INGESTED SOIL AS A SOURCE OF CS-137 TO RUMINANTS

Ingestion of soil has been identified as a potentially important sourc e of radionuclides, particularly to grazing ruminants. Soil artificial ly contaminated with radiocaesium was administered orally each day for 33 days to Bergamasca sheep and the transfer to milk measured. Two so il types were used, with a clay content of 11% and 16%, respectively. Transfer coefficient (f(m)) values to sheep milk, calculated at the eq uilibrium (period from 7th to 21st day after soil administration), wer e 3.72 x 10(-4) days l-1 (S.D. = 7.2 x 10(-5) days 1-1) and 6.11 x 10( -4) days 1-1 (S.D. = 9.1 x 10(-5) days l-1), respectively for the two soils. These low values indicate that radiocaesium is not removed from the binding sites on the clay minerals in the gut of the sheep.