Reactive transport of Sr at two laboratory-scale columns: experiments and modeling
Résumé
In support to the environmental monitoring of nuclear sites, predictions of reactive transport models used to simulate the contaminant migration such as 90Sr in soils, sediments and aquifers have to be improved. The objectives of this study are to evaluate the coupling between the multi-site ion exchanger model (MSIE), based on a component additivity approach, and the advection-dispersion equation (ADE) to simulate Sr transport in two-component materials. Non-reactive transport experiments with conservative tracers are used to determine transport parameters, such as total porosity and dispersivity. The reactive transport model was used to simulate Sr transport in a Bt soil and a clayey sandstone in centimeter and decimeter scale columns. Simulation results obtained with the additivity approach were compared to those obtained with a generalized composite approach (Kd). Simulations results shows that the Kd approach often fails to reproduce experimental data whereas the additivity approach successfully predicts the Sr reactive transport in a clayey sandstone both at the centimeter and decimeter scales without any adjustment of parameters. These results justify taking into account more complex retention model in reactive transport models to understand and improve the robustness of Sr transport prediction. Sorption property of a low capacity and high selectivity site on illite was revealed to be a determining parameter in Sr transport behavior. However, this database is restricted to minerals having similar reactivity than the references used and has to be extended to soil clay minerals.
Domaines
Milieux et Changements globaux
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