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Schwab L, Gallati N, Reiter SM, Kimber RL, Kumar N, McLagan DS, Biester H, Kraemer SM, Wiederhold JG. Mercury Isotope Fractionation during Dark Abiotic Reduction of Hg(II) by Dissolved, Surface-Bound, and Structural Fe(II). ENVIRONMENTAL SCIENCE & TECHNOLOGY 2023; 57:15243-15254. [PMID: 37748105 PMCID: PMC10569049 DOI: 10.1021/acs.est.3c03703] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2023] [Revised: 09/04/2023] [Accepted: 09/07/2023] [Indexed: 09/27/2023]
Abstract
Stable mercury (Hg) isotope ratios are an emerging tracer for biogeochemical transformations in environmental systems, but their application requires knowledge of isotopic enrichment factors for individual processes. We investigated Hg isotope fractionation during dark, abiotic reduction of Hg(II) by dissolved iron(Fe)(II), magnetite, and Fe(II) sorbed to boehmite or goethite by analyzing both the reactants and products of laboratory experiments. For homogeneous reduction of Hg(II) by dissolved Fe(II) in continuously purged reactors, the results followed a Rayleigh distillation model with enrichment factors of -2.20 ± 0.16‰ (ε202Hg) and 0.21 ± 0.02‰ (E199Hg). In closed system experiments, allowing reequilibration, the initial kinetic fractionation was overprinted by isotope exchange and followed a linear equilibrium model with -2.44 ± 0.17‰ (ε202Hg) and 0.34 ± 0.02‰ (E199Hg). Heterogeneous Hg(II) reduction by magnetite caused a smaller isotopic fractionation (-1.38 ± 0.07 and 0.13 ± 0.01‰), whereas the extent of isotopic fractionation of the sorbed Fe(II) experiments was similar to the kinetic homogeneous case. Small mass-independent fractionation of even-mass Hg isotopes with 0.02 ± 0.003‰ (E200Hg) and ≈ -0.02 ± 0.01‰ (E204Hg) was consistent with theoretical predictions for the nuclear volume effect. This study contributes significantly to the database of Hg isotope enrichment factors for specific processes. Our findings show that Hg(II) reduction by dissolved Fe(II) in open systems results in a kinetic MDF with a larger ε compared to other abiotic reduction pathways, and combining MDF with the observed MIF allows the distinction from photochemical or microbial Hg(II) reduction pathways.
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Affiliation(s)
- Lorenz Schwab
- Department
of Environmental Geosciences, Centre for Microbiology and Environmental
Systems Science, University of Vienna, Josef-Holaubek-Platz 2, 1090 Vienna, Austria
- Doctoral
School in Microbiology and Environmental Science, University of Vienna, 1030 Vienna, Austria
- Environmental
Engineering Institute IIE-ENAC, Soil Biogeochemistry Laboratory, École Polytechnique Fédérale
de Lausanne (EPFL), Route
des Ronquos 86, 1951 Sion, Switzerland
| | - Niklas Gallati
- Department
of Environmental Geosciences, Centre for Microbiology and Environmental
Systems Science, University of Vienna, Josef-Holaubek-Platz 2, 1090 Vienna, Austria
| | - Sofie M. Reiter
- Department
of Environmental Geosciences, Centre for Microbiology and Environmental
Systems Science, University of Vienna, Josef-Holaubek-Platz 2, 1090 Vienna, Austria
| | - Richard L. Kimber
- Department
of Environmental Geosciences, Centre for Microbiology and Environmental
Systems Science, University of Vienna, Josef-Holaubek-Platz 2, 1090 Vienna, Austria
| | - Naresh Kumar
- Department
of Environmental Geosciences, Centre for Microbiology and Environmental
Systems Science, University of Vienna, Josef-Holaubek-Platz 2, 1090 Vienna, Austria
- Soil
Chemistry and Chemical Soil Quality Group, Department of Environmental
Sciences, University of Wageningen, Droevendaalsesteeg 3a, 6708 Wageningen, Netherlands
| | - David S. McLagan
- Environmental
Geochemistry Group, Institute of Geoecology, Technische Universität Braunschweig, Langer Kamp 19c, 38106 Braunschweig, Germany
- Department
