Isotope fractionation approach to characterize the reactive transport processes governing the fate of hexachlorocyclohexanes at a contaminated site in India

Wu, Langping; Liu, Yaqing; Xiao, Ling; Bajaj, Abhay; Sharma, Monika; Lal, Rup; Richnow, Hans H.

doi:10.1016/j.envint.2019.105036

Cited by 38 publications

(32 citation statements)

References 37 publications

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“…The reactions were stopped at different time intervals and the remaining γ-HCH was extracted for concentration and stable carbon, hydrogen and chlorine isotope analysis. The analytical methods have been described in detail elsewhere [9,10] and basic information is provided in Supplementary Materials.…”

Section: Methodsmentioning

confidence: 99%

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Can Alkaline Hydrolysis of γ-HCH Serve as a Model Reaction to Study Its Aerobic Enzymatic Dehydrochlorination by LinA?

Kannath

Adamczyk

et al. 2019

IJMS

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Hexachlorocyclohexane (HCH) isomers constitute a group of persistent organic pollutants. Their mass production and treatment have led to a global environmental problem that continues to this day. The characterization of modes of degradation of HCH by isotope fractionation is a current challenge. Multi isotope fractionation analysis provides a concept to characterize the nature of enzymatic and chemical transformation reactions. The understanding of the kinetic isotope effects (KIE) on bond cleavage reaction contributes to analyses of the mechanism of chemical and enzymatic reactions. Herein, carbon, chlorine, and hydrogen kinetic isotope effects are measured and predicted for the dehydrochlorination reaction of γ-HCH promoted by the hydroxyl ion in aqueous solution. Quantum mechanical (QM) microsolvation with an implicit solvation model and path integral formalism in combination with free-energy perturbation and umbrella sampling (PI-FEP/UM) and quantum mechanical/molecular mechanical QM/MM potentials for including solvent effects as well as calculating isotope effects are used and analyzed with respect to their performance in reproducing measured values. Reaction characterization is discussed based on the magnitudes of obtained isotope effects. The comparative analysis between the chemical dehydrochlorination of γ-HCH in aqueous media and catalyzed reaction by dehydrochlorinase, LinA is presented and discussed. Based on the values of isotope effects, these two processes seem to occur via the same net mechanism.

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Section: Methodsmentioning

confidence: 99%

“…According to estimates 1.7–4.8 million tons of HCH are still present widely in nature [6]. Isotope fractionation concepts have been used to elucidate transformation reactions of HCH in field studies [7,8] and diagnostically to characterize transformation reactions even in food webs [9,10].…”

Section: Introductionmentioning

confidence: 99%

Can Alkaline Hydrolysis of γ-HCH Serve as a Model Reaction to Study Its Aerobic Enzymatic Dehydrochlorination by LinA?

Kannath

Adamczyk

et al. 2019

IJMS

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“…The relationship between these AKIE concepts and chemical reactions, such as decomposition, can be directly applied to plants that can be used as prime targets for pesticides. In a recent study on hexachlorocyclohexane (HCH, lindane), the increasing δ 13 C signature of HCH combined with the enantiomeric fraction (EF) value of α-HCH (an index of preferential degradation of α-HCH) could explain the degradation process of these compounds in the rhizosphere of plants, although the results still have limitations in determining the contribution of biodegradation in the rhizosphere and within plants (soil–plant system) [ 110 ]. Concepts related to the quantification of the decomposition of pollutants have been discussed using the ‘Rayleigh equation’ approach, that informs the change in the isotopic enrichment of the degraded substrate and allows the calculation of the isotopic composition of the product, since the 2000s [ 104 ].…”

Section: Applications Of Csia For Monitor Pesticide Pollution In Environments and Agricultural Productsmentioning

confidence: 99%

“…Recently, multi-isotope analysis (C, H, N, and Cl) in pesticides has been developed to competitively investigate the source and transformation routes in the environment [ 110 ]. Several studies have suggested that considering more than one (e.g., C, N, Cl) isotope variable clearly improves the discrimination power of a pesticide derived from different suppliers [ 35 , 128 , 133 ].…”

