atomic Radiation and Oceanography and Fisheries
move into an affected area or, if not picked up
at once following death, they decay so rapidly
in the warm tropical waters as to be undetecta-
ble in a few hours, thus escaping notice.
II. Somatogenic Effects of Ionizing Radiation
If we consider genetic effects in the strict
sense of damage to chromosomes or genes, to
the extent the modified characteristics are passed
from one generation to the next, there is little
to be found in the published literature describ-
ing work on marine or fresh-water forms. Some
effects on aquatic forms have been described,
however, where gametes were exposed to radia-
tion prior to zygote formation. The effects in
such cases are due, at least in part, to somatic
which died during the incubation period con-
tained conspicuously abnormal embryos. The
abnormalities could be attributed to deficiencies,
improper differentiation of cell masses, dispro-
portionate growth, or combinations of these fac-
tors. Abnormal types of embryos occurred
among the progeny of control parents and of
parents which had received low doses of radia-
tion which were almost identical with the types
which occurred among the progeny of parents
receiving large amounts of radiation. However,
as the amount of radiation increased the relative
abundance of malformed embryos increased and
the degree of development attained decreased.
Practically all of the embryos from parents
treated with 1500 r and 2500 r were so ab-
TABLE 6 Effect on Trout Eggs from Irradiating the Parent Fish ^
(Values are per cent of eggs which died at each stage)
Number of r units received by parents
Stage of ,, A _ ,
Development 0 50 100 500 750 1000 1500 2500
No embryo 18.5 32.2 23.0 24.4 42.6 41.5 68.1 83.6
Blastoderm 0.8 0.3 3.2 5.9 0.6 3.2 2.9 4.5
Embryonic axis 4.3 4.6 4.3 8.2 21.1 29.5 22.1 11.5
Blastopore closed 1.0 4.4 3.7 23.6 22.5 15.5 5.5 0.3
Eyed 6.3 9.1 16.2 8.6 3.5 2.1 0.3 0.1
Hatching 8.7 11.4 10.1 14.5 6.3 6.3 0.9 0
Total 39.6 62.0 60.5 85.2 96.6 98.1 99-8 100
1 Data from means (unpublished) of figure 1 from Foster et al. (1949).
damage but will be considered here because they normal that they died before closure of the
represent some changes which may occur in oflF- blastopore. Irradiation of the parent fish thus
spring of irradiated parents. increased the frequency of occurrence of malfor-
The classical work of Henshaw and his col- mations."
leagues with the eggs and sperm of the sea Table 6 illustrates that egg mortality was di-
urchin Arbacia demonstrated that X-radiation rectly related to the dose received by the parent
of the gametes delayed the first cleavage. Ef- fish and that the degree of development ob-
fects of X-rays on gametes of fish have received tained by the embryo decreased at the higher
some attention. In spite of massive doses of exposure levels.
X-rays — 100,000 to 200,000 r — (Rugh and Irradiation of gametes prior to "fertilization"
Clugston, 1955) to the eggs and sperm of is, of course, not the only means of producing
Fundulus heterocUtus, fertihzation can take abnormal embryos with ionizing radiation. We-
place and some embryonic development is pos- lander (1954) found that abnormalities in-
sible although this may be parthenogenic from creased with dose among trout embryos irradi-
irradiated sperm. Solberg's (1936) work with ated at the 32-cell and early eyed stages. The
Oryzias indicates that spermatozoa are three to production of phenocopies has been tentatively
four times as sensitive to radiation as ova, how- established. Welander, as stated earlier, found
ever. Foster (1949) found that that trout irradiated with 200 and 400 r at the
"The mean mortalities of the eggs obtained 32-cell stage had abnormal dorsal and adipose
from parents subjected to 500 or more roentgen fins. Such anomalies arising from irradiation of
units were significantly greater than that of the cleavage stages would appear to result from a
eggs from the control parents. Most of the eggs disturbance of the precursors.
Chapter 10
Radiation of Aquatic Orgajtisms
101
III. Other Considerations in Atomic Energy
Use
When potential effects of atomic energy in-
stallations upon aquatic life are considered, ra-
diation damage resulting from the release of
radioactive isotopes is probably the primary con-
sideration. Conventional types of pollutants
must not be overlooked, however. Indeed, the
chemical toxicity or high temperature of effluent
released into a stream or lagoon could well be
of greater concern than the radioactive materi-
als. Olson and Foster (1955) have reported
that very high concentrations of effluent from
the Hanford reactors are toxic to young salmon
and trout, not because of the radioactive iso-
topes present, but because of the presence of
dichromate. Krumholz (1954) states that:
"The waste effluent which enters White Oak
Creek consists of a heterogeneous mixture of
chemical wastes resulting from laboratory, pilot-
plant, and full-scale operations. Some of these
wastes are radioactive and some are not."
Since a variety of toxic substances is apt to
be present in effluent from atomic energy plants,
just as from other types of industry, care should
be taken in appraising biological observations.
If adverse effects on aquatic populations are ob-
served, one should not immediately conclude
that these are a result of radiation damage
when, in fact, they may well result from altered
chemical or temperature conditions.
Serious radiation damage to aquatic popula-
tions is certainly possible, however, under cat-
astrophic or emergency conditions. It could
also occur where there is continued release of
inordinate amounts of isotopes which are con-
centrated in the organisms. Such damage ap-
pears unlikely, however, in situations where
adequate radiation hazard control is extended to
the environs of an atomic energy facility. Such
control must go well beyond the sole considera-
tion of maximum permissible concentrations
for drinking water. Foster (1955) has pointed
out that:
"If radiophosphorus were allowed to reach
the maximum level permitted for drinking
water, organisms living in the water would suf-
fer radiation damage and the fish would be un-
safe for human food."
If contamination in the fish and in other
edible forms is to remain at a level which is safe
for human beings, however, the radiation dose
received by the organisms may not be intolerable
to the organisms themselves. For example, the
International Committee on Radiation Protec-
tion recommends maximum permissible concen-
trations (MFC) for V^- in drinking water of
2 X 10-* fxc P^- per cc, equivalent to an in-
take of about 3 ixc P^- each week. If MFC's
were based on a nominal consumption of one
pound of fish per person each week, and an
additional safety factor of 10 were applied ow-
ing to the large populations involved, then the
MFC for edible parts (flesh) of the fish would
be 7 X 10"* /tc F32 per gram. This is only about
one per cent of the concentration which Watson
(unpublished data) found to be sub-lethal to
trout in a 12-week period (although some ra-
diation damage did occur). It seems unlikely,
therefore, that significant damage would result
to fish if the concentration of P^- in the flesh
remained below 10-^ ju,c/g.
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Back, A., and L. Halberstaedter. 1945. In-
fluence of biological factors on the form
of roentgen-ray survival curves. Experi-
ments on Raramecimn caudatum. Am. J.
Roentgenol. Radium Therapy 54:290-295.
BoNHAM, Kelshaw. 1955. Sensitivity to
X-rays of the early cleavage stages of the
snail Helisoma subcrenatum. Growth
XIX:9-18.
BoNHAM, Kelshaw, and Ralph F. Palumbo,
1951. Effects of X-rays on snails, Crusta-
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BoNHAM, Kelshaw, Allyn H. Seymour,
Lauren R. Donaldson, and Arthur D.
Welander. 1947. Lethal effect of X-rays
on marine microplanton organisms. Sci-
ence vol. 106, no. 2750.
Butler, E. G. 1936. The efifects of radium and
X-rays on embryonic development. In,
Biological Effects of Radiation, ed. B. M.
Duggar, McGraw-Hill Book Co., Inc.,
N. Y., pp. 389-410.
Chipman, W. a. 1956. Passage of fission
products through the skin of tuna. Fish
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port— Fisheries no. 167.
CoRBELLA, E. 1930. Influsso delle radiazioni
Roentgen sullo svilluppo embrionale dei
Teleostei (Salmo lactistris L., Sabno iri-
deus Gibb., Perca fluvialilis L.) Riv. Biol.
Milano 12:93-117.
Crowther, J. A. 1926. The action of X-rays
on Colpidium colpoda. Proc. Roy. Soc.
London, Ser. B, 100, 390-404.
Ellinger, F. 1939. Note of action of X-rays
on goldfish {Carassius auratus) . Proc. Soc.
Exp. Biol. 41:327-9, 2 figs.
Evans, T. C. 1936. Qualitative and quantita-
tive changes in radiosensitivity of grass-
hopper eggs during early development.
Physiol. Zool. 9:443-454.
Feldman-Muhsam, B., and L. Halberstaed-
TER. 1946. The effect of X-rays on Lei-
schmania tropica in vitro. Brit. J. Rad. 19
(217):4l-3.
Foster, Richard F., Lauren R. Donaldson,
Arthur D. Welander, Kelshaw Bon-
ham, and Allyn H. Seymour. 1949. The
effect on embryos and young of rainbow
trout from exposing the parent fish to
X-rays. Groivth XIII: 119-142.
Foster, Richard F., and J. J. Davis. 1955.
The accumulation of radioactive substances
in aquatic forms. Proceedings of the Inter-
national Conference on Peaceful Uses of
Atomic Energy, 13(P/280) :364-367.
Halberstaedter, L., and A. Back. 1943. In-
fluence of colchicine alone and combined
with X-rays on Paramecium. Nature (Lon-
don) 152 (3853):275-276.
Henshaw, p. S., and D. S. Francis. 1936.
The effect of X-rays on cleavage in Ar-
hacia eggs: evidence of nuclear control of
division rate. Biol. Bull. 70:28-35.
Hiatt, Robert W., Howard Boroughs, Sid-
ney J. TowNSLEY, and Geraldine Kau.
1955. Radioisotope uptake in marine or-
ganisms with special reference to the pas-
sage of such isotopes as are liberated from
atomic weapons through food chains lead-
ing to organisms utilized as food by man.
Ann. Rept., Hawaii Mar. Lab., U. of
Hawaii.
Krumholz, Louis A. 1954. A summary of
findings of the ecological survey of White
Oak Creek, Roane County, Tennessee,
1950-1953. USAEC Doc. ORO-132.
Olson, P. A., and R. F. Foster. 1955. Re-
actor effluent monitoring with young Chi-
nook salmon — 1954. In Biology Research,
Ann. Rept. (1954), Biol. Sec, Radiol. Sci.
Dept., General Electric, Hanford Atomic
Products Operation (USAEC Doc. HW-
35917) :11-18.
Powers, E. L., and D. Shefner. 1950. Effects
of high dosages of X-rays in Paramecium
aurelia. Genetics 35:131.
Prosser, C. L., C. W. Hagen, Jr., and W.
Grundhauser, 1948. The lethal action
of X-radiation, stable isotopes of fission
elements Sr ®^ and (Ba-La)'*° upon gold-
fish. (USAEC Doc. ANL-4017).
RuGH, R. 1949. Some prenatal effects of Am-
hly stoma opacum larvae exposed to 25,000
f X-radiation. Anat.Rec. 103:500-501.
RuGH and Clugston. 1955. Effects of various
levels of X-irradiation on the gametes and
early embryos of Fundulus beteroclitus.
Biol. Bull. 108 (3): 3 18-25.
Russell, L. B., and W. L. Russell. 1954. An
analysis of the changing radiation response
of the developing mouse embryo. ]our.
Cell. Com p. Physiol. 43:(Suppl. 1), 103-
149.
SoLBERG, A. N. 1938. The susceptibilty of
Fundulus beteroclitus embryos to X-radia-
tion. Jour. Exp. Zool. 78-A41-469.
SSAMOKHVOLOVA, G. W. 1938. Effect of
X-rays on fishes (Lebistes reticulatus,
xiphophorus hellerii and Carassius vul-
garis) Biol. Zh. Moscow 7:1023-1034.
Watson, D. G. 1956. Effects of feeding
chronic levels of P^- to rainbow trout (un-
published data).
Welander, Arthur D., Lauren R. Donald-
son, Richard F. Foster, Kelshaw Bon-
ham, and Allyn H. Seymour, 1948.
The effects of roentgen rays on the em-
bryos and larvae of the chinook salmon.
Growth ^l\:{-5), 203-242.
Welander, Arthur D., Lauren R. Donald-
son, Richard F. Foster, Kelshaw Bon-
ham, Allyn H. Seymour, and Frank G.
LowMAN. 1949. The effects of roentgen
rays on adult rainbow trout. (USAEC
Doc. UWFL-17).
Welander, Arthur D. 1954. Some effects
of X-irradiation of different embryonic
stages of the trout {Salmo gairdnerii) .
Growth XVIII:227-255.
Chapter 11
ISOTOPIC TRACER TECHNIQUES FOR MEASUREMENT OF PHYSICAL
PROCESSES IN THE SEA AND THE ATMOSPHERE^
Harmon Craig, Scripps Institution of Oceanography, University of California,
La Jolla, California
I. Introduction
Throughout this report reference has been
made to the need for a fundamental understand-
ing, on a long-term basis, of mixing phenomena
in the ocean and the atmosphere. In a general
sense the ocean and the atmosphere may be re-
garded as a two-phase system, in which the
phases are separated by the fundamental dis-
continuity of the ocean-atmosphere interface.
Each phase is further divided into two parts by
a second order discontinuity; the atmosphere,
divided by the tropopause at about 12 km, into
the troposphere and the stratosphere, etc., and
the oceans, divided by the thermocline at some
100 meters, into an upper and lower layer.
The basic problems in determining the effects
of both radioactive waste disposal and the dis-
persal of debris from nuclear explosions may be
formulated in terms of a single objective. Given
the ocean-atmosphere system under normal
steady state conditions, and given some sub-
stance introduced at any point in one of the
four designated zones, we wish to be able to
predict quantitatively the concentration of the
substance as a function of latitude, longitude,
altitude or depth, and time. These problems
thus involve studies of (1) the intra-phase mix-
ing, above, below, and across the second-order
discontinuities within each phase, and (2) the
inter-phase mixing across the ocean-atmosphere
interface, with the aim of predicting the effects
of perturbations on the system.
The dominant mixing processes in the vari-
ous spheres are processes of mass movement or
turbulent mixing. In such processes, for ele-
ments undergoing no change of phase, there is
little or no separation of components, and thus,
in general, isotopic tracer techniques may in-
1 Contribution from the Scripps
Oceanography, New Series, No. 902.
Institution of
volve a wide range of materials of quite differ-
ent chemistry. It is this phenomenon of mass
movement dominance, and the relative unim-
portance of diffusive transfer except in special
cases, that makes the tracer technique so power-
ful; a tagged isotope for each element is not
required, and one can choose for each particular
study the elements most useful for tracing the
movement of a mass of heterogeneous material.
As mentioned at several points in this report,
both artificial and natural isotopic tracers may
be used for the study of transfer phenomena in
the sea and the atmosphere. Artificial tracers
are of value in such studies because they allow
the investigator to introduce perturbations in
the system at convenient times and places; they
are especially valuable for the study of short
term fluctuations in local systems. However, for
the general understanding of mass transfer phe-
nomena, artificial tracers are of value mainly as
experimental checks on deductions based on
other data, with the exceptions of a few special
cases to be described below. The reason for this
is that mass transfer phenomena are by nature
subject to long term periodic fluctuations such
as convection, with periods often longer than
the time range available for observation. A sec-
ond reason for this is the high cost of radioiso-
topes and the large amounts of activity required
to tag adequately the large masses of water nec-
essary for ocean studies.
Revelle, Folsom, Goldberg and Isaacs (1955)
have discussed in their Geneva report the prob-
lems involved in adapting radioisotope tracer
techniques to transfer studies in the ocean, and
the requirements for usable isotopes. If one
introduces some 10 curies of a gamma emitter
in solution at some point below the thermocline,
it is found that within a reasonable duration of
observation time the activity will be concen-
trated in a layer of the order of 1 meter thick
103
104
Atomic Radiation and Oceanography and Fisheries
spread over a horizontal area of radius r. They
find that with the best of present instruments,
the horizontal spread in which the concentration
of the introduced radioactivity can be deter-
mined corresponds to r= 1 km. With the possi-
bility of improved instrumentation, and the use
of specially selected nuclides, it may be possible
to raise the area of detection and determination
of activity concentration to about 100 km^, an
area which is still negligible with respect to
oceanic expanses.
The radioisotopes suitable for such measure-
ments must of course have a half-life compati-
ble with the mixing rates to be studied and yet
short enough so as not to constitute a perma-
nent hazard, namely of the order of a week to a
month. Moreover, they must be available in
multi-curie amounts at reasonable cost, should
form soluble ionic species in sea-water, have a
high specific activity, and, for instrumental rea-
sons, should be gamma emitters with energy be-
tween .2 and 1.3 Mev. Revelle, et al., were
able to list three such isotopes, which, together
with half-life, cost, and other data, are listed in
the following table:
Cost
Half- per
Isotope life curie
Rb"* . . . 19.5 day $1000
P^ ... 8.0 day 750
Ba'*" ... 12.8 day 500
Specific Gamma
activity energy
available Mev
9 mc/gram 1.1
Carrier-free 0.36, 0.72
Carrier-free 0.16, 0.54
Comparison of the cost of these isotopes with
the maximum area of detection cited above
shows that the study of large-scale transfer phe-
nomena in the oceans, using deliberately intro-
duced artificial radioactivity in the form of spe-
cific isotopes, is so costly as to be infeasible with
the estimated best instrumentation which will
be available in the near future. It is evident
that such isotopes are at best adapted only to
short-term, small scale studies of local phe-
nomena. The use of mixed fission products on
a large scale, discussed elsewhere in this report,
is somewhat more feasible but is beset with
many difficult problems of transportation and
handling.
