Comparison of the uptake of radiocaesium from soil to grass after nuclear weapons tests and the Chernobyl accident.

In order to compare the transfer factors of 137Cs deposited after the fallout from the Chernobyl accident with 137Cs from nuclear weapons testing, soil and vegetation samples have been collected from a semi-natural ecosystem in western Norway. For the 137Cs from Chernobyl, 85% is found in the upper 5 cm of soil, whereas most of the nuclear weapons test 137Cs is found between 3 and 12 cm in the soil profile. The transfer factors from soil to vegetation are calculated to be 0.41 +/- 0.07 m2 kg-1 for the nuclear weapons test 137Cs and 0.40 +/- 0.22 m2 kg-1 for Chernobyl 137Cs. Hence, the results show no significant difference between the two fallouts. The effective ecological half-life of 137Cs for this ecosystem is estimated to be between 10 and 20 years. Wash-out and binding effects seem to be of minor importance for the uptake.