Effect of soil characteristics on soil particle size dependence of distribution coefficient

In order to clarify parameters which determine soil particle size dependence of radionuclide (⁶⁰Co, ⁸⁵Sr and ¹³⁷Cs) distribution coefficient, the correlations between the distribution coefficient and the soil characteristics (specific surface area, ion exchange capacity, exchanged ion species and mineral composition) were studied for the coastal sand sieved into nine classes in particle size. It was found that the distribution coefficient was strongly connected with the specific surface area and the clay mineral content. Furthermore, it seemed that the distribution coefficient was separated into two components; one is the component corresponding to the ion-exchange adsorption which is represented as a linear function of specific surface area, and the other is the component corresponding to the fixation depending on the clay mineral content. It was concluded that the soil particle size dependence of radionuclide distribution coefficient is attributable to the specific surface area and the clay mineral content, and that the content ratio of silt and clay which have large specific surface area and rich clay mineral, has an important effect on the radionuclide distribution coefficient. (author)