Distribution coefficients (Kd) and desorption rates of 137Cs and 241Am in Black Sea sediments

The distribution coefficients (Kd) and desorption rates of 137Cs and 241Am radionuclides in bottom sediments at different locations in the Black Sea were studied under laboratory conditions. The Kd values were found to be 500 for 137Cs and 3800 for 241Am at the steady state and described exponential curves. Rapid uptake of the radionuclides occurred during the initial period and little accumulation happened after four days. The desorption rates for 137Cs in different bottom sediments were best described by a three-component exponential model. The desorption half-times of 137Cs ranged from 26 to 50 d at the slow components. However, the desorption rate of 241Am described one component for all sediment samples and desorption half-time was found to be 75 d. In general, the results showed that the 241Am radionuclide is more effectively transferred to bottom sediment and has longer turnover time than 137Cs under Black Sea conditions.