Depleted uranium (DU) is a by-product of the nuclear fuel industry and is used in anti-tank penetrators due to its high density, self-sharpening and pyrophoric properties. Military activities have left a legacy of DU waste in terrestrial and marine environments and presently there are no clean up procedures in place. In order to understand the fate of this DU, long term (500 days) microcosm experiments simulating key environments have been carried out for the first time to investigate the mechanisms and rates of DU corrosion as a function of the biogeochemical and environmental conditions.