From these considerations it seems evident
that the critical data in studies of atmospheric
and oceanic mixing and interaction will come
from the use of the naturally occurring isotopic
tracers, which reflect in their material balance
adjustments the differential rates of transfer
from source, through reservoir, to sink, and
loss by decay. It is from these transfer rates,
adjusted to the steady state geochemical and
geophysical cycles of the various elements, that
we can hope to gain an understanding of the
long period variations in natural transfer phe-
nomena. The importance of gaining a clear un-
derstanding of the long period transfer rates,
when problems such as storage of potentially
hazardous radioactive wastes and cumulative ef-
fects of nuclear detonations are considered, can-
not be overemphasized.
In the following sections we discuss the pres-
ent status of our knowledge of the distribution
and properties of the various naturally occurring
isotopes which are useful for studies of atmos-
pheric and oceanic transfer phenomena. In ad-
dition, mention is made of the nuclides pro-
duced in nuclear detonations and supplied by
reactors which have properties such that they
are also useful in such studies and which have
been studied to some extent.
II. Distribution of naturally occurring isotopes
of elements adapted for transfer studies
In this section we discuss the production and
occurrence of radioactive and stable isotopes
showing measurable isotopic variations, and the
distribution factors which determine their rela-
tive concentrations in natural materials.
Carbon 14
Carbon 14 is formed in the atmosphere by
the reaction of neutrons with nitrogen, i. e.
Ni4-}-n = C" + p + 620kev;
the neutrons being the result of the interaction
of primary cosmic rays with the atmosphere
(Libby, 1955). The carbon 14 is naturally ra-
dioactive, decaying by ^S-emission back to nitro-
gen 14 with a half -life of 5570 years. Thus the
half-life is so short that radiocarbon depends,
for its existence, on the continual production in
the stratosphere, with which it is presumably in
steady state. The assumption of a steady state
condition for at least the last 15,000 years is
justified by the observation that radiocarbon
dates on historic samples agree with the calen-
dar dates. The steady state production rate,
which is equal to the steady state disintegration
rate, can be calculated from measurements on
the neutron flux in the lower stratosphere and
compared with the observed specific activity of
Chapter 11 Tracer Studies of the Sea and Atmosphere 105
carbon. Anderson (1953) who has made the displayed by the terrestrial plants and the atmos-
most recent and detailed considerations of the phere.
production rate, finds a rate of 2.6 carbon 14 The evaluation of the exchange time of COj
atoms per cm^ and per sec. between atmosphere and sea from data on the
The carbon 14 atoms are oxidized to CO2 and natural distribution of C^*, is discussed in See-
thus enter the normal geochemical and biologi- tion IV of this paper.
cal cycles of carbon via the atmosphere. The The most recent and accurate measurement of
distribution through the atmosphere and the the absolute radiocarbon concentration is that
terrestrial plants is rapid, and the steady state of Suess (1955), based on comparisons with an
radiocarbon concentration in these reservoirs is absolute standard obtained from the National
taken as the basis for the so-called "modern" Bureau of Standards. Suess finds a concentra-
specific activity of carbon, namely about 15 dis- tion of 1.238 x IQ-^^ atoms of O* per atom of
integrations per minute per gram of carbon. carbon for average 19th century wood, corrected
On the other hand, the transfer of carbon for decay to the present date and corrected for
from the atmosphere to the sea is slow enough, isotopic fractionation. Based on this value and
compared to the half-life, to produce a signifi- a half -life of 5568 years, we give below the
cant difference between the predicted and ob- amounts of C" in metric tons, and the activi-
served activity of carbon in the surface layers ties in megacuries present in the major reser-
of the oceans. Carbon, as one of the lighter voirs on the earth (Craig, 1957 (a), calcu-
elements, is subjected to natural fractionation lated from his Table 1). The figures for the
of its isotopes in the various reactions it under- atmosphere and terrestrial living matter are nor-
goes in its biogeochemical cycle (cf. section on malized for isotopic fractionation, while the or-
stable isotope variations, below). The steady ganic and inorganic carbon in the ocean was
state isotopic separation of the stable isotopes assumed to have an average age of 600 years
C12 and C13 produces a C" concentration in relative to corrected 19th century wood, or 200
surface ocean water bicarbonate and shell car- years relative to surface ocean bicarbonate (see
bonate which is about 2.5 per cent higher than Section IV, this paper) .
the C^^ concentration in terrestrial plants. It is Total C* Total activity
thus known that the C^* concentration in ocean Reservoir metric tons megacuries
bicarbonate and carbonate should be about 5 per TMrkT' IwTng ' matter' + ^'^"^
cent higher than the concentration in land humus 2.2 11.0
plants, namely about 15.75 disintegrations per Ocean: Total organic matter. 3.8 17.6
minute per gram of carbon (Craig, 1954). In ^^^^'''- Total inorganic car-
, / ° ^ \ 1 bon 49.8 228.6
actual tact, however, measurements show that
the specific activity of bicarbonate and carbon- Totals 56.8 261.6
ate from the ocean is about the same as the spe- ^^^ ^^^^^ ^^^j^j^^ ^f radiocarbon present on
cific activity of land plants. Thus the atmos- ^^^ ^^^^^^ ^^^^ corresponds to some 260 mega-
pheric C" activity has been increased 5 per ^^^^^^^ practically all of which is in the ocean,
cent by slow exchange of CO, between atmos- Using Anderson's figure for the production rate,
phere and sea, resulting in an "apparent age," ^ited above, and the decay constant of 3.945 x
relative to wood standards, of 400 years for the ^q-^^ ^^^^-^^ the calculated total inventory of
bicarbonate and carbonate shells in the surface radiocarbon on the earth is 78.4 tons, which
layers of the ocean (Craig, 1954, 1957 (a)), differs from the figure of 56.8 metric tons, ob-
Some 10 measurements have now been made on tained in Table II, by about 28 per cent. How-
marine plants, animals, and sea-water from the ever, the production rate, as estimated from cos-
Atlantic (Suess, 1954) and from the New Zea- rnic ray data and the counting of atmospheric
land area (Rafter, 1955) which indicate that neutrons, is uncertain to at least 20 per cent be-
the radiocarbon "age" of surface marine car- cause of the uncertainty in the reactor flux from
bonate is about 400 years; it is thus clear that which the neutron counters are calibrated. More
radiocarbon age determinations made on deep recent estimates of the production rate are lower
ocean waters must all be referred to this base- than the figure cited above and all that can be
line, rather than to the modern specific activity said about the agreement between the calculated
106
Atotnk Radiation and Oceanography and Fisheries
and predicted radiocarbon inventories is that
they agree within present hmits of error.
Tritium
Tritium (H^) is made in the upper atmos-
phere, primarily in the "stars" or nuclear ex-
plosions produced by the collisions of primary
cosmic ray particles with the atmospheric
molecules; it is naturally radioactive, decaying
by ^' emission to helium 3 with a half-life of
about 12.5 years (Kaufman and Libby, 1954).
The T atoms "burn" very quickly to HTO and
enter the precipitation — evaporation cycle of
water. A very small amount of tritium is pro-
duced in rocks by the nuclear reaction of
lithium with neutrons produced by spontaneous
fission of uranium and from (a,n) reactions
(Morrison and Pine, 1955) ; the production of
tritium by this process is insignificant relative
to the atmospheric production.
Detailed studies of the distribution of tritium
in natural waters have been made by Libby and
his co-workers at Chicago. The natural concen-
tration of tritium (before thermonuclear tests)
in continental waters averages about 5 X 10"^®
atoms of tritium per atom of hydrogen. (Fol-
lowing Libby's usage, such a concentration will
hereafter be referred to as 5 tritium units, ab-
breviated as T.U.) The concentration in oceanic
rains is about 1 T.U., while in the surface
waters of the ocean itself the concentration
appears to be as low as 0.2 T.U. The sea is,
of course, the ultimate resting place of the
tritium formed in the atmosphere, and the low
concentration in the oceanic rains relative to
continental rains is principally due to tritium
removal by direct molecular exchange with the
sea surface (see below) .
Kaufman and Libby (1954) calculated the
tritium production rate in the atmosphere by
equating it with the rate at which tritium dis-
appears from the atmosphere into the ocean,
taken as the sum of the tritium entering the
ocean by run-off from continental rains and the
tritium entering directly via oceanic rains. For
this calculation only the average run-off and
ocean precipitation figures, and measured av-
erage tritium content of such waters, are needed.
They obtained a net production rate, averaged
over the earth's surface, of .12 T atoms per
cm2 per second. Von Buttlar and Libby (1955)
measured many more rain samples, and also
analyzed 5 samples of ocean water, from which
they could estimate the tritium content of the
water vapor which evaporates from the sea
surface. Using this latter figure they calculated
the production rate over the oceans, assuming
that tritium is lost from the atmosphere only
by oceanic rain, and gained by production and
oceanic evaporation, and obtained a figure of
0.11 to 0.12 T atoms per cm- per sec. A similar
calculation was made for the production rate
over land, assuming tritium is lost from the
continental atmosphere only by continental rains
running off into the ocean, and gained by pro-
duction, and by transport of ocean vapor onto
the continents. Using the tritium data for av-
erage Mississippi Valley rains, they obtained a
figure of 0.16. Their estimated world average
production rate is 0.14 with a probable un-
certainty of less than 20 per cent. This value
agrees precisely with the expected world pro-
duction rate calculated by Currie, Libby, and
Wolfgang (1956) from their experimental
measurements on tritium production in nitrogen
and oxygen by bombarding protons of 450-Mev
and 2-Bev energies. Previous experiments and
calculations by Fireman and Rowland (1955)
gave an expected production rate of 0.2 T
atoms/cm- sec, also in good agreement with
the rate apparently observed.
However, the tritium production rate must
be a good deal higher than the figures given
above. Von Buttlar and Libby calculated that,
with such a production rate, and with the ob-
served surface sea concentration of about 0.24
T.U., then the mixed layer of the sea is about
100 meters deep if one assumes that all the
tritium of the sea is in the mixed layer. Though
this depth is consistent with observational data
on the sea, such a calculation assumes that the
mixed layer is sealed off from the deep sea so
that no tritium mixes below the thermocline,
and the question then arises as to just how much
mixing across the thermocline does, in fact,
occur.
As discussed by Wooster and Ketchum in a
separate paper in this report, various observa-
tions on ocean currents and on the heat flux
through the ocean floor, indicate that the deep
ocean water turns over, or mixes with surface
water, in times of the order of a few hundred
years. Assuming a generalized two-layer model
of the sea, consisting of a shallow mixed layer
about 75 meters deep on the average, and a
Chapter 11
Tracer Studies of the Sea and Atmosphere
107
homogeneous deep sea below the thermocline
marking the interface between the layers, Craig
(In press (a) ) derived equations relating the
production rate of a radioactive isotope to the
concentrations of the isotope in the two layers
of the sea and the mixing time through tlie
thermocline. (These functions are discussed
briefly in a separate paper by the writer in this
report, in which calculations on the disposal
of fission products in the sea and their ultimate
steady state concentrations are discussed.) The
applications of such calculations to the distribu-
tion of radiocarbon in the atmosphere and sea
were demonstrated; these results are discussed
in Section IV of this paper.
Application of such calculations to the dis-
tribution of natural tritium (Craig, 1957 (b)
and manuscript in preparation) shows that for
reasonable internal mixing rates of the sea, most
of the world inventory of tritium must actually
be in the deep sea below the thermocline. Thus
for a deep water replacement time, or residence
time of a water molecule in the deep sea before
mixing into the surface layer, of 0 to 1000
years, and with a surface concentration of 0.24
T.U., the tritium flux into the sea must be
between 7.6 and 0.3 atoms cm^/sec. For the
most reasonable deep sea residence time of the
order of a few hundred years, the flux must
be somewhere between 0.4 and 0.8. It is found
that about | of the total tritium in the sea is
below the thermocline, with a deep-sea tritium
concentration of about 0.014 tritium units.
The tritium production rate over the North
American continent was recalculated (Craig,
op. cit.) by taking into account the removal of
tritium from the continent by the outgoing
water vapor which does not condense over the
land. This calculation gives a world average
production rate of from 0.6-0.8 after correction
for the latitudinal geomagnetic eflfect on the
incoming cosmic rays. A tritium production
rate of this order of magnitude indicates an
average deep-sea residence time of water of
about 250 years, for a simple two-layer ocean.
Calculations based on a second-order ocean
model in which the deep sea reservoir is exposed
to the atmosphere at high latitudes would give
a longer residence time relative to the mixed
layer of the sea because of direct entry of
tritium from the atmosphere to the deep sea.
(See the discussion of radiocarbon residence
times in Section IV of this paper.)
However, if the bulk of the tritium is not
produced by cosmic radiation, but by solar
accretion (see below), the world average pro-
duction may be as high as 1.7 atoms cm^/sec
because the geomagnetic correction applies only
to tritium produced by cosmic rays in the trop-
osphere.
The calculated production rate over the
oceans of about 0.14 is obtained by considering
only the transfer of tritium into the sea by
rainfall. Since rainfall appears to account for
only about one-tenth of the tritium which ac-
tually enters the sea, it appears that the trans-
fer of tritium from atmosphere to sea by direct
molecular exchange across the sea surface is
about 9 times as effective as the scrubbing action
of precipitation.
A production rate of 1.4 atoms of tritium/
cm^sec means that the world inventory of trit-
ium, before thermonuclear tests, was about
20 kg of tritium, or 200 megacuries, essentially
all of which is in the ocean. However, from
the experimental data obtained by the workers
cited above on the production of tritium by
the action of protons on nitrogen and oxygen,
it appears very doubtful that the cosmic ray
production rate can be much higher than about
0.2. In fact it is probably necessary to assume
that tritium is produced on the surface of the
sun and is directly accreted into the earth's
atmosphere, rather than being a secondary re-
sult of the action of the cosmic ray protons on
the atmosphere, as postulated by Feld and Craig
(Craig, 1957(b)).
From a study of the fall-out rate of strontium
90 pushed into the stratosphere by large atomic
detonations, Libby (1956a, b) calculates the
stratospheric residence time of strontium to be
about 10 years (cf. Section IV of this paper).
Since at least half of the tritium production
should take place in the stratosphere even if
all the production is due to the action of pro-
tons on the earth's atmosphere, slow mixing
through the tropopause will pile up tritium in
the stratosphere in the same way that slow
exchange across the sea surface builds up the
radiocarbon concentration in the atmosphere.
One-sixth of the atmosphere is above the tropo-
pause on the average, but the water vapor con-
centration is so low that only about 0.3 per cent
of the total water vapor in the atmosphere is
in the stratosphere; thus the tritium concentra-
tion of the stratospheric water vapor will be
108
Atomic Radiation and Oceanography and Fisheries
much higher than that of the tropospheric va-
por, which averages about 1 T.U. From the
strontium data we assume that the mixing time
of water vapor through the tropopause is at
least 10 years.
Assuming a tritium production rate of 1.4,
half of which is in the stratosphere, the trit-
ium concentration of stratospheric water vapor
is then calculated to be at least 300,000 tritium
units. This is an astounding concentration fac-
tor relative to tropospheric water vapor. Re-
cently the present writer and F. Begemann
analyzed a series of samples of atmospheric
molecular hydrogen for deuterium and tritium
content respectively. Mass spectrometric meas-
urements showed that all samples contained
about 2-10 per cent less D than ocean water,
falling just in the range of meteoric waters, and
containing far too much deuterium to represent
thermodynamic equilibrium with water vapor.
These data confirmed a few previous measure-
ments (cf. Harteck, 1954) which showed that
the molecular hydrogen in the atmosphere must
form by direct photodissociation of water vapor
in the region around 70 km altitude, rather than
by bacterial decomposition of organic matter
which has been shown to produce hydrogen in
isotopic equilibrium with water. We may thus
assume that the tritium content of stratospheric
molecular hydrogen is about the same as that of
the stratospheric water vapor.
Assuming that the hydrogen is statistically
distributed in the atmosphere, so that i is
above, and | below, the tropopause, and taking
again the mixing time through the tropopause
as 10 years, we then calculate the tritium con-
tent of the molecular hydrogen in the trop-
osphere. This figure is found to be 100,000
tritium units, probably as a minimum figure
because of slow vertical mixing from the base
of the stratosphere to the 70 km level where
the hydrogen is made, and because of the indi-
cation that more than half the tritium is found
initially in the stratosphere. The tritium con-
tents measured by Begemann on a dozen sam-
ples of tropospheric hydrogen range from 50,-
000 to 100,000 tritium units, averaging about
80,000 T.U., in excellent agreement with the
calculated value when the various uncertainities
are considered.
It thus appears that the high tritium content
of tropospheric hydrogen can be satisfactorily
explained by purely geophysical reasoning based
on the stratosphere-troposphere exchange time
as estimated from Libby's Sr^o data, and the
known concentration of water vapor in the
stratosphere. This explanation seems more likely
than the intricate series of photochemical mech-
anisms proposed by Harteck (1954) which at
best may account for a tritium concentration of
about 1000 T.U. in the molecular hydrogen.
Beryllium 7
Beryllium 7 is formed in cosmic ray stars,
the peak production occurring at about 15 km.
