生物炭-含铁矿物共沉淀的氧化还原波动转化及其影响有机污染物降解研究

Both biochar and iron-bearing mineral can separately catalyze electron transfer and pollutant degradation processes. However, these two important redox-active components usually coexist as coprecipitate and other complexes in soil environment. In-depth research is needed due to a lack of knowledge on the structure and composition, transformation pathway and reactivity of biochar and iron-bearing mineral coprecipitate. Chemical and biological methods would be used here to prepare several typical coprecipitates of biochar and iron-bearing mineral. The structure, composition and redox activity changes of the coprecipitates under redox fluctuation conditions would be characterized by a combination of microscopic, spectroscopic and electrochemical methods. The impacts of the coprecipitate on transformation and degradation of chloro- and nitro-substituted aromatics through mediating anaerobic bioreduction and forming hydroxyl radical under aerobic conditions would also be explored. Based on these research results, the applicant intends to analyze the behavior and mechanism of coprecipitate’s coupled iron and carbon transformation during cyclic redox process. The influence rule and mechanism of coprecipitate's dynamic structure and composition changes on its electron exchange capacity and degradation reactivity would be elucidated. The research would deepen the understanding of the combined effects of various redox-active species and different ways of electron transfer/storage on transformation and fate of pollutants. It is hoped that this research would provide guidance for improved remediation of polluted soil by reasonably regulating soil redox conditions and the structure and composition of coprecipitate.

生物炭和含铁矿物可分别催化电子传递与污染物降解，但在土壤环境中这两种重要的固相氧化还原活性组分往往以共沉淀等复合体的形式共存。目前对生物炭-含铁矿物共沉淀的结构组成、转化途径及反应活性等认识有限，值得开展深入研究。本课题利用化学和生物方法合成多种典型生物炭-含铁矿物共沉淀，结合显微学、光谱学和电化学技术表征氧化还原波动条件下共沉淀结构组成与氧化还原活性的变化，探究共沉淀通过介导微生物厌氧还原与好氧产羟基降解转化卤代和硝基芳烃等有机污染物的表现。基于上述研究结果，解析氧化还原交替循环过程中共沉淀碳铁组分的耦合转化行为与机理，阐明好氧/缺氧界面上共沉淀结构组成的动态变化对其催化电子传递能力和降解反应活性的影响规律与机制，深化对土壤环境中多种氧化还原活性物种及不同电子传递/存储方式联合作用影响污染物转化归趋的理解，以期指导通过合理调控氧化还原条件与共沉淀结构组成强化对受污染土壤的治理与修复。

自然及人工过程所产生的生物炭颗粒可与天然环境中的含铁矿物形成共沉淀物。本项目关注上述共沉淀物在氧化还原波动条件下的转化行为及其对环境污染物降解的影响。利用生物与非生物方法成功合成并表征生物炭-含铁矿物共沉淀物，解析不同条件下共沉淀物的形成机制；系统探究了氧化还原波动条件下共沉淀中碳铁元素耦合转化过程及其调控机制；深入揭示了共沉淀氧化还原活性组分构成及其动态变化规律；基于对氧化还原波动条件下磺胺抗生素等污染物降解产物的分析，阐释共沉淀影响有机污染物降解的路径与机制。本项目还系统考察了水动力条件下生物炭、含铁矿物及微生物细胞等胶体颗粒在饱和多孔介质中的穿透和沉积规律；首次揭示了微生物细胞与生物炭和含铁矿物等氧化还原活性介质间的胞外电子传递活性对胶体运移行为的重要作用。本项目研究成果深化了对天然环境中微生物细胞与生物炭和含铁矿物等氧化还原活性颗粒相互作用的认识，为改善污染场地的生物修复效果奠定理论和技术基础。