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 m}Ag; ²⁴¹Am; ¹⁰⁹Cd; ⁶⁰Co; ⁵⁷Co-cobalamine; ¹³⁴Cs; ¹⁵²Eu; ⁵⁴Mn; ¹³³Ba; ¹⁰⁶Ru; and ⁸⁵Sr. The major findings of this investigation are that 1. radionuclide distribution coefficients (K_ds) 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 m}Ag. The observed differences in K_ds for sediments from the two dumpsites exemplifies the importance of undertaking site-specific determinations of K_ds. 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).