of Geological Sciences and Geological Engineering, Queen’s University, Kingston, Ontario K7L 3N6, Canada
- School
of Environmental Studies, Queen’s
University, Kingston, Ontario K7L 3N6, Canada
| | - Harald Biester
- Environmental
Geochemistry Group, Institute of Geoecology, Technische Universität Braunschweig, Langer Kamp 19c, 38106 Braunschweig, Germany
| | - Stephan M. Kraemer
- Department
of Environmental Geosciences, Centre for Microbiology and Environmental
Systems Science, University of Vienna, Josef-Holaubek-Platz 2, 1090 Vienna, Austria
| | - Jan G. Wiederhold
- Department
of Environmental Geosciences, Centre for Microbiology and Environmental
Systems Science, University of Vienna, Josef-Holaubek-Platz 2, 1090 Vienna, Austria
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McLagan DS, Schwab L, Wiederhold JG, Chen L, Pietrucha J, Kraemer SM, Biester H. Demystifying mercury geochemistry in contaminated soil-groundwater systems with complementary mercury stable isotope, concentration, and speciation analyses. ENVIRONMENTAL SCIENCE. PROCESSES & IMPACTS 2022; 24:1406-1429. [PMID: 34981096 PMCID: PMC9491299 DOI: 10.1039/d1em00368b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Interpretation of mercury (Hg) geochemistry in environmental systems remains a challenge. This is largely associated with the inability to identify specific Hg transformation processes and species using established analytical methods in Hg geochemistry (total Hg and Hg speciation). In this study, we demonstrate the improved Hg geochemical interpretation, particularly related to process tracing, that can be achieved when Hg stable isotope analyses are complemented by a suite of more established methods and applied to both solid- (soil) and liquid-phases (groundwater) across two Hg2+-chloride (HgCl2) contaminated sites with distinct geological and physicochemical properties. This novel approach allowed us to identify processes such as Hg2+ (i.e., HgCl2) sorption to the solid-phase, Hg2+ speciation changes associated with changes in groundwater level and redox conditions (particularly in the upper aquifer and capillary fringe), Hg2+ reduction to Hg0, and dark abiotic redox equilibration between Hg0 and Hg(II). Hg stable isotope analyses play a critical role in our ability to distinguish, or trace, these in situ processes. While we caution against the non-critical use of Hg isotope data for source tracing in environmental systems, due to potentially variable source signatures and overprinting by transformation processes, our study demonstrates the benefits of combining multiple analytical approaches, including Hg isotope ratios as a process tracer, to obtain an improved picture of the enigmatic geochemical behavior and fate of Hg at contaminated legacy sites.
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Affiliation(s)
- D S McLagan
- Institute for Geoecology, Technical University of Braunschweig, 38106 Braunschweig, Germany.
- Department of Physical & Environmental Sciences, University of Toronto Scarborough, Toronto, M1C1A4, Canada
| | - L Schwab
- Department of Environmental Geosciences, Centre for Microbiology and Environmental Systems Science, University of Vienna, 1090 Vienna, Austria
| | - J G Wiederhold
- Department of Environmental Geosciences, Centre for Microbiology and Environmental Systems Science, University of Vienna, 1090 Vienna, Austria
| | - L Chen
- Institute for Geoecology, Technical University of Braunschweig, 38106 Braunschweig, Germany.
| | - J Pietrucha
- Institute for Geoecology, Technical University of Braunschweig, 38106 Braunschweig, Germany.
| | - S M Kraemer
- Department of Environmental Geosciences, Centre for Microbiology and Environmental Systems Science, University of Vienna, 1090 Vienna, Austria
| | - H Biester
- Institute for Geoecology, Technical University of Braunschweig, 38106 Braunschweig, Germany.
