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Liu Z, Li C, Tan K, Li Y, Tan W, Li X, Zhang C, Meng S, Liu L. Study of natural attenuation after acid in situ leaching of uranium mines using isotope fractionation and geochemical data. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 865:161033. [PMID: 36574851 DOI: 10.1016/j.scitotenv.2022.161033] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2022] [Revised: 11/22/2022] [Accepted: 12/14/2022] [Indexed: 06/17/2023]
Abstract
Acid in situ leaching (AISL) is a subsurface mining approach suitable for low-grade ores which does not generate tailings, and has been adopted widely in uranium mining. However, this technique causes an extremely high concentration of contaminants at post-mining sites and in the surroundings soon after the mining ceases. As a potential AISL remediation strategy, natural attenuation has not been studied in detail. To address this problem, groundwater collected from 26 wells located within, adjacent, upgradient, and downgradient of a post-mining site were chosen to analyze the fate of U(VI), SO42-, δ34S, and δ238U, to reveal the main mechanisms governing the migration and attenuation of the dominant contaminants and the spatio-temporal evolutions of contaminants in the confined aquifer of the post-mining site. The δ238U values vary from -0.07 ‰ to 0.09 ‰ in the post-mining site and from -1.43 ‰ to 0.03 ‰ around the post-mining site. The δ34S values were found to vary from 3.3 ‰ to 6.2 ‰ in the post-mining site and from 6.0 ‰ to 11.0 ‰ around the post-mining site. Detailed analysis suggests that there are large differences between the range of isotopic composition variation and the range of pollutants concentration distribution, and the estimated Rayleigh isotope fractionation factor is 0.9994-0.9997 for uranium and 1.0032-1.0061 for sulfur. The isotope ratio of uranium and sulfur can be used to deduce the migration history of the contaminants and the irreversibility of the natural attenuation process in the anoxic confined aquifer. Combining the isotopic fractionation data for U and S with the concentrations of uranium and sulfate improved the accuracy of understanding of reducing conditions along the flow path. The study also indicated that as long as the geological conditions are favorable for redox reactions, natural attenuation could be used as a cost-effective remediation scheme.
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Affiliation(s)
- Zhenzhong Liu
- School of Resource Environment and Safety Engineering, University of South China, Hengyang 421001, PR China
| | - Chunguang Li
- School of Resource Environment and Safety Engineering, University of South China, Hengyang 421001, PR China; China Institute of Atomic Energy, Beiing 102413, PR China; R&D Center of Radioactive Waste Treatment, Disposal and Modeling, University of South China, Hengyang 421001, PR China.
| | - Kaixuan Tan
- School of Resource Environment and Safety Engineering, University of South China, Hengyang 421001, PR China
| | - Yongmei Li
- School of Resource Environment and Safety Engineering, University of South China, Hengyang 421001, PR China
| | - Wanyu Tan
- Hunan City University, Yiyang 413000, PR China
| | - Xiqi Li
- School of Resource Environment and Safety Engineering, University of South China, Hengyang 421001, PR China
| | - Chong Zhang
- School of Resource Environment and Safety Engineering, University of South China, Hengyang 421001, PR China; Beijing Research Institute of Chemical Engineering Metallurgy, Beijing 101149, PR China
| | - Shuo Meng
- R&D Center of Radioactive Waste Treatment, Disposal and Modeling, University of South China, Hengyang 421001, PR China
| | - Longcheng Liu
- China Institute of Atomic Energy, Beiing 102413, PR China; R&D Center of Radioactive Waste Treatment, Disposal and Modeling, University of South China, Hengyang 421001, PR China; Department of Chemical Engineering, Royal Institute of Technology, Stockholm, Sweden
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Chen X, Zheng W, Anbar AD. Uranium Isotope Fractionation ( 238U/ 235U) during U(VI) Uptake by Freshwater Plankton. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2020; 54:2744-2752. [PMID: 31995356 DOI: 10.1021/acs.est.9b06421] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Uranium contamination in the environment is a serious public health concern. Biotic U(VI) reduction and nonreductive U(VI) uptake by microorganisms (e.g., U(VI) biosorption by cyanobacteria) are effective U remediation techniques. Variations of 238U/235U have been extensively explored to track biotic U(VI) reduction in laboratory experiments and field applications. However, U isotope fractionation during nonreductive U(VI) uptake by microorganisms is poorly constrained. To investigate U isotope fractionation in this process, we cultured freshwater plankton in the presence of U(VI) and measured 238U/235U in the culture media and biomass. We found that nonreductive U(VI) uptake by freshwater plankton fractionated U isotopes in the opposite direction compared to biotic U(VI) reduction. δ238U values in freshwater plankton were consistently ∼0.23 ± 0.06‰ lighter than those in dissolved U in the culture medium at various fractions of U removal (12-30%), consistent with equilibrium isotope fractionation in a closed system. The equilibrium isotope fractionation observed in our experiments possibly results from changes in coordination geometry between dissolved U(VI) in the culture media and adsorbed U(VI) on cell surfaces. Our experimental results highlight the need to consider U isotope fractionation during nonredox U(VI) uptake by microorganisms and organic matter when applying variations of 238U/235U to track biogeochemical processes and evaluate U remediation.
