Abe Y, Aravena R, Zopfi J, Shouakar-Stash O, Cox E, Roberts J D, Hunkeler D
Centre for Hydrogeology, University of Neuchâtel, Rue Emile Argand 11, CH-2009 Neuchâtel, Switzerland.
Environ Sci Technol. 2009 Jan 1;43(1):101-7. doi: 10.1021/es801759k.
The study investigated carbon and chlorine isotope fractionation during aerobic oxidation and reductive dechlorination of vinyl chloride (VC) and cis-1,2-dichloroethene (cDCE). The experimental data followed a Rayleigh trend. For aerobic oxidation, the average carbon isotope enrichment factors were -7.2 per thousand and -8.5% for VC and cDCE, respectively, while average chlorine isotope enrichment factors were only -0.3 per thousand for both compounds. These values are consistent with an initial transformation by epoxidation for which a significant primary carbon isotope effect and only a small secondary chlorine isotope effect is expected. For reductive dechlorination, larger carbon isotope enrichment factors of -25.2 per thousand for VC and -18.5 per thousand for cDCE were observed consistent with previous studies. Although the average chlorine isotope enrichmentfactors were larger than those of aerobic oxidation (-1.8 per thousand for VC, -1.5 per thousand for cDCE), they were not as large as typically expected for a primary chlorine isotope effect suggesting that no cleavage of C-Cl bonds takes place during the initial rate-limiting step. The ratio of isotope enrichment factors for chlorine and carbon were substantially different for the two reaction mechanisms suggesting that the reaction mechanisms can be differentiated at the field scale using a dual isotope approach.
该研究调查了氯乙烯（VC）和顺式1,2 - 二氯乙烯（cDCE）在好氧氧化和还原脱氯过程中的碳和氯同位素分馏情况。实验数据呈现瑞利趋势。对于好氧氧化，VC和cDCE的平均碳同位素富集因子分别为-7.2‰和-8.5‰，而两种化合物的平均氯同位素富集因子仅为-0.3‰。这些值与通过环氧化的初始转化一致，对于这种转化，预计会有显著的一级碳同位素效应，而二级氯同位素效应较小。对于还原脱氯，观察到VC的碳同位素富集因子较大，为-25.2‰，cDCE为-18.5‰，这与先前的研究一致。尽管平均氯同位素富集因子大于好氧氧化时的（VC为-1.8‰，cDCE为-1.5‰），但它们不像一级氯同位素效应通常预期的那么大，这表明在初始限速步骤中没有发生C-Cl键的断裂。两种反应机制的氯和碳同位素富集因子之比有很大差异，这表明可以在现场尺度上使用双同位素方法区分反应机制。
