三峡库区富磷岩溶流域磷迁移转化规律及其对水文过程的响应

Eutrophication is a complex global environmental issue, and the eutrophication in the Three Gorges Reservoir Area has caused great world's concerns, especially in its impoundment tributaries. Taking those rich phosphorus watersheds in the Three Gorges Reservoir area, where human beings exert less influences as the research object, we would explore phosphorous species composition and spatial and temporal characteristics, as well as the geological origin of phosphorus in various media / transport and transformation of the water (surface water and groundwater) and sediments (soil, river sediment, phosphate rock and weathered clastic rock) in geologic rich phosphorus watersheds at the natural state, by means of field sampling, fixed-point sampling and continuous sampling of the sediment, water and other multiple mediums under different hydrological time scales (hydrological season scale and rain scale). Using technical advantages of the automated real-time monitoring technology, advanced field survey tools and test technology, we would like to study on the response mechanisms of the phosphorus morphology (with emphasis on the geological origin of phosphorus) and the content in different mediums to hydrological processes under various watershed hydrological time scales. Basing on these researches, we attempt to assess the contribution of phosphorus eutrophication of water in the rich phosphorus watersheds of Three Gorges Reservoir Area, thus, to provide a series of new scientific data for pollution control from the endogenous phosphorus nutrients in the Three Gorges reservoir and new ideas of river management at watershed scale.

水体富营养化是全球性的复杂环境问题，长江三峡库区，尤其是其支流在蓄水后出现富营养化的问题已引起全球高度的关注。在三峡库区人为干扰小、地质成因磷丰富的流域，对沉积物(磷块岩、土壤、河流沉积物和风化碎屑岩)、水(地下水、地表水和土壤水)等多介质，在不同水文时间尺度（水文季节尺度和场雨尺度）下进行实地、定点和连续取样，利用自动化监测实时监测技术、先进的野外调查手段和测试技术等技术优势，探讨自然状态下地质成因富磷流域中水体和沉积物中磷的形态组成和时空分布特征，以及地质成因磷在各介质中/间的迁移转化规律，研究各介质中磷的形态（重点是地质成因磷）及含量对流域不同水文时间尺度下水文过程的响应机制，评估长江三峡库区富磷流域磷对库区水体富营养化的贡献，为尚未探明和尚未引起重视的长江三峡水库内源营养物质磷的污染控制提供新的科学数据，为流域管理提供新的思路。

本项目在对前人研究成果的充分调研基础上，以三峡库区内香溪河典型岩溶流域为研究区域，采用野外采样和长期连续观测、室内测试实验和理论分析相结合，在分析岩溶流域水循环方式、水化学特征和同位素地球化学特征的基础上，研究流域系统内磷的形态组成及时空分布特征、迁移转化规律、以及地质成因磷对水循环过程的响应研究。具体结论主要有：1）在泄水和蓄水过程中，香溪河干流水体总磷、总氮浓度都超过国际公认的富营养化阈值。蓄水过程中干流总磷浓度整体呈下降趋势。2）经估算香溪河流域因水土流失携带的总氮、总磷、有效氮和有效磷分别为3221.07t/a、10123.21t/a、1813.42t/a和2679.52t/a。3）在上游TP含量为丰水期>平水期>枯水期，在中下游TP浓度丰、平、枯三期相差较小。在上游TP浓度波动较大，受岩溶山区地下水地表水相互转化及水动力条件影响大，在中游TP浓度变化幅度小，在下游TP浓度增幅大，显示出大比降的流域汇流特征使得大量TP快速汇入河道向河口输送并沉降下来。4）南阳河流域TP含量高于国际公认的富营养化阈值，反映出在高磷的地质背景区域，香溪河流域地质成因磷的释放作用也不可忽视。南阳河流域估算TP输出总量为5.007t/a，DTP输出总量为4.172t/a。