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Sahoo PK, Virk HS, Powell MA, Kumar R, Pattanaik JK, Salomão GN, Mittal S, Chouhan L, Nandabalan YK, Tiwari RP. Meta-analysis of uranium contamination in groundwater of the alluvial plains of Punjab, northwest India: Status, health risk, and hydrogeochemical processes. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 807:151753. [PMID: 34822893 DOI: 10.1016/j.scitotenv.2021.151753] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Revised: 11/07/2021] [Accepted: 11/13/2021] [Indexed: 06/13/2023]
Abstract
Despite numerous studies, there are many knowledge gaps in our understanding of uranium (U) contamination in the alluvial aquifers of Punjab, India. In this study, a large hydrogeochemical dataset was compiled to better understand the major factors controlling the mobility and enrichment of uranium (U) in this groundwater system. The results showed that shallow groundwaters (<60 m) are more contaminated with U than from deeper depths (>60 m). This effect was predominant in the Southwest districts of the Malwa, facing significant risk due to chemical toxicity of U. Groundwaters are mostly oxidizing and alkaline (median pH: 7.25 to 7.33) in nature. Spearman correlation analysis showed that U concentrations are more closely related to total dissolved solids (TDS), salinity, Na, K, HCO3-, NO3- Cl-, and F- in shallow water than deep water, but TDS and salinity remained highly correlated (U-TDS: ρ = 0.5 to 0.6; U-salinity: ρ = 0.5). This correlation suggests that the salt effect due to high competition between ions is the principal cause of U mobilization. This effect is evident when the U level increased with increasing mixed water species (Na-Cl, Mg-Cl, and Na-HCO3). Speciation data showed that the most dominant U species are Ca2UO2(CO3)2- and CaUO2(CO3)3-, which are responsible for the U mobility. Based on the field parameters, TDS along with pH and oxidation-reduction potential (ORP) were better fitted to U concentration above the WHO guideline value (30 μg.L-1), thus this combination could be used as a quick indicator of U contamination. The strong positive correlation of U with F- (ρ = 0.5) in shallow waters indicates that their primary source is geogenic, while anthropogenic factors such as canal irrigation, groundwater table decline, and use of agrochemicals (mainly nitrate fertilizers) as well as climate-related factors i.e., high evaporation under arid/semi-arid climatic conditions, which result in higher redox and TDS/salinity levels, may greatly affect enrichment of U. The geochemical rationale of this study will provide Science-based-policy implications for U health risk assessment in this region and further extrapolate these findings to other arid/semi-arid areas worldwide.
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Affiliation(s)
- Prafulla Kumar Sahoo
- Department of Environmental Science and Technology, Central University of Punjab, V.P.O. Ghudda, 151401 Bathinda, India; Instituto Tecnológico Vale (ITV), Rua Boaventura da Silva, 955, Belém 66055-090, PA, Brazil.