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3
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Zhang S, Peiffer S, Liao X, Yang Z, Ma X, He D. Sulfidation of ferric (hydr)oxides and its implication on contaminants transformation: a review. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 816:151574. [PMID: 34798096 DOI: 10.1016/j.scitotenv.2021.151574] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Revised: 11/05/2021] [Accepted: 11/05/2021] [Indexed: 06/13/2023]
Abstract
Rapid industrialization and urbanization have resulted in elevated concentrations of contaminants in the groundwaters and subsurface soils, posing a growing hazard to humans and ecosystems. The transformation of most contaminants is closely linked to the mineralogy of ferric (hydr)oxides. Sulfidation of ferric (hydr)oxides is one of the most significant biogeochemical reactions in the anoxic environments, causing reductive dissolution and recrystallization of ferric (hydr)oxides and further affecting the transformation of iron-associated contaminants. This paper provides a comprehensive review on the sulfidation process of ferric (hydr)oxides and the transformation of relevant contaminants. This review presents detailed reaction mechanisms between ferric (hydr)oxides and dissolved sulfide, and elucidates the factors (e.g. crystallinity of ferric (hydr)oxides, the ratio of sulfide concentration to the surface area concentration of ferric (hydr)oxides) that control the formation of surface associated Fe(II), iron sulfide minerals, as well as transformation of secondary minerals. Then, we summarized the transformation mechanisms of a variety of typical environmentally relevant contaminants existing in groundwater and subsurface soils, including heavy metals, metal(loid) oxyanions (arsenic, antimony, chromium), radionuclides (uranium, technetium), organic contaminants and phosphate/nitrate species. The general mechanisms of contaminant transformation involve a combination of release, reduction and re-adsorption/incorporation processes, the specific pathway of which is highly dependent on the properties of the contaminant itself and the extent of sulfidation. Moreover, the challenge of extending our knowledge towards in situ remediation, as well as further research needs are identified.
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Affiliation(s)
- Shaojian Zhang
- Key Laboratory for City Cluster Environmental Safety and Green Development of the Ministry of Education, Institute of Environmental and Ecological Engineering, Guangdong University of Technology, Guangzhou 510006, China; Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou 511458, China
| | - Stefan Peiffer
- BayCEER, Department of Hydrology, University of Bayreuth, D-95440 Bayreuth, Germany
| | - Xiaoting Liao
- Key Laboratory for City Cluster Environmental Safety and Green Development of the Ministry of Education, Institute of Environmental and Ecological Engineering, Guangdong University of Technology, Guangzhou 510006, China
| | - Zhengheng Yang
- Key Laboratory for City Cluster Environmental Safety and Green Development of the Ministry of Education, Institute of Environmental and Ecological Engineering, Guangdong University of Technology, Guangzhou 510006, China
| | - Xiaoming Ma
- Key Laboratory for City Cluster Environmental Safety and Green Development of the Ministry of Education, Institute of Environmental and Ecological Engineering, Guangdong University of Technology, Guangzhou 510006, China
| | - Di He
- Key Laboratory for City Cluster Environmental Safety and Green Development of the Ministry of Education, Institute of Environmental and Ecological Engineering, Guangdong University of Technology, Guangzhou 510006, China; Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou 511458, China.
