1
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Wei Y, Chen Y, Cao X, Xiang M, Huang Y, Li H. A Critical Review of Groundwater Table Fluctuation: Formation, Effects on Multifields, and Contaminant Behaviors in a Soil and Aquifer System. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2024; 58:2185-2203. [PMID: 38237040 DOI: 10.1021/acs.est.3c08543] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2024]
Abstract
The groundwater table fluctuation (GTF) zone is an important medium for the hydrologic cycle between unsaturated soil and saturated aquifers, which accelerates the migration, transformation, and redistribution of contaminants and further poses a potential environmental risk to humans. In this review, we clarify the key processes in the generation of the GTF zone and examine its links with the variation of the hydrodynamic and hydrochemistry field, colloid mobilization, and contaminant migration and transformation. Driven by groundwater recharge and discharge, GTF regulates water flow and the movement of the capillary fringe, which further control the advection and dispersion of contaminants in soil and groundwater. In addition, the formation and variation of the reactive oxygen species (ROS) waterfall are impacted by GTF. The changing ROS components partially determine the characteristic transformation of solutes and the dynamic redistribution of the microbial population. GTF facilitates the migration and transformation of contaminants (such as nitrogen, heavy metals, non-aqueous phase liquids, and volatile organic compounds) through colloid mobilization, the co-migration effect, and variation of the hydrodynamic and hydrochemistry fields. In conclusion, this review illustrates the limitations of the current literature on GTF, and the significance of GTF zones in the underground environment is underscored by expounding on the future directions and prospects.
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Affiliation(s)
- Yaqiang Wei
- School of Environmental and Chemical Engineering, Shanghai University, Shanghai 200444, China
| | - Yuling Chen
- School of Environmental and Chemical Engineering, Shanghai University, Shanghai 200444, China
| | - Xinde Cao
- School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Minghui Xiang
- School of Environmental and Chemical Engineering, Shanghai University, Shanghai 200444, China
| | - Yuan Huang
- School of Environmental and Chemical Engineering, Shanghai University, Shanghai 200444, China
| | - Hui Li
- School of Environmental and Chemical Engineering, Shanghai University, Shanghai 200444, China
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2
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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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3
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Li Y, Huang Y, Li Z, Tang X, Liu X, Hughes SS. Mechanisms of chromium isotope fractionation and the applications in the environment. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2022; 242:113948. [PMID: 35999763 DOI: 10.1016/j.ecoenv.2022.113948] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Revised: 07/31/2022] [Accepted: 08/01/2022] [Indexed: 06/15/2023]
Abstract
Chromium (Cr) is a toxic heavy metal that gives rise to environmental pollution and human risk. Chromium stable isotopes have a wide range of applications in both environmental field and earth science field. In this contribution, we focus on the application of the Cr isotope in both tracing pollution sources and monitoring Cr(Ⅵ) pollution. Meanwhile, we also provide a description of the main influencing factors controlling Cr isotope fractionation, chromium isotope analytical methods, and terrestrial Cr release. Chromium isotope tracing of contaminant sources is a new application method, it has a tremendous advantage in searching for the source of Cr pollution, which has not been covered in previous reviews. At the end of the article, the current status of Cr isotope applications in the paleo-environment is explained. Although there are still some uncertainties in practical applications, chromium isotope system shows great promise in the environmental aspects.
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Affiliation(s)
- Ying Li
- State Key Laboratory of Geohazard Prevention and Geoenvironment Protection, College of Geosciences, Chengdu University of Technology, Chengdu 610059, Sichuan, China
| | - Yi Huang
- State Key Laboratory of Geohazard Prevention and Geoenvironment Protection, College of Geosciences, Chengdu University of Technology, Chengdu 610059, Sichuan, China; State Key Laboratory of Collaborative Control and Joint Remediation of Soil and Water Pollution, College of Ecology and Environment, Chengdu University of Technology, Chengdu 610059, Sichuan, China.
| | - Zijing Li
- State Key Laboratory of Geohazard Prevention and Geoenvironment Protection, College of Geosciences, Chengdu University of Technology, Chengdu 610059, Sichuan, China
| | - Xue Tang
- State Key Laboratory of Geohazard Prevention and Geoenvironment Protection, College of Geosciences, Chengdu University of Technology, Chengdu 610059, Sichuan, China
| | - Xiaowen Liu
- State Key Laboratory of Geohazard Prevention and Geoenvironment Protection, College of Geosciences, Chengdu University of Technology, Chengdu 610059, Sichuan, China
| | - Scott S Hughes
- Department of Geosciences, Idaho State University, Pocatello, ID 83209, USA
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Davidson AB, Holmden C, Nomosatryo S, Henny C, Francois R, Crowe SA. Cr Isotopes and the Engineered Attenuation of Cr(VI)-Rich Runoff. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2021; 55:14938-14945. [PMID: 34669373 DOI: 10.1021/acs.est.1c01714] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The leaching of lateritic soils can result in drainage waters with high concentrations of Cr(VI). Such Cr(VI)-rich waters have developed in streams that drain lateritic soils in Central Sulawesi Island, Indonesia. Chromium in this lateritic drainage system is removed by reduction of Cr(VI) to Cr(III) through two faucets delivering an FeSO4 solution to the drainage waters. Cr stable isotope compositions from both water and sediment samples along the drainage path were used to evaluate the efficacy of this remediation strategy. Overall, dissolved [Cr(VI)] decreased moving downstream, but there was an increase in [Cr(VI)] after the first faucet that was effectively removed at the second faucet. This intermittent increase in [Cr(VI)] was the likely result of oxidative remobilization of sediment Cr(III) through reaction with Mn oxides. Cr isotope distributions reflect near quantitative reduction associated with the FeSO4 faucets but also reveal that Cr isotope fractionation is imparted due to Cr redox cycling, downstream. During this redox cycling, fractionation appeared to accompany oxidation, with the product Cr(VI) becoming enriched in 53Cr relative to the reactant Cr(III) with an apparent fractionation factor of 0.7 ± 0.3‰. This study suggests that while FeSO4 effectively removes Cr(VI) from the drainage, the presence of Mn oxides can confound attenuation and improvements to Cr(VI) remediation should consider means of preventing the back reaction of Cr(III) with Mn oxides.
