Stable carbon isotope analysis to distinguish biotic and abiotic degradation of 1,1,1-trichloroethane in groundwater sediments

Broholm, Mette Martina; Hunkeler, Daniel; Tuxen, Nina; Jeannottat, Simon; Scheutz, Charlotte

doi:10.1016/j.chemosphere.2014.01.051

Cited by 17 publications

(10 citation statements)

References 31 publications

(60 reference statements)

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“…A chain of redox reactions influenced by the additional presence of pyrite in the aquifer eventually affected the degradation of chlorinated ethenes, which led primarily to an increase of biotic PCE and TCE degradation to cDCE immediately downgradient of the source area and predominantly to an abiotic reduction of cDCE in the plume centre. Intricate situations similar to that of the current study, where iron plays a role in redox reactions and both bacterial and abiotic degradation of chlorinated contaminants occur, have been previously reported (Elsner et al, 2004;Shani et al, 2013;Broholm et al, 2014). This underlines the need for studies that explore the dynamics of geochemical systems where iron is present.…”

Section: Assessment Of Source Thermal Remediation Effect On Redox Consupporting

confidence: 84%

Identification of abiotic and biotic reductive dechlorination in a chlorinated ethene plume after thermal source remediation by means of isotopic and molecular biology tools

Badin

Broholm

Jacobsen

et al. 2016

Journal of Contaminant Hydrology

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Section: Assessment Of Source Thermal Remediation Effect On Redox Consupporting

confidence: 84%

Identification of abiotic and biotic reductive dechlorination in a chlorinated ethene plume after thermal source remediation by means of isotopic and molecular biology tools

Badin

Broholm

Jacobsen

et al. 2016

Journal of Contaminant Hydrology

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“…This technique can therefore be used to differentiate between degradation mechanisms if isotope fractionation signatures are significantly different. CSIA has been used to differentiate between biotic and abiotic degradation of chlorinated ethanes in groundwater sediments and biotic and abiotic contribution of trichloroethylene degradation in a reactive iron barrier . There have been several studies documenting carbon isotope fractionation in chlorinated ethanes and ethenes via reaction with Fe 0 . − However, there is no analogous data published for chlorinated methanes, and in general, there is a lack of fractionation data for these compounds.…”

Section: Introductionmentioning

confidence: 99%

Relative Contributions of Dehalobacter and Zerovalent Iron in the Degradation of Chlorinated Methanes

Lee

Wells

Wong

et al. 2015

Environ. Sci. Technol.

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The role of bacteria and zerovalent iron (Fe(0)) in the degradation of chlorinated solvents in subsurface environments is of interest to researchers and remediation practitioners alike. Fe(0) used in reactive iron barriers for groundwater remediation positively interacted with enrichment cultures containing Dehalobacter strains in the transformation of halogenated methanes. Chloroform transformation and dichloromethane formation was up to 8-fold faster and 14 times higher, respectively, when a Dehalobacter-containing enrichment culture was combined with Fe(0) compared with Fe(0) alone. The dichloromethane-fermenting culture transformed dichloromethane up to three times faster with Fe(0) compared to without. Compound-specific isotope analysis was employed to compare abiotic and biotic chloroform and dichloromethane degradation. The isotope enrichment factor for the abiotic chloroform/Fe(0) reaction was large at -29.4 ± 2.1‰, while that for chloroform respiration by Dehalobacter was minimal at -4.3 ± 0.45‰. The combined abiotic/biotic dechlorination was -8.3 ± 0.7‰, confirming the predominance of biotic dechlorination. The enrichment factor for dichloromethane fermentation was -15.5 ± 1.5‰; however, in the presence of Fe(0) the factor increased to -23.5 ± 2.1‰, suggesting multiple mechanisms were contributing to dichloromethane degradation. Together the results show that chlorinated methane-metabolizing organisms introduced into reactive iron barriers can have a significant impact on trichloromethane and dichloromethane degradation and that compound-specific isotope analysis can be employed to distinguish between the biotic and abiotic reactions involved.