It decays by electron capture to lithium 7 with
a half -life of about 53 days. The discovery,
and the elucidation of the geochemical history,
of this cosmic ray produced nuclide is due to
Arnold and Al-Salih (1955).
Once formed in the atmosphere, the beryl-
lium burns to the nonvolatile BeO or possibly
Be (OH) 2, either of which diffuses until en-
countering a dust particle and adhering thereon.
It is thus a tracer for the atmospheric dust, on
which it is washed out of the atmosphere by
rain, ultimately going into the ocean. Arnold
and Al-Salih detected radioberyllium in 22 rain
and snow samples from Chicago and Indiana,
the average absolute assay being 6x lO*' atoms/
liter. The estimated world-wide average pro-
duction rate is 0.04 atoms per cm^ per second,
based on estimated rates of transfer and mix-
ing in the stratosphere and troposphere. Most
of the mixing rates involved are of the order
of magnitude of the half-life, which makes
calculation of the production rate difficult but
greatly enhances the utility of the isotope for
studying atmospheric processes, especially when
used in conjunction with tritium.
A detailed discussion of the beryllium 7 pro-
duction rate and atmospheric residence time has
recently been given by Benioff (1956). He
calculates the production rate to be 5.0 atoms/
cm-min in the stratosphere and 1.3 atoms/cm--
min in the troposphere, and he finds that a
stratospheric residence time of the order of
years is required to match these production rates.
Thus his stratospheric residence time agrees with
that found by Libby for fission products.
Beryllium 10, a yS" emitter with a half-life
of 2.5 X 10*^ years, is also formed in the cosmic
ray stars. J. R. Arnold has recently identified
this isotope in deep sea sediment samples
(manuscript in press) ; it should be of great
Chapter 11
Tracer Studies of the Sea and Atmosphere
109
importance, because of the long half-hfe, for
the dating of such sediments.
Deuterium and Oxygen 18
Deuterium and oxygen 18 are stable isotopes
of hydrogen and oxygen respectively, and it is
now well known that the isotopes of these
elements, as well as of other light elements
such as carbon, nitrogen, and sulphur, are
fractionated, or separated, by chemical and
physical processes in natural systems. Since
the fractionation factors for stable isotopes are
measurable and/or calculable for many separa-
tion processes, and since the magnitude of these
factors is mainly a function of temperature and
process, the stable isotopes are extremely well
adapted for the study of natural transfer rates
in the geochemical cycles of their elements.
The concentrations of these isotopes show
rather wide variations in different natural ma-
terials, these variations generally ranging from
a few tenths of a per cent to a few per cent.
In this report we shall mainly be concerned
with the distribution of these isotopes in marine
and fresh waters and in the atmosphere. Craig
and Boato (1955) have recently reviewed the
present status of natural isotopic studies, and
reference is made to that paper for a more
extended discussion.
Vapor Pressures and Relatfve Abundances of
THE Isotopic Water Molecules
Relative p (mm Hg)
abundance ,, ^ ^
Species (ocean water) Mass 30° C 100° C
H2O 1 18 31.5 760
HDO 1/3230 19 29.4 741
H^O^" 1/500 20 31.3 756
The above table shows the three most prom-
inent members of the family of isotopic water
molecules, their masses, relative abundances in
average ocean water, and their vapor pressures
at two temperatures. Other members of the
family are much less abundant and can be
neglected. One sees from the table that the
vapor pressures are not a direct function of
the molecular weight ; the vapor pressure differ-
ence between HDO and HJD is 10 times larger
than the vapor pressure difference between
H,0i8 and HoO, at 30 °C. The isotopic separa-
tion in an evaporation or condensation process
is directly proportional to these vapor pressure
differences, so that in water vapor in equi-
librium with water at 30°, the percentage de-
pletion in deuterium, relative to the water, is
ten times larger than the percentage depletion
in oxygen 18.
The natural isotopic variations are customarily
given in terms of per mil enrichment or deple-
tion relative to a standard, similar to the way
the density parameter is given in an oceano-
graphic temperature-salinity diagram. The data
are presented in terms of a function 8, defined
as follows:
8 ( % ) = [ (Rsample/Rstd ) - 1 ] x 1 000
where R is the isotopic ratio O^YO^^ or D/H.
In the case of deuterium, however, the quantity
in the brackets is multiplied by 100 and the 8
values are given in per cent, because of the ten
times higher isotopic separations encountered.
Rstd here refers to the isotopic ratio in average
ocean water.
Since HoO^*' is the most volatile isotopic
species, the water vapor over the oceans is
depleted in the heavy isotopes relative to the
surface ocean water. As this vapor moves over
the continents, the first rain to fall out is en-
riched in the heavy isotopes relative to the
vapor, again because of the higher volatility of
the lightest species. Removal of the heavy iso-
topes, in the form of rain, then causes the vapor
to become continually depleted in deuterium
and oxygen 18. In general enough rain falls
out of an air mass over the oceans so that by
the time the mass reaches the continents the
rain is already "lighter" in isotopic content
than ocean water, and as the air mass moves
inland and poleward the rain which falls out
becomes more and more depleted in deuterium
and oxygen 18.
In a recent study by Craig (ms. in prepara-
tion) several hundred fresh water samples from
all over the world were analyzed for deuterium
and oxygen 18 concentration. The deuterium
concentration varies by about 30% relative to
mean ocean water, 8D ranging from -f3 to
— 27%, while the oxygen 18 concentration
varies by only 4%, 80^^ ranging from -\-6%o
to — 34%o. The delta values for the trwo iso-
topes show a linear correlation such that 8D =
980^^, corresponding to the vapor pressure
difference ratio at about 25 °C. The reason for
the high value of the average temperature at
which liquid and vapor equilibrate in the at-
mosphere is as yet unknown; the uncertainty
110
Atomic Radiation and Oceanography and Fisheries
in the vapor pressure data is such that the
value could hardly be less than about 20°. The
delta values for fresh waters show a general
correlation with latitude or distance from the
ocean; there is a general decrease in the heavy
isotope concentration as the latitude varies from
equatorial to polar, reflecting the continuous
loss of vapor from the poleward moving air
masses.
Isotopic variations such as mentioned above
can be measured quite simply and precisely
with the mass spectrometer, and it is evident,
from the ranges of variation cited, that such
studies on meteoric waters can provide a wealth
of information concerning meteorological trans-
fer and mixing phenomena in the atmosphere.
The average water vapor of the earth has
roughly the composition 8D=— 10%, 80^ » =
— ll%o, but large variations, related to the
amount of liquid water which has condensed
out of the vapor, occur, and thus such studies
are directly adapted to problems of water vapor
transport over both the oceans and continents.
The situation in the oceans themselves is
somewhat more complicated. The oxygen iso-
topic composition of ocean waters has been
studied by Epstein and Mayeda (1953), and
the deuterium variations in the same samples
by Friedman (1953) ; these writers also an-
alyzed nine fresh water samples and first eluci-
dated the D-O^^ relationship in natural waters.
The surface layers of the oceans are in general
enriched in the heavy isotopes relative to mean
ocean water because of the net storage of HoO^*'
in the stagnant and circulating fresh water and
vapor; the extent of this enrichment reflects
the hold up at the boundary of the mixed
surface layer, namely the thermocline. On the
other hand, the deeper layers of the ocean are
depleted in deuterium and oxygen 18, relative
to mean ocean water, because of the influx of
glacial melt water in polar latitudes, the glacial
waters having 8 values at the lightest ends of
the ranges cited in the preceding paragraphs.
Thus the oceans are isotopically upside down
with the heavy isotopes concentrated at the
surface, and the isotopic composition parameters
in general correlate with salinity.
Epstein and Mayeda (op. cit.) showed that
the salinity-oxygen 18 variations in marine
waters were consistent with a model in which
the oceanic precipitation is progressively de-
pleted in the heavy isotopes as a function of
the extent of precipitation from the local atmos-
pheric reservoir. Salinity, of course, is uniquely
related to the direct amount of fresh water
removed by evaporation or added by meltwater
dilution, but the relationship in the case of
isotopic composition is more complex. This is
because the isotopic composition of fresh water
precipitating over the oceans, or added by run-
off or melting of ice, is variable, depending on
the history of the air mass from which it was
precipitated. The correlation between isotopic
composition and salinity is therefore more or
less local, reflecting the particular relations ob-
taining on the average in the area. As a result,
the isotopic composition parameters, rather than
being simply transforms of salinity, and thus
not inherently very useful for the study of
transfer problems, become important parame-
ters for such studies because of the reflection
of areal conditions in a manner diff^erent from,
but related to, the salinity parameter. Examples
of this eflfect are discussed in Part IV, where
applications to transfer studies are treated.
The isotopic composition of atmospheric
oxygen is an interesting case of adjustment
of a reservoir composition to steady state non-
equilibrium biogeochemical transfer processes.
Oxygen would exist in the atmosphere in the
absence of living plants because of photodisso-
ciation of water vapor in the atmosphere, with
subsequent escape of hydrogen from the earth.
However, oxygen is cycled through the bio-
sphere so rapidly that its isotopic composition,
rather than reflecting its mode of formation,
may be adjusted to a steady state balance be-
tween photosynthetic formation and respiratory
uptake. The oxygen produced in photosyn-
thesis is in isotopic equilibrium with the water
taken up by the plants and is very close in
isotopic composition to this water; however
the atmospheric oxygen is some 23%o enriched
in oxygen 18 relative to average ocean water.
Lane and Dole (1956) have measured the
preferential uptake of oxygen 16 by various
animals and land plants and concluded that the
net fractionation is such as to account quantita-
tively for the atmospheric oxygen composition.
Respiration in the oceans shows a much smaller
selective oxygen 16 uptake (Rakestraw et al.,
1951; Dole et al., 1954) and the isotopic com-
position of oxygen dissolved in ocean water is
variable and dependent on the amount of oxy-
gen which has been taken up from the local
Chapter 11
Tracer Studies of the Sea and Atmosphere
111
reservoir. There is some doubt as to whether
the data of Lane and Dole can actually yield
a material balance without invoking some spe-
cial mechanisms relating the productivities of
the oceans and the land, and a good deal of
further study on this question is needed. The
intent here is to point out that the isotopic
transfer rates involved in this problem of the
isotopic composition of atmospheric oxygen,
and the variations in the isotopic composition
and amounts of oxygen dissolved in ocean
waters, may well be important parameters for
the study of transfer phenomena in the oceans
and the atmosphere and the interaction between
them.
Carbon 13
About one per cent of natural carbon con-
sists of the stable isotope O^; the ratio C^^/C^-,
and thus effectively the C^^ concentration, in
natural material shows a range of variation of
about 6 per cent. The details of the natural
variation have been described (Craig, 1953,
1954), and reference is made to these papers
for extended discussion. The delta values for
carbon are referred to a standard which has
the composition of average limestone; on this
scale the characteristic compositions of natural
materials are shown below:
Material d C^ (%c)
Limestones and shell 0
Ocean bicarbonate — 1.5
Atmospheric CO2 — 7
Marine biosphere — 13
Terrestrial biosphere — 25
Coal —25
Petroleum — 28
Shales —28
The difference between the compositions of
atmospheric carbon dioxide and ocean bicar-
bonate probably reflects the isotopic equilibrium
constant for the exchange of carbon isotopes
between these compounds; the other variations
shown in the table are due to kinetic factors
which cause a selection of the isotopes in the
various processes involved in the biogeochemi-
cal cycle of carbon. The carbon 14 variations
caused by such processes should be almost
exactly twice the C^^ values shown above, and,
as noted previously, the knowledge of the C^^
variations has been of great value in under-
standing the transfer rates and mixing phenom-
ena involved in the distribution of radiocarbon.
A particularly fertile field for study is the
marine biosphere and the phenomena involved
in the isotopic partition of carbon between
carbonate and organic matter. One critical
parameter in the kinetic processes involved is
the rate of uptake of CO, by photosynthesis
versus the relative rates of CO., replenishment
by mixing and by reassociation of bicarbonate
ions, and such studies may well lead to an
improved knowledge of the carbon flux through
local ecological systems and the interaction of
the local system with the general marine reser-
voir. Keeling (manuscript in preparation) has
studied the isotopic variations in carbon dioxide
over the land, and has found that the isotopic
parameters are critical indicators of the atmos-
pheric transfer phenomena through local bio-
topes, as a result of the large difference in
isotopic composition between normal atmos-
pheric carbon dioxide and carbon dioxide pro-
duced in respiration during the night.
III. Contribution of radioisotopes to the geo-
sphere by nuclear fission and detonations
The steady state isotopic distributions dis-
cussed in the preceding section have, in the
case of radioactive elements, been altered to
some extent by contribution to the geosphere
of radioisotopes produced in nuclear fission in
both reactors and nuclear detonations. Such
contributions, rather than being detrimental
to the study of natural transfer phenomena,
have, on the whole, provided extra parameters
of great value for such studies. It is of course
obvious that addition of such elements under
carefully controlled conditions in selected loca-
tions and at planned times would have con-
tributed a great deal more to our knowledge of
geophysical phenomena than the actual dis-
persal of the material has resulted in; never-
theless it is possible, even though working in
almost total ignorance of the amounts of ma-
terial added, to deduce a great deal of valuable
information about mixing rates and even to
make detailed studies of certain specific prob-
lems.
The fission of uranium in reactors and nu-
clear weapons results in a great variety of
elements distributed mass-wise into a spectrum
known as the fission yield curve; the propor-
tions of the various masses produced are a
unique function of the atomic mass and vary
112 Atomic Radiation and Oceanography and Fisheries
little with neutron energy or substitution of activity, the values all represent lower limits
plutonium for uranium 235. For our purposes, and should be slightly larger.
the elements of most interest produced by fis- '^9 .
^ ■' . activity
sion are krypton 85, strontium 90, and cesium produced
137, raneine in half-life from 10 to 33 years; ^. . J'y?^^
. . ° ^ 1-1 Fission fission
tritium, which is not a fission product, is also yield (mega-
of great importance. Measurable additions to Radioisotope Half-life (%) curies)
,, , f . •,.• ,. ^- r,r, J Krypton 85 10 years 0.24 2
the geosphere of tritium, strontium 90, and str^^^i^^ ^q 28 years 5.0 15
krypton 85 have been noted and are discussed Cesium 137 33 years 6.3 16
in Part IV in connection with general applica- Lj^by (1956a, b) has given detailed discus-
tions to transfer study phenomena. In this sec- sions of the fall-out patterns of strontium 90
tion we estimate the total amounts of these and cesium 137, based on the Project Sunshine
nuclides which have been produced ; these esti- measurements on world-wide samples. Geo-
mates are also of some interest in connection physically, the most significant finding is that,
with the magnitude of the disposal problem, as mentioned previously, the residence time in
both present and future. ^^ stratosphere of material pushed through
One result of the advent of nuclear fission ^^^ tropopause is about 10 years. The most
is that all the krypton in the atmosphere has f ^^"^ measurements on the distribution of
become contaminated with radiokrypton. De fi/sion products from nuclear explosions (Libby:
Vries (1956) has measured the specific activity ^^^^^^^ before American Association for the
of atmospheric krypton, taken in March of Advancement of Science, Washington, D.C
1955, as 25,000 counts per minute per mole. ^^^^^.^^ ^2, 1956) indicate that the amount of
The activity is due to contamination with kryp- ^^rontrnm 90 scattered over the surface of the
ton 85, which decays by ^- emission with a ^^'^^ '' "°^ equivalent to an average activity
half-life of ten years. From DeVries' measure- concentration of about 16 millicuries per square
ment, we readily calculate that 56.4 moles, or "'^^- ^^ ^^^l^^^^^' ^^^, ^^^"^^ "°7 ^^^^ ^" *.^;^e
4700 grams, of Kr«^ are now present in the stratosphere is equivalent to another 12 milli-
atmosphere, and in ignorance of the rate of curies per square mile. The total amount so far
production, we make only a small error by distributed is thus about 5 6 megacunes of Sr^o,
assuming this figure as the total amount of °^ ^^''^ ^^.^^^ 2.4 are still in the stratosphere,
radiokrypton produced and not correcting for ^^^' assuming purely statistical distribution,
decay. From the fission yield of 0.24 per cent ^,«"^^ ^.3 megacunes have fallen directly into
c - iu-^ v^4-««„ :t. ^^^J^^r. <-u.«- .^^J 02 <;nr> the sea, while about 0.9 megacunes have fallen
for this isotope, it appears that some 23,500 , , , r t^ r , • -,
~ 1 <cnn 1 ^c ^^o■i'^ J ^1 i-^ • ^ u ^ on the land surface. Because of the similar
moles, or 5500 kg, of U-^^ and plutonium have ,,^,., ,/-. -.i.r r
J c • • i-u J \- r i-u half-life and fission yield, the figures for cesium
undergone fission since the advent of anthropo- .,, , , /, '. , °, ^
^- r ■ ,,. • ^ , • 137 will be almost identical to those tor stron-
genetic fission, resulting in an atmospheric . ^ ^ • , r • 1 ,
f • •, f ^ • T. • 1 tium 90. Comparing these figures with the ones
krypton activity of 2 megacunes. It is assumed, . . . v ^.1.1 0.1. i. ui
'^ ■' , , ,,,/-• 1 1 given in the above table, we see that roughly
as seems reasonable, that all fission produced ?^,,-, / 1 r n i.u i-j /: • j Z
... ' . , \ 5.6/17.4 or -\ of all the solid fission products
krypton finds its way into the atmosphere. r jju m c • u u j-
•'^ •' ^ so far produced, by all fission, have been dis-
From the fission yield data, we calculate the tributed over the atmosphere, the land, and the
total amounts of radiostrontium and cesium gg^ j^y atomic weapons testing,
which have been produced; the data for the xhe most important of these elements for
three elements are shown below. Only the studying mixing rates in the sea should be
strontium and cesium produced by detonation cesium 137, which being soluble, should be
of nuclear weapons will escape into the atmos- an excellent tracer for the mixing rate of surface
phere and be deposited over the surface of the ocean water down through the thermocline.
earth and sea. Because the krypton figure is Krypton 85 should ultimately prove important
uncorrected for decay, and because some kryp- for atmospheric mixing studies, especially for
ton must have gone directly into the strato- comparison of mixing rates of gaseous and
sphere and is not included in the measured solid elements across the tropopause.