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Affiliation(s)
- Ashley B Davidson
- Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia, Earth Sciences Building, 2020-2207 Main Mall, Vancouver, British Columbia V6T 1Z4, Canada
| | - Chris Holmden
- Saskatchewan Isotope Laboratory, University of Saskatchewan, Geology Building, 114 Science Place, Saskatoon S7N 5E2, Saskatchewan Canada
| | - Sulung Nomosatryo
- Research Center for Limnology, Indonesian Institute of Sciences (LIPI), Cibinong-Bogor, 16911, Indonesia
- GFZ German Research Centre for Geosciences, Section Geomicrobiology, 14473 Potsdam, Germany
| | - Cynthia Henny
- Research Center for Limnology, Indonesian Institute of Sciences (LIPI), Cibinong-Bogor, 16911, Indonesia
| | - Roger Francois
- Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia, Earth Sciences Building, 2020-2207 Main Mall, Vancouver, British Columbia V6T 1Z4, Canada
| | - Sean A Crowe
- Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia, Earth Sciences Building, 2020-2207 Main Mall, Vancouver, British Columbia V6T 1Z4, Canada
- Department of Microbiology & Immunology, University of British Columbia, 1365-2350 Health Sciences Mall, Vancouver, British Columbia V6T 1Z3, Canada
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5
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Hydrogeochemical Processes and Natural Background Levels of Chromium in an Ultramafic Environment. The Case Study of Vermio Mountain, Western Macedonia, Greece. WATER 2021. [DOI: 10.3390/w13202809] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
The hydrogeochemical processes and natural background levels (NBLs) of chromium in the ultramafic environment of Vermio Mountain, Western Macedonia, Greece, were studied. Seventy groundwater samples were collected from 15 natural springs between 2014–2020, and an extensive set of physical and chemical parameters were determined. The ultramafic-dominated environment of western Vermio Mt. favors elevated groundwater concentrations of dissolved magnesium (Mg2+), silicon (Si), nickel (Ni), and Cr in natural spring waters. Chromium was the principal environmental parameter that exhibited a wide range of concentrations, from 0.5 to 131.5 μg/L, systematically exceeding the permissible limit of 50 μg/L for drinking water. Statistical evaluation of hydrogeological, hydrochemical, and hydrological data highlighted the water-ultramafic rock process as the predominant contributor of Cr in groundwater. The NBL assessment for Cr and Cr(VI) was successfully applied to the typical ultramafic-dominated spring “Potistis” that satisfied all the methodology criteria. The NBLs of Cr and Cr(VI) were defined at 130 μg/L and 100 μg/L, respectively, revealing that a natural ultramafic-dominated environment exhibits the geochemical potential to contribute very high concentrations of geogenic Cr to groundwater. The holistic methodology, proposed herein, could be implemented in any catchment scale to assess geogenic and anthropogenic Cr-sources that degrade groundwater quality.
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Xia B, Zhu JM, Wang X, Zhang L, Wu G. Chromium isotope fractionation during black shale weathering and its environmental implications. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 783:147126. [PMID: 34088147 DOI: 10.1016/j.scitotenv.2021.147126] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2021] [Revised: 04/08/2021] [Accepted: 04/09/2021] [Indexed: 06/12/2023]
Abstract
Black shale contains abundant pyrite and organic matter that are susceptible to weathering when exposed to the air. In the process of weathering, acid mine drainage can be produced, and a range of toxic trace elements including Cr can be released and transported into rivers, groundwater and soils, potentially leading to severe environmental pollution. In order to study Cr migration and Cr isotopic fractionation during black shale weathering, we sampled metalliferous black shales and cherts from two weathering profiles at Shadi and Yutangba from the Permian Maokou Formation in Enshi Prefecture. The unweathered samples in Shadi and Yutangba have high Cr contents (1562 μg/g and 643 μg/g, respectively), and highly fractionated Cr isotopic compositions (2.04 ± 0.11‰ and 1.91 ± 0.09‰, respectively, expressed as δ53Cr). The narrow range of authigenic δ53Cr in these unweathered shales suggests that the δ53Cr value of the seawater was relatively stable during the period of deposition. Strongly weathered shales in Shadi and Yutangba both display significant Cr losses compared to the unweathered counterparts. Their average δ53Cr values are 1.75 ± 0.12‰ and 1.85 ± 0.39‰ for Shadi and Yutangba, respectively, which are isotopically lighter than fresh samples. This indicates that heavier Cr isotopes are preferentially leached into fluids, leaving the residues enriched in lighter isotopes during black shale weathering. However, the δ53Cr values of the samples close to the water table are higher than those of the unaltered ones, which can be explained by adsorption or quantitative reduction of Cr(VI) near the water table. The fact that Cr isotopes are fractionated during black shale weathering may complicate the application of δ53Cr in polluted samples to identify the Cr sources in areas with exposed black shales. The δ53Cr of seepage water can be measured and treated as a more realistic source signal.
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Affiliation(s)
- Bo Xia
- State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China
| | - Jian-Ming Zhu
- State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China.
| | - Xiangli Wang
- Department of Marine Sciences, University of South Alabama, Mobile, AL 36688, USA; Dauphin Island Sea Lab, Dauphin Island, AL 36528, USA
| | - Lixin Zhang
- School of Earth System Science, Tianjin University, Tianjin 300072, China
| | - Guangliang Wu
- State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China
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7
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Wang L, Jin Y, Weiss DJ, Schleicher NJ, Wilcke W, Wu L, Guo Q, Chen J, O'Connor D, Hou D. Possible application of stable isotope compositions for the identification of metal sources in soil. JOURNAL OF HAZARDOUS MATERIALS 2021; 407:124812. [PMID: 33340973 DOI: 10.1016/j.jhazmat.2020.124812] [Citation(s) in RCA: 46] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2020] [Revised: 11/22/2020] [Accepted: 12/05/2020] [Indexed: 06/12/2023]
Abstract
Metals in soil are potentially harmful to humans and ecosystems. Stable isotope measurement may provide "fingerprint" information on the sources of metals. In light of the rapid progress in this emerging field, we present a state-of-the-art overview of how useful stable isotopes are in soil metal source identification. Distinct isotope signals in different sources are the key prerequisites for source apportionment. In this context, Zn and Cd isotopes are particularly helpful for the identification of combustion-related industrial sources, since high-temperature evaporation-condensation would largely fractionate the isotopes of both elements. The mass-independent fractionation of Hg isotopes during photochemical reactions allows for the identification of atmospheric sources. However, compared with traditionally used Sr and Pb isotopes for source tracking whose variations are due to the radiogenic processes, the biogeochemical low-temperature fractionation of Cr, Cu, Zn, Cd, Hg and Tl isotopes renders much uncertainty, since large intra-source variations may overlap the distinct signatures of inter-source variations (i.e., blur the source signals). Stable isotope signatures of non-metallic elements can also aid in source identification in an indirect way. In fact, the soils are often contaminated with different elements. In this case, a combination of stable isotope analysis with mineralogical or statistical approaches would provide more accurate results. Furthermore, isotope-based source identification will also be helpful for comprehending the temporal changes of metal accumulation in soil systems.
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Affiliation(s)
- Liuwei Wang
- School of Environment, Tsinghua University, Beijing 100084, China
| | - Yuanliang Jin
- School of Environment, Tsinghua University, Beijing 100084, China
| | - Dominik J Weiss
- Department of Earth Science & Engineering, Imperial College London, London SW7 2AZ, United Kingdom; Civil and Environmental Engineering, Princeton University, New York, USA
| | - Nina J Schleicher
- Department of Earth Science & Engineering, Imperial College London, London SW7 2AZ, United Kingdom
| | - Wolfgang Wilcke
- Institute of Geography and Geoecology, Karlsruhe Institute of Technology (KIT), Reinhard-Baumeister-Platz 1, Karlsruhe 76131, Germany
| | - Longhua Wu
- Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China
| | - Qingjun Guo
- Center for Environmental Remediation, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China; College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Jiubin Chen
- Institute of Surface-Earth System Science, School of Earth System Science, Tianjin University, Tianjin, 300072, China
| | - David O'Connor
- School of Real Estate and Land Management, Royal Agricultural University, Cirencester, GL7 1RS, United Kingdom
| | - Deyi Hou
- School of Environment, Tsinghua University, Beijing 100084, China.
