Uranyl phosphate minerals as long term sink in uranium bioremediation

US Department of Energy nuclear fuel and weapon production has resulted in uranium contaminated soils and groundwater. As the magnitude of this environmental issue requires an in situ remediation strategy, bioreduction of soluble U(VI) to insoluble U(IV) has been investigated. However, site specific conditions prevent the effectiveness of this remediation technique requiring instead a redox independent method. The biomineralization of the water soluble U(VI) species is presented as a remediation alternative, and the role of different organophosphate species and bacterial strains in this process continues to be studied. However, the stability of these uranyl phosphate minerals must also be examined to evaluate their role as long term sinks for uranium. This study seeks to quantify uranyl phosphate stability in environmentally relevant conditions by examining the effect of Na+, Ca2+, SO42-, and HCO3- present in typical subsurface environments, and uranium phosphate biomineralization in the presence of carbonates. The results of the study suggest that the uranyl phosphate species biomineralized by the facultative anaerobe, Rahnella sp.Y9602, isolated from soils at the DOE Oak Ridge Field Research Center (ORFRC) as a model organism, is preferred even in the presence of the competing carbonate species. Furthermore, even in the presence of cations and anions, uranyl phosphate minerals may be exploited as an alternative remediation reservoir.Committee Member/Second Reader: Carrie Shepler; Faculty Mentor: Martial Taillefer