| | | | - Mike A Powell
- Department of Renewable Resources, University of Alberta, Edmonton, AB T6G 2R3, Canada
| | - Ravishankar Kumar
- Department of Environmental Science and Technology, Central University of Punjab, V.P.O. Ghudda, 151401 Bathinda, India
| | | | | | - Sunil Mittal
- Department of Environmental Science and Technology, Central University of Punjab, V.P.O. Ghudda, 151401 Bathinda, India
| | - Lokesh Chouhan
- Department of Environmental Science and Technology, Central University of Punjab, V.P.O. Ghudda, 151401 Bathinda, India
| | | | - Raghavendra Prasad Tiwari
- Department of Environmental Science and Technology, Central University of Punjab, V.P.O. Ghudda, 151401 Bathinda, India
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Su J, Cheisson T, McSkimming A, Goodwin CAP, DiMucci IM, Albrecht-Schönzart T, Scott BL, Batista ER, Gaunt AJ, Kozimor SA, Yang P, Schelter EJ. Complexation and redox chemistry of neptunium, plutonium and americium with a hydroxylaminato ligand. Chem Sci 2021; 12:13343-13359. [PMID: 34777753 PMCID: PMC8528073 DOI: 10.1039/d1sc03905a] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2021] [Accepted: 09/03/2021] [Indexed: 11/25/2022] Open
Abstract
There is significant interest in ligands that can stabilize actinide ions in oxidation states that can be exploited to chemically differentiate 5f and 4f elements. Applications range from developing large-scale actinide separation strategies for nuclear industry processing to carrying out analytical studies that support environmental monitoring and remediation efforts. Here, we report syntheses and characterization of Np(iv), Pu(iv) and Am(iii) complexes with N-tert-butyl-N-(pyridin-2-yl)hydroxylaminato, [2-(tBuNO)py]−(interchangeable hereafter with [(tBuNO)py]−), a ligand which was previously found to impart remarkable stability to cerium in the +4 oxidation state. An[(tBuNO)py]4 (An = Pu, 1; Np, 2) have been synthesized, characterized by X-ray diffraction, X-ray absorption, 1H NMR and UV-vis-NIR spectroscopies, and cyclic voltammetry, along with computational modeling and analysis. In the case of Pu, oxidation of Pu(iii) to Pu(iv) was observed upon complexation with the [(tBuNO)py]− ligand. The Pu complex 1 and Np complex 2 were also isolated directly from Pu(iv) and Np(iv) precursors. Electrochemical measurements indicate that a Pu(iii) species can be accessed upon one-electron reduction of 1 with a large negative reduction potential (E1/2 = −2.26 V vs. Fc+/0). Applying oxidation potentials to 1 and 2 resulted in ligand-centered electron transfer reactions, which is different from the previously reported redox chemistry of UIV[(tBuNO)py]4 that revealed a stable U(v) product. Treatment of an anhydrous Am(iii) precursor with the [(tBuNO)py]− ligand did not result in oxidation to Am(iv). Instead, the dimeric complex [AmIII(μ2-(tBuNO)py)((tBuNO)py)2]2 (3) was isolated. Complex 3 is a rare example of a structurally characterized non-aqueous Am-containing molecular complex prepared using inert atmosphere techniques. Predicted redox potentials from density functional theory calculations show a trivalent accessibility trend of U(iii) < Np(iii) < Pu(iii) and that the higher oxidation states of actinides (i.e., +5 for Np and Pu and +4 for Am) are not stabilized by [2-(tBuNO)py]−, in good agreement with experimental observations. The coordination modes and electronic properties of a strongly coordinating hydroxylaminato ligand with Np, Pu and Am were investigated.Complexes were characterized by a range of experimental and computational techniques.![]()
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Affiliation(s)
- Jing Su
- Theoretical Division, Los Alamos National Laboratory Los Alamos New Mexico 87545 USA
| | - Thibault Cheisson
- P. Roy and Diana T. Vagelos Laboratories, Department of Chemistry, University of Pennsylvania 231 S 34th St. Philadelphia Pennsylvania 19104 USA
| | - Alex McSkimming
- P. Roy and Diana T. Vagelos Laboratories, Department of Chemistry, University of Pennsylvania 231 S 34th St. Philadelphia Pennsylvania 19104 USA
| | - Conrad A P Goodwin
- Chemistry Division, Los Alamos National Laboratory Los Alamos New Mexico 87545 USA
| | - Ida M DiMucci
- Chemistry Division, Los Alamos National Laboratory Los Alamos New Mexico 87545 USA
| | - Thomas Albrecht-Schönzart
- Department of Chemistry and Biochemistry, Florida State University 95 Chieftan Way Tallahassee Florida 32306 USA
| | - Brian L Scott
- Materials and Physics Applications Division, Los Alamos National Laboratory Los Alamos New Mexico 87545 USA
| | - Enrique R Batista
- Theoretical Division, Los Alamos National Laboratory Los Alamos New Mexico 87545 USA
| | - Andrew J Gaunt
- Chemistry Division, Los Alamos National Laboratory Los Alamos New Mexico 87545 USA
| | - Stosh A Kozimor
- Chemistry Division, Los Alamos National Laboratory Los Alamos New Mexico 87545 USA
| | - Ping Yang
- Theoretical Division, Los Alamos National Laboratory Los Alamos New Mexico 87545 USA
| | - Eric J Schelter
- P. Roy and Diana T. Vagelos Laboratories, Department of Chemistry, University of Pennsylvania 231 S 34th St. Philadelphia Pennsylvania 19104 USA
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3
