Redox动态变化下潜流带中氯乙酰胺类除草剂转化过程的碳氯同位素解析

The phenomenon of redox oscillation commonly occurs in hyporheic zone. Thus, a hypothesis is proposed that degradation of contaminants involves both biotic and abiotic multi-processes under redox oscillating environments. This study focuses on the scientific issue with respect to the identification and quantification of the multi-processes, and investigates transformation processes as well as carbon and chlorine isotope analysis of chloroacetanilide herbicides (acetochlor and butachlor) under redox oscillation in hyporheic zone on scales ranging from batch experiments, column experiments to contaminated field sites. The objectives of this study are to ascertain behavior of chloroacetanilide herbicides degraded by abiotic and biotic processes under different redox conditions, and especially to determine carbon and chlorine isotope enrichment factors for chloroacetanilide herbicides during typical degradation processes and elucidate the significance of isotope fractionation, and to reveal the mechanism of multi-processes contributing to degradation of chloroacetanilide herbicides under redox oscillating environments. This study will advance deeper understanding of the transformation of organic contaminants in surface and groundwater interactions, and provide scientific basis for prevention and restoration of organic contaminants.

本申请基于“潜流带存在Redox动态变化”的现象，提出“Redox动态变化引发生物-非生物多过程共同降解污染物”的科学假设。针对“有机污染物多种生物-非生物降解过程的解析”这一重要科学问题，以乙草胺和丁草胺作为目标污染物，结合碳氯同位素分析技术，从室内批实验、土柱实验、野外场地三个尺度开展Redox动态变化下潜流带中氯乙酰胺类除草剂的转化过程与碳氯同位素解析研究，探明不同氧化还原条件下生物-非生物作用对氯乙酰胺类除草剂的降解特性，重点确定氯乙酰胺类除草剂典型降解过程的碳氯同位素富集系数及其指示作用，揭示Redox动态变化下氯乙酰胺类除草剂多过程降解机制。本研究可以深化地表水-地下水相互作用中有机污染物迁移转化规律的认识，为有机污染的有效防控提供科学依据。

随着Redox动态变化，潜流带中的微生物群落和矿物组成等将发生相应变化，进而可能影响污染物的行为归趋。本研究表征了全国典型农业种植区潜流带还原沉积物再氧化过程的产羟基自由基能力、微生物群落结构等理化性质，在此基础上重点研究了沉积物对氯乙酰胺类除草剂的化学氧化降解和微生物降解特性及其主控因素，确定了羟基自由基氧化降解和微生物降解过程中氯乙酰胺类除草剂的同位素分馏效应及其指示意义。研究表明，潜流带沉积物产羟基自由基可在数小时的短时间尺度内快速降解氯乙酰胺类除草剂，而微生物需要在数十天以上的长时间尺度内才可能有效降解氯乙酰胺类除草剂。羟基自由基氧化降解和微生物降解过程中氯乙酰胺类除草剂的同位素分馏存在显著差异。本研究可以深化有机污染物在潜流带中的迁移转化规律的认识，为有机污染的有效防控提供科学依据。