分层异重流背景下三峡水库典型支流沉积物磷迁移转化机理研究

Hydraulic conditions were altered significantly by the filling of the Three Gorges Reservoir (TGR), trapping sediment in reservoir, the enriched phosphorus associated sedimentation can be contaminated zone. Stratified density currents in tributary bays were characterized by changing plunging depth at different hydrological seasons, which can affect phosphorus transformation at the sediment-water interface by changing environmental condition and DBL and phosphorus gradients. This study will combine field monitoring and laboratory analysis to investigate environmental factor and hydraulic conditions and microbiologic population during the operation of the TGR. The response of environmental factors and microbiologic population in the sediment -water interface to density currents and the variation of DBL and phosphorus fractions will also be investigated. Then the mechanism of the phosphorus transformation at the sediment-water interface will be clarified. The key factors which affect phosphorus transformation in response to density currents will be revealed. The results will provide a theoretical basis for quantification and management of phosphorus loads, and also be of theoretical and practical significance on algal bloom control in the TGR region.

三峡水库蓄水后，水动力条件变化，泥沙沉降、累积并富集大量磷营养盐，形成沉积物污染带。在水库不同水位运行期，支流库湾普遍存在表、中、底层不同形式分层异重流，分层异重流的存在改变了沉积物磷赋存环境，压缩了沉积物扩散边界层厚度(DBL)，影响沉积物中磷形态转化及磷在沉积物-上覆水中的浓度梯度，进而影响沉积物中磷迁移扩散过程。本研究以三峡水库香溪河支流库湾为研究对象，通过野外监测和室内分析等方法，监测水库运行过程中沉积物-水界面水动力条件、水环境因子和微生物群落等变化过程，分析沉积物表面环境因子和微生物群落对分层异重流水动力过程的响应关系，以及沉积物中磷赋存形态和DBL变化规律，探明三峡水库支流沉积物磷迁移转化驱动机制，揭示分层异重流动力背景下影响沉积物磷迁移转化的关键因子及其影响机制。研究成果为内源磷负荷计算及控制提供理论基础，对防控支流库湾水华具有理论价值和现实意义。

项目以三峡水库典型支流香溪河库湾为研究对象，开展了三峡水库香溪河库湾上覆水环境条件和沉积物理化性质野外监测和室内分析，系统分析了库湾分层异重流的特殊水动力背景及在分层异重流背景下沉积物赋存环境、微生物群落结构分布特征，研究在水库运行过程中沉积物及孔隙水中磷的时空变化规律，阐明香溪河沉积物磷源-汇关系、界面交换通量及微生物对沉积物-水系统中磷迁移转化的影响。项目研究过程中积累了大量的监测数据，为进一步开展三峡水库香溪河库湾沉积物赋存环境及内源磷控制提供支撑。研究成果在《Journal of Hydrology》、《环境科学》等国内外期刊上发表已标注论文10篇，其中SCI4篇，EI2篇；申报专利2项。另外有关的研究成果正在整理，预计发表3篇论文。