Owing to ecosystem and human health consequences,understanding uranium's potential for mobility in environmental settings isimportant.  In anaerobic soils andsediments, oxidized U(VI) may be reduced through biological or chemicalpathways to U(IV), forming sparingly soluble solids.  However, formation of uranyl-calcium-carbonatocomplexes may limit reduction and authogenic UO2 is susceptible toreoxidation.  Determining reactionpathways of uranium that promote solids stable under aerobic and anaerobicconditions is critical for limiting dissolved concentrations and migration ofuranium.  We examined the fate of uraniumincorporated into transforming Fe(hydr)oxides under cyclic oxidizing andreducing conditions.  Uranium in systems containingferrihydrite, 4 mM Ca, 3.8 mM HCO3- and 3 or 10 mMFe(II), that were maintained under reducing conditions for 15d followed by 5dof oxidation for 3 cycles exhibited widely diverging fates.  Uranium EXAFS and XANES analysis revealoxidized uranium both adsorbed on and incorporated in the structure of goethiteand magnetite.

Stability of uranium incorporated into Fe(hydr)oxide structure under fluctuating redox conditions

242nd National Meeting (2011)

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