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Zhang L, Chen Y, Xia Q, Kemner KM, Shen Y, O'Loughlin EJ, Pan Z, Wang Q, Huang Y, Dong H, Boyanov MI. Combined Effects of Fe(III)-Bearing Clay Minerals and Organic Ligands on U(VI) Bioreduction and U(IV) Speciation. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2021; 55:5929-5938. [PMID: 33822593 DOI: 10.1021/acs.est.0c08645] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Reduction of U(VI) to U(IV) drastically reduces its solubility and has been proposed as a method for remediation of uranium contamination. However, much is still unknown about the kinetics, mechanisms, and products of U(VI) bioreduction in complex systems. In this study, U(VI) bioreduction experiments were conducted with Shewanella putrefaciens strain CN32 in the presence of clay minerals and two organic ligands: citrate and EDTA. In reactors with U and Fe(III)-clay minerals, the rate of U(VI) bioreduction was enhanced due to the presence of ligands, likely because soluble Fe3+- and Fe2+-ligand complexes served as electron shuttles. In the presence of citrate, bioreduced U(IV) formed a soluble U(IV)-citrate complex in experiments with either Fe-rich or Fe-poor clay mineral. In the presence of EDTA, U(IV) occurred as a soluble U(IV)-EDTA complex in Fe-poor montmorillonite experiments. However, U(IV) remained associated with the solid phase in Fe-rich nontronite experiments through the formation of a ternary U(IV)-EDTA-surface complex, as suggested by the EXAFS analysis. Our study indicates that organic ligands and Fe(III)-bearing clays can significantly affect the microbial reduction of U(VI) and the stability of the resulting U(IV) phase.
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Affiliation(s)
- Limin Zhang
- State Key Laboratory of Biology and Environmental Geology, China University of Geosciences, Beijing 100083, China
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China
| | - Yu Chen
- State Key Laboratory of Biology and Environmental Geology, China University of Geosciences, Beijing 100083, China
| | - Qingyin Xia
- State Key Laboratory of Biology and Environmental Geology, China University of Geosciences, Beijing 100083, China
| | - Kenneth M Kemner
- Biosciences Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Yanghao Shen
- Biosciences Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Edward J O'Loughlin
- Biosciences Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Zezhen Pan
- Environmental Microbiology Laboratory Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
| | - Qihuang Wang
- Department of Environmental Science and Engineering, Fudan University, Shanghai 200438, China
| | - Ying Huang
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China
| | - Hailiang Dong
- State Key Laboratory of Biology and Environmental Geology, China University of Geosciences, Beijing 100083, China
| | - Maxim I Boyanov
- Biosciences Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
- Bulgarian Academy of Sciences, Institute of Chemical Engineering, Sofia 1113, Bulgaria
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El-Sharkawy AM. 234U/238U activity ratios in groundwaters from two aquifers in Saudi Arabia, and correlation with water chemistry. JOURNAL OF RADIATION RESEARCH AND APPLIED SCIENCES 2019. [DOI: 10.1016/j.jrras.2018.07.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Affiliation(s)
- Ahmed M. El-Sharkawy
- Nuclear and Radiological Regulatory Authority, P.O.Box 7551, Cairo, 11762, Egypt
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Yan S, Boyanov MI, Mishra B, Kemner KM, O'Loughlin EJ. U(VI) Reduction by Biogenic and Abiotic Hydroxycarbonate Green Rusts: Impacts on U(IV) Speciation and Stability Over Time. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2018; 52:4601-4609. [PMID: 29630355 DOI: 10.1021/acs.est.7b06405] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Green rusts (GRs) are redox active FeII-FeIII minerals that form in the environment via various biotic and abiotic processes. Although both biogenic (BioGR) and abiotic (ChemGR) GRs have been shown to reduce UVI, the dynamics of the transformations and the speciation and stability of the resulting UIV phases are poorly understood. We used carbonate extraction and XAFS spectroscopy to investigate the products of UVI reduction by BioGR and ChemGR. The results show that both GRs can rapidly remove UVI from synthetic groundwater via reduction to UIV. The initial products in the ChemGR system are solids-associated UIV-carbonate complexes that gradually transform to nanocrystalline uraninite over time, leading to a decrease in the proportion of carbonate-extractable U from ∼95% to ∼10%. In contrast, solid-phase UIV atoms in the BioGR system remain relatively extractable, nonuraninite UIV species over the same reaction period. The presence of calcium and carbonate in groundwater significantly increase the extractability of UIV in the BioGR system. These data provide new insights into the transformations of U under anoxic conditions in groundwater that contains calcium and carbonate, and have major implications for predicting uranium stability within redox dynamic environments and designing approaches for the remediation of uranium-contaminated groundwater.