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Affiliation(s)
- Xinming Chen
- School of Earth and Space Exploration, Arizona State University, Tempe, Arizona 85287, United States
- Department of Earth, Ocean and Atmospheric Sciences and National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32306, United States
| | - Wang Zheng
- Institute of Surface-Earth System Science, Tianjin University, Tianjin 300072, China
| | - Ariel D Anbar
- School of Earth and Space Exploration, Arizona State University, Tempe, Arizona 85287, United States
- School of Molecular Sciences, Arizona State University, Tempe, Arizona 85287, United States
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Reimus PW, Dangelmayr MA, Clay JT, Chamberlain KR. Uranium Natural Attenuation Downgradient of an in Situ Recovery Mine Inferred from a Cross-Hole Field Test. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2019; 53:7483-7493. [PMID: 31132251 DOI: 10.1021/acs.est.9b01572] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
A field test was conducted at a uranium in situ recovery (solution mining) site to evaluate postmining uranium natural attenuation downgradient of an ore zone. Approximately 1 million liters of water from a previously mined ore zone was injected into an unmined ore zone that served as a proxy for a downgradient aquifer, while a well located approximately 23 m away was pumped. After 1 year of pumping, only about 39% of the injected U(VI) was recovered, whereas essentially 100% of coinjected chloride was recovered. A geochemical/transport model was used to simultaneously match the chloride and uranium concentrations at the pumping well while also qualitatively matching aqueous 238U/235U ratios, which reflect uranium removal from solution by reduction. It was concluded that ∼50% of the injected U(VI) was reduced to U(IV), although the reduction capacity in the flow pathways between the injection and production wells was estimated to be nearly exhausted by the end of the test. Estimating the reduction capacity of the downgradient aquifer can inform restoration strategy and offer a useful metric for regulatory decisions concerning the adequacy of restoration. U(VI) reduction should be effectively irreversible in these anoxic environments, which differ greatly from shallow oxic environments where U(IV) is readily reoxidized.
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Affiliation(s)
- Paul W Reimus
- Los Alamos National Laboratory , P.O. Box 1663, Los Alamos , New Mexico 87545 , United States
| | - Martin A Dangelmayr
- Los Alamos National Laboratory , P.O. Box 1663, Los Alamos , New Mexico 87545 , United States
| | - James T Clay
- Cameco Resources, Inc. , 762 Ross Road , Douglas , Wyoming 82633 , United States
| | - Kevin R Chamberlain
- University of Wyoming , Department of Geology and Geophysics , 1000 East University Avenue , Dept. 3006, Laramie , Wyoming 82071 , United States
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Skierszkan EK, Robertson JM, Lindsay MBJ, Stockwell JS, Dockrey JW, Das S, Weis D, Beckie RD, Mayer KU. Tracing Molybdenum Attenuation in Mining Environments Using Molybdenum Stable Isotopes. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2019; 53:5678-5686. [PMID: 30998001 DOI: 10.1021/acs.est.9b00766] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Molybdenum contamination is a concern in mining regions worldwide. Better understanding of processes controlling Mo mobility in mine wastes is critical for assessing potential impacts and developing water-quality management strategies associated with this element. Here, we used Mo stable isotope (δ98/95Mo) analyses to investigate geochemical controls on Mo mobility within a tailings management facility (TMF) featuring oxic and anoxic environments. These isotopic analyses were integrated with X-ray absorption spectroscopy, X-ray diffraction, Raman spectroscopy, transmission electron microscopy, and aqueous chemical data. Dissolved Mo concentrations were inversely correlated with δ98/95Mo values such that enrichment of heavy Mo isotopes in solution reflected attenuation processes. Inner-sphere complexation of Mo(VI) with ferrihydrite was the primary driver of Mo removal and was accompanied by a ca. 1‰ isotope fractionation. Limited Mo attenuation and isotope fractionation were observed in Fe(II)- and Mo-rich anoxic TMF seepage, while attenuation and isotope fractionation were greatest during discharge and oxidation of this seepage after discharge into a pond where Fe-(oxyhydr)oxide precipitation promoted Mo sorption. Overall, this study highlights the role of sorption onto Fe-(oxyhydr)oxides in attenuating Mo in oxic environments, a process which can be traced by Mo isotope analyses.
