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Chen W, Garcia AN, Phillips E, De Vera J, Passeport E, O'Carroll DM, Sleep B, Lollar BS. Quantifying remediation of chlorinated volatile compounds by sulfidated nano zerovalent iron treatment using numerical modeling and CSIA. WATER RESEARCH 2024; 263:122149. [PMID: 39098153 DOI: 10.1016/j.watres.2024.122149] [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: 03/08/2024] [Revised: 07/23/2024] [Accepted: 07/24/2024] [Indexed: 08/06/2024]
Abstract
Sulfidated nanoscale zerovalent iron (S-nZVI) has demonstrated promising reactivity and longevity for remediating chlorinated volatile compounds (cVOC) contaminants in laboratory tests. However, its effectiveness in field applications remains inadequately evaluated. This study provides the first quantitative evaluation of the long-term effectiveness of carboxymethyl cellulose-stabilized S-nZVI (CMC-S-nZVI) at a cVOC-contaminated field site. A reactive transport model-based numerical approach delineates the change in cVOC concentrations and carbon isotope values (i.e., δ13C from compound-specific stable isotope analysis (CSIA)) caused by dissolution of dense non-aqueous phase liquid, sorption, and pathway-specific degradation and production, respectively. This delineation reveals quantitative insights into remediation effectiveness typically difficult to obtain, including extent of degradation, contributions of different degradation pathways, and degradation rate coefficients. Significantly, even a year after CMC-S-nZVI application, degradation remains an important process effectively removing various cVOC contaminants (i.e., chlorinated ethenes, 1,2-dichloroethanes, and chlorinated methanes) at an extent varying from 5 %-62 %. Although the impacts of CMC-S-nZVI abundance on degradation vary for different cVOC and for different sampling locations at the site, for the primary site contaminants of tetrachloroethene and trichloroethene, their predominance of dichloroelimination pathway (≥ 88 %), high degradation rate coefficient (0.4-1.7 d-1), and occurrence at locations with relatively high CMC-S-nZVI abundance strongly indicate the effectiveness of abiotic remediation. These quantitative assessments support that CMC-S-nZVI supports sustainable ZVI-based remediation. Further, the novel numerical approach presented in this study provides a powerful tool for quantitative cVOC remediation assessments at complex field sites where multiple processes co-occur to control both concentration and CSIA data.
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Affiliation(s)
- Weibin Chen
- Department of Earth Sciences, University of Toronto, 22 Ursula Franklin Street, Toronto, Ontario, M5S 3B1, Canada
| | - Ariel Nunez Garcia
- Department of Civil Engineering, Queen's University, 58 University Ave, Kingston, Ontario, K7L 3N9, Canada
| | - Elizabeth Phillips
- Department of Earth Sciences, University of Toronto, 22 Ursula Franklin Street, Toronto, Ontario, M5S 3B1, Canada
| | - Joan De Vera
- Department of Earth Sciences, University of Toronto, 22 Ursula Franklin Street, Toronto, Ontario, M5S 3B1, Canada
| | - Elodie Passeport
- Department of Civil and Mineral Engineering, University of Toronto, 35 St George Street, Toronto, Ontario, M5S 1A4, Canada; Department of Chemical Engineering and Applied Chemistry, University of Toronto, 200 College Street, Toronto, Ontario, M5S 3E5, Canada
| | - Denis M O'Carroll
- School of Civil and Environmental Engineering, Water Research Centre, University of New South Wales, Sydney, NSW 2052, Australia
| | - Brent Sleep
- Department of Civil and Mineral Engineering, University of Toronto, 35 St George Street, Toronto, Ontario, M5S 1A4, Canada
| | - Barbara Sherwood Lollar
- Department of Earth Sciences, University of Toronto, 22 Ursula Franklin Street, Toronto, Ontario, M5S 3B1, Canada; Institut de Physique du Globe de Paris (IPGP), Université Paris Cité, 1 Rue Jussieu, Paris 75005, France.
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2
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Gil-Villalba S, Palau J, Soder-Walz JM, Vallecillo MA, Corregidor J, Tirado A, Shouakar-Stash O, Guivernau M, Viñas M, Soler A, Rosell M. Use of isotopic (C, Cl) and molecular biology tools to assess biodegradation in a source area of chlorinated ethenes after biostimulation with Emulsified Vegetable Oil (EVO). THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 951:175351. [PMID: 39151619 DOI: 10.1016/j.scitotenv.2024.175351] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2024] [Revised: 08/04/2024] [Accepted: 08/05/2024] [Indexed: 08/19/2024]
Abstract
Enhanced In Situ Bioremediation (EISB) using Emulsified Vegetable Oil (EVO) as a long-term electron donor has gained prominence for the treatment of groundwater contaminated with chlorinated ethenes (CEs). This study explores the potential of isotopic and molecular biology tools (MBT) to investigate the CEs (PCE, TCE and cis-DCE) bioremediation using EVO in a contaminated site. A multiple approach using C and Cl-CSIA, quantification of Dehalococcoides (Dhc) and specific reductive dechlorination (RD) gene population, and hydrochemical data in microcosm experiments and field samples was applied. Despite the high partitioning of CEs into the EVO phase, the carbon isotopic values of the remaining CEs fraction in the aqueous phase did not exhibit significant changes caused by phase partitioning in laboratory experiments. Both microcosm experiments and field data revealed a rapid RD of PCE and TCE, resulting in the transient accumulation of cis-DCE, which was slowly degraded to vinyl chloride (VC). These results agreed with the presence of Dhc populations and a shift to stronger reducing conditions in the field: i) RD functional genes (tceA, vcrA and bvcA) exhibited a trend to higher values and ii) a substantial increase in Dhc populations (up to 30% of the total bacterial populations) was observed over time. The dual-element isotope slope ΛC-Cl for RD of cis-DCE obtained from field data (ΛC - Cl = 5 ± 3) was similar to the one determined from the microcosm experiments under controlled anoxic conditions (ΛC - Cl = 4.9 ± 0.8). However, ΛC-Cl values differ from those reported so far for laboratory studies with Dhc strains and mixed cultures containing Dhc, i.e., between 8.3 and 17.8. This observation underscores the potential variety of reductive dehalogenases involved during cis-DCE RD and the importance of determining site-specific Λ and ɛ values in order to improve the identification and quantification of transformation processes in the field.
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Affiliation(s)
- Sergio Gil-Villalba
- Grup MAiMA, SGR Mineralogia Aplicada, Geoquímica i Hidrogeologia (MAGH), Departament de Mineralogia, Petrologia i Geologia Aplicada, Facultat de Ciències de la Terra, Institut de Recerca de l'Aigua (IdRA), Universitat de Barcelona (UB), Martí Franquès s/n, 08028 Barcelona, Spain.
| | - Jordi Palau
- Grup MAiMA, SGR Mineralogia Aplicada, Geoquímica i Hidrogeologia (MAGH), Departament de Mineralogia, Petrologia i Geologia Aplicada, Facultat de Ciències de la Terra, Institut de Recerca de l'Aigua (IdRA), Universitat de Barcelona (UB), Martí Franquès s/n, 08028 Barcelona, Spain
| | - Jesica M Soder-Walz
- Departament d'Enginyeria Química, Biològica i Ambiental, Universitat Autònoma de Barcelona (UAB), Carrer de les Sitges s/n, Bellaterra, Spain
| | - Miguel A Vallecillo
- Environmental Resources Management Iberia SAU, Rambla de Catalunya 33, 08007 Barcelona, Spain
| | - Jordi Corregidor
- Environmental Resources Management Iberia SAU, Rambla de Catalunya 33, 08007 Barcelona, Spain
| | - Andrea Tirado
- Environmental Resources Management Iberia SAU, Rambla de Catalunya 33, 08007 Barcelona, Spain
| | | | - Miriam Guivernau
- Sustainability in Biosystems Programme, Institute of Agrifood Research and Technology (IRTA), Torre Marimon, Caldes de Montbui, Barcelona, Spain
| | - Marc Viñas
- Sustainability in Biosystems Programme, Institute of Agrifood Research and Technology (IRTA), Torre Marimon, Caldes de Montbui, Barcelona, Spain
| | - Albert Soler
- Grup MAiMA, SGR Mineralogia Aplicada, Geoquímica i Hidrogeologia (MAGH), Departament de Mineralogia, Petrologia i Geologia Aplicada, Facultat de Ciències de la Terra, Institut de Recerca de l'Aigua (IdRA), Universitat de Barcelona (UB), Martí Franquès s/n, 08028 Barcelona, Spain
| | - Monica Rosell
- Grup MAiMA, SGR Mineralogia Aplicada, Geoquímica i Hidrogeologia (MAGH), Departament de Mineralogia, Petrologia i Geologia Aplicada, Facultat de Ciències de la Terra, Institut de Recerca de l'Aigua (IdRA), Universitat de Barcelona (UB), Martí Franquès s/n, 08028 Barcelona, Spain
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3
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Zhang X, Yi L, Li R. Identification of dense nonaqueous phase liquid sources in groundwater: a review of isotope technique. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2024; 31:52688-52706. [PMID: 39190252 DOI: 10.1007/s11356-024-34427-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/28/2024] [Accepted: 07/15/2024] [Indexed: 08/28/2024]
Abstract
Excessive dense nonaqueous phase liquids (DNAPLs) in subsurface aquifers posed a threat to human health and sustainable development of groundwater resources. Accurately identifying the sources of DNAPLs is crucial for groundwater remediation and prevention efforts. In the previous studies, significant advances were made in using isotope techniques for identifying DNAPLs in groundwater. In this paper, we provide a comprehensive overview of the commonly used isotopic tools applied to source identification. This overview will outline the advantages and limitations of the isotope technique and describe the needs for future research. Isotope tracing techniques are based on the unique isotopic characteristics of DNAPLs from different sources, enabling the identification and differentiation of DNAPL sources. The δ13C and δ37Cl values are most commonly used for identifying DNAPLs in groundwater. In field applications, however, the differences in isotopic characteristics from diverse sources can be weakened after undergoing a series of human and natural factors, which can affect the accuracy of source identification. To improve the accuracy of DNAPL source identification, a dual-isotope tracing approach seems the best available solution. Nonetheless, in the face of complex polluted environments, the dual-isotope method seems stretched. Therefore, further researches remain to be carried out to accurately and efficiently assess the sources of DNAPLs in groundwater and their individual contributions. This is a prerequisite for groundwater resource conservation and remediation efforts.
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Affiliation(s)
- Xiang Zhang
- College of Environmental Science and Engineering, Nankai University, Tianjin, 300350, PR China
| | - Lixin Yi
- College of Environmental Science and Engineering, Nankai University, Tianjin, 300350, PR China.
| | - Ruotong Li
- College of Environmental Science and Engineering, Nankai University, Tianjin, 300350, PR China
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4
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Khan AM, Gharasoo M, Wick LY, Thullner M. Phase-specific stable isotope fractionation effects during combined gas-liquid phase exchange and biodegradation. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2022; 309:119737. [PMID: 35817302 DOI: 10.1016/j.envpol.2022.119737] [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: 02/24/2022] [Revised: 06/28/2022] [Accepted: 07/04/2022] [Indexed: 06/15/2023]
Abstract
Stable isotope fractionation of toluene under dynamic phase exchange was studied aiming at ascertaining the effects of gas-liquid partitioning and biodegradation of toluene stable isotope composition in liquid-air phase exchange reactors (Laper). The liquid phase consisted of a mixture of aqueous minimal media, a known amount of a mixture of deuterated (toluene-d) and non-deuterated toluene (toluene-h), and bacteria of toluene degrading strain Pseudomonas putida KT2442. During biodegradation experiments, the liquid and air-phase concentrations of both toluene isotopologues were monitored to determine the observable stable isotope fractionation in each phase. The results show a strong fractionation in both phases with apparent enrichment factors beyond -800‰. An offset was observed between enrichment factors in the liquid and the gas phase with gas-phase values showing a stronger fractionation in the gas than in the liquid phase. Numerical simulation and parameter fitting routine was used to challenge hypotheses to explain the unexpected experimental data. The numerical results showed that either a very strong, yet unlikely, fractionation of the phase exchange process or a - so far unreported - direct consumption of gas phase compounds by aqueous phase microorganisms could explain the observed fractionation effects. The observed effect can be of relevance for the analysis of volatile contaminant biodegradation using stable isotope analysis in unsaturated subsurface compartments or other environmental compartment containing a gas and a liquid phase.
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Affiliation(s)
- Ali M Khan
- Department of Environmental Microbiology, UFZ - Helmholtz Centre for Environmental Research, Leipzig, Germany
| | - Mehdi Gharasoo
- Department of Earth and Environmental Sciences, University of Waterloo, Waterloo, Ontario, Canada
| | - Lukas Y Wick
- Department of Environmental Microbiology, UFZ - Helmholtz Centre for Environmental Research, Leipzig, Germany
| | - Martin Thullner
- Department of Environmental Microbiology, UFZ - Helmholtz Centre for Environmental Research, Leipzig, Germany.
