生物炭/铁质粘土矿物介导洞庭湖表层沉积物多氯代二苯并二噁英/呋喃（PCDD/Fs）脱氯降解的机制研究

The surface sediment of Dongting Lake has become a high risk area for the exposure of recalcitrant polychlorinated dibenzo-p-dioxins/furans (PCDD/Fs) pollutant, which poses a potential threat to human dietary safety and ecosystems. The use of biochar as an electron shuttle to mediate the in-situ degradation of halogenated organics in sediments is a new type of pollution control technology developed in recent years. However, little research has been conducted on the degradation mechanism and bioavailability evaluation of PCDD/Fs in actual restoration systems. The project aims to prepare biochar/iron-clay minerals composites with the best performance. Based on the electron shuttle angle, the enhanced effect of iron-clay mineral loading on the biodegradation activity of biochar was investigated. Considering the contamination of PCDD/Fs in the surface sediments of Dongting Lake, the project prepares to establish a preferred method for the restoration of PCDD/Fs contaminated sediments by biochar/iron-clay minerals, and to reveal the mechanism of PCDD/Fs migration and transformation during the restoration process, and to systemly evaluate the potential ecological risk of PCDD/Fs in the restored sediments. Comprehensive analysis of the bio-chemical coupling dechlorination mechanism of PCDD/Fs by biochar/iron-clay minerals in order to provide theoretical guidance and technical support for pollution control and remediation of recalcitrant halogenated organics in the sediments.

洞庭湖表层沉积物已成为难降解有机物多氯代二苯并二噁英/呋喃（PCDD/Fs）暴露的高风险区域，对人类饮食安全和生态系统造成潜在威胁。采用生物炭作为电子穿梭体介导沉积物中卤代有机物原位降解是近年来发展的新型污染治理技术，而针对实际修复体系中PCDD/Fs的降解行为机制和生物有效性评价的研究尚少。本项目旨在制备最佳性能的生物炭/铁质粘土矿物复合材料，基于电子穿梭角度探讨铁质粘土矿物负载对生物炭降解活性的强化效应；针对洞庭湖表层沉积物PCDD/Fs污染状况，建立生物炭/铁质粘土矿物介导PCDD/Fs污染沉积物修复的优选方法，在此基础上揭示实际修复过程中PCDD/Fs的迁移转化行为，综合评价修复沉积物中PCDD/Fs的潜在生态风险；全面解析生物炭/铁质粘土矿物介导表层沉积物PCDD/Fs脱氯降解的微生物-化学耦合机制，以期为沉积物中难降解卤代有机物的污染控制与修复技术提供理论指导和技术支撑。

平衡优化生物炭的电子穿梭性能是生物炭材料应用于卤代有机物污染沉积物修复研究的首要环节。本项目针对洞庭湖沉积物实际PCDD/Fs污染状况，优化制备出电子穿梭性能优越、稳定性良好、低成本和环境友好等优点的负载型生物炭功能材料，使其在污染物还原降解修复中具有广阔的应用前景。项目研究表明洞庭湖PCDD/Fs毒性当量值最高达8.8 pg I-TEQ·g-1，已严重超出最低风险阈值，而负载型生物炭功能材料对于PCDD/Fs毒性当量抑制率可达87.5%以上。本项目基于电子穿梭角度探讨铁质粘土矿物或零价纳米铁镍负载对生物炭降解活性的强化效应，并通过Box-Behnken响应面法建立了负载型生物炭功能材料介导沉积物修复的优选方法，在此基础上证实负载型生物炭功能材料可有效降低污染物在多介质中的迁移性并增强沉积物对于污染物的固定化作用。同时，本项目全面解析了负载型生物炭功能材料介导表层沉积物PCDD/Fs脱氯降解的电子传递机制，研究成果为固相介质中难降解卤代有机物的污染控制与修复技术提供理论指导和技术支撑。