Anthropogenically Enhanced Mobilization of Naturally Occurring Uranium Leading to Groundwater Contamination
Earth and Atmospheric Sciences, University of Nebraska-Lincoln, Lincoln, NE, USA
Contamination of groundwater with naturally occurring uranium throughout the United States has been recently reported. Traditionally, increases in carbonate concentrations and alkalinity have been attributed to mobilization of naturally occurring uranium. However, in areas where uranium exists as a reduced solid-phase mineral, elevated uranium concentrations cannot be accounted for by alkalinity alone due to the requirement of oxidation yielding a soluble aqueous species. A recent study demonstrated that uranium mobilization is significantly correlated to the presence of anthropogenic nitrate contamination in the High Plains and Central Valley aquifer systems. These two aquifers are the source of drinking water for 6 million people and are utilized to irrigate 22 million acres of cropland. Nitrate, a common groundwater contaminant has been demonstrated in legacy site studies to stimulate the oxidative dissolution of U(IV) bearing minerals either abiotically or biotically through direct and indirect mechanisms. The objectives of this research are to (i) to determine the rate and extent of abiotic/biotic processes resulting in oxidative dissolution/mobilization U(IV) and; (ii) to develop a spatially derived reactive transport model to predict communities at risk of naturally occurring uranium mobilization. This research will be accomplished through the use of laboratory-based intact anaerobic sediment core studies from sites where uranium mobilization has been identified, and reactive transport modeling utilizing supercomputing capabilities. Our findings will elucidate the microbially mediated link between nitrate and naturally occurring uranium and predict future groundwater contamination in areas where uranium mineral reserves may be potentially utilized where anthropogenic nitrate is present.
AAPG Search and Discovery Article #90199 © 2014 AAPG Foundation 2014 Grants-in-Aid Projects