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4
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Huang Y, Wang M, Gong Y, Zeng EY. Efficient removal of mercury from simulated groundwater using thiol-modified graphene oxide/Fe-Mn composite in fixed-bed columns: Experimental performance and mathematical modeling. THE SCIENCE OF THE TOTAL ENVIRONMENT 2020; 714:136636. [PMID: 31991272 DOI: 10.1016/j.scitotenv.2020.136636] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2019] [Revised: 01/05/2020] [Accepted: 01/09/2020] [Indexed: 06/10/2023]
Abstract
Mercury contamination in groundwater has been considered as an environmental and public health issue all over the world. Yet, effective in situ remediation techniques have been lacking. A thiol-modified graphene oxide/Fe-Mn composite (SGO/Fe-Mn) was employed as a reactive sorbent of permeable reactive barrier (PRB) for in situ remediation of mercury contaminated groundwater using fixed-bed columns. Mercury existed as HgCl2, Hg(OH)2, and HgClOH, and was mainly removed through surface complexation. The Brunauer-Emmett-Teller sorption isotherm model provided adequate fitting of the sorption isotherm data with a maximum monolayer sorption capacity of 112.03 ± 16.59 mg g-1. Breakthrough time, the time when 5% of initial Hg concentration is measured in the effluent, increased with the decrease of influent mercury concentration, pore velocity, dissolved oxygen (DO), and dissolved organic matter (DOM). The resultant column sorption capacity was enhanced at higher influent mercury concentration, lower groundwater pore velocity, lower DOM and DO. Moreover, when the SGO/Fe-Mn was thoroughly mixed with quartz sand in the column, the breakthrough time was increased and the resultant sorption capacity was improved compared to the case that SGO/Fe-Mn was packed between two layers of quartz sand. Mathematically, the Adams-Bohart model satisfactorily reproduced the initial behavior of mercury breakthrough curves (<40 pore volumes). Yan model adequately simulated the breakthrough curves. The results reveal the potential of SGO/Fe-Mn as an efficient PRB reactive material for in situ remediation of mercury in contaminated groundwater.
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Affiliation(s)
- Yao Huang
- Guangdong Key Laboratory of Environmental Pollution and Health, School of Environment, Jinan University, Guangzhou 511443, China
| | - Mengxia Wang
- Guangdong Key Laboratory of Environmental Pollution and Health, School of Environment, Jinan University, Guangzhou 511443, China
| | - Yanyan Gong
- Guangdong Key Laboratory of Environmental Pollution and Health, School of Environment, Jinan University, Guangzhou 511443, China.
| | - Eddy Y Zeng
- Guangdong Key Laboratory of Environmental Pollution and Health, School of Environment, Jinan University, Guangzhou 511443, China
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5
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Ting Y, Ch'ng BL, Chen C, Ou MY, Cheng YH, Hsu CJ, Hsi HC. A simulation study of mercury immobilization in estuary sediment microcosm by activated carbon/clay-based thin-layer capping under artificial flow and turbation. THE SCIENCE OF THE TOTAL ENVIRONMENT 2020; 708:135068. [PMID: 31780157 DOI: 10.1016/j.scitotenv.2019.135068] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/26/2019] [Revised: 10/10/2019] [Accepted: 10/18/2019] [Indexed: 06/10/2023]
Abstract
In-situ thin layer capping (TLC) is a promising sediment remediation approach that has been shown effective in immobilizing contaminants from releasing to natural biotas and human beings. This research intended to comprehend the effectiveness of Hg immobilization by TLC under turbation condition via a microcosm study. Three TLC caps with different activated carbon (AC)/clay combinations were applied to actual Hg-contaminated estuary sediment (76.0 ± 2.6 mg-Hg/kg). The caps with AC (3%) + bentonite (3%) and AC (3%) + kaolin (3%) were efficient in reducing both total mercury (THg) and methylmercury (MeHg) concentrations in overlying water by 75-95% and 64-98%, respectively, in the later stage of 75-d operation. In contrast, the AC (3%) + montmorillonite (3%) cap did not show a significant reduction on THg and MeHg in the overlying water, probably due to the unstable, suspension property of montmorillonite. The stable caps showed higher resistance to Hg breakthrough under occasional turbation events; however, a labile cap appeared to have dramatic Hg breakthrough when turbation occurred. It is therefore essential to note that with unstable caps, turbation events may result in unwanted secondary resuspension of contaminants.
