DEPTH MIGRATION OF CHERNOBYL ORIGINATED CS-137 AND SR-90 IN SOILS OF BYELARUS

Depth migration of Cs-137 and Sr-90 was studied in soils of reference sites that have different environmental characteristics and are situat ed in all four radiogeochemical regions of Belarus. The parameters as used were: the fraction of the nuclide inventory below a depth of 2 cm ; the fraction of the nuclide inventory below a depth of 5 cm; and the thickness of the top soil layer containing 90% of the nuclide invento ry. Despite the apparent differences in the nuclide migration at vario us sites, some common tendencies were observed. During the first 3-5 y ears after the accident, the Sr-90 depth migration at several watershe d and terrace sites did not exceed that of Cs-137. About 5-15% of the nuclide inventories are below the depth of 5 cm, and 90% are contained in the top 3-7 cm soil layer. However, at the floodplain reference si tes, a pronounced tendency for a higher migration rate of Sr-90 was re vealed. Less than 5% of the Cs-137 inventory but about 5-30% of the Sr -90 inventory are below 5 cm, and the top soil layer containing 90% of hte nuclide inventory is 1-2 cm thicker for Sr-90. Copyright (C) 1996 Elsevier Science Limited