Chapter 11
Tracer Studies of the Sea and Atmosphere
113
Thermonuclear weapons may also be expected
to produce some carbon 14 because of the
neutrons released into the atmosphere in the
explosion. A contemporary sample of grass,
collected in the summer of 1955 in S.W. Kansas
by the writer, was analyzed for C^* content by
M. Rubin at the U.S. Geological Survey labora-
tory. This grass was found to be about 2.5
per cent higher in O* content than the 19th
century wood, corrected for age, used as the
U.S.G.S. radiocarbon standard (Suess, 1955).
The samples and standard were analyzed for
C^^ content by the writer and the results cor-
rected for isotopic fractionation, and the sample
was counted twice. Thus the measurement is
quite precise, and probably indicates that the
atmospheric radiocarbon content has risen about
2 per cent above normal at the present time,
due to thermonuclear neutron production. For
future geochemical studies with natural radio-
carbon it will be important to monitor continu-
ously the activity of contemporaneous plants
and atmospheric carbon dioxide, though the
effect will be insignificant for radiocarbon dat-
ing studies for some time yet.
The situation with tritium is different. The
earliest rain ever analyzed for tritium content
fell in Chicago in May of 1951; since October
1952 Libby and his co-workers at Chicago have
produced an essentially continuous record of
the tritium content of Chicago rain, and have
analyzed a great many other samples from many
parts of the world. Their data show that there
was no significant production of tritium in the
November 1952 Ivy test (Kaufman and Libby,
1954). However, the March 1954 Castle ther-
monuclear tests produced an increase in tritium
concentration of Chicago rain from an average
value of 9 to a maximum value of 450 atoms
T/lQi^ atoms H; i.e., a factor of 50 (von
Buttlar and Libby, 1955). Even more striking
was the discovery that the tritium content of
southern hemisphere waters showed no signifi-
cant increase in tritium concentration, and snow
samples collected from the Antarctic as late as
February of 1955 showed that during this in-
terval no significant amounts of artifically pro-
duced tritium had crossed the equator (Bege-
mann, 1956).
Begemann's recent data show that the tritium
rained out of the northern hemispheric atmos-
phere with a mean-life of about 40 days for
the decrease in tritium concentration; as late
as the end of 1955 the tritium concentration of
Chicago rain was still about three times normal.
In Section II above it was concluded that the
world inventor}' of tritium was about 20 kg,
with about 5 kg in the mixed layer of the sea,
and about 15 kg in the deep sea. The Chicago
data show that the tritium content of the sur-
face ocean waters has increased by at least a
factor of four, indicating that the order of
magnitude of 20 kilograms of man-made trit-
ium has so far rained out into the ocean. Thus
the amount of tritium produced by man is now
about equal to the natural steady-state inventory.
IV. Applications of tracer techniques to the
study of physical processes in the sea and
atmosphere
In this section we describe a few of the more
obvious applications of the tracer techniques
and isotopes described in the previous sections
to specific problems of transfer phenomena in
the oceans and atmosphere. The topics are sub-
divided in terms of the isotopes discussed, in
order to facilitate reference to points in pre-
ceding sections and parts of this section.
Carbon 14
Carbon 14 is perhaps the most useful of the
isotopic tools available for geophysical and
geochemical studies, especially when used in
conjunction with oxygen 18 data; the 5700
year half-life and the universal distribution of
carbon in organic and inorganic reservoirs make
it ideal for such purposes. The most obvious
application of immediate interest is the dating
of the bicarbonate of the deep-sea waters, in
order to determine the mixing rate of the
oceans. Unfortunately, only one definitive set
of measurements of this type has been made,
namely the U. S. Geological Survey laboratory
measurements of waters east of the Lesser An-
tilles at approximately 57° W. and 16° N.,
made by M. Rubin (personal communication) .
These data are shown below:
Carbon 14
Depth (meters) age (years)
Surface 652
640 634
1640 628
1750 841
114
Atomic Radiation and Oceanography and Fisheries
The absolute values are probably not better
than ±150 years, but the relative values are
more precise. The age of the surface bicar-
bonate is somewhat older than the 400-year
average age mentioned in Part II as the result
of slow transfer of atmospheric carbon into the
sea, perhaps as a result of local conditions;
however, the important figure is the age dif-
ference between surface and deeper waters and
it is unfortunate that still deeper waters were
not sampled. The importance of a great many
vertical profiles of this sort from both oceans,
and their fundamental import for knowledge of
the mixing rates in the ocean, is obvious.
Because of the requirements of steady state
balancing, the amounts of water transferred,
per unit time, downward and upward through
the thermocline in the sea must be equal, but
because the mixed layer contains only about
2 per cent of the sea, this balance requires that
a water molecule remain, on the average, some
50 times longer below the thermocline than
above. As a consequence of this relationship,
an uncertainty of 10 years in the residence time
of material in the mixed layer results in an
uncertainty of 500 years in the residence time
of the material below the thermocline, consid-
ering the world average rate of general cross-
thermocline mixing of the substance. As we
shall see below, the half-life of radiocarbon
happens to be so long, that considerations of
the extensive data on C^* distribution in the
atmosphere, biosphere, and mixed layer of the
sea, do not yield important information on the
internal mixing rate of the ocean itself. In fact,
the distribution of tritium above the thermocline
of the sea furnishes a much more precise esti-
mate of the general turnover time of water in
the deep sea.
Thus the application of radiocarbon analysis
to mixing problems within the sea itself can
be made only by actually getting below the
mixed layer and studying the deep-sea distribu-
tion of C^* directly; such studies, coupled with
chemical analyses and physical data serving as
parameters for the identification of continuous
water masses, will probably prove to be the
most fruitful method for the delineation of
large scale mixing phenomena in the sea.
On the other hand, the distribution of radio-
carbon in the atmosphere and mixed layer of
the sea is strongly dependent on the rate of
exchange of carbon dioxide between the atmos-
phere and sea, and from a study of the relation-
ship between the exchange rates and the radio-
active decay rate, it is possible to derive rather
precise values for the flux of carbon into the
sea and downward through the thermocline.
For such calculations it is necessary to assume
a model of the atmosphere-sea system based on
simplifying assumptions as to the nature of the
sea below the thermocline. Calculations of this
type, outlining the factors affecting the natural
distribution of radiocarbon, have recently been
made by Suess (1953), Arnold and Anderson
(1957), Craig (1957 (a)), and Revelle and
Suess (1957) . The conclusions of these papers,
though reached by various means, are quite
similar, and we shall briefly summarize the gen-
eral results.
There are two empirically observed effects,
of different origin, by which factors aflfecting
the natural distribution of radiocarbon may be
evaluated. The first of these is the observation
that the carbon in the surface layers of the sea
(bicarbonate, shell, and organic matter) has an
apparent age of about 400 years relative to the
terrestrial wood used as standards for radio-
carbon dating. The second is the observation
that contemporaneous wood has a radiocarbon
activity some 2 per cent lower than the activity
of 19th century wood, corrected for age to the
present date. This decrease in activity, reflect-
ing the contribution of C^* free CO2 to the
atmosphere by the combustion of fossil fuel,
was first found by Suess (1953) and we shall
refer to it as the Suess effect.
The "apparent age" of carbon in the mixed
layer of the sea has been measured on Atlantic
ocean samples (and one Pacific sample) by
Suess (1954), and on Pacific ocean samples
around New Zealand by Rafter (1955). The
average age determined by Suess is 430 years,
while that of the Pacific samples was reported
by Rafter as only 290 years. However, the
Suess measurements are relative to the 19th
century wood standard, corrected for decay to
the present, while the Rafter measurements
were made relative to a contemporaneous stand-
ard which has suffered a decrease in activity
due to the Suess effect. Measurement of the
effect in the New Zealand standard shows that
110 years must be added to the ages reported
by Rafter (1955) in order to correct for this
effect and make the ages comparable to those
reported by Suess (Rafter, manuscript in press) .
Chapter 11
Tracer Studies of the Sea and Atmosphere
115
Thus the average ages reported for the two
oceans are in almost exact agreement, and we
may consider the 400 year apparent age well
established as a world-wide phenomenon.
The 400 year apparent age of mixed-layer
carbon is simply a less meaningful way of
stating that the radiocarbon activity of mixed-
layer carbon is 5 per cent lower than the ac-
tivity in modern wood, uncontaminated by the
Suess effect. Actually it is observed that the
activities in wood and in surface ocean carbon
are measured to be the same, but the measure-
ments must be corrected for natural isotopic
fractionation in the physical and chemical proc-
esses involved in the carbon cycle (see section
on carbon 13 variations). Marine shells con-
centrate carbon 13 by 2.5 per cent relative to
terrestrial wood, and must therefore concentrate
carbon 14 by 5 per cent; since this concentra-
tion factor is not observed, we see that the
activity of carbon in the mixed layer is, in fact,
5 per cent lower than expected. The relation-
ships between carbon 13 and carbon 14 varia-
tions expected on theoretical grounds, and on
the basis of laboratory measurements, were dis-
cussed in detail by Craig (1954) who showed
that the 5 per cent discrepancy must be the
result of slow transfer of carbon from the
atmosphere to the sea, and cannot be explained
by any other cause. Rafter (1955) verified the
conclusion that the carbon 14 difi'erence be-
tween atmospheric CO^ and wood must be twice
the carbon 1 3 difference, by direct measurement.
The exchange rate of carbon dioxide between
atmosphere and sea may be deduced from con-
siderations of the steady state relationships be-
tween the exchange rate and the radioactive
decay rate; this type of evaluation is independ-
ent of considerations based on the magnitude
of the Suess effect and the kinetics of the
transient state. The general equations govern-
ing the transfer of a radioactive isotope between
its various exchange reservoirs have been given
by Craig (1957(a)) in terms of the rela-
tionship between the uniform activity which
would be observed if all of the sea and the
atmosphere were mixed together at a rate in-
finitely faster than the radioactive decay rate,
and the percentage deviations from this uni-
form activity which are actually observed in
the different reservoirs. Mixing rates are ex-
pressed in terms of the residence time of a
molecule in a particular reservoir, which cor-
responds to the operational definition of flush-
ing time or replacement time, used by oceanog-
raphers, and, for the first order processes
with which we are concerned, to the reciprocal
of the exchange rate constant.
The constant radioactive decay rate of carbon
14 furnishes a built-in clock which monitors
the transfer rate of carbon between its various
reservoirs. For example, if a barrier is inter-
posed between the atmosphere and sea, so that
the transfer rate of carbon between these reser-
voirs is slowed down, the radiocarbon atoms
formed in the atmosphere have less probability
of getting into the sea and thus of leaving the
atmosphere by physical removal. However, the
steady state requires that the total number of
C^* atoms leaving the atmosphere by all mech-
anisms be equal to the production of radio-
carbon atoms by the cosmic rays, and thus the
number undergoing radioactive decay in the
atmosphere must increase. The number of
radioactive atoms decaying per unit time is a
constant fraction of the total number present
(the exponential decay law), and therefore the
piling up of radiocarbon in the atmosphere
because of such an exchange barrier results in
an increase in the number decaying in just the
way required to maintain the steady state secu-
lar equilibrium with the production rate. The
percentage increase in the C^* activity of the
atmosphere is a function of the ratio between
the exchange rate and the decay rate, or, what
is the same thing, between the atmospheric
residence time and the radioactive mean life.
Considering then, the percentage change in
the radiocarbon activity of atmospheric CO2
and terrestrial wood, relative to the activity
which would characterize these materials in the
hypothetical state of infinitely rapid mixing
between atmosphere and sea, it is found that
for each year of residence time of a CO,
molecule in the atmosphere as a result of slow
exchange, the atmospheric activity will increase
by 0.74 per cent. The activity in the sea would,
of course, decrease as a result of the slower
transfer of radiocarbon into the ocean, but since
there is some 60 times as much carbon in the
sea as in the atmosphere, the percentage de-
crease of activity in the sea will be only I/60
of the atmospheric increase, namely about 0.01
per cent, which is not observable.
We can make a more detailed model of the
carbon exchange system by breaking the sea
116
Atomic RadJatio7i and Oceanography and Fisheries
up into a two-layer ocean, taking the upper layer
to be about 75 meters deep corresponding to
the average mixed layer as actually observed
in the sea. (The 75 meter estimate was made
by Dr. Warren Wooster, who kindly studied
the question of the average depth of the mixed
layer over the year in the various areas of the
oceans.) The lower layer, extending to a depth
of 4000 meters on the average, is termed for
convenience the "deep sea," though it is of
course obvious that such a uniform layer has
little resemblance to the actual structure of the
sea below the thermocline. Nevertheless, it is
found that the consequences of such an assump-
tion about the nature of the deep sea are not
serious insofar as affecting the validity of the
calculations on the atmospheric residence time,
and the treatment of the relationships existing
between the atmosphere, mixed layer, and main
body of the sea, is of course improved im-
mensely by assuming such a model. If we then
add a barrier between the mixed layer and the
deep sea, representing slow mixing across the
thermocline, the radiocarbon is further piled
up in both the atmosphere and the mixed layer,
in the same manner as previously described.
Calculation shows that the activities in the
atmosphere and mixed layer are both increased
by about 1.2 per cent, relative to the case of a
rapidly mixed, uniform sea, for each 100 years
of residence time in the deep sea, or, what is
almost the same thing, for each 100 years of
"age" of the deep water. The activity in the
deep sea is reduced by 0.05 per cent for each
100 years of deep-sea residence time.
For deep-sea residence times up to several
thousand years, the interpolation of a mixing
barrier at the thermocline in the sea causes very
close to the same activity increase in both the
atmosphere and the mixed layer, and thus the
activity difference observed between the atmos-
phere and mixed layer is sensitive only to the
atmosphere-sea exchange rate for internal mix-
ing times of the sea of the order of a few
thousand years or less. The physical evidence
discussed by Wooster and Ketchum in a sep-
arate paper in this report, and the tritium cal-
culations cited previously in this paper, clearly
show that the average mixing time of the sea
is at least within this range.
Thus the figure cited above of a 0.74 per cent
increase in atmospheric activity for each year
of atmospheric residence time, indicates that
the residence time of a COg molecule in the
atmosphere, before entering the sea, is about
7 years, corresponding to the 5 per cent activity
difference between carbon in the atmosphere
and in the mixed layer of the sea.
An independent calculation of the atmos-
pheric residence time can be made by consider-
ing only the steady-state material balance in the
atmosphere as a function of the production
rate of radiocarbon, taken as (2 ± .5)0* atoms/
cm^ sec, and the rate at which carbon enters the
sea. This calculation gives an atmospheric resi-
dence time of about 6 years. Considering the
errors to be assigned the numerical values in
both these calculations, it appears that the best
value of the atmospheric residence time of car-
bon dioxide may be taken as 7±3 years, cor-
responding to a rate constant >^(j-m = 0-l4, where
k is the fraction of the carbon in the atmosphere
transferred to the mixed layer per year (Craig,
1957 (a)).
The average annual exchange flux of carbon
dioxide, into and out of the sea each year, is
thus found to be about 2x10'^ mioles per
square centimeter of sea surface. This rate is
lower by a factor of 10,000 than the rate re-
cently obtained by Dingle (1954) from consid-
eration of the various rate constants involved,
and the discrepancy thus serves to emphasize
the power of natural isotopic studies to yield
quantitative data, as compared with more tra-
ditional methods.
An entirely independent calculation of the
atmospheric residence time, not based on steady-
state considerations, may be made from the
magnitude of the so-called Suess effect described
previously. It is known that since the begin-
ning of the industrial revolution, man has added
an amount of carbon dioxide to the atmosphere
by fuel combustion equivalent to about 12 per
cent of the amount originally present. The
degree of dilution of radiocarbon activity in
contemporaneous wood by incorporation of C^*-
free COo, measured relative to the activity of
19th century wood, is then a measure of the
rate at which the dead CO2 has been removed
from the atmosphere into the sea. The first
measurements of this effect, made by Suess
(1953), indicated a dilution of about 3 per
cent, and from these data Suess deduced an
atmospheric CO^ residence time of 20-50 years.
More recent and extensive measurements by
Suess (1955) have shown that the figure of
Chapter 11
Tracer Studies of the Sea and Atmosphere
117
3 per cent is higher than the average world-
wide figure, and represents an increased local
contamination in trees growing near sites of
industrial activity. The latest measurements in-
dicate a world-wide effect of about 1 .7 per cent.
Revelle and Suess (1957) have discussed the
relationships between the exchange rate, the
Suess effect, the effect of an increase in the
atmospheric CO, content on the atmospheric
and oceanic reservoirs, and the buffering effect
of the sea water alkalinity on carbon transients.