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Affiliation(s)
- Elliott K Skierszkan
- Lorax Environmental Services Ltd. , 2289 Burrard Street , Vancouver , BC Canada , V6J 3H9
| | - Jared M Robertson
- Department of Geological Sciences , University of Saskatchewan , 114 Science Place , Saskatoon , SK Canada , S7N 5E2
- O'Kane Consultants Inc. , 112 Research Drive , Saskatoon , SK Canada , S7N 3R3
| | - Matthew B J Lindsay
- Department of Geological Sciences , University of Saskatchewan , 114 Science Place , Saskatoon , SK Canada , S7N 5E2
| | - Justin S Stockwell
- Lorax Environmental Services Ltd. , 2289 Burrard Street , Vancouver , BC Canada , V6J 3H9
| | - John W Dockrey
- Lorax Environmental Services Ltd. , 2289 Burrard Street , Vancouver , BC Canada , V6J 3H9
| | - Soumya Das
- Department of Geological Sciences , University of Saskatchewan , 114 Science Place , Saskatoon , SK Canada , S7N 5E2
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Lefebvre P, Noël V, Lau KV, Jemison NE, Weaver KL, Williams KH, Bargar JR, Maher K. Isotopic Fingerprint of Uranium Accumulation and Redox Cycling in Floodplains of the Upper Colorado River Basin. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2019; 53:3399-3409. [PMID: 30807121 DOI: 10.1021/acs.est.8b05593] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Uranium (U) groundwater contamination is a major concern at numerous former mining and milling sites across the Upper Colorado River Basin (UCRB), USA, where U(IV)-bearing solids have accumulated within naturally reduced zones (NRZs). Understanding the processes governing U reduction and oxidation within NRZs is critical for assessing the persistence of U in groundwater. To evaluate the redox cycling of uranium, we measured the U concentrations and isotopic compositions (δ238U) of sediments and pore waters from four study sites across the UCRB that span a gradient in sediment texture and composition. We observe that U accumulation occurs primarily within fine-grained (low-permeability) NRZs that show active redox variations. Low-permeability NRZs display high accumulation and low export of U, with internal redox cycling of U. In contrast, within high-permeability NRZs, U is remobilized under oxidative conditions, possibly without any fractionation, and transported outside the NRZs. The low δ238U of sediments outside of defined NRZs suggests that these reduced zones act as additional U sources. Collectively, our results indicate that fine-grained NRZs have a greater potential to retain uranium, whereas NRZs with higher permeability may constitute a more-persistent but dilute U source.
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Affiliation(s)
- Pierre Lefebvre
- Department of Earth System Science , Stanford University , Stanford , California 94305 , United States
- Département de Géosciences , Ecole Normale Supérieure , Paris 75005 , France
| | - Vincent Noël
- Stanford Synchrotron Radiation Lightsource , SLAC National Accelerator Laboratory , Menlo Park , California 94025 , United States
| | - Kimberly V Lau
- Department of Geological Sciences , Stanford University , Stanford , California 94305 , United States
| | - Noah E Jemison
- Department of Geology , University of Illinois at Urbana-Champaign , Champaign , Illinois 61820 , United States
| | - Karrie L Weaver
- Department of Earth System Science , Stanford University , Stanford , California 94305 , United States
| | - Kenneth H Williams
- Earth Sciences Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
| | - John R Bargar
- Stanford Synchrotron Radiation Lightsource , SLAC National Accelerator Laboratory , Menlo Park , California 94025 , United States
| | - Kate Maher
- Department of Earth System Science , Stanford University , Stanford , California 94305 , United States
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Christensen JN, Dafflon B, Shiel AE, Tokunaga TK, Wan J, Faybishenko B, Dong W, Williams KH, Hobson C, Brown ST, Hubbard SS. Using strontium isotopes to evaluate the spatial variation of groundwater recharge. THE SCIENCE OF THE TOTAL ENVIRONMENT 2018; 637-638:672-685. [PMID: 29758424 DOI: 10.1016/j.scitotenv.2018.05.019] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2018] [Revised: 05/01/2018] [Accepted: 05/02/2018] [Indexed: 06/08/2023]
Abstract
Recharge of alluvial aquifers is a key component in understanding the interaction between floodplain vadose zone biogeochemistry and groundwater quality. The Rifle Site (a former U-mill tailings site) adjacent to the Colorado River is a well-established field laboratory that has been used for over a decade for the study of biogeochemical processes in the vadose zone and aquifer. This site is considered an exemplar of both a riparian floodplain in a semiarid region and a post-remediation U-tailings site. In this paper we present Sr isotopic data for groundwater and vadose zone porewater samples collected in May and July 2013 to build a mixing model for the fractional contribution of vadose zone porewater (i.e. recharge) to the aquifer and its variation across the site. The vadose zone porewater contribution to the aquifer ranged systematically from 0% to 38% and appears to be controlled largely by the microtopography of the site. The area-weighted average contribution across the site was 8% corresponding to a net recharge of 7.5 cm. Given a groundwater transport time across the site of ~1.5 to 3 years, this translates to a recharge rate between 5 and 2.5 cm/yr, and with the average precipitation to the site implies a loss from the vadose zone due to evapotranspiration of 83% to 92%, both ranges are in good agreement with previously published results by independent methods. A uranium isotopic (234U/238U activity ratios) mixing model for groundwater and surface water samples indicates that a ditch across the site is hydraulically connected to the aquifer and locally significantly affects groundwater. Groundwater samples with high U concentrations attributed to natural bio-reduced zones have 234U/238U activity ratios near 1, suggesting that the U currently being released to the aquifer originated from the former U-mill tailings.
