Interactions in a cesium, strontium, natural organic matter, soils clays system. From decontamination to remediation

This study is part of the DEMETERRES project, which aims to develop new methods and technologies in the field of decontamination and remediation of contaminated soils and effluents after a nuclear accident. The objective of this PhD is to obtain a better knowledge of ¹³⁷Cs and ⁹⁰Sr interactions onto agricultural soils and to better predict the chemical state of these elements in soils after a nuclear accident. A database in the multi-sites ion exchanger formalism has been built, reflecting the adsorption behaviours of Cs⁺ and Sr²⁺ onto illite and smectite (two major clay minerals) with regards to major environmental cations: i.e. H⁺, Na⁺, and Ca²⁺. It was used to predict the adsorption of Cs⁺ and Sr²⁺ onto French agricultural soil samples (Pusignan, Etoile-sur-Rhone and Herqueville). Good simulations of the adsorption of Cs⁺ and Sr²⁺ onto Pusignan and Etoile-sur-Rhone are obtained. In the case of Herqueville, the removal of NOM does not improve the agreement between experimental results and simulations, but the removal of exchangeable aluminum allows a better representation of the adsorption results of Sr²⁺ onto Herqueville, but not for Cs⁺. This work allows efficiently simulating the adsorption of Cs and Sr onto soils and support decontamination and remediation strategies after a nuclear accident. (author)