Creation of a database of polonium distribution coefficient in soils

Abstract

The solid-liquid distribution coefficient (Kd) is a useful parameter for describing the sorption of elements and compounds, such as radionuclides, into soils. It is also a key input parameter in many risk assessment codes intended to predict the effect of radioactive contamination on humans. Unfortunately, it is a parameter subjected to many sources of variability, which sometimes hinder its applicability in these models. The sources of variability originate from the experimental approaches followed for its determination, and also from the dependence of Kd on the type of radionuclide and soil properties. This project is going to be carried out within the international project H2020-EURATOM which, among others, aims to create new Kd databases from the information reported in the literature for radionuclides of natural origin (NOR) and also from new NOR sorption experiments with soils with varying edaphic properties. The present project will focus on polonium, considered as one of the most radiotoxic NORs, and for which little is known about the main mechanisms affecting its sorption in soils. Thus, it is intended to perform an exhaustive literature search, obtain a critically reviewed solid-liquid distribution coefficient dataset and, subsequently, to examine the main soil properties affecting the Kd(Po) variability through statistical analysis. The analyzed data has revealed that parameters as textural composition, organic matter content or pH may an important impact on Po sorption in soils. However, at the same time, uncontrolled factors and experimental methodology lead to a significative source variability that has de be dealt with in order to have more consistent results.