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Affiliation(s)
- John N Christensen
- Earth and Environmental Science Area, Lawrence Berkeley National Laboratory, 1 Cyclotron Rd., Berkeley, CA 94720, United States.
| | - Baptiste Dafflon
- Earth and Environmental Science Area, Lawrence Berkeley National Laboratory, 1 Cyclotron Rd., Berkeley, CA 94720, United States
| | - Alyssa E Shiel
- College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331, United States
| | - Tetsu K Tokunaga
- Earth and Environmental Science Area, Lawrence Berkeley National Laboratory, 1 Cyclotron Rd., Berkeley, CA 94720, United States
| | - Jiamin Wan
- Earth and Environmental Science Area, Lawrence Berkeley National Laboratory, 1 Cyclotron Rd., Berkeley, CA 94720, United States
| | - Boris Faybishenko
- Earth and Environmental Science Area, Lawrence Berkeley National Laboratory, 1 Cyclotron Rd., Berkeley, CA 94720, United States
| | - Wenming Dong
- Earth and Environmental Science Area, Lawrence Berkeley National Laboratory, 1 Cyclotron Rd., Berkeley, CA 94720, United States
| | - Kenneth H Williams
- Earth and Environmental Science Area, Lawrence Berkeley National Laboratory, 1 Cyclotron Rd., Berkeley, CA 94720, United States
| | - Chad Hobson
- Earth and Environmental Science Area, Lawrence Berkeley National Laboratory, 1 Cyclotron Rd., Berkeley, CA 94720, United States
| | - Shaun T Brown
- Earth and Environmental Science Area, Lawrence Berkeley National Laboratory, 1 Cyclotron Rd., Berkeley, CA 94720, United States
| | - Susan S Hubbard
- Earth and Environmental Science Area, Lawrence Berkeley National Laboratory, 1 Cyclotron Rd., Berkeley, CA 94720, United States
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Jemison NE, Shiel AE, Johnson TM, Lundstrom CC, Long PE, Williams KH. Field Application of 238U/ 235U Measurements To Detect Reoxidation and Mobilization of U(IV). ENVIRONMENTAL SCIENCE & TECHNOLOGY 2018; 52:3422-3430. [PMID: 29464949 DOI: 10.1021/acs.est.7b05162] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Biostimulation to induce reduction of soluble U(VI) to relatively immobile U(IV) is an effective strategy for decreasing aqueous U(VI) concentrations in contaminated groundwater systems. If oxidation of U(IV) occurs following the biostimulation phase, U(VI) concentrations increase, challenging the long-term effectiveness of this technique. However, detecting U(IV) oxidation through dissolved U concentrations alone can prove difficult in locations with few groundwater wells to track the addition of U to a mass of groundwater. We propose the 238U/235U ratio of aqueous U as an independent, reliable tracer of U(IV) remobilization via oxidation or mobilization of colloids. Reduction of U(VI) produces 238U-enriched U(IV), whereas remobilization of solid U(IV) should not induce isotopic fractionation. The incorporation of remobilized U(IV) with a high 238U/235U ratio into the aqueous U(VI) pool produces an increase in 238U/235U of aqueous U(VI). During several injections of nitrate to induce U(IV) oxidation, 238U/235U consistently increased, suggesting 238U/235U is broadly applicable for detecting mobilization of U(IV).
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Affiliation(s)
- Noah E Jemison
- Department of Geology , University of Illinois at Urbana-Champaign , 3081 Natural History Building, 1301 W. Green St. , Urbana , Illinois 61801 , United States
| | - Alyssa E Shiel
- College of Earth, Ocean, and Atmospheric Sciences , Oregon State University , 104 CEOAS Administration Building, 101 SW 26th St. , Corvallis , Oregon 97331 , United States
| | - Thomas M Johnson
- Department of Geology , University of Illinois at Urbana-Champaign , 3081 Natural History Building, 1301 W. Green St. , Urbana , Illinois 61801 , United States
| | - Craig C Lundstrom
- Department of Geology , University of Illinois at Urbana-Champaign , 3081 Natural History Building, 1301 W. Green St. , Urbana , Illinois 61801 , United States
| | - Philip E Long
- Earth Sciences Division , Lawrence Berkeley National Laboratory , 1 Cyclotron Road , Berkeley , California 94720 , United States
| | - Kenneth H Williams
- Earth Sciences Division , Lawrence Berkeley National Laboratory , 1 Cyclotron Road , Berkeley , California 94720 , United States
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Dang DH, Wang W, Pelletier P, Poulain AJ, Evans RD. Uranium dispersion from U tailings and mechanisms leading to U accumulation in sediments: Insights from biogeochemical and isotopic approaches. THE SCIENCE OF THE TOTAL ENVIRONMENT 2018; 610-611:880-891. [PMID: 28830048 DOI: 10.1016/j.scitotenv.2017.08.156] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2017] [Revised: 08/14/2017] [Accepted: 08/15/2017] [Indexed: 06/07/2023]
Abstract
Uranium contamination is a worldwide problem that grows proportionally to human demands for energy and armory. Understanding U cycling in the environment is of eminent interest, mostly concerning ecosystems directly impacted by point sources. In Bow Lake (Ontario, Canada), which is located adjacent to a former U mine, exceptionally high concentrations of U are related to U dispersion from tailings and biogeochemical processes such as biotic reduction and adsorption. This has been shown by a U-Pb isotope composition model. In this study, we use U isotope fractionation (δ238U) to highlight U cycling and the role of bacteria (Geobacteraceae and sulfate-reducing bacteria) in affecting U cycling. Bacteria affected U cycling directly via biotic U reduction and indirectly via reductive dissolution of carrier phases. All the processes are interconnected through diagenetic reactions with the supply of bioavailable organic matter being the primary driving force of the diagenesis. This study is the first to use multiple biogeochemical and isotopic approaches to track U cycling from a contamination point source to U storage in lake sediments.