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5
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Kundu K, Melsbach A, Heckel B, Schneidemann S, Kanapathi D, Marozava S, Merl-Pham J, Elsner M. Linking Increased Isotope Fractionation at Low Concentrations to Enzyme Activity Regulation: 4-Cl Phenol Degradation by Arthrobacter chlorophenolicus A6. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2022; 56:3021-3032. [PMID: 35148097 PMCID: PMC8892832 DOI: 10.1021/acs.est.1c04939] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/23/2021] [Revised: 01/23/2022] [Accepted: 01/26/2022] [Indexed: 06/14/2023]
Abstract
Slow microbial degradation of organic trace chemicals ("micropollutants") has been attributed to either downregulation of enzymatic turnover or rate-limiting substrate supply at low concentrations. In previous biodegradation studies, a drastic decrease in isotope fractionation of atrazine revealed a transition from rate-limiting enzyme turnover to membrane permeation as a bottleneck when concentrations fell below the Monod constant of microbial growth. With degradation of the pollutant 4-chlorophenol (4-CP) by Arthrobacter chlorophenolicus A6, this study targeted a bacterium which adapts its enzyme activity to concentrations. Unlike with atrazine degradation, isotope fractionation of 4-CP increased at lower concentrations, from ε(C) = -1.0 ± 0.5‰ in chemostats (D = 0.090 h-1, 88 mg L-1) and ε(C) = -2.1 ± 0.5‰ in batch (c0 = 220 mg L-1) to ε(C) = -4.1 ± 0.2‰ in chemostats at 90 μg L-1. Surprisingly, fatty acid composition indicated increased cell wall permeability at high concentrations, while proteomics revealed that catabolic enzymes (CphCI and CphCII) were differentially expressed at D = 0.090 h-1. These observations support regulation on the enzyme activity level─through either a metabolic shift between catabolic pathways or decreased enzymatic turnover at low concentrations─and, hence, reveal an alternative end-member scenario for bacterial adaptation at low concentrations. Including more degrader strains into this multidisciplinary analytical approach offers the perspective to build a knowledge base on bottlenecks of bioremediation at low concentrations that considers bacterial adaptation.
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Affiliation(s)
- Kankana Kundu
- Institute
of Groundwater Ecology, Helmholtz Zentrum
Munchen, Ingolstadter
Landstraße 1, 85764 Neuherberg, Bavaria, Germany
- Center
for Microbial Ecology and Technology (CMET), Faculty of Bioscience
Engineering, University of Ghent, Coupure Links 653, 9000 Ghent, Belgium
| | - Aileen Melsbach
- Institute
of Groundwater Ecology, Helmholtz Zentrum
Munchen, Ingolstadter
Landstraße 1, 85764 Neuherberg, Bavaria, Germany
- Chair
of Analytical Chemistry and Water Chemistry, Technical University of Munich, Lichtenbergstr. 4, D-85748 Garching, Germany
| | - Benjamin Heckel
- Institute
of Groundwater Ecology, Helmholtz Zentrum
Munchen, Ingolstadter
Landstraße 1, 85764 Neuherberg, Bavaria, Germany
| | - Sarah Schneidemann
- Institute
of Groundwater Ecology, Helmholtz Zentrum
Munchen, Ingolstadter
Landstraße 1, 85764 Neuherberg, Bavaria, Germany
| | - Dheeraj Kanapathi
- Institute
of Groundwater Ecology, Helmholtz Zentrum
Munchen, Ingolstadter
Landstraße 1, 85764 Neuherberg, Bavaria, Germany
| | - Sviatlana Marozava
- Institute
of Groundwater Ecology, Helmholtz Zentrum
Munchen, Ingolstadter
Landstraße 1, 85764 Neuherberg, Bavaria, Germany
| | - Juliane Merl-Pham
- Core
Facility Proteomics, Helmholtz Zentrum München, Heidemannstr. 1, 80939 Munich, Germany
| | - Martin Elsner
- Institute
of Groundwater Ecology, Helmholtz Zentrum
Munchen, Ingolstadter
Landstraße 1, 85764 Neuherberg, Bavaria, Germany
- Chair
of Analytical Chemistry and Water Chemistry, Technical University of Munich, Lichtenbergstr. 4, D-85748 Garching, Germany
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6
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Ottosen CB, Bjerg PL, Hunkeler D, Zimmermann J, Tuxen N, Harrekilde D, Bennedsen L, Leonard G, Brabæk L, Kristensen IL, Broholm MM. Assessment of chlorinated ethenes degradation after field scale injection of activated carbon and bioamendments: Application of isotopic and microbial analyses. JOURNAL OF CONTAMINANT HYDROLOGY 2021; 240:103794. [PMID: 33735692 DOI: 10.1016/j.jconhyd.2021.103794] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2020] [Revised: 01/19/2021] [Accepted: 03/01/2021] [Indexed: 06/12/2023]
Abstract
Over the last decade, activated carbon amendments have successfully been applied to retain chlorinated ethene subsurface contamination. The concept of this remediation technology is that activated carbon and bioamendments are injected into aquifer systems to enhance biodegradation. While the scientific basis of the technology is established, there is a need for methods to characterise and quantify the biodegradation at field scale. In this study, an integrated approach was applied to assess in situ biodegradation after the establishment of a cross sectional treatment zone in a TCE plume. The amendments were liquid activated carbon, hydrogen release donors and a Dehalococcoides containing culture. The integrated approach included spatial and temporal evaluations on flow and transport, redox conditions, contaminant concentrations, biomarker abundance and compound-specific stable isotopes. This is the first study applying isotopic and microbial techniques to assess field scale biodegradation enhanced by liquid activated carbon and bioamendments. The injection enhanced biodegradation from TCE to primarily cis-DCE. The Dehalococcoides abundances facilitated characterisation of critical zones with insufficient degradation and possible explanations. A conceptual model of isotopic data together with distribution and transport information improved process understanding; the degradation of TCE was insufficient to counteract the contaminant input by inflow into the treatment zone and desorption from the sediment. The integrated approach could be used to document and characterise the in situ degradation, and the isotopic and microbial data provided process understanding that could not have been gathered from conventional monitoring tools. However, quantification of degradation through isotope data was restricted for TCE due to isotope masking effects. The combination of various monitoring tools, applied frequently at high-resolution, with system understanding, was essential for the assessment of biodegradation in the complex, non-stationary system. Furthermore, the investigations revealed prospects for future research, which should focus on monitoring contaminant fate and microbial distribution on the sediment and the activated carbon.
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Affiliation(s)
- Cecilie B Ottosen
- Department of Environmental Engineering, Technical University of Denmark (DTU), Bygningstorvet, Building 115, 2800 Kgs. Lyngby, Denmark.
| | - Poul L Bjerg
- Department of Environmental Engineering, Technical University of Denmark (DTU), Bygningstorvet, Building 115, 2800 Kgs. Lyngby, Denmark
| | - Daniel Hunkeler
- Centre for Hydrogeology and Geothermics (CHYN), University of Neuchâtel, Rue Emile Argand 11, CH-2000 Neuchâtel, Switzerland
| | - Jeremy Zimmermann
- Centre for Hydrogeology and Geothermics (CHYN), University of Neuchâtel, Rue Emile Argand 11, CH-2000 Neuchâtel, Switzerland
| | - Nina Tuxen
- The Capital Region of Denmark, Center for Regional Development, Regionsgården, Kongens Vænge 2, 3400 Hillerød, Denmark
| | | | | | - Gareth Leonard
- REGENESIS Bioremediation Products Ltd, F8 Nutgrove Office Park, Rathfarnham, Dublin 14, Ireland
| | - Lærke Brabæk
- Department of Environmental Engineering, Technical University of Denmark (DTU), Bygningstorvet, Building 115, 2800 Kgs. Lyngby, Denmark
| | - Inge Lise Kristensen
- Department of Environmental Engineering, Technical University of Denmark (DTU), Bygningstorvet, Building 115, 2800 Kgs. Lyngby, Denmark
| | - Mette M Broholm
- Department of Environmental Engineering, Technical University of Denmark (DTU), Bygningstorvet, Building 115, 2800 Kgs. Lyngby, Denmark
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7
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Walaszek M, Cary L, Billon G, Blessing M, Bouvet-Swialkowski A, George M, Criquet J, Mossmann JR. Dynamics of chlorinated aliphatic hydrocarbons in the Chalk aquifer of northern France. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 757:143742. [PMID: 33221002 DOI: 10.1016/j.scitotenv.2020.143742] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Revised: 11/11/2020] [Accepted: 11/11/2020] [Indexed: 06/11/2023]
Abstract
The Chalk aquifer used for drinking-water production in the southwest of the Lille European Metropolis is threatened by the presence of chlorinated aliphatic hydrocarbons (CHCs), their concentrations in groundwater regularly exceeding the regulatory limits for drinking water in France. This hinders its use for drinking-water production. Understanding the dynamics and spatial distribution of CHC in the aquifer is a key factor for resource sustainability. For that purpose, an intensive monitoring was undertaken in several well fields and at different depths over eight years. To assess a possible migration and/or degradation of the compounds, the water column in several wells was sampled at various depths with passive samplers. Furthermore, CHC degradation mechanisms were investigated with compound-specific carbon-isotope analysis. The CHC concentrations and their distributions in the area depend on past and current industrial activity, causing plumes emphasized by pumping in the wells, such plumes being multi-source with no identified origin in most wells. In the south area of Les Ansereuilles, reductive dechlorination of tetrachloroethylene from a former industrial laundry highly impacted the surrounding area with its main degradation product cis-1,2-dichloroethylene. The same area is also affected by tetrachlroroethylene from several industrial laundries, textile factories and dyeing industries with also an anaerobic degradation. In the northern part of Les Ansereuilles, tetrachloroethylene, trichloroethane, trichloroethylene and 1,1-dichloroethylene were found as primary products, whereas cis-1,2-dichloroethylene appears to be an anaerobic degradation product of TCE. The other well fields (Houplin-Ancoisne, Seclin and Emmerin) are less impacted by CHC pollution, and it was shown that no CHC degradation occurred in the wells. However, the stratification of CHCs in the well-water columns, their constant concentration values over time caused by the large amount of available CHCs, and the minor degradation occurring in wells are of concern for water operators in the future.
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Affiliation(s)
- Milena Walaszek
- Univ. Lille CNRS, UMR 8516 - LASIRE, Equipe Physico-Chimie de l'Environnement, Lille F-59000, France; BRGM (French Geological Survey), 59810 Lesquin, France
| | - Lise Cary
- BRGM (French Geological Survey), 59810 Lesquin, France.
| | - Gabriel Billon
- Univ. Lille CNRS, UMR 8516 - LASIRE, Equipe Physico-Chimie de l'Environnement, Lille F-59000, France
| | | | | | - Melinda George
- Univ. Lille CNRS, UMR 8516 - LASIRE, Equipe Physico-Chimie de l'Environnement, Lille F-59000, France
| | - Justine Criquet
- Univ. Lille CNRS, UMR 8516 - LASIRE, Equipe Physico-Chimie de l'Environnement, Lille F-59000, France
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8
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Zito P, Smith DF, Cao X, Ghannam R, Tarr MA. Barium ion adduct mass spectrometry to identify carboxylic acid photoproducts from crude oil-water systems under solar irradiation. ENVIRONMENTAL SCIENCE. PROCESSES & IMPACTS 2020; 22:2313-2321. [PMID: 33150906 DOI: 10.1039/d0em00390e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Petroleum derived dissolved organic matter (DOMHC) samples were successfully cationized with barium, revealing many [M-H + Ba]+ peaks in both dark and simulated sunlight treatments. The DOMHC samples generated after light exposure exhibited a greater number of [M-H + Ba]+ peaks compared to the dark control. Multiple [M-H + Ba]+ peaks were investigated in the irradiated DOMHC using low resolution MS/MS in order to confirm the presence of diagnostic fragment ions, m/z 139, 155 and 196 in each treatment. Due to the high complexity of the bariated DOMHC mixture, Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS/MS) was employed to obtain molecular level information for both irradiated and dark treatments. The irradiated DOMHC treatments had more bariated oxygenated species over a wide range of H/C and O/C when compared to the dark controls. Doubly bariated species were also observed in DOMHC, which provides evidence that photochemistry transforms DOMHC to even more complex mixtures with multiple oxygenations per molecule. This study provides evidence that barium adduct mass spectrometry can be successfully applied to DOMHC screening for the presence of COOHs, both in dark samples and solar irradiated samples. Furthermore, direct evidence and molecular composition of aqueous phase crude oil photoproducts is provided by this technique.
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Affiliation(s)
- Phoebe Zito
- Department of Chemistry, University of New Orleans, New Orleans, Louisiana 70148, USA. and Pontchartrain Institute for Environmental Sciences, Chemical Analysis & Mass Spectrometry Facility, University of New Orleans, New Orleans, Louisiana 70148, USA
| | - Donald F Smith
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310, USA
| | - Xian Cao
- Department of Chemistry, University of New Orleans, New Orleans, Louisiana 70148, USA.
| | - Rana Ghannam
- Department of Chemistry, University of New Orleans, New Orleans, Louisiana 70148, USA. and Pontchartrain Institute for Environmental Sciences, Chemical Analysis & Mass Spectrometry Facility, University of New Orleans, New Orleans, Louisiana 70148, USA
| | - Matthew A Tarr
- Department of Chemistry, University of New Orleans, New Orleans, Louisiana 70148, USA.
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9
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Teramoto EH, Vogt C, Martins Baessa MP, Polese L, Soriano AU, Chang HK, Richnow HH. Dynamics of hydrocarbon mineralization characterized by isotopic analysis at a jet-fuel-contaminated site in subtropical climate. JOURNAL OF CONTAMINANT HYDROLOGY 2020; 234:103684. [PMID: 32711211 DOI: 10.1016/j.jconhyd.2020.103684] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2019] [Revised: 06/24/2020] [Accepted: 07/14/2020] [Indexed: 06/11/2023]
Abstract
Release of benzene, toluene, ethylbenzene, and xylene (BTEX) as components of the light non-aqueous phase liquids (LNAPL) contaminates soil and groundwater. Assessing the mechanisms of degradation and mineralization of BTEX in groundwater helps understand the migration of the dissolved plume, enabling the reduction of risks to humans. Here, we studied the fate of ethylbezene, m,p-xylenes and o-xylenes and the accompanying formation of methane in a Cenozoic lateritic aquifer in Brazil by compound-specific carbon stable isotope analysis (CSIA), to gain insights into the complex dynamics of release and biodegradation of BTEX in the LNAPL source zone. The enrichment of ∂13C in aromatic compounds dissolved in groundwater compared to the corresponding compounds in LNAPL indicate that CSIA can provide valuable information regarding biodegradation. The isotopic analysis of methane provides direct indication of oxidation mediated by aquifer oxygenation. The ∂13C-CO2 values indicate methanogenesis prevailing at the border and aerobic biodegradation in the center of the LNAPL source zone. Importantly, the isotopic results allowed major improvements in the previously developed conceptual model, supporting the existence of oxic and anoxic environments within the LNAPL source zone.
