The stability of microbially reduced U(IV); impact of residual electron donor and sediment ageing

Newsome, Laura; Morris, Katherine; Shaw, Samuel; Trivedi, Divyesh; Lloyd, Jonathan R.

doi:10.1016/j.chemgeo.2015.05.016

Cited by 46 publications

(61 citation statements)

References 65 publications

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“…These results indicate complete oxidation of mononuclear U(IV) (Figure 1), except for sample C2-25 cm in which 17 % of mononuclear U(IV) persisted, which is consistent with the reported higher sensitivity of mononuclear species to redox change than crystalline U(IV) species [15][16][17][18]. In addition, except in sample C2-25 cm, 30-45 % of the U(IV)-phosphate minerals oxidized, likely into U(VI)-mononuclear species that were accounted by an increase of the U(VI)-biosorbed component in the LCF.…”

Section: Effect Of Oxic Incubationssupporting

confidence: 90%

“…However, the long-term fate of U in wetlands remains unclear, especially when they exhibit intermittent oxidizing conditions due to water-table fluctuations [10]. Indeed, non-crystalline U species that have been identified as major U species in wetlands, such as mononuclear U(VI) and U(IV) complexes bound to organic matter [10,[11][12][13], are known to be potentially mobile under both oxic [14][15][16][17] and anoxic conditions [7,18]. In addition, U(IV)-phosphate minerals may also play an important role in U retention in mining-contaminated wetlands.…”

Section: Introductionmentioning

confidence: 99%

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Experimental redox transformations of uranium phosphate minerals and mononuclear species in a contaminated wetland

Stetten

Lefebvre

Pape

et al. 2020

Journal of Hazardous Materials

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Reducing conditions and high organic carbon content make wetlands favorable to uranium (U) sequestration. However, such environments are subjected to water-table fluctuations that could impact the redox behavior of U and its mobility. Our previous study on U speciation in a highly contaminated wetland has suggested a major role of water-table redox fluctuations in the redistribution of U from U(IV)-phosphate minerals to organic U(VI) and U(IV) mononuclear species. Here, we investigate the mechanisms of these putative processes by mimicking drying or flooding periods via laboratory incubations of wetland samples. LCF-XANES and EXAFS analyses show the total oxidation/reduction of U(IV)/U(VI)mononuclear species after 20 days of oxic/anoxic incubation, whereas U-phosphate minerals appear to be partly oxidized/reduced. SEM-EDXS combined with µ-XRF and µ-XANES analyses suggest that autunite Ca(UO 2) 2 (PO 4) 2 • H 2 O is reduced into lermontovite U(PO 4 OH •H 2 O, whereas oxidized ningyoite CaU(PO 4) 2 •2H 2 O is locally dissolved. The release of U from this latter process is observed to be limited by U(VI) adsorption to the surrounding soil matrix and further re-reduction into mononuclear U(IV) upon anoxic cycling. Analysis of incubation waters show, however, that dissolved organic carbon enhances U solubilization even under anoxic conditions. This study brings important information that help to assess the long-term stability of U in seasonally saturated organicrich contaminated environments.

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Section: Effect Of Oxic Incubationssupporting

confidence: 90%

Section: Introductionmentioning

confidence: 99%

Experimental redox transformations of uranium phosphate minerals and mononuclear species in a contaminated wetland

Stetten

Lefebvre

Pape

et al. 2020

Journal of Hazardous Materials

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“…The sorption of uranium complexes on iron hydroxides is significantly reduced in the presence of organic matter and/or competing cations, such as Ca 2+ and Mg 2+ [31]. Other studies have shown that the concentration of U(VI) in the aqueous phase drastically decreases during bacterial processes because of the formation of insoluble U(IV) compounds [47,48]. In addition, humic substances (HS), including fulvic acid and humic acid, have a strong complexing ability for 238 U of all types of organic matter.…”

Section: Response Relationship Of 238 U Concentration To Organic Mattmentioning

confidence: 99%

Distribution Characteristics and Influencing Factors of Uranium Isotopes in Saline Lake Waters in the Northeast of Qaidam Basin