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“…However, according to the results from previous reaction studies, − the second mechanistic scenario seems more likely. In anoxic conditions, 1,1,1-TCA can also undergo metal-catalyzed reduction by natural reductants such as iron sulfides. , Transformation of 1,1,1-TCA by zero-valent metals and bimetallic reductants has been investigated to evaluate their potential application to in situ treatment techniques such as nanoparticles injection or permeable reactive barriers. − For 1,1,1-TCA reductive dechlorination by zero-valent iron, cleavage of a C–Cl bond by dissociative single electron transfer (SET) and formation of 1,1-dichoroethyl radical intermediate has been proposed as the first reaction step (Scheme b), leading to the production of 1,1-dichloroethane (1,1-DCA, via hydrogenolysis), ethene/ethane (α-elimination) and C 4 compounds (coupling). , Furthermore, recently, 1,1,1-TCA degradation by activated persulfate (PS) using different methods such as base and heat − activation was demonstrated. Thermal decomposition of PS generates reactive oxygen species and, for reaction with 1,1,1-TCA, transformation via H abstraction has been postulated (Scheme c).…”

Section: Introductionmentioning

confidence: 99%

“…Due to the susceptibility of 1,1,1-TCA to abiotic transformations, two of the three pathways investigated in this study (Scheme ) may occur simultaneously in the aquifer. In anoxic conditions, reduction of 1,1,1-TCA by natural reductants or engineered Fe(0) systems can occur in addition to HY/DH. On the other hand, the rate of HY/DH will increase significantly during treatment of 1,1,1-TCA by heat-activated PS due to the raise of water temperature .…”

Section: Introductionmentioning

confidence: 99%

Carbon and Chlorine Isotope Analysis to Identify Abiotic Degradation Pathways of 1,1,1-Trichloroethane

Palau

Shouakar-Stash

Hunkeler

2014

Environ. Sci. Technol.

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This study investigates dual C−Cl isotope fractionation during 1,1,1-TCA transformation by heat-activated persulfate (PS), hydrolysis/dehydrohalogenation (HY/DH) and Fe(0). Compound-specific chlorine isotope analysis of 1,1,1-TCA was performed for the first time, and transformation-associated isotope fractionation ε bulk C and ε bulk Cl values were −4.0 ± 0.2‰ and no chlorine isotope fractionation with PS, −1.6 ± 0.2‰ and −4.7 ± 0.1‰ for HY/DH, −7.8 ± 0.4‰ and −5.2 ± 0.2‰ with Fe(0). Distinctly different dual isotope slopes (Δδ 13 C/Δδ 37 Cl): ∞ with PS, 0.33 ± 0.04 for HY/DH and 1.5 ± 0.1 with Fe(0) highlight the potential of this approach to identify abiotic degradation pathways of 1,1,1-TCA in the field. The trend observed with PS agreed with a C−H bond oxidation mechanism in the first reaction step. For HY/DH and Fe(0) pathways, different slopes were obtained although both pathways involve cleavage of a C−Cl bond in their initial reaction step. In contrast to the expected larger primary carbon isotope effects relative to chlorine for C−Cl bond cleavage, ε bulk C < ε bulk Cl was observed for HY/DH and in a similar range for reduction by Fe(0), suggesting the contribution of secondary chlorine isotope effects. Therefore, different magnitude of secondary chlorine isotope effects could at least be partly responsible for the distinct slopes between HY/DH and Fe(0) pathways. Following this dual isotope approach, abiotic transformation processes can unambiguously be identified and quantified.

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Stable carbon isotope analysis to distinguish biotic and abiotic degradation of 1,1,1-trichloroethane in groundwater sediments

Cited by 17 publications

References 31 publications

Identification of abiotic and biotic reductive dechlorination in a chlorinated ethene plume after thermal source remediation by means of isotopic and molecular biology tools

Identification of abiotic and biotic reductive dechlorination in a chlorinated ethene plume after thermal source remediation by means of isotopic and molecular biology tools

Relative Contributions of Dehalobacter and Zerovalent Iron in the Degradation of Chlorinated Methanes

Carbon and Chlorine Isotope Analysis to Identify Abiotic Degradation Pathways of 1,1,1-Trichloroethane

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