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Affiliation(s)
- Sen Yan
- School of Earth Sciences , China University of Geosciences , Wuhan , 430074 , China
- Biosciences Division , Argonne National Laboratory , Argonne , Illinois 60439 , United States
| | - Maxim I Boyanov
- Biosciences Division , Argonne National Laboratory , Argonne , Illinois 60439 , United States
- Institute of Chemical Engineering , Bulgarian Academy of Sciences , Sofia , 1113 , Bulgaria
| | - Bhoopesh Mishra
- Biosciences Division , Argonne National Laboratory , Argonne , Illinois 60439 , United States
- School of Chemical and Process Engineering , University of Leeds , Leeds , LS2 9JT , U.K
| | - Kenneth M Kemner
- Biosciences Division , Argonne National Laboratory , Argonne , Illinois 60439 , United States
| | - Edward J O'Loughlin
- Biosciences Division , Argonne National Laboratory , Argonne , Illinois 60439 , United States
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6
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Fan D, Lan Y, Tratnyek PG, Johnson RL, Filip J, O'Carroll DM, Nunez Garcia A, Agrawal A. Sulfidation of Iron-Based Materials: A Review of Processes and Implications for Water Treatment and Remediation. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2017; 51:13070-13085. [PMID: 29035566 DOI: 10.1021/acs.est.7b04177] [Citation(s) in RCA: 192] [Impact Index Per Article: 27.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Iron-based materials used in water treatment and groundwater remediation-especially micro- and nanosized zerovalent iron (nZVI)-can be more effective when modified with lower-valent forms of sulfur (i.e., "sulfidated"). Controlled sulfidation for this purpose (using sulfide, dithionite, etc.) is the main topic of this review, but insights are derived by comparison with related and comparatively well-characterized processes such as corrosion of iron in sulfidic waters and abiotic natural attenuation by iron sulfide minerals. Material characterization shows that varying sulfidation protocols (e.g., concerted or sequential) and key operational variables (e.g., S/Fe ratio and sulfidation duration) result in materials with structures and morphologies ranging from core-shell to multiphase. A meta-analysis of available kinetic data for dechlorination under anoxic conditions, shows that sulfidation usually increases dechlorination rates, and simultaneously hydrogen production is suppressed. Therefore, sulfidation can greatly improve the efficiency of utilization of reducing equivalents for contaminant removal. This benefit is most likely due to inhibited corrosion as a result of sulfidation. Sulfidation may also favor desirable pathways of contaminant removal, such as (i) dechlorination by reductive elimination rather than hydrogenolysis and (ii) sequestration of metals as sulfides that could be resistant to reoxidation. Under oxic conditions, sulfidation is shown to enhance heterogeneous catalytic oxidation of contaminants. These net effects of sulfidation on contaminant removal by iron-based materials may substantially improve their practical utility for water treatment and remediation of contaminated groundwater.
