黄河长江源区的水资源开发利用和水利工程建设将显著影响水沙条件，进而影响含氮化合物迁移转化，但目前相关研究几乎为空白。本项目拟将实地监测、野外中宇宙和室内微宇宙实验以及多种同位素示踪分析技术相结合，重点阐明黄河源区河水氮的来源以及在水-沙界面的迁移转化规律。首先采用15NNO3，17ONO3和18ONO3三种同位素相结合的方法解析源区河水氮的来源。在此基础上研究源区河流水沙条件对氮迁移转化作用的影响，重点考察悬浮泥沙相的厌氧氨氧化作用、耦合硝化反硝化作用以及碳转化对氮转化作用的影响，揭示悬浮泥沙含量、粒径和组成对氮转化作用的影响机制，阐明不同水沙条件下温室气体N2O和CH4的释放规律。进一步将模拟实验和野外实地监测结果相结合，分析水利工程/水库建设对水沙条件的影响以及对氮迁移转化、河流通量和温室气体排放的影响，为黄河长江源区的水生态环境安全保障，以及水资源开发利用和水利设施建设提供科学依据。

The exploitation and utilization of water resources, and the construction of hydraulic engineering system in the source regions of the Yellow and Yangtze rivers have significant impact on water and sediment conditions, and will further influence the migration and transformation of nitrogen compounds. However, the relevant studies are few. This project intends to study the source of nitrogen and the mechanism of migration and transformation of nitrogen in the water-sediment interface in the source region of the Yellow River with the combination of field monitoring, filed medium cosmos and indoor microcosm experiments and multiple isotopic tracing technologies. Firstly, three isotopes including 5NNO3,17ONO3 and 18ONO3 will be combined to analyze the source of nitrogen in the river. On this basis, the effect of water and sediment conditions in the source regions on the migration and transformation of nitrogen will be investigated, which emphasizes the anaerobic ammonium oxidation, coupled nitrification and denitrification, and the effect of carbon transformation on nitrogen transformation in suspended sediment phase. In addition, the effect of suspended sediment concentrations, sizes and compositions on nitrogen transformation will be expounded, and the release of two greenhouse gases (N2O and CH4) under different water and sediment conditions will be clarified. Furthermore, with the combination of the results of simulation experiments and field monitoring, the effect of the reservoir construction on water and sediment conditions, nitrogen transformation and river fluxes, and greenhouse gases release will be explored. This project will provide scientific basis for the safeguard of aquatic ecosystem security, exploitation and utilization of water resources, and construction of hydraulic engineering system.