They conclude that, all things considered, the
residence time of COg in the atmosphere, rela-
tive to exchange with the sea, is of the order of
10 years. Though the uncertainty in their esti-
mate is a good deal larger than in the case of
the steady-state considerations discussed above,
the close agreement of the figures obtained by
these different considerations is gratifying, and
indicates that the factors governing the natural
distribution of radiocarbon are now fairly well
understood.
The size of the terrestrial biosphere and the
annual rate of photosynthesis on land have been
estimated by Schroeder and Noddack, and from
their figures it appears that the terrestrial plants
consume about 3 per cent of the atmospheric
CO2 per year, corresponding to an atmospheric
residence time before entrance into the bio-
sphere of 33 years. With a residence time of
7 years, prior to exchange into the sea, the total
residence time of a CO2 molecule in the atmos-
phere is 6 years, after which it goes either into
the sea (9 chances out of 11) or into the ter-
restrial biosphere (2 chances out of 11). Thus
the carbon dioxide flux into the sea is about
4.5 times larger than the flux into the biosphere,
and about 82 per cent of the COo leaving the
atmosphere goes into the sea, while only about
18 per cent goes into the terrestrial plants. This
ratio represents a considerable departure from
previous estimates, and indicates that the spatial
distribution of plants and soils is probably not
the dominant factor in determining the steady-
state CO, concentration in the atmosphere. In
fact it appears more likely that the spatial pat-
tern of absorption and release of CO„ by the
sea, and the seasonal variations in this pattern,
are the dominant factors.
The various considerations outlined above are
all consistent with any deep-sea residence time
of carbon up to a few thousand years, and do
not yield any closer estimate for this figure.
Recent unpublished data by Broecker and co-
workers at the Lamont Geological Observatory
indicate that the bicarbonate of deep ocean
waters probably averages about 8 per cent lower
in C^* content than the surface mixed layer,
corresponding to a radiocarbon "age" of the
order of 670 years. However, considerations by
Craig (in press), based on a second order
oceanic model in which the deep sea reservoir
is exposed to the atmosphere in high latitudes,
show that about half of the radiocarbon in the
deep sea is derived directly from the atmosphere.
The other half enters the deep sea from the
surface mixed layer of the ocean by the mixing
and interchange of water.
Because of this dual source of radiocarbon,
the residence time calculated for carbon in the
deep sea is only about half of the actual resi-
dence time of a water molecule in the deep sea
relative to the mixed layer; thus the deep-sea
residence time of water relative to the mixed
layer is probably of the order of 1000 years as a
world-wide average. However the actual inter-
pretation of such residence times in the sea is
quite complicated, and reference is made to the
paper cited above for a detailed discussion of
carbon and water residence times.
Deuterium and Oxygen 18
As discussed previously, the stable isotopes
are of great value in the study of ocean water
mixing as additional parameters related to salin-
ity. One particular case in which information
can be gained from such studies is the problem
of meltwater dilution of the oceans in the polar
regions. A salinity decrease can be caused by
addition of fresh water from river runoff, or
from the melting of sea ice, and from salinity
data alone these sources cannot be differentiated.
However, the isotopic composition of the two
sources is quite different; the sea ice should
have a composition quite similar to that of the
ocean water, while, as shown above, the runoff
of rivers in polar areas is greatly depleted in
deuterium and oxygen 18 relative to ocean
water. Thus from consideration of salinity and
isotopic data taken together, a quantitative eval-
uation of the mixing conditions can be made.
Friedman of the U. S. Geological Survey is
currently studying such problems with deute-
rium analyses of Atlantic waters. The isotopic
data should also be useful in material balance
118
Atomic Radiation and Oceanography and Fisheries
studies over various sections of the oceans,
because of the latitudinal decrease in deuterium
and oxygen 18 concentration of oceanic water
vapor, and the known temperature dependence
of the isotopic selection in evaporation.
Craig, Boato, and White (1956) have shown
how deuterium and oxygen 18 measurements
can be usesd to determine the proportions of
juvenile or magnetic water to reheated ground
water in thermal springs, and volcanic steam.
These isotopes, together with tritium, have im-
portant applications to practically all hydrologic
problems, and the exploitation of such tech-
niques has barely begun.
Tritium and Strontium 90
As described in Part II, the tritium measure-
ments made by Libby and his co-workers fur-
nish an independent value for the mixing rate
in the sea; more detailed studies will surely
provide important information on the oceanic
mixing phenomena. The production of tritium
in thermonuclear explosions provides an iso-
topic tracer for determination of atmospheric
mixing times across the face of the earth and
storage times in the atmosphere.
The measurement of the world-wide distribu-
tion of strontium 90 produced by nuclear deto-
nations has been done by W. F. Libby and
E. A. Martell at the University of Chicago.
The results of their work have recently been
described by Libby (1956 a, b). The radio-
nuclides produced by low-yield kiloton weapons,
and part of the activity produced by the higher-
yield megaton weapons, are distributed within
the troposphere in a belt corresponding to the
latitude of the test site. This material has a
tropospheric life which is a function of particle
size; some of the activity may circle the earth
two or three times within the hemisphere in
which it was produced before being washed out
of the atmosphere. However, the mean life of
this tropospheric material is only a few weeks.
More interesting is the fact that Libby and
Martell find that half or more of the radio-
strontium produced by the megaton weapons
is distributed over both hemispheres and falls
out much more slowly, the mean storage time
in the atmosphere being of the order of ten
years. They conclude that this material is car-
ried up into the stratosphere, above the tropo-
pause, where it is mixed horizontally in a time
comparable to the storage time at this level.
The contrast between the distribution of
megaton weapon produced radiostrontium and
tritium is extremely significant. As noted in
Part III, Begemann and Libby find that the
artificially produced tritium is confined to a
single hemisphere and is rapidly washed out
of the atmosphere; this material thus follows
the pattern of the activities which remain in
the troposphere. The tritium and fission prod-
uct data thus show that over a period of months
there is virtually no cross-hemispheric mixing in
the troposphere, but that over a period of years
the stratosphere is well-mixed horizontally. The
failure to detect tritium carried up into the
stratosphere with the megaton weapon produced
radiostrontium may be due to the instantaneous
combustion of tritium to HTO by the catalytic
action of the oxides of nitrogen produced in
the blast (Harteck, personal communication).
As water, the tritium may be frozen out at the
lower cold trap, in the tropopause, where the
temperature is about — 70°C, and thus pre-
vented from entering the stratosphere.
On the other hand, Martell points out (per-
sonal communication), that the thermal energy
of the fireball is still quite large by the time a
fireball produced by a megaton weapon has
risen to the height of the tropopause. In order
for HTO to condense and thus be trapped be-
low the tropopause, it is necessary to assume
that the lighter constituents of the fireball have
diffused into the cooler outer layers. Martell
suggests that if such is the case, then the actual
explanation may be that the portion of the cloud
containing the HTO may not have sufficient
thermal energy to penetrate the tropopause, and
as a result, this portion of the cloud merely
expands horizontally below the tropopause.
V. Conclusions
From the discussion in the preceding parts of
this report, it is apparent that the advent of
manmade nuclear reactions introduced a series
of geophysical and geochemical experiments on
a vast scale. It is fortunate that the introduction
of such experiments came at a time when geo-
chemists were well underway towards the under-
standing of natural transfer phenomena by
means of studies based on naturally CKCurring
isotopes in their steady state biogeochemical
cycles. It should be clear that the need for this
knowledge is such that every effort should be
Chapter 11
Tracer Studies of the Sea and Atmosphere
119
made to prevent irreversible procedures which
might ehminate the opportunity to study such
mixing at the natural level where evaluation of
the long term variables is possible. On the other
hand, it is also evident that the introduction of
artificially produced radioisotopes into the geo-
sphere has been productive of a great deal of
new knowledge that might otherwise not have
been obtained.
The importance of continuous monitoring of
the levels of such substances as tritium cannot
be overemphasized. As an example of this, it
may be pointed out that one reason that carbon
14 is such a powerful tool for the evaluation
of ocean-atmosphere interaction that we have
relatively precise records on just how much dead
carbon has been produced by the combustion of
fossil fuels ; were this information not available
the use of radiocarbon in such studies would be
exceedingly difficult, if not impossible.
From the carbon 14 inventory discussed in
Part II, and assuming an average depth of
about 150 meters for the oceanic thermocline,
it appears that about 4 per cent of the carbon
14 in the sea lies above the thermocline; this
corresponds to an activity of about 10 mega-
curies. It is thus evident that introduction of
artificially produced radiocarbon in 10,000 curie
amounts above the thermocline would begin to
produce a critical level which would interfere
with the natural radiocarbon studies of such
fundamental importance. Introduction of 100-
1000 curie amounts above the thermocline
would produce activity sites which could be
traced for years, but such experiments could
not be done more than once every decade or
so if the natural level is to be preserved. It
would thus seem highly desirable that some
international body be constituted to record and
monitor the material put into the sea and the
atmosphere as wastes and for tracer experi-
ments. It is a truism to point out that a con-
taminated laboratory is rather easily replaced,
but that the laboratory of the earth scientists
is not easily renovated.
-CONCLUSIONS
Anderson, E. C. 1953. The production and
distribution of natural radiocarbon. Ann.
Rev. Nuclear Science 2:63-78.
Arnold, J. R., and H. A. Al-Salih. 1955.
Beryllium-7 produced by cosmic rays.
Science 121:451-453.
Arnold, J. R., and E. C. Anderson. 1957.
The distribution of carbon- 14 in nature.
Tellus 9:28-32.
Begemann, F. 1956. Distribution of artifi-
cially produced tritium in nature. Nuclear
Processes in Geologic Settings: Proceed-
ings of the Second Conference. National
Academy of Sciences — National Research
Council Publication 400:pp. 166-171.
Benioff, p. a. 1956. Cosmic-ray production
rate and mean removal time of Beryllium-7
from the atmosphere. Phys. Rev. 104:
1122-1130.
Craig, H. 1953. The geochemistry of the stable
carbon isotopes. Geochim. et Cosmochim.
Acta 3:53-92.
1954. Carbon 13 in plants and the relation-
ships between carbon 13 and carbon 14
variations in nature. /. of Geology 62:
115-149.
1957 (a). The natural distribution of radio-
carbon and the exchange time of carbon
dioxide between atmosphere and sea. Tel-
lus 9:1-11.
1957 (b). Distribution, production rate, and
possible solar origin of natural tritium.
Phys. Rev. 105:1125-1127.
In press. The natural distribution of radio-
carbon: II. Mixing rates in the sea and
residence times of carbon and water.
Tellus.
Craig, H., and G. Boato. 1955. Isotopes.
At7n. Rev. Phys. Chem. 6:403-432.
Craig, H., G. Boato, and D. E. White. 1956.
The isotopic geochemistry of thermal wa-
ters. Nuclear Processes in Geologic Set-
tings: Proceedings of the Second Confer-
ence. National Academy of Sciences —
National Research Council Publication
400 :pp. 29-38.
Currie, L. a., \V. F. Libby, and R. L. Wolf-
gang, 1956. Tritium production by high-
energy protons. Phys. Rev. 101:1557-
1563.
De Vries, H. 1956. Purification of CO, for
use in a proportional counter for i*C age
measurements. Appl. Sci. Res. (B) 5:
387-400.
Dingle, A. N. 1954. The carbon dioxide
exchange between the North Atlantic ocean
and the atmosphere. Tellus 6:342-350.
Dole, M., G. A. Lane, D. P. Rudd, and D. A.
Zaukelies, 1954. Isotopic composition
120
Atomic Radiation and Oceanography and Fisheries
of atmospheric oxygen and nitrogen. Geo-
chim. et Cosmochim. Acta 6:65-78.
Epstein, S., and T, K. Mayeda. 1953. Varia-
tion of O^^ content of waters from natural
sources. Geochim. et Cosmochim. Acta
4:213-224.
Fireman, E. L., and F. S. Rowland. 1955.
Tritium and neutron production by 2.2-
Bev protons on nitrogen and oxygen. Phys.
Rev. 97:780-782.
Friedman, I. 1953. Deuterium content of
natural water and other substances. Geo-
chim. et Cosmochim. Acta 4:89-103.
Harteck, p. 1954. The relative abundance
of HT and HTO in the atmosphere. /,
Chem. Rhys. 22:1746-1751.
Kaufman, S., and W. F. Libby. 1954. The
natural distribution of tritium. Rhys. Rev.
93:1337-1344.
Lane, G. A., and M. Dole. 1956. Fractiona-
tion of oxygen isotopes during respiration.
Science 123:574-576.
Libby, W. F. 1955. Radiocarbon dating. Univ.
of Chicago Press, Chicago: 2nd edition,
175 pp.
1956(a) Radioactive fallout and radioactive
strontium. Science 123:656-660.
1956(b) Radioactive strontium fallout. Rroc.
Nat. Acad. Sci. 42 :?> 65-590.
Morrison, P., and J. Pine. 1955. Radiogenic
origin of the helium isotopes in rock. Ann.
New York Acad. Science 62:69-92.
Rafter, T. A. 1955. ^*C variations in nature
and the effect on radiocarbon dating. New
Zealand J. Sci. Tech. (B) 37:20-38.
Rakestraw, N., D. Rudd and M. Dole. 1951.
Isotopic composition of oxygen in air
dissolved in Pacific ocean water as a func-
tion of depth. /. Amer. Chem. Soc. 73:
2976.
Revelle, R., T. R. Folsom, E. D. Goldberg,
and J. D. Isaacs. 1955. Nuclear science
and oceanography. Intern. Conf. on Peace-
ful Uses of Atomic Energy, Geneva, also
Contr. Scripps Inst. Ocean. N. S. 794:
22 pp.
Revelle, R., and H. E. Suess. 1957. Car-
bon dioxide exchange between atmosphere
and ocean and the question of an increase
in atmospheric COg during the past dec-
ades. Tellus 9:18-27.
Suess, H. E. 1953. Natural radiocarbon and
the rate of exchange of carbon dioxide
between the atmosphere and the sea. Nu-
clear Processes in Geologic Settings. Na-
tional Academy of Sciences — National
Research Council Publication, pp. 52-56.
Suess, H. E. 1954. Natural radiocarbon meas-
urements by acetylene counting. Science
120:5-7.
1955. Radiocarbon concentration in modern
wood. Science 122:415-417.
Von Buttlar, H., and W. F. Libby. 1955.
Natural distribution of cosmic-ray pro-
duced tritium. 2. /, Inorganic and Nuclear
Chem. 1:75-91.
Chapter 12
ON THE TAGGING OF WATER MASSES FOR THE STUDY OF PHYSICAL
PROCESSES IN THE OCEANS^
Theodore R. Folsom, Scripps Institution of Oceanography, La Jolla, California
and
Allyn C. Vine, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts
Finding, identifying, and plotting the courses
of characteristic masses of water in the oceans
are major activities of the physical ocea-
nographer. Assistance from the new techniques
that have come with the use of radioactive
materials has been welcomed by him; some of
these techniques have already been put into
service for tracing the water. It is not gen-
erally realized how much experience has been
gained, beginning with the 1946 tests in Bi-
kini Lagoon, in tracing water masses contam-
inated with radioactive materials from weapons'
tests. And many thoughts are now turning
toward the radioactive tagging of ocean water
by other means in regions where knowledge of
underlying physical processes are meager, espe-
cially in the very deep waters. Proposals for
the disposal in the sea of atomic energy wastes
cannot be properly evaluated until estimates
can be improved concerning the motion of this
deep water.
Many of the advantages (familiar in the
laboratory) of using radioactive identifying tags
can be realized at sea, even though rendered
difficult by the very large physical dimensions
of the oceans. What appeals most to the ocea-
nographer is his new ability, under certain cir-
cumstances, to make very rapid identifications
of water lying on the surface or deep below his
ship; thus allowing large volumes to be sur-
veyed in three dimensions and in more detail
than ever before possible.
Three layers in the ocean are distinguished
1 Contribution from the Scripps Institution of
Oceanography, New Series, No. 905.
Contribution No. 929 from Woods Hole Oceano-
graphic Institution. Part of Table 2 was computed
with the collaboration of John Harley of AEC, New
York City Operations Office, who gave much other
counsel for which the authors are grateful.
clearly by structure and behavior: the mixed
layer near the surface; the intermediate layer
lying just below wherein the temperature changes
rapidly with depth (this thermal stratification
bringing about great stability) ; and finally, the
large, nearly uniform bottom water mass ex-
tending to the sea floor with so little variation
in density that very stable stratification is not
possible. Each water mass reacts differently
when disturbed, and therefore, mixing occurs
differently in response to currents and mass
intrusions. Experiments conducted in any one
of these domains must take into consideration
the special features that exist, and must call
upon equipment most suited to these sections.
Equipment specialized for radiological survey
work in any of these oceanographic domains is
still primitive. However, it can be said that
equipment for detecting and measuring radia-
tion is not a bit less highly developed than are
the equipment and techniques needed for navi-
gating a ship, and for maneuvering detectors
at sea, especially at great depth. So much in-
formation now can be reported by radiological
means in a short time that a ship now has more
reason than heretofore for precise navigation.
In some cases, the depth and position of the
detector relative to the ship must be known
instantly, and almost always must be controlled
far better than has been accepted by traditional
hydrography. It is difficult to record data in
full detail in many cases, and in others it is
difficult to evaluate features rapidly enough to
alter maneuvers to best advantage; an ocea-
nographer can now expect to be aware of a
strongly active layer in less than one second
after his electronic probe makes contact, and
he even may make use of a fast moving airplane
to outline radioactive areas on the surface.
