Radionuclide adsorption to sediments from nuclear waste dumping sites in the Kara Sea

Environmental parameters (salinity, sediment concentration, equilibration time) affecting radionuclide partitioning between sediment and seawater were experimentally investigated for Kara Sea sediments collected from nuclear waste dumping sites in Abrosimov and Stepovogo Bays off Novaya Zemlya. Adsorption kinetics were examined and the influence of salinity and sediment concentration were evaluated over the range of concentrations expected in the bays for the following radionuclides: 110 mAg; 241Am; 109Cd; 60Co; 57Co-cobalamine; 134Cs; 152Eu; 54Mn; 133Ba; 106Ru; and 85Sr. The major findings of this investigation are that 1. radionuclide distribution coefficients (Kds) were most sensitive to variations in sediment character (241Am, 60Co, 109Cd) and concentration (57Co-cobalamine, 85Sr, and 133Ba), 2. distribution coefficients generally decreased with increasing sediment concentration and 3. fast adsorption kinetics (near equilibrium ≈1 day) were observed only for 137Cs and 110 mAg. The observed differences in Kds for sediments from the two dumpsites exemplifies the importance of undertaking site-specific determinations of Kds. For purposes of confining radioactive wastes to the dumpsites in Stepovogo and Abrosimov Bays, the findings of this study indicate that based on sediment character alone, Stepovogo Bay will be more effective at retaining radionuclides than Abrosimov Bay. This is unfortunate since less radioactive waste resides in Stepovogo Bay (0.6 PBq) than in Abrosimov Bay (1.4 PBq).