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Affiliation(s)
- Elias Hideo Teramoto
- São Paulo State University, UNESP, Environmental Studies Center (CEA) and Basin Studies Laboratory (LEBAC), Rio Claro, Brazil
| | - Carsten Vogt
- Helmholtz Centre for Environmental Research - UFZ, Leipzig, Germany
| | | | - Luciana Polese
- São Paulo State University, UNESP, Environmental Studies Center (CEA) and Basin Studies Laboratory (LEBAC), Rio Claro, Brazil
| | | | - Hung Kiang Chang
- São Paulo State University, UNESP, Environmental Studies Center (CEA) and Basin Studies Laboratory (LEBAC), Rio Claro, Brazil; São Paulo State University, UNESP, Dept. of Applied Geology, Rio Claro, Brazil.
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10
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Zimmermann J, Halloran LJS, Hunkeler D. Tracking chlorinated contaminants in the subsurface using compound-specific chlorine isotope analysis: A review of principles, current challenges and applications. CHEMOSPHERE 2020; 244:125476. [PMID: 31830644 DOI: 10.1016/j.chemosphere.2019.125476] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2019] [Revised: 11/20/2019] [Accepted: 11/25/2019] [Indexed: 06/10/2023]
Abstract
Many chlorinated hydrocarbons have gained notoriety as persistent organic pollutants in the environment. Engineered and natural remediation efforts require a monitoring tool to track the progress of degradation processes. Compound-specific isotope analysis (CSIA) is a robust method to evaluate the origin and fate of contaminants in the environment and does not rely on concentration measurements. While carbon CSIA has established itself in the routine assessment of contaminated sites, studies incorporating chlorine isotopes have only recently become more common. Although some aspects of chlorine isotope analysis are more challenging than carbon isotope analysis, having additional isotopic data yields valuable information for contaminated site management. This review provides an overview of chlorine isotope fractionation of chlorinated contaminants in the subsurface by different processes and presents analytical techniques and unresolved challenges in chlorine isotope analysis. A summary of successful field applications illustrates the potential of using chlorine isotope data. Finally, approaches in modelling chlorine isotope fractionation due to degradation, diffusion, and sorption processes are discussed.
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Affiliation(s)
- Jeremy Zimmermann
- Centre for Hydrogeology and Geothermics, University of Neuchâtel, Rue Emile-Argand 11, CH-2000, Neuchâtel, Switzerland.
| | - Landon J S Halloran
- Centre for Hydrogeology and Geothermics, University of Neuchâtel, Rue Emile-Argand 11, CH-2000, Neuchâtel, Switzerland
| | - Daniel Hunkeler
- Centre for Hydrogeology and Geothermics, University of Neuchâtel, Rue Emile-Argand 11, CH-2000, Neuchâtel, Switzerland
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11
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Murray A, Maillard J, Rolle M, Broholm M, Holliger C. Impact of iron- and/or sulfate-reduction on a cis-1,2-dichloroethene and vinyl chloride respiring bacterial consortium: experiments and model-based interpretation. ENVIRONMENTAL SCIENCE. PROCESSES & IMPACTS 2020; 22:740-750. [PMID: 32003373 DOI: 10.1039/c9em00544g] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Process understanding of microbial communities containing organohalide-respiring bacteria (OHRB) is important for effective bioremediation of chlorinated ethenes. The impact of iron and sulfate reduction on cis-1,2-dichloroethene (cDCE) and vinyl chloride (VC) dechlorination by a consortium containing the OHRB Dehalococcoides spp. was investigated using multiphase batch experiments. The OHRB consortium was found to contain endogenous iron- and sulfate-reducing bacteria (FeRB and SRB). A biogeochemical model was developed and used to quantify the mass transfer, aquatic geochemical, and microbial processes that occurred in the multiphase batch system. It was determined that the added SRB had the most significant impact on contaminant degradation. Addition of the SRB increased maximum specific substrate utilization rates, kmax, of cDCE and VC by 129% and 294%, respectively. The added FeRB had a slight stimulating effect on VC dechlorination when exogenous SRB were absent, but when cultured with the added SRB, FeRB moderated the SRB's stimulating effect. This study demonstrates that subsurface microbial community interactions are more complex than categorical, guild-based competition for resources such as electron donor.
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Affiliation(s)
- Alexandra Murray
- Department of Environmental Engineering, Technical University of Denmark, Bld 115, 2800 Lyngby, DK-2800, Denmark.
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12
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Chen S, Zhang K, Jha RK, Ma L. Impact of atrazine concentration on bioavailability and apparent isotope fractionation in Gram-negative Rhizobium sp. CX-Z. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2020; 257:113614. [PMID: 31761577 DOI: 10.1016/j.envpol.2019.113614] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2019] [Revised: 11/10/2019] [Accepted: 11/10/2019] [Indexed: 06/10/2023]
Abstract
Compound-specific stable isotope analysis of micropollutants has become an established method for the qualitative and quantitative assessment of biodegradation in the field. However, many of environmental factors may have an influence on the observed isotope fractionation. Herein, we investigate the impact of substrate concentration on the observed enrichment factor derived from Rayleigh plot of batch laboratory experiments conducted to measure the atrazine carbon isotope fractionation of Rhizobium sp. CX-Z subjected to the different initial concentration level of atrazine. The Rayleigh plot (changes in bulk concentration vs. isotopic composition) derived from batch experiments shown divergence from the linear relation towards the end of degradation, confirming bioavailability of atrazine changed along with the decay of substrate concentration, consequently, influenced the isotope fractionation and lowered the observed enrichment factor. When microbial degradation is coupled to a mass transfer step limiting the bioavailability of substrate, the observed enrichment factor displays a dependence on initial atrazine concentration. Observed enrichment factors (ε) (absolute value) derived from the low concentration (i.e. 9.5 μM) are below 3.5‰ to the value of -5.4‰ determined at high bioavailability (membrane-free cells). The observed enrichment factor depended significantly on the atrazine concentration, indicating the concentration level and the bioavailability of a substrate in realistic environments should be considered during the assessment of microbial degradation or in situ bioremediation based on compound-specific stable isotope analysis (CSIA) method.
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Affiliation(s)
- Songsong Chen
- State Key Laboratory of Pollution Control and Resources Reuse, Tongji University, Shanghai 200092, China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, PR China
| | - Kai Zhang
- State Key Laboratory of Pollution Control and Resources Reuse, Tongji University, Shanghai 200092, China
| | - Rohit Kumar Jha
- State Key Laboratory of Pollution Control and Resources Reuse, Tongji University, Shanghai 200092, China
| | - Limin Ma
- State Key Laboratory of Pollution Control and Resources Reuse, Tongji University, Shanghai 200092, China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, PR China.
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13
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Qian Y, Chen K, Liu Y, Li J. Assessment of hexachlorcyclohexane biodegradation in contaminated soil by compound-specific stable isotope analysis. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2019; 254:113008. [PMID: 31400667 DOI: 10.1016/j.envpol.2019.113008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2019] [Revised: 08/01/2019] [Accepted: 08/02/2019] [Indexed: 06/10/2023]
Abstract
Compound-specific isotope analysis (CSIA) was firstly applied to explore the biodegradation of hexachlorcyclohexane (HCH) isomers in contaminated soil. Concentrations and compound-specific carbon isotope ratio profiles of HCH in different specific ex-situ pilot-scale contaminated soil mesocosms were determined. The addition of nutrients and Sphingobium spp. significantly enhanced the degradation of HCH in contaminated soils within 90 days. Isomer specific biodegradation of HCHs was observed with α- and γ-HCH being more degradable than β and δ-HCH. Stable carbon isotope fractionation of HCH was observed and the δ13C values shifted from -28.8 ± 0.3‰ to -24.8 ± 0.7‰ upon 87.3% removal, -27.9 ± 0.2‰ to -25.9 ± 0.5‰ upon 72.8% removal, -29.4 ± 0.3‰ to -19.9 ± 0.6‰ upon 95.8% removal, and -27.8 ± 0.5‰ to -23.6 ± 0.7‰ after 96.9% removal for α, β, γ, and δ-HCH, respectively. Furthermore, the enrichment factor ε for α, β, γ, and δ-HCH biodegradation in soil was obtained for the first time as -2.0‰, -1.5‰, -3.2‰, and -1.4‰, which could play a critical role in assessing in situ biodegradation of HCH isomers in field site soil. Results from ex-situ pilot-scale experiments clearly demonstrated that CSIA could be a promising tool to qualitatively and quantitatively evaluate in situ biodegradation of HCH in contaminated field site.
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Affiliation(s)
- Yiguang Qian
- Shenzhen Key Laboratory of Environmental Chemistry and Ecological Remediation, College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen 518060, China
| | - Ke Chen
- College of Resources and Environmental Science, South-Central University for Nationalities, Wuhan 430074, China
| | - Yaqing Liu
- UFZ, Helmholtz Centre for Environmental Research, Department of Isotope Biogeochemistry, Permoserstr.15, 04318 Leipzig, Germany
| | - Juying Li
- Shenzhen Key Laboratory of Environmental Chemistry and Ecological Remediation, College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen 518060, China.
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14
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Murray AM, Maillard J, Jin B, Broholm MM, Holliger C, Rolle M. A modeling approach integrating microbial activity, mass transfer, and geochemical processes to interpret biological assays: An example for PCE degradation in a multi-phase batch setup. WATER RESEARCH 2019; 160:484-496. [PMID: 31177078 DOI: 10.1016/j.watres.2019.05.087] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2019] [Revised: 05/22/2019] [Accepted: 05/25/2019] [Indexed: 06/09/2023]
Abstract
The rate at which organic contaminants can be degraded in aquatic environments is not only dependent upon specific degrading bacteria, but also upon the composition of the microbial community, mass transfer of the contaminant, and abiotic processes that occur in the environment. In this study, we present three-phase batch experiments of tetrachloroethene (PCE) degradation by a consortium of organohalide-respiring bacteria, cultivated alone or in communities with iron- and/or sulfate-reducers. We developed a modeling approach to quantitatively evaluate the experimental results, comprised of chemical and biomolecular time series data. The model utilizes the IPhreeqc module to couple multi-phase mass transfer between gaseous, organic and aqueous phases with microbial and aquatic geochemical processes described using the geochemical code PHREEQC. The proposed approach is able to capture the contaminant degradation, the microbial population dynamics, the effects of multi-phase kinetic mass transfer and sample removal, and the geochemical reactions occurring in the aqueous phase. The model demonstrates the importance of aqueous speciation and abiotic reactions on the bioavailability of the substrates. The model-based interpretation allowed us to quantify the reaction kinetics of the different bacterial guilds. The model further revealed that the inclusion of sulfate-reducing bacteria lowers the rate of PCE degradation and that this effect is moderated in the presence of iron-reducing bacteria.
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Affiliation(s)
- Alexandra Marie Murray
- Department of Environmental Engineering, Technical University of Denmark, Kgs. Lyngby, DK-2800, Denmark
| | - Julien Maillard
- Laboratory for Environmental Biotechnology, ENAC-IIE, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
| | - Biao Jin
- State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Science, China
| | - Mette M Broholm
- Department of Environmental Engineering, Technical University of Denmark, Kgs. Lyngby, DK-2800, Denmark
| | - Christof Holliger
- Laboratory for Environmental Biotechnology, ENAC-IIE, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
| | - Massimo Rolle
- Department of Environmental Engineering, Technical University of Denmark, Kgs. Lyngby, DK-2800, Denmark.
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15
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Marozava S, Meyer AH, Pérez-de-Mora A, Gharasoo M, Zhuo L, Wang H, Cirpka OA, Meckenstock RU, Elsner M. Mass Transfer Limitation during Slow Anaerobic Biodegradation of 2-Methylnaphthalene. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2019; 53:9481-9490. [PMID: 31262174 DOI: 10.1021/acs.est.9b01152] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Affiliation(s)
- Sviatlana Marozava
- Institute of Groundwater Ecology, Helmholtz Zentrum München-German Research Center for Environmental Health, Ingolstädter Landstrasse 1, D-85764 Neuherberg, Germany
| | - Armin H. Meyer
- Institute of Groundwater Ecology, Helmholtz Zentrum München-German Research Center for Environmental Health, Ingolstädter Landstrasse 1, D-85764 Neuherberg, Germany
| | - Alfredo Pérez-de-Mora
- Institute of Groundwater Ecology, Helmholtz Zentrum München-German Research Center for Environmental Health, Ingolstädter Landstrasse 1, D-85764 Neuherberg, Germany
| | - Mehdi Gharasoo
- Institute of Groundwater Ecology, Helmholtz Zentrum München-German Research Center for Environmental Health, Ingolstädter Landstrasse 1, D-85764 Neuherberg, Germany
- University of Waterloo, Department of Earth and Environmental Sciences, Ecohydrology, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada
| | - Lin Zhuo
- Institute of Groundwater Ecology, Helmholtz Zentrum München-German Research Center for Environmental Health, Ingolstädter Landstrasse 1, D-85764 Neuherberg, Germany
| | - He Wang
- Institute of Groundwater Ecology, Helmholtz Zentrum München-German Research Center for Environmental Health, Ingolstädter Landstrasse 1, D-85764 Neuherberg, Germany
| | - Olaf A. Cirpka
- University of Tübingen, Center for Applied Geoscience, Hölderlinstrasse 12, 72074 Tübingen, Germany
| | - Rainer U. Meckenstock
- University Duisburg-Essen, Biofilm Centre, Universitätsstrasse 5, D-45141 Essen, Germany
| | - Martin Elsner
- Institute of Groundwater Ecology, Helmholtz Zentrum München-German Research Center for Environmental Health, Ingolstädter Landstrasse 1, D-85764 Neuherberg, Germany
- Technical University of Munich, Chair of Analytical Chemistry and Water Chemistry, Marchioninistrasse 17, 81377 Munich, Germany
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16
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Heckel B, Phillips E, Edwards E, Sherwood Lollar B, Elsner M, Manefield MJ, Lee M. Reductive Dehalogenation of Trichloromethane by Two Different Dehalobacter restrictus Strains Reveal Opposing Dual Element Isotope Effects. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2019; 53:2332-2343. [PMID: 30726673 DOI: 10.1021/acs.est.8b03717] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Trichloromethane (TCM) is a frequently detected and persistent groundwater contaminant. Recent studies have reported that two closely related Dehalobacter strains (UNSWDHB and CF) transform TCM to dichloromethane, with inconsistent carbon isotope effects (ε13CUNSWDHB = -4.3 ± 0.45‰; ε13CCF = -27.5 ± 0.9‰). This study uses dual element compound specific isotope analysis (C; Cl) to explore the underlying differences. TCM transformation experiments using strain CF revealed pronounced normal carbon and chlorine isotope effects (ε13CCF = -27.9 ± 1.7‰; ε37ClCF = -4.2 ± 0.2‰). In contrast, small carbon and unprecedented inverse chlorine isotope effects were observed for strain UNSWDHB (ε13CUNSWDHB = -3.1 ± 0.5‰; ε37ClUNSWDHB = 2.5 ± 0.3‰) leading to opposing dual element isotope slopes (λCF = 6.64 ± 0.14 vs λUNSWDHB = -1.20 ± 0.18). Isotope effects of strain CF were identical to experiments with TCM and Vitamin B12 (ε13CVitamin B12 = -26.0 ± 0.9‰, ε37ClVitamin B12 = -4.0 ± 0.2‰, λVitamin B12 = 6.46 ± 0.20). Comparison to previously reported isotope effects suggests outer-sphere-single-electron transfer or SN2 as possible underlying mechanisms. Cell suspension and cell free extract experiments with strain UNSWDHB were both unable to unmask the intrinsic KIE of the reductive dehalogenase (TmrA) suggesting that enzyme binding and/or mass-transfer into the periplasm were rate-limiting. Nondirected intermolecular interactions of TCM with cellular material were ruled out as reason for the inverse isotope effect by gas/water and gas/hexadecane partitioning experiments indicating specific, yet uncharacterized interactions must be operating prior to catalysis.
