黑臭水体沉积物耗氧过程对重金属释放及其生物有效性的影响机制

Pollution by oxygen-consuming substances in the aquatic systems is a significant national water pollution problem in China, which has a great impact on the health of aquatic ecosystems. Sediment oxygen demand (SOD) is one of the important factors affecting oxygen balance in water systems, accounting for 20% ~ 100% of the total oxygen consumption. SOD will inevitably lead to the change of the redox potential at the sediment-water interface, which may affect the transformation and mobility of heavy metals in the sediments, but the mechanism for such a phenomenon remains unclear. In this study, basing on field monitoring and laboratory simulation, the typical black and malodorous rivers in the Haihe River Basin will be selected for studying: 1) the redox properties of sediments under low dissolved oxygen condition; 2) the contribution rates of biological SOD and chemical SOD to the total SOD and the key oxygen consumption process; 3) the fractions, release flux, and bioavailability of heavy metals in the sediments simultaneously; and 4) the effects and mechanism of critical oxygen consuming process on heavy metal fractions, release flux, and bioavailability. The outcome of this study will provide a scientific basis and theoretical guidance for the sediment quality restoration of black and malodorous water body in China.

耗氧污染是当前全国性的水污染问题，对水生态系统健康影响的甚大，主要表现为水体发黑、发臭，即黑臭水体。沉积物耗氧可占水体耗氧量的20%~100%，其过程势必导致沉积物-水界面氧化还原特性发生变化，进而影响沉积物中重金属的迁移转化，但对于这一过程驱动机制和内在机理的认识仍为空白。本项目计划以海河流域典型黑臭河流为对象，综合利用柱培养法、微电极法、薄膜梯度扩散技术等，通过野外监控和实验室模拟相结合，研究黑臭水体低溶氧条件下沉积物的氧化还原特性，并区分化学耗氧与生物耗氧对沉积物耗氧的贡献，揭示关键耗氧过程和主要耗氧因子；同步分析沉积物中重金属赋存形态、释放通量、生物有效性及其耦合关系，揭示关键耗氧过程中重金属形态的转化规律，探索关键耗氧过程对重金属释放通量及其生物有效性的影响机制和关键机理，将为我国黑臭水体沉积物质量修复提供科学依据和理论指导。

耗氧污染是当前全国性水污染问题，主要表现为水体发黑、发臭，即黑臭水体。沉积物耗氧可占水体耗氧量20%~100%，其过程会导致沉积物-水界面氧化还原性质发生变化，进而影响沉积物中重金属迁移转化。本项目以海河流域典型黑臭河流为对象，研究了黑臭河流低溶氧条件下沉积物氧化还原特性，揭示了关键耗氧过程和主要耗氧因子，同步分析了沉积物中重金属赋存形态及其生物有效性，初步探明了关键耗氧过程中重金属形态的转化，及其对重金属生物有效性的影响机制。研究发现：①海河流域平原河流沉积物基本处于弱还原或还原环境（< 90 mV），AVS、活性铁、亚铁等是沉积物氧化还原性质的主控因素；②黑臭河流化学耗氧是沉积物耗氧主要贡献者，Fe2+耗氧是化学耗氧主要贡献者，Fe2+和S2−是主要耗氧因子；③黑臭河流沉积物多为强还原环境，沉积物中重金属含量多数超过背景值，主要源于人为活动，且生物有效性高，潜在生态风险较大；④黑臭河流沉积物在耗氧过程中，沉积物氧化还原电位主要受硫体系控制，引起部分重金属向上覆水中释放，且化学耗氧会导致这些重金属生物有效态含量上升（1-5倍）。上述认识将可为我国黑臭水体沉积物质量修复提供科学依据和理论指导。项目目前已发表前三标注SCI文章15篇，申请专利2项。