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Guo Q, Planer-Friedrich B, Luo L, Liu M, Wu G, Li Y, Zhao Q. Speciation of antimony in representative sulfidic hot springs in the YST Geothermal Province (China) and its immobilization by spring sediments. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2020; 266:115221. [PMID: 32698057 DOI: 10.1016/j.envpol.2020.115221] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Revised: 06/14/2020] [Accepted: 07/08/2020] [Indexed: 06/11/2023]
Abstract
As a well-known toxic element, antimony occurred in a wide range of concentrations in the geothermal waters discharging from Rehai and Daggyai, two representative hydrothermal areas in the Yunnan-Sichuan-Tibet Geothermal Province of China. Antimony speciation in different types of the hot springs in Rehai and Daggyai varied greatly as well, and tri- and tetrathioantimonate were detected in most neutral to alkaline Rehai hot springs. Neutral to alkaline pH, high sulfide concentrations, and high sulfide to antimony ratios were the critical factors promoting the formation of thioantimonates. The fact that no thioantimonates were detected in neutral to alkaline Daggyai hot springs is attributed to high concentrations of coexistent arsenic capable of inhibiting the thiolation of oxyantimony anions, because thioantimonates are kinetically more labile than thioarsenates. Upon discharge of the hot springs, both total aqueous antimony and arsenic decreased rapidly and substantially via immobilization to the sediments in the spring vents and their outflow channels. Some of the common iron-bearing minerals in the spring sediments, like pyrite and goethite, are known sinks for antimony and arsenic. Yet, an interesting difference was observed with antimony and iron contents in the sediment samples showing a significant correlation that was lacking for arsenic and iron contents. The explanation might be that for arsenic, sorption affinities are known to vary significantly with aqueous arsenic speciation and mineral phases. Typically, thiolation increases, and oxidation decreases arsenic mobility. Sorption experiments for antimony conducted in the present study, in contrast, showed that different antimony species were comparably sorbed to pyrite over a wide range of initial antimony concentrations and to goethite at relatively low initial antimony concentrations (but still covering the concentration range of antimony in common natural waters), so neither thiolation nor oxidation contributed significantly to the mobility of antimony in the hot springs investigated in this study.
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Affiliation(s)
- Qinghai Guo
- State Key Laboratory of Biogeology and Environmental Geology & School of Environmental Studies, China University of Geosciences, 430074, Wuhan, Hubei, PR China.
| | - Britta Planer-Friedrich
- Environmental Geochemistry, Bayreuth Center for Ecology and Environmental Research (BayCEER), University of Bayreuth, Universitätsstraße 30, 95447, Bayreuth, Germany
| | - Li Luo
- State Key Laboratory of Biogeology and Environmental Geology & School of Environmental Studies, China University of Geosciences, 430074, Wuhan, Hubei, PR China
| | - Mingliang Liu
- State Key Laboratory of Biogeology and Environmental Geology & School of Environmental Studies, China University of Geosciences, 430074, Wuhan, Hubei, PR China
| | - Geng Wu
- State Key Laboratory of Biogeology and Environmental Geology & School of Environmental Studies, China University of Geosciences, 430074, Wuhan, Hubei, PR China
| | - Yumei Li
- State Key Laboratory of Biogeology and Environmental Geology & School of Environmental Studies, China University of Geosciences, 430074, Wuhan, Hubei, PR China
| | - Qian Zhao
- State Key Laboratory of Biogeology and Environmental Geology & School of Environmental Studies, China University of Geosciences, 430074, Wuhan, Hubei, PR China
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Ren M, Wang D, Ding S, Yang L, Xu S, Yang C, Wang Y, Zhang C. Seasonal mobility of antimony in sediment-water systems in algae- and macrophyte-dominated zones of Lake Taihu (China). CHEMOSPHERE 2019; 223:108-116. [PMID: 30772589 DOI: 10.1016/j.chemosphere.2019.02.013] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Revised: 01/02/2019] [Accepted: 02/04/2019] [Indexed: 06/09/2023]
