Quantitative analysis of radiocaesium retention in soils

Abstract

The fallout of radiocaesium after the Chernobyl accident has renewed interest in its environmental behaviour. How it behaves in soils and sediments is important, for example, for the modelling of radiocaesium transport and retention in soils, and transfer from soil to plants and hence into the food chain. The traditional approach is highly empirical and is based on the measurement of solid–liquid distribution coefficients (K_D values) and transfer factors. It is generally believed that radiocaesium retention in soils and sediments is due to the presence of a small number of highly selective sites. Neither their abundance nor their Cs-selectivity has been quantitatively determined. Here we report a new methodology which achieves such characterization. Previously studies of radio-caesium in soils have foundered because K_D values have been derived under conditions very different from those in situ. We show that in situ K_D values can be predicted from readily measurable soil properties, thus enabling information about the mobility of radiocaesium in soils to be reliably and easily obtained. These findings can be generally applied to a wide variety of soils.