Two approaches to the study of radiocaesium partitioning and mobility in agricultural soils from the Chernobyl area

Abstract

Two approaches were followed to study the solid-phase speciation of radiocaesium and predict its mobility and soil-to-plant transfer in agricultural soils from the Chernobyl area. Soils contaminated by Chernobyl fallout or by soluble ¹³⁷Cs were used. From the application of a sequential extraction scheme and a desorption procedure that uses an ion-exchange technique, the amount of radiocaesium potentially available was determined and the time dynamics of its distribution were predicted, with a significant decrease in the exchangeable fraction over time. However, it was not possible to explain its relative mobility in a number of soils, especially in peaty soils. The ion-exchange technique, with longer desorption times, highlighted the heterogeneity and low reproducibility of fuel-particle deposition. In addition, the calculation of distribution coefficients (K_D) allowed the quantification of the partitioning of radiocaesium between specific and regular exchange complex sites (only up to 25% in the latter sites) and, considering K⁺ and NH₄⁺ levels in soil solution, the calculation of in situK_D, which could predict radiocaesium mobility and transfer in the soils studied.