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Affiliation(s)
- Dimin Fan
- Oak Ridge Institute for Science and Education (ORISE) Fellow, Office of Superfund Remediation and Technology Innovation, U.S. Environmental Protection Agency, 2777 Crystal Drive, Arlington, Virginia 22202, United States
| | - Ying Lan
- OHSU-PSU School of Public Health, Oregon Health & Science University , 3181 SW Sam Jackson Park Road, Portland, Oregon 97239, United States
| | - Paul G Tratnyek
- OHSU-PSU School of Public Health, Oregon Health & Science University , 3181 SW Sam Jackson Park Road, Portland, Oregon 97239, United States
| | - Richard L Johnson
- OHSU-PSU School of Public Health, Oregon Health & Science University , 3181 SW Sam Jackson Park Road, Portland, Oregon 97239, United States
| | - Jan Filip
- Regional Centre of Advanced Technologies and Materials, Palacký University Olomouc , Šlechtitelů 27, CZ-78371 Olomouc, Czech Republic
| | - Denis M O'Carroll
- School of Civil and Environmental Engineering, Connected Water Initiative, University of New South Wales , Manly Vale, New South Wales 2093, Australia
| | - Ariel Nunez Garcia
- Department of Civil and Environmental Engineering, Western University , 1151 Richmond St., London, Ontario Canada
| | - Abinash Agrawal
- Department of Earth and Environmental Sciences, Wright State University, Wright State University , 3640 Colonel Glenn Highway, Dayton, Ohio 45435, United States
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7
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Enhanced uranium immobilization and reduction by Geobacter sulfurreducens biofilms. Appl Environ Microbiol 2014; 80:6638-46. [PMID: 25128347 DOI: 10.1128/aem.02289-14] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Biofilms formed by dissimilatory metal reducers are of interest to develop permeable biobarriers for the immobilization of soluble contaminants such as uranium. Here we show that biofilms of the model uranium-reducing bacterium Geobacter sulfurreducens immobilized substantially more U(VI) than planktonic cells and did so for longer periods of time, reductively precipitating it to a mononuclear U(IV) phase involving carbon ligands. The biofilms also tolerated high and otherwise toxic concentrations (up to 5 mM) of uranium, consistent with a respiratory strategy that also protected the cells from uranium toxicity. The enhanced ability of the biofilms to immobilize uranium correlated only partially with the biofilm biomass and thickness and depended greatly on the area of the biofilm exposed to the soluble contaminant. In contrast, uranium reduction depended on the expression of Geobacter conductive pili and, to a lesser extent, on the presence of the c cytochrome OmcZ in the biofilm matrix. The results support a model in which the electroactive biofilm matrix immobilizes and reduces the uranium in the top stratum. This mechanism prevents the permeation and mineralization of uranium in the cell envelope, thereby preserving essential cellular functions and enhancing the catalytic capacity of Geobacter cells to reduce uranium. Hence, the biofilms provide cells with a physically and chemically protected environment for the sustained immobilization and reduction of uranium that is of interest for the development of improved strategies for the in situ bioremediation of environments impacted by uranium contamination.
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Latta DE, Mishra B, Cook RE, Kemner KM, Boyanov MI. Stable U(IV) complexes form at high-affinity mineral surface sites. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2014; 48:1683-91. [PMID: 24404905 DOI: 10.1021/es4047389] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Uranium (U) poses a significant contamination hazard to soils, sediments, and groundwater due to its extensive use for energy production. Despite advances in modeling the risks of this toxic and radioactive element, lack of information about the mechanisms controlling U transport hinders further improvements, particularly in reducing environments where U(IV) predominates. Here we establish that mineral surfaces can stabilize the majority of U as adsorbed U(IV) species following reduction of U(VI). Using X-ray absorption spectroscopy and electron imaging analysis, we find that at low surface loading, U(IV) forms inner-sphere complexes with two metal oxides, TiO2 (rutile) and Fe3O4 (magnetite) (at <1.3 U nm(-2) and <0.037 U nm(-2), respectively). The uraninite (UO2) form of U(IV) predominates only at higher surface loading. U(IV)-TiO2 complexes remain stable for at least 12 months, and U(IV)-Fe3O4 complexes remain stable for at least 4 months, under anoxic conditions. Adsorbed U(IV) results from U(VI) reduction by Fe(II) or by the reduced electron shuttle AH2QDS, suggesting that both abiotic and biotic reduction pathways can produce stable U(IV)-mineral complexes in the subsurface. The observed control of high-affinity mineral surface sites on U(IV) speciation helps explain the presence of nonuraninite U(IV) in sediments and has important implications for U transport modeling.
