A GIS Based Estimation of Loss of Particulate Nitrogen and Phosphorus in Typical Drainage Area of Pearl River Delta

摘要

The output of nitrogen and phosphorus from agricultural activities is the main source for water eutrophication.The fully developed agriculture in vegetables,fruits and flowers in Pearl River Delta gives rise to excessive use of chemical matter such as fertilizer and pesticide and thus bring about the serious water pollution because of the loss of nitrogen (N) and phosphorus (P) from the farmland in the region.Based on Geographic Information System (GIS) and soil pollution data,Universal Soil Loss Equation (USLE) and source type method are used to estimate the loads of particulate N and P from the soil of different land use types in the drainage area of Liuxi River in Guangzhou,China.So the key regions those the NPS pollution occurred can be confirmed and the technical support for the pollution control target and the capital flow concentration can be provided by the results.The study shows that,(1) The total loss of particulate N and P in the drainage area is 582.49 t/a and 424.74 t/a respectively.Among them the loss of particulate N from paddy soil occupies 40.02% and that of forest 6.31%,while the loss of particulate P from the soil of dry-land accounts for 28.75% and that of paddy soil 26.31%.(2) There are significantly different losses of particulate N and P per unit area from the soils of different source land use types in the drainage area.The losses of particulate N and P per unit area are both the highest from the soil of dry-land,which is 7.72 kg/hm2 and 9.50 kg/hm2 respectively,followed by those of orchard,which is 7.20 kg/hm2 and 6.56 kg/hm2 respectively.The causes are excessive use of chemical matter,unreasonable cultivation pattern,and the soil erosion of different land use.(3) The excessive N and P come from the loss of particulate N and P from the fertilization in agricultural production,and they are the main source of the pollutants in Liuxi River water.