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Affiliation(s)
- Benjamin Heckel
- Institute of Groundwater Ecology , Helmholtz Zentrum München , Ingolstädter Landstr. 1 , 85764 Neuherberg , Germany
- Chair of Analytical Chemistry and Water Chemistry , Technical University of Munich , Marchioninistrasse 17 , D-81377 Munich , Germany
| | - Elizabeth Phillips
- Department of Earth Sciences 22 Russell St , University of Toronto , Toronto Ontario M5S 3B1 , Canada
| | - Elizabeth Edwards
- Department of Chemical Engineering and Applied Chemistry , University of Toronto , Toronto , Ontario M5S 3E5 , Canada
| | - Barbara Sherwood Lollar
- Department of Earth Sciences 22 Russell St , University of Toronto , Toronto Ontario M5S 3B1 , Canada
| | - Martin Elsner
- Institute of Groundwater Ecology , Helmholtz Zentrum München , Ingolstädter Landstr. 1 , 85764 Neuherberg , Germany
- Chair of Analytical Chemistry and Water Chemistry , Technical University of Munich , Marchioninistrasse 17 , D-81377 Munich , Germany
| | - Michael J Manefield
- School of Civil and Environmental Engineering, Water Research Centre (WRC) , University of New South Wales , Sydney , New South Wales 2052 , Australia
| | - Matthew Lee
- School of Civil and Environmental Engineering, Water Research Centre (WRC) , University of New South Wales , Sydney , New South Wales 2052 , Australia
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17
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Gharasoo M, Ehrl BN, Cirpka OA, Elsner M. Modeling of Contaminant Biodegradation and Compound-Specific Isotope Fractionation in Chemostats at Low Dilution Rates. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2019; 53:1186-1196. [PMID: 30339002 PMCID: PMC6986770 DOI: 10.1021/acs.est.8b02498] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2018] [Revised: 10/17/2018] [Accepted: 10/19/2018] [Indexed: 05/06/2023]
Abstract
We present a framework to model microbial transformations in chemostats and retentostats under transient or quasi-steady state conditions. The model accounts for transformation-induced isotope fractionation and mass-transfer across the cell membrane. It also verifies that the isotope fractionation ϵ can be evaluated as the difference of substrate-specific isotope ratios between inflow and outflow. We explicitly considered that the dropwise feeding of substrate into the reactor at very low dilution rates leads to transient behavior of concentrations and transformation rates and use this information to validate conditions under which a quasi-steady state treatment is justified. We demonstrate the practicality of the code by modeling a chemostat experiment of atrazine degradation at low dilution/growth rates by the strain Arthrobacter aurescens TC1. Our results shed light on the interplay of processes that control biodegradation and isotope fractionation of contaminants at low (μg/L) concentration levels. With the help of the model, an estimate of the mass-transfer coefficient of atrazine through the cell membrane was achieved (0.0025 s-1).
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Affiliation(s)
- Mehdi Gharasoo
- Technical
University of Munich, Chair of Analytical
Chemistry and Water Chemistry, Marchioninistrasse 17, 81377 Munich, Germany
- Helmholtz
Zentrum München, Institute of Groundwater
Ecology, Ingolstädter
Landstrasse 1, 85764 Neuherberg, Germany
| | - Benno N. Ehrl
- Helmholtz
Zentrum München, Institute of Groundwater
Ecology, Ingolstädter
Landstrasse 1, 85764 Neuherberg, Germany
| | - Olaf A. Cirpka
- University
of Tubingen, Center for Applied
Geoscience, Hölderlinstrasse
12, 72074 Tübingen, Germany
| | - Martin Elsner
- Technical
University of Munich, Chair of Analytical
Chemistry and Water Chemistry, Marchioninistrasse 17, 81377 Munich, Germany
- Helmholtz
Zentrum München, Institute of Groundwater
Ecology, Ingolstädter
Landstrasse 1, 85764 Neuherberg, Germany
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18
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Ehrl B, Kundu K, Gharasoo M, Marozava S, Elsner M. Rate-Limiting Mass Transfer in Micropollutant Degradation Revealed by Isotope Fractionation in Chemostat. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2019; 53:1197-1205. [PMID: 30514083 PMCID: PMC6365907 DOI: 10.1021/acs.est.8b05175] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2018] [Revised: 12/03/2018] [Accepted: 12/05/2018] [Indexed: 05/05/2023]
Abstract
Biodegradation of persistent micropollutants like pesticides often slows down at low concentrations (μg/L) in the environment. Mass transfer limitations or physiological adaptation are debated to be responsible. Although promising, evidence from compound-specific isotope fractionation analysis (CSIA) remains unexplored for bacteria adapted to this low concentration regime. We accomplished CSIA for degradation of a persistent pesticide, atrazine, during cultivation of Arthrobacter aurescens TC1 in chemostat under four different dilution rates leading to 82, 62, 45, and 32 μg/L residual atrazine concentrations. Isotope analysis of atrazine in chemostat experiments with whole cells revealed a drastic decrease in isotope fractionation with declining residual substrate concentration from ε(C) = -5.36 ± 0.20‰ at 82 μg/L to ε(C) = -2.32 ± 0.28‰ at 32 μg/L. At 82 μg/L ε(C) represented the full isotope effect of the enzyme reaction. At lower residual concentrations smaller ε(C) indicated that this isotope effect was masked indicating that mass transfer across the cell membrane became rate-limiting. This onset of mass transfer limitation appeared in a narrow concentration range corresponding to about 0.7 μM assimilable carbon. Concomitant changes in cell morphology highlight the opportunity to study the role of this onset of mass transfer limitation on the physiological level in cells adapted to low concentrations.
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Affiliation(s)
- Benno
N. Ehrl
- Institute
of Groundwater Ecology, Helmholtz Zentrum
München, Ingolstädter
Landstrasse 1, 85764 Neuherberg, Germany
| | - Kankana Kundu
- Institute
of Groundwater Ecology, Helmholtz Zentrum
München, Ingolstädter
Landstrasse 1, 85764 Neuherberg, Germany
| | - Mehdi Gharasoo
- Institute
of Groundwater Ecology, Helmholtz Zentrum
München, Ingolstädter
Landstrasse 1, 85764 Neuherberg, Germany
| | - Sviatlana Marozava
- Institute
of Groundwater Ecology, Helmholtz Zentrum
München, Ingolstädter
Landstrasse 1, 85764 Neuherberg, Germany
| | - Martin Elsner
- Institute
of Groundwater Ecology, Helmholtz Zentrum
München, Ingolstädter
Landstrasse 1, 85764 Neuherberg, Germany
- Chair
of Analytical Chemistry and Water Chemistry, Technical University of Munich, Marchioninistrasse 17, 81377 Munich, Germany
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19
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Badin A, Braun F, Halloran LJS, Maillard J, Hunkeler D. Modelling of C/Cl isotopic behaviour during chloroethene biotic reductive dechlorination: Capabilities and limitations of simplified and comprehensive models. PLoS One 2018; 13:e0202416. [PMID: 30133496 PMCID: PMC6104987 DOI: 10.1371/journal.pone.0202416] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2018] [Accepted: 08/02/2018] [Indexed: 11/30/2022] Open
Abstract
Predicting the fate of chloroethenes in groundwater is essential when evaluating remediation strategies. Such predictions are expected to be more accurate when incorporating isotopic parameters. Although secondary chlorine isotope effects have been observed during reductive dechlorination of chloroethenes, development of modelling frameworks and simulation has thus far been limited. We have developed a novel mathematical framework to simulate the C/Cl isotopic fractionation during reductive dechlorination of chloroethenes. This framework differs from the existing state of the art by incorporating secondary isotopic effects and considering both C and Cl isotopes simultaneously. A comprehensive general model (GM), which is expected to be the closest representation of reality thus far investigated, was implemented. A less computationally intensive simplified model (SM), with the potential for use in modelling of complex reactive transport scenarios, was subsequently validated based on its comparison to GM. The approach of GM considers all isotopocules (i.e. molecules differing in number and position of heavy and light isotopes) of each chloroethene as individual species, of which each is degraded at a different rate. Both models GM and SM simulated plausible C/Cl isotopic compositions of tetrachloroethene (PCE), trichloroethene (TCE) and cis-1,2-dichloroethene (cDCE) during sequential dechlorination when using experimentally relevant kinetic and isotopic parameters. The only major difference occurred in the case where different secondary isotopic effects occur at the different non-reacting positions when PCE is dechlorinated down to cDCE. This observed discrepancy stems from the unequal Cl isotope distribution in TCE that arises due to the occurrence of differential secondary Cl isotopic effects during transformation of PCE to TCE. Additionally, these models are shown to accurately reproduce experimental data obtained during reductive dechlorination by bacterial enrichments harbouring Sulfurospirillum spp. where secondary isotope effects are known to have occurred. These findings underscore a promising future for the development of reactive transport models that incorporate isotopic parameters.
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Affiliation(s)
- Alice Badin
- University of Neuchâtel, Centre for Hydrogeology & Geothermics (CHYN), Neuchâtel, Switzerland
| | - Fabian Braun
- Swiss Center for Electronics and Microtechnology (CSEM), Systems Division, Neuchâtel, Switzerland
- Ecole Polytechnique Fédérale de Lausanne (EPFL), Signal Processing Laboratory (LTS5), Lausanne, Switzerland
| | - Landon J. S. Halloran
- University of Neuchâtel, Centre for Hydrogeology & Geothermics (CHYN), Neuchâtel, Switzerland
- * E-mail: (LJSH); (DH)
| | - Julien Maillard
- Ecole Polytechnique Fédérale de Lausanne (EPFL), Laboratory for Environmental Biotechnology, Lausanne, Switzerland
| | - Daniel Hunkeler
- University of Neuchâtel, Centre for Hydrogeology & Geothermics (CHYN), Neuchâtel, Switzerland
- * E-mail: (LJSH); (DH)
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20
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Chen G, Shouakar-Stash O, Phillips E, Justicia-Leon SD, Gilevska T, Sherwood Lollar B, Mack EE, Seger ES, Löffler FE. Dual Carbon-Chlorine Isotope Analysis Indicates Distinct Anaerobic Dichloromethane Degradation Pathways in Two Members of Peptococcaceae. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2018; 52:8607-8616. [PMID: 29975517 DOI: 10.1021/acs.est.8b01583] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Dichloromethane (DCM) is a probable human carcinogen and frequent groundwater contaminant and contributes to stratospheric ozone layer depletion. DCM is degraded by aerobes harboring glutathione-dependent DCM dehalogenases; however, DCM contamination occurs in oxygen-deprived environments, and much less is known about anaerobic DCM metabolism. Some members of the Peptococcaceae family convert DCM to environmentally benign products including acetate, formate, hydrogen (H2), and inorganic chloride under strictly anoxic conditions. The current study applied stable carbon and chlorine isotope fractionation measurements to the axenic culture Dehalobacterium formicoaceticum and to the consortium RM comprising DCM degrader Candidatus Dichloromethanomonas elyunquensis. Degradation-associated carbon and chlorine isotope enrichment factors (εC and εCl) of -42.4 ± 0.7‰ and -5.3 ± 0.1‰, respectively, were measured in D. formicoaceticum cultures. A similar εCl of -5.2 ± 0.1‰, but a substantially lower εC of -18.3 ± 0.2‰, were determined for Ca. Dichloromethanomonas elyunquensis. The εC and εCl values resulted in distinctly different dual element C-Cl isotope correlations (ΛC/Cl = Δδ13C/Δδ37Cl) of 7.89 ± 0.12 and 3.40 ± 0.03 for D. formicoaceticum and Ca. Dichloromethanomonas elyunquensis, respectively. The distinct ΛC/Cl values obtained for the two cultures imply mechanistically distinct C-Cl bond cleavage reactions, suggesting that members of Peptococcaceae employ different pathways to metabolize DCM. These findings emphasize the utility of dual carbon-chlorine isotope analysis to pinpoint DCM degradation mechanisms and to provide an additional line of evidence that detoxification is occurring at DCM-contaminated sites.