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Affiliation(s)
- Yu Ting
- Graduate Institute of Environmental Engineering, National Taiwan University, No. 1, Sec. 4, Roosevelt Rd., Taipei 106, Taiwan
| | - Boon-Lek Ch'ng
- Graduate Institute of Environmental Engineering, National Taiwan University, No. 1, Sec. 4, Roosevelt Rd., Taipei 106, Taiwan
| | - Chi Chen
- Graduate Institute of Environmental Engineering, National Taiwan University, No. 1, Sec. 4, Roosevelt Rd., Taipei 106, Taiwan
| | - Meng-Yuan Ou
- Graduate Institute of Environmental Engineering, National Taiwan University, No. 1, Sec. 4, Roosevelt Rd., Taipei 106, Taiwan
| | - Yung-Hua Cheng
- Graduate Institute of Environmental Engineering, National Taiwan University, No. 1, Sec. 4, Roosevelt Rd., Taipei 106, Taiwan
| | - Che-Jung Hsu
- Graduate Institute of Environmental Engineering, National Taiwan University, No. 1, Sec. 4, Roosevelt Rd., Taipei 106, Taiwan
| | - Hsing-Cheng Hsi
- Graduate Institute of Environmental Engineering, National Taiwan University, No. 1, Sec. 4, Roosevelt Rd., Taipei 106, Taiwan.
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6
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Eckley CS, Gilmour CC, Janssen S, Luxton TP, Randall PM, Whalin L, Austin C. The assessment and remediation of mercury contaminated sites: A review of current approaches. THE SCIENCE OF THE TOTAL ENVIRONMENT 2020; 707:136031. [PMID: 31869604 PMCID: PMC6980986 DOI: 10.1016/j.scitotenv.2019.136031] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Revised: 12/07/2019] [Accepted: 12/07/2019] [Indexed: 04/13/2023]
Abstract
Remediation of mercury (Hg) contaminated sites has long relied on traditional approaches, such as removal and containment/capping. Here we review contemporary practices in the assessment and remediation of industrial-scale Hg contaminated sites and discuss recent advances. Significant improvements have been made in site assessment, including the use of XRF to rapidly identify the spatial extent of contamination, Hg stable isotope fractionation to identify sources and transformation processes, and solid-phase characterization (XAFS) to evaluate Hg forms. The understanding of Hg bioavailability for methylation has been improved by methods such as sequential chemical extractions and porewater measurements, including the use of diffuse gradient in thin-film (DGT) samplers. These approaches have shown varying success in identifying bioavailable Hg fractions and further study and field applications are needed. The downstream accumulation of methylmercury (MeHg) in biota is a concern at many contaminated sites. Identifying the variables limiting/controlling MeHg production-such as bioavailable inorganic Hg, organic carbon, and/or terminal electron acceptors (e.g. sulfate, iron) is critical. Mercury can be released from contaminated sites to the air and water, both of which are influenced by meteorological and hydrological conditions. Mercury mobilized from contaminated sites is predominantly bound to particles, highly correlated with total sediment solids (TSS), and elevated during stormflow. Remediation techniques to address Hg contamination can include the removal or containment of Hg contaminated materials, the application of amendments to reduce mobility and bioavailability, landscape/waterbody manipulations to reduce MeHg production, and food web manipulations through stocking or extirpation to reduce MeHg accumulated in desired species. These approaches often rely on knowledge of the Hg forms/speciation at the site, and utilize physical, chemical, thermal and biological methods to achieve remediation goals. Overall, the complexity of Hg cycling allows many different opportunities to reduce/mitigate impacts, which creates flexibility in determining suitable and logistically feasible remedies.
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Affiliation(s)
- Chris S Eckley
- U.S. Environmental Protection Agency, Region-10, 1200 6th Ave, Seattle, WA 98101, USA.
| | - Cynthia C Gilmour
- Smithsonian Environmental Research Center, 647 Contees Wharf Rd., Edgewater, MD 21037-0028, USA.
| | - Sarah Janssen
- USGS Upper Midwest Water Science Center, 8505 Research Way, Middleton, WI 53562, USA.
| | - Todd P Luxton
- US Environmental Protection Agency, Office of Research and Development, National Risk Management Research Laboratory, 26 West Martin Luther King Drive, Cincinnati, OH 45268, USA.
| | - Paul M Randall
- US Environmental Protection Agency, Office of Research and Development, Cincinnati, OH, USA.
| | - Lindsay Whalin
- San Francisco Bay Water Board, 1515 Clay St., Ste. 1400, Oakland, CA 94612, USA.
| | - Carrie Austin
- San Francisco Bay Water Board, 1515 Clay St., Ste. 1400, Oakland, CA 94612, USA.
