The transfer of 137Cs and 90Sr to dairy cattle fed fresh herbage collected 3.5 km from the Chernobyl nuclear power plant

A study conducted during summer 1993 to determine the bioavailability and transfer of 137Cs and 90Sr to dairy cattle from herbage collected from a pasture contaminated by particulate fallout is described. The study pasture was located 3.5 km from the Chernobyl nuclear power plant. The true absorption coefficient (At) determined for 137Cs (0.23) was considerably lower than previous estimates for radiocaesium incorporated into vegetation by root uptake. It is likely that the low dry matter digestibility of the diet and the potential presence of 137Cs associated with adherent soil-associated fuel particles contributed to this low bioavailability. The At value determined for 90Sr (0.27) did not indicate a reduced bioavailability. It is suggested that the current and previous calcium status of the animals was the controlling influence on the transfer of 90Sr from the diet to milk.