Research of Agricultural Non-point Source Pollution Load in Dongjianghu Lake Watershed

Soil erosion is the main output way of adsorbent nitrogen and phosphorus pollution as well as an important link of non-point source (NPS) pollution assessment. Taking the Dongjianghu Lake watershed as the main study area, the Universal Soil Loss Equation (USLE) and experience equation of nitrogen and phosphorus pollution load were used to estimate the pollution load of adsorbent nitrogen and phosphorus in the watershed. The research focused on extracting and analyzing the farmland NPS pollution load, and then identified the key areas of agricultural NPS pollution, so as to provide a scientific basis for decreasing and controlling the loss of nitrogen and phosphorus from agriculture sources. The results showed that in Dongjianghu Lake watershed, the total amount of soil erosion of agricultural NPS pollution was 1.447×10⁶ t, and the total amount of adsorbent nitrogen and phosphorus loss was 2 658.3 and 504.1 t, respectively, with higher loss risk of dry land than paddy field. The amount of adsorbent nitrogen and phosphorus loss generated by the application of chemical fertilizer was 1 561.9 and 215.4 t, accounting for 58.8% and 42.7% of the farmland total loss, respectively. The critical prevention and control areas of agricultural NPS pollution mainly include the Oujiang River, Zheshui River and the area around the main estuary of the lake.