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Communication Dans Un Congrès Année : 2022

Uranium speciation and transport behavior in the wetland of the former extraction mine of Rophin (France)

C den Auwer

Résumé

Introduction In the vicinity ofold uranium mines, wetlands prove to be specific zones with significant amounts of accumulated U. At the center ofthe ancient mining district of Lachaux in France (45.994°N, 3.596°E), the site of Rophin (within the ZATU: Uranium Working Zone = Long Term SocioEcological Research Tool ofCNRS) is characterized by awetland areawith high U concentrations up to 3.6 g.kg-1. In this context, the main challenge is to describe the behavior ofU and relevant decay products in the wetland using a predictive model that combines chemical speciation and transport. Methods The overall adopted scientific approach is to propose a mechanistic description ofthe mobility of these elements, from the molecular scale (speciation) to in situ behavior (lability), by coupling field and laboratory experiments with modelling. Batch desorption and column experiments were carried out with in situ soil samples to assess the mobile fraction part of U and its distribution coefficients (Kd). Labile behavior of U was examined directly on site by using the DGT/DET techniques while U speciation was investigated by the combination ofseveral techniques (SEM, XAS). From laboratory data, predictive modelling (smart-Kd model) was implemented under sitespecific conditions. Results Observations by SEM, XANES and EXAFS confirmed the U transportin particulate form during the mining activities and the establishment of reducing conditions over time, implying the presence of both U(IV) and U(VI). Labile quantity and Kd values of U were confirmed to be homogeneous at the scale of the Rophin wetland and consistent with in situ labile behavior deduced from the DGT/DET approach, considering a kinetically controlled interaction. Conclusions Thanks to the combination of different techniques, a better understanding of what happened in the wetland over 70 years can be achieved. All these data should now allow us to define the key parameters to be integrated in the reactive part ofthe transport model ofthe Rophin site
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Dates et versions

hal-03842676 , version 1 (01-12-2022)

Identifiants

  • HAL Id : hal-03842676 , version 1

Citer

A.-L Nivesse, C Landesman, A Martin, T Arnold, S Sachs, et al.. Uranium speciation and transport behavior in the wetland of the former extraction mine of Rophin (France). ERPW-2022 European Radiation Protection Week 2022, Oct 2022, Estoril, Portugal. ⟨hal-03842676⟩
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