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8
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He X, Chen G, Fang Z, Liang W, Li B, Tang J, Sun Y, Qin L. Source identification of chromium in the sediments of the Xiaoqing River and Laizhou Bay: A chromium stable isotope perspective. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2020; 264:114686. [PMID: 32422517 DOI: 10.1016/j.envpol.2020.114686] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2019] [Revised: 04/11/2020] [Accepted: 04/26/2020] [Indexed: 06/11/2023]
Abstract
Hexavalent chromium, Cr(VI), is a heavy metal contaminant and the reduction of Cr(VI) is accompanied by large isotopic fractionation. In this study, the sources of Cr were explored using the Cr isotopic composition of sediments from the Xiaoqing River, a heavily polluted river located in the Shandong Province of China, which flows into Laizhou Bay. The results show that δ53Cr values of the sediments are the highest upstream near the pollution source, and gradually decrease along the river toward the range for igneous reservoirs observed near the estuary. Based on the calculation of authigenic Cr isotopic composition (δ53Crauth) using the detrital index and leaching experiments, we suggest that the authigenic Cr in the sample near the pollution source with the highest δ53Crauth value mainly comes from the reduction of Cr(VI) discharged by anthropogenic activity, and authigenic Cr in other samples in the midstream with δ53Crauth values slightly higher than the range of igneous reservoirs may come from natural oxidative Cr weathering products. By introducing a Rayleigh model, we calculate that at least 31%-55% of Cr(VI) in the river water had been reduced to Cr(III) near the pollution source. Due to the self-purification ability of the river, Cr(VI) was reduced; thus, there is no record of high δ53Crauth values in the downstream of the Xiaoqing River and Laizhou Bay, indicating no obvious Cr pollution in these locations. The limited variation of δ53Cr values for samples from a sediment core in Laizhou Bay is also indicative of no obvious Cr pollution in the history. The Cr isotopic compositions of the river sediments are useful for the identification of Cr sources and can be used to advise environmental remediation on Cr pollution.
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Affiliation(s)
- Xiaoqing He
- CAS Key Laboratory of Crust-Mantle Materials and Environments, University of Science and Technology of China, Hefei, 230026, PR China; CAS Center for Excellence in Comparative Planetology, Hefei, 230026, PR China
| | - Guojun Chen
- CAS Key Laboratory of Crust-Mantle Materials and Environments, University of Science and Technology of China, Hefei, 230026, PR China; Guangdong Key Laboratory of Integrated Agro-Environmental Pollution Control and Management, Guangdong Institute of Eco-Environmental Science and Technology, Guangdong Academy of Sciences, Guangzhou, 510650, PR China; National-Regional Joint Engineering Research Center for Soil Pollution Control and Remediation in South China, Guangzhou, 510650, PR China
| | - Ziyao Fang
- CAS Key Laboratory of Crust-Mantle Materials and Environments, University of Science and Technology of China, Hefei, 230026, PR China; CAS Center for Excellence in Comparative Planetology, Hefei, 230026, PR China
| | - Wenjian Liang
- CAS Key Laboratory of Crust-Mantle Materials and Environments, University of Science and Technology of China, Hefei, 230026, PR China
| | - Boda Li
- CAS Key Laboratory of Crust-Mantle Materials and Environments, University of Science and Technology of China, Hefei, 230026, PR China; Department of Earth, Environmental and Planetary Sciences, Rice University, Houston, TX, 77005, USA
| | - Jianhui Tang
- CAS Key Laboratory of Coastal Environmental Processes and Ecological Remediation, Yantai Institute of Coastal Zone Research (YIC), Chinese Academy of Sciences (CAS) Shandong Key Laboratory of Coastal Environmental Processes, YICCAS, Yantai, 264003, PR China
| | - Yongge Sun
- Institute of Environment & Biogeochemistry (eBig), School of Earth Science, Zhejiang University, Hangzhou, 310027, China
| | - Liping Qin
- CAS Key Laboratory of Crust-Mantle Materials and Environments, University of Science and Technology of China, Hefei, 230026, PR China; CAS Center for Excellence in Comparative Planetology, Hefei, 230026, PR China.
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9
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Ceballos E, Margalef-Martí R, Carrey R, Frei R, Otero N, Soler A, Ayora C. Characterisation of the natural attenuation of chromium contamination in the presence of nitrate using isotopic methods. A case study from the Matanza-Riachuelo River basin, Argentina. THE SCIENCE OF THE TOTAL ENVIRONMENT 2020; 699:134331. [PMID: 31670212 DOI: 10.1016/j.scitotenv.2019.134331] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2019] [Revised: 08/10/2019] [Accepted: 09/05/2019] [Indexed: 06/10/2023]
Abstract
The groundwater contamination by hexavalent chromium (Cr(VI)) in a site of the Matanza-Riachuelo River basin (MRB), Argentina, has been evaluated by determining the processes that control the natural mobility and attenuation of Cr(VI) in the presence of high nitrate (NO3-) contents. The groundwater Cr(VI) concentrations ranged between 1.9E-5 mM and 0.04 mM, while the NO3- concentrations ranged between 0.5 mM and 3.9 mM. In order to evaluate the natural attenuation of Cr(VI) and NO3- in the MRB groundwater, Cr and N isotopes were measured in these contaminants. In addition, laboratory batch experiments were performed to determine the isotope fractionation (ε) during the reduction of Cr(VI) under denitrifying conditions. While the Cr(VI) reduction rate is not affected by the presence of NO3-, the NO3- attenuation is slower in the presence of Cr(VI). Nevertheless, no significant differences on ε values were observed when testing the absence or presence of each contaminant. The ε53Cr determined in the batch experiments describe a two- stage trend, in which Stage I is characterized by ε53Cr ~-1.8‰ and Stage II by ε53Cr ~-0.9‰. The respective ε15NNO3 obtained is -23.9‰ whereas ε18ONO3 amount to -25.7‰. Using these ε values and a Rayleigh fractionation model we estimate that an average of 60% of the original Cr(VI) is removed from the groundwater of the contaminated site. Moreover, the average degree of NO3- attenuation by denitrification is found to be about 20%. This study provides valuable information about the dynamics of a complex system that can serve as a basis for efficient management of contaminated groundwater in the most populated and industrialized basin of Argentina.
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Affiliation(s)
- Elina Ceballos
- Instituto de Hidrología de Llanuras "Dr. Eduardo J. Usunoff", CONICET-UNCPBA-CIC, República de Italia 780, 47 (B7300), Azul, Buenos Aires, Argentina.
