Soil-soil solution distribution coefficients for radionuclides in Japanese agricultural soils

One of the key parameters required in modeling the behavior of radionuclides in the biosphere is the soil-soil solution distribution coefficient (Kd). In order to provide more reliable estimates, it is necessary to obtain Kd data for each important radionuclide in various soil groups and to identify the soil properties that influence these Kd values. In this study, we used 142 agricultural soil samples collected throughout Japan, and determined Kd values for 63Ni, 75Se, 85Sr, 113Sn, 124Sb, and 137Cs. We then examined the relationships between the Kd values of each radionuclide and soil properties by means of statistical analysis. Soil samples were classified into four groups: Andosol (n=35), Cambisol (n=25), Fluvisol (n=77), and other (n=5). The Kd values for all six radionuclides in all soil samples were determined by means of batch sorption tests. Geometric means of the Kd values were Sn>Cs>Ni>Sr>Se>Sb. When we compared the Kd values of Se, Sr, Sb, and Cs between the four soil groups, we found no significant differences (t-test, p>0.05). The Kd values of Ni and Sn were higher in the Andosol group than in the Cambisol and Fluvisol groups. The effects of soil properties on Kd variation differed significantly among the soil groups for all radionuclides except Sr. (author)