Section: Applications Of Csia For Monitor Pesticide Pollution In Environments and Agricultural Productsmentioning

confidence: 99%

Application of Compound-Specific Isotope Analysis in Environmental Forensic and Strategic Management Avenue for Pesticide Residues

et al. 2021

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Unintended pesticide pollution in soil, crops, and adjacent environments has caused several issues for both pesticide users and consumers. For users, pesticides utilized should provide higher yield and lower persistence while considering both the environment and agricultural products. Most people are concerned that agricultural products expose humans to pesticides accumulating in vegetation. Thus, many countries have guidelines for assessing and managing pesticide pollution, for farming in diverse environments, as all life forms in soil are untargeted to these pesticides. The stable isotope approach has been a useful technique to find the source of organic matter in studies relating to aquatic ecology and environmental sciences since the 1980s. In this study, we discuss commonly used analytical methods using liquid and gas chromatography coupled with isotopic ratio mass spectrometry, as well as the advanced compound-specific isotope analysis (CSIA). CSIA applications are discussed for tracing organic pollutants and understanding chemical reactions (mechanisms) in natural environments. It shows great applicability for the issues on unintended pesticide pollution in several environments with the progress history of isotope application in agricultural and environmental studies. We also suggest future study directions based on the forensic applications of stable isotope analysis to trace pesticides in the environment and crops.

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“…Compound‐specific isotope analysis (CSIA) is a powerful tool for source identification and process characterization involving such persistent organic pollutants as hexachlorocyclohexanes, polychlorinated biphenyls and PBDEs . Prior studies showed that organic compounds having lighter carbon isotopes (i.e.…”

Section: Introductionmentioning

confidence: 99%

Compound‐specific carbon isotope analysis for mechanistic characterization of debromination of decabrominated diphenyl ether

Zhu

Zhong

et al. 2020

Rapid Comm Mass Spectrometry

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Rationale: Decabrominated diphenyl ether (BDE-209) is a notorious persistent organic pollutant widely found in the environment. Developing a compound-specific isotope analysis (CSIA) method is much needed in order to trace its transport and degradation processes and to evaluate the effectiveness of the remediation of BDE-209 in the environment. However, the conventional CSIA method, i.e. gas chromatography (GC) combustion isotope ratio mass spectrometry, is not appropriate for BDE-209 because of its high thermal instability and incomplete combustion. Methods:We developed a high-performance liquid chromatography (HPLC) method for the separation and purification of BDE-209 that prevents its thermal reactivity as occurred in prior GC-based methods. The δ 13 C value of the purified BDE-209 was determined using offline elemental analyzer isotope ratio mass spectrometry (EA/IRMS). This two-step method was applied to determine the δ 13 C values of BDE-209 in two commercial samples and to characterize carbon isotope fractionation associated with the debromination of BDE-209 via nanoscale zero-valent iron. Results: The mean values of daily δ 13 C analyses of six replicates of a BDE-209 standard varied from −27.66‰ to −27.92‰, with a standard deviation ranging from 0.07‰ to 0.16‰, indicating a good reproducibility of EA/IRMS. The EA/IRMS analysis of the purified BDE-209 standard indicated no obvious isotope fractionation during the sample purification. The impurity content in commercial BDE-209 samples may contribute additional variation of the δ 13 C values of BDE-209. The δ 13 C values of BDE-209 gradually changed from −27.47 ± 0.37‰ to −24.59 ± 0.19‰ when 74% of the BDE-209 standard was degraded within 36 h. The estimated carbon isotope enrichment factor was −1.72 ± 0.18‰. Conclusions:The two-step method based on HPLC and EA/IRMS avoids the thermal instability of BDE-209 in the traditional CSIA method. It offers a novel approach for elucidating the degradation mechanisms of BDE-209 in the environment and for source identification in contaminated sites.

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Isotope fractionation approach to characterize the reactive transport processes governing the fate of hexachlorocyclohexanes at a contaminated site in India

Cited by 38 publications

References 37 publications

Can Alkaline Hydrolysis of γ-HCH Serve as a Model Reaction to Study Its Aerobic Enzymatic Dehydrochlorination by LinA?

Can Alkaline Hydrolysis of γ-HCH Serve as a Model Reaction to Study Its Aerobic Enzymatic Dehydrochlorination by LinA?

Application of Compound-Specific Isotope Analysis in Environmental Forensic and Strategic Management Avenue for Pesticide Residues

Compound‐specific carbon isotope analysis for mechanistic characterization of debromination of decabrominated diphenyl ether

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