Linking thorium-232 mobility and soil-to-plant transfer with soil characteristics: Céline Siongers

Thorium, a naturally occurring radionuclide, can have an impact on the environment and human health when present in elevated concentrations due to natural or anthropogenic activities. To model the behavior of thorium in the environment, and to estimate the thorium concentration in biosphere compartments, parameters such as the solid-liquid distribution coefficient (Kd) and the soil-to-plant transfer factor (TF) are often used. However, these parameters are highly variable and increase the model uncertainty. These parameters are site specific and cannot be uniformly used without a characterization of the soil. In this study, it is hypothesized that with soil testing for labile Th, in combination with soil characteristics that influence Th sorption, the prediction of Kd and TF values will improve. As such, uncertainties related to risk assessment models will partially decrease. This paper contains a first approach on how to determine the labile thorium fraction in soils. This thesis on the radionuclide mobility of thorium-232 contains a literature study based on the studies and experiments of the mobility of heavy metals in soils. This is a starting point for an experimental study of the mobility of thorium.