Uranium

About: Uranium is a research topic. Over the lifetime, 26283 publications have been published within this topic receiving 317689 citations. The topic is also known as: element 92 & U.

Microbial reduction of uranium

Abstract: REDUCTION of the soluble, oxidized form of uranium, U(VI), to insoluble U(IV) is an important mechanism for the immobilization of uranium in aquatic sediments and for the formation of some uranium ores1–10. U(VI) reduction has generally been regarded as an abiological reaction in which sulphide, molecular hydrogen or organic compounds function as the reductant1,2,5,11. Microbial involvement in U(VI) reduction has been considered to be limited to indirect effects, such as microbial metabolism providing the reduced compounds for abiological U(VI) reduction and microbial cell walls providing a surface to stimulate abiological U(VI) reduction1,12,13. We report here, however, that dissimilatory Fe(III)-reducing microorganisms can obtain energy for growth by electron transport to U(VI). This novel form of microbial metabolism can be much faster than commonly cited abiological mechanisms for U(VI) reduction. Not only do these findings expand the known potential terminal electron acceptors for microbial energy transduction, they offer a likely explanation for the deposition of uranium in aquatic sediments and aquifers, and suggest a method for biological remediation of environments contaminated with uranium.

Stimulating the in situ activity of Geobacter species to remove uranium from the groundwater of a uranium-contaminated aquifer.

Abstract: The potential for removing uranium from contaminated groundwater by stimulating the in situ activity of dissimilatory metal-reducing microorganisms was evaluated in a uranium-contaminated aquifer located in Rifle, Colo. Acetate (1 to 3 mM) was injected into the subsurface over a 3-month period via an injection gallery composed of 20 injection wells, which was installed upgradient from a series of 15 monitoring wells. U(VI) concentrations decreased in as little as 9 days after acetate injection was initiated, and within 50 days uranium had declined below the prescribed treatment level of 0.18 μM in some of the monitoring wells. Analysis of 16S ribosomal DNA (rDNA) sequences and phospholipid fatty acid profiles demonstrated that the initial loss of uranium from the groundwater was associated with an enrichment of Geobacter species in the treatment zone. Fe(II) in the groundwater also increased during this period, suggesting that U(VI) reduction was coincident with Fe(III) reduction. As the acetate injection continued over 50 days there was a loss of sulfate from the groundwater and an accumulation of sulfide and the composition of the microbial community changed. Organisms with 16S rDNA sequences most closely related to those of sulfate reducers became predominant, and Geobacter species became a minor component of the community. This apparent switch from Fe(III) reduction to sulfate reduction as the terminal electron accepting process for the oxidation of the injected acetate was associated with an increase in uranium concentration in the groundwater. These results demonstrate that in situ bioremediation of uranium-contaminated groundwater is feasible but suggest that the strategy should be optimized to better maintain long-term activity of Geobacter species.

Uranium-series disequilibrium: applications to earth, marine, and environmental sciences. 2. ed

Abstract: The phenomenon of radioactivity geochemistry of actinides and their daughters uranium-series desequilibrium applications applications in geochronology chemical procedures spectroscopic methods mass spectrometry and applications to uranium-series disequilibrium igneous rocks uranium-series mobilization and surface hydrology ground water the oceanic chemistry of the uranium and thorium series nuclides radionuclides of the uranium and thorium decay series in the estuarine environment carbonate and sulphate precipitates marine sediments and sedimatentation processes uranium-series studies of marine phosphates and carbonates archaeological applications palaeclimatology and palaeoclimate records applications to radioactive waste disposal studies decay-series disequilibria applied to the study of rock-water interactions and geothermal systems applications od dating to denudation chronology and landscape evolution uranium-series disequilibrium in exploration geology applications of lead-210 to sedimentation studies.