| Abstract |
Fate of U(IV) solid phases under oxidizing conditions is of great environmental importance. In shallow aquatic sediment, U(V1) was reduced to U(1V) directly by bacteria including Geobacter and Desulfovibrio spp., but not by the aqueous sulfide or iron sulfide minerals produced by sulfate-reducing bacteria. In shallow subsurface sediment nearby the aquatic sediment, uranium was as enriched as economically important deposits and the majority of uranium persisted as U(1V) against reoxidation. The shallow subsurface sediment was colonized by a microbial community actively cycling nitrogen, iron and sulfur. Preservation of U(1V) in oxidizing sediments is attributed to rapid microbial utilization of oxygen, nitrate and Fe(III), which rapidly oxidize U(1V). |