Laboratory of Hydrology and Geochemistry of Strasbourg (LHyGeS), UMR 7517, University of Strasbourg/ENGEES, CNRS, France; Génétique Moléculaire, Génomique, Microbiologie (GMGM), UMR 7156, University of Strasbourg, CNRS, France.
Laboratory of Hydrology and Geochemistry of Strasbourg (LHyGeS), UMR 7517, University of Strasbourg/ENGEES, CNRS, France.
Chemosphere. 2014 Mar;99:89-95. doi: 10.1016/j.chemosphere.2013.10.027. Epub 2013 Nov 18.
Compound-specific isotope analysis (CSIA) is a promising tool to study the environmental fate of a wide range of contaminants including pesticides. In this study, a novel CSIA method was developed to analyse the stable carbon isotope signatures of widely used chloroacetanilide herbicides. The developed method was applied in combination with herbicide concentration and hydrochemical analyses to investigate in situ biodegradation of metolachlor, acetochlor and alachlor during their transport in lab-scale wetlands. Two distinct redox zones were identified in the wetlands. Oxic conditions prevailed close to the inlet of the four wetlands (oxygen concentration of 212±24μM), and anoxic conditions (oxygen concentrations of 28±41μM) prevailed towards the outlet, where dissipation of herbicides mainly occurred. Removal of acetochlor and alachlor from inlet to outlet of wetlands was 56% and 51%, whereas metolachlor was more persistent (23% of load dissipation). CSIA of chloroacetanilides at the inlet and outlet of the wetlands revealed carbon isotope fractionation of alachlor (εbulk=-2.0±0.3‰) and acetochlor (εbulk=-3.4±0.5‰), indicating that biodegradation contributes to the dissipation of both herbicides. This study is a first step towards the application of CSIA to evaluate the transport and degradation of chloroacetanilide herbicides in the environment.
化合物特定同位素分析（CSIA）是研究包括农药在内的广泛污染物环境归宿的一种很有前途的工具。本研究开发了一种新的 CSIA 方法，用于分析广泛使用的氯乙酰胺类除草剂的稳定碳同位素特征。该方法与除草剂浓度和水化学分析相结合，用于研究氯甲草、乙草胺和甲草胺在实验室规模湿地中的运输过程中的原位生物降解情况。湿地中确定了两个明显的氧化还原区。四个湿地入口附近为好氧条件（氧浓度为 212±24μM），而出口处为缺氧条件（氧浓度为 28±41μM），除草剂的消解主要发生在缺氧条件下。从湿地入口到出口，乙草胺和甲草胺的去除率分别为 56%和 51%，而氯甲草的持久性更高（23%的负荷消解）。对湿地入口和出口处的氯乙酰胺类化合物进行 CSIA 分析，发现甲草胺（εbulk=-2.0±0.3‰）和乙草胺（εbulk=-3.4±0.5‰）存在碳同位素分馏，表明生物降解对这两种除草剂的消解都有贡献。本研究是将 CSIA 应用于评估氯乙酰胺类除草剂在环境中的迁移和降解的第一步。
