Treatments for farmland contaminated with radioactive material

M.ll.'.^i6 ^

TREATMENTS FOR FARMLAND

CONTAMINATED WITH

RADIOACTIVE MATERIAL

Agriculture Handbook No. 395

AUG; 5 71

Depositoy Oocutntol

Agricultural Research Service
UNITED STATES DEPARTMENT OF AGRICULTURE

Supported in part by the
UNITED STATES ATOMIC ENERGY COMMISSION

CONTENTS

Page

Review of research 2

Removal of crops and crop residues 2

Removal of surface soil 3

Decontamination in cold weather 3

No-tillage management 4

Deep placement of contaminated soil 4

Irrigation and leaching 5

Applications of lime, fertilizers, and other soil amendments 6

Feasibility of treatments for contaminated areas 6

Exposure of workers 8

Removal of crops and mulches 10

Removal of surface soil 11

Decontamination in cold weather 12

No-tillage management 12

Deep placement of contaminated soil 12

Irrigation and leaching 13

Applications of lime, fertilizers, and other soil amendments 13

Alternatives to treating contaminated soil 14

Conclusions 14

Literature cited 15

Washington, D.C. Issued June 1971

For sale by the Superintendent of Documents, U.S. Government Printing Office
Washington, D.C. 20402 — Price 20 cents

TREATMENTS FOR FARMLAND CONTAMINATED
WITH RADIOACTIVE MATERIAL

By R. G. Menzel and P. E. James '

This handbook presents information on the ef-
fectiveness and feasibility of various treatments
for farmland that has been contaminated with
radioactive material. Two kinds of treatments
are evaluated. The first kind, which may be called
decontamination, includes methods of removing
radioactive material from farmland. Tlie second
kind includes methods of treating land to reduce
the uptake of radioactive materials by crops with-
out decontaminating. Alternatives to treating
contaminated land are discussed to give a broader
perspective on the techniques of managing con-
taminated land.

There are many possible sources of radioactive
material that could contaminate farmland, rang-
ing from widespread fallout from the explosion
of nuclear weapons to a very limited spread from
a transportation accident involving radioactive
material. The explosion of nuclear weapons could
result in contamination of thousands of square
miles. Contamination from a very severe reactor
accident might aft'ect several hundred square
miles. In transportation accidents the contami-
nated area would probably be less than one acre.

A decision to treat the contaminated area will
require consideration of several complex factors,
including (a) the immediate and long-term haz-
ard presented bj' the location and nature of the
radioactive material, (b) the hazard likely to re-
luain after treatment, (c) other consequences of
the treatment, such as radiation exposures to the
persons carrying out the treatment and changes
in productivity of the treated land, and (d) the
availability of machinerj- and nnvnpower for
treatment. It may be unnecessary to treat contami-

' Respectively, .soil .scientist, Soil and Water Conserva-
tion Research Division, and agricultural engineer, Agri-
cultural Engineering Research Division, Agricultural Re-
.search Service, Beltsville, Md., 20705. This study was
supported in part by the U.S. Atomic Energy Commission.

nated land if the radioactive material is short-
lived and the area can be isolated until it decays.
If the area of contamination is large, the quan-
tity of readily available resources might he lack-
ing for desirable treatment of all areas at once.
In that case, careful judgment will be required
to recommend which areas sliould be treated first
and what methods should be used.

Since the choice of treatment may depend on
the objectives of treating any given area of con-
tamination, it is necessary to define the objectives
clearly. These could be one or more of the fol-
lowing: (a) Preventing spread of the radioactive
material to other areas; (b) reducing the radi-
ation hazard to persons who must live or work
in the area; and (c) reducing the entry of the
radioactive material into food products derived
from the contaminated land. Some treatments are
better suited to one objective than to another.

The urgency of treatment would likewise de-
pend on the objectives. Immediate action might
l)e essential for preventing spread of radioactiv-
ity or reducing the radiation hazard, but not
for reducing the radioactivity in crops. Immedi-
ate action might increase greatly the radiation
exposures to the persons carrying out the treat-
ment. In each case of contamination, the hazards
of immediate treatment should be balanced
against those of delaying or forgoing treatment.

In many cases, the main objective of treating
contaminated farmland would be to reduce the
entry of radioactive material into food products.
This would be true if relatively long-lived and
biologically active radionuclides, such as cal-
cium-45, zinc-65, strontium-89, or strontium-90,
were present in appreciable quantities. In fall-
out from nuclear explosions the strontium radio-
nuclides are very important (7).^ Since they

' Italic numbers in parentheses refer to Literature
Cited, p. 15.

AGRICULTURAL HANDBOOK 395, tJ.S. DEPT. OF AGRICULTURE

often constitute tlie main hazard, we evaluated
the effectiveness of some treatments by the re-
duction in uptake of radiostrontium.

This bulletin describes the effectiveness and
feasibility of many possible treatments of con-

taminated land under various soil and crop con-
ditions. This information should allow one to
choose a suitable treatment after the objectives
have been decided upon. This decision must take
into account the particular circmnstances of each
instance of contamination.

REVIEW OF RESEARCH

There is widely scattered literature concerning
the treatment of radioactive contamination on
land. Some of the publications are not generally
available, and many of the pertinent results have
not been considered in relation to agricultural
areas. In this review, we have attempted to or-
ganize information about a wide variety of pro-
posed treatments for contaminated agricultural
land. References are either to original work or to
critical reviews. The literature citations are se-
lected to give pertinent results for various treat-
ments.

The general problem of managing contaminated
agricultui-al land has been discussed briefly in
a previous publication (-5i). Experimental results
tliat were available in 1963 concerning the re-
moval of crops, crop residues, and surface soil,
tlie deep placement of contaminated soil, and the
application of fertilizei-s and soil amendments
were reviewed. A Russian review of the problem
has been translated and is available from the U.S.
Department of Commerce (1). It discusses re-
sults with deep plowing, leaching, and the ap-
plication of lime and fertilizer.

Many tests on the decontamination of land
areas that have been conducted by the U.S. De-
partment of Defense are relevant to agricultural
decontamination. A performance summary of
these tests has been published (^9), and the ap-
plication of the results in areas contaminated by
fallout lias been considered (25). These tests are
particularly valuable for including techniques
of snow removal and the decontamination of
frozen and thawing soil that have not been stud-
ied elsewhere.

Removal of Crops and Crop Residues

A number of tests on the remo\-al of contam-
inated crops and crop residues have been made
by the Agricultural Research Service at Belts-

ville, Md. (18, 21, 22). Radioactive material was
applied as a spray or as simulated dry fallout.
Measurements were made of the amount of radio-
active material removed as various crops or crop
residues were removed from the land. The tests
included removal of standing crops at various
stages of maturity, removal of sod, and removal
of grass or straw mulch.

