Rapid Deployment of Engineered Solutions for Environmental Problems at Hanford

The investigation targets uranium (U) contamination in the vadose zone (VZ) of the 200 Area that may affect potential discharges to the Columbia River via groundwater migration. Injection of reactive gases such as NH3 is an innovative technology that targets U contamination in the VZ to reduce the potential for radionuclides mobility in subsurface. The alkaline conditions can greatly enhance the solubility of most Al- and Si-containing minerals by many orders of magnitude. The following decrease in pH will cause uranium co-precipitation during the recrystallization of minerals. Microbial activities in many environmental systems are additional layers of complexity that affect U(VI) mobility in the subsurface. In nature, a variety of bacteria may enhance the mobility of heavy metals or radionuclides by dissolution and desorption due to the secretion of protons and various ligands. This project investigates the bacterial effect on U(VI) release from the autunite mineral (Ca[(UO2)(PO4)]2•3H2O) to provide a more comprehensive understanding of the important microbiological processes affecting autunite stability and uranium mobility within subsurface bicarbonate-bearing environments.