Abstract
Differences in trophic status can lead to different water quality and sediment geochemistry characteristics, influencing antimony (Sb) mobility in sediments and its release into the water column. In this study, seasonal sampling was conducted in algal- and macrophyte-dominated zones of Lake Taihu, China. High-resolution dialysis (HR-Peeper) and diffusive gradients in thin films (DGT) techniques were used to measure soluble Sb and DGT-labile Sb in the sediment-water profiles at a 4 mm vertical resolution. Results showed that total Sb in sediments from the two zones were on average 3.50 mg/kg and 3.21 mg/kg in the algal- and macrophyte-dominated zones, respectively, with the residual fraction being 96.3% and 95.4% of the total Sb contents in the two zones. In winter, soluble Sb concentrations in both zones increased. This was probably due to the oxidation of Sb(III) to Sb(V) by Mn and Fe oxides. In summer and autumn, soluble Sb concentrations in the algal-dominated region remained low. This is attributed to the dominance of insoluble Sb(III) in sediments under anoxic conditions under eutrophic environments. In contrast, soluble Sb concentrations in the macrophyte-dominated zone were significantly high in summer and were 4.15-times higher than limits set by the World Health Organization (WHO). This likely resulted from the photochemical and rhizospheric oxidation of insoluble Sb(III) compounds. It is suggested that Sb contamination in the sediment-water system of the macrophyte-dominated zone deserves additional attention.
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Affiliation(s)
- Minyi Ren
- State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Dan Wang
- Shanghai Waterway Engineering Design and Consulting Co., Ltd., Shanghai 200120, China
| | - Shiming Ding
- State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China.
| | - Liyuan Yang
- School of Resources and Environment, University of Jinan, Jinan 250022, China
| | - Shiwei Xu
- Central Laboratory, Jiangsu Academy of Agricultural Science, Nanjing 210008, China
| | - Chenye Yang
- Central Laboratory, Jiangsu Academy of Agricultural Science, Nanjing 210008, China
| | - Yan Wang
- State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China; Nanjing EasySensor Environmental Technology Co., Ltd, Nanjing 210018, China
| | - Chaosheng Zhang
- International Network for Environment and Health, School of Geography and Archaeology & Ryan Institute, National University of Ireland, Galway, Ireland
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Tandy S, Hockmann K, Keller M, Studer B, Papritz A, Schulin R. Antimony mobility during prolonged waterlogging and reoxidation of shooting range soil: A field experiment. THE SCIENCE OF THE TOTAL ENVIRONMENT 2018; 624:838-844. [PMID: 29274608 DOI: 10.1016/j.scitotenv.2017.12.193] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2017] [Revised: 12/06/2017] [Accepted: 12/17/2017] [Indexed: 06/07/2023]
Abstract
Due to its increasing anthropogenic use, antimony (Sb) soil pollution is of growing concern. Many soils experience fluctuating hydrological conditions, yet very little is known about how this affects the mobility of this toxic element under field conditions. In this study, we performed an outdoor lysimeter experiment to compare Sb leaching from a calcareous shooting range soil under drained and prolonged waterlogged conditions (1.5-2.75years), followed by a 1.5-year period of soil reoxidation. Waterlogging reduced Sb leachate concentrations significantly compared to drained conditions and soil solution concentrations decreased with depth due to the increased reducing conditions. This was attributed to the reduction of Sb(V) to Sb(III) and the more effective sorption of the latter to metal (hydr)oxides. However, reductive dissolution of iron (hydr)oxides released Sb into solution, although Sb concentrations never exceeded those in the drained lysimeters. On reoxidation of the soil, Sb was remobilized, but even after 1.5years under reoxidised conditions, Sb leachate and soil solution concentrations still remained below those of the drained lysimeters. Our results demonstrate that prolonged waterlogging may have an irreversible effect on Sb leachate and soil solution concentrations.
