Indicators of the biological cycle of 90Sr in birch forests of the Bryansk region 30 years aft er the Chernobyl fallout

Abstract

In the paper, the features of the biological cycle of 90Sr in the birch forests of the Bryansk region in the remote period aft er the Chernobyl fallout are discussed. Specific activity and inventories of 90Sr in soil, diff erent structures and types of tree and herbaceous-shrubby stories, higher fungi, and litter are given. It is shown that at present the major part of 90Sr in the contaminated birch forests of the Bryansk Polesie is accumulated in the soil (82,3%), of which about 71% is in the mineral soil horizons. The biota contains only 17,7% of the total radionuclide inventory with maximum values in the tree story. Th e contribution of herbaceous-shrubby vegetation and higher fungi is small, <0,5%. In birch forests 3,07 kBq·m-2 90Sr is involved in the biological cycle, which is about 3% of its total stock in the ecosystem and approximately corresponds to the radioactive decay of this radionuclide. The main part of the 90Sr goes for formation of annual growth of the stand, while the contribution of higher fungi to the cycle exceeds the contribution of the herbaceous-shrubby layer. Th e 90Sr return to soil is lower (48,2%) than its fi xation in annual biomass growth (51,8%).