Relationship Between Land Use And Non-point Source Pollution Output

With the development of society,the problem of ecological environment has become the focus of people’s attention.The non-point source pollution caused by land-use has also become a hot topic in current research.Based on the relationship between land-use and non-point source pollutants,this paper selected the Yellow River Delta as the research area to study the correlation between land-use and non-point source pollutants,total nitrogen（TN）,total phosphorus（TP）and chemical oxygen demand（COD）,and estimated the output load of non-point source pollutants and the amount of non-point source pollutants into the river.In order to provide scientific support for non-point source pollution control and control in the future.（1）The random forest method was used to extract the land-use in the study area,and its structural characteristics were analyzed.The results showed that the construction land,arable land and breeding land accounted for about 61%of the total area,while the proportion of woodland and other land was very small.The study area was divided into 8 zones using Arc Hydro Tools.The analysis of land use structure showed that the study area was mainly divided into paddy field in 1,aquaculture in 2,paddy field and corn field in 3,maize and aquaculture in 4 and 5,aquaculture in 6 and 7.Zone 8 is dominated by building land.（2）Based on continuous water quality monitoring and analysis data,the spatial and temporal pattern of non-point source pollution in the study area was explored.The concentrations of TN,TP and COD in each water period were higher in normal period than in high water period.In normal period,paddy field has the greatest correlation with TN concentration,farming has the greatest correlation with TP concentration,maize has the greatest correlation with COD concentration,soybean has the greatest correlation with TN and TP concentration,and forest land has the greatest correlation with COD concentration.In the normal period,each land use type mainly plays a role in intercepting TP,while in the wet period,it mainly plays a role in promoting TP output.In different periods,each land use type mainly plays a role in intercepting COD,but has different effects on TN.（3）The output coefficient method was used to estimate the output load of non-point source pollutants,and the amount of agricultural pollution sources,such as residential buildings,farmland and aquaculture,was calculated.The areas with higher pollution load per unit area have a greater relationship with land use type,mainly affected by farmland and aquaculture.The amount of agricultural pollution sources TN,TP and COD into the river is 848.37 t·a^-1,110.85 t·a^-1,4799.37t·a^-1,among which the amount of aquaculture into the river is the largest,followed by farmland pollutants,and the pollutants from residential buildings are the last.This study shows that land-use structure is closely related