Removal of standing crops from a contami-
nated area removed only part of the radioactive
material, because much of it fell through the
vegetative cover to the ground. From one-fourth
to one-half of the radioactive material was us-
ually carried on green crops removed by con-
ventional types of forage-harvesting machinery
(21, 22). These included a flail-type forage chop-
per, a direct-cut forage harvester, and a mower,
followed by a side-delivery rake and windrow
pick-up baler. Crops removed by the forage chop-
per and harvester carried somewhat more con-
tamination than those removed by mowing, rak-
ing, and baling. Crops providing more complete
ground cover usually carried more of the radio-
active material when they were removed. ^\Tien
rain fell or sprinkler irrigation was used after
contamination and before crop removal, the
amounts of contamination removed with the crops
were appreciably lower.

Harvester-thresher combines were used for har-
vesting and threshing mature rye and soybeans.
About one-tenth of the contamination was re-
moved with the straw. The harvested grains con-
tained less than 1 percent of the contamination
in rye and less than 0.1 percent in soybeans (18).
In these experiments, the radioactive material
was carried on tiny glass spheres (20^0 fi in
diam.) in order to simulate fallout occurring
under dry conditions.

Cutting and removing sod removed more than
90 percent of radioactive contamination pre^d-
ously sprayed on the surface. The high effective-

TREATMENTS FOR FARMLAND CONTAMINATED WITH RADIOACTIVE MATERIAL

ness resulted from the fact that tlie root mat
and some soil was remo\-ed with tlie sod. A road
grader was also effective in removing contami-
nated sod. Similar tests with sod-cutting ma-
chines have been conducted by the U.S. Depart-
ment of Defense, witli equally effective results
(3.9).

The effectiveness of decontamination by remov-
ing mulches differed greatly according to the
type of mulch and method of contaminating it.
"Wheat-straw and bermudagrass mulches were
spread evenly on the ground surface at rates
of 2 to 5 tons per acre. Then they were contami-
nated and afterward removed from the plots
with a side-delivery rake. When radioactive solu-
tion was sprayed onto wheat-straw mulch, more
than 90 percent of the contamination was re-
moved with the mulch {31). With di-y simu-
lated fallout applied on bermudagrass mulch,
about 30 percent of the contamination was re-
moved with a mulch of 2 tons per acre and
60 percent with a mulch of 5 tons per acre. The
poorer decontamination with dry fallout was at-
tributed partly to inefficient raking of the fine,
short grass and partly to sifting of dry fallout
through the mulch.

Removal of Surface Soil

Many common types of earth-moving equip-
ment have been used in decontamination tests.
These include graders, bulldozers, and rotary,
elevating, and pan-type scrapers. In tests re-
ported by the Agricultural Research Service (18.
21, 22), from 80 to 90 percent of radioactive
surface contamination was usually removed when
2 inches of soil was removed. Although these
tests were conducted at different times, there ap-
l^eared to be little diffei-ence in the effectiveness
of different kinds of scraping equipment.

Roughness of the soil surface apparently had
some influence on the depth of cut necessary to
achieve this degree of decontamination. However,
the use of rollers to smooth the surface after
contamination and before scraping did not in-
crease the effectiveness of decontamination. The
lack of significant results in this regard may
have been due to difficulties in controlling the
depth of cut, which varied with moisture con-
tent and looseness of the surface soil. The depth

of cut was more easily controlled witli the rotary
and elevating scrapers and graders than with
bulldozers and large pan-type scrapers.

Similar tests have been reported l\v the IT.S.
Department of Defense (29). Tilled, hard, or
turf-covered soils in moist or dry condition were
scraped with a pan-type scraper or with a grader
followed by the scraper to pick up windrows
left by the grader. The first grader cut, 2 inches
deep, removed about 90 percent of the surface
contamination from tilled soil, and after a sec-
ond cut more than 99 percent of the initial con-
tamination had been removed. Decontamination
was even more effective with hard or turf-covered
soil, or when the scraping was done with the pan-
type scraper making a cut from 2 to 4 inches
deep.

Street sweepers using vacuum or rotary brooms
have been studied for removal of fallout con-
tamination from soil surfaces. A small vacuum
street sweeper was used to remove contamination
from a clipped meadow of Kentucky .SI fescue
and Ladino clover (18). About half of the con-
tamination could be removed by sweeping the
meadow twice, but little decontamination could
be effected by further sweeping. In later experi-
ments at Beltsville, a rotating broom sweeper
with steel bristles removed about 75 percent of
the contamination from a moist soil with a thin
cover of fescue. A second sweeping gave almost
90 percent remo^'al of contamination. A sweeper
with plastic bristles was less effective, apparently
because the plastic bristles did not cut as well
through vegetation.

Some attempts have been made to bind con-
tamination in a coating of asphalt allowed to
harden on the contaminated surface. By peeling
off the asphalt coating, Schulz and others (3-3) re-
moved 97 percent of a radioactive tracer that
had been sprinkled on the surface of small plots.
Wlien used on a field scale (21) the asphalt emul-
sion did not improve decontamination because
mechanical scraping methods broke up the as-
phalt coating instead of peeling it from the
surface.

Decontamination in Cold Weather

The U.S. Army Nuclear Defense Laboratoiy
has tested methods for decontaminating various
surfaces under cold weather conditions (23).

AGRICULTURAL HANDBOOK 395, U.S. DEPT. OF AGRICULTURE

Treatments for frozen or thnwinp; around and
tliat covered with snow or ice are of possible
agricultural interest.

Mechanical snow removal was quite effective
in removing radioactivity from areas where a
fallout simulant had been spread on top of loose
snow. Under good operating conditions, a blade
snow plow or motor grader left less than 5 per-
cent of tlie radioactivity, and a carryall scraper,
bulldozer, or rotarj' snowblower left less than
15 percent. More effoi't was required to reach the
same level of decontamination with warm, sticky
loose snow than with cold snow using either a
road grader or rotary snow blower.

Ice or frozen gi'ound surface was effectively
decontaminated by sweeping. Hand sweeping left
less than 5 percent of the radioactivity on ice.
Mechanical sweeping left less than 15 pei'cent on
a frozen ground surface. It made little difference
whether the temperature was just below freezing
or subzero.

Thawing ground was scraped with a carryall
scraper, bulldozer, or motor grader, which left
less than 10 percent of the radioactivity after
one or two passes of the equipment. With addi-
tional passes it was possible to leave less than
one percent of the radioactivity on the ground.
About the same effort was required to scrape
either a thawing soil or a warm soil.

No-tilla{3;e Management

When radionuclides are left on the soil sur-
face In' not cultivating during the planting and
growth of crops, uptake by many crops is less
than would be obtained with normal cultivation.
For example, irrigated barley grown on a silt
loam soil in central Washington (4) took up
half as much radiostrontium when it was left
on the surface as when it was thoroughly mixed
through 4 inches of soil by cultivation (4). Simi-
lar trends were shown for wheat, barley, po-
tatoes, and sugar beets grown in field experiments
on several widely varying soil types in England
(24) . However, shallow-rooted crops such as rye-
grass and kale took up twice as much radio-
strontium when it was left on the surface as
when it was plowed 4 inches deep.