| | - Rosanna Margalef-Martí
- Grup MAiMA, SGR Mineralogia Aplicada, Geoquímica i Geomicrobiologia, Departament de Mineralogia, Petrologia i Geologia Aplicada, Facultat de Ciències de la Terra, Universitat de Barcelona, UB, C/Martí i Franquès, s/n, 08028 Barcelona, Spain
| | - Raul Carrey
- Grup MAiMA, SGR Mineralogia Aplicada, Geoquímica i Geomicrobiologia, Departament de Mineralogia, Petrologia i Geologia Aplicada, Facultat de Ciències de la Terra, Universitat de Barcelona, UB, C/Martí i Franquès, s/n, 08028 Barcelona, Spain
| | - Robert Frei
- Department of Geosciences and Natural Resource Management, University of Copenhagen, Copenhagen, Denmark
| | - Neus Otero
- Grup MAiMA, SGR Mineralogia Aplicada, Geoquímica i Geomicrobiologia, Departament de Mineralogia, Petrologia i Geologia Aplicada, Facultat de Ciències de la Terra, Universitat de Barcelona, UB, C/Martí i Franquès, s/n, 08028 Barcelona, Spain; Serra Húnter Fellow, Generalitat de Catalunya, Spain
| | - Albert Soler
- Grup MAiMA, SGR Mineralogia Aplicada, Geoquímica i Geomicrobiologia, Departament de Mineralogia, Petrologia i Geologia Aplicada, Facultat de Ciències de la Terra, Universitat de Barcelona, UB, C/Martí i Franquès, s/n, 08028 Barcelona, Spain
| | - Carlos Ayora
- Department of Geoscience, Institute of Environmental Assessment and Water Research, IDAEA-CSIC, C/Jordi Girona, 18, 08028 Barcelona, Spain
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Toma J, Holmden C, Shakotko P, Pan Y, Ootes L. Cr isotopic insights into ca. 1.9 Ga oxidative weathering of the continents using the Beaverlodge Lake paleosol, Northwest Territories, Canada. GEOBIOLOGY 2019; 17:467-489. [PMID: 31006990 DOI: 10.1111/gbi.12342] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2018] [Revised: 03/05/2019] [Accepted: 03/26/2019] [Indexed: 06/09/2023]
Abstract
The ca. 1.9 Ga Beaverlodge Lake paleosol was studied using redox-sensitive Cr isotopes in order to determine the isotopic response to paleoweathering of a rhyodacite parent rock 500 million years after the Great Oxidation Event. Redox reactions occurring in modern weathering environments produce Cr(VI) that is enriched in heavy Cr isotopes compared to the igneous inventory. Cr(VI) species are soluble and easily leached from soils into streams and rivers, thus, leaving particle-reactive and isotopically light Cr(III) species to build up in soils. The Beaverlodge Lake paleosol and two other published weathering profiles of similar age, the Flin Flon and Schreiber Beach paleosols, are not as isotopically light as modern soils, indicating that rivers were not as isotopically heavy at that time. Considering that the global average δ53 Cr value for the oxidative weathering flux of Cr to the oceans today is just 0.27 ± 0.30‰ (1σ) based on a steady-state analysis of the modern ocean Cr cycle, the oxidative weathering flux of Cr to the oceans at ca. 1.9 Ga would have likely been shifted to lower δ53 Cr values, and possibly lower than the igneous inventory (-0.12 ± 0.10‰, 2σ). Mn oxides are the main oxidant of Cr(III) in modern soils, but there is no evidence that they formed in the studied paleosols. Cr(VI) may have formed by direct oxidation of Cr(III) using molecular oxygen or H2 O2 , but neither pathway is as efficient as Mn oxides for producing Cr(VI). The picture that emerges from this and other studies of Cr isotope variation in ca. 1.9 Ga paleosols is of atmospheric oxygen concentrations that are high enough to oxidize iron, but too low to oxidize Mn, resulting in low Cr(VI) inventories in Earth surface environments.
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Affiliation(s)
- Jonathan Toma
- Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, AB, Canada
| | - Chris Holmden
- Department of Geological Sciences, University of Saskatchewan, Saskatoon, SK, Canada
| | | | - Yuanming Pan
- Department of Geological Sciences, University of Saskatchewan, Saskatoon, SK, Canada
| | - Luke Ootes
- British Columbia Geological Survey, Stn Prov Govt, Victoria, BC, Canada
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11
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Zhang Q, Song Y, Amor K, Huang WE, Porcelli D, Thompson I. Monitoring Cr toxicity and remediation processes - combining a whole-cell bioreporter and Cr isotope techniques. WATER RESEARCH 2019; 153:295-303. [PMID: 30735959 DOI: 10.1016/j.watres.2019.01.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2018] [Revised: 01/12/2019] [Accepted: 01/14/2019] [Indexed: 06/09/2023]
Abstract
Bioremediation is a sustainable and cost-effective means of contaminant detoxification. Although Cr(VI) is toxic at high concentrations, various microbes can utilise it as an electron accepter in the bioremediation process, and reduce it to the less toxic form Cr(III). During remediation, it is important to monitor the level of toxicity and effectiveness of Cr(VI) reduction in order to optimize the conditions. This study employed a whole-cell bioreporter Acinetobacter baylyi ADPWH-recA to access the degree of toxicity of different species of Cr over a range of initial concentrations. It also investigated whether Cr isotope fractionation factors were impacted by different levels of Cr toxicity (related to its concentration) and Cr(VI) reduction rates by Cr resistant bacteria Pseudomonas fluorescens LB 300. The results show that, of both Cr2O72- and CrO42-, the whole-cell bioreporter was efficient in indicating the level of genotoxicity of Cr(VI) at low concentrations and cytotoxicity at high concentrations via variations of bioluminescence. High concentrations (> 100 mg/L) of Cr(III) could also strongly induce the luminescence in the bioreporter, indicating DNA damage at such abundance. Pseudomonas fluorescens LB 300 was found to be effective in reducing Cr(VI) even when the concentration was high (40 mg/L); however, complete Cr(VI) reduction was only observed at low concentrations (< 5 mg/L), since the toxicity of high concentrations of Cr(VI) impacted the effectiveness of reduction by the bacteria. During reduction, the C53r/C52r ratio of remaining Cr(VI) increased from its initial value, and the calculated fractionation factor by bacterial Cr(VI) reduction (ε) was -3.1±0.3‰. The fractionation factor was independent of the initial Cr(VI) concentration. Therefore, a single Cr isotope fractionation factor can be effectively applied in indicating the extent of bioremediation processing of Cr(VI) over a wide range of concentrations. This significantly simplified monitoring of Cr(VI) depletion in bioremediation, since variations of ε normally indicate a change in the reduction mechanism and therefore would complicate the elucidation of processes driving the remediation.
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Affiliation(s)
- Qiong Zhang
- Department of Earth Sciences, University of Oxford, South Parks Road, Oxford, OX1 3AN, United Kingdom.
