Elucidating Depleted Uranium Geochemistry In Firing Range Soils.

The historical testing of depleted uranium (DU) munitions at a number of military installations within the US has led to environmental build-up (up to 50 metric tons of metallic DU), and release of DU and its degradation products.  After environmental exposure, DU may readily oxidize creating species that have different toxicity and behavioral properties from the source DU.  A series of both fired and unfired DU penetrator rods were buried at different depths in the soil at the Yuma Proving Ground in AZ for 10 years in order to monitor DU/U degradation and speciation under natural conditions.  Rods and the surrounding soils were recently excavated.  Noticeable U mineral “blooms” coated all rod surfaces, and in some cases complete degradation of the DU rods were noted.  A number of liquid and solid- state analytical techniques were used to fully characterize the U in the system.  Synchrotron based-techniques X-ray Fluorescence mapping, X-ray Absorption Spectroscopy and X-ray Diffraction were used to identify elemental associations and DU/U minerals present at the rod surface and surrounding soils.  Data were collected at beamline X27A at the National Synchrotron Light Source at Brookhaven National Laboratory.  Data show that the metallic DU rods oxidized to form a number of U minerals including: Schoepite (UO₂)₈O₂(OH)12^.H₂O), Metaschoepite ((UO₂)₄O(OH)₆·5H₂O), Becquerelite (Ca(UO₂)₆O₄(OH)₆^.8(H₂O)), and Fourmariertite (Pb(UO₂)₄O₃(OH)₄^.4(H₂O)).