Uranium(VI) attenuation in a carbonate-bearing oxic alluvial aquifer

JOURNAL OF HAZARDOUS MATERIALS

卷:412

Article

Nolan, P. J.^1,7  Bone, Sharon E.²  Campbell, Kate M.³  Pan, Donald^4,8  Healy, Olivia M.⁴  Stange, Marty⁵  Bargar, John R.^2,4,6  Weber, Karrie A.^1,4,6 

[1] Univ Nebraska, Dept Earth & Atmospher Sci, Lincoln, NE USA

[2] SLAC Natl Accelerator Lab, Stanford Synchrotron Radiat Lightsource, Menlo Pk, CA USA

[3] US Geol Survey, Boulder, CO USA

[4] Univ Nebraska, Sch Biol Sci, 232 Manter Hall, Lincoln, NE 68588 USA

[5] City Hastings, Hastings Util, Hastings, NE USA

[6] Univ Nebraska, Daugherty Water Food Global Inst, Lincoln, NE USA

[7] Golder Associates Inc, Redmond, WA USA

[8] Florida Gulf Coast Univ, Water Sch, Dept Ecol & Environm Studies, Ft Myers, FL USA

关键词: Uranium;    Groundwater;    Geogenic contamination;    Uranium carbonate minerals;   

DOI  :  10.1016/j.jhazmat.2021.125089

来源: Elsevier

【 摘 要 】

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 ?13C (0.57%o ? 0.15%o) 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 ?g/L), presenting a deposition mechanism for uranium attenuation rather than solely a means of mobilization.

【 授权许可】

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