Daigle, Ashley R., 1986-2010-08-252010-08-252010-06https://hdl.handle.net/1794/10636xiii, 67 p. : ill. (some col.) A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number.The bedrock aquifer of the Southern Willamerte Basin, Oregon, USA, is contaminated with arsenic at concentrations as high as several ppm. Single-well push-pull tests were conducted to investigate how microbial metabolisms control arsenic occurrence and levels in the aquifer. Test solutions containing ethanol were injected into the aquifer; dissolved gases, groundwater, and sediments were then sampled to monitor the speciation of carbon, iron, sulfur, and arsenic. Ethanol amendment stimulated a series of microbial metabolisms, including arsenate reduction, iron reduction, and sulfate reduction. Arsenate reduction converts arsenate to arsenite; iron reduction produces ferrous iron; sulfate reduction releases sulfide. Arsenite and ferrous iron then combine with sulfide and form arsenic sulfide and iron sulfide minerals. Results of the experiments demonstrate that the interactions among microbial metabolisms and mineral precipitation influenced arsenic contamination in the aquifer. These results shed new light on potential bioremediation strategies in the area.en-USArsenic wastes -- Oregon -- Willamette River WatershedAquifers -- Oregon -- Willamette River WatershedThesis