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Affiliation(s)
- Gao Chen
- Center for Environmental Biotechnology, Department of Civil and Environmental Engineering, and Department of Microbiology , University of Tennessee , Knoxville , Tennessee 37996 , United States
| | - Orfan Shouakar-Stash
- Isotope Tracer Technologies Inc. (IT2) , Waterloo , Ontario N2 V 1Z5 , Canada
- Department of Earth and Environmental Sciences , University of Waterloo , Waterloo , Ontario N2L 3G1 , Canada
- School of Engineering , University of Guelph , Guelph , Ontario N1G 2W1 , Canada
| | - Elizabeth Phillips
- Department of Earth Sciences , University of Toronto , Toronto , Ontario M5S 3B1 , Canada
| | - Shandra D Justicia-Leon
- School of Biology , Georgia Institute of Technology , Atlanta , Georgia 30332 , United States
| | - Tetyana Gilevska
- Department of Earth Sciences , University of Toronto , Toronto , Ontario M5S 3B1 , Canada
| | | | - E Erin Mack
- DuPont Corporate Remediation Group , E. I. DuPont de Nemours and Company , Wilmington , Delaware 19805 , United States
| | - Edward S Seger
- The Chemours Company , Wilmington , Delaware 19899 , United States
| | - Frank E Löffler
- Center for Environmental Biotechnology, Department of Civil and Environmental Engineering, and Department of Microbiology , University of Tennessee , Knoxville , Tennessee 37996 , United States
- Oak Ridge National Laboratory (UT-ORNL) Joint Institute for Biological Sciences (JIBS) and Biosciences Division , University of Tennessee and Oak Ridge National Laboratory , Oak Ridge , Tennessee 37831 , United States
- Department of Biosystems Engineering and Soil Science , University of Tennessee , Knoxville , Tennessee 37996 , United States
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21
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Buttet GF, Murray AM, Goris T, Burion M, Jin B, Rolle M, Holliger C, Maillard J. Coexistence of two distinct Sulfurospirillum populations respiring tetrachloroethene—genomic and kinetic considerations. FEMS Microbiol Ecol 2018. [DOI: 10.1093/femsec/fiy018] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Géraldine Florence Buttet
- Ecole Polytechnique Fédérale de Lausanne (EPFL), School of Architecture, Civil and Environmental Engineering, Laboratory for Environmental Biotechnology, Station 6, CH-1015 Lausanne, Switzerland
| | - Alexandra Marie Murray
- DTU Environment, Department of Environmental Engineering, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
| | - Tobias Goris
- Department of Applied and Ecological Microbiology, Institute of Microbiology, Friedrich Schiller University, Philosophenweg 12, 07743 Jena, Germany
| | - Mélissa Burion
- Ecole Polytechnique Fédérale de Lausanne (EPFL), School of Architecture, Civil and Environmental Engineering, Laboratory for Environmental Biotechnology, Station 6, CH-1015 Lausanne, Switzerland
| | - Biao Jin
- DTU Environment, Department of Environmental Engineering, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
| | - Massimo Rolle
- DTU Environment, Department of Environmental Engineering, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
| | - Christof Holliger
- Ecole Polytechnique Fédérale de Lausanne (EPFL), School of Architecture, Civil and Environmental Engineering, Laboratory for Environmental Biotechnology, Station 6, CH-1015 Lausanne, Switzerland
| | - Julien Maillard
- Ecole Polytechnique Fédérale de Lausanne (EPFL), School of Architecture, Civil and Environmental Engineering, Laboratory for Environmental Biotechnology, Station 6, CH-1015 Lausanne, Switzerland
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22
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Pati SG, Kohler HPE, Hofstetter TB. Characterization of Substrate, Cosubstrate, and Product Isotope Effects Associated With Enzymatic Oxygenations of Organic Compounds Based on Compound-Specific Isotope Analysis. Methods Enzymol 2017; 596:291-329. [PMID: 28911775 DOI: 10.1016/bs.mie.2017.06.044] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Enzymatic oxygenations are among the most important biodegradation and detoxification reactions of organic pollutants. In the environment, however, such natural attenuation processes are extremely difficult to monitor. Changes of stable isotope ratios of aromatic pollutants at natural isotopic abundances serve as proxies for isotope effects associated with oxygenation reactions. Such isotope fractionations offer new avenues for revealing the pathway and extent of pollutant transformation and provide new insights into the mechanisms of catalysis by Rieske non-heme ferrous iron oxygenases. Based on compound-specific C, H, N, and O isotope analysis, we present a comprehensive methodology with which isotope effects can be derived from the isotope fractionation measured in substrates, the cosubstrate O2, and organic oxygenation products. We use dioxygenation of nitrobenzene and 2-nitrotoluene by nitrobenzene dioxygenase as illustrative examples to introduce different mathematical procedures for deriving apparent substrate and product isotope effects. We present two experimental approaches to control reactant and product turnover for isotope fractionation analysis in experimental systems containing purified enzymes, E. coli clones, and pure strains of environmental microorganisms. Finally, we present instrumental procedures and sample treatment instructions for analysis of C, H, and N isotope analysis in organic compounds and O isotope analysis in aqueous O2 by gas and liquid chromatography coupled to isotope ratio mass spectrometry.
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Affiliation(s)
- Sarah G Pati
- Eawag, Swiss Federal Institute of Aquatic Science and Technology, Dübendorf, Switzerland; Institute of Biogeochemistry and Pollutant Dynamics (IBP), ETH Zürich, Zürich, Switzerland
| | - Hans-Peter E Kohler
- Eawag, Swiss Federal Institute of Aquatic Science and Technology, Dübendorf, Switzerland
| | - Thomas B Hofstetter
- Eawag, Swiss Federal Institute of Aquatic Science and Technology, Dübendorf, Switzerland; Institute of Biogeochemistry and Pollutant Dynamics (IBP), ETH Zürich, Zürich, Switzerland.
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23
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Van Breukelen BM, Thouement HAA, Stack PE, Vanderford M, Philp P, Kuder T. Modeling 3D-CSIA data: Carbon, chlorine, and hydrogen isotope fractionation during reductive dechlorination of TCE to ethene. JOURNAL OF CONTAMINANT HYDROLOGY 2017; 204:79-89. [PMID: 28764859 DOI: 10.1016/j.jconhyd.2017.07.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2017] [Revised: 07/14/2017] [Accepted: 07/15/2017] [Indexed: 06/07/2023]
Abstract
Reactive transport modeling of multi-element, compound-specific isotope analysis (CSIA) data has great potential to quantify sequential microbial reductive dechlorination (SRD) and alternative pathways such as oxidation, in support of remediation of chlorinated solvents in groundwater. As a key step towards this goal, a model was developed that simulates simultaneous carbon, chlorine, and hydrogen isotope fractionation during SRD of trichloroethene, via cis-1,2-dichloroethene (and trans-DCE as minor pathway), and vinyl chloride to ethene, following Monod kinetics. A simple correction term for individual isotope/isotopologue rates avoided multi-element isotopologue modeling. The model was successfully validated with data from a mixed culture Dehalococcoides microcosm. Simulation of Cl-CSIA required incorporation of secondary kinetic isotope effects (SKIEs). Assuming a limited degree of intramolecular heterogeneity of δ37Cl in TCE decreased the magnitudes of SKIEs required at the non-reacting Cl positions, without compromising the goodness of model fit, whereas a good fit of a model involving intramolecular CCl bond competition required an unlikely degree of intramolecular heterogeneity. Simulation of H-CSIA required SKIEs in H atoms originally present in the reacting compounds, especially for TCE, together with imprints of strongly depleted δ2H during protonation in the products. Scenario modeling illustrates the potential of H-CSIA for source apportionment.
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Affiliation(s)
- Boris M Van Breukelen
- Department of Water Management, Delft University of Technology, Stevinweg 1, 2628 CN Delft, The Netherlands.
| | - Héloïse A A Thouement
- Department of Water Management, Delft University of Technology, Stevinweg 1, 2628 CN Delft, The Netherlands
| | - Philip E Stack
- Scotland's Rural College (SRUC), Kings Buildings, West Mains Road, Edinburgh, EH9 3JG, UK
| | - Mindy Vanderford
- HydroGeoLogic, Inc., 4407 Jane St., Bellaire, TX 77401, United States
| | - Paul Philp
- School of Geology and Geophysics, University of Oklahoma, 100 E. Boyd Street, SEC 710, Norman, OK 73019, United States
| | - Tomasz Kuder
- School of Geology and Geophysics, University of Oklahoma, 100 E. Boyd Street, SEC 710, Norman, OK 73019, United States
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24
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Buchner D, Jin B, Ebert K, Rolle M, Elsner M, Haderlein SB. Experimental Determination of Isotope Enrichment Factors - Bias from Mass Removal by Repetitive Sampling. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2017; 51:1527-1536. [PMID: 27995793 DOI: 10.1021/acs.est.6b03689] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Application of compound-specific stable isotope approaches often involves comparisons of isotope enrichment factors (ε). Experimental determination of ε-values is based on the Rayleigh equation, which relates the change in measured isotope ratios to the decreasing substrate fractions and is valid for closed systems. Even in well-controlled batch experiments, however, this requirement is not necessarily fulfilled, since repetitive sampling can remove a significant fraction of the analyte. For volatile compounds the need for appropriate corrections is most evident, and various methods have been proposed to account for mass removal and for volatilization into the headspace. In this study we use both synthetic and experimental data to demonstrate that the determination of ε-values according to current correction methods is prone to considerable systematic errors even in well-designed experimental setups. Application of inappropriate methods may lead to incorrect and inconsistent ε-values entailing misinterpretations regarding the processes underlying isotope fractionation. In fact, our results suggest that artifacts arising from inappropriate data evaluation might contribute to the variability of published ε-values. In response, we present novel, adequate methods to eliminate systematic errors in data evaluation. A model-based sensitivity analysis serves to reveal the most crucial experimental parameters and can be used for future experimental design to obtain correct ε-values allowing mechanistic interpretations.
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Affiliation(s)
- Daniel Buchner
- Department of Geosciences, Center for Applied Geosciences, University of Tübingen , Hölderlinstraße 12, D-72074 Tübingen, Germany
| | - Biao Jin
- Department of Geosciences, Center for Applied Geosciences, University of Tübingen , Hölderlinstraße 12, D-72074 Tübingen, Germany
- Department of Environmental Engineering, Technical University of Denmark , Miljøvej Building 113, DK-2800 Kgs. Lyngby, Denmark
| | - Karin Ebert
- Department of Geosciences, Center for Applied Geosciences, University of Tübingen , Hölderlinstraße 12, D-72074 Tübingen, Germany
| | - Massimo Rolle
- Department of Geosciences, Center for Applied Geosciences, University of Tübingen , Hölderlinstraße 12, D-72074 Tübingen, Germany
- Department of Environmental Engineering, Technical University of Denmark , Miljøvej Building 113, DK-2800 Kgs. Lyngby, Denmark
| | - Martin Elsner
- Institute of Groundwater Ecology, Helmholtz Zentrum München , Ingolstädter Landstraße 1, D-85764 Neuherberg, Germany
| | - Stefan B Haderlein
- Department of Geosciences, Center for Applied Geosciences, University of Tübingen , Hölderlinstraße 12, D-72074 Tübingen, Germany
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25
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Nijenhuis I, Richnow HH. Stable isotope fractionation concepts for characterizing biotransformation of organohalides. Curr Opin Biotechnol 2016; 41:108-113. [DOI: 10.1016/j.copbio.2016.06.002] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2016] [Revised: 05/23/2016] [Accepted: 06/06/2016] [Indexed: 12/11/2022]
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26
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Ratti M, Canonica S, McNeill K, Erickson PR, Bolotin J, Hofstetter TB. Isotope fractionation associated with the direct photolysis of 4-chloroaniline. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2015; 49:4263-4273. [PMID: 25719866 DOI: 10.1021/es505784a] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Compound-specific isotope analysis is a useful approach to track transformations of many organic soil and water pollutants. Applications of CSIA to characterize photochemical processes, however, have hardly been explored. In this work, we systematically studied C and N isotope fractionation associated with the direct photolysis of 4-Cl-aniline used as a model compound for organic micropollutants that are known to degrade via photochemical processes. Laboratory experiments were carried out at an irradiation wavelength of 254 nm over the pH range 2.0 to 9.0 as well as in the presence of Cs(+) as a quencher of excited singlet 4-Cl-aniline at pH 7.0 and 9.0. We observed considerable variation of C and N isotope enrichment factors, ϵC and ϵN, between -1.2 ± 0.2‰ to -2.7 ± 0.2‰ for C and -0.6 ± 0.2‰ to -9.1 ± 1.6‰ for N, respectively, which could not be explained by the speciation of 4-Cl-aniline alone. In the presence of 1 M Cs(+), we found a marked increase of apparent (13)C-kinetic isotope effects ((13)C-AKIE) and decrease of 4-Cl-aniline fluorescence lifetimes. Our data suggest that variations of C and N isotope fractionation originate from heterolytic dechlorination of excited triplet and singlet states of 4-Cl-aniline. Linear correlations of (13)C-AKIE vs (15)N-AKIE were distinctly different for these two reaction pathways and may be explored further for the identification of photolytic aromatic dechlorination reactions.
