Pollutant District Control In Tiaoxi Inlet Of Taihu Lake

The eutrophication of Taihu Lake water has been a cause for concern.Tiaoxi River is the main inflow river around the lake.Based on the census data of pollution,land use and water quality monitoring data of Tiaoxi,the pollutant discharge quantity was calculated.Based on the methods of mathematical statistics analysis,the Geographical Information System(GIS)and the watershed distributed hydrological model-soil water assessment model(SWAT)to analyze the source structure and divide the partition.And the effect of Best Management Practices(BMPs)on nonpoint source control in Tiaoxi Watershed was evaluated.The main results was showed asfollows:(1)According to the pollution census data from 2011 to 2014,the pollutant discharge quality of COD,NH3-N,TN,TP from industrial enterprises source,town living source,farmland runoff source,livestock and poultry breeding source,aquaculture source and rural living source in the lake inlet of Tiaoxi were calculated.Atmospheric nitrogen deposition was monitored once it rains.It is shown that the annual discharge of pollutants in the researched area was COD 11655.79t/a,NH3-N 1944.21t/a,TN 3543.60t/a and TP 407.62t/a.The emission per unit area in economic-development zone were highest which were chiefly from town living source,and the water-sensitive areas were the lowest.The main pollution sources in the lake-protected areas are rural living and agricultural non-point sources,and the pollution load sources in the ecological-security areas are scattered.(2)Based on the platform of ArcGIS,the monitoring points were set.16 monitoring points were set to monitor the water quality of Tiaoxi.It is shown that COD and NH3-N in the study area all meet the water standard of the surface water class III,and TP in part areas reached this standard.The chief contaminant was TN.(3)A watershed distributed hydrological model--SWAT model for Tiaoxi watershed was established.19 management scenarios impacting nutrient loss were applied and analyzed.These scenarios included domestic sewage control measures,livestock and poultry breeding control measures,farmland management measures(e.g.cropping,landscape change)and interception measures(vegetation filter belt and grassland waterway).The results revealed that the reduction of domestic sewage is better than that of livestock and poultry,which is related to the contribution rate of domestic sewage and livestock and poultry breeding to nitrogen and phosphorus load in the study area.Contour planting operation is better than returning farmland to forest when less than 10%of the arable land returned to forest land,which is equivalent to 15%of returning farmland to forest.The implementation of soil and water conservation measures such as contour planting and interception measures can effectively reduce the non-point source pollution load in the basin,so the soil and water conservation measures should be strengthened in this area.(4)The land use type,water quality,catchment area,environmental function zoning and other comprehensive consideration,the Wuxing District was divided into Binhu protected area(area A),Economic development area(area B),ecological security area(area C)and water sensitive area(area D)four partition modules.The emissions per unit area in economic development area were highest which chiefly from town living source.For this region,the measure of reforming the urban sewage collection system and sewage treatment plants will be taken;Water pollution in the water-sensitive areas is the lowest,and the pollution of agricultural non-point source pollution is mainly carried out.The rural life and farmland runoff pollution are higher in Binhu protected area,and this area affected significantly by river network.For the region,agricultural non-point source and river network pollution control is mainly carried out.Ecological protection area pollution load source is more dispersed,and relative to other areas,there are more livestock and poultry breeding and aquaculture pollution,so aimed this area mainly for livestock and poultry and aquaculture and agricultural non-point source control.