New best estimates for radionuclide solid–liquid distribution coefficients in soils, Part 1: radiostrontium and radiocaesium

Best estimates for the solid-liquid distribution coefficients (Kd) of radiostrontium and radiocaesium for various soil types, were derived from geometric means (GM) calculated from grouping soils by texture and organic matter content, and also using soil cofactors governing soil–radionuclide interaction. The Kd (Sr) GM for Sand, Loam, Clay and Organic groups were similar, although the value for the Sand group was significantly lower. The Sr cofactor approach, based on the ratios of cation exchange capacity (CEC) to Ca and Mg concentrations in the soil solution, leads to Kd (Sr) GM with a lower variability, from which best estimates could be proposed. The Kd (Cs) GM for Sand and Organic groups differed, although similar values were obtained for Loam and Clay groups. Grouping the Kd (Cs) according to the Radiocaesium Interception Potential (RIP) and the RIP divided by the K concentration in the soil solution also allows to suggest Kd (Cs) best estimates with a lower variability.