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Affiliation(s)
- Marco Ratti
- †Eawag, Swiss Federal Institute of Aquatic Science and Technology, CH-8600 Dübendorf, Switzerland
- ‡Institute of Biogeochemistry and Pollutant Dynamics (IBP), ETH Zürich, CH-8092 Zürich, Switzerland
| | - Silvio Canonica
- †Eawag, Swiss Federal Institute of Aquatic Science and Technology, CH-8600 Dübendorf, Switzerland
| | - Kristopher McNeill
- ‡Institute of Biogeochemistry and Pollutant Dynamics (IBP), ETH Zürich, CH-8092 Zürich, Switzerland
| | - Paul R Erickson
- ‡Institute of Biogeochemistry and Pollutant Dynamics (IBP), ETH Zürich, CH-8092 Zürich, Switzerland
| | - Jakov Bolotin
- †Eawag, Swiss Federal Institute of Aquatic Science and Technology, CH-8600 Dübendorf, Switzerland
| | - Thomas B Hofstetter
- †Eawag, Swiss Federal Institute of Aquatic Science and Technology, CH-8600 Dübendorf, Switzerland
- ‡Institute of Biogeochemistry and Pollutant Dynamics (IBP), ETH Zürich, CH-8092 Zürich, Switzerland
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27
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Höyng D, Prommer H, Blum P, Grathwohl P, D'Affonseca FM. Evolution of carbon isotope signatures during reactive transport of hydrocarbons in heterogeneous aquifers. JOURNAL OF CONTAMINANT HYDROLOGY 2015; 174:10-27. [PMID: 25638275 DOI: 10.1016/j.jconhyd.2014.12.005] [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: 05/21/2014] [Revised: 12/22/2014] [Accepted: 12/30/2014] [Indexed: 06/04/2023]
Abstract
Compound-specific isotope analysis (CSIA) of organic pollutants has become a well-established tool for assessing the occurrence and extent of biodegradation processes in contaminated aquifers. However, the precision of CSIA is influenced by the degree to which assumptions underlying CSIA data interpretation hold under realistic field-scale conditions. For the first time this study demonstrates how aquifer analogs combined with reactive transport models offer an underexplored way to develop generic process understanding, evaluate monitoring and quantification strategies in highly heterogeneous subsurface settings. Data from high-resolution aquifer analogs were used in numerical experiments to track the propagation of a representative oxidizable organic compound (toluene) within a variety of realistic heterogeneous aquifers and to investigate its detailed fate. The simulations were used to analyze (1) the effects of physical aquifer heterogeneities on spatiotemporal patterns of contaminant concentrations and isotope signatures, (2) the performance of the commonly applied Rayleigh equation and (3) the applicability of an extension of the Rayleigh equation for complex hydrogeological conditions. The results indicate that if field-derived enrichment factors are applied without corrections for dilution, the conventional Rayleigh equation is inaccurate and estimates for biodegradation are typically overestimated and unreliable in heterogeneous aquifers. Underestimations can occur due to the partial source zone depletion. In contrast, if dilution can be accurately accounted for, field-derived enrichment factors comprise a suitable alternative to laboratory-derived and redox-specific enrichment factors. The study also examines to what extent variations in monitoring/sampling strategies influence the obtained results. Especially measurements from long-screened wells (>1 m) reveal to be inappropriate for the application of the Rayleigh equation in the investigated aquifer analogs, as low resolution data sampled from the simulated scenarios only enable a qualitative assessment of biodegradation. Measurements from both long- and short-screened wells employing the Rayleigh equation streamline approach are only partly viable for in situ biodegradation measurements in heterogeneous systems.
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Affiliation(s)
- Dominik Höyng
- University of Tübingen, Center for Applied Geoscience, Hölderlinstraße 12, 72074 Tübingen, Germany.
| | - Henning Prommer
- CSIRO Land and Water, Private Bag No. 5, Wembley, WA 6913, Australia; University of Western Australia, School of Earth and Environment, Crawley, Perth, WA 6009, Australia; National Centre for Groundwater Research and Training, Flinders University, Adelaide, GPO Box 2100, SA 5001, Australia
| | - Philipp Blum
- Karlsruhe Institute of Technology (KIT), Institute for Applied Geosciences (AGW), Kaiserstraße 12, 76131 Karlsruhe, Germany
| | - Peter Grathwohl
- University of Tübingen, Center for Applied Geoscience, Hölderlinstraße 12, 72074 Tübingen, Germany
| | - Fernando Mazo D'Affonseca
- University of Tübingen, Center for Applied Geoscience, Hölderlinstraße 12, 72074 Tübingen, Germany; TIMGEO GmbH, Hölderlinstraße 29, 72074 Tübingen, Germany
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28
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Lutz SR, Van Breukelen BM. Combined source apportionment and degradation quantification of organic pollutants with CSIA: 1. Model derivation. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2014; 48:6220-6228. [PMID: 24852716 DOI: 10.1021/es405400w] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Compound-specific stable isotope analysis (CSIA) serves as a tool for source apportionment (SA) and for the quantification of the extent of degradation (QED) of organic pollutants. However, simultaneous occurrence of mixing of sources and degradation is generally believed to hamper both SA and QED. On the basis of the linear stable isotope mixing model and the Rayleigh equation, we developed the stable isotope sources and sinks model, which allows for simultaneous SA and QED of a pollutant that is emitted by two sources and degrades via one transformation process. It was shown that the model necessitates at least dual-element CSIA for unequivocal SA in the presence of degradation-induced isotope fractionation, as illustrated for perchlorate in groundwater. The model also enables QED, provided degradation follows instantaneous mixing of two sources. If mixing occurs after two sources have degraded separately, the model can still provide a conservative estimate of the overall extent of degradation. The model can be extended to a larger number of sources and sinks as outlined. It may aid in forensics and natural attenuation assessment of soil, groundwater, surface water, or atmospheric pollution.
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Affiliation(s)
- S R Lutz
- Critical Zone Hydrology Group, Department of Earth Sciences, Faculty of Earth and Life Sciences, Vrije Universiteit Amsterdam , De Boelelaan 1085, 1081 HV Amsterdam, The Netherlands
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29
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Jin B, Rolle M, Li T, Haderlein SB. Diffusive fractionation of BTEX and chlorinated ethenes in aqueous solution: quantification of spatial isotope gradients. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2014; 48:6141-50. [PMID: 24811111 DOI: 10.1021/es4046956] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Laboratory experiments were performed to investigate and quantify the extent of diffusive isotope fractionation of organic contaminants in aqueous solution. We selected petroleum hydrocarbons (toluene and ethylbenzene, in 1:2 mixtures of labeled (perdeuterated) and nonlabeled isotopologues) and chlorinated solvents (trichloroethene, TCE, and cis-dichloroethene, cis-DCE, at their natural isotopic abundance) as model compounds. The experimental approach using gel diffusion tubes allowed us to resolve concentration and isotopic gradients induced by isotopologue-specific diffusion and to determine aqueous diffusion coefficients in agreement with the values calculated using published empirical correlations. The experimental results were quantitatively evaluated with numerical simulations to determine the aqueous diffusion coefficients, D, and the exponent of the inverse power-law relation between D and the molecular mass of the isotopologues. The results show remarkable diffusive isotope fractionation for all the investigated organic compounds; however, the extent of fractionation was found to be smaller for the chlorinated ethenes and remarkably deviating from an inverse square root relationship between the isotopologues diffusion coefficients and their molecular mass. The outcomes of this study are relevant for the interpretation of isotopic signatures of organic contaminants in environmental systems and for the quantitative application of compound specific isotope analysis (CSIA) that needs to take into account the fractionation effects of both physical and transformation processes.
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Affiliation(s)
- Biao Jin
- Center for Applied Geosciences, University of Tübingen , Hölderlinstrasse 12, D-72074 Tübingen, Germany
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30
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Liang X, Mundle SOC, Nelson JL, Passeport E, Chan CCH, Lacrampe-Couloume G, Zinder SH, Sherwood Lollar B. Distinct carbon isotope fractionation during anaerobic degradation of dichlorobenzene isomers. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2014; 48:4844-4851. [PMID: 24758692 DOI: 10.1021/es4054384] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Chlorinated benzenes are ubiquitous organic contaminants found in groundwater and soils. Compound specific isotope analysis (CSIA) has been increasingly used to assess natural attenuation of chlorinated contaminants, in which anaerobic reductive dechlorination plays an essential role. In this work, carbon isotope fractionation of the three dichlorobenzene (DCB) isomers was investigated during anaerobic reductive dehalogenation in methanogenic laboratory microcosms. Large isotope fractionation of 1,3-DCB and 1,4-DCB was observed while only a small isotope effect occurred for 1,2-DCB. Bulk enrichment factors (εbulk) were determined from a Rayleigh model: -0.8 ± 0.1 ‰ for 1,2-DCB, -5.4 ± 0.4 ‰ for 1,3-DCB, and -6.3 ± 0.2 ‰ for 1,4-DCB. εbulk values were converted to apparent kinetic isotope effects for carbon (AKIE) in order to characterize the carbon isotope effect at the reactive positions for the DCB isomers. AKIE values are 1.005 ± 0.001, 1.034 ± 0.003, and 1.039 ± 0.001 for 1,2-DCB, 1,3-DCB, and 1,4-DCB, respectively. The large difference in AKIE values between 1,2-DCB and 1,3-DCB (or 1,4-DCB) suggests distinct reaction pathways may be involved for different DCB isomers during microbial reductive dechlorination by the methanogenic cultures.
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Affiliation(s)
- Xiaoming Liang
- Department of Earth Sciences, University of Toronto , Toronto, Ontario M5S 3B1, Canada
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31
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Jin B, Rolle M. Mechanistic approach to multi-element isotope modeling of organic contaminant degradation. CHEMOSPHERE 2014; 95:131-139. [PMID: 24034890 DOI: 10.1016/j.chemosphere.2013.08.050] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2013] [Revised: 08/06/2013] [Accepted: 08/15/2013] [Indexed: 06/02/2023]
Abstract
We propose a multi-element isotope modeling approach to simultaneously predict the evolution of different isotopes during the transformation of organic contaminants. The isotopic trends of different elements are explicitly simulated by tracking position-specific isotopologues that contain the isotopes located at fractionating positions. Our approach is self-consistent and provides a mechanistic description of different degradation pathways that accounts for the influence of both primary and secondary isotope effects during contaminant degradation. The method is particularly suited to quantitatively describe the isotopic evolution of relatively large organic contaminant molecules. For such compounds, an integrated approach, simultaneously considering all possible isotopologues, would be impractical due to the large number of isotopologues. We apply the proposed modeling approach to the degradation of toluene, methyl tert-butyl ether (MTBE) and nitrobenzene observed in previous experimental studies. Our model successfully predicts the multi-element isotope data (both 2D and 3D), and accurately captures the distinct trends observed for different reaction pathways. The proposed approach provides an improved and mechanistic methodology to interpret multi-element isotope data and to predict the extent of multi-element isotope fractionation that goes beyond commonly applied modeling descriptions and simplified methods based on the ratio between bulk enrichment factors or on linear regression in dual-isotope plots.
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Affiliation(s)
- Biao Jin
- Center for Applied Geosciences, University of Tübingen, Sigwartstrasse 10, D-72076 Tübingen, Germany
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32
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Bashir S, Fischer A, Nijenhuis I, Richnow HH. Enantioselective carbon stable isotope fractionation of hexachlorocyclohexane during aerobic biodegradation by Sphingobium spp. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2013; 47:11432-11439. [PMID: 24007541 DOI: 10.1021/es402197s] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Carbon isotope fractionation was investigated for the biotransformation of γ- and α- hexachlorocyclohexane (HCH) as well as enantiomers of α-HCH using two aerobic bacterial strains: Sphingobium indicum strain B90A and Sphingobium japonicum strain UT26. Carbon isotope enrichment factors (ε(c)) for γ-HCH (ε(c) = -1.5 ± 0.1 ‰ and -1.7 ± 0.2 ‰) and α-HCH (ε(c) = -1.0 ± 0.2 ‰ and -1.6 ± 0.3 ‰) were similar for both aerobic strains, but lower in comparison with previously reported values for anaerobic γ- and α-HCH degradation. Isotope fractionation of α-HCH enantiomers was higher for (+) α-HCH (ε(c) = -2.4 ± 0.8 ‰ and -3.3 ± 0.8 ‰) in comparison to (-) α-HCH (ε(c) = -0.7 ± 0.2 ‰ and -1.0 ± 0.6 ‰). The microbial fractionation between the α-HCH enantiomers was quantified by the Rayleigh equation and enantiomeric fractionation factors (ε(e)) for S. indicum strain B90A and S. japonicum strain UT26 were -42 ± 16% and -22 ± 6%, respectively. The extent and range of isomer and enantiomeric carbon isotope fractionation of HCHs with Sphingobium spp. suggests that aerobic biodegradation of HCHs can be monitored in situ by compound-specific stable isotope analysis (CSIA) and enantiomer-specific isotope analysis (ESIA). In addition, enantiomeric fractionation has the potential as a complementary approach to CSIA and ESIA for assessing the biodegradation of α-HCH at contaminated field sites.
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Affiliation(s)
- Safdar Bashir
- Department of Isotope Biogeochemistry, Helmholtz Centre for Environmental Research - UFZ , Permoserstraße 15, 04318, Leipzig, Germany
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Jaekel U, Vogt C, Fischer A, Richnow HH, Musat F. Carbon and hydrogen stable isotope fractionation associated with the anaerobic degradation of propane and butane by marine sulfate-reducing bacteria. Environ Microbiol 2013; 16:130-40. [DOI: 10.1111/1462-2920.12251] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2013] [Revised: 07/30/2013] [Accepted: 08/12/2013] [Indexed: 10/26/2022]
Affiliation(s)
- Ulrike Jaekel
- Department of Microbiology; Max Planck Institute for Marine Microbiology; Bremen 28359 Germany
| | - Carsten Vogt
- Department of Isotope Biogeochemistry; Helmholtz Centre for Environmental Research -UFZ; Leipzig Germany
| | - Anko Fischer
- Department of Isotope Biogeochemistry; Helmholtz Centre for Environmental Research -UFZ; Leipzig Germany
- Isodetect GmbH; Leipzig Germany
| | - Hans-Hermann Richnow
- Department of Isotope Biogeochemistry; Helmholtz Centre for Environmental Research -UFZ; Leipzig Germany
| | - Florin Musat
- Department of Microbiology; Max Planck Institute for Marine Microbiology; Bremen 28359 Germany
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Kuder T, van Breukelen BM, Vanderford M, Philp P. 3D-CSIA: carbon, chlorine, and hydrogen isotope fractionation in transformation of TCE to ethene by a Dehalococcoides culture. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2013; 47:9668-9677. [PMID: 23895211 DOI: 10.1021/es400463p] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Carbon (C), chlorine (Cl), and hydrogen (H) isotope effects were determined during dechlorination of TCE to ethene by a mixed Dehalococcoides (Dhc) culture. The C isotope effects for the dechlorination steps were consistent with data published in the past for reductive dechlorination (RD) by Dhc. The Cl effects (combined with an inverse H effect in TCE) suggested that dechlorination proceeded through nucleophilic reactions with cobalamin rather than by an electron transfer mechanism. Depletions of (37)Cl in daughter compounds, resulting from fractionation at positions away from the dechlorination center (secondary isotope effects), further support the nucleophilic dechlorination mechanism. Determination of C and Cl isotope ratios of the reactants and products in the reductive dechlorination chain offers a potential tool for differentiation of Dhc activity from alternative transformation mechanisms (e.g., aerobic degradation and reductive dechlorination proceeding via outer sphere mechanisms), in studies of in situ attenuation of chlorinated ethenes. Hydrogenation of the reaction products (DCE, VC, and ethene) showed a major preference for the (1)H isotope. Detection of depleted dechlorination products could provide a line of evidence in discrimination between alternative sources of TCE (e.g., evolution from DNAPL sources or from conversion of PCE).