Zhao

Zhang

et al. 2020

Minerals

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Four saline lakes in the northeast of Qaidam Basin were selected to explore the distribution characteristics and influencing factors of uranium isotopes in lake waters with high evaporation background. The 238U concentration and the activity ratios of 234U/238U ([234U/238U]AR) showed that there was no significant change in the same lake, but there was a certain degree of difference in the distribution between different lakes. We found that aqueous 238U concentration within a certain range increased with an increase in TDS (total dissolved solid) and salinity, as was also the case with pH. As in natural waters, the pH affects the speciation of 238U, but TDS and salinity affect the adsorption process of aqueous 238U. Further, the replenishment of water will also affect the uranium isotope concentration for lakes, but it is not the main influencing factor for saline lakes. Therefore, we suggest that pH is the dominant factor affecting changes in aqueous 238U concentration of the sampled saline lakes. The [234U/238U]AR in these saline lakes are closely related to the input water and the associated water–rock interactions involving sediments, atmosphere dust, and organic material, etc. during the evolution stage, metamorphous degree, and hydrochemistry of the saline lakes. Lake water samples collected in the maximum and minimum discharge water period, were used to evaluate the seasonal distribution characteristics of aqueous 238U, and we found that 238U concentration did not show an evident change with the seasons in these saline lakes. If the 238U concentration and [234U/238U]AR can remain consistent during a period of time, then the sediment ages and/or sedimentation rates could be determined by lake sediment and/or biogenic carbonate in future, thus allowing for the accurate reconstruction of the paleoclimate and paleoenvironment.

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“…The curve named "remaining oxygen" shows the remaining oxygen concentration of O after subtracting oxygen per uranium dioxide, phosphate group and possible silicon oxide. The lines named "MnAc 2 tetra", "MnAc 2 dihydr", "MnAc 2 anhydr" and "Mn hydroxide" show the oxygen concentration required to satisfy the corresponding stoichiometric formulas of Mn( 2 and Mn(OH) 2 . The intersection of these lines with the curve of "remaining oxygen" makes it possible to estimate the thickness of the sample.…”

Section: Imaging and Composition Of The Biogenic Mineralsmentioning

confidence: 99%

“…The basis of such treatment is the transformation of highly soluble U(VI) salts to sparingly soluble uranium (IV) oxide, uraninite. However, the strategy can be successful if the biogenic uraninite remains immobilized and does not easily oxidize [2]. Therefore, the structure and morphology of biogenic minerals, as well the impurity effect, have been and remain a subject of close attention with a view to addressing problems in fundamental and applied science and in technology.…”

Section: Introductionmentioning

confidence: 99%

Electron microscopy of biogenic minerals: structure and sizes of uranium dioxide nanoparticles with Mn2+ impurities

Suvorova¹

2019

Nanosystems: Phys. Chem. Math.

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Methodological aspects of the extraction of structural and chemical information from transmission electron microscopy (TEM) of uranium dioxide (UO 2 ) biogenic nanoparticles are presented. Nanoparticles were formed via the bacterial reduction of water-soluble uranyl acetate with U (VI) in the presence of Mn 2+ ions and cultures Shewanella oneidensis MR-1 in the medium. The particles of 1.2 -3.5 nm in diameter and particle agglomerations were visualized in conventional TEM, high resolution TEM, scanning TEM modes. Their phase and chemical composition were investigated with electron diffraction, X-ray energy dispersive spectrometry and electron energy loss spectroscopy with high spatial resolution. Maintenance of the element balance helped to find the composition of the mixture of UO 2 and Mn acetates. The interpretation of TEM data and modeling allowed to propose the mechanism for the suppression of UO 2 particle growth and higher resistance to dissolution of smaller UO 2 particles with adsorbed Mn acetate compared to the larger pure particles.

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The stability of microbially reduced U(IV); impact of residual electron donor and sediment ageing

Cited by 46 publications

References 65 publications

Experimental redox transformations of uranium phosphate minerals and mononuclear species in a contaminated wetland

Experimental redox transformations of uranium phosphate minerals and mononuclear species in a contaminated wetland

Distribution Characteristics and Influencing Factors of Uranium Isotopes in Saline Lake Waters in the Northeast of Qaidam Basin

Electron microscopy of biogenic minerals: structure and sizes of uranium dioxide nanoparticles with Mn2+ impurities

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