Speciation-Dependent Microbial Reduction of Uranium within Iron-Coated Sands

摘要

Transport of uranium within surface and subsurface environments is predicated largely on its redox state. Uranyl reduction may transpire through either biotic (enzymatic) or abiotic pathways; in either case, reduction of U(VI) to U(IV) results in the formation of sparingly soluble UO_2 precipitates. Biological reduction of U(VI), while demonstrated as prolific under both laboratory and field conditions, is influenced by competing electron acceptors (such as nitrate, manganese oxides, or iron oxides) and uranyl speciation. Formation of Ca-UO_2-CO_3 ternary complexes, often the predominate uranyl species in carbonate-bearing soils and sediments, decreases the rate of dissimilatory U(VI) reduction.