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Affiliation(s)
- Duc Huy Dang
- School of the Environment, Trent University, 1600 West Bank Drive, Peterborough, ON K9L 0G2, Canada.
| | - Wei Wang
- School of the Environment, Trent University, 1600 West Bank Drive, Peterborough, ON K9L 0G2, Canada
| | - Philip Pelletier
- Biology Department, University of Ottawa, 30 Marie Curie, Ottawa, ON K1N 6N5, Canada
| | - Alexandre J Poulain
- Biology Department, University of Ottawa, 30 Marie Curie, Ottawa, ON K1N 6N5, Canada
| | - R Douglas Evans
- School of the Environment, Trent University, 1600 West Bank Drive, Peterborough, ON K9L 0G2, Canada; Water Quality Center, Trent University, 1600 West Bank Drive, Peterborough, ON K9L 0G2, Canada
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Tarhan LG, Planavsky NJ, Wang X, Bellefroid EJ, Droser ML, Gehling JG. The late-stage "ferruginization" of the Ediacara Member (Rawnsley Quartzite, South Australia): Insights from uranium isotopes. GEOBIOLOGY 2018; 16:35-48. [PMID: 29105940 DOI: 10.1111/gbi.12262] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/25/2017] [Accepted: 09/01/2017] [Indexed: 06/07/2023]
Abstract
The paleoenvironmental setting in which the Ediacara Biota lived, died, and was preserved in the eponymous Ediacara Member of the Rawnsley Quartzite of South Australia is an issue of long-standing interest and recent debate. Over the past few decades, interpretations have ranged from deep marine to shallow marine to terrestrial. One of the key features invoked by adherents of the terrestrial paleoenvironment hypothesis is the presence of iron oxide coatings, inferred to represent the upper horizons of paleosols, along fossiliferous sandstone beds of the Ediacara Member. We find that these surficial oxides are characterized by (234 U/238 U) values which are not in secular equilibrium, indicating extensive fluid-rich alteration of these surfaces within the past approximately 2 million years. Specifically, the oxide coatings are characterized by (234 U/238 U) values >1, indicating interaction with high-(234 U/238 U) fluids derived from alpha-recoil discharge. These oxides are also characterized by light "stable" δ238/235 U values, consistent with a groundwater U source. These U isotope data thus corroborate sedimentological observations that ferric oxides along fossiliferous surfaces of the Ediacara Member consist of surficial, non-bedform-parallel staining, and sharply irregular patches, strongly reflecting post-depositional, late-stage processes. Therefore, both sedimentological and geochemical evidence indicate that Ediacara iron oxides do not reflect synsedimentary ferruginization and that the presence of iron oxides cannot be used to either invoke a terrestrial paleoenvironmental setting for or reconstruct the taphonomic pathways responsible for preservation of the Ediacara Biota. These findings demonstrate that careful assessment of paleoenvironmental parameters is essential to the reconstruction of the habitat of the Ediacara Biota and the factors that led to the fossilization of these early complex ecosystems.
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Affiliation(s)
- L G Tarhan
- Department of Geology and Geophysics, Yale University, New Haven, CT, USA
| | - N J Planavsky
- Department of Geology and Geophysics, Yale University, New Haven, CT, USA
| | - X Wang
- Department of Geology and Geophysics, Yale University, New Haven, CT, USA
| | - E J Bellefroid
- Department of Geology and Geophysics, Yale University, New Haven, CT, USA
| | - M L Droser
- Department of Earth Sciences, University of California, Riverside, Riverside, CA, USA
| | - J G Gehling
- South Australian Museum and University of Adelaide, Adelaide, SA, Australia
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Dang DH, Novotnik B, Wang W, Georg RB, Evans RD. Uranium Isotope Fractionation during Adsorption, (Co)precipitation, and Biotic Reduction. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2016; 50:12695-12704. [PMID: 27797199 DOI: 10.1021/acs.est.6b01459] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Uranium contamination of surface environments is a problem associated with both U-ore extraction/processing and situations in which groundwater comes into contact with geological formations high in uranium. Apart from the environmental concerns about U contamination, its accumulation and isotope composition have been used in marine sediments as a paleoproxy of the Earth's oxygenation history. Understanding U isotope geochemistry is then essential either to develop sustainable remediation procedures as well as for use in paleotracer applications. We report on parameters controlling U immobilization and U isotope fractionation by adsorption onto Mn/Fe oxides, precipitation with phosphate, and biotic reduction. The light U isotope (235U) is preferentially adsorbed on Mn/Fe oxides in an oxic system. When adsorbed onto Mn/Fe oxides, dissolved organic carbon and carbonate are the most efficient ligands limiting U binding resulting in slight differences in U isotope composition (δ238U = 0.22 ± 0.06‰) compared to the DOC/DIC-free configuration (δ238U = 0.39 ± 0.04‰). Uranium precipitation with phosphate does not induce isotope fractionation. In contrast, during U biotic reduction, the heavy U isotope (238U) is accumulated in reduced species (δ238U up to -1‰). The different trends of U isotope fractionation in oxic and anoxic environments makes its isotope composition a useful tracer for both environmental and paleogeochemical applications.