121
122
Atomic Radiation and Oceanography and Fisheries
Instrument Sensitivity and Natural Backgrounds
Many promising measuring schemes have
been proposed. However, it is profitable to com-
pare the equipment and techniques which have
been used already at sea. At the top of Table 2
is presented the background radiations coming
from cosmic rays and from the natural potas-
sium in the sea, and the activity level now
believed tolerable for drinking water also is
given for comparison.
At the bottom of Table 2 are listed, in the
brief numerical form in which they are com-
monly stated, the sensitivities of three measur-
ing techniques which actually have been used
for radiological exploration at sea. Many as-
pects of the measurement problem are over-
simplified by a comparison of this sort, but the
table does indicate that present shipboard beta
analysis is capable of measuring beta tracer ac-
tivity below the background beta activity due
to the potassium in the sea water, whereas
gamma detectors so far have been limited at
levels above the gamma backgrounds of the
sea. On surveys covering large distances, such
as on Operation TROLL (U. S. Atomic Energy
Commission 1956), and on the SHUNKOTU
MARU Expedition (Mujoke, Sugiura, and Ka-
meda 1954), there is ample time for water
analyses, and advantage can be made of beta
techniques. Nevertheless, there are many circum-
stances where direct measurements by gamma
devices are necessary for rapidly locating small
contaminated water masses, and it is likely that
gamma techniques will be perfected so as to
allow use at levels far below their present
capability.
There are occasions at sea in which a gamma
detector must indicate the presence of tracer
activity within a few seconds after making con-
tact. The limitations imposed by this sort of
time restriction in the presence of statistical
fluctuations in the signals are discussed in Ap-
pendix A, and are summarized in Table 3.
Other important details concerning the radio-
active background in the sea have not been
thoroughly explored. It may be too late to
estimate the background level that existed a
decade ago for some isotopes, and this should
not be forgotten in planning future surveys.
Of particular interest are background condi-
tions near the sea floor where radium and
thorium activity are known to accumulate in
sediments; but little is known in detail about
the lateral distribution of bottom activity.
More complete utilization of iveapons' tests for
the marine sciences
It appears likely that large weapons will
continue to be tested in oceanic areas and that
radioactive materials will be strewn from time
to time over the surface of the sea. Valuable
oceanographic data already has come from such
sources ; for example, direct measurements have
been made of the rate of mixing downward
from the surface to the thermocline, and also,
direct information has been obtained regarding
mass motion and lateral mixing. One special
feature of benefit in studying weapons tests is
the unique initial boundary condition provided
by the arrival of fallout activity almost simul-
taneously over an area having dimensions very
large compared with the depth of water in-
volved; downward mixing appears as a rela-
tively simple phenomena following this initial
condition, and can be studied under almost
ideal circumstances.
Two expeditions mentioned above have
proven that further information concerning
lateral mixing and flow can be gained for many
months after a weapons' test, and obviously
this fact should be exploited fully by marine
scientists of all nations. Ancillary benefits
might come from more or less fixed monitoring
stations; if, for example, following the 1954
test, repeated sampling had been done off Guam
it would have furnished data of value for in-
terpolating observations made in the two fol-
low-up cruises mentioned.
Bottom exploration following weapons' tests
has not been given deserved attention, and in-
sufficient attention has been paid to getting
even purely oceanographic information from
these sources into the form needed by those
people who are charged with making decisions
regarding the ominous waste disposal problem.
Hazards involved in the deliberate tagging of
ocean waters
Safety of the research staff is always a con-
sideration; at sea because of special circum-
stances the handling of extremely large amounts
of activity is not too difficult or hazardous. Pro-
tection can be secured very cheaply by towing
the larger sources of radioactivity aft of the
Chapter 12
Tagged Water Masses for Studying the Oceans
123
ship, preferably slightly submerged on a suit-
able barge or special vessel. Bringing large
quantities of activity to the waterfront prom-
ises to be more expensive, but practical experi-
ence in this should be valuable for later plan-
ning of large-scale disposals.
The more controversial question of how
much radioactivity can safely be introduced into
the sea is not without reasonable solutions; but
the recommendations depend upon the cir-
cumstances, especially, upon the particular part
of the oceans to be studied. At the outset,
barren areas of ocean rather than those produc-
tive of things leading to human food must
be selected since the former can yield equally
good information regarding purely physical
phenomena.
Deliberate tagging of surface waters (^Opera-
tion PORK CHOP)
Surface waters mix in a turbulent manner
due to forces not yet fully understood. Better
knowledge of this layer is badly needed justi-
fying the consideration of water tracing experi-
ments involving introduction of fairly large
amounts of activity. Greatest care must be
exercised here because these waters are those
most close to humans, in several senses.
Rate of mixing to the bottom of the mixed
layer, and rate and character of lateral motion
as functions of the usual parameters of the sea
are of most immediate interest, and observa-
tions lasting even a few days or few weeks
would be of great value at the outset, especially
if repeated frequently. A simple surface water
experiment now will be proposed in briefest
possible outline.
Figure 1 presents schematically some of the
procedure which might be used and some of
the phenomena to be expected. Guided by
suitable navigational aids, here represented by
deep-anchored buoys No. 1 and No. 2, the ship
A proceeds on a straight course while dropping
two quantities of radioactive materials (a and
a') mixed with enough surface water to leave
near the surface a small contaminated patch
having nearly neutral buoyance. These are
essentially point-source initial conditions in this
scale of dimensions; although, they are not as
convenient as the plane-source initial conditions
BUOY » 2
OPERATION "PORK CHOPS'
Figure 1
124
Atomic Radiation and Oceanography and Fisheries
provided by fallout, they have some mathemati-
cal simplicity. It would appear economical and
informative to drop two sources almost simul-
taneously, some distance apart — say one to ten
kilometers; this would permit large-scale ad-
vection also to be studied at little extra ship
cost.
From the sources s and s' will grow a larger
more dilute patch of water finally ceasing to
penetrate rapidly downward at depth d. The
rate and lateral spread prior to this time as
functions of wind velocity are of special in-
terest. After further downward penetration is
retarded, the areas a and a' move and expand
to the larger areas A and A' conserving most
of the original radioactive material, and the
product of activity and area should be almost
constant after correction is made for the known
rates of decay of radioactive constituents.
Dual ship operations
Experience has shown that operations on the
scale of this sort can scarcely hope to be suc-
cessful unless more than one ship is used ; even
with the best facilities one ship may lose con-
tact with the invisible patch and waste valuable
time locating it. One ship, X, must stay in or
near the tagged mass while the other one, Y,
may survey the area in detail, inspecting sections
across the mass, studying the bottom for ref-
erence features, and chasing missing buoys if
necessary.
Ultimate disposal of hazard in surface waters
Reduction of activity to a level below that
of the natural activity of sea water is one cri-
terion which has been used for planning dis-
posals (Glueckoff 1955), and this is fairly
reassuring provided the specifically dangerous
and the long-lived activities are eliminated, for
example, after radiostrontium and radiocesium
are removed from raw fission wastes. Present
evidence permits the conclusion that in the
open ocean, when winds are above the critical
white-cap level and under circumstances where
mixing ceases at a depth of about 30 to 50
meters, as much as 1,000 curies would mix to
a safe dilution in less than 40 days. An ex-
ample of the dispersal rate in the open sea
will now be given.
Brief outcome of an experimental tagging of
surface waters in the open sea
Surface water made active by introducing fis-
sion products concentrated within a few square
kilometers was intercepted by a ship 36 days
after inoculation and traversed for 10 days.
After corrections were made for the drift of
the water during the survey, and for radioactive
decay, a synoptic picture could be drawn roughly
locating the contours of activity. This estimate
of radioactive distribution was referred to the
time of 40 days after the start of dispersal.
The contamination had mixed significantly
only to about 30 to 60 meters, although the
thermocline lay nearer to 100 meters depth.
The following tabular description of this synop-
tic sketch can be made.
TABLE 1 Approximate Distribution of Radio-
activity Found in the Surface Waters of the
Open Seas 40 Days After Being Introduced Sud-
denly AS A ""Point Source." (A Synoptic Picture
Computed from Measurements Made on
Several Different Days.)
Concentration
Areas inside of radio-
Areas inside con- the contours activity (as
tours of equal as percentages per cent of
concentration of the area of the maximum
in square the maximum concentration
kilometers. contour. measured).
40,000 (km^) 100% 10%
24,000 65 20
14,000 38 30
8,000 22 40
800 2 60
490 1 80
35 0.1 100
At the end of 40 days, the center of gravity
of this distribution was about 120 miles from
the point of inoculation and the pattern was
about four times longer than broad. The wind
was 3 and 4 of Beaufort's scale for the first
20 days, but was much calmer for the last 20
days.
If the average mixing depths are taken as
50 meters, then, 1,000 curies distributed over
40,000 square kilometers would result in an
average concentration of 1.5 X 10-^°/yu,c/ml.
This would certainly be safe sea water in most
senses; and even in the smaller areas where
much less than the average dispersal took place
the water should also be safe. In fact, the
experiment indicated that it is likely that after
40 days, following the introduction of 1,000
Chapter 12 Tagged Water Masses for Studying the Oceans 125
curies of activity into the surface waters of the by considerations of hazard to humans. Two
open sea, only about 0.1 per cent of the total more difficult experiments will now be de-
area should retain contamination above the scribed,
tolerance concentration permitted for potable
water, and even in this small region the residual investigations in the thermocline layer by use
artificial activity would amount to less than the ^j radioactivity
normal natural activity of sea water.
It is evident from Table 2 and Table 3 that The thermocline lying between perhaps 100
shipboard beta measurements would suffice to meters depth on an average, and 800 meters
detect the more radioactive spots if there were or more, can be thought of as being a lid which
initially 1,000 curies of slowly decaying beta restrains deeper water from reaching the sur-
activity; it is apparent, however, that direct face. Experiments in this stable region must
measurements by gamma detectors might be take into consideration the fact that any liquid
sufficient for several days or even weeks. Sur- introduced here will seek the level of its own
face experiments are by far the easiest to con- density and will then spread out in a very thin
duct and implement — they are limited largely layer. An experiment in this layer has been
TABLE 2 Approximate Sensitivities of Three Detecting and Measuring Techniques Presently
Available for Use At Sea Compared With the Activity of Sea
Water and With That of Fresh Water.
A Common background radiation levels:
d/m/1 curies/1 microcuries/ml rad/hr 2 mrad/yr ^
Activity in normal sea water due to potassium: ^
Gamma rays 70 3 X 10"" 3 X 10"* 1 X 10"^ 0.9
Beta rays 660 3.0 X 10"'" 3.0 X 10"^ — —
Maximum permissible * concentration of unknown mixed beta activities in drinking water:
Beta rays 220 l\ X 10"'° 1 X 10"^ — —
Cosmic ray background at sea surface: ^
At equator 61 — — — 33
At 55°N (mag) — — — 37
B Sea water activities at which present measurements are significant.
Shipboard water analysis ^ for mixed beta emitters, 60 minutes count after removal of potassium:
50 ± 15 2 X 10"" 2 X 10"* — —
Uuderwater gamma detector,'' 1956 scintillation rate-meter of AEC-NYOO:
220 (approx) — — 1.4 X 10"^ 1.2
(0.6 MEV gammas assumed)
Underwater gamma detector,^ 1935 geiger instruments of SIO. {counting pulses):
(See also table 3 for other cases)
Case A: Used in deep water where net background is 15 CPM, assume photons of 0.6 Mev; assume short
measurements required, t = 5 sec.
6600 3 X 10"' 3 X 10^ 3.8 X 10^ 30
Case B: Towed on surface, assume constant background 60 CPM, assume photons of 0.6 Mev; assume
long measurements permitted, t ^ 5 min.
520 2 X 10"'° 2 X 10"' 0.3 X 10^ 3
1 Assuming normal sea water has 3.8 X 10"* gk/g sea water, that beta activity is 29 d/s/gk and that
gamma activity is 3 d/s/gk.
'The rad unit is somewhat larger than the more familiar roentgen unit; 1 rad z= 1.1 roentgen approximately
for gamma rays. Values in this column were computed upon the assumption that the activity was uniformly
distributed in the water and that the detector was a meter or more from any boundary.
3 Referring to beta ray activity in rad units in roentgen units is a dangerous practice — much further spe-
cification depending upon the individual experiment is required.
* Handbook 52 of the National Bureau of Standards. The values given refer to the case where the nature of
the activity is unknown; certain radioisotopes can be tolerated at much higher levels.
5 See Table 1 in the accompanying paper "Comparisons of Some Natural Radiations Received by Selected
Organisms" by T R. Folsom, and John H. Harley for variation of cosmic rays with depth and altitude.
s Cosmic rays are counted by most geiger counters at the average rate of approximately one count/min/sq
cm of counter area.
^ This information was supplied by J. H. Harley from personal communication with H. D. LeVine of
the New York City Operations Office of the Atomic Energy Commission who designed this equipment.
s This detector was not intended previously for use at low intensities, but rather for measuring a wide
range of intensities of gamma rays. Additional geiger tubes might easily be added to increase the sensitivity
by at least five fold. Still more sensitive gamma devices are now used in oil well logging.
126
Atomic Radiation and Oceanography and Fisheries
TABLE 3 Comparison of Minimum Detectable Concentrations Using Several Measuring Times
AND Assuming Several Backgrounds
(a) Minimum detectable anomolous activity if potassium of the sea produced the only background, i.e.,
B=: 1.2 X 10"^ gammas/sec/ml.
Rads/hour
Counting time Minimum detectable Net signal , ^ ^
in sees. concentration counts/min Total net Photons Photons
t 7/sec/ml = 7/min/l CaVe=30Ca counts 30Cat .6 mev 1.5 mev
Ca
3 19 11,000 5.7 17 6.5X10^ 16X10^
5 11 6,600 3.3 17 3.8 9.5
60 010 600 0.3 18 .3 .8
180 0039 230 .12 22 .13 .33
300 0026 160 .078 23 .09 .22
600 0016 _ 99 .048 30 .06 .14
Very large 0.025/ Vt
(b) Minimum concentration detectable if backround were 15 CPM, i.e., an actual background signal ex-
perienced in deep water.
Cb
3 19 11,000 5.7 17 6.5X10"^ 16X10-"
5 11 6,600 3.3 17 3.8 9.5
60 010 590 .29 17 .33 .84
180 0058 350 .17 32 .20 .50
300 0049 290 .15 45 .17 .42
600 0032 190 .096 58 .11 .28
Very large 0.067/ Vt~
(c) Minimum detectable concentration if total background were 60 CPM, i.e., an actual background signal
experienced at the sea surface.
Cc
3 205 12,000 6.1 18 7.1 X 10"^ 18 X 10"^
5 133 8,000 4.0 20 4.6 12
60 0222 1,330 .67 40 1.9 7.5
180 0116 700 .35 63 .4 1.0
300 0087 520 .26 78 .3 .74
600 0059 354 .17 102 .2 .51
Very large 0.13/" Vt~
described in some detail by Revelle, Folsom,
Goldberg, and Isaacs (1955), and discussed in
several of the accompanying papers. It will be
discussed here only in the matter of difficulty
of survey. Although mixing is known to be
very slow in the thermocline, it is not certain
how direct is the path from this fringe biosphere
to human food supply, so that the hazard of a
long remaining concentration of activity is not
easily evaluated. Revelle et al., prefer to sug-
gest the experimental use of the conservative
amounts of 10 to 100 curies, and they then
show that such small sources of radioactivity
might be practical none the less.
Actual field experience has shown that layers
as thin as one or two meters thick are extremely
difficult to sample for water analyses even after
being located by gamma ray detectors. Folsom
(1956) has emphasized that future deep sur-
veys with radioactive tags must rely heavily
upon discovery of radioactive water by means
of gamma detectors, and has urged that special-
ized forms of these be brought to perfection.
In this particular layer, geometric factors
are not adverse for maneuvering a detector into
the water mass to be studied ; a probe is dropped
rapidly and more or less vertically so as to
intersect and pierce a rather broad horizontal
lamina, sharply confirming the activity. Some
difficulty would be encountered in holding the
probe in the thin layer long enough to permit
accurate measurements after the activity falls
to such a low level that statistical fluctuation
becomes the predominant source of error; how-
ever, the major difficulty even at these depths
is holding the ship in the general area of active
pools of small size. Any area of less than
a square mile below the surface is a tiny detail
in the open sea, and oceanographers never be-
fore have realized how hard it is to navigate
and maneuver to study areas so small. Multi-
ship operation, the use of the best position-
Chapter 12
Tagged Water Masses for Studying the Oceans
127
locating gear, and careful crew training and
teamwork are necessary for subsurface radio-
logical surveys even at these moderate depths.
Outline of tagging experiment in the thernio-
cline layer
Figure 2 illustrates certain features which
must be considered in this region. The ship, A,
may lower a gamma sonde through an activated
pool and detect its presence by the receiving
of a signal like tliat shown on the right side of
the figure; the hydrographer may obtain a
water sample by triggering electrically a water
sampler at the moment the detector indicates
that the sampler is within the active layer. The
data in Table 3 make it clear that rapid response
is important during this sort of measurement;
a statistically significant signal must be accumu-
lated in the short period during which the
probe is passing through the active layer.
