基于关键水文过程解析氮湿沉降下紫色土流域氮运移与再分配特征

氮（N）沉降对流域N素迁移转化的影响及其响应机制，已成为目前全球变化与地球科学研究的热点领域。基于关键水文路径对降雨-径流过程响应的敏感性差异研究，针对不同径流条件下，流域水体流经不同土地利用类型对N动态输出的影响研究还很有限。因此，本项目拟以四川省紫色土响滩河流域为研究区，通过原位径流小区和流域水文监测相结合，利用多稳定同位素（δD和δ18O、δ15N和δ18O）进行源与路径耦合示踪，揭示湿沉降在地表径流和壤中流中的分配比，探讨N湿沉降引起的地表径流和壤中流中N的再分配特征及其环境效应。借助LOADEST模型精细解析由N湿沉降导致的流域垂向关键水文过程对横向氮输出负荷的贡献。综合揭示基于关键水文过程解析氮湿沉降下紫色土流域氮运移与再分配特征，为改善流域生态系统管理，保障流域水质安全提供科学支撑，对保护长江流域水环境具有重要意义。

Nitrogen (N) deposition is an important source of N in watershed and its response mechanism has become a hot topic in global change and earth science research. Due to the different sensitivities of key hydrological paths to rainfall-runoff processes, there are still limited studies on N dynamic output under different runoff conditions and different land use types through which watershed water flows. The subtropical watershed in the purple soil area in Sichuan province is selected as a study area in the project. The aims of this project are to reveal the characteristic of N redistribution by using stable isotope (δD, δ18O, δ15N, δ18O) to trace the N source and hydrological path in situ runoff plot and stream in watershed, to quantify the contribution of each hydrological path in N transport load and N source at the vertical to horizontal interface caused by wet N deposition based on LOADEST model. It has great significance for the protection of the water environment of the Yangtze River Basin to comprehensively reveal the characteristics of nitrogen transport and redistribution in purple soil basin under the wet nitrogen deposition based on the analysis of key hydrological processes, and it also provides scientific basis for securing water quality safe and improving watershed management.