Colloidal Migration Behavior of Radionuclides Sorbed on Mobile Fine Soil Particles through a Sand Layer

摘要

Migration properties of 60Co, 85Sr and 137Cs sorbed on fine soil particles have been examined by a column method. The influent solutions containing both the radionuclides and the fine soil particles smaller than 5μm in diameter were introduced in the coarse sand column of different length between 1 and 10cm. The first order desorption rate constants of the radionuclides from the fine soil particles to the coarse sand were estimated from the relation between the effluent amounts of the radionuclides and the column lengths. The sorption ratios of the radionuclides on the fine soil particles and the coarse sand were obtained by a batch method.The effluent amounts of the radionuclides decreased with increasing length of the column, then kept a constant values. At the column of 10cm, the effluent amounts of 60Co, 85Sr and 137Cs relative to the influent ones were 0.3, 0.1 and 0.8, respectively. The sorption ratio of each radionuclide for the fine soil particles was several 10 times larger than that for the coarse sand. First order desorption rate constants of the radionuclides from the fine soil particles were in the order of 85Sr>137Cs>60Co. These results show that higher affinity of the radionuclides to the fine soil particles than the coarse sand results the colloidal migration of the radionuclides sorbed on the fine soil particles.