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7
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Iron Sulfide Minerals as Potential Active Capping Materials for Mercury-Contaminated Sediment Remediation: A Minireview. SUSTAINABILITY 2019. [DOI: 10.3390/su11061747] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Several innovative approaches have been proposed in recent years to remediate contaminated sediment to reduce human health and environmental risk. One of the challenges of sediment remediation stems from its unfeasible high cost, especially when ex situ strategies are selected. Therefore, in situ methods such as active capping have been emerging as possible options for solving sediment problems. Active capping methods have been extensively tested in field-scale sediment remediation for organic pollutants (e.g., PCBs, PAHs, DDT) contamination with good sequestration efficiency; however, these methods have not been widely tested for control of heavy metal pollutants, such as mercury (Hg). In this review, the potentials of using iron sulfide minerals to sequestrate Hg were discussed. Iron sulfide minerals are common in the natural environment and have shown good effectiveness in sequestrating Hg by adsorption or precipitation. Iron sulfides can also be synthesized in a laboratory and modified to enhance their sequestration ability for Hg. Some of the potential advantages of iron sulfides are pointed out here. Additional tests to understand the possibility of applying iron sulfides as active caps to remediate complicated environment systems should be conducted.
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8
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Weber AK, Barber LB, LeBlanc DR, Sunderland EM, Vecitis CD. Geochemical and Hydrologic Factors Controlling Subsurface Transport of Poly- and Perfluoroalkyl Substances, Cape Cod, Massachusetts. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2017; 51:4269-4279. [PMID: 28285525 DOI: 10.1021/acs.est.6b05573] [Citation(s) in RCA: 109] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Growing evidence that certain poly- and perfluoroalkyl substances (PFASs) are associated with negative human health effects prompted the U.S. Environmental Protection Agency to issue lifetime drinking water health advisories for perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) in 2016. Given that groundwater is a major source of drinking water, the main objective of this work was to investigate geochemical and hydrological processes governing the subsurface transport of PFASs at a former fire training area (FTA) on Cape Cod, Massachusetts, where PFAS-containing aqueous film-forming foams were used historically. A total of 148 groundwater samples and 4 sediment cores were collected along a 1200-m-long downgradient transect originating near the FTA and analyzed for PFAS content. The results indicate that unsaturated zones at the FTA and at hydraulically downgradient former domestic wastewater effluent infiltration beds both act as continuous PFAS sources to the groundwater despite 18 and 20 years of inactivity, respectively. Historically different PFAS sources are evident from contrasting PFAS composition near the water table below the FTA and wastewater-infiltration beds. Results from total oxidizable precursor assays conducted using groundwater samples collected throughout the plume suggest that some perfluoroalkyl acid precursors at this site are transporting with perfluoroalkyl acids.