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Affiliation(s)
- Drew E Latta
- Biosciences Division, Argonne National Laboratory , Argonne, Illinois 60439, United States
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9
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Rui X, Kwon MJ, O'Loughlin EJ, Dunham-Cheatham S, Fein JB, Bunker B, Kemner KM, Boyanov MI. Bioreduction of hydrogen uranyl phosphate: mechanisms and U(IV) products. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2013; 47:5668-5678. [PMID: 23634690 DOI: 10.1021/es305258p] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
The mobility of uranium (U) in subsurface environments is controlled by interrelated adsorption, redox, and precipitation reactions. Previous work demonstrated the formation of nanometer-sized hydrogen uranyl phosphate (abbreviated as HUP) crystals on the cell walls of Bacillus subtilis, a non-U(VI)-reducing, Gram-positive bacterium. The current study examined the reduction of this biogenic, cell-associated HUP mineral by three dissimilatory metal-reducing bacteria, Anaeromyxobacter dehalogenans strain K, Geobacter sulfurreducens strain PCA, and Shewanella putrefaciens strain CN-32, and compared it to the bioreduction of abiotically formed and freely suspended HUP of larger particle size. Uranium speciation in the solid phase was followed over a 10- to 20-day reaction period by X-ray absorption fine structure spectroscopy (XANES and EXAFS) and showed varying extents of U(VI) reduction to U(IV). The reduction extent of the same mass of HUP to U(IV) was consistently greater with the biogenic than with the abiotic material under the same experimental conditions. A greater extent of HUP reduction was observed in the presence of bicarbonate in solution, whereas a decreased extent of HUP reduction was observed with the addition of dissolved phosphate. These results indicate that the extent of U(VI) reduction is controlled by dissolution of the HUP phase, suggesting that the metal-reducing bacteria transfer electrons to the dissolved or bacterially adsorbed U(VI) species formed after HUP dissolution, rather than to solid-phase U(VI) in the HUP mineral. Interestingly, the bioreduced U(IV) atoms were not immediately coordinated to other U(IV) atoms (as in uraninite, UO2) but were similar in structure to the phosphate-complexed U(IV) species found in ningyoite [CaU(PO4)2·H2O]. This indicates a strong control by phosphate on the speciation of bioreduced U(IV), expressed as inhibition of the typical formation of uraninite under phosphate-free conditions.
