Understanding the molecular-scale speciation andreactivity of reduced U(IV) species in subsurface environments is crucial to optimizingin situ bioremediation strategies. Recentstudies have shown that, in addition to UO2, non-crystalline productsof U(VI) reduction can also form. This presentation will focus on the reactivityof biogenic and chemogenic UO2 and non-crystalline forms of U(IV) underchemical extractions targeting U(IV) fractions that are water soluble, ionexchangeable, amenable to complexation by a ligand, or oxidizable. X-rayabsorption spectroscopy was employed to determine differences in U speciationfor solid samples recovered from various chemical extractions. Negligible U concentrationswere extracted from experiments targeting water soluble and ion exchangeablefractions. Less than 5% of the total U was amenable to complexation. Non-crystallineforms of U(IV) were more susceptible to oxidation than either form of UO2.These results suggest that non-crystalline forms of U(IV) are less stable thanuraninite in subsurface environments.

Use of chemical extractions to evaluate the reactivity of U(IV) species

245th National Meeting (2013)

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