The Weihe River in northwest China has nitrogen pollution issues, mainly from nitrate. The study looked at different forms of nitrogen to identify pollution sources. Manure, sewage, and industrial waste were the main contributors. Areas with more people and industry had higher nitrogen levels. Forests and grasslands helped reduce nitrogen. To clean up the river, it's important to treat sewage better, manage manure well, and change land use. The research aims to find ways to make the river's water cleaner by understanding where the pollution comes from and how to address it for a healthier environment.