The historical testing of depleted uranium (DU) munitions at a number of military installations within the US has led to environmental build-up and release of DU to the environment. After environmental exposure, DU (as U<sup>0</sup>) may readily oxidize creating species that have different toxicity and geochemical properties. A series of both fired and unfired DU penetrator rods were buried at different depths at the Yuma Proving Grounds (YPG) in AZ over 10 years ago in order to monitor DU oxidation and migration under natural soil conditions. Several rods from different depths and the soils surrounding them have been harvested along with “legacy soils” experiencing historical DU firings at YPG. Liquid and solid- state analytical techniques were used to characterize the speciation of U and kinetics of U release in these soils. Synchrotron based-techniques (XRF mapping, X-ray Absorption Spectroscopy and XRD) were used to identify elemental associations and DU minerals present at the rod surface and surrounding soils. Data were collected at beamline X27A at the NSLS. Noticeable DU mineral “blooms” coated all rod surfaces, and in some cases complete oxidation of the metallic rod occurred. Data show that the metallic DU oxidized to form a number of U minerals and confirm that soil constituents (Ba, Pb) influence U mineral formation in these systems. The highest concentrations of DU were found in the soil within 10 cm of the rods, with minimal evidence of U migration past 15 cm of the rod. Extraction studies showed high levels of U release from soils with a sequential extraction scheme.

Chemistry of depleted uranium in military firing range soils

249th National Meeting (2015)

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