Oxidation of uranium oxide aerosol particles in the near-surface environment [abstract]

Between 1958 and 1984, microscopic particles of depleted uranium (DU) oxide were emitted as an aerosol from a manufacturing plant located in a populated area of Colonie, NY, and deposited in sediments, soils, and interior dusts. During this period, plant workers and nearby residents were exposed to significant amounts of DU through inhalation. This study focuses on a interior dusts and a dated sediment core from a nearby reservoir that contains a detailed historical record of particle deposition. We have identified more than 50 discrete, DU-bearing particles with diameters <1 to 30 μm (mean = 5 μm). Particle morphologies include spheres, irregular shards, and agglomerates of micron- to submicron-size particles. Particle compositions determined by electron microprobe range from 45-100 wt % UO2, with minor Si, Ca, Pb, and Fe. U LIII-edge μ-XANES spectra were compared between DU particles collected from interior dusts (dry) and from sediments (wet). Absorption edge profiles and energies of the dust sample spectra are similar to the U(IV)O2 model compound, indicating a preponderance of U(IV). In contrast, the edge positions of sediment sample particles are shifted to higher energies, suggesting a higher proportion of U(VI) relative to the dust samples. In one case, the absorption edge position of a sediment particle was nearly identical to the U(VI) model compound metaschoepite. These results suggest that U oxidation state and phase relations of these particles are functions of environment (wet vs. dry) and exposure age.