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Affiliation(s)
- Duc Huy Dang
- School of the Environment and ‡Water Quality Center, Trent University , 1600 West Bank Drive, Peterborough, Ontario, Canada K9L 0G2
| | - Breda Novotnik
- School of the Environment and ‡Water Quality Center, Trent University , 1600 West Bank Drive, Peterborough, Ontario, Canada K9L 0G2
| | - Wei Wang
- School of the Environment and ‡Water Quality Center, Trent University , 1600 West Bank Drive, Peterborough, Ontario, Canada K9L 0G2
| | - R Bastian Georg
- School of the Environment and ‡Water Quality Center, Trent University , 1600 West Bank Drive, Peterborough, Ontario, Canada K9L 0G2
| | - R Douglas Evans
- School of the Environment and ‡Water Quality Center, Trent University , 1600 West Bank Drive, Peterborough, Ontario, Canada K9L 0G2
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11
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Jemison NE, Johnson TM, Shiel AE, Lundstrom CC. Uranium Isotopic Fractionation Induced by U(VI) Adsorption onto Common Aquifer Minerals. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2016; 50:12232-12240. [PMID: 27758097 DOI: 10.1021/acs.est.6b03488] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Uranium groundwater contamination due to U mining and processing affects numerous sites globally. Bioreduction of soluble, mobile U(VI) to U(IV)-bearing solids is potentially a very effective remediation strategy. Uranium isotopes (238U/235U) have been utilized to track the progress of microbial reduction, with laboratory and field studies finding a ∼1‰ isotopic fractionation, with the U(IV) product enriched in 238U. However, the isotopic fractionation produced by adsorption may complicate the use of 238U/235U to trace microbial reduction. A previous study found that adsorption of U(VI) onto Mn oxides produced a -0.2‰ fractionation with the adsorbed U(VI) depleted in 238U. In this study, adsorption to quartz, goethite, birnessite, illite, and aquifer sediments induced an average isotopic fractionation of -0.15‰ with the adsorbed U(VI) isotopically lighter than coexisting aqueous U(VI). In bicarbonate-bearing matrices, the fractionation depended little on the nature of the sorbent, with only birnessite producing an atypically large fractionation. In the case of solutions with ionic strengths much lower than those of typical groundwater, less isotopic fractionation was produced than U(VI) solutions with greater ionic strength. Studies using U isotope data to assess U(VI) reduction must consider adsorption as a lesser, but significant isotope fractionation process.
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Affiliation(s)
- N E Jemison
- Department of Geology, University of Illinois at Urbana-Champaign , 156 Computing Applications Building, 605 E. Springfield Avenue, Champaign, Illinois 61820, United States
| | - T M Johnson
- Department of Geology, University of Illinois at Urbana-Champaign , 156 Computing Applications Building, 605 E. Springfield Avenue, Champaign, Illinois 61820, United States
| | - A E Shiel
- College of Earth, Ocean, and Atmospheric Sciences, Oregon State University , 104 CEOAS Administration Building, 101 26th Street, Corvallis, Oregon 97322, United States
| | - C C Lundstrom
- Department of Geology, University of Illinois at Urbana-Champaign , 156 Computing Applications Building, 605 E. Springfield Avenue, Champaign, Illinois 61820, United States
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Brown ST, Basu A, Christensen JN, Reimus P, Heikoop J, Simmons A, Woldegabriel G, Maher K, Weaver K, Clay J, DePaolo DJ. Isotopic Evidence for Reductive Immobilization of Uranium Across a Roll-Front Mineral Deposit. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2016; 50:6189-6198. [PMID: 27203292 DOI: 10.1021/acs.est.6b00626] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We use uranium (U) isotope ratios to detect and quantify the extent of natural U reduction in groundwater across a roll front redox gradient. Our study was conducted at the Smith Ranch-Highland in situ recovery (ISR) U mine in eastern Wyoming, USA, where economic U deposits occur in the Paleocene Fort Union formation. To evaluate the fate of aqueous U in and adjacent to the ore body, we investigated the chemical composition and isotope ratios of groundwater samples from the roll-front type ore body and surrounding monitoring wells of a previously mined area. The (238)U/(235)U of groundwater varies by approximately 3‰ and is correlated with U concentrations. Fluid samples down-gradient of the ore zone are the most depleted in (238)U and have the lowest U concentrations. Activity ratios of (234)U/(238)U are ∼5.5 up-gradient of the ore zone, ∼1.0 in the ore zone, and between 2.3 and 3.7 in the down-gradient monitoring wells. High-precision measurements of (234)U/(238)U and (238)U/(235)U allow for development of a conceptual model that evaluates both the migration of U from the ore body and the extent of natural attenuation due to reduction. We find that the premining migration of U down-gradient of the delineated ore body is minimal along eight transects due to reduction in or adjacent to the ore body, whereas two other transects show little or no sign of reduction in the down-gradient region. These results suggest that characterization of U isotopic ratios at the mine planning stage, in conjunction with routine geochemical analyses, can be used to identify where more or less postmining remediation will be necessary.
