COMPARISON OF THE UPTAKE OF RADIOCESIUM FROM SOIL TO GRASS AFTER NUCLEAR-WEAPONS TESTS AND THE CHERNOBYL ACCIDENT

In order to compare the transfer factors of Cs-137 deposited after the fallout from the Chernobyl accident with Cs-137 from nuclear weapons testing, soil and vegetation samples have been collected from a semi-natural ecosystem in western Norway. For the Cs-137 from Chernobyl, 85% is found in the upper 5 cm of soil, whereas most of the nuclear weapons test Cs-137 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 Cs-137 and 0.40 +/- 0.22 m2 kg-1 for Chernobyl Cs-137. Hence, the results show no significant difference between the two fallouts. The effective ecological half-life of Cs-137 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.