Uranium(VI) attenuation in a carbonate-bearing oxic alluvial aquifer
| Autor: | Marty Stange, Sharon E. Bone, Karrie A. Weber, Donald Pan, John R. Bargar, P.J. Nolan, Kate M. Campbell, Olivia M. Healy |
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| Rok vydání: | 2020 |
| Předmět: |
inorganic chemicals
Environmental Engineering Health Toxicology and Mutagenesis 0211 other engineering and technologies Alkalinity chemistry.chemical_element 02 engineering and technology 010501 environmental sciences complex mixtures 01 natural sciences chemistry.chemical_compound Environmental Chemistry Maximum Contaminant Level Waste Management and Disposal 0105 earth and related environmental sciences Geochemical modeling Calcite 021110 strategic defence & security studies Chemistry technology industry and agriculture Uranium Pollution Environmental chemistry Carbonate Liebigite Groundwater |
| Zdroj: | Journal of hazardous materials. 412 |
| ISSN: | 1873-3336 |
| Popis: | Uranium minerals are commonly found in soils and sediment across the United States at an average concentration of 2–4 mg/kg. Uranium occurs in the environment primarily in two forms, the oxidized, mostly soluble uranium(VI) form, or the reduced, sparingly soluble reduced uranium(IV) form. Here we describe subsurface geochemical conditions that result in low uranium concentrations in an alluvial aquifer with naturally occurring uranium in soils and sediments in the presence of complexing ligands under oxidizing conditions. Groundwater was saturated with respect to calcite and contained calcium (78–90 mg/L) with elevated levels of carbonate alkalinity (291–416 mg/L as HCO3−). X-ray adsorption near edge structure (XANES) spectroscopy identified that sediment-associated uranium was oxidized as a uranium(VI) form (85%). Calcite was the predominant mineral by mass in the ultrafine fraction in uranium-bearing sediments (>16 mg/kg). Groundwater geochemical modeling indicated calcite and/or a calcium-uranyl-carbonate mineral such as liebigite in equilibrium with groundwater. The δ13C (0.57‰ ± 0.15‰) was indicative of abiotic carbonate deposition. Thus, solid-phase uranium(VI) associated with carbonate is likely maintaining uranium(VI) groundwater levels below the maximum contaminant level (MCL; 30 µg/L), presenting a deposition mechanism for uranium attenuation rather than solely a means of mobilization. |
| Databáze: | OpenAIRE |
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