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Affiliation(s)
- Shaun T Brown
- Department of Earth and Planetary Science University of California , Berkeley, California 94709, United States
- Energy Geosciences Division, E.O. Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States
| | - Anirban Basu
- Department of Earth and Planetary Science University of California , Berkeley, California 94709, United States
- Energy Geosciences Division, E.O. Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States
| | - John N Christensen
- Energy Geosciences Division, E.O. Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States
| | - Paul Reimus
- Earth and Environmental Sciences Division, Los Alamos National Laboratory , Los Alamos, New Mexico 87454, United States
| | - Jeffrey Heikoop
- Earth and Environmental Sciences Division, Los Alamos National Laboratory , Los Alamos, New Mexico 87454, United States
| | - Ardyth Simmons
- Earth and Environmental Sciences Division, Los Alamos National Laboratory , Los Alamos, New Mexico 87454, United States
| | - Giday Woldegabriel
- Earth and Environmental Sciences Division, Los Alamos National Laboratory , Los Alamos, New Mexico 87454, United States
| | - Kate Maher
- Department of Geological Sciences, Stanford University , Stanford, California 94305, United States
| | - Karrie Weaver
- Department of Geological Sciences, Stanford University , Stanford, California 94305, United States
| | - James Clay
- Power Resources Inc. , Smith Ranch-Highland Operation, 762 Ross Road, Douglas, Wyoming 82633, United States
| | - Donald J DePaolo
- Department of Earth and Planetary Science University of California , Berkeley, California 94709, United States
- Energy Geosciences Division, E.O. Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States
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Guo Z, Li Y, Pan S, Xu J. Fabrication of Fe3O4@cyclodextrin magnetic composite for the high-efficient removal of Eu(III). J Mol Liq 2015. [DOI: 10.1016/j.molliq.2015.02.034] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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14
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Basu A, Brown ST, Christensen JN, DePaolo DJ, Reimus PW, Heikoop JM, Woldegabriel G, Simmons AM, House BM, Hartmann M, Maher K. Isotopic and Geochemical Tracers for U(VI) Reduction and U Mobility at an in Situ Recovery U Mine. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2015; 49:5939-5947. [PMID: 25909757 DOI: 10.1021/acs.est.5b00701] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
In situ recovery (ISR) uranium (U) mining mobilizes U in its oxidized hexavalent form (U(VI)) by oxidative dissolution of U from the roll-front U deposits. Postmining natural attenuation of residual U(VI) at ISR mines is a potential remediation strategy. Detection and monitoring of naturally occurring reducing subsurface environments are important for successful implementation of this remediation scheme. We used the isotopic tracers (238)U/(235)U (δ(238)U), (234)U/(238)U activity ratio, and (34)S/(32)S (δ(34)S), and geochemical measurements of U ore and groundwater collected from 32 wells located within, upgradient, and downgradient of a roll-front U deposit to detect U(VI) reduction and U mobility at an ISR mining site at Rosita, TX, USA. The δ(238)U in Rosita groundwater varies from +0.61‰ to -2.49‰, with a trend toward lower δ(238)U in downgradient wells. The concurrent decrease in U(VI) concentration and δ(238)U with an ε of 0.48‰ ± 0.08‰ is indicative of naturally occurring reducing environments conducive to U(VI) reduction. Additionally, characteristic (234)U/(238)U activity ratio and δ(34)S values may also be used to trace the mobility of the ore zone groundwater after mining has ended. These results support the use of U isotope-based detection of natural attenuation of U(VI) at Rosita and other similar ISR mining sites.
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Affiliation(s)
- Anirban Basu
- †Department of Earth and Planetary Science, University of California, Berkeley, 307 McCone Hall, Berkeley, California 94720, United States
| | - Shaun T Brown
- †Department of Earth and Planetary Science, University of California, Berkeley, 307 McCone Hall, Berkeley, California 94720, United States
- ‡Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720, United States
| | - John N Christensen
- ‡Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720, United States
| | - Donald J DePaolo
- †Department of Earth and Planetary Science, University of California, Berkeley, 307 McCone Hall, Berkeley, California 94720, United States
- ‡Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720, United States
| | - Paul W Reimus
- §Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Jeffrey M Heikoop
- §Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Giday Woldegabriel
- §Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Ardyth M Simmons
- §Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Brian M House
- §Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
- ∥Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California 92093, United States
| | - Matt Hartmann
- ⊥Uranium Resources, Inc., 6950 S. Potomac Street, Suite 300, Centennial, Colorado 80112, United States
| | - Kate Maher
- #Department of Geological and Environmental Sciences, Stanford University, Stanford, California 94305, United States
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Wiederhold JG. Metal stable isotope signatures as tracers in environmental geochemistry. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2015; 49:2606-24. [PMID: 25640608 DOI: 10.1021/es504683e] [Citation(s) in RCA: 172] [Impact Index Per Article: 19.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The biogeochemical cycling of metals in natural systems is often accompanied by stable isotope fractionation which can now be measured due to recent analytical advances. In consequence, a new research field has emerged over the last two decades, complementing the traditional stable isotope systems (H, C, O, N, S) with many more elements across the periodic table (Li, B, Mg, Si, Cl, Ca, Ti, V, Cr, Fe, Ni, Cu, Zn, Ge, Se, Br, Sr, Mo, Ag, Cd, Sn, Sb, Te, Ba, W, Pt, Hg, Tl, U) which are being explored and potentially applicable as novel geochemical tracers. This review presents the application of metal stable isotopes as source and process tracers in environmental studies, in particular by using mixing and Rayleigh model approaches. The most important concepts of mass-dependent and mass-independent metal stable isotope fractionation are introduced, and the extent of natural isotopic variations for different elements is compared. A particular focus lies on a discussion of processes (redox transformations, complexation, sorption, precipitation, dissolution, evaporation, diffusion, biological cycling) which are able to induce metal stable isotope fractionation in environmental systems. Additionally, the usefulness and limitations of metal stable isotope signatures as tracers in environmental geochemistry are discussed and future perspectives presented.