Attention is called to the need for naviga-
tional and maneuvering aids here by including
schematically the parachute-drogue C. It is
difficult to maneuver a weighted detector hori-
zontally in order to study the lateral distribution
in detail. The use is suggested of towed gamma
detectors depressed to the desired level by
hydrofoils controllable from the surface, more
or less as illustrated schematically at the left
of Figure 2. By means of a swivel-clamp, SC,
a pennant several meters long containing a row
of Geiger tubes or other gamma detectors, might
be suspended above the depressor so as to pre-
sent a vertical, linear array, thus giving a high
probability of intersecting wide lateral distri-
butions of activity. This sort of gear should not
be too awkward nor fragile for deck handling
at sea. Signals might be recorded partially, or
entirely inside the depressor, or reported to the
ship electronically or sonically.
Ship A or a sister ship with similar gear
might stay in the pool during the whole experi-
ment, however, if the pool were lost after its
depth was established, then Ship B would likely
be the first to find it again with its towed
detector.
Difficulties in sounding and exploring very deep
ivaters
Bottom exploration so far has been confined
largely to sonic plotting and sounding by solid
cable; very deep wire casts are very time con-
suming and difficult; the ship generally is
moved laterally by surface currents before the
OPERATlOM "poker CHIP"
Figure 2
128
Atomic Radiation and Oceanography and Fisheries
wire touches bottom. Oceanographers seldom
hope to place their sondes and coring tools
upon any pre-selected topographic detail of
small area. However, it is quite likely that a
technique can be perfected for dragging a de-
tecting instrument along the bottom in many
areas of the oceans' floor, and with a dragged
detector a large region might be traversed rap-
idly, and tagged water masses near the sea floor
might be located and surveyed. A proposal for
tagging bottom waters now will be outlined.
Difficulties in tagging bottom waters
Fortunately, little hazard to human popula-
tions would result from putting into the deep
bottom waters in certain latitudes almost any
amount of activity which might be readily
available in the near future, or which would be
easy to handle safely ashore and on ordinary
surface vessels. After all, these amounts would
be only the feeble forerunners of what may
have to follow.
The problem is that of displaying even a rela-
tively large radioactive source economically in
face of the immensity of the abyssal reaches.
One can think of many things which must not
be done; heavy, radioactive liquid cannot be
merely poured overboard, for example. Match-
ing density at intermediate layers or attempting
to insert a strata at a selected depth also would
appear experimentally difficult in view of the
limited knowledge presently available; an un-
equilibrated liquid mass might wander about
like a sinking dinnerplate — and soon become
lost. In the absence of the restraining forces
found in more stable waters, the pouring of
streams of dense solution downward from a
height above the bottom, or alternately the re-
leasing of lighter material upward from the
bottom would surely cause mass motion which
might not cease until the streams had moved
long distances and perhaps had curled into con-
figurations quite unsuited as initial boundary
conditions for water tracing experiments. Fur-
thermore, activity spread initially in more or less
vertical lines would make very poor targets for
detectors trailing on the end of wires three
miles long, and would be wasteful in terms of
radioactive material and of expedition time.
One might, of course, carefully select a per-
fect basin, and might gently introduce into it
a dense radioactive solution. This certainly
should be considered since only a small amount
of activity might suffice for tagging the waters
in a small basin and valuable information re-
garding motion and dispersion in basins might
result, but results would not lead to a realistic
picture of the large scale flow over bottom
which may have to disperse the wastes dumped
in the future. The results of an experiment set
up in this way would be inadequate, and, in
fact, might be misleading in a dangerous direc-
tion.
Production and use of horizontal line-sources
near the bottom
"Operation HARE and HOUND"
It is evident that distribution of activity in a
horizontal line near the bottom would be most
easy to intercept by a detector dragged along
the bottom, and it appears also to be something
which would be relatively easy to produce, and
economical. It should be possible to hold tagged
water near the bottom by mixing it with a very
dense solution; and there are two ways im-
mediately evident for effectively spreading
streaks of dense solution for long distances over
the bottom terrain.
Figure 3 illustrates the two methods proposed
for tagging bottom water, and the method pro-
posed for locating the tagged masses later. The
Ship B' is shown dragging a "Hare" D, across
the bottom leaving behind a streak of contami-
nated water. Alternately, Ship B is shown just
after it has dropped to the sea floor a specialized
water blending device which might well be
called a "quern" ^, C, which generates for a
few minutes or hours, a stream of dense, radio-
active solution on the slope of a carefully se-
lected large topographical ridge b — d ; this
stream flows away very much like one of the
submarine currents which are now called "tur-
bidity currents" by geologists. Violence of this
sort of free current might theoretically be con-
trolled through wide limits by adjusting the
densities of the solution. The essential features
of a water-tagging quern are shown in the
upper right of Figure 3. Radioactive material,
AS, is combined in predetermined proportions
with a heavy salt solution by metering pump,
P, and the two are then fed to a fan-type mixer,
and are there blended with a large volume of
1 Old English name for a mill for grinding all sorts
of things. (RuggoflF, 1949.)
Chapter 12
Tagged Water Masses for Studying the Oceans
129
OPERATION "hare AND HOUND"
Figure 3
local water. There are several reasons for pre-
ferring a design leading to inexpensive construc-
tion and single use; the cost of decontamination
of apparatus of this type would outweigh any
benefit from repeated use. Suggestion is made
of the use of a salt such as sodium nitrate which
has both high solubility, and an endothermic
heat of solution which would serve to overcome
the adiabatic heat set free during lowering. It
would appear that one or more tons of a nitrate
salt, mixed into bottom water by use of a few
kilowatt hours of energy, stored in oil-sealed
accumulators, could produce a compact body of
very heavy water which would rush like a
freight train across the terrain dropping a
streak of traceable radioactive eddies as it trav-
eled.
A fixed, water-mixing quern, of the sort
described, might produce a tagged water mass
behaving in a manner appearing realistic to
both the disposal planner and the submarine
geologist; however, its use is not likely to lead
directly to the extremely simple results needed
for the very first experiments. The employment
of a dragged hare might be preferable at the
outset — and its metering machinery might be
somewhat less elaborate than that of the
quern just described.
One might contemplate using 1,000 or more
curies for making streaks several kilometers
long so that location would not be difficult with
a simple gamma device dragged by a ship. In
Figure 3, Ship A is shown dragging such a de-
tector which might be called a "hound" for
obvious reasons. For very great depths, no elec-
trical wire is presently available with the dura-
bility equal to that of an ordinary dredging
cable. It would, therefore, be wise to first con-
sider the use of a compact multichannel chart
recorder inside the dragged pressure shell E so
as to make permanent records of signals picked
up by a set of gamma detectors suspended by an
130
Atomic Radiation and Oceanography and Fisheries
oil-filled float F. Numerous accessories might
profitably ornament this sort of gear, but the
one which might prove most rewarding would
be a sound producer capable of reporting the
moment of contact with the tagged water mass ;
even a crude sonic signal sent from a transducer
on the float, F to the ship, A, via the towed
hydrophone, H, would suffice. Details of the
gamma signals need only be recorded so that
they might be inspected later on the recorder
chart, however, it would be important for the
navigator to recognize instantly when contact
was made so that he could maneuver the ship
economically.
The operations proposed above are not un-
like those used successfully by cable ships when
retrieving submarine wires. Careful preliminary
surveys of the whole area, the selection of iden-
tifying landmarks, and the laying of the mark-
ing buoys also appear essential for success in
work of this type.
The final results might have the general char-
acter of the hypothetical signals shown graphi-
cally at lower right in Figure 3. Change in
amplitude and displacement, and skewness of
the signal records should lead to estimates of
both velocity and rate of mixing. If each survey
included ten or more intersectings, and if each
contact brought separate gamma signals from
several detectors distributed along the hound's
vertical "tail," then the data of the sort needed
would accumulate quickly.
Rough estimate of effectiveness of 1,000 curies
for tagging bottom waters
It appears possible to distribute radioactivity
uniformly along the course of a device dragged
over the sea bottom, and it would appear pos-
sible also to deposit the material so gently that
it would come to rest within a few meters of
the precise course. If, for a rough evaluation,
we assume that local difl^usion sooner or later
produced a uniform distribution within a radius
of 10 meters, and that the total activity, M, was
1,000 curies, then the length of the water mass
which might be tagged can be stated
0)
/=
C7rr2
where C is the average concentration of activity
within the tagged mass.
If now we assume that only 10 seconds can
be allotted for traversing 20 meters (that is the
ship's speed is about 4 knots), then the equa-
tion (9) of Appendix A indicates that a single
detector like the 1955 SIO Geiger instrument
could detect, in the presence of a realistic deep-
water background of 15 cps, a limiting gamma
source concentration of 0.061 disintegrations/
sec/ml, or C = 0.06l/3.7 x lO'^o curies/ml, and
the length of traverse which could be tagged
with 1,000 curies would be, under these as-
sumptions.
/=
1000
1.65x10-12^(1000)2
- = 1900 Km (2)
It would appear feasible to locate and allocate
by ordinary navigational means a geographical
line in the deep sea floor of less than two kil-
ometer's length, so that the hypothetical ex-
ample just given suggests that 1,000 curies
could equally well be used to produce a very
concentrated streak of activity having a length
of two or three kilometers which might still be
detected with ease after it had difl^used, mixed,
or decayed to less than one percent of its initial
concentration. Thus it can be concluded that
1,000 curies, or even less activity, put into bot-
tom water would be quite adequate for tracing
movements on a scale large enough to contrib-
ute information useful in disposal planning.
SUMMARY AND CONCLUSIONS
1. Consideration has been given some of the
problems involved in tagging water masses in
the open ocean.
2. The problems are different in the three
major strata; the surface layers, the thermocline,
and the deep water layer.
3. It appears that under certain circumstances
water tagged with even moderate quantities of
activity can be followed for at least several
weeks; surface waters contaminated by large
activities such as result from fallout can cer-
tainly be followed for a year or more.
4. Much field experience in radiological ocea-
nography has been gained already. A fairly clear
direction for development of instruments has
been indicated.
5. The need is seen for attention to the perfec-
tion of navigational aids, for use of specialized
vessels and gear, and for the use of several ves-
sels simultaneously in oceanic surveys of this
sort.
Chapter 12
Tagged Water Masses for Studying the Oceans
131
APPENDIX A
In practice, many factors tend to limit the
effectiveness of an under sea gamma detector,
but the random fluctuation of a feeble radiation
may alone prevent its recognition in the pres-
ence of a background of similar magnitude. The
lowest detectable concentration, limited only by
statistical considerations, may be expressed in
terms of the strength of the background, the
time permitted for measurement, and the meas-
uring efficiency of the instrument.
Let the sea water be contaminated with a con-
centration of radioactivity N curies/ml, and let
this activity cause m counts/sec to be indicated
by the instrument, and let the average back-
ground be b counts/sec. The relative accuracy,
n, of a single measurement made during t sec-
onds will depend upon signal strength and
background strength; if the fluctuations are
purely random, the error, 95 per cent of the
time will be equal to, or less than.
mt
2V
O-jlf — (Tb
2yjmt-^ht
mt
mt
and solving for the net signal gives,
mt —
2-\-2^\-^nht
A.l
A.2
Now, the counting efficiency of the instru-
ment logically should be derived from the ratio
of counts recorded to the photons striking the
instrument. This ratio would be impossible to
evaluate, but it is approximated when the instru-
ment is small, and easily penetrated by.
;;?/
3.7xlO"Nz//
A.3
that is by the ratio of the net counts recorded to
the photons emitted in a volume of liquid, v,
equal to that displaced by the detector. Solv-
ing this equation for concentration,
mt
N=
iJxlO^'^t^et
A.4
curies/ml, and substituting here the value for
net count, mt, obtained in equation (2) when
the background rate is b, and accuracy is, n, the
limiting concentration can be expressed,
N =
2 + 2\/l + }i-bt
b.lxlQ^^n-vet
A.5
curies/ml, wherein b expresses the background
rate actually indicated when the instrument is
surrounded by clean sea water. If no other back-
ground exists except that coming from a sur-
rounding solution having specific activity B, and
if the instrument counts this activity with the
same efficiency, e, than the limiting detectable
concentration becomes, in curies/ml,
N=
2 + 2\/l+Bn-vet
^.1 XlO^'^n-vet
A.6
Numerical examples applying to an actual un-
dersea instrument
The sensitive portion of the 1955 model of
the Scripps Institution of Oceanography's
Geiger instrument has a volume of about 1,000
ml. The ratio e, applying to hard gamma rays,
was measured directly by submerging the in-
strument in a tank containing potassium solu-
tion of known concentration, and was found to
be approximately 0.03.
If by "detection" is meant the measurement
of the concentration with an error of not more
than 50 per cent, then, n=:0.5.
Formulas (5) and (6) may now be applied
to three characteristic background circum-
stances:
Case 1: Here no other background is evi-
dent except that caused by a solution having
specific activity 6=1.2x10'^ gammas/sec/ml
such as comes from the natural potassium in
normal sea water. From (6), the limiting de-
tectable concentration,
C,:
2 + 2V 1+0.009^
iJt
A.7
gammas/sec/ml, and when t becomes very
large this approaches,
C^^—^ A.8
Case 2: In deep water cosmic rays may be
neglected, and the S. I. O. probe is likely to
indicate a total background of about 15 CPM,
or b = 0.25 counts/sec, therefore, the concentra-
tion just delectable is.
2 + 2Vl-f 0.063/
C2 — . — ■
A.9
gammas/sec/ml, which approaches as t in-
creases to a large value,
0.067
Co= — = A.IO
Case 3: In shallow water where cosmic rays
are unattenuated, the background on the S. I. O.
probe amounts to about 60 CPM, or b=1.0
132
Atomic Radiation and Oceanography and Fisheries
counts/sec, therefore the minimum detectable
concentration becomes.
C,=
2 + 2V1 + O.25/
T^t
A.U
gammas/sec/ml which approaches for very
large values of t,
C =
0.13
A.12
Tabulations
Table 3 compares the effect of increasing the
period of measurement with the effect of di-
minishing the background. It is evident that a
substantial change in background has relatively
small practical effect on any measurement made
so rapidly that only a very poor sample is taken
out of the fluctuating signal; however, when
sufficient time can be alloted for good sampling,
the background level becomes the limiting fac-
tor. It should not be overlooked that in practi-
cal field work, instrument imperfections may
contribute to the overall error more or less pro-
portionally with time of measurement, and that
measurement time must be spent economically
on almost all oceanographic expeditions. It is
apparent therefore that efforts should be made
towards increasing the counting rate, ve, while
reducing the relative value of the background
count by all possible means. Technique for
cleanliness and for discrimination of back-
ground by electronic means have not yet been
fully developed for this purpose.
REFERENCES
FoLSOM, Theodore R. 1956. Problems pecul-
iar to direct radiological measurements at
sea. Paper presented at Nat. Acad, of Sci-
ence Meeting, 29 Feb.-l Mar. 1956. Wash-
ington, D. C. Proceedings (in press) .
Glueckoff. 1955. Long term aspects of fis-
sion product disposal. United Nations Con-
ference on the Peaceful Uses of Atomic
Energy, Geneva. Paper No. 398: 11 pp.
Miyake, Y., Y. Sugiura, and K. Kameda,
1954. On the distribution of radioactivity
in the sea around Bikini Atoll in June
1954. Paper in meteor and geophys., Me-
teorol. Research Institute, Tokyo, 5:253-
262.
Revelle, R. R., T. R. Folsom, E. D. Gold-
berg, and J. D. Isaacs. 1955. Nuclear
science and oceanography. United Nations
International Conference on the Peaceful
Uses of Atomic Energy, Geneva. Paper
No. 277:22 pp.
RuGGOFF, Milton D. (Editor) Why the sea
is salt (an abstract from a translation from
the Norse by Sir George Weble) pp 672-
676 in Harvest of World Folk Tales.
XViii + 734 pages. Viking Press.
U. S. Atomic Energy Commission and Of-
fice OF Naval Research. 1956. Opera-
tion TROLL. Health and Safety Labora-
tory, U.S.A.E.C, New York Operations
Office, NYO-4656, Ed. by J. H. Harley:
37 pp.
U. S. Department of Commerce. 1953.
Maximum permissible amounts of radio-
isotopes in the human body, and maximum
permissible concentrations in air and water.
National Bureau of Standard Handbook
52:445 pp.
Chapter 13
LARGE-SCALE BIOLOGICAL EXPERIMENTS USING
RADIOACTIVE TRACERS^
MiLNER B. SCHAEFER, hiter-American Tropical Tuna Commhsion, Scripps Institution of
Oceanography, La Jolla, California
One of the major difficulties in evaluating
the probable results of the introduction of radio-
active materials into the sea is the lack of ade-
quate knowledge respecting the effects of the
organisms in the sea on the distribution and
transport of such materials. Some information,
which has been reviewed in earlier sections of
this report, has been obtained on the uptake
and excretion of elements by different kinds
of marine organisms. This information is,
however, not sufficiently extensive. The even
more important problems of the quantitative
interrelationships and movements of the popu-
lations of organisms at the several trophic levels
are among the least understood biological phe-
nomena of the oceans. These, together with
physical factors, will determine the fluxes of
the radioactive materials.
Measurements of the fluxes of materials
through physical-biological systems, or ecosys-
tems in the sea are of vast and fundamental
importance not only for evaluating the probable
distribution of radio-active products introduced
into the sea, but also as a basis of evaluating
the sea as a source of food and other biological
products for the use of mankind. With the
approaching full utilization of the land, in-
creasing attention is being directed to the sea
as a source of such products, but the basic bio-
logical knowledge for realistic evaluation of the
potential harvest of the sea is quite inadequate.
The availability of rather large quantities of
radioactive materials, as by-products of the de-
velopment and utilization of nuclear energy,
makes possible the study, in situ, of the biologi-
cal and ecological processes in the sea by the
use of tracer techniques. A start has been made,
in connection with the introduction of radio-
isotopes into the marine and fresh waters by
1 Contribution from the Scripps Institution of
Oceanography, New Series, No. 903a.
weapons tests and by the disposal of low-level
wastes, but the opportunities for obtaining use-
ful information by these means have not been
fully exploited. Also it should be possible by
introducing radioisotopes in a planned, con-
trolled, and purposive fashion to obtain even
better information than is possible through ob-
servation of introductions ancillary to opera-
tions having a different primary purpose.
Observation in connection with weapons tests
Observations in connection with weapons
tests have the advantages that (1) very large
quantities of radioisotopes are introduced into
the sea, sometimes over a rather large area, so
that radioactivity is sufficiently high to be de-
tected in the sea waters and organisms over a
considerable time after the event, and (2) the
difficulty of being certain that the organisms
have actually remained in the water containing
the isotopes is minimized. On the other hand,
the determination of exact amounts of isotopes
introduced, of their spatial distribution, and
of their physical state presents some difficulty.
Biological studies, in connection with the
various weapons tests in the Western Pacific
ocean, have been primarily directed toward de-
termining the concentration of gross activity in
different organisms, the localization of such
activity in different parts of the organism, and
the rates of decline of activity with time. There
has also been limited determination of the
isotopes concerned. The most extensive data
are from the lagoons of the atolls at and near
the test sites. In the open sea, outside the
lagoons, usually only limited collections of or-
ganisms have been made, incidental to other
operations.
Following the test series of 1954, however,
two rather extensive surveys were made of the
distribution of activity in the sea, and in organ-
133
134
Atomic Radiation and Oceanography and Fisheries
isms at different trophic levels, over a large
sea area at intervals of approximately 4 months
and 13 months after the test.
These observations have been directed pri-
marily to possible human hazards through con-
tamination of edible marine products. Only
minor attention has been given to ecological
processes, probably because of lack of facilities
for the extensive, systematic collecting required.
Soon after the underwater test in the Eastern
Pacific in the spring of 1955, some collections
were made that indicate which organisms in the
food chain are the primary concentrators of
certain radioisotopes, and that give some indi-
cation of the time scale in passage to the next
step of the food chain. Unfortunately, it was
not possible to follow the passage of isotopes
farther through the system.
Following a weapons test a series of obser-
vations and collections taken in a carefully
planned pattern in space and time could pro-
vide information on the time scale involved in
the passage of material through the system of
prey and predators, and on the efficiency of this
transfer from one stage to another, two of the
little understood basic problems in marine ecol-
ogy. Data from experiments with radioactive
tracers, together with more limited field data,
indicate that the transfer efficiencies are differ-
ent for different elements.
In those situations, following weapons tests,
where there is a fairly extensive body of water
containing radioisotopes at some particular level,
say at the surface, it should be possible by means
of collections at various depths over a period
of time to obtain worthwhile information on
the vertical migrations of organisms, and also
to determine how the feeding and excretion
patterns of such organisms transport radioiso-
topes from one level to another.
These and similar studies would require the
assignment of a vessel, with necessary equip-
ment and a team of scientists, to the exclusive
pursuit of such studies. Since results will de-
pend on systematic, serial observations, the ves-
sel must be available to take them when and
where required, which precludes the commit-
ment of the vessel to other activities. Although
a sizable cost is involved, it is believed that the
results to be obtained are of sufficient value to
more than justify it.
It should also be pointed out that effective
planning of such studies requires considerable
knowledge of the types of organisms to be en-
countered in the test area, the sizes of their
populations, and some knowledge of their mi-
gration patterns, as well as data on the currents
and other physical parameters to be considered.
A pre-survey of the test areas by standard
methods of biological investigation is, therefore,
an important element in the adequate planning
and execution of post-test investigations by
means of the radioisotopes produced by the
test.
Observations in connection ivith waste disposal
The disposal of wastes from the fission in-
dustry by introduction into the marine en-
vironment offers another means of studying
the uptake of elements by aquatic organisms,
their fluxes in the ecosystem, and their effects
on the organisms concerned. Advantages over
weapons tests are: (1) the wastes are usually
introduced in such a manner that their amount,
distribution and physical state can be readily
determined, (2) disposal is usually continuous,
even though not of constant magnitude, thus
permitting systematic study over considerable
periods of time.
Disposal in the United States has consisted
of relatively low-level wastes introduced into
fresh waters by the Hanford works on the
Columbia River, the Oak Ridge National Lab-
oratory, and the Plant on the Savannah River.
At the first named locality, field observations,
supplemented by laboratory experiments, are
being made on the uptake of radioisotopes by
organisms, their fluxes through the food chain,
and their distribution in the river as the result
of the combined effects of physical and bio-
logical processes. The phosphorous cycle has
been investigated in particular detail. At the
Oak Ridge Laboratory, observations were made
over a period of years on the uptake of fission
products by various organisms, the sites of
deposition of radioisotopes in the organisms
and the effects on some of their populations.
Continuous disposal into marine waters is not
practiced at present in this country. Reports
by H. Seligman, H. J. Dunster, D. R. R. Fair
and A. J. McLean at the 1955 Geneva Con-
ference on Peaceful Uses of Atomic Energy
describe introduction of low-level wastes into
the Irish Sea, and briefly review studies of the
uptake of various isotopes by different kinds of
organisms.
Chapter 13
Large-Scale Biological Experiments with Tracers
135
With the exception of hmited work at Han-
ford and Oak Ridge, it appears in all these cases
that primary attention has been concentrated
on monitoring aspects, that is measurement of
the quantity and distribution of radioisotopes
to insure against hazards to human or other
animal populations. The work of Richard Foster
and others on the radiophosphorus cycle in the
Columbia River, and the work of Louis A.
Krumholz on seasonal variations in quantities
of fission products in different groups of organ-
isms, indicate however, that locations where
wastes are being continuously introduced into
aquatic environments offer a good opportunity
to study the ecological processes of the aquatic
populations through the tracers provided by the
introduced isotopes. It may be expected with
the development of the fission industry in the
next few years, that there will be disposal of
some low-level wastes into marine waters, which
will provide opportunities to investigate the
ecology of estuaries and inshore ocean waters
by these means.
These introductions also constitute large-scale
experiments on both the direct and genetic
effects of long-term exposure of marine organ-
isms to atomic radiations. It is important that
these eflFects be carefully investigated, because
it is possible that the larger organisms in the
sea, which are subjected to much lower rates
of natural radiation than terrestrial forms (due
to the shielding effects of water on cosmic
rays, as well as to the low gamma-ray activity
per unit volume of sea water compared with the
rock and soil of the land), may show propor-
tionally a greater genetic effect from a given
amount of radiation.
Planned experiments
Much useful information may be obtained by
well conceived biological observations in con-
nection with weapons tests and routine disposal
of industrial atomic wastes. Much more pre-
cise information could be obtained, however,
by planned experiments introducing measured
quantities of known isotopes into the marine
environment in a controlled manner. Further-
more, it is evident that the fluxes of different
elements through the ecosystem vary according
to their abundance in the sea and their physio-
logical roles in the organisms. Some of the
most important elements biologically are not
fission products, nor are they present in wastes
in appreciable quantity. The outstanding ex-
ample is carbon. The energy which supports
most of the life in the sea, as on the land, is
fixed as chemical energy of complex carbon
compounds synthesized by plants. To study the
flux of energy through the different trophic
levels of the ecosystem it is necessary, therefore,
to measure directly or indirectly the flux of
carbon. One of the most promising possibili-
ties, discussed further below, is the use of radio-
carbon in tracer experiments on a scale larger
than the present laboratory-type experiments.
The need for large scale experiments under
natural conditions arises because we require
knowledge concerning the quantitative interre-
lationships of the various populations of or-
ganisms, and it is not possible to reproduce
natural marine communities, especially the pe-
lagic elements, in the laboratory. It is probably
not possible yet to study some aspects of open-
sea communities by radioactive tracers, either,
but it may be possible to improve on present
techniques by larger scale in situ experiments
than have been attempted.
Large scale experiments, employing either
mixed fission products or single isotopes iso-
lated from mixed fission products, appear feasi-
ble (at least in selected locations in the open
sea) to determine what organisms take up
which elements and the quantitative aspects of
how these elements are passed through the food
chain. It may also be feasible to introduce
sufficient quantities of radioisotopes in particu-
lar situations to make possible a study of the
transport of such elements by migrations of
organisms. In general, however, in the open
sea, it will be necessary to confine attention to
those elements which are naturally present in
seawater in very small concentrations, so that
the organisms may be expected to take up a
relatively large fraction of the isotope in ques-
tion. In the case of elements such as carbon,
only a small fraction of which is taken up by
the organisms, experiments in unconfined vol-
umes of open sea would appear to require
larger quantities of the radioisotope than are
feasible on a cost basis, and experiments there-
fore will have to be limited, in the near future
at least, to small enclosed arms of the sea or
artificially bounded volumes of water in the
open sea.
In order to conduct experiments in the open
sea it is necessary to (1) introduce the radioiso-
topes into an area sufiiciently large so that it
can be located and followed, to insure the or-
136
Atomic Radiation and Oceanography and Fisheries
ganisms under study being in it over a known
period of time, and (2) have a sufficiently high
radioactivity that it may be followed from ship-
board. If we use only fission products which
organisms concentrate; then, since longer count-
ing periods are feasible for samples of the
organisms than are feasible for the equipment
used to locate and follow the water mass, the
radioactivity required to determine the position
of the contaminated water mass is expected to
be the limiting factor in the experiment.
Revelle, Folsom, Goldberg and Isaacs (1955)
have indicated that, in the slow-mixing levels
of the sea below the thermocline, vertical mix-
ing is almost negligible, so it may be expected
that while the area in which the isotopes can
be detected spreads over a radius of 4.1 km.,
vertically it will be limited to about 1 meter.
In these circumstances, it has been calculated
that 10 curies of gamma emitter may be detected
until it has spread laterally to a radius of 4 km.,
or a mean concentration of about 2x10"^ curies
per cubic meter. They do not specify the time
involved, but it may be presumed to be of the
order of one week to one month. For biological
experiments, it would be necessary to make
observations over a longer period of time, also
we cannot commence significant biological ob-
servations until the contaminated area is suffi-
ciently large to ensure knowledge of which
animals are or have been in the active water.
For these reasons the time involved should
perhaps be increased by a factor of 10. If the
diffusion of the contaminated water, both ver-
tically and horizontally follows the "random
walk" law, the volume containing the activity
will increase linearly with time, and, in conse-
quence, about 100 curies of gamma activity will
be required.
Experiments in the upper mixed layer will
require much larger quantities of fission prod-
ucts. Mixing to the top of the thermocline is
very rapid; according to the authors above
cited the lower boundary of radioactive water
moves down at about 10'^ cm/second. If we
select an area, such as that off Central America
where there is a fairly shallow sharp thermo-
cline at a mean depth of about 20 meters, mix-
ing down to the top of the thermocline would
be complete in less than ten hours. Thereafter
downward mixing should be negligible. Recent
experiments suggest that the radius over which
the water spreads laterally is increased as about
the 0.8 power of time. In Bikini lagoon it has
been found that the radius of the radioactive
area increased to 4 kilometers in 3 days. If
we ran an experiment for 90 days, which is
probably the time necessary to follow the flux
of radioelements through two or more trophic
levels, we would, then, expect the radius to
approximate
r= 4 (30) -8=: 60 kilometers.
The volume would then be (with a 20 meter
thermocline)
77X36x10^x20 cubic meters
or about 225 X 10^ cubic meters
To be still detectible at this dilution, using the
above estimate of 2 x 10""^ curies/cubic meter,
an initial quantity of some 4x10* curies would
be required. The logistics of handling large
quantities of fission products will be difficult,
but not perhaps impossible.
Because of the smaller volume of water to
be dealt with, it may be most desirable, at least
initially, to conduct such experiments in a small
enclosed arm of the sea. Such an environment
is diflferent in many respects from the open
ocean, but much useful information about fluxes
of radioelements through the several trophic
levels could be obtained. It would not be diffi-
cult to select a small bay, with a narrow, shal-
low entrance, which could be cut off temporarily
from the sea for this purpose. A body of, say,
one square kilometer with an average depth of
ten meters might be used, giving a volume of
lO'' cubic meters. Since the problem of locating
the water mass is eliminated, and fairly large
volumes of water can be filtered for organisms,
rather small quantities of fission products, which
would not be hazardous, could be employed.
One curie would be ample, and the contamina-
tion of the water itself would be within safe
levels for human hazards.
It was noted earlier that one of the important
fundamental ecological problems is to measure
the flux of carbon through different trophic
levels. Since the fraction of the carbon taken
up by plants is a very small part of the total in
the sea water, experiments with radio-carbon in
the open sea are not feasible. Experiments
using samples in bottles have been conducted
in situ in recent years, but these have two de-
ficiencies: (1) the surface and other effects of
the container modify the environment so that
the resulting computations for photosynthesis
probably are not those that would have occurred
Chapter 13
Large-Scale Biological Experiments with Tracers
137
naturally in the sea and (2) only the uptake
of carbon at the phytoplankton level is meas-
ured. It seems feasible to improve on the ex-
periments in bottles by conducting experiments
in small lagoons, or by employing larger partly-
enclosed volumes in the open sea.
From experience with such experiments in
bottles, it can be shown that there is sufficient
uptake of carbon by the phytoplankton, if
grown in a concentration of 0.3 micro-curie per
liter for one day, to measure it if a one liter
sample is filtered and the radioactivity of the
filtered plants determined in a counter of 20
per cent efficiency. By increasing either the
counting time or the volume of water filtered,
the initial concentration of C^* can be decreased
correspondingly.
For an experiment in a lagoon, we might
use a body of water of, say, 500 meters long
by 200 meters wide with an average depth of
10 meters, giving a volume of 1x10^ cubic
meters or 1 x 10^ liters. By filtering 100 liters
of water for phytoplankton, C^* at a concen-
tration in the water of 3x10"^ curies per liter
would suffice, or 3 curies for the experiment.
Since there is probably between a 50 per cent
and 90 per cent loss at each step up the food
chain, correspondingly larger volumes would
have to be strained for the higher forms, but
this is a simple problem by the use of standard
nets, etc.
To get improved measurements of the uptake
of carbon by phytoplankton in the open sea,
and the passage of carbon to the smaller grazing
organisms, it is suggested that a moderately
large rubber tank open at the surface be em-
ployed to isolate a piece of the top of the sea,
yet have a sufficiently small surface-to-volume
ratio that the processes will more nearly ap-
proach normal conditions than is obtained in
bottle experiments. We might employ such an
apparatus of 20 meters diameter by 10 meters
deep, having a volume of tt 10^ cubic meters,
or ttXIO^ liters. By filtering 10 liter samples
for phytoplankton, with 20 per cent efficient
counting equipment, we would need to provide
about 3x10"^ curies per liter, or a total of
about 1/10 curie of O*.
So?77e cost and logistic considerations
For the two experiments with C^*, discussed
immediately above, the problems of handling
the amounts of activity involved present no
particular difficulty. Since C^* is a pure beta
emitter, the shielding problem for even the
experiment requiring 3 curies is a simple matter.
The cost of the isotope, however is fairly high;
at present about $30,000 per curie. This might
be reduced somewhat if the present demand
were to increase. The cost, notwithstanding,
however, the information to be gained is well
worth the outlay.
In the case of an experiment using gamma
emitters in the slow-mixing layer below the
thermocline, where about 100 curies would be
required, it is suggested that mixed fission
products from wastes from processing of reactor
fuel elements be used. A large quantity of such
wastes will be available, probably at no charge.
If one used HNO3 salted waste product from
a natural uranium-plutonium reactor, after 100
days "cooling," the reactor waste will contain
about 200 curies/gallon. Approximately half
a gallon will be needed, requiring about 10"
of lead shielding for transportation and han-
dling. A cubical container will require 10.05
cubic feet of lead, weighing 7,175 pounds.
This is feasible to handle by freight and on
shipboard.
For the kilocurie quantities required for an
experiment in the upper mixed layer of the
sea, the handling problem reaches a different
order of magnitude. It becomes quite infeasible
to handle waste liquids in the volume required.
It may be possible, because of the much higher
activity per unit volume to employ slugs of
U^^^ from a reactor, which, after 30 per cent
burning and 100 days "cooling" have about
2x10^ curies per kilo of fairly long term
gamma activity. Even then some 2/10 kilos
of "used" U^^^ would be required. The prob-
lems of transporting and handling this are
somewhat difficult as are methods of dissolving
and liberating the material at sea, but probably
feasible. Further detailed consideration needs
to be given to this problem. It may, of course,
be that the use of an explosive reaction — a
small nuclear detonation for oceanographic and
biological experimental purposes — is the only
logistically feasible method.
REFERENCES
Revelle, R., T. R. Folsom, E. D. Goldberg,
and J. D. Isaacs. 1955. Nuclear Science
and Oceanography. United Nations Inter-
national Conf. on Peaceful Uses of Atomic
Energy, Geneva, Paper no. 277:22 pp.
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