Influence of humic acid on migration of 60Co, 85Sr and 137Cs in coastal sandy soil

Sorption and migration experiments were performed by both batch and column methods, to study influence of humic acid complexing on the mobility of 60Co, 85Sr and 137Cs in a coastal sandy soil. The study focuses on a correlation between molecular-weight of dissolved humic acid and ability of the complexing with the radionuclides in liquid phase. Dissolved humic acid was complexed with 60Co and 85Sr. The interaction ability of 60Co was independent of molecular-weight of humic acid, while that of 85Sr depended on. The mobility of 60Co increased under the condition with coexistence of humic acid as well as its sorption ratio decreased. The distribution profile of molecular-weight of 60Co was kept at a constant in the solution before and after the sorption experiment, due to completing the sorption and complexation equilibrium. The mobility of 85Sr increased under the condition with coexistence of humic acid, in spite of the sorption ratio of 85Sr was not affected by the coexistence. Such contradiction was caused by different kinetics between the batch and column methods. The sorption ability and mobility of 137Cs were not affected by the coexistence of the humic acid. (author)