Abstract:

Nitrogen loss load of non-point source in small watershed was calculated and analysis and control research of water pollution sources in  Danjiangkou were carried out. Based on the monitoring of watershed section and runoff plots, the average annual nitrogen loss modulus and nonpoint source pollution nitrogen load of different land use types were calculated using mean concentration method in Yingwugou watershed. The results showed that the total nitrogen content was the major exceeded pollutant in runoff and nitrate nitrogen content was always greater than the ammonia content. When the slope of sloping cropland was greater than 25°, severe nitrogen loss and poor water quality happened. The rural production and living pollutant emissions had a great impact on water quality. Nitrate nitrogen concentration and total nitrogen concentration both increased greatly from watershed section 1 to mouth station. The average annual total nitrogen loss modulus of farmland, grassland and forestland were 0.36, 0.22 and 0.09 t／(a·km²), respectively. The average non-point source pollutant concentration of ammonia nitrogen, nitrate nitrogen and total nitrogen in watershed export were 0.17, 4.71 and 7.55 mg/L, respectively. The average point source pollutant concentration of ammonia nitrogen, nitrate nitrogen and total nitrogen in watershed export were 0.20, 2.12 and 4.08 mg / L, respectively. The average total nitrogen runoff loss modulus in Yingwugou watershed was 0.89 t／(a·km²). The total nitrogen is the major pollutant affecting water quality. The nitrogen loss of sloping farmland and rural garbage must be controlled effectively.

Key words: non-point source pollution, total nitrogen, Dan River, mean concentration method, nitrogen loss modulus