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MARTIN : RADIOECOLOGY AND STUDY OF ENVIRONMENTAL RADIATION

305

on plants during a period of three weeks following contamination was parallel to the beta decay of < 44» fallout particles.*
Under favorable conditions, some of the water soluble material deposited
on leaves maybe assimilated byfoliar absorption. Russell et al. (1955, 1959)
and Russell and Possingham (1959) reporting on fallout studies made in
Australia and in the United Kingdom, have indicated that considerable

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quantities of water soluble fission products may be retained by foliar ab-

Sr

sorption. Since there have been no direct observations of foliar absorption
of fallout originating from detonations at the Nevada Test Site (Romney
et al. 1962) we may suppose that foliar absorption is probably more significant in humid grassland or pasture regions than in arid grassland or
desert-shrub regions.
3. Animals. The possible modesof fission product ingestion by herbivores
are: (a) ingestion of fallout contaminated plants, (b) ingestion of fallout

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Table 8. dverage beta activity in tissues of jack rabbits serially collected from an
area contaminated by fallout from the Nevada Test Site* (80 miles from Ground Zero).

_——_— — o =o

Time of
Collection,
Days after
Contamination
2

3
10

220
Baekground**

Average beta activity extrapolated to time of sampling and
expressed as npe/g fresh tissue
Lung
Caecum
Liver
Kidney
Muscle
Bone
116
61
21

1
1

16,500
4,350
606

.

6
7

817

67

3
1

2
1

990
21

55
18

385

639

3
1

3
2

376
10

103
60

* After: Lindberg et al. (1959).
** Based on animals eollected before contamination.

oS
8

i9

20

k rabbits colFrom Larson

ield studies
ntaminated

of activity

from the pelt during preening, (c) accidental ingestion of contaminated soil
while digging or feeding, and (d) swallowing of material cleared from the
lungs and nasopharynx. Duringthe first few weeks after fallout, the correlation between the activity of plants and that of the gut contents of herbivores is usually quite close, and the other three possible modes of ingestion
are probably of minor significance.
The maximum concentration of mixed fission products in the tissues of
herbivores living in fallout contaminated environments occurs usually
within a few days after fallout. The total body burden of internal beta
emitters then decreases (Figure 7) in proportion to the decreased activity
of forage plants, and this may approximate the rate of mixedfission product decay.
* Studies completed after this paper was written (Martin 1963, 1964) have shown
that the effective half-lives of radionuclides on fallout-contaminated plants are significantly shorter than their respective radioactive half-lives, and losses in excess of radioactive decay have been attributed primarily to wind action,

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