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Affiliation(s)
- Andrea K Weber
- Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University , Cambridge, Massachusetts 02138, United States
| | - Larry B Barber
- U.S. Geological Survey , Boulder, Colorado 80303, United States
| | - Denis R LeBlanc
- U.S. Geological Survey , Northborough, Massachusetts 01532, United States
| | - Elsie M Sunderland
- Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University , Cambridge, Massachusetts 02138, United States
- Department of Environmental Health, Harvard T. H. Chan School of Public Health, Harvard University , Boston, Massachusetts 02115, United States
| | - Chad D Vecitis
- Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University , Cambridge, Massachusetts 02138, United States
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9
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Wang Y, Schaefer JK, Mishra B, Yee N. Intracellular Hg(0) Oxidation in Desulfovibrio desulfuricans ND132. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2016; 50:11049-11056. [PMID: 27654630 DOI: 10.1021/acs.est.6b03299] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The disposal of elemental mercury (Hg(0)) wastes in mining and manufacturing areas has caused serious soil and groundwater contamination issues. Under anoxic conditions, certain anaerobic bacteria can oxidize dissolved elemental mercury and convert the oxidized Hg to neurotoxic methylmercury. In this study, we conducted experiments with the Hg-methylating bacterium Desulfovibrio desulfuricans ND132 to elucidate the role of cellular thiols in anaerobic Hg(0) oxidation. The concentrations of cell-surface and intracellular thiols were measured, and specific fractions of D. desulfuricans ND132 were examined for Hg(0) oxidation activity and analyzed with extended X-ray absorption fine structure (EXAFS) spectroscopy. The experimental data indicate that intracellular thiol concentrations are approximately six times higher than those of the cell wall. Cells reacted with a thiol-blocking reagent were severely impaired in Hg(0) oxidation activity. Spheroplasts lacking cell walls rapidly oxidized Hg(0) to Hg(II), while cell wall fragments exhibited low reactivity toward Hg(0). EXAFS analysis of spheroplast samples revealed that multiple different forms of Hg-thiols are produced by the Hg(0) oxidation reaction and that the local coordination environment of the oxidized Hg changes with reaction time. The results of this study indicate that Hg(0) oxidation in D. desulfuricans ND132 is an intracellular process that occurs by reaction with thiol-containing molecules.
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Affiliation(s)
- Yuwei Wang
- Department of Environmental Sciences, Rutgers University , New Brunswick, New Jersey 08901, United States
| | - Jeffra K Schaefer
- Department of Environmental Sciences, Rutgers University , New Brunswick, New Jersey 08901, United States
| | - Bhoopesh Mishra
- Department of Physics, Illinois Institute of Technology , Chicago, Illinois 60616, United States
| | - Nathan Yee
- Department of Environmental Sciences, Rutgers University , New Brunswick, New Jersey 08901, United States
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10
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Lee SW, Lowry GV, Hsu-Kim H. Biogeochemical transformations of mercury in solid waste landfills and pathways for release. ENVIRONMENTAL SCIENCE. PROCESSES & IMPACTS 2016; 18:176-189. [PMID: 26745831 DOI: 10.1039/c5em00561b] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Mercury (Hg) is present in a variety of solid wastes including industrial wastes, household products, consumer electronics, and medical wastes, some of which can be disposed in conventional landfills. The presence of this neurotoxic metal in landfills is a concern due to the potential for it to leach or volatilize from the landfill and impact local ecosystems. The objective of this review is to describe general practices for the disposal of mercury-bearing solid wastes, summarize previous studies on the release of mercury from landfills, and delineate the expected transformations of Hg within landfill environments that would influence transport of Hg via landfill gas and leachate. A few studies have documented the emissions of Hg as landfill gas, primarily as gaseous elemental Hg(0) and smaller amounts as methylated Hg species. Much less is known regarding the release of Hg in leachate. Landfill conditions are unique from other subsurface environments in that they can contain water with very high conductivity and organic carbon concentration. Landfills also experience large changes in redox potential (and the associated microbial community) that greatly influence Hg speciation, transformations, and mobilization potential. Generally, Hg is not likely to persist in large quantities as dissolved species, since Hg(0) tends to evolve in the gas phase and divalent Hg(ii) sorbs strongly to particulate phases including organic carbon and sulfides. However, Hg(ii) has the potential to associate with or form colloidal particles that can be mobilized in porous media under high organic carbon conditions. Moreover, the anaerobic conditions within landfills can foster the growth of microorganisms that produced monomethyl- and dimethyl-Hg species, the forms of mercury with high potential for bioaccumulation. Much advancement has recently been made in the mercury biogeochemistry research field, and this study seeks to incorporate these findings for landfill settings.
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Affiliation(s)
- Sung-Woo Lee
- Department of Civil & Environmental Engineering, Duke University, Durham, North Carolina 27708, USA.
| | - Gregory V Lowry
- Department of Civil & Environmental Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
| | - Heileen Hsu-Kim
- Department of Civil & Environmental Engineering, Duke University, Durham, North Carolina 27708, USA.
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11
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Hellal J, Guédron S, Huguet L, Schäfer J, Laperche V, Joulian C, Lanceleur L, Burnol A, Ghestem JP, Garrido F, Battaglia-Brunet F. Mercury mobilization and speciation linked to bacterial iron oxide and sulfate reduction: A column study to mimic reactive transfer in an anoxic aquifer. JOURNAL OF CONTAMINANT HYDROLOGY 2015; 180:56-68. [PMID: 26275395 DOI: 10.1016/j.jconhyd.2015.08.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2015] [Revised: 08/02/2015] [Accepted: 08/03/2015] [Indexed: 05/03/2023]
Abstract
Mercury (Hg) mobility and speciation in subsurface aquifers is directly linked to its surrounding geochemical and microbial environment. The role of bacteria on Hg speciation (i.e., methylation, demethylation and reduction) is well documented, however little data is available on their impact on Hg mobility. The aim of this study was to test if (i) Hg mobility is due to either direct iron oxide reduction by iron reducing bacteria (IRB) or indirect iron reduction by sulfide produced by sulfate reducing bacteria (SRB), and (ii) to investigate its subsequent fate and speciation. Experiments were carried out in an original column setup combining geochemical and microbiological approaches that mimic an aquifer including an interface of iron-rich and iron depleted zones. Two identical glass columns containing iron oxides spiked with Hg(II) were submitted to (i) direct iron reduction by IRB and (ii) to indirect iron reduction by sulfides produced by SRB. Results show that in both columns Hg was leached and methylated during the height of bacterial activity. In the column where IRB are dominant, Hg methylation and leaching from the column was directly correlated to bacterial iron reduction (i.e., Fe(II) release). In opposition, when SRB are dominant, produced sulfide induced indirect iron oxide reduction and rapid adsorption of leached Hg (or produced methylmercury) on neoformed iron sulfides (e.g., Mackinawite) or its precipitation as HgS. At the end of the SRB column experiment, when iron-oxide reduction was complete, filtered Hg and Fe concentrations increased at the outlet suggesting a leaching of Hg bound to FeS colloids that may be a dominant mechanism of Hg transport in aquifer environments. These experimental results highlight different biogeochemical mechanisms that can occur in stratified sub-surface aquifers where bacterial activities play a major role on Hg mobility and changes in speciation.
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Affiliation(s)
- Jennifer Hellal
- BRGM (D3E/BGE) 3 Av. Claude Guillemin, 45060, BP. 36009, Orléans Cedex 2, France.
| | - Stéphane Guédron
- University of Geneva, Institut F.-A. Forel, CP416, CH-1290 Versoix, Switzerland
| | - Lucie Huguet
- University of Geneva, Institut F.-A. Forel, CP416, CH-1290 Versoix, Switzerland
| | - Jörg Schäfer
- University of Bordeaux, UMR EPOC, Allée Geoffroy St. Hilaire, 33615 Pessac Cedex, France
| | - Valérie Laperche
- BRGM (D3E/BGE) 3 Av. Claude Guillemin, 45060, BP. 36009, Orléans Cedex 2, France
| | - Catherine Joulian
- BRGM (D3E/BGE) 3 Av. Claude Guillemin, 45060, BP. 36009, Orléans Cedex 2, France
| | - Laurent Lanceleur
- University of Bordeaux, UMR EPOC, Allée Geoffroy St. Hilaire, 33615 Pessac Cedex, France
| | - André Burnol
- BRGM (D3E/BGE) 3 Av. Claude Guillemin, 45060, BP. 36009, Orléans Cedex 2, France
| | | | - Francis Garrido
- BRGM (D3E/BGE) 3 Av. Claude Guillemin, 45060, BP. 36009, Orléans Cedex 2, France
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