Key Laboratory of Eco-Restoration of Regional Contaminated Environment, Shenyang University, Ministry of Education, Shenyang 110044, China.
China Coal Technology & Engineering Group Shenyang Engineering Company, Shenyang 110015, China.
Molecules. 2022 Apr 30;27(9):2874. doi: 10.3390/molecules27092874.
Compound specific isotope analysis (CSIA) and enantiomer specific isotope analysis (ESIA) are powerful tools for assessing the fate of hexachlorocyclohexanes (HCHs) in the environment. However, there is no systematic study on the CSIA and ESIA analysis test methods of the carbon isotopes of HCHs in water and soil environments, in particular the isotope fractionation in the pre-concentration process. We endeavored to test the compatibility of CSIA and ESIA with the liquid-liquid extraction method of HCHs in water. The results showed that there were negligible changes in the δC of HCHs after extraction, indicating that liquid-liquid extraction can be used as a pre-concentration method for the determination of δC of HCHs in water. The optimized method was validated and then applied to differentiate three HCHs from different manufacturers, to identify in situ degradation of HCHs of groundwater from a contaminated site and to resolve the carbon isotope fractionation occurring in the α-HCH oxidation by CaO/Fe(II) Fenton system. The results showed that the same reagents from different manufacturers have different carbon isotope compositions, and different isomers from the same manufacturer also have different isotope compositions, showing useful evidence in identifying the source of HCHs. The more enriched δC in the down-gradient wells indicated that HCHs have undergone biodegradation or/and chemical reactions in the groundwater system of the site. Carbon isotopic enrichment factors (ε) of -1.90 ± 0.10‱ were obtained in the oxidation process. Hence, the method validated in this study has great potential as a method for identifying the degradation of HCHs in a water environment.
化合物特定同位素分析 (CSIA) 和对映体特定同位素分析 (ESIA) 是评估六氯环己烷 (HCHs) 在环境中命运的有力工具。然而，对于水和土壤环境中 HCHs 的碳同位素 CSIA 和 ESIA 分析测试方法，特别是在预浓缩过程中的同位素分馏，尚无系统研究。我们努力测试 CSIA 和 ESIA 与水中 HCHs 的液液萃取方法的兼容性。结果表明，萃取后 HCHs 的 δC 几乎没有变化，表明液液萃取可以作为测定水中 HCHs δC 的预浓缩方法。优化后的方法得到了验证，然后用于区分来自不同制造商的三种 HCHs，识别受污染场地地下水的 HCHs 原位降解，并解决 CaO/Fe(II) Fenton 体系中 α-HCH 氧化过程中发生的碳同位素分馏。结果表明，不同制造商的相同试剂具有不同的碳同位素组成，同一制造商的不同异构体也具有不同的同位素组成，为识别 HCHs 的来源提供了有用的证据。在下向井中更富集的 δC 表明 HCHs 在该场地地下水系统中经历了生物降解或/和化学反应。在氧化过程中获得了碳同位素富集因子 (ε) 为-1.90±0.10‱。因此，本研究中验证的方法在识别水环境中 HCHs 的降解方面具有很大的潜力。