The relative uptake of radiostrontium from
no tillage, compared with normal cultivation, has

varied widely in our trials at the Agricultural
Research Center (unpublislied data). In the no-
tillage treatment, a fescue meadow was killed
with herbicide, and the crops were seeded 21/^
or 5 inches deep with a sod planter. On two soil
types and with three crops grown in 1968, the
relative uptakes were roughly as follows (nor-
mal cultivation = 1.0) :

Soil type
Elkton silt loam
Sassafras sandy loam 2

Wheat Corn Bush Beans
1.5 ='1.5(1) 3

0.2

'0.6(0.3)

Although poor weed control was obtained and
crop growth was generally unsatisfactory, it ap-
pears that no-tillage management reduced radio-
strontium uptake only on the sandy loam with
corn and beans. These crops tend to be deeper
rooted than wheat. The sandy loam is better
aerated and thus encourages deeper rooting than
the silt loam. This factor and the minimum dis-
turbance of the soil surface during planting are
probably most important for reducing the up-
take of radionuclides from the soil surface.

Deep Placement of Contaminated Soil

Field plot experiments have usually shown re-
ductions in the uptake of radiostrontium when
it was placed deeper in the soil than it would
be with normal cultivation. Deep placement has
been accomplished in several experiments by ex-
cavating and refilling field plots. Placement of
strontium-89 in a layer 15 inches deep in a silt
loam soil at Beltsville, Md. did not reduce uptake
by soybeans compared with rotary tillage into
the top 6 inches of soil {17).

In other experiments, placement treatments
were combined factorially with lime, irrigation,
and potassium fertilizer treatments to test for
effects on root distribution that might increase
the benefit from deep placement. No such effects
were found. With various soil types and climatic
conditions in several states, the lowest strontium-
90 content of corn, soybean, oats, or wheat grain
with deep placement was about 40 percent of that
with normal plowing {8). The reduction in up-

' Rflative uptake values in parentheses are from plant-
ing 5 inches deep. Otherwise, uptake was the same from
both depths of planting.

TREATMEUSTTS FOR FARMLAND CONTAMINATED WITH RADIOACTIVE MATERIAL

take from deep placement of strontium-9() varied
considerably with different crops and locations.

In similar experiments carried out in Russia,
the uptake of mixed fission products was com-
pared from placements 30 and fiO or 7() cm. (12
and 24 or 28 in.) beneath the surface of a soddy
leached soil (10. pp. 20^-208). This type of soil
encourages shallow rooting of plants. Several
crops were grown in 3 or 4 successive years on
the same plots. The results with each crop varied
greatly fi-om year to year. In general, the up-
takes from the deeper placements were about
one-tenth of those from the shallow placement.
The reduction from deep placement was least
with oats and barley, intermediate with peas, and
greatest with vetch.

Field tests with varying depths of plowing to
reduce radiostrontium uptake have been reported
from England (24) and Russia {13). Deep plow-
ing to 50 cm. (20 in.) on a leached chernozem
soil in Russia reduced average uptake of stron-
tinni-90 by oats to 60 percent of the U])take after
disking 10 cm. (3.9 in.) deep. The uptake by
individual plants was highly vai-iable, perhaps
because plowing tended to band the surface-
applied sti-ontium-90. In England, studies on
widely varying soil types showed that, in gen-
eral, the deepest plowing (12 inches) resulted
in least uptake for shallow-rooted crops such as
ryegrass and a grass-clover pasture. However,
plowing depths to 12 inches had little effect on
the strontium-89 uptake by deep-rooted crops.

Various herbicides and inorganic chemicals
were used in greenhouse and field experiments
to limit uptake from a buried soil layer contain-
ing strontium-85 (19). Wlien sodium carbonate
was placed with the contaminated layer at the
rate of 10 tons per acre, the uptake of stron-
tium-85 was less than one-tenth of that without
sodium carbonate, but crop yields were only
slightly reduced. Seven other inorganic chemicals
and seven herbicides did not reduce strontium-85
uptake as effectively and tended to give greater
yield reductions. But this limited experience
does not establish that sodium carbonate is the
best material to use as a root inhibitor. A long-
lasting, immobile material that will stop root
growth into the contaminated soil volume with-
out reducing crop yields is needed.

In a subsequent experiment on an irrigated

silty clay loam in Texas, sodium carbonate at
the same rate of application was plowed to a
depth of 3 feet with contaminated surface soil
(20). A 36-inch moldboai'd plow with an at-
tached grader blade was used to push a 2-inch
layer of topsoil into the furrow behind the mold-
boai'd. Nearly all (95 percent) of the contami-
nated surface soil was placed deeper than 24
inches beneath the plowed surface. The uptake
of strontium-85 by Sudan grass, sugarbeets, soy-
beans, and cabbage was from one-fourth to one-
half as much as with rotary tillage to a 6-incli
depth. '\^nien sodium carbonate was applied with
deep plowing, the uptake of strontium-85 was
only one-fifth as much as without sodium car-
bonate. On this rather tight, deep, fertile soil,
crop yields were increased markedly by deep
plowing. They were not measurably affected by
the application of sodium carbonate.

Heating contaminated soil to immobilize stron-
tium-90 has been tried in conjunction with deep
placement (2). Uptake of strontimn-90 with four
soil types that had been heated to 800° C. ranged
from one-eighth to one-half as much as with no
heating. In all cases, the contaminated soil was
placed 25 cm. (10 in.) deep for measuring plant
uptake. Extractability investigations suggested
that less uptake would be obtained if the soil
were heated to 1,000° C. or higher.

Irrigation and Leaching

Controlled applications of water to contami-
nated land might be used to leach radionuclides
out of the rooting zone of crops or to modify the
rooting depth of the crops. Until now, the re-
ported attempts to use irrigation have had little
success toward either objective.

Leaching of radioactive strontium through soils
with water of dilute solutions is very slow. When
columns of various soils were leached with 30
inches of water, the maximum penetration of
strontium-89 was 4.3 inches (26) . In the same ex-
periment, leaching with 0.005 A^ CaCU increased
the penetration, but the average sti-ontium-89
movement in one soil was only 3 inches after
application of 16.4 inches of solution. With the
other soils, more solution (up to 250 inches)
was required to give the same average strontium-
89 movement. Leaching with dilute solutions of

6

AGRICULTURAL HANDBOOK 395, U.S. DEPT. OF AGRICULTURE

complexing agents, such as ethylenediaminetetra-
acetic acid, has also shown little advantage for
removing radioactive strontium (27).

