Grup MAiMA, SGR Mineralogia Aplicada, Geoquímica i Hidrogeologia (MAGH), Departament de Mineralogia, Petrologia i Geologia Aplicada, Facultat de Ciències de la Terra, Institut de Recerca de l'Aigua (IdRA), Universitat de Barcelona (UB), Martí i Franquès s/n, 08028 Barcelona, Spain.
Department of Technical Biogeochemistry, Helmholtz Centre for Environmental Research - UFZ, Permoserstraße 15, Leipzig 04318, Germany.
J Hazard Mater. 2024 Dec 5;480:135929. doi: 10.1016/j.jhazmat.2024.135929. Epub 2024 Sep 20.
This study investigates the use of multi-element compound-specific isotope analysis (ME-CSIA) to monitor degradation processes of methoxychlor, a persistent organochlorine insecticide. Laboratory experiments examined the kinetics, release of transformation products, and carbon and chlorine isotope effects during methoxychlor degradation through alkaline hydrolysis, oxidation with alkaline-activated persulfate, and biotic reductive dechlorination. Results showed that hydrolysis and oxidation did not cause significant carbon and chlorine isotope fractionation, indicating that C-H rather than C-Cl bond cleavage was the rate-determining step. Conversely, biotic reductive dechlorination by a field-derived microcosm under strictly anoxic conditions displayed significant carbon (ε = -0.9 ± 0.3 ‰) and chlorine (ε = -1.9 ± 1.0 ‰) isotope fractionation. Its corresponding calculated dual isotope slope (Λ = 0.4 ± 0.1) and apparent kinetic isotope effects (AKIE = 1.014 ± 0.005 and AKIE = 1.006 ± 0.003) indicate a C-Cl bond cleavage as the rate-determining step, highlighting the difference with respect to the other studied degradation mechanisms. Changes in the microbial community diversity revealed that families such as Dojkabacteria, Anaerolineaceae, Dysgonomonadaceae, Bacteroidetes vadinHA17, Pseudomonadaceae, and Spirochaetaceae, may be potential agents of methoxychlor reductive dechlorination under anoxic conditions. This study advances the understanding of degradation mechanisms of methoxychlor and improves the ability to track its transformation in contaminated environments, including for the first time an isotopic perspective.
本研究采用多元素化合物特异性同位素分析（ME-CSIA）来监测甲氧氯这种持久性有机氯杀虫剂的降解过程。实验室实验通过碱性水解、碱性过硫酸盐氧化和生物还原脱氯，考察了甲氧氯降解过程中的动力学、转化产物的释放以及碳和氯同位素效应。结果表明，水解和氧化不会导致显著的碳和氯同位素分馏，表明 C-H 键而不是 C-Cl 键的断裂是速率决定步骤。相反，在严格缺氧条件下，由一个现场衍生的微宇宙进行的生物还原脱氯显示出显著的碳（ε=-0.9±0.3‰）和氯（ε=-1.9±1.0‰）同位素分馏。其相应的计算双同位素斜率（Λ=0.4±0.1）和表观动力学同位素效应（AKIE=1.014±0.005 和 AKIE=1.006±0.003）表明 C-Cl 键的断裂是速率决定步骤，这与其他研究的降解机制有显著差异。微生物群落多样性的变化表明，Dojkabacteria、Anaerolineaceae、Dysgonomonadaceae、Bacteroidetes vadinHA17、Pseudomonadaceae 和 Spirochaetaceae 等家族可能是缺氧条件下甲氧氯还原脱氯的潜在作用因子。本研究增进了对甲氧氯降解机制的理解，提高了在污染环境中追踪其转化的能力，包括首次从同位素角度进行研究。
