Distribution Coefficients for Radionuclides in Aquatic Environments. Volume 5. Adsorption and Desorption Studies of Plutonium and Americium.

摘要

The distribution coefficents of two important transuranic elements, plutonium and americium, were measured experimentally in several freshwater, estuarine, and marine systems to evaluate the magnitude of their interactions with sediments. The Kd values for sorption of these radionuclides ranged from 1,000 to 1,000,000 ml/g in all the sediment-water systems studied, in agreement with their Kd values reported in the literature. Significant differences between the Kd values obtained for different experimental systems suggest that the amount of Pu and Am removed by sediment particles depends on the sediment type and the water composition. The Kd for desorption of the radionuclides was measured and found to be considerably greater than the sorption Kds in most cases. This indicates that the radionuclide-sediment interactions were not completely reversible under the experimental conditions. The effects of pH and sediment concentration on the Kd values were also investigated. There were significant changes in the Kd values as these parameters were varied. Experiments using sterilized and non-sterilized samples were conducted for some of the sediment-water systems to evaluate possible bacterial effects on Kd. Finally, dialysis experiments were performed to determine the relative importance of suspended sediments, organic detritus, and phytoplankton in removing these radionuclides from both fresh and marine waters.