Earth and Atmospheric Sciences, Department of


Date of this Version



Environ. Sci. Technol. 2023, 57, 4354−4366



U.S. government work

Experimentally derived data reported in this study have been deposited in the University of Nebraska-Lincoln Data Repository (


Groundwater uranium (U) concentrations have been measured above the U.S. EPA maximum contaminant level (30 μg/L) in many U.S. aquifers, including in areas not associated with anthropogenic contamination by milling or mining. In addition to carbonate, nitrate has been correlated to uranium groundwater concentrations in two major U.S. aquifers. However, to date, direct evidence that nitrate mobilizes naturally occurring U from aquifer sediments has not been presented. Here, we demonstrate that the influx of high-nitrate porewater through High Plains alluvial aquifer silt sediments bearing naturally occurring U(IV) can stimulate a nitrate-reducing microbial community capable of catalyzing the oxidation and mobilization of U into the porewater. Microbial reduction of nitrate yielded nitrite, a reactive intermediate, which was further demonstrated to abiotically mobilize U from the reduced alluvial aquifer sediments. These results indicate that microbial activity, specifically nitrate reduction to nitrite, is one mechanism driving U mobilization from aquifer

Westrop EST 2023 Nitrate stimulated SUPPLEMENTAL.pdf (597 kB)
Groundwater geochemical data; descriptive statistics for XANES linear combination fits; measured geochemical parameters from batch adsorption experiments; upflowcolumn reactor experimental design replicating the sand and silt lithologic interface; ORP, pH, Fe(II), U, and viruses/mL measured from upflow-column reactor effluent; upflow reactor sediment U and Fe; and surface complexation model