Carbonate Facilitated Mobilization of Uranium from Lacustrine Sediments under Anoxic Conditions

Seder-Colomina, Marina; Mangeret, Arnaud; Stetten, Lucie; Merrot, Pauline; Diez, Olivier; Julien, Anthony; Barker, Evelyne; Thouvenot, Antoine; Bargar, John; Cazala, Charlotte; Morin, Guillaume

doi:10.1021/acs.est.8b01255

Title: Carbonate Facilitated Mobilization of Uranium from Lacustrine Sediments under Anoxic Conditions

Journal Article · Sat Jul 07 00:00:00 EDT 2018 · Environmental Science and Technology

DOI:https://doi.org/10.1021/acs.est.8b01255· OSTI ID:1476326

Seder-Colomina, Marina ^[1];

^[1]; Stetten, Lucie ^[2]; Merrot, Pauline ^[3]; Diez, Olivier ^[1]; Julien, Anthony ^[1]; Barker, Evelyne ^[1]; Thouvenot, Antoine ^[4]; Bargar, John ^[5]; Cazala, Charlotte ^[1]; Morin, Guillaume ^[3]

Inst. for Radiological Protection and Nuclear Safety (IRSN), Fontenay-aux-Roses (France)
Inst. for Radiological Protection and Nuclear Safety (IRSN), Fontenay-aux-Roses (France); Inst. of Mineralogy, Materials Physics and Cosmochemistry (IMPMC), Paris (France)
Inst. of Mineralogy, Materials Physics and Cosmochemistry (IMPMC), Paris (France)
Univ. Clermont Auvergne, Clermont-Ferrand (France). Lab. Microorganims: Genome and Environment (LMGE)
SLAC National Accelerator Lab., Menlo Park, CA (United States). Stanford Synchrotron Radiation Lightsource (SSRL)

Sorbed U(IV) species can be major products of U(VI) reduction in natural reducing environments as sediments and waterlogged soils. These species are considered more labile than crystalline U(IV) minerals, which could potentially influence uranium migration in natural systems subjected to redox oscillations. In this work, we examined the role of oxygen and carbonate on the remobilization of uranium from lake sediments, in which ~70% of the 150–300 ppm U is under the form of mononuclear U(IV) sorbed species. Our results show that both drying and oxic incubation only slightly increase the amount of remobilized U after 8 days, compared to anoxic drying and anoxic incubation. In contrast, the amount of remobilized U increases with the quantity of added bicarbonate even under anoxic conditions. Moreover, U L_III-edge XANES data show that a significant amount of the solid U(IV) is mobilized in such conditions. Thermodynamic speciation calculations based on the supernatant composition indicates the predominance of aqueous UO₂(CO₃)₃^4– and, to a lesser extent, CaUO₂(CO₃)₃^2– complexes. These results suggest that monomeric U(IV) species could be oxidized into aqueous U(VI) carbonate complexes even under anoxic conditions via carbonate promoted oxidative dissolution, which emphasizes the need for considering such a process when modeling U dynamics in reducing environments.

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Research Organization:: SLAC National Accelerator Lab., Menlo Park, CA (United States)

Sponsoring Organization:: USDOE Office of Science (SC), Biological and Environmental Research (BER); USDOE Office of Science (SC), Basic Energy Sciences (BES); National Institutes of Health (NIH)