Biogeochemical controls on the corrosion of depleted uranium alloy in subsurface soils.

Military activities have left a legacy of depleted uranium (DU) penetrator waste in the near-surface terrestrial environment. To understand the fate of this DU alloy, the mechanisms and controlling factors of corrosion need to be determined. In this study, field-moist and waterlogged microcosms were used to investigate the effect of redox conditions and soil water content on the corrosion and fate of DU in subsurface soil, and the impact of corroding DU on the soil microbial population. The mechanism of corrosion and the corrosion products formed were highly dependent on the water status of the soil. Under field-moist conditions, DU corroded at a rate of 0.49 +/- 0.06 g cm(-2) y(-1) and the main U input to surrounding soil was large metaschoepite [(UO2)8O2(OH)12 x (H2O)10] particles. However, underwaterlogged conditions the rate of corrosion was significantly slower at 0.01-0.02 g cm(-2) y(-1) and occurred with the release of dissolved species to the surrounding environment. Corrosion ceases under reducing conditions, thus redox conditions are important in determining the persistence of penetrators in the environment. Corroding DU alters the redox conditions in the surrounding environment and both mechanisms of corrosion impact the microbial community.