Abstract:

Rural nonpoint source pollution is serious and environmental problems intensified in Poyang Lake small watershed. It is of great urgency to control agricultural pollution, because the pollution from agriculture is more wide and serious compared with others. Agricultural pollution is principally transported from agricultural land. The harm is more serious than point source pollutions and hard to be monitored and controlled, because the indefinite quantity of agricultural pollutants are discharged during uncertain period through uncertain process. The rural life and farming are the main source of rural nonpoint source pollution through the background investigation and analysis of pollution sources in Poyang Lake small watershed. Farming in the demonstration area is one of the main sources of rural nonpoint source pollution, the proportion of total, nitrogen and phosphorus load more than 50%, 48% and 49%, respectively. Country life is also an important source of rural nonpoint source pollution. Nitrogen and phosphorus loss can be intercepted effectively by integrated BMPs, in which source control and end treatments are combined, buffer, ditch wetland, artificial wetland, facultative pond are added into a group rationally. Pollutant cutting quantity per area of the whole system is 71017 kg of CODcr, 11491 kg of SS, 408 kg of TP, 1918 kg of NH+4N, 474 kg of NO-3N and 3593 kg of TN respectively, while the total investment is less than 27 thousand yuan, i.e. investment cost of less than 2 700 yuan/m3, and the operation cost less than 01 yuan/m3. The cutting quantity of SS through buffer zones is 63.07 kg, accounted for 50% of all. The surface flow constructed wetland has the highest removal capacity and impact resistance, through which total nitrogen can be cut down more than 30 g per unit area. Adsorption capacity of phosphorus by wetland soil is also high. Equilibrium Phosphorus Concentration (EPC0) of Wetland substrate is lower than 0.05 mg/L. If inflow concentration of SPR of wetland is higher than EPC0, wetland is for phosphorus “source”; by contrast if inflow concentration of SPR of wetland is less than EPC0, wetlands is for phosphorus “collect”. But the reduction of nitrate nitrogen ability is not strong; the followed facultative pond just make up for the defect, reductions of nitrate nitrogen stay above 013 g/m2. Overall, decontamination ability of ditch wetland is not low, but the capacity of resisting impact load is weak, easily affected by external factor. Decontamination ability can be enhanced by improving the ecosystem, the emergent macrophytes especially