| | - Yizhi Song
- Department of Engineering Science, University of Oxford, Parks Road, Oxford, OX1 3PJ, United Kingdom
| | - Ken Amor
- Department of Earth Sciences, University of Oxford, South Parks Road, Oxford, OX1 3AN, United Kingdom
| | - Wei E Huang
- Department of Engineering Science, University of Oxford, Parks Road, Oxford, OX1 3PJ, United Kingdom
| | - Don Porcelli
- Department of Earth Sciences, University of Oxford, South Parks Road, Oxford, OX1 3AN, United Kingdom
| | - Ian Thompson
- Department of Engineering Science, University of Oxford, Parks Road, Oxford, OX1 3PJ, United Kingdom
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12
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Kanagaraj G, Elango L. Chromium and fluoride contamination in groundwater around leather tanning industries in southern India: Implications from stable isotopic ratio δ 53Cr/δ 52Cr, geochemical and geostatistical modelling. CHEMOSPHERE 2019; 220:943-953. [PMID: 33395816 DOI: 10.1016/j.chemosphere.2018.12.105] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2018] [Revised: 12/11/2018] [Accepted: 12/14/2018] [Indexed: 05/13/2023]
Abstract
This study investigates the contamination of groundwater by chromium and fluoride around leather tanning industries. Major ions, chromium, δ53Cr/δ52Cr and fluoride were analyzed by advanced analytical methods. High degree of variation was observed in the concentration of chloride in groundwater, which ranged between 205 and 3310 mg/L, around 56% of the samples were recorded above the acceptable limit indicating the quality of groundwater is fresh to saline and it could be due to mixing of tannery effluents with freshwater aquifers. The chromium in the groundwater around 40% of the sampling wells exceeds the permissible limit whereas, 37% of wells were with fluoride above the accepted limit. Geochemical modelling using Phreeqc suggest that the saturation index of minerals such as calcite, dolomite, fluoride, gypsum and anorthite is affected by precipitation, dissolution and ion exchange processes. Concentration of chromium isotopes δ53Cr and δ52Cr reveals the source of Cr in the groundwater is more likely from tannery effluents. Accumulation of fluoride in groundwater is contributed by bedrock, charnockite, granite, epidote hornblende gneiss, fissile hornblende biotite gneiss in the study area. Groundwater contamination in this area is caused by both natural as well as anthropogenic sources. Around 37% of the samples exceeds HQI limit (HQI>1), which indicates possible health problems to the public upon prolonged use of untreated groundwater for drinking. To overcome this situation, it's essential to improve the performance of the effluent treatment plants and recharge structure to recover the quality of groundwater.
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Affiliation(s)
- G Kanagaraj
- Department of Geology, Anna University, Chennai, 600025, India.
| | - L Elango
- Department of Geology, Anna University, Chennai, 600025, India.
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13
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Zhang Q, Amor K, Galer SJG, Thompson I, Porcelli D. Using stable isotope fractionation factors to identify Cr(VI) reduction pathways: Metal-mineral-microbe interactions. WATER RESEARCH 2019; 151:98-109. [PMID: 30594094 DOI: 10.1016/j.watres.2018.11.088] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2018] [Revised: 11/26/2018] [Accepted: 11/30/2018] [Indexed: 06/09/2023]
Abstract
Microbes interact with metals and minerals in the environment altering their physical and chemical states, whilst in turn metals and minerals impact on microbial growth, activity and survival. The interactions between bacteria and dissolved chromium in the presence of iron minerals, and their impact on Cr isotope variations, were investigated. Cr(VI) reduction experiments were conducted with two bacteria, Pseudomonas fluorescens LB 300 and Shewanella oneidensis MR-1, in the presence of two iron oxide minerals, goethite and hematite. Both minerals were found to inhibit the rates of Cr(VI) reduction by Pseudomonas, but accelerated those of Shewanella. The Cr isotopic fractionation factors generated by Shewanella were independent of the presence of the minerals (ε = -2.3‰). For Pseudomonas, the ε value was the same in both the presence and absence of goethite (-3.3‰); although, it was much higher (ε = -4.3‰) in the presence of hematite. The presence of aqueous Fe(III) in solution had no detectable impact on either bacterial Cr reduction rates nor isotopic fractionation factors. The presence of aqueous Fe(II) induced rapid abiotic reduction of Cr(VI). The different effects that the presence of Fe minerals had on the Cr fractionation factors and reduction rates of the different bacterial species may be attributed to the way each bacteria attached to the minerals and their different reduction pathways. SEM images confirmed that Pseudomonas cells were much more tightly packed on the mineral surfaces than were Shewanella. The images also confirmed that Shewanella oneidensis MR-1 produced nanowires. The results suggest that the dominant Cr(VI) reduction pathway for Pseudomonas fluorescens LB 300 may have been through membrane-bound enzymes, whilst for Shewanella oneidensis MR-1 it was probably via extracellular electron transfer. Since different minerals impact differentially on bacterial Cr(VI) reduction and isotope fractionation, variations of mineralogies and the associated changes of bacterial communities should be taken into consideration when using Cr isotopes to quantify Cr redox behaviour in the environment.
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Affiliation(s)
- Qiong Zhang
- Department of Earth Sciences, University of Oxford, Oxford, United Kingdom.
| | - Ken Amor
- Department of Earth Sciences, University of Oxford, Oxford, United Kingdom
| | - Stephen J G Galer
- Max Planck Institute for Chemistry, Climate Geochemistry Department, 55128, Mainz, Germany
| | - Ian Thompson
- Department of Engineering Science, University of Oxford, Oxford, United Kingdom
| | - Don Porcelli
- Department of Earth Sciences, University of Oxford, Oxford, United Kingdom
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14
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Lu YZ, Chen GJ, Bai YN, Fu L, Qin LP, Zeng RJ. Chromium isotope fractionation during Cr(VI) reduction in a methane-based hollow-fiber membrane biofilm reactor. WATER RESEARCH 2018; 130:263-270. [PMID: 29241112 DOI: 10.1016/j.watres.2017.11.045] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2017] [Revised: 10/23/2017] [Accepted: 11/22/2017] [Indexed: 06/07/2023]
Abstract
Chromium (Cr) isotope fractionation analysis is a promising tool for monitoring Cr(VI) reduction in natural aqueous systems. In addition, large amounts of CH4 in natural aqueous sediments are oxidized to CO2 through methanotrophs, thereby mitigating emissions to the atmosphere. However, the investigations on the Cr(VI) reduction process with methanotrophs, and the associated Cr isotope fractionation patterns are scarce. In this study, we have shown that Cr(VI) reduction can occur in the presence of CH4 as the sole electron donor in a hollow-fiber membrane reactor (HfMBR) after direct bacteria enrichment from sediment samples. Products of the methane oxidation by the methanotrophs are used by microbes to reduce Cr(VI) as shown by the progressive increase in δ53Cr with time in the CH4 feed reactor. The isotope fractionation factor (ε) of -2.62 ± 0.20‰ was obtained from the application of the Rayleigh distillation model. The results of Cr isotope fractionation analysis also explained the decrease of Cr(VI) concentration in the N2 feed reactor, where the δ53Cr values remained steady in the first two weeks but significantly increased in the last two weeks, indicating that physical adsorption and subsequent Cr(VI) reduction occurred. This study extended the application of Cr isotope fractionation, showing the suitability of this method for clarifying different Cr(VI) removal processes.
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Affiliation(s)
- Yong-Ze Lu
- CAS Key Laboratory for Urban Pollutant Conversion, Department of Chemistry, University of Science & Technology of China, Hefei 230026, China
| | - Guo-Jun Chen
- CAS Key Laboratory of Crust-Mantle Materials and Environments, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China
| | - Ya-Nan Bai
- CAS Key Laboratory for Urban Pollutant Conversion, Department of Chemistry, University of Science & Technology of China, Hefei 230026, China; Advanced Laboratory for Environmental Research and Technology, USTC-CityU, Suzhou 215123, China
| | - Liang Fu
- CAS Key Laboratory for Urban Pollutant Conversion, Department of Chemistry, University of Science & Technology of China, Hefei 230026, China
| | - Li-Ping Qin
- CAS Key Laboratory of Crust-Mantle Materials and Environments, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China
| | - Raymond Jianxiong Zeng
- CAS Key Laboratory for Urban Pollutant Conversion, Department of Chemistry, University of Science & Technology of China, Hefei 230026, China; Advanced Laboratory for Environmental Research and Technology, USTC-CityU, Suzhou 215123, China.