Acids and salts also have been applied to con-
taminated soil surfaces in order to increase the
movement of strontiimi-00 during leaching (33).
Hydrochloric acid and ferric chloride, at rates
of 15 and 22 tons per acre, respectively, were
most effective. When these treatments were fol-
lowed by leaching with 5 feet of irrigation water,
about 20 percent of the stroiitium-90 remained in
the top foot of a fine sandy loam, and about 60
percent in the top foot of a loam. In addition
to being expensive and rather ineffective, the
latter two treatments would leave an infertile
soil.

A series of field experiments have been re-
ported (8) in which irrigation was used in an
attempt to modify the uptake of strontium-90
from deep or shallow placement in the soil. No
modifying effect of irrigation could be detected.

Applications of Lime, Fertilizers,
and Other Soil Amendments

Soil amendments have been used to reduce
the uptake of radionuclides in difl'erent ways.
Calcium- and potassium-bearing materials pro-
vide cations that compete, respectively, with
strontium and cesium and thus reduce their en-
try into plants. Soluble phosphates added in
large amounts precipitate strontium so that less
of it may enter plants. Additions of materials
with a high cation exchange capacity, such as
peat, compost, or clay minerals, may also reduce
the amounts of radionuclides taken up by plants.

Many experiments have shown that applica-
tions of lime or gypsum to acid soils reduce
the uptake of radioactive strontium by plants
grown on these soils {J, 4, 10, U, 17, 24). The
reduction depends upon increasing the available
calcium supply of the soil, so that little effect

is seen on soils already well supjilied witli cal-
cium. Even on very acid soils, application of
lime or gypsum does not usually reduce uptake
of radiostrontium to less than one-third of the
uptake from the untreated soil.

Potassium fertilizers reduce the uptake of ra-
dioactive cesiiuii from soils (/, J7). Tliis is simi-
lar to the effect of lime on uptake of radioactive
strontium. Potassium also reduces the uptake
of radioactive strontium, but to a much smaller
degree than applications of lime or gypsum {1.
6, 8).

Nitrogen fertilizers tend slightly to increase
the uptake of radioactive strontium and cesium
from soils (1).

Phosphate fertilizers added to soils at the
usual agronomic rates have shown little effect
on uptake of radionuclides {10. pp. 197-200).
However, large additions of soluble phosphates
have resulted in very striking reduction in the
uptake of radioactive strontium [10). Wlien di-
ammonium or tripotassium phosphates were
added in amounts equivalent to the cation ex-
change capacity of the soil (4 to 12 metric tons
per hectare, or 2.2 to 6.5 avdp. tons per acre),
the uptake of radioactive strontium was reduced
to one-tenth of that without these materials.
Tlie treatment was more effective in soils with a
higher pH value. At the higher rates of appli-
cation, some difficulty with plant growth was
noted.

Materials with a high cation exchange capac-
ity have reduced uptake of radioactive stron-
tium when they were added to soils. Decom-
posing organic materials or compost liave re-
duced uptake as much as a factor of five when
mixed with mineral soils in amounts greater than
2 parts per 100 of soil {10. pp. 170-180; 17).
Clay minerals such as kaolinite and montmorillo-
nite have also reduced uptake of radioactive
strontium when added to a sand culture {11) or
soils {28).

FEASIBILITY OF TREATMENTS FOR CONTAMINATED AREAS

Treatments for land areas that are contami-
nated with radioactive materials will not be fea-
sible unless the following i-equirements are met.
First, the treatment must make a significant re-
duction in the radiation hazard, either by remov-

ing the radioactive material or by reducing its
uptake into crops. Second, it must leave the land
in a productive state for agricultural use. Third,
equipment and materials for the treatment must
be available. Finally, the treatment should meet

TREATMEINTS FOR FARMLAND CONTAMINATED WITH RADIOACTIVE MATERIAL

tlie other requirements with no more than a rea-
sonable eti'ort. Treatments that are feasible in
one situation may not be in another.

In some cases it may be impractical, or even
impossible, to treat contaminated land because
of the condition of the land. An obvious limi-
tation would exist if the radiation level were
high enough to endanger workers in the field.
The existence of heavy vegetative or snow cover,
or of a frozen surface soil, would preclude the
use of most kinds of scraping equipment. Soil
characteristics such as surface roughness, shal-
lowness of fertile soil, or the presence of stones
might greatly increase the effort needed to reach
the desired effectiveness, or even prevent some
treatments.

In order to compare the feasibility of various
treatments, their important characteristics are
given in tables 1, 2, 3, and 4. These character-

istics include the effectiveness of the treatment,
the effort required for treatment and for disposal
of contaminated material, and the productivity of
treated land. Because soil and crop conditions
vary so widely, we attempt only the qualitative
evaluation of these characteristics. For example,
the effectiveness of a treatment is judged good
if test results generally showed more than 95
percent of surface contamination was removed,
poor if less than 75 percent was removed, and
fair if the amount removed was intermediate.
Few data are available for estimating effort re-
quired for treatment or disposal, or predicting
the productivity of treated land. Evaluations of
these characteristics are based on existing data,
supplemented by qualitative observations of test
procedures and general agricultural experience.
We found that machinery must be operated
with care to obtain clean i-emoval of contami-

Table 1. — A comparison of methods for removing contaminated crops or mulches from lamd

Effort required-

Type of
vegetation

Implement

Removal of
radioactivity '

For
removal '

For
disposal ''

Soybeans, 12" high Mower Poor Poor Fair.

Soybeans, 12" high Flail harvester Poor Fair Good.

Soybeans, full growth Flail harvester Poor Poor to fair Good.

Soybeans, full growth Forage harvester Poor Poor to fair Good.

Soybeans, mature Combine, straw removed Poor Poor Fair.

Fescue-clover meadow- Forage harvester Poor Poor to fair Good.

Sudan grass, 12" high Mower Poor Poor Fair.

Sudan gras.s, 12" high Flail harvester Poor Fair Good.

Rye, full growth Mow, rake and bale Poor Poor Good.

Rye, full growth Forage harvester Poor Poor to fair Good.

Rye, mature Combine, straw removed Poor Poor Fair.

Wheat, mature Combine, straw removed Poor Poor Fair.

Corn, full growth I'V)rage harvester Poor Poor Fair.

Mulch, 5 tons wheat straw/acre Side-delivery rake Good Poor Fair.

Mulch, .5 tons bermudagrass hay/acre Rake and bale Poor Poor Good.

" Rating of removal of radioactivity : Good — •>95 percent removal.

Fair — 75 to 95 percent removal.
Poor — <75 percent removal.
° Rating of removal effort : Good — >5 acres per hour.

Fair — 1 to 5 acres per hour.
Poor — <! acre per hour.
'Rating of disposal effort: Good — additional loading and hauling effort minimal.

Fair — considerable effort in loading and hauling.
Poor — very great loading and hauling effort.

8

AGRICULTURAL HANDBOOK 395. U.S. DEPT. OF AGRICULTURE

nated soil or vegetation. This means that more
effort may be required tlian in normal operations
with the same types of machinery.