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Affiliation(s)
- Susan Tandy
- Institute of Terrestrial Ecosystems, ETH Zurich, 8092 Zurich, Switzerland.
| | - Kerstin Hockmann
- Institute of Terrestrial Ecosystems, ETH Zurich, 8092 Zurich, Switzerland; Southern Cross GeoScience, Southern Cross University, Lismore, NSW 2480, Australia
| | - Martin Keller
- Institute of Terrestrial Ecosystems, ETH Zurich, 8092 Zurich, Switzerland
| | - Björn Studer
- Institute of Terrestrial Ecosystems, ETH Zurich, 8092 Zurich, Switzerland
| | - Andreas Papritz
- Institute of Terrestrial Ecosystems, ETH Zurich, 8092 Zurich, Switzerland
| | - Rainer Schulin
- Institute of Terrestrial Ecosystems, ETH Zurich, 8092 Zurich, Switzerland
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Herath I, Vithanage M, Bundschuh J. Antimony as a global dilemma: Geochemistry, mobility, fate and transport. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2017; 223:545-559. [PMID: 28190688 DOI: 10.1016/j.envpol.2017.01.057] [Citation(s) in RCA: 229] [Impact Index Per Article: 32.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2016] [Revised: 12/02/2016] [Accepted: 01/18/2017] [Indexed: 05/14/2023]
Abstract
Elevated concentrations of antimony (Sb) in environmental, biological and geochemical systems originating from natural, geological and anthropogenic sources are of particular global concern. This review presents a critical overview of natural geochemical processes which trigger the mobilization of Sb from its host mineral phases and related rocks to the surrounding environments. The primary source of Sb contamination in the environment is geogenic. The geochemical characteristics of Sb are determined by its oxidation states, speciation and redox transformation. Oxidative dissolution of sulfide minerals and aqueous dissolution are the most prevalent geochemical mechanisms for the release of Sb to the environment. Transformation of mobile forms of Sb is predominantly controlled by naturally occurring precipitation and adsorption processes. Oxyhydroxides of iron, manganese and aluminum minerals have been recognized as naturally occurring Sb sequestrating agents in the environment. Antimony is also immobilized in the natural environment via precipitation with alkali and heavy metals resulting extremely stable mineral phases, such as schafarzikite, tripuhyite and calcium antimonates. Many key aspects, including detection, quantification, and speciation of Sb in different environmental systems as well as its actual human exposure remain poorly understood. Identification of global distribution of most vulnerable Sb-contaminated regions/countries along with aquifer sediments is an urgent necessity for the installation of safe drinking water wells. Such approaches could provide the global population Sb-safe drinking and irrigation water and hinder the propagation of Sb in toxic levels through the food chain. Hence, raising awareness through the mobility, fate and transport of Sb as well as further transdisciplinary research on Sb from global scientific communities will be a crucial stage to establish a sustainable Sb mitigation on a global scale.
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Affiliation(s)
- Indika Herath
- School of Civil Engineering and Surveying, Faculty of Health, Engineering and Sciences, University of Southern Queensland, West Street, Toowoomba, Queensland, Australia
| | - Meththika Vithanage
- Chemical and Environmental Systems Modeling Research Group, National Institute of Fundamental Studies, Hantana Road, Kandy, Sri Lanka; International Centre for Applied Climate Science, University of Southern Queensland, West Street, Toowoomba, Queensland, Australia
| | - Jochen Bundschuh
- School of Civil Engineering and Surveying, Faculty of Health, Engineering and Sciences, University of Southern Queensland, West Street, Toowoomba, Queensland, Australia; International Centre for Applied Climate Science, University of Southern Queensland, West Street, Toowoomba, Queensland, Australia; Deputy Vice-Chancellor's Office (Research and Innovation), University of Southern Queensland, West Street, Toowoomba, Queensland, Australia.
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Kumar N, Couture RM, Millot R, Battaglia-Brunet F, Rose J. Microbial Sulfate Reduction Enhances Arsenic Mobility Downstream of Zerovalent-Iron-Based Permeable Reactive Barrier. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2016; 50:7610-7. [PMID: 27309856 DOI: 10.1021/acs.est.6b00128] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
We assessed the potential of zerovalent-iron- (Fe(0)) based permeable reactive barrier (PRB) systems for arsenic (As) remediation in the presence or absence of microbial sulfate reduction. We conducted long-term (200 day) flow-through column experiments to investigate the mechanisms of As transformation and mobility in aquifer sediment (in particular, the PRB downstream linkage). Changes in As speciation in the aqueous phase were monitored continuously. Speciation in the solid phase was determined at the end of the experiment using X-ray absorption near-edge structure (XANES) spectroscopy analysis. We identified thio-As species in solution and AsS in solid phase, which suggests that the As(V) was reduced to As(III) and precipitated as AsS under sulfate-reducing conditions and remained as As(V) under abiotic conditions, even with low redox potential and high Fe(II) content (4.5 mM). Our results suggest that the microbial sulfate reduction plays a key role in the mobilization of As from Fe-rich aquifer sediment under anoxic conditions. Furthermore, they illustrate that the upstream-downstream linkage of PRB affects the speciation and mobility of As in downstream aquifer sediment, where up to 47% of total As initially present in the sediment was leached out in the form of mobile thio-As species.