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15
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Saad EM, Wang X, Planavsky NJ, Reinhard CT, Tang Y. Redox-independent chromium isotope fractionation induced by ligand-promoted dissolution. Nat Commun 2017; 8:1590. [PMID: 29150598 PMCID: PMC5693864 DOI: 10.1038/s41467-017-01694-y] [Citation(s) in RCA: 55] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Accepted: 10/09/2017] [Indexed: 11/24/2022] Open
Abstract
The chromium (Cr) isotope system has emerged as a potential proxy for tracing the Earth’s atmospheric evolution based on a redox-dependent framework for Cr mobilization and isotope fractionation. Although studies have demonstrated that redox-independent pathways can also mobilize Cr, no quantitative constraints exist on the associated isotope fractionations. Here we survey the effects of common environmental ligands on the dissolution of Cr(III)-(oxy)hydroxide solids and associated Cr isotope fractionation. For a variety of organic acids and siderophores, δ53Cr values of dissolved Cr(III) are −0.27 to 1.23‰, within the range of previously observed Cr isotope signatures in rock records linked to Cr redox cycling. Thus, ligand-promoted dissolution of Cr-containing solids, a redox-independent process, must be taken into account when using sedimentary Cr isotope signatures to diagnose atmospheric oxygen levels. This work provides a step towards establishing a more robust framework for using Cr isotopes to track the evolution of the Earth’s atmosphere. The chromium (Cr) isotope system has emerged as a potential proxy for tracing Earth’s atmospheric evolution based on a redox-dependent framework. Here the authors show that ligand-complexation, a redox-independent process, must be considered when using Cr isotope signatures to diagnose atmospheric oxygen levels.
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Affiliation(s)
- Emily M Saad
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA, 30332, USA
| | - Xiangli Wang
- Department of Geology and Geophysics, Yale University, New Haven, CT, 06511, USA
| | - Noah J Planavsky
- Department of Geology and Geophysics, Yale University, New Haven, CT, 06511, USA
| | - Christopher T Reinhard
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA, 30332, USA
| | - Yuanzhi Tang
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA, 30332, USA.
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16
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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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17
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Čadková E, Chrastný V. Isotope evidence of hexavalent chromium stability in ground water samples. CHEMOSPHERE 2015; 138:74-80. [PMID: 26037819 DOI: 10.1016/j.chemosphere.2015.05.057] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2014] [Revised: 05/14/2015] [Accepted: 05/19/2015] [Indexed: 06/04/2023]
Abstract
Chromium stable isotopes are of interest in many geochemical studies as a tool to identify Cr(VI) reduction and/or dilution in groundwater aquifers. For such studies the short term stability of Cr(VI) in water samples is required before the laboratory analyses can be carried out. Here the short term stability of Cr(VI) in groundwater samples was studied using an isotope approach. Based on commonly available methods for Cr(VI) stabilization, water samples were filtered and the pH value was adjusted to be equal to or greater than 8 before Cr isotope analysis. Based on our Cr isotope data (expressed as δ(53)CrNIST979), Cr(VI) was found to be unstable over short time periods in anthropogenically contaminated groundwater samples regardless of water treatment (e.g., pH adjustment, different storage temperatures). Based on our laboratory experiments, δ(53)CrNIST979 of the Cr(VI) pool was found to be unstable in the presence of dissolved Fe(II), Mn(IV) and/or SO2. Threshold concentrations of Fe(II) causing Cr(VI) reduction range between 10 mg L(-1) and 100 mg L(-1)and less than 1 mg L(-1) for Mn. Hence our isotope data show that water samples containing Cr(VI) should be processed on-site through anion column chemistry to avoid any isotope shifts.
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Affiliation(s)
- Eva Čadková
- Czech Geological Survey, Geologická 6, 152 00 Prague 5, Czech Republic.
| | - Vladislav Chrastný
- Faculty of Environmental Sciences, Czech University of Life Sciences Prague, Kamýcká 129, 165 21 Prague 6, Czech Republic.
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18
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Xu F, Ma T, Zhou L, Hu Z, Shi L. Chromium isotopic fractionation during Cr(VI) reduction by Bacillus sp. under aerobic conditions. CHEMOSPHERE 2015; 130:46-51. [PMID: 25777078 DOI: 10.1016/j.chemosphere.2015.02.033] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2014] [Revised: 02/04/2015] [Accepted: 02/11/2015] [Indexed: 06/04/2023]
Abstract
This study investigated the fractionation of chromium isotopes during chromium reduction by Bacillus sp. under aerobic condition, variable carbon source (glucose) concentration (0, 0.1, 1, 2.5 and 10mM), and incubation temperatures (4, 15, 25 and 37°C). The results revealed that the δ(53)Cr values in the residual Cr(VI) increased with the degree of Cr reduction, and followed a Rayleigh fractionation model. The addition of glucose only slightly affected cell-specific Cr(VI) reduction rates (cSRR). However, the value of ε (2.00±0.21‰) in the experiments with different concentrations of glucose (0.1, 1, 2.5 and 10mM) was smaller than that from the experiment without glucose (3.74±0.16‰). The results indicated that the cell-specific reduction rate is not the sole control on the degree of isotopic fractionation, and different metabolic pathways would result in differing degrees of Cr isotopic fractionation. The cSRR decreased with decreasing temperature, showing that the values of ε were 7.62±0.36‰, 4.59±0.28‰, 3.09±0.16‰ and 1.99±0.23‰ at temperatures of 4, 15, 25 and 37°C, respectively. It shown that increasing cSRR linked to decreasing fractionations has been associated with increasing temperatures. Overall, our results revealed that temperature is a primary factor affecting Cr isotopic fractionation under microbial actions.
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Affiliation(s)
- Fen Xu
- State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074, China; School of Environmental Studies, China University of Geosciences, Wuhan 430074, China
| | - Teng Ma
- State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074, China; School of Environmental Studies, China University of Geosciences, Wuhan 430074, China.
| | - Lian Zhou
- State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, China.
| | - Zhifang Hu
- State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, China
| | - Liu Shi
- Guangxi Transportation Research Institute, Nanning 530007, China
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19
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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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20
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Jamieson-Hanes JH, Amos RT, Blowes DW, Ptacek CJ. Dual Mechanism Conceptual Model for Cr Isotope Fractionation during Reduction by Zerovalent Iron under Saturated Flow Conditions. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2015; 49:5467-5475. [PMID: 25839086 DOI: 10.1021/es506223a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Chromium isotope analysis is rapidly becoming a valuable complementary tool for tracking Cr(VI) treatment in groundwater. Evaluation of various treatment materials has demonstrated that the degree of isotope fractionation is a function of the reaction mechanism, where reduction of Cr(VI) to Cr(III) induces the largest fractionation. However, it has also been observed that uniform flow conditions can contribute complexity to isotope measurements. Here, laboratory batch and column experiments were conducted to assess Cr isotope fractionation during Cr(VI) reduction by zerovalent iron under both static and saturated flow conditions. Isotope measurements were accompanied by traditional aqueous geochemical measurements (pH, Eh, concentrations) and solid-phase analysis by scanning electron microscopy and X-ray absorption spectroscopy. Increasing δ(53)Cr values were associated with decreasing Cr(VI) concentrations, which indicates reduction; solid-phase analysis showed an accumulation of Cr(III) on the iron. Reactive transport modeling implemented a dual mechanism approach to simulate the fractionation observed in the experiments. The faster heterogeneous reaction pathway was associated with minimal fractionation (ε=-0.2‰), while the slower homogeneous pathway exhibited a greater degree of fractionation (ε=-0.9‰ for the batch experiment, and ε=-1.5‰ for the column experiment).