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Affiliation(s)
- Tomasz Kuder
- School of Geology and Geophysics, University of Oklahoma , 100 E. Boyd Street, SEC 710, Norman, Oklahoma 73019, United States
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35
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Mundle SOC, Vandersteen AA, Lacrampe-Couloume G, Kluger R, Sherwood Lollar B. Pressure-monitored headspace analysis combined with compound-specific isotope analysis to measure isotope fractionation in gas-producing reactions. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2013; 27:1778-1784. [PMID: 23821571 DOI: 10.1002/rcm.6625] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2013] [Revised: 05/08/2013] [Accepted: 05/09/2013] [Indexed: 06/02/2023]
Abstract
RATIONALE Processes that lead to pressure changes in closed experimental systems can dramatically increase the total uncertainty in enrichment factors (ε) based on headspace analysis and compound-specific isotope analysis (CSIA). We report: (1) A new technique to determine ε values for non-isobaric processes, and (2) a general approach to evaluate the experimental error in calculated ε values. METHODS ε values were determined by monitoring the change in headspace pressure from the production of CO2 in a decarboxylation reaction using a pressure gauge and measuring the δ(13) C values using CSIA. The statistical error was assessed over shorter reaction progress intervals to evaluate the impact of experimental error on the total uncertainty associated with calculated ε values. RESULTS As an alternative to conventional compositional analysis, calculation of CO2 produced during the reaction monitored with a pressure gauge resulted in rate constants and ε values with improved correlation coefficients and confidence intervals for a non-isobaric process in a closed system. Further, statistical evaluation of the ε values as a function of reaction progress showed that uncertainty in data points for reaction progress (f) at late stages of the reaction can have a significant impact on the reported ε value. CONCLUSIONS Pressure-monitored headspace analysis reduces the uncertainty associated with monitoring the reaction progress (f) based on estimating substrate removal and headspace dilution during sampling. Statistical calculations over shorter intervals should be used to evaluate the total error for reported ε values.
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Affiliation(s)
- Scott O C Mundle
- Department of Earth Sciences, University of Toronto, Toronto, Ontario, M5S 3B1, Canada
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36
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Eckert D, Qiu S, Elsner M, Cirpka OA. Model complexity needed for quantitative analysis of high resolution isotope and concentration data from a toluene-pulse experiment. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2013; 47:6900-7. [PMID: 23668814 DOI: 10.1021/es304879d] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Separating microbial- and physical-induced effects on the isotope signals of contaminants has been identified as a challenge in interpreting compound-specific isotope data. In contrast to simple analytical tools, such as the Rayleigh equation, reactive-transport models can account for complex interactions of different fractionating processes. The question arises how complex such models must be to reproduce the data while the model parameters remain identifiable. In this study, we reanalyze the high-resolution data set of toluene concentration and toluene-specific δ(13)C from the toluene-pulse experiment performed by Qiu et al. (this issue). We apply five reactive-transport models, differing in their degree of complexity. We uniquely quantify degradation and sorption properties of the system for each model, estimate the contributions of biodegradation-induced, sorption-induced, and transverse-dispersion-induced isotope fractionation to the overall isotope signal, and investigate the error introduced in the interpretation of the data when individual processes are neglected. Our results show that highly resolved data of both concentration and isotope ratios are needed for unique process identification facilitating reliable model calibration. Combined analysis of these highly resolved data demands reactive transport models accounting for nonlinear degradation kinetics and isotope fractionation by both reactive and physical processes such as sorption and transverse dispersion.
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Affiliation(s)
- Dominik Eckert
- Center for Applied Geoscience, University of Tübingen, Hölderlinstraße 12, D-72074 Tübingen, Germany
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Cretnik S, Thoreson KA, Bernstein A, Ebert K, Buchner D, Laskov C, Haderlein S, Shouakar-Stash O, Kliegman S, McNeill K, Elsner M. Reductive dechlorination of TCE by chemical model systems in comparison to dehalogenating bacteria: insights from dual element isotope analysis (13C/12C, 37Cl/35Cl). ENVIRONMENTAL SCIENCE & TECHNOLOGY 2013; 47:6855-6863. [PMID: 23627862 DOI: 10.1021/es400107n] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Chloroethenes like trichloroethene (TCE) are prevalent environmental contaminants, which may be degraded through reductive dechlorination. Chemical models such as cobalamine (vitamin B12) and its simplified analogue cobaloxime have served to mimic microbial reductive dechlorination. To test whether in vitro and in vivo mechanisms agree, we combined carbon and chlorine isotope measurements of TCE. Degradation-associated enrichment factors ε(carbon) and ε(chlorine) (i.e., molecular-average isotope effects) were -12.2‰ ± 0.5‰ and -3.6‰ ± 0.1‰ with Geobacter lovleyi strain SZ; -9.1‰ ± 0.6‰ and -2.7‰ ± 0.6‰ with Desulfitobacterium hafniense Y51; -16.1‰ ± 0.9‰ and -4.0‰ ± 0.2‰ with the enzymatic cofactor cobalamin; -21.3‰ ± 0.5‰ and -3.5‰ ± 0.1‰ with cobaloxime. Dual element isotope slopes m = Δδ(13)C/ Δδ(37)Cl ≈ ε(carbon)/ε(chlorine) of TCE showed strong agreement between biotransformations (3.4 to 3.8) and cobalamin (3.9), but differed markedly for cobaloxime (6.1). These results (i) suggest a similar biodegradation mechanism despite different microbial strains, (ii) indicate that transformation with isolated cobalamin resembles in vivo transformation and (iii) suggest a different mechanism with cobaloxime. This model reactant should therefore be used with caution. Our results demonstrate the power of two-dimensional isotope analyses to characterize and distinguish between reaction mechanisms in whole cell experiments and in vitro model systems.
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Affiliation(s)
- Stefan Cretnik
- Institute of Groundwater Ecology, Helmholtz Zentrum München, Ingolstädter Landstrasse 1, 85764 Neuherberg, Germany
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38
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Aeppli C, Bastviken D, Andersson P, Gustafsson O. Chlorine isotope effects and composition of naturally produced organochlorines from chloroperoxidases, flavin-dependent halogenases, and in forest soil. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2013; 47:6864-6871. [PMID: 23320408 DOI: 10.1021/es3037669] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The use of stable chlorine isotopic signatures (δ(37)Cl) of organochlorine compounds has been suggested as a tool to determine both their origins and transformations in the environment. Here we investigated the δ(37)Cl fractionation of two important pathways for enzymatic natural halogenation: chlorination by chloroperoxidase (CPO) and flavin-dependent halogenases (FDH). Phenolic products of CPO were highly (37)Cl depleted (δ(37)Cl = -12.6 ± 0.9‰); significantly more depleted than all known industrially produced organochlorine compounds (δ(37)Cl = -7 to +6‰). In contrast, four FDH products did not exhibit any observable isotopic shifts (δ(37)Cl = -0.3 ± 0.6‰). We attributed the different isotopic effect to the distinctly different chlorination mechanisms employed by the two enzymes. Furthermore, the δ(37)Cl in bulk organochlorines extracted from boreal forest soils were only slightly depleted in (37)Cl relative to inorganic Cl. In contrast to previous suggestions that CPO plays a key role in production of soil organochlorines, this observation points to the additional involvement of either other chlorination pathways, or that dechlorination of naturally produced organochlorines can neutralize δ(37)Cl shifts caused by CPO chlorination. Overall, this study demonstrates that chlorine isotopic signatures are highly useful to understand sources and cycling of organochlorines in nature. Furthermore, this study presents δ(37)Cl values of FDH products as well of bulk organochlorines extracted from pristine forest soil for the first time.
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Affiliation(s)
- Christoph Aeppli
- Department of Applied Environmental Science (ITM), Stockholm University, Sweden.
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39
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Wiegert C, Mandalakis M, Knowles T, Polymenakou PN, Aeppli C, Macháčková J, Holmstrand H, Evershed RP, Pancost RD, Gustafsson O. Carbon and chlorine isotope fractionation during microbial degradation of tetra- and trichloroethene. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2013; 47:6449-6456. [PMID: 23668287 DOI: 10.1021/es305236y] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Two-dimensional compound-specific isotope analysis (2D-CSIA), combining stable carbon and chlorine isotopes, holds potential for monitoring of natural attenuation of chlorinated ethenes (CEs) in contaminated soil and groundwater. However, interpretation of 2D-CSIA data sets is challenged by a shortage of experimental Cl isotope enrichment factors. Here, isotope enrichments factors for C and Cl (i.e., εC and εCl) were determined for biodegradation of tetrachloroethene (PCE) and trichloroethene (TCE) using microbial enrichment cultures from a heavily CE-contaminated aquifer. The obtained values were εC = -5.6 ± 0.7‰ (95% CI) and εCl = -2.0 ± 0.5‰ for PCE degradation and εC = -8.8 ± 0.2‰ and εCl = -3.5 ± 0.5‰ for TCE degradation. Combining the values for both εC and εCl yielded mechanism-diagnostic εCl/εC ratios of 0.35 ± 0.11 and 0.37 ± 0.11 for the degradation of PCE and TCE, respectively. Application of the obtained εC and εCl values to a previously investigated field site gave similar estimates for the fraction of degraded contaminant as in the previous study, but with a reduced uncertainty in assessment of the natural attenuation. Furthermore, 16S rRNA gene clone library analyses were performed on three samples from the PCE degradation experiments. A species closely related to Desulfitobacterium aromaticivorans UKTL dominated the reductive dechlorination process. This study contributes to the development of 2D-CSIA as a tool for evaluating remediation strategies of CEs at contaminated sites.
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Affiliation(s)
- Charline Wiegert
- Department of Applied Environmental Science, ITM, Stockholm University, 106 91 Stockholm, Sweden.
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40
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Jin B, Haderlein SB, Rolle M. Integrated carbon and chlorine isotope modeling: applications to chlorinated aliphatic hydrocarbons dechlorination. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2013; 47:1443-1451. [PMID: 23298341 DOI: 10.1021/es304053h] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We propose a self-consistent method to predict the evolution of carbon and chlorine isotope ratios during degradation of chlorinated hydrocarbons. The method treats explicitly the cleavage of isotopically different C-Cl bonds and thus considers, simultaneously, combined carbon-chlorine isotopologues. To illustrate the proposed modeling approach we focus on the reductive dehalogenation of chlorinated ethenes. We compare our method with the currently available approach, in which carbon and chlorine isotopologues are treated separately. The new approach provides an accurate description of dual-isotope effects regardless of the extent of the isotope fractionation and physical characteristics of the experimental system. We successfully applied the new approach to published experimental results on dehalogenation of chlorinated ethenes both in well-mixed systems and in situations where mass-transfer limitations control the overall rate of biodegradation. The advantages of our self-consistent dual isotope modeling approach proved to be most evident when isotope fractionation factors of carbon and chlorine differed significantly and for systems with mass-transfer limitations, where both physical and (bio)chemical transformation processes affect the observed isotopic values.
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Affiliation(s)
- Biao Jin
- Center for Applied Geosciences, University of Tübingen, Hölderlinstr. 12, D-72074 Tübingen, Germany
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41
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Aeppli C, Tysklind M, Holmstrand H, Gustafsson Ö. Use of Cl and C isotopic fractionation to identify degradation and sources of polychlorinated phenols: mechanistic study and field application. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2013; 47:790-797. [PMID: 23210465 DOI: 10.1021/es303343u] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The widespread use of chlorinated phenols (CPs) as a wood preservative has led to numerous contaminated sawmill sites. However, it remains challenging to assess the extent of in situ degradation of CPs. We evaluated the use of compound-specific chlorine and carbon isotope analysis (Cl- and C-CSIA) to assess CP biotransformation. In a laboratory system, we measured isotopic fractionation during oxidative 2,4,6-trichlorophenol dechlorination by representative soil enzymes (C. fumago chloroperoxidase, horseradish peroxidase, and laccase from T. versicolor). Using a mathematical model, the validity of the Rayleigh approach to evaluate apparent kinetic isotope effects (AKIE) was confirmed. A small but significant Cl-AKIE of 1.0022 ± 0.0006 was observed for all three enzymes, consistent with a reaction pathway via a cationic radical species. For carbon, a slight inverse isotope effect was observed (C-AKIE = 0.9945 ± 0.0019). This fractionation behavior is clearly distinguishable from reported reductive dechlorination mechanisms. Based on these results we then assessed degradation and apportioned different types of technical CP mixtures used at two former sawmill sites. To our knowledge, this is the first study that makes use of two-element CSIA to study sources and transformation of CPs in the environment.
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Affiliation(s)
- Christoph Aeppli
- Department of Applied Environmental Science (ITM), Stockholm University, SE-106 91 Stockholm, Sweden.
