Experimental redox transformations of uranium phosphate minerals and mononuclear species in a contaminated wetland

JOURNAL OF HAZARDOUS MATERIALS

卷:384

Article

Stetten, Lucie^1,2,3  Lefebvre, Pierre¹  Le Pape, Pierre¹  Mangeret, Arnaud²  Blanchart, Pascale²  Merrot, Pauline¹  Brest, Jessica¹  Julien, Anthony²  Bargar, John R.⁴  Cazala, Charlotte²  Morin, Guillaume¹ 

[1] Sorbonne Univ, Inst Mineral Phys Mat & Cosmochim IMPMC, UMR 7590 CNRS, IRD MNHN, Case 115,4 Pl Jussieu, F-75252 Paris 5, France

[2] Inst Radioprotect & Surete Nucl, IRSN, 31 Ave Div Leclerc, F-92262 Fontenay Aux Roses, France

[3] Univ Vienna, Ctr Microbiol & Environm Syst Sci, Dept Environm Geosci, Althanstr 14,UZA 2, A-1090 Vienna, Austria

[4] SLAC Natl Accelerator Natl Lab, Stanford Synchrotron Radiat Lightsource SSRL, MS 69,2575 Sand Hill Rd, Menlo Pk, CA 94025 USA

关键词: Wetland;    Uranium;    Redox transformations;    Soil incubation;    X-ray absorption spectroscopy;   

DOI  :  10.1016/j.jhazmat.2019.121362

来源: Elsevier

【 摘 要 】

Reducing conditions and high organic carbon content make wetlands favorable to uranium (U) sequestration. However, such environments are subjected to water-table fluctuations that could impact the redox behavior of U and its mobility. Our previous study on U speciation in a contaminated wetland has suggested a major role of water-table redox fluctuations in the redistribution of U from U(IV)-phosphate minerals to organic U(VI) and U(IV) mononuclear species. Here, we investigate the mechanisms of these putative processes by mimicking drying or flooding periods via laboratory incubations of wetland samples. LCF-XANES and EXAFS analyses show the total oxidation/reduction of U(IV)/U(VI)-mononuclear species after 20 days of oxic/anoxic incubation, whereas U-phosphate minerals are partly oxidized/reduced. SEM-EDXS combined with mu-XRF and mu-XANES analyses suggest that autunite Ca(UO2)(2)(PO4)(2)center dot 11H(2)O is reduced into lermontovite U(PO4)(OH)center dot H2O, whereas oxidized ningyoite CaU(PO4)(2)center dot 2H(2)O is locally dissolved. The release of U from this latter process is observed to be limited by U(VI) adsorption to the soil matrix and further re-reduction into mononuclear U(IV) upon anoxic cycling. Analysis of incubation waters show, however, that dissolved organic carbon enhances U solubilization even under anoxic conditions. This study brings important information that help to assess the long-term stability of U in seasonally saturated organic-rich contaminated environments.

【 授权许可】

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