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Affiliation(s)
- Naresh Kumar
- BRGM , French Geological Survey, Laboratory Division and ‡Water Environment and Ecotechnology Division, 3 av. Claude Guillemin, 45060 Orléans cedex 02, France
- CEREGE, CNRS-Aix Marseille University - IRD - Collège de France, UM-34 , 13545 Aix-en-Provence, France
| | - Raoul-Marie Couture
- Norwegian Institute for Water Research-NIVA , Gaustadalléen 21, 0349 Oslo, Norway
- Ecohydrology Group, University of Waterloo , 200 University Avenue, Waterloo, Ontario, N2L 3G1 Canada
| | - Romain Millot
- BRGM , French Geological Survey, Laboratory Division and ‡Water Environment and Ecotechnology Division, 3 av. Claude Guillemin, 45060 Orléans cedex 02, France
| | | | - Jérôme Rose
- CEREGE, CNRS-Aix Marseille University - IRD - Collège de France, UM-34 , 13545 Aix-en-Provence, France
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Couture RM, Charlet L, Markelova E, Madé B, Parsons CT. On-off mobilization of contaminants in soils during redox oscillations. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2015; 49:3015-23. [PMID: 25633742 DOI: 10.1021/es5061879] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Near-surface biogeochemical systems can oscillate between oxic and anoxic conditions. Under such periodic changes many redox-sensitive inorganic contaminants undergo speciation, mobility and toxicity changes. We investigated the changes to chromium (Cr), arsenic (As), selenium (Se), antimony (Sb) and uranium (U) mobility during a series of laboratory experiments where argillaceous substrates were subjected to successive cycles of oxidizing and reducing conditions. The EH oscillated between -320 and +470 mV, induced via both abiotic and microbial forcings. Chemically induced cycles of oxidation and reduction were achieved via a combination of gas (N2:CO2 vs compressed air) and carbon (ethanol) addition, to stimulate the metabolism of a natively present microbial community. The contaminants were added either alone or as contaminant mixtures. Results show clear on-off switch mobility behavior for both major elements such as carbon (C), iron (Fe) and manganese (Mn) and for contaminants. Mn, Fe, and As were mobilized under anoxic conditions, whereas Sb, Se, and U were mobilized under oxic conditions. While As, Sb, and U were reversibly sorbed, Se and Cr were irreversibly sequestered via reductive precipitation. When present in aqueous solutions at high concentrations, Cr(VI) prevented the reduction of Mn and Fe, and inhibited the mobilization of elements with lower EH(o). To improve remediation strategies for multiple contaminants in redox-dynamic environments, we propose a mixed kinetic-equilibrium biogeochemical model that can be forced by oscillating boundary conditions and that uses literature rates and constants to capture the key processes responsible for the mobilization of contaminants in soils.