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Affiliation(s)
- Julia H Jamieson-Hanes
- †Department of Earth and Environmental Sciences, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1, Canada
| | - Richard T Amos
- ‡Department of Earth Sciences, Carleton University, 1125 Colonel By Drive, Ottawa, ON K1S 5B6, Canada
| | - David W Blowes
- †Department of Earth and Environmental Sciences, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1, Canada
| | - Carol J Ptacek
- †Department of Earth and Environmental Sciences, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1, Canada
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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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Izbicki JA. Fate of nutrients in shallow groundwater receiving treated septage, Malibu, CA. GROUND WATER 2014; 52 Suppl 1:218-33. [PMID: 24902718 PMCID: PMC4265202 DOI: 10.1111/gwat.12194] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2013] [Accepted: 02/12/2014] [Indexed: 05/22/2023]
Abstract
Treated wastewater discharged from more than 400 onsite wastewater treatment systems (OWTS) near the Civic Center area of Malibu, California, 40 km west of downtown Los Angeles, composes 28% of the recharge to a 3.4 km(2) alluvial aquifer. On the basis of δ(18) O and δD data, the fraction of wastewater in some samples was >70%. Ammonium and nitrate concentrations in water from 15 water-table wells sampled in July 2009 and April 2010 ranged from <0.01 to 12 milligrams per liter as nitrogen (mg/L as N), and from <0.01 to 11 mg/L as N, respectively. Chemical and isotopic data (δ(15) N of ammonium and nitrate, and δ(18) O of nitrate) show two processes remove nitrogen discharged from OWTS. Where groundwater was reducing, sorption of ammonium resulted in 30 to 50% nitrogen removal. Where groundwater was initially oxic, nitrification with subsequent denitrification as reducing conditions developed, resulted in up to 60% nitrogen removal. Nitrogen removal through sorption dominated during the cooler April sample period, and denitrification dominated during the warmer July sample period. The combination of mixing and nitrogen removal due to denitrification, sorption, and volatilization produces a δ(15) N apparent fractionation factor (εapp = -5), that can be explained using laboratory-derived fractionation factors (ε) for the individual processes. Phosphate concentrations ranged from < 0.04 to 2 mg/L as phosphorous. Sorption to iron oxides on the surfaces of mineral grains at near-neutral pH's removed some phosphate; however, little removal occurred at more alkaline pH's (>7.3).
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Affiliation(s)
- John A Izbicki
- Water Resources, U.S. Geological Survey, 4165 Spruance Road, Suite 200, San Diego, CA 92101; (619) 225-6131; fax: (619) 225-6101.
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Pyrosequencing analysis of bacterial community and assembly in activated sludge samples from different geographic regions in China. Appl Microbiol Biotechnol 2014; 98:9119-28. [DOI: 10.1007/s00253-014-5920-3] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2014] [Revised: 06/25/2014] [Accepted: 06/27/2014] [Indexed: 10/24/2022]
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Novak M, Chrastny V, Cadkova E, Farkas J, Bullen TD, Tylcer J, Szurmanova Z, Cron M, Prechova E, Curik J, Stepanova M, Pasava J, Erbanova L, Houskova M, Puncochar K, Hellerich LA. Common occurrence of a positive δ53Cr shift in Central European waters contaminated by geogenic/industrial chromium relative to source values. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2014; 48:6089-6096. [PMID: 24779992 DOI: 10.1021/es405615h] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Carcinogenic effects of hexavalent chromium in waters are of concern in many countries worldwide. We explored Cr isotope systematics at 11 sites in the Czech Republic and Poland. Geogenic Cr pollution was associated with serpentinite bodies at former convergent plate margins, while anthropogenic Cr pollution resulted from electroplating, tanning, and the chemical industry. Cr(VI) concentration in geogenic waters was less than 40 ppb. Anthropogenic waters contained up to 127,000 ppb Cr(VI). At both geogenic and anthropogenic sites, where known, the source of pollution had a low δ53Cr (<1‰). δ53Cr of geogenic and anthropogenic waters was up to 3.9 and 5.8‰, respectively. At both serpentinite-dominated and industrial sites, δ53Cr(VI)aq was shifted toward higher values, compared to the pollution source. At the industrial sites, this positive δ53Cr shift was related to Cr(VI) reduction, a process known to fractionate Cr isotopes. At geogenic sites, the origin of high δ53Cr(VI)aq is tentatively ascribed to preferential release of 53Cr during oxidation of soil Cr(III) and its mobilization to water. δ53Cr(VI) of industrially contaminated waters was significantly higher (p<0.001) compared to δ53Cr of waters carrying geogenic Cr(VI), implying that either the effective fractionation factor or process extent was greater for Cr(VI) reduction than for Cr(III) oxidation.
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Affiliation(s)
- Martin Novak
- Division of Geochemistry and Laboratories, Czech Geological Survey , Geologicka 6, 152 00 Prague 5, Czech Republic
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Druhan JL, Maher K. A Model Linking Stable Isotope Fractionation to Water Flux and Transit Times in Heterogeneous Porous Media. ACTA ACUST UNITED AC 2014. [DOI: 10.1016/j.proeps.2014.08.054] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Jamieson-Hanes JH, Amos RT, Blowes DW. Reactive transport modeling of chromium isotope fractionation during Cr(VI) reduction. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2012; 46:13311-13316. [PMID: 23153412 DOI: 10.1021/es3046235] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Chromium isotope fractionation is indicative of mass-transfer processes, such as reduction of Cr(VI) to Cr(III) during groundwater remediation. Laboratory experiments comparing batch and column treatment of Cr(VI) using organic carbon suggest that the associated isotope fractionation may be influenced by solute-transport mechanisms. These batch and column experiments were simulated using the reactive transport model MIN3P to further evaluate the effects of Cr reduction and transport on isotope fractionation under saturated flow conditions. Simulation of the batch experiment provided a good fit to the experimental data, where a fractionation factor (α₅₃) of 0.9965 was attributed to a single, dominant Cr(VI) removal mechanism. Calibration of the column simulations to the experimental results suggested the presence of a second, more rapid Cr(VI) removal mechanism with α₅₃ = 0.9992. Results from this study demonstrate that the interpretation of Cr isotope fractionation during reduction can be complex, particularly where multiple removal mechanisms are evident. Reactive transport modeling of Cr isotope fractionation can provide a quantitative assessment of the contaminant removal mechanisms, thus improving the application of Cr isotope measurements as a tool to track Cr(VI) migration and attenuation in groundwater.