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Affiliation(s)
- Xue Rui
- Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556, United States
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10
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Fan D, Anitori RP, Tebo BM, Tratnyek PG, Lezama Pacheco JS, Kukkadapu RK, Engelhard MH, Bowden ME, Kovarik L, Arey BW. Reductive sequestration of pertechnetate (⁹⁹TcO₄⁻) by nano zerovalent iron (nZVI) transformed by abiotic sulfide. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2013; 47:5302-5310. [PMID: 23611018 DOI: 10.1021/es304829z] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Under anoxic conditions, soluble pertechnetate (⁹⁹TcO₄⁻) can be reduced to less soluble TcO₂·nH₂O, but the oxide is highly susceptible to reoxidation. Here we investigate an alternative strategy for remediation of Tc-contaminated groundwater whereby sequestration as Tc sulfide is favored by sulfidic conditions stimulated by nano zerovalent iron (nZVI). nZVI was pre-exposed to increasing concentrations of sulfide in simulated Hanford groundwater for 24 h to mimic the onset of aquifer biotic sulfate reduction. Solid-phase characterizations of the sulfidated nZVI confirmed the formation of nanocrystalline FeS phases, but higher S/Fe ratios (>0.112) did not result in the formation of significantly more FeS. The kinetics of Tc sequestration by these materials showed faster Tc removal rates with increasing S/Fe between 0 and 0.056, but decreasing Tc removal rates with S/Fe > 0.224. The more favorable Tc removal kinetics at low S/Fe could be due to a higher affinity of TcO₄⁻ for FeS than iron oxides, and electron microscopy confirmed that the majority of the Tc was associated with FeS phases. The inhibition of Tc removal at high S/Fe appears to have been caused by excess HS(-). X-ray absorption spectroscopy revealed that as S/Fe increased, the pathway for Tc(IV) formation shifted from TcO₂·nH2₂ to Tc sulfide phases. The most substantial change of Tc speciation occurred at low S/Fe, coinciding with the rapid increase in Tc removal rate. This agreement further confirms the importance of FeS in Tc sequestration.
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Affiliation(s)
- Dimin Fan
- Division of Environmental and Biomolecular Systems, Oregon Health & Science University, 20000 NW Walker Road, Beaverton, Oregon 97006, United States
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Abstract
Recent work has indicated that iron (oxyhydr-)oxides are capable of structurally incorporating and releasing metals and nutrients as a result of Fe2+-induced iron oxide recrystallization. In the present paper, we briefly review the current literature examining the mechanisms by which iron oxides recrystallize and summarize how recrystallization affects metal incorporation and release. We also provide new experimental evidence for the Fe2+-induced release of structural manganese from manganese-doped goethite. Currently, the exact mechanism(s) for Fe2+-induced recrystallization remain elusive, although they are likely to be both oxide-and metal-dependent. We conclude by discussing some future research directions for Fe2+-catalysed iron oxide recrystallization.
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Lee JH, Fredrickson JK, Kukkadapu RK, Boyanov MI, Kemner KM, Lin X, Kennedy DW, Bjornstad BN, Konopka AE, Moore DA, Resch CT, Phillips JL. Microbial reductive transformation of phyllosilicate Fe(III) and U(VI) in fluvial subsurface sediments. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2012; 46:3721-3730. [PMID: 22414073 DOI: 10.1021/es204528m] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The microbial reduction of Fe(III) and U(VI) was investigated in shallow aquifer sediments collected from subsurface flood deposits near the Hanford Reach of the Columbia River in Washington State. Increases in 0.5 N HCl-extractable Fe(II) were observed in incubated sediments and (57)Fe Mössbauer spectroscopy revealed that Fe(III) associated with phyllosilicates and pyroxene was reduced to Fe(II). Aqueous uranium(VI) concentrations decreased in subsurface sediments incubated in sulfate-containing synthetic groundwater with the rate and extent being greater in sediment amended with organic carbon. X-ray absorption spectroscopy of bioreduced sediments indicated that 67-77% of the U signal was U(VI), probably as an adsorbed species associated with a new or modified reactive mineral phase. Phylotypes within the Deltaproteobacteria were more common in Hanford sediments incubated with U(VI) than without, and in U(VI)-free incubations, members of the Clostridiales were dominant with sulfate-reducing phylotypes more common in the sulfate-amended sediments. These results demonstrate the potential for anaerobic reduction of phyllosilicate Fe(III) and sulfate in Hanford unconfined aquifer sediments and biotransformations involving reduction and adsorption leading to decreased aqueous U concentrations.
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Affiliation(s)
- Ji-Hoon Lee
- Pacific Northwest National Laboratory, Richland, Washington 99352, United States
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13
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Blodau C. Thermodynamic Control on Terminal Electron Transfer and Methanogenesis. ACS SYMPOSIUM SERIES 2011. [DOI: 10.1021/bk-2011-1071.ch004] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Christian Blodau
- School of Environmental Sciences, University of Guelph, N1G 2W1, Guelph, Canada
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