Estimation of pollution loads from agricultural nonpoint sources in Beijing region based on export coefficient modeling approach

Nonpoint source pollutants produced from agricultural production activity is one of the major pollutant sources for environmental pollution. Pollution loads from agricultural nonpoint sources in Beijing City were estimated according to the approach of export coefficient modeling. The results demonstrated that total nitrogen and total phosphorus loads in Beijing City respectively were 19565.7 and 2413.1 Mg a-1 in 2006. Total nitrogen and phosphorus loads was affected by types of land utilization significantly . The contributions to pollution load from various types of pollutant sources were different. The magnitude order of the contribution from various types of pollutant sources was wastewater and garbage from rural residents > cultivated land > forest land > livestock and poultry breeding > garden plot > grassplot for total nitrogen load, and wastewater and garbage from rural residents > livestock and poultry breeding > cultivated land > forest land > garden plot > grassplot for total phosphorus load, respectively. The differences among various districts/counties in Beijing about total nitrogen and total phosphorus loads and their load intensities were great. Total nitrogen and total phosphorous loads in Daxing, Shunyi, Fangshan, Miyun, and Tongzhou Districts were bigger, and the load intensities of total nitrogen and total phosphorous in Chaoyang, Fengtai, Tongzhou, Shunyi, and Daxing Districts were higher. The research about the distribution of nitrogen and phosphorous pollutants and their load intensities from agricultural nonpoint sources can provide a foundation on regional planning and agricultural structure adjustment in Beijing region.