Speciation of Uranium in Seepage Waters of a Mine Tailing Pile Studied by Time-Resolved Laser-Induced Fluorescence Spectroscopy (TRLFS)

Bernhard, Gert; Geipel, Gerhard; Brendler, Vinzenz; Nitsche, H.

doi:10.1524/ract.1996.74.special-issue.87

Cited by 231 publications

(172 citation statements)

References 4 publications

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“…For example, Gudavalli et al (2013) showed that during dissolution of Na-and Ca-autunite, buffered bicarbonate solutions were undersaturated thermodynamically with respect to becquerelite, and uranyl carbonate and Ca-uranyl carbonate complexes were the predominant aqueous species, which were postulated to control mineral dissolution. Uranyl carbonate and alkaline-earth uranyl carbonate complexes are highly soluble and stable species that dominate the uranyl aqueous speciation between pH 7 and 11 (Bernhard et al, 1996;Kalmykov and Choppin, 2000;Bernhard et al, 2001) and also uranyl adsorption onto sediment and soils (Stewart et al, 2010). Indeed, breakthrough of U(VI) was noticeably retarded by sorption to quartz in control columns with low carbonate BPW compared to high carbonate BPW systems (Control 2, Fig.…”

Section: Effect Of Dissolved Carbonate On Dissolution Mechanismmentioning

confidence: 98%

Rates and mechanisms of uranyl oxyhydroxide mineral dissolution

Reinoso-Maset

Steefel

et al. 2017

Geochimica et Cosmochimica Acta

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Section: Effect Of Dissolved Carbonate On Dissolution Mechanismmentioning

confidence: 98%

Rates and mechanisms of uranyl oxyhydroxide mineral dissolution

Reinoso-Maset

Steefel

et al. 2017

Geochimica et Cosmochimica Acta

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“…Inclusion of Ca, however, results in two ternary calcium-uranyl-carbonato species, CaUO 2 (CO 3 ) 3 2-and Ca 2 UO 2 (CO 3 ) 3 , emerging as dominant aqueous species, often accounting for >99% of U(VI) in solution (Bernhard et al, 1996(Bernhard et al, , 2001Kalmykov and Choppin, 2000;Kelly et al, 2003;Dong and Brooks, 2006).…”

Section: +mentioning

confidence: 99%

Influence of Uranyl Speciation and Iron Oxides on Uranium Biogeochemical Redox Reactions

Stewart

Amos

Nico

et al. 2011

Geomicrobiology Journal

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Uranium is a pollutant of concern to both human and ecosystem health. Uranium's redox state often dictates its partitioning between the aqueous-and solid-phases, and thus controls its dissolved concentration and, coupled with groundwater flow, its migration within the environment. In anaerobic environments, the more oxidized and mobile form of uranium (UO 2 2+ and associated species) may be reduced, directly or indirectly, by microorganisms to U(IV) with subsequent precipitation of UO 2 . However, various factors within soils and sediments may limit biological reduction of U(VI), inclusive of alterations in U(VI) speciation and competitive electron acceptors. Here we elucidate the impact of U(VI) speciation on the extent and rate of reduction with specific emphasis on speciation changes induced by dissolved Ca, and we examine the impact of Fe(III) (hydr)oxides (ferrihydrite, goethite and hematite) varying in free energies of formation on U reduction. The amount of uranium removed from solution during 100 h of incubation with S. putrefaciens was 77% with no Ca or ferrihydrite present but only 24% (with ferrihydrite) and 14% (no ferrihydrite) were removed for systems with 0.8 mM Ca.Imparting an important criterion on uranium reduction, goethite and hematite decrease the dissolved concentration of calcium through adsorption and thus tend to diminish the effect of calcium on uranium reduction. Dissimilatory reduction of Fe(III) and U(VI) can proceed through different enzyme pathways, even within a single organism, thus providing a potential second means by which Fe(III) bearing minerals may impact U(VI) reduction. We quantify rate coefficients for simultaneous dissimilatory reduction of Fe(III) and U(VI) in systems varying in Ca concentration (0 to 0.8 mM), and using a mathematical construct implemented with the reactive transport code MIN3P, we reveal the predominant influence of uranyl speciation, 2 specifically the formation of uranyl-calcium-carbonato complexes, and ferrihydrite on the rate and extent of uranium reduction in complex geochemical systems.3

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“…One drawback of TRLFS is that fluorescence intensity decreases with increasing pH (from pH 5.5) and ionic strength at low U concentrations (<30 µg l -1 ). The determination of higher uranyl carbonate species (UO 2 [CO 3 ] 2 2-, UO 2 [CO 3 ] 3 4-), for example, is difficult at pH 8.5 [40,41]. Overall, TRLFS is not suitable at present for determining U speciation in freshwater at high pH or estuarine and seawater.…”

Section: Watermentioning

confidence: 99%

Uranium Speciation and Bioavailability in Aquatic Systems: An Overview

Markich

2002

The Scientific World JOURNAL

203

142

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The speciation of uranium (U) in relation to its bioavailability is reviewed for surface waters (fresh-and seawater) and their sediments. A summary of available analytical and modeling techniques for determining U speciation is also presented. U(VI) is the major form of U in oxic surface waters, while U(IV) is the major form in anoxic waters. The bioavailability of U (i.e., its ability to bind to or traverse the cell surface of an organism) is dependent on its speciation, or physicochemical form. U occurs in surface waters in a variety of physicochemical forms, including the free metal ion (U 4+ or UO 2 2+ ) and complexes with inorganic ligands (e.g., uranyl carbonate or uranyl phosphate), and humic substances (HS) (e.g., uranyl fulvate) in dissolved, colloidal, and/or particulate forms. Although the relationship between U speciation and bioavailability is complex, there is reasonable evidence to indicate that UO 2 2+ and UO 2 OH + are the major forms of U(VI) available to organisms, rather than U in strong complexes (e.g., uranyl fulvate) or adsorbed to colloidal and/or particulate matter. U(VI) complexes with inorganic ligands (e.g., carbonate or phosphate) and HS apparently reduce the bioavailability of U by reducing the activity of UO 2 2+ and UO 2 OH + . The majority of studies have used the results from thermodynamic speciation modeling to support these conclusions. Time-resolved laser-induced fluorescence spectroscopy is the only analytical technique able to directly determine specific U species, but is limited in use to freshwaters of low pH and ionic strength. Nearly all of the available information relating the speciation of U to its bioavailability has been derived using simple, chemically defined experimental freshwaters, rather than natural waters. No data are available for estuarine or seawater. Furthermore, there are no available data on the relationship between U speciation and bioavailability in sediments. An understanding of this relationship has been hindered due to the lack of direct quantitative U speciation techniques for particulate phases. More robust analytical techniques for determining the speciation of U in natural surface waters are needed before the relationship between U speciation and bioavailability can be clarified.

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Speciation of Uranium in Seepage Waters of a Mine Tailing Pile Studied by Time-Resolved Laser-Induced Fluorescence Spectroscopy (TRLFS)

Cited by 231 publications

References 4 publications

Rates and mechanisms of uranyl oxyhydroxide mineral dissolution

Rates and mechanisms of uranyl oxyhydroxide mineral dissolution

Influence of Uranyl Speciation and Iron Oxides on Uranium Biogeochemical Redox Reactions

Uranium Speciation and Bioavailability in Aquatic Systems: An Overview

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