RADIOCESIUM TRANSFER TO SHEEPS MILK AS A RESULT OF SOIL INGESTION

Soil ingestion as a source of radiocaesium contamination to ruminants was studied by measuring the transfer coefficient to sheep milk. Eight lactating ewes, housed in individual metabolism cages, were used. Fif ty grams per day of heavily contaminated sandy topsoil, collected in 1 990 from the Chernobyl area, were administered orally to the animals f or a period of 1 week. The daily dose intake in Cs-137 was 1835 Bq day -1. During this contamination period, daily milk production and excret a output were measured. The ewes were monitored for an additional 7 da y decontamination period, while they fed on uncontaminated feed. Trans fer coefficients were obtained through a best fit (minimum chi2) of th e data to predictions of a linear compartment model. The values obtain ed were f(m) = (2.6 +/- 0.7) x 10(-2) and f(u( = (5 +/- 2) x 10(-2) da ys kg-1 for radiocaesium transport to milk and urine, respectively. Th ese results suggest that soil ingestion can be a major source of radio contamination for sheep and other free-grazing ruminants. Comparison o f our results with soil-to-milk transfer coefficient values derived in two recent independent experiments suggests that there might be a str ong dependence of radiocaesium availability on soil composition.