大型水库分异作用对潜流带水体交换模式及氮迁出的影响

At present, the "dead zone" of the ocean has grown to more than 500 sites with a total area of 4.5 million square kilometers, which poses a serious threat to the marine ecosystem. How to reduce the load of nutrients such as nitrogen and phosphorus into the sea, control and reduce the "dead zone" have become a common topic facing the world. As the most common engineering in river basins in China, reservoirs change the original river flow pattern into the lake type by the variation of sediment deposition, reducing the surface oxidation area and increasing the reduction of the lower sedment layers. Is the denitrification efficiency significantly higher than that of rivers? This project will use the Three Gorges Reservoir as an example, the aims are (1) to solve the impact mechanism of a large reservoir on the water exchange pattern in the hyporheic zone with the in-situ observation and control experiment; (2)to find the nitrogen forms and flux in the water-sediment interface and the differences between reservoirs and rivers ; (3) to catch the key influence mechanism of nitrogen flux in the water-sediment interface by the exchange of water in the hyporheic zone. The solution to these three scientific issues is to provide support for exploring the function of denitrification and decontamination of reservoirs, formulating scientific measures for basin pollution control, and in-depth understanding of the ecological environmental impact of reservoirs.

目前，海洋"死亡地带(dead zone)"已增至500余处，总面积达到450万平方公里，对海洋生态系统造成严重威胁，如何降低氮磷等营养盐入海负荷、控制并缩减"死亡地带"已成为当前世界面临的共同课题。水库作为我国河流流域中最常见的工程措施，通过对泥沙的分异沉积，将潜流带交换模式由动水河流型转变为静水湖泊型，缩小了表层氧化区域，增大了下层还原范围，其脱氮效率是否较河流显著提高？本项目将针对这一疑问，以三峡水库为例，通过原位观测与控制实验，解决①大型水库对潜流带水体交换模式的影响机制、②水库水-泥界面氮迁出形态及通量与河流的差异、③潜流带水体交换对水-泥界面氮迁出通量的关键影响机制等三个科学问题，回答"较自然河流，水库建设究竟是强化了潜流带脱氮作用还是增加了溶解态氮释放风险？"这一问题，以期为发掘水库的脱氮除污功能、制定科学的流域污染治理措施，以及深入认识水库的生态环境影响提供支撑。

目前，海洋"死亡地带(dead zone)"已增至500余处，总面积达到450万平方公里，对海洋生态系统造成严重威胁，如何降低氮磷等营养盐入海负荷、控制并缩减"死亡地带"已成为当前世界面临的共同课题。水库作为我国河流流域中最常见的工程措施，通过对泥沙的分异沉积，将潜流带交换模式由动水河流型转变为静水湖泊型，缩小了表层氧化区域，增大了下层还原范围，其脱氮效率是否较河流显著提高？本项目针对这一疑问，以三峡水库和澜沧江梯级水库群为例，通过原位观测与控制实验，解决了①大型水库对潜流带水体交换模式的影响机制、②水库水-泥界面氮迁出形态及通量与河流的差异、③潜流带水体交换对水-泥界面氮迁出通量的关键影响机制等三个科学问题，研究结果表明水库沉积物和水体均是脱氮场所，水库建成后脱氮效率明显增加。项目研究可为发掘水库的脱氮除污功能、制定科学的流域污染治理措施，以及深入认识水库的生态环境影响提供支撑。