Laboratory Experiments to Study Radiocaesium Interaction in Organic Soils

Abstract

The total concentration of a pollutant in a given environmental compartment is often used for risk assessment. However, the real impact of the pollutant also depends on its toxicity and mobility. In soils, pollutant mobility is strongly related to its interaction with the different sites. The mechanisms and dynamics of this interaction may be studied by adsorption and desorption approaches. Adsorption experiments based on the measurement of the pollutant solid-liquid distribution coefficient (K_D) determine the interaction capacity of the soil and identify the nature of the sites involved. Desorption experiments based on single, sequential or consecutive extractions show the reversibility of the adsorption process (soil fixation capacity) and how it might be affected by changes in field conditions. They also predict changes in reversibility over time. In this work, the study of radiocaesium interaction in organic soils is used to illustrate these statements. In this study, the combined use of adsorption and desorption experiments shows that, even in highly organic soils, the specific sites of clay materials may govern radiocaesium behaviour.