Distribution and migration of Pu in abiotic components of the Black Sea ecosystems during the post-Chernobyl period.

Distribution of Pu in abiotic components (water and bottom sediment) of the Black Sea ecosystems was studied during the post-Chernobyl period at different offshore and near-shore locations. The trends of these radionuclides accumulation by sediments were analyzed. The spatial-temporal changes in the Pu distribution as well as effective half-life for these radionuclides in the Black Sea surface water in deep-sea area are presented. The estimations of the average annual removal fluxes of the Pu into the bottom sediments were obtained. The Black Sea sediments were characterized by a higher Pu concentration factor (C ≈ n·10-n·10) and radiocapacity factor (F(Pu) was about 99.9% on the shelf, 94.5-99.1% on deep-sea basin for silty and 94.6-98.9% on the shelf for sandy bottom sediments) as compared with C and F for Cs and Sr. Silty bottom sediments play the role of Pu main depot in the Black Sea ecosystem. The studied radioecological characteristics of Pu allowed us to define the type of plutonium biogeochemical behavior in the Black Sea as a pedotropic one. The results of this complex radioecological monitoring of Pu contamination in the Black Sea and their analysis makes it possible to understand the plutonium redistribution pathways which will enable to carry out the tracing of its migration within the ecosystems.