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42
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Thullner M, Fischer A, Richnow HH, Wick LY. Influence of mass transfer on stable isotope fractionation. Appl Microbiol Biotechnol 2012; 97:441-52. [PMID: 23143531 DOI: 10.1007/s00253-012-4537-7] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2012] [Revised: 10/19/2012] [Accepted: 10/22/2012] [Indexed: 11/27/2022]
Abstract
Biodegradation of contaminants is a common remediation strategy for subsurface environments. To monitor the success of such remediation means a quantitative assessment of biodegradation at the field scale is required. Nevertheless, the reliable quantification of the in situ biodegradation process it is still a major challenge. Compound-specific stable isotope analysis has become an established method for the qualitative analysis of biodegradation in the field and this method is also proposed for a quantitative analysis. However, to use stable isotope data to obtain quantitative information on in situ biodegradation requires among others knowledge on the influence of mass transfer processes on the observed stable isotope fractionation. This paper reviews recent findings on the influence of mass transfer processes on stable isotope fractionation and on the quantitative interpretation of isotope data. Focus will be given on small-scale mass transfer processes controlling the bioavailability of contaminants. Such bioavailability limitations are known to affect the biodegradation rate and have recently been shown to affect stable isotope fractionation, too. Theoretical as well as experimental studies addressing the link between bioavailability and stable isotope fractionation are reviewed and the implications for assessing biodegradation in the field are discussed.
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Affiliation(s)
- Martin Thullner
- Department of Environmental Microbiology, UFZ-Helmholtz Centre for Environmental Research, Permoserstr. 15, 30418 Leipzig, Germany.
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43
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Wiegert C, Aeppli C, Knowles T, Holmstrand H, Evershed R, Pancost RD, Macháčková J, Gustafsson Ö. Dual carbon-chlorine stable isotope investigation of sources and fate of chlorinated ethenes in contaminated groundwater. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2012; 46:10918-10925. [PMID: 22989309 DOI: 10.1021/es3016843] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Chlorinated ethenes (CEs) are ubiquitous groundwater contaminants, yet there remains a need for a method to efficiently monitor their in situ degradation. We report here the first field application of combined stable carbon and chlorine isotope analysis of tetrachloroethene (PCE) and trichloroethene (TCE) to investigate their biodegradation in a heavily contaminated aquifer. The two-dimensional Compound Specific Isotope Analysis (2D-CSIA) approach was facilitated by a recently developed gas chromatography-quadrupole mass spectrometry (GCqMS) method for δ(37)Cl determination. Both C and Cl isotopes showed evidence of ongoing PCE transformation. Applying published C isotope enrichment factors (ε(C)) enabled evaluation of the extent of in situ PCE degradation (11-78%). We interpreted C and Cl isotopes using a numerical reactive transport model along a 60-m flow path. It revealed that combined PCE and TCE mass load was dechlorinated by less than 10%, and that cis-dichloroethene was not further dechlorinated. Furthermore, the 2D-CSIA approach allowed estimation of Cl isotope enrichment factors ε(Cl) (-7.8 to -0.8‰) and characteristic ε(Cl)/ε(C) values (0.42-1.12) for reductive PCE dechlorination at this field site. This investigation demonstrates the benefit of 2D-CSIA to assess in situ degradation of CEs and the applicability of Cl isotope fractionation to evaluate PCE and TCE dechlorination.
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Affiliation(s)
- Charline Wiegert
- Department of Applied Environmental Science (ITM), Stockholm University, Svante Arrhenius väg 8c, SE-106 91 Stockholm, Sweden
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44
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Eckert D, Rolle M, Cirpka OA. Numerical simulation of isotope fractionation in steady-state bioreactive transport controlled by transverse mixing. JOURNAL OF CONTAMINANT HYDROLOGY 2012; 140-141:95-106. [PMID: 23017261 DOI: 10.1016/j.jconhyd.2012.08.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2012] [Revised: 08/09/2012] [Accepted: 08/10/2012] [Indexed: 05/12/2023]
Abstract
Compound-specific stable isotope analysis (CSIA) has increasingly been used as a tool to assess intrinsic biodegradation at contaminated field sites. Typically, the Rayleigh equation is used to estimate the extent of biodegradation from measured isotope ratios of the contaminant. However, if the rate-limiting step in overall degradation is not the microbial reaction itself, the Rayleigh equation may no more be applicable. In this study we simulate biodegradation of continuously emitted petroleum hydrocarbons in groundwater systems. These contaminants are effectively degraded at the plume fringe where transverse dispersion makes them mix with dissolved electron acceptors present in the ambient groundwater. We simulate reactive transport to study the coupled effects of transverse mixing and biodegradation on the spatial patterns of carbon isotope signatures and their interpretation based on depth-integrated sampling which represents the most common setup in the assessment of contaminated sites. We present scenarios mimicking a hydraulically uniform laboratory experiment and a field-scale application considering heterogeneous conductivity fields. We compare cases in which isotopologue-specific transverse dispersion is considered to those where this additional fractionation process is neglected. We show that these effects cause significant shifts in the isotopic signals and may lead to overestimation of biodegradation. Moreover, our results provide evidence that the rate-limiting effect of transverse mixing on the overall degradation spatially varies along the length of a steady-state contaminant plume. The control of biodegradation by transverse dispersion and the fractionating effect of dispersion modulate the fractionation caused by the microbial reaction alone. As a consequence, significantly nonlinear isotopic patterns are observed in a Rayleigh plot. Simulations in heterogeneous flow domains show that these effects persist at larger field scales and are sensitive to the degree of mixing enhancement, determined by the heterogeneity of the hydraulic conductivity fields, and to the groundwater flow velocity.
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Affiliation(s)
- Dominik Eckert
- University of Tübingen, Center for Applied Geoscience, Hölderlinstraße, 12, 72074 Tübingen, Germany
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45
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Van Breukelen BM, Rolle M. Transverse hydrodynamic dispersion effects on isotope signals in groundwater chlorinated solvents' plumes. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2012; 46:7700-8. [PMID: 22681629 DOI: 10.1021/es301058z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
The effects of transverse hydrodynamic dispersion on altering transformation-induced compound-specific isotope analysis (CSIA) signals within groundwater pollution plumes have been assessed with reactive transport modeling accommodating diffusion-induced isotope fractionation (DIF) and implementing different parameterizations of local transverse dispersion. The model reproduced previously published field data showing a negative carbon isotope pattern (-2 ‰) at the fringes of a nondegrading PCE plume. We extended the study to reactive transport scenarios considering vinyl chloride as a model compound and assessing, through a detailed sensitivity analysis, the coupled effects of transverse hydrodynamic dispersion (with and without DIF) and aerobic fringe degradation on the evolution of carbon and chloride isotope ratios. Transformation-induced positive isotope signals were increasingly attenuated with distance from the source and higher degradation rate. The effect of DIF on the overall isotope signal attenuation was greatest near the source and for low values of groundwater flow velocity, transverse dispersion coefficient, molecular weight, rate constant, and isotope fractionation factor, α, of the degradation reaction. Models disregarding DIF underestimate the actual α. The approximately twice larger DIF effect for chlorine than for carbon together with the low α for oxidation resulted in strong chlorine CSIA depletions for VC at the plume fringe.
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Affiliation(s)
- Boris M Van Breukelen
- Faculty of Earth and Life Sciences, VU University Amsterdam, De Boelelaan 1085, NL-1081 HV Amsterdam, The Netherlands.
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46
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Schmidt TC, Jochmann MA. Origin and fate of organic compounds in water: characterization by compound-specific stable isotope analysis. ANNUAL REVIEW OF ANALYTICAL CHEMISTRY (PALO ALTO, CALIF.) 2012; 5:133-155. [PMID: 22482787 DOI: 10.1146/annurev-anchem-062011-143143] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Within the past 15 years, compound-specific stable isotope analysis has continued to increase in popularity in the area of contaminant hydrology of organic molecules. In particular, in cases where concentration data alone are insufficient to elucidate environmental processes unequivocally, the isotope signature can provide additional unique information. Specifically, it can help answer questions about contaminant source apportionment, quantification of biotic and abiotic processes, and identification of transformation reactions on a mechanistic level. We review advances in laboratory and field investigations and exemplary applications in contaminant hydrology via stable isotope analysis. We also highlight future directions in the field.
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Affiliation(s)
- Torsten C Schmidt
- Instrumental Analytical Chemistry, University of Duisburg-Essen, 45141 Essen, Germany.
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47
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Hofstetter TB, Berg M. Assessing transformation processes of organic contaminants by compound-specific stable isotope analysis. Trends Analyt Chem 2011. [DOI: 10.1016/j.trac.2010.10.012] [Citation(s) in RCA: 111] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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48
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Elsner M. Stable isotope fractionation to investigate natural transformation mechanisms of organic contaminants: principles, prospects and limitations. ACTA ACUST UNITED AC 2010; 12:2005-31. [PMID: 21038038 DOI: 10.1039/c0em00277a] [Citation(s) in RCA: 238] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Gas chromatography-isotope ratio mass spectrometry (GC-IRMS) has made it possible to analyze natural stable isotope ratios (e.g., (13)C/(12)C, (15)N/(14)N, (2)H/(1)H) of individual organic contaminants in environmental samples. They may be used as fingerprints to infer contamination sources, and may demonstrate, and even quantify, the occurrence of natural contaminant transformation by the enrichment of heavy isotopes that arises from degradation-induced isotope fractionation. This review highlights an additional powerful feature of stable isotope fractionation: the study of environmental transformation mechanisms. Isotope effects reflect the energy difference of isotopologues (i.e., molecules carrying a light versus a heavy isotope in a particular molecular position) when moving from reactant to transition state. Measuring isotope fractionation, therefore, essentially allows a glimpse at transition states! It is shown how such position-specific isotope effects are "diluted out" in the compound average measured by GC-IRMS, and how a careful evaluation in mechanistic scenarios and by dual isotope plots can recover the underlying mechanistic information. The mathematical framework for multistep isotope fractionation in environmental transformations is reviewed. Case studies demonstrate how isotope fractionation changes in the presence of mass transfer, enzymatic commitment to catalysis, multiple chemical reaction steps or limited bioavailability, and how this gives information about the individual process steps. Finally, it is discussed how isotope ratios of individual products evolve in sequential or parallel transformations, and what mechanistic insight they contain. A concluding session gives an outlook on current developments, future research directions and the potential for bridging the gap between laboratory and real world systems.
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Affiliation(s)
- Martin Elsner
- Institute of Groundwater Ecology, Helmholtz Zentrum München - German Research Center for Environmental Health, Ingolstädter Landstr. 1, 85764, Neuherberg, Germany.
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Dong Y, Butler EC, Philp RP, Krumholz LR. Impacts of microbial community composition on isotope fractionation during reductive dechlorination of tetrachloroethylene. Biodegradation 2010; 22:431-44. [PMID: 20862525 DOI: 10.1007/s10532-010-9416-2] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2010] [Accepted: 09/07/2010] [Indexed: 11/24/2022]
Abstract
Isotope fractionation has been used with increasing frequency as a tool to quantify degradation of chlorinated aliphatic pollutants in the environment. The objective of this research was to determine if the electron donor present in enrichment cultures prepared from uncontaminated sediments influenced the extent of isotope fractionation of tetrachloroethylene (PCE), either directly, or through its influence on microbial community composition. Two PCE-degrading enrichment cultures were prepared from Duck Pond (DP) sediment and were incubated with formate (DPF) or H(2) (DPH) as electron donor. DPF and DPH were significantly different in both product distribution and extent of isotope fractionation. Chemical and isotope analyses indicated that electron donors did not directly affect the product distribution or the extent of isotope fractionation for PCE reductive dechlorination. Instead, restriction fragment length polymorphism (RFLP) and sequence analysis of the 16S rRNA clone libraries of DPF and DPH identified distinct microbial communities in each enrichment culture, suggesting that differences in microbial communities were responsible for distinct product distributions and isotope fractionation between the two cultures. A dominant species identified only in DPH was closely related to known dehalogenating species (Sulfurospirillum multivorans and Sulfurospirillum halorespirans) and may be responsible for PCE degradation in DPH. Our study suggests that different dechlorinators exist at the same site and can be preferentially stimulated by different electron donors, especially over the long-term (i.e., years), typical of in-situ ground water remediation.
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Affiliation(s)
- Yiran Dong
- Energy and Bioscience Institute, University of Illinois-Urbana Champaign, Urbana, IL 61801, USA
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Rolle M, Chiogna G, Bauer R, Griebler C, Grathwohl P. Isotopic fractionation by transverse dispersion: flow-through microcosms and reactive transport modeling study. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2010; 44:6167-73. [PMID: 20704214 DOI: 10.1021/es101179f] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Flow-through experiments were carried out to investigate the role of transverse dispersion on the isotopic behavior of an organic compound during conservative and bioreactive transport in a homogeneous porous medium. Ethylbenzene was selected as model contaminant and a mixture of labeled (perdeuterated) and light isotopologues was continuously injected in a quasi two-dimensional flow-through system. We observed a significant fractionation of ethylbenzene isotopologues during conservative transport at steady state. This effect was particularly pronounced at the plume fringe and contrasted with the common assumption that physical processes only provide a negligible contribution to isotope fractionation. Under the experimental steady state conditions, transverse hydrodynamic dispersion was the only process that could have caused the observed fractionation. Therefore, the measured isotope ratios at the outlet ports were interpreted with different parameterizations of the transverse dispersion coefficient. A nonlinear compound-specific parameterization showed the best agreement with the experimental data. Successively, bioreactive experiments were performed in two subsequent stages: a first oxic phase, involving a single strain of ethylbenzene degraders and a second phase with aerobic and anaerobic (i.e., ethylbenzene oxidation coupled to nitrate reduction) degradation. Significant fractionation through biodegradation occurred exclusively due to the metabolic activity of the anaerobic degraders. We performed analytical and numerical reactive transport simulations of the different experimental phases which confirmed that both the effects of physical processes (diffusion and dispersion) and microbially mediated reactions have to be considered to match the observed isotopic fractionation behavior.
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Affiliation(s)
- Massimo Rolle
- Center for Applied Geosciences, University of Tübingen, Sigwartstrasse 10, D-72076 Tübingen, Germany.
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