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Affiliation(s)
- Julia H Jamieson-Hanes
- Department of Earth and Environmental Sciences, University of Waterloo, Waterloo, ON N2L 3G1, Canada
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Jamieson-Hanes JH, Gibson BD, Lindsay MBJ, Kim Y, Ptacek CJ, Blowes DW. Chromium isotope fractionation during reduction of Cr(VI) under saturated flow conditions. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2012; 46:6783-6789. [PMID: 22676583 DOI: 10.1021/es2042383] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Chromium isotopes are potentially useful indicators of Cr(VI) reduction reactions in groundwater flow systems; however, the influence of transport on Cr isotope fractionation has not been fully examined. Laboratory batch and column experiments were conducted to evaluate isotopic fractionation of Cr during Cr(VI) reduction under both static and controlled flow conditions. Organic carbon was used to reduce Cr(VI) in simulated groundwater containing 20 mg L(-1) Cr(VI) in both batch and column experiments. Isotope measurements were performed on dissolved Cr on samples from the batch experiments, and on effluent and profile samples from the column experiment. Analysis of the residual solid-phase materials by scanning electron microscopy (SEM) and by X-ray absorption near edge structure (XANES) spectroscopy confirmed association of Cr(III) with organic carbon in the column solids. Decreases in dissolved Cr(VI) concentrations were coupled with increases in δ(53)Cr, indicating that Cr isotope enrichment occurred during reduction of Cr(VI). The δ(53)Cr data from the column experiment was fit by linear regression yielding a fractionation factor (α) of 0.9979, whereas the batch experiments exhibited Rayleigh-type isotope fractionation (α = 0.9965). The linear characteristic of the column δ(53)Cr data may reflect the contribution of transport on Cr isotope fractionation.
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Affiliation(s)
- Julia H Jamieson-Hanes
- Department of Earth and Environmental Sciences, University of Waterloo, 200 University Ave W, Waterloo, ON N2L 3G1, Canada
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Basu A, Johnson TM. Determination of hexavalent chromium reduction using Cr stable isotopes: isotopic fractionation factors for permeable reactive barrier materials. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2012; 46:5353-5360. [PMID: 22424120 DOI: 10.1021/es204086y] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Cr stable isotope measurements can provide improved estimates of the extent of Cr(VI) reduction to less toxic Cr(III). The relationship between observed (53)Cr/(52)Cr ratio shifts and the extent of reduction can be calibrated by determining the isotopic fractionation factor for relevant reactions. Permeable reactive barriers (PRB) made of Fe(0) and in situ redox manipulation (ISRM) zones effectively remediate Cr-contaminated aquifers. Here, we determine the isotopic fractionations for dominant reductants in reactive barriers and reduced sediments obtained from an ISRM zone at the US DOE's Hanford site. In all cases, significant isotopic fractionation was observed; fractionation (expressed as ε) was -3.91‰ for Fe(II)-doped goethite, -2.11‰ for FeS, -2.65‰ for green rust, -2.67‰ for FeCO(3), and -3.18‰ for ISRM zone sediments. These results provide a better calibration of the relationship between Cr isotope ratios and the extent of Cr(VI) reduction and aid in interpretation of Cr isotope data from systems with reactive barriers.
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Affiliation(s)
- Anirban Basu
- Department of Geology, University of Illinois at Urbana-Champaign, 208 Natural History Building, 1301 West Green Street, Urbana, Illinois 61801, United States.
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Wanner C, Zink S, Eggenberger U, Mäder U. Assessing the Cr(VI) reduction efficiency of a permeable reactive barrier using Cr isotope measurements and 2D reactive transport modeling. JOURNAL OF CONTAMINANT HYDROLOGY 2012; 131:54-63. [PMID: 22343010 DOI: 10.1016/j.jconhyd.2012.01.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/29/2011] [Revised: 01/07/2012] [Accepted: 01/13/2012] [Indexed: 05/31/2023]
Abstract
In Thun, Switzerland, a permeable reactive barrier (PRB) for Cr(VI) reduction by gray cast iron was installed in May 2008. The PRB is composed of a double array of vertical piles containing iron shavings and gravel. The aquifer in Thun is almost saturated with dissolved oxygen and the groundwater flow velocities are ca. 10-15m/day. Two years after PRB installation Cr(VI) concentrations still permanently exceed the Swiss threshold value for contaminated sites downstream of the barrier at selected localities. Groundwater δ(53/52)Cr(SRM979) measurements were used to track Cr(VI) reduction induced by the PRB. δ(53/52)Cr(SRM979) values of two samples downstream of the PRB showed a clear fractionation towards more positive values compared to four samples from the hotspot, which is clear evidence of Cr(VI) reduction induced by the PRB. Another downstream sample did not show a shift to more positive δ(53/52)Cr(SRM979) values. Because this latter location correlates with the highest downstream Cr(VI) concentration it is proposed that a part of the Cr(VI) plume is bypassing the barrier. Using a Rayleigh fractionation model a minimum present-day overall Cr(VI) reduction efficiency of ca. 15% was estimated. A series of 2D model simulations, including the fractionation of Cr isotopes, confirm that only a PRB bypass of parts of the Cr(VI) plume can lead to the observed values. Additionally, the simulations revealed that the proposed bypass occurs due to an insufficient permeability of the individual PRB piles. It is concluded that with this type of PRB a complete and long-lasting Cr(VI) reduction is extremely difficult to achieve for Cr(VI) contaminations located in nearly oxygen and calcium carbonate saturated aquifer in a regime of high groundwater velocities. Additional remediation action would limit the environmental impact and allow to reach target concentrations.
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Affiliation(s)
- Christoph Wanner
- Institute of Geological Sciences, University of Bern, Switzerland
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Stable Isotopes of Transition and Post-Transition Metals as Tracers in Environmental Studies. ADVANCES IN ISOTOPE GEOCHEMISTRY 2012. [DOI: 10.1007/978-3-642-10637-8_10] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
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Johnson TM. Stable Isotopes of Cr and Se as Tracers of Redox Processes in Earth Surface Environments. ADVANCES IN ISOTOPE GEOCHEMISTRY 2012. [DOI: 10.1007/978-3-642-10637-8_9] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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Raddatz AL, Johnson TM, McLing TL. Cr stable isotopes in Snake River Plain aquifer groundwater: evidence for natural reduction of dissolved Cr(VI). ENVIRONMENTAL SCIENCE & TECHNOLOGY 2011; 45:502-507. [PMID: 21121656 DOI: 10.1021/es102000z] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
At Idaho National Laboratory, Cr(VI) concentrations in a groundwater plume once exceeded regulatory limits in some monitoring wells but have generally decreased over time. This study used Cr stable isotope measurements to determine if part of this decrease resulted from removal of Cr(VI) via reduction to insoluble Cr(III). Although waters in the study area contain dissolved oxygen, the basalt host rock contains abundant Fe(II) and may contain reducing microenvironments or aerobic microbes that reduce Cr(VI). In some contaminated locations, (53)Cr/(52)Cr ratios are close to that of the contaminant source, indicating a lack of Cr(VI) reduction. In other locations, ratios are elevated. Part of this shift may be caused by mixing with natural background Cr(VI), which is present at low concentrations but in some locations has elevated (53)Cr/(52)Cr. Some contaminated wells have (53)Cr/(52)Cr ratios greater than the maximum attainable by mixing between the inferred contaminant and the range of natural background observed in several uncontaminated wells, suggesting that Cr(VI) reduction has occurred. Definitive proof of reduction would require additional evidence. Depth profiles of (53)Cr/(52)Cr suggest that reduction occurs immediately below the water table, where basalts are likely least weathered and most reactive, and is weak or nonexistent at greater depth.
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Affiliation(s)
- Amanda L Raddatz
- Department of Geology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
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