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Affiliation(s)
- Raoul-Marie Couture
- Norwegian Institute for Water Research , Gaustadalléen 21, 0349 Oslo, Norway
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Anderer C, Delwa de Alarcón N, Näther C, Bensch W. A Strategy for the Preparation of Thioantimonates Based on the Concept of Weak Acids and Corresponding Strong Bases. Chemistry 2014; 20:16953-9. [DOI: 10.1002/chem.201404396] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2014] [Indexed: 11/09/2022]
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Helz GR. Activity of zero-valent sulfur in sulfidic natural waters. GEOCHEMICAL TRANSACTIONS 2014; 15:13. [PMID: 26561456 PMCID: PMC4631721 DOI: 10.1186/s12932-014-0013-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/03/2014] [Accepted: 07/29/2014] [Indexed: 06/05/2023]
Abstract
BACKGROUND Ionic and molecular carriers of dissolved (filter-passing) zero-valent sulfur (S0) in anaerobic natural waters include polysulfides, Sn2-, molecular S8(aq), organic macromolecules and certain higher valent thioanions. Because S0 is rapidly transferred among these various carriers, its biogeochemical roles in such processes as dehalogenation of organic compounds, chelation of trace metals, and anaerobic microbial metabolism are not determined solely by one ionic or molecular species. Here, S0 is treated collectively as a virtual thermodynamic component, and computational as well as graphical methods for quantifying its activity (aS0) in natural waters are presented. From aS0, concentrations of the ionic and molecular carriers of S0 can be calculated easily. RESULTS Concentration ratios of any two polysulfide ions define aS0 (Method I). Unfortunately these concentrations are often too low in nature for accurate quantification with current methods. Measurements of total divalent sulfur (ΣS-II), zero-valent sulfur (ΣS0) and pH provide a more widely applicable approach (Method II). Systematic errors in ΣS0 measurements are the main limit to accuracy of this method at the present time. Alternative methods based on greigite solubility and potentiometry are discussed. A critical comparison of Methods I and II reveals inconsistencies at low ΣS0/ΣS-II that imply errors in the thermodynamic data for HS2- and S2-. For samples having low ΣS0/ΣS-II, an interim remedy is recommended: letting pKa2 = 6.3 for all HSn- ions. CONCLUSIONS Newly assembled data for aS0 in a selection of anaerobic natural waters indicate that S0 is always metastable in the surveyed samples with respect to disproportionation to sulfide and sulfate. In all the surveyed environments, sulfur-rich minerals, such as greigite, covellite and orpiment, are stable in preference to their sulfur-poor cohorts, mackinawite, chalcocite and realgar. The aS0 values in the dataset span conditions favoring Hg-polysulfide complexes vs. Hg-sulfide complexes, implying that aS0 could affect Hg-methylation rates in nature. No support is found for the common assumption that aS0 = 1 in reducing natural waters. This paper calls attention to an urgent need for improved measurement methods, especially for total zero-valent sulfur, as well as new determinations of ionization constants for all HSn- species.
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Affiliation(s)
- George R Helz
- Chemistry and Biochemistry, University of Maryland, College Park, 20742 MD USA
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Waldmann M, Musgraves JD, Richardson K, Arnold CB. Structural properties of solution processed Ge23Sb7S70 glass materials. ACTA ACUST UNITED AC 2012. [DOI: 10.1039/c2jm32235h] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Planer-Friedrich B, Scheinost AC. Formation and structural characterization of thioantimony species and their natural occurrence in geothermal waters. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2011; 45:6855-6863. [PMID: 21749047 DOI: 10.1021/es201003k] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Previously postulated from laboratory studies, the occurrence of antimony-sulfur species in geothermal waters could now be proven using anion-exchange chromatography-inductively coupled plasma-mass spectrometry. The two thioantimony species detected by AEC-ICP-MS in oxic synthetic antimonite-sulfide solutions were assigned to tri- and tetrathioantimonate based on their S/Sb ratios and structural characterization by X-ray absorption spectroscopy (XAS). XAS confirmed that the initial species formed under anoxic conditions from antimonite at a 10-fold sulfide excess is trithioantimonite. Trithioantimonite rapidly transforms to tetrathioantimonate in the presence of oxygen or to antimonite at excess OH(-) versus SH(-) concentrations, and escapes chromatographic detection. In natural geothermal waters, up to 30% trithioantimonate and 9% tetrathioantimonate were detected. Their occurrence increased at increasingly alkaline pH and with increasing sulfide and decreasing oxygen concentrations. Considering the large sulfide excess (100 to 10,000-fold) the proportion of thioantimonates formed under natural conditions is lower than expected from synthetic solutions. Together with the observed high thioarsenate concentrations (>80% of total arsenic), this indicates that in direct competition with arsenic for a limited source of sulfide, thioantimonates form less spontaneously than thioarsenates. Interactions of arsenic and antimony with sulfur can therefore be decisive for similarities or differences in their environmental behavior.