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Affiliation(s)
- Jan G Wiederhold
- Soil Chemistry Group, Institute of Biogeochemistry and Pollutant Dynamics, ETH Zurich , 8092 Zurich, Switzerland
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Andersen MB, Elliott T, Freymuth H, Sims KWW, Niu Y, Kelley KA. The terrestrial uranium isotope cycle. Nature 2015; 517:356-9. [DOI: 10.1038/nature14062] [Citation(s) in RCA: 118] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2014] [Accepted: 11/04/2014] [Indexed: 02/07/2023]
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Bao C, Wu H, Li L, Newcomer D, Long PE, Williams KH. Uranium bioreduction rates across scales: biogeochemical hot moments and hot spots during a biostimulation experiment at Rifle, Colorado. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2014; 48:10116-10127. [PMID: 25079237 DOI: 10.1021/es501060d] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We aim to understand the scale-dependent evolution of uranium bioreduction during a field experiment at a former uranium mill site near Rifle, Colorado. Acetate was injected to stimulate Fe-reducing bacteria (FeRB) and to immobilize aqueous U(VI) to insoluble U(IV). Bicarbonate was coinjected in half of the domain to mobilize sorbed U(VI). We used reactive transport modeling to integrate hydraulic and geochemical data and to quantify rates at the grid block (0.25 m) and experimental field scale (tens of meters). Although local rates varied by orders of magnitude in conjunction with biostimulation fronts propagating downstream, field-scale rates were dominated by those orders of magnitude higher rates at a few selected hot spots where Fe(III), U(VI), and FeRB were at their maxima in the vicinity of the injection wells. At particular locations, the hot moments with maximum rates negatively corresponded to their distance from the injection wells. Although bicarbonate injection enhanced local rates near the injection wells by a maximum of 39.4%, its effect at the field scale was limited to a maximum of 10.0%. We propose a rate-versus-measurement-length relationship (log R' = -0.63 log L - 2.20, with R' in μmol/mg cell protein/day and L in meters) for orders-of-magnitude estimation of uranium bioreduction rates across scales.
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Affiliation(s)
- Chen Bao
- John and Willie Leone Department of Energy and Mineral Engineering, ‡EMS Energy Institute, and §Earth and Environmental Systems Institute (EESI), Pennsylvania State University , University Park, Pennsylvania 16802, United States
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Zong P, Gou J. Rapid and economical synthesis of magnetic multiwalled carbon nanotube/iron oxide composite and its application in preconcentration of U(VI). J Mol Liq 2014. [DOI: 10.1016/j.molliq.2014.02.002] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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19
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Stoliker DL, Campbell KM, Fox PM, Singer DM, Kaviani N, Carey M, Peck NE, Bargar JR, Kent DB, Davis JA. Evaluating chemical extraction techniques for the determination of uranium oxidation state in reduced aquifer sediments. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2013; 47:9225-9232. [PMID: 23875928 DOI: 10.1021/es401450v] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Extraction techniques utilizing high pH and (bi)carbonate concentrations were evaluated for their efficacy in determining the oxidation state of uranium (U) in reduced sediments collected from Rifle, CO. Differences in dissolved concentrations between oxic and anoxic extractions have been proposed as a means to quantify the U(VI) and U(IV) content of sediments. An additional step was added to anoxic extractions using a strong anion exchange resin to separate dissolved U(IV) and U(VI). X-ray spectroscopy showed that U(IV) in the sediments was present as polymerized precipitates similar to uraninite and/or less ordered U(IV), referred to as non-uraninite U(IV) species associated with biomass (NUSAB). Extractions of sediment containing both uraninite and NUSAB displayed higher dissolved uranium concentrations under oxic than anoxic conditions while extractions of sediment dominated by NUSAB resulted in identical dissolved U concentrations. Dissolved U(IV) was rapidly oxidized under anoxic conditions in all experiments. Uraninite reacted minimally under anoxic conditions but thermodynamic calculations show that its propensity to oxidize is sensitive to solution chemistry and sediment mineralogy. A universal method for quantification of U(IV) and U(VI) in sediments has not yet been developed but the chemical extractions, when combined with solid-phase characterization, have a narrow range of applicability for sediments without U(VI).
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