The study analyzed nitrogen pollution in the Weihe River. From 1976 to 2000, nitrogen concentrations increased, with NH-3-N and NO-3-N levels fluctuating less in the 1990s than the 1980s. NO-3-N levels surpassed NH-3-N until 1993, then reversed. NH-3-N levels were higher in low flow seasons due to reduced runoff and sewage. Nitrogen pollution from both point and non-point sources rose, with non-point sources like industrial wastewater and excessive fertilizer use being the main contributors.