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首页> 外文期刊>Environmental Science & Technology >Carbon and Chlorine Isotope Effects During Abiotic Reductive Dechlorination of Polychlorinated Ethanes
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Carbon and Chlorine Isotope Effects During Abiotic Reductive Dechlorination of Polychlorinated Ethanes

机译：多氯乙烷的非生物还原脱氯过程中的碳和氯同位素效应

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摘要

We investigated the extent and variability of C and Cl isotope fractionation during the reduction of polychlorinated ethanes to evaluate the potential use of Cl isotope analysis for the assessment of contaminant transformation in subsurface environments. Kinetic isotope effects.(KIE) for C and Cl for the reductive β-elimination of 1,1,2,2-tetrachloroethane (1,1,2,2-TeCA), pentachloroethane (PCA), and hexachloroethane by Cr(II) used as model reductant in homogeneous solution were compared to KIEs measured for dehydrochlorination of 1,1,2,2-TeCA and PCA. Since isotopic reactions of polychlorinated compounds are complicated by the simultaneous presence of several Cl isotopologues and intramolecular isotopic competition, we present a procedure for the determination of KIEs for Cl from the initial reactant and final product Cl isotope ratios. Despite different reaction mechanisms, that is reduction via dissociative inner-sphere electron transfer by Cr(H_2O)_6~(2+) and base-catalyzed, concerted elimination, respectively, apparent KIEs for C of both pathways fall within a similar range (1.021-1.031). In contrast, KIEs for Cl are significantly higher for reductive β-elimination (1.013-1.021) than for dehydrochlorination (1.000-1.006). These results suggest that reductive transformations of polychlorinated contaminants might be identified on the basis of combined C and Cl isotope analysis.
机译：我们研究了多氯乙烷还原过程中C和Cl同位素分馏的程度和变异性，以评估Cl同位素分析在评估地下环境中污染物转化中的潜在用途。 C和Cl的动力学同位素效应（KIE），用于通过Cr（II）还原性地消除1,1,2,2-四氯乙烷（1,1,2,2-TeCA），五氯乙烷（PCA）和六氯乙烷的β-消除将在均相溶液中用作模型还原剂的）与测量1,1,2,2-TeCA和PCA脱氯化氢的KIE进行比较。由于多氯化合物的同位素反应同时存在几个氯同位素和分子内同位素竞争而使多氯化合物的同位素反应复杂化，因此我们提出了一种从初始反应物和最终产物氯同位素比值确定氯的KIE的方法。尽管有不同的反应机理，即通过Cr（H_2O）_6〜（2+）的解离内球电子转移和碱催化的协同消除所导致的还原，两条途径的C的表观KIE均在相似的范围内（1.021） -1.031）。相反，还原性β-消除（1.013-1.021）的Cl的KIEs明显高于脱氯化氢（1.000-1.006）的KIE。这些结果表明，可以根据结合的C和Cl同位素分析确定多氯污染物的还原转化。

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