Spectral Induced Polarization Response of Biofilm Formation in Hanford Vadose Zone Sediment

As a result of the U.S. Nuclear weapons program during the second world war and the cold war, there now exists a significant amount of uranium contamination at the U.S. Department of Energy Hanford site located in Washington state. In-situ immobilization of mobile uranium via injections of a soluble sodium tripolyphosphate amendment may prove effective in the formation of insoluble uranyl phosphate mineral, autunite. However, the injected polyphosphate undergoes hydrolysis in aqueous solutions to form orthophosphate, which serves as a readily available nutrient for the various microorganisms in the sediment. Sediment-filled column experiments conducted under saturated oxygen restricted conditions using geophysical Spectral Induced Polarization technique have shown the impact of microbes on the dissolution of autunite, a calcium uranyl phosphate mineral. Spectral Induced Polarization may be an effective way to track changes indicative of bacterial activities on the surrounding environment. This method can be a cost-effective alternative to the drilling of boreholes at a field scale.