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Affiliation(s)
- Britta Planer-Friedrich
- Environmental Geochemistry, University of Bayreuth, Universitaetsstrasse 30, 95440 Bayreuth, Germany.
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Couture RM, Van Cappellen P. Reassessing the role of sulfur geochemistry on arsenic speciation in reducing environments. JOURNAL OF HAZARDOUS MATERIALS 2011; 189:647-52. [PMID: 21382662 DOI: 10.1016/j.jhazmat.2011.02.029] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2010] [Revised: 02/03/2011] [Accepted: 02/10/2011] [Indexed: 05/16/2023]
Abstract
Recent evidence suggests that the oxidation of arsenite by zero-valent sulfur (S(0)) may produce stable aqueous arsenate species under highly reducing conditions. The speciation of arsenic (As) in reducing soils, sediments and aquifers may therefore be far more complex than previously thought. We illustrate this by presenting updated E(h)-pH diagrams of As speciation in sulfidic waters that include the most recently reported formation constants for sulfide complexes of As(III) and As(V). The results show that the stability fields of As(III) and As(V) (oxy)thioanions cover a large pH range, from pH 5 to 10. In particular, As(V)-S(-II) complexes significantly enhance the predicted solubility of As under reducing conditions. Equilibrium calculations further show that, under conditions representative of sulfidic pore waters and in the presence of solid-phase elemental sulfur, the S(0)((aq))/HS(-) couple yields a redox potential (E(h))∼ 0.1 V higher than the SO(4)(2-)/HS(-) couple. S(0) may thus help stabilize aqueous As(V) not only by providing an electron acceptor for As(III) but also by contributing to a more oxidizing redox state.
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Affiliation(s)
- Raoul-Marie Couture
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA 30332-0340, USA.
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Tossell JA. Calculation of the visible-UV absorption spectra of hydrogen sulfide, bisulfide, polysulfides, and As and Sb sulfides, in aqueous solution. GEOCHEMICAL TRANSACTIONS 2003; 4:28. [PMID: 35412783 PMCID: PMC1475635 DOI: 10.1186/1467-4866-4-28] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2003] [Accepted: 10/28/2003] [Indexed: 05/16/2023]
Abstract
Recently we showed that visible-UV spectra in aqueous solution can be accurately calculated for arsenic (III) bisulfides, such as As(SH)3, As(SH)2S- and their oligomers. The calculated lowest energy transitions for these species were diagnostic of their protonation and oligomerization state. We here extend these studies to As and Sb oxidation state III and v sulfides and to polysulfides S n 2- , n = 2-6, the bisulfide anion, SH-, hydrogen sulfide, H2S and the sulfanes, S n H2, n = 2-5. Many of these calculations are more difficult than those performed for the As(iii) bisulfides, since the As and Sb(v) species are more acidic and therefore exist as highly charged anions in neutral and basic solutions. In general, small and/or highly charged anions are more difficult to describe computationally than larger, monovalent anions or neutral molecules. We have used both Hartree-Fock based (CI Singles and Time-Dependent HF) and density functional based (TD B3LYP) techniques for the calculations of absorption energy and intensity and have used both explicit water molecules and a polarizable continuum to describe the effects of hydration. We correctly reproduce the general trends observed experimentally, with absorption energies increasing from polysulfides to As, Sb sulfides to SH- to H2S. As and Sb(v) species, both monomers and dimers, also absorb at characteristically higher energies than do the analogous As and Sb(III)species. There is also a small reduction in absorption energy from monomeric to dimeric species, for both As and Sb III and v. The polysufides, on the other hand, show no simple systematic changes in UV spectra with chain length, n, or with protonation state. Our results indicate that for the As and Sb sulfides, the oxidation state, degree of protonation and degree of oligomerization can all be determined from the visible-UV absorption spectrum. We have also calculated the aqueous phase energetics for the reaction of S8 with SH- to produce the polysulfides, S n H-, n = 2-6. Our results are in excellent agreement with available experimental data, and support the existence of a S6 species.
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Affiliation(s)
- JA Tossell
- Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742
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