N. Green et al., FACTORS AFFECTING THE TRANSFER OF RADIONUCLIDES TO SHEEP GRAZING ON PASTURES RECLAIMED FROM THE SEA, Journal of environmental radioactivity, 30(2), 1996, pp. 173-183
The ingestion of soil by sheep grazing on pasture reclaimed from the s
ea has been studied. Seasonal variation of soil intake was small compa
red to that found in a parallel study at an inland farm, but this coul
d be explained by the husbandry, specifically the provision of supplem
entary feed during the winter months, and the quality of the pasture.
The quantity of soil ingested, expressed as a percentage of the dry ma
tter intake, was typically about 2%, much lower than values normally u
sed in models used to assess the impact of radionuclides in the enviro
nment. These results have been combined with relevant data from earlie
r studies at this same site in order to quantify the factors affecting
intakes of various radionuclides by; sheep and their onward transfer
along the foodchain. Strontium-90 and Tc-99 have relatively, high soil
:grass transfer factors and ingestion of soil-associated activity was
not an important contributor to intakes. For Cs-137, the relative cont
ributions to intake from activity incorporated into foliage and from t
hat associated with soil were about equal. However, after ingestion mo
st of the soil-associated Cs-137 activity would be unavailable for upt
ake by the animal, and so soil:grass transfer was the most important c
ontributor, to the subsequent transfer to animal products. For Pu-239,
Pu-240 and Am-241, inadvertent ingestion of soil-associated activity.
This process was also the most important contributor to uptake even th
ough only about 5% of the soil-associated activity, was soluble in rum
en fluid. The implications of these results for radiological assessmen
ts are discussed.