过硫酸盐活化体系中共存在的氧化/还原自由基对地下水氯代烃的降解贡献度及机制研究

我们前期调查和实验结果充分提示：氯代烃是地下水最主要和严重的污染物，过硫酸盐活化技术对其治理有效可行，且证实活化体系中产生的氧化自由基（SO4-.、OH.）/还原自由基（O2-.）对氯代烃降解起关键性作用。但从氧化/还原自由基角度阐明氯代烃降解机制及地下水质和土壤中矿物质对自由基强度影响等系列问题尚不清。本研究首次在四种过硫酸盐活化体系中（热、过渡金属Fe、碱、过氧化氢），拟通过自由基探针和电子顺磁共振检测，证实氧化/还原自由基共存在；以最常见的三氯乙烯和1,1,1-三氯乙烷为目标污染物，在水相和水-氯代烃自由相中构建氧化/还原反应体系，用GC/MS产物分析、Cl-释放率及Gaussian 09软件模拟等多元化手段，阐明氯代烃降解机制；从自由基清扫剂实验及自由基强度变化两方面，研究自由基对氯代烃降解贡献度，及地下水质和矿物质对氯代烃降解效果影响，为实际氯代烃污染地下水修复治理提供理论依据。

Our previous investigation and preliminary experiments clearly indicated that chlorinated hydrocarbon (CHC) is the most and serious contaminants in groundwater. The remediation of contaminated groundwater by activated persulfate technique is effective and feasible, in which it is confirmed that the generated oxidative/reductive free radicals (SO4?o, OHo and O2?o) in systems are playing a key role in CHC degradation. However, many questions related to the CHC degradation mechanism from the point of view of oxidative/reductive free radicals, and the effects of groundwater characteristics and minerals in soil on generated radicals strength are still unclear. This project will confirm for the first time the co-existence of oxidative/reductive free radicals in four activated persulfate systems (heat, transition metal Fe, base and H2O2) by radical probes and EPR methods. The CHC oxidative/reductive degradation mechanisms (choosing TCE and 1,1,1-TCA as the target contaminants) will be elucidated through GC/MS intermediates analysis, released Cl- content, and Gaussian 09 simulation by establishing oxidative/reductive reaction systems in dissolved CHC phase and DNAPL phase. From both radical scavenging test and free radicals strength change aspects, the CHC degradation contributions by oxidative and reductive free radicals, respectively, will be investigated, and the effects of groundwater characteristics and mineral compositions in soil medium on CHC degradation efficiency will be evaluated. It is anticipated that the outcome of this research would provide solid theoretical basis for CHC contaminated groundwater remediation in practice.