Exposure of Workers

It is doubtful whether the treatment of agri-
cultural land would be so urgent as to justify
exposing workers to possibly disabling amounts
of radiation. Disabling illnesses are not likely
to occur if radiation doses to humans are lim-
ited to less than 100 rems (9, p. 591). Different

ways may be used to limit radiation doses, de-
pending on whether intense local contamination
or widespread fallout are present.

In cases of localized contamination, it should
be possible to limit exposures by evacuating resi-
dents and using teams of workers to remove the
contamination. Each team might work only a
short time in areas of high radiation intensity.
Specially shielded or radio-controlled equip-
ment could be brought to the contaminated area
to reduce further the exposure of workers. Con-
centrated effort would be needed to remove con-

Table 2. — A comparison of methods for removing soil surface contamination in waitn weather

Condition of
surface

Implement

Removal of
radioactivit.v '

Effort required —

For For

removal " disposal '

Effect on

soil

productivity '

Bluegrass sod Sod cutter 12" wide Good to fair Poor Fair Good to fair.

Fescue-clover meadow Vacuumized sweeper Poor Poor Good Good.

Fescue meadow Rotating-broom sweeper Fair Fair Good Good.

Fescue-clover meadow Motor grader Fair Poor Poor Good to fair.

Fescue-clover 12" high Motor grader Good to fair Poor Poor Good to fair.

So.vbean stubble Motor grader Fair Poor Poor Good to fair.

So.vbean stubble I'oiistant-draft .scraper Fair Poor Poor Good to fair.

Wheat stubble Vacuumized sweeper Poor Poor Good Good.

Corn stubble Motor grader Poor Poor Poor Good to fair.

Plowed Motor grader Fair Poor Poor Good to fair.

Plowed Bulldozer Good Poor Poor Good to fair.

Plowed Self-loading scraper, leu. yd Fair to good Poor Fair Good to fair.

Plowed Pan-type scraper, S cu. yd. Good Poor Fair Fair.

Disked Motor grader Fair to poor Poor Poor Good to fair.

Disked Rotary scraper Fair to good Poor Fair Good to fair.

Disked Elevating scraper Fair Poor Fair Good to fair.

Seedbed Motor grader Good to fair Poor Poor Good to fair.

Seedbed Bulldozer Good to fair Poor Poor Good to fair.

Seedbed Self-loading scraper Fair Poor Fair Good to fair.

Seedbed Pan-type .scraper Good Poor Fair Fair.

'Rating of removal of radioactivity: Good — > 9.5 percent removal.

Fair — 75-95 percent removal.
Poor — <; 75 percent removal.

° Rating of removal effort : Good — > 5 acres per hour.

Fair — 1 to 5 acres per hour.
Poor — < 1 acre per hour.
' Rating of disposal effort : Good— additional loading and hauling effort minimal.

Fair — considerable effort in loading and hauling.
Poor — very great loading and hauling effort.
* Rating of effect on soil productivity : Good — Increases or does not change productivity.

Fair — ^Reduces productivity <; 20 percent.
Poor — Reduces productivity > 20 percent.

TREATMENTS FOR FARMLAND CONTAMINATED WITH RADIOACTIVE MATERIAL 9

tamination quickly or prevent its spreading to come primarily from external gamma radiation,
other areas. Fallout on sparsely populated farmland would
In case of widespread contamination after a contribute relatively little external gamma radi-
nuclear attack, decontamination effort should be ation to the whole population. It would con-
concentrated in densely populated areas. For tribute more radiation internally through the
the population as a whole, this would give the entry of strontium-90 and other fission prod-
greatest reduction in radiation dose, which would nets into the food chain. Thus, the probable pur-

Table 3. — .4 compiirixon of methods for remoring soil surface contamination in cold weather

Effort required — Effect on

Condition of Implement Removal of For For soil

surface radioactivity ' removal ' disposal ' productivity '

Loose snow 2 to 7" deep Motor grader Poor to good Fair Fair Good.

Do. Carryall scraper Fair Fair Good Good.

Do. Bulldozer Fair Fair Fair Good.

Do. Rotary snow blower Fair Poor Fair Good.

Loose snow 7 to 12" deep Snow plow Good Good Poor Good.

Do. Motor grader Good Fair Poor Good.

Do. Carryall scraper Fair Fair Fair Good.

Do. Rotary snow blower Poor to good Poor Poor Good.

Packed snow Motor grader Fair Fair to poor Fair Good.

Do. Rotary -broom sweeper Fair Fair to poor Good Good.

Do. Vacuumized sweeper Poor to fair Poor Good Good.

Loose snow on Motor grader Poor to fair Poor Fair Good.

packed snow.

Frozen loose snow Snow plow Poor Good Fair Good.

on packed snow.
Frozen ground Jlotor grader Poor Poor Fair Good.

Do. Rotary-broom sweeper Fair to good Poor to fair Good Good.

Do. Vacuumized sweeper Poor to fair Poor to fair Good Good.

Thawing ground Motor grader Good Poor Poor Good to

fair.

Do. Carryall sweeper Good Poor Fair Good to

fair.

Do. Bulldozer Good Poor Poor Good to

fair.

Do. Rotary -broom sweeper Poor Fair Good Good.

' Rating of removal of radioactivity : Good — > 95 percent removal.

Fair — 7.5 to 95 percent removal.
Poor — <; 75 percent removal.
"Rating of removal effort; Good — > 5 acres per hour.

Fair — 1 to 5 acres per hour.
Poor — < 1 acre per hour.
" Rating of disposal effort : Good — additional loading and hauling effort minimal.

Fair — considerable effort in loading and hauling.
Poor — very great loading and hauling effort.
' Rating of effect on soil productivity : Good — Increases or does not change productivity.

Fair — Reduces productivity < 20 percent.
Poor — Reduces productivity > 20 percent.

10

AGRICULTURAL HANDBOOK 395. U.S. DBPT. OF AGRICULTURE

pose of treating farmland after contamination
with widespread fallout would be to reduce up-
take of fission products by plants.

Removal of Crops and Mulches

The presence of a crop would affect the choice
of treatments for a contaminated area. A heavy
crop would intercept part of any contaminating
material that was deposited from the air, such
as fallout. Thus, removal of the crop would
partly decontaminate a land area. However, crop
removal would generally be inadequate. In some
cases, crops might have to be removed before

other, more effective treatments could be carried
out.

The feasibility ratings of methods for remov-
ing crops and mulches are summarized in table 1.
Most common types of crop-liarvesting nuichinery
are compared on crops ranging from meadow to
full-grown corn.

With one exception, none of the methods re-
moved more than 75 percent of simulated fallout
from a contaminated area. The exception is that
taking off a heavy mulch of wheat straw gave
good decontamination. This test was run with
liquid droplet contamination, which apparently
adhered to the straw. Dry fallout contamination

Table 4. — A coinparison of soil management methods for reducing strontium-90 uptake from

contaminated soils.

Method

Reduction in
Sr-90 uptake'

Effort
required '

Effect on soil
productivity*

Minimum tillage

Plowing, 7" deep

Plowing, 12" deep

Plowing, 36" deep

Plowing, 36" deep with

root inhibition.

Irrigation

Leaching

Lime application, 2 to 10

tons/acre.
Nitrogen fertilizers,

100# N/acre.
Phosphate fertilizers,

100# P/acre.
Potassium fertilizers,

500# K/acre.
Organic compost,

5 to 20 tons/acre.
Clay minerals,

.T to 20 tons/acre.
Ammonium or potassium

phosphates, 2 to 5 tons/acre.

Poor to fair Good

Poor Good

Poor Fair .

Fair to poor Poor

Good to fair Poor

Poor Fair to good

Poor Fair

Poor to fair Good

Poor Good

Poor Good

Poor Good

Poor Fair

Poor Fair .

Fair Fair .

-Good to poor.
-Good.
-Good.

-Good to poor.
-Good to poor.

-Good.
-Poor.
-Good.

-Good.

-Good.

-Good.

-Good.

-Good to fair.

.Fair to poor.

'Rating of reduction in Sr-90 uptake: Good — > 95 percent reduction.

Fair — 75 to 95 percent reduction.
Poor — < 75 percent reduction.
' Rating of effort required : Good — Not significantly more than normal field practices.

Fair — Extra equipment, materials, or labor required.
Poor — Very great requirement of equipment, materials, or labor.
' Rating of effect on soil productivity : Good — Increases or does not change productivity.

Fair — Reduces productivity < 20 percent.
Poor — Reduces productivity > 20 percent.

TREATMENTS FOR FARMLAND CONTAMINATED WITH RADIOACTIVE MATERIAL

11

mipht sift through the straw, resulting in poor
decontamination as was achieved with the ber-
mudagrass hay mulch.

In view of the rather poor removal of radio-
activity, crop removal would probably be used
only as a necessary preliminary to some soil treat-
ment that would be more effective. For example,
a bulky crop would interfere with tlie loading of
scrapers, and cause excessive spillage from the
blades of graders or bulldozers. Such crops would
have to be removed before the land could be
decontaminated by scraping. Even then, roots
that could not be cut might decrease the effec-
tiveness of scraping. Areas with trees probably
could not be decontaminated effectively.

Crop removal requires considerable time. The
most rapid methods will clear little more than
one acre per hour.

Tlie problem of disposal of contaminated plant
material has received little attention. It consists
of reducing bulk of the material, hauling it, and
storing it in a safe manner. For the ratings in
table 1, it was considered that crop disposal
would be easier than disposal of surface soil,
since the weight of material to be hauled would
be much less. Methods that remove and load the
plant material for hauling in one operation are
generally less time consuming than those that
do not. Disposal might be in pits or isolated
stacks or buildings.

The removal of crops and mulches would have
no detrimental effect on soil productivity.

Removal of Surface Soil

Decontamination of farmland is easier if the
contaminated surface soil can be removed before
the soil has been cultivated. Penetration of sur-
face contamination into soil by leaching or ero-
sion is minor compared to that in cultivation.
Thus, removal of a few centimeters of surface
soil will give a high degree of decontamination
unless the soil has been disturbed by cultivation
or the surface is so rough that some of the ex-
posed soil is not removed by shallow scraping.

Feasibility ratings are summarized in table 2
for various methods of removing unfrozen con-
taminated surface soil. The equipment ranges
from sweepers, which would remove a minimal
thickness of soil, to heavy earth-moving equip-

ment. Soil conditions vary from a rough plowed
surface to light vegetative covers, wliich are not
expected to interfere with soil removal.

Scraping operations usually remove more than
75 percent of the radioactive contamination on a
soil surface. The removal of radioactivity is
likely to be better from a smooth seedbed than
from a corn stubble or other rough soil surface.

Decontamination with scrapers is ineffective
on stony soils. Scrapers cannot cut at shallow
depths when large stones lie at the soil surface.
Even small stones, a few centimeters in diam-
eter, may cause the scraper blade to roll over
considerable quantities of fine soil containing the
radioactive material. Thus, it would be neces-
sary to scrape repeatedly, or to greater depth,
to achieve a high degree of decontamination.

Rough soil surfaces are common in pastures
and cultivated fields. Freshly plowed surfaces
and row-crop ridges often have differences in
elevation of several inches between the highest
and lowest surface. Land that has been bedded
for furrow irrigation presents even greater ex-
tremes. Since a greater amount of soil would have
to be removed for effective decontamination,
rough surface areas would require extra effort
for soil removal and disposal.

Measurements of the time required for soil re-
moval and disposal were made in the U.S. De-
partment of Defense tests (29) and in some of
our unpublished studies. Bulldozers, road grad-
ers, and scrapers required more than one hour
of equipment time per acre of surface soil re-
moved. It usually required more time to haul the
soil to a disposal pit or pile than it did to scrape
the surface.

Feasibility ratings for disposal (table 2) are
based on the mass of soil to be moved and the
loading effort required after decontamination.
After scraping with a motor grader or bulldozer,
the removed soil must be loaded for hauling to a
disposal area. The sweepers and other scrapers
are loaded during decontamination. The mass
of soil to be hauled is much greater with the
scrapers than with sweepers.

Studies on removal of surface soil have often
shown some loss in soil productivity (3, 34) •
The loss in productivity will vary according to
the depth of fertile soil originally present, and
the amount of soil removed. Restoring the pro-

12

AGKICULTURAL HANDBOOK 395, U.S. DEPT. OF AGRICULTURE

ductivity of the treated area requires improve-
ments in the physical structure and in the nu-
trient supply of the remaining soil. xVdditions
of lime, fertilizers, manure, and mulches help to
restore ])roductivity.

Decontamination in Cold Weather

Subfreezing weather and the possibility of
snow cover exist for part of the year on large
acreages of farmland in the United States. In
cold weather, the removal of surface contamina-
tion would usually be more difficult tlian in warm
weather. If the soil surface were frozen, it could
not be removed by scraping. Vacuum or sweep-
ing machines might be useful unless the con-
taminant had been frozen into the surface.

A snow cover would present different problems,
depending on whether the contaminant was be-
neath it, mixed with it, or deposited on top of it.
In the first case, the snow cover would have to
be removed before the contaminant on the soil
surface could be treated. If additional hazard
would be created by contaminant carried in the
runoff' from melted snow, it might be desirable
to remove the snow cover in spite of the extra
effort required. In case the contaminant was in
or on top of the snow, the area could be decon-
taminated by removing only the snow. However,
the presence of crop residues in the snow cover
would interfere witli snow removal and could
seriously reduce the effectiveness of decontam-
ination.

Studies on the decontamination of land that
was frozen or covered with ice or snow have been
made by the U.S. Army Nuclear Defense Lab-
oratory (£3). Feasibility ratings derived from
their data are given in table 3 for methods that
may be applicable under some farmland condi-
tions.

Several methods removed 75 percent or even
95 percent of the contaminant that had been
deposited on the snow or ground surface. Since
tests were carried out at varying temperatures
and textures of the snow, differences between im-
plements in effectiveness of removal of radio-
activity may not be significant. Tlie texture of

the snow, which varied with the recent temper-
ature history, affected the removal of radio-
activity.

Tlie effort required for removal of radioactive
contaminants in cold weather was not excessive
under the conditions of the tests, which were
run on paved or smooth ground areas. On rough
land areas, the rate of ti'avel would be much
slower. A longer time would be required for
decontamination in such circumstances, even as-
suming that the snow cover permitted effective
decontamination.

Ratings for disposal effort are based on the
weight of materials to be moved, and whether
or not an extra loading operation would be nec-
essary. However, the disposal of contaminated
snow could be very difficult because of its great
bulk. It should be piled so that the contaminant
would not spread by wind, rain, or runoff from
melting snow. If one could let the snow melt
while retaining the contaminant, there would
be much less material for disposal.

No effect on soil productivity would be ex-
pected from snow removal, and removal of thaw-
ing ground should have an effect comparable to
that of removal of surface soil.

No-tillage Management

Wliere the soil surface contains most of the
radioactive contamination, its uptake by crops
could be lessened by growing deep-rooted crops
under conditions of no-tillage. The feasibility
of no-tillage management has been established
for economic production of certain crops {5),
but its possible usefulness as a treatment for con-
taminated land has not been established. It would
have the advantage of keeping the radioactive
material mostly on the surface, where it could
later be removed or otherwise treated. Estimated
feasibility ratings for no-tillage management are
given in table 4.

Deep Placement of Contaminated Soil

Contaminated surface soil may be buried by
plowing. With common farm tractors and plows,
the depth of plowing is limited to about 12 inches.

TREATMENTS FOR FARMLAND CONTAMINATED WITH RADIOACTIVE MATERIAL

13

Large moldboard or disk plows are available in
limited numbere. Some of these plows might not
give efficient burial of contaminated soil (15).
The uptake of radioactivity is much less when
sodium carbonate is placed on the contaminated
soil before deep plowing.

Feasibility ratings for plowing treatments are
summarized in table 4. Plowing to 7 or 12 inches
deep could be carried out with common farm
plows, but it has little effect on uptake of radio-
active strontium. If the hazard were from ex-
ternal gamma radiation from uptake of radio-
activity into plants, plowing would reduce the
hazard very greatly. Plowing 36 inches deep re-
quires special machinery, and the effects on stron-
tium uptake may vary greatly with different soils
and crops. Only by using some material or tech-
nique to stop root growth into the contaminated
soil volume can a highly effective reduction in
uptake be achieved.

The effort required for plowing increases
sharply with increasing depth of plowing. Two
large crawler tractors were required to pull the
plow 36 inches deep in Pullman silty clay loam
(12). About one acre was plowed per hour of
operating time. Two tractor drivers and one man
at the controls of the plow were used. During
large field operations, the rear tractor driver
could possibly control the plow. However, it was
convenient to station an extra man on the front
tractor to warn its driver in case of equipment
breakdown. Thus, from 2 to 4 man-hours were
required per acre plowed.

Many soils would produce poor crops after
deep plowing. This could result from low fertility,
high acidity, soluble salts, or poor texture or
structure of the soil brought to the surface. Fer-
tility and acidity problems could be corrected by
mixing fertilizers and lime into the new topsoil.
Correcting poor soil structure is more difficult
since it may require large additions of sand, com-
post, or manure, and long periods of time for the
improvement of structure. These measures would
add to the already great effort of deep plowing.
Soils with deep, fertile subsoils would be most
likely to produce good crops after deep plowing.
Some impervious soils are benefited by improved
water infiltration after deep plowing (30, 32) .

Irrigation and Leaching

The effectiveness, effort, and productivity rat-
ings of irrigation and leaching treatments for
contaminated land are listed in table 4. Irrigation
does not reduce uptake of radioactive strontium.
Leaching removes little radioactive strontium
from the soil profile unless large quantities of
chemicals are added to increase the movement of
strontium. Therefore, irrigation and leaching
would not be feasible treatments for contami-
nated soils, even though little extra effort might
be needed in some irrigated areas to change the
frequency of irrigation or to leach with large
amounts of water. Soil productivity would be
lowered by leaching because essential nutrient
elements would be removed with the strontium.

Applications of Lime, Fertilizers,
and Other Soil Amendments

The effectiveness, effort, and productivity
ratings of various soil amendments are also given
in table 4. Unfortunately, none of the soil amend-
ments are highly effective in reducing uptake of
radioactive strontium. Large applications of
ammonium or potassium phosphates and, on very
acid soils, the application of lime, will reduce the
uptake of radioactive strontium by 75 percent.
With lime, this is about the maximum reduction
that can be achieved, and it has been observed
only on soils that were initially very low in ex-
changeable calcium. With the phosphates, re-
ductions in the range of 75 to 95 percent have
been observed on a number of soil types in the
greenhouse, but phosphates are much less readily
obtainable than lime, and detrimental effects on
plant growth liave been observed. Field tests have
not been made with the phosphates.

Applications of soil amendments could be made
more easily than most other treatments for con-
taminated land. They would be limited mainly
by the availability of the materials, the effort
required to spread them on the land, and response
of the soil to the amendment. Optimum use of
lime and fertilizers for economic crop production
gives nearly as much reduction in radiostrontium
uptake as can be achieved with heavier applica-
tions of these materials.

14

AGRICULTURAL HANDBOOK 395, U.S. DEPT. OF AGRICULTURE

ALTERNATIVES TO TREATING CONTAMINATED SOIL

lu tlie event of widespread radioactive con-
tamination, such as after a nuclear attack, much
of tlie contaminated farmland could be needed
for crop production before it could be treated.
Since the major hazard from farmland contam-
ination arises from the entry of radionuclides,
especially strontium, into human food, some
alternatives to soil treatment have been suggested.
Among these are using contaminated land to
grow crops that contribute lesser amounts of
radionuclides to the human diet; using contam-
inated pastures for beef or mutton instead of
dairy production; and removing radionuclides
from milk and other products by treatment in
processing. The main characteristics and limita-
tions of these alternatives are important in
determining the feasibility of treating contam-
inated soil.

Some crops would contribute little or no radio-
active material to the human diet, even if they
were grown on highly contaminated soils. Fiber
crops, such as cotton and flax, are obvious ex-
amples. Sugar and oil crops would have most of
the radioactive materials removed from the re-
fined products that are part of the human diet.
However, in case byproducts, such as cottonseed
meal or sugarbeet pulp, are fed to animals, the
indirect contribution of radionuclides to the hu-
man diet would have to be considered. Since corn
has one of the lowest mineral contents of any
grain, its content of radionuclides such as stron-
tium is very low. Other essential food crops, espe-
cially those that contribute important minerals

to the diet, would have to be grown on land with
lesser amounts of contamination. Such crops
would include most fruits and vegetables.

Meat and eggs would contribute little radio-
active strontium to the human diet. Thus, when
the most hazardous contaminating material was
strontium, using the land for beef, pork, mutton,
or poultry production would be advantageous.
This may not be true when other radionuclides
constitute the main hazard. For example, meat
contributes almost as much cesium-137 to the diet
as does milk (36).

Ion-exchange treatment of milk could reduce
its strontium-90 content perhaps more effectively
than decontamination or soil management treat-
ments on hay and pasture land. In full-scale tests
of ion-exchange treatment in a milk-processing
plant, from 90 to 97 percent of the strontium-90
was removed from the milk (35). Similar treat-
ment may be possible with vegetable and fruit
juices and purees, but experimental tests have not
been made.

If the alternatives to ti-eating contaminated
soil were used fully, land for nutritionally criti-
cal crops could be treated preferentially. Critical
crops might vaiy, depending on what crops were
normally produced in the highly contaminated
areas and the possibility of transporting substi-
tutes from other areas. In subsequent years, more
land could be treated for producing critical crops.

In some situations, it might be possible to use
very highly contaminated land by treating the
soil and then using one of the above alternatives.

CONCLUSIONS

Land thai has been contaminated loith radio-
active nrnteriah may he treated to remove the
contaminant or to reduce its entry into food
products. Because these treatments usually re-
quire great effort, the objectives and feasibility
of various treatments need to be carefully evalu-
ated for each contamination incident. Indiscrim-
inate use of ineffeetixe treatments could be very
costly without much reduction in the radiation
hazard to the population.

Treatment objectives may vary according to
the type and extent of contamination. If acci-

dental contamination is confined to a limited area,
it may be removed to pre\ent its spread to other
areas. In such cases, an existing or potential
radiation hazard may be removed without undue
liazard to the decontamination workers. If the
contamination is widespread radioactive fallout,
it may be physically impossible to remove the
entire hazard. Nevertheless, the proper choice of
treatments and land areas to be treated could
reduce significantly the entry of radionuclides
into tlie Inuiian food chain.

Scraping off the surface soil is the most ef-

TREATMENTS FOR FARMLAND CONTAMINATED WITH RADIOACTIVE MATERIAL

15

fectii'B method of removing a surface deposit of
radioactive material. More than 95 percent may
be removed if scraping is carefully clone. Scrap-
ing should be done before the contaminated soil
has been cultivated. Even in favorable circum-
stances, about one hour of equipment time per
acre is required for soil removal and disposal.
Scraping rough or stony soil, or that covered by
coai'se vegetation, is less eti'ective and requires
more effort. Various kinds of scraping machinery
could be used, but those providing easy depth
control and self-loading reduce the effort of soil
removal and disposal. Scraping treatments may
also be effective for contaminated snow surfaces.

^4 rotary-brush street sweeper removes more
than 75 percent of radioactive particles that have
been deposited on a. relatively hard, smooth soil
surface. Two or three passages of the sweeper
remove additional contamination, and the amount
of soil to be disposed of is much smaller than
with scraping equipment. This treatment may
also be effective on ice or frozen soil surfaces.

Vegetative cover would intercept part of a
deposit of radioactive material, aTvd removing the
vegetation might remove up to half of the radio-
active material. Removal of vegetation might be
a necessary preliminary to a more effective treat-
ment such as scraping. Conventional forage-
liarvesting machinery could be used to remove
vegetation.

Lime, fertilizer, or other amsndments may re-
duce the entini of radionuclides from, contami-
nated soils into crops. Use of lime and fertilizers
for optimum economic return often gives the best
reduction in radionuclide uptake. Hence, although
tlie reduced uptake may be 70 or 80 percent of
that with no treatment, it can be obtained at no
cost. Some other amendments, including large
applications of ammonium pliospliate or sodium
carbonate (the latter plowed deeply with the
contaminated soil), may reduce radionuclide up-
take much more effectively. However, the reduc-
tion in uptake is less than would be obtained by
scraping a suitable soil surface, and the treat-
ments would probably be more costly than scrap-
ing.

Alternatives to decontamiriation and soil man-
agement treatments should be considered, espe-
cially if the radioactive material is widespread,
because of the great effort required for effective
treatment of contaminated land. Some altei-na-
tives are growing crops that take up small
amounts of radionuclides and removing radionu-
clides from milk and other products by treatment
during processing. The treatment of contaminated
land might then be limited to those areas needed
for the production of certain vegetable or fruit
crops.

LITERATURE CITED

(1) Aleksakhin, R. M.

196.^. [radioactive contamination of soil and
plants]. Translated from Russian by the
U.S. Atomic Energy Comn., AEC-tr-6631,
pp. 68-86.

(2) Andersen, A, J.

1067. REDUCTION OF THE STRONTIUM-90 UPTAKE
BY BARLEY THROUGH HIGH-TEMPERATUBE
TREATMENT AND DEEP PLACEMENT OF THE

CONTAMINATED SOIL LAYER. In Radioeco-
logical Concentration Processes, pp. 421-
427. Ed. by B. Aberg and F. P. Hungate,
Pergamon, Oxford.

(3) Bachtell, M. a., Willard, C. J., and Taylor,
G. S.

1956. building fertility in exposed subsoil.
Ohio Agr. Expt. Sta. Res. Bui. 782, 35 pp.

(4) Cline, J. F., and Hungate, F. P.

1956. EFFECT of STRONTIUM AND CALCIUM IN SOIL
ON UPTAKE OF SR-90 BY' BARLEY PLANTS.

U.S. Atomic Energy Comn. HW 41500:
81-84.

(5) Deering, R. E.

1967. low-cost farming without a moldboard.
Farm Quarterly 22 (1) : 92-95, 132-138.

(6) Evans, E. J., and Dekker, A. J.

1963. the EFFECT OF POTASSIUil FERTILIZATION
ON THE STRONTIUM-90 CONTENT OF CROPS.

Canad. .Jour. Soil Sci. 43: 309-315.

(7) Frere, M. H., Larson, K. H., Menzel, R. G., and
Others.

1963. THE BEHAVIOR OF RADIO.\CTIVE FALLOUT IN

SOILS AND PLA.NTS. Natl. Acad. Sci. Natl.
Res. Council Pub. 1092, Washington, D.C.,
32 pp.

16

AGRICULTURAL HANDBOOK 395, U.S. DBPT. OF AGRICULTURE

(8) Menzel, R. G., Roberts, H., Jr. and others.

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TREATMENTS FOR FARMLAND CONTAMINATED WITH RADIOACTIVE MATERIAL

17

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1967

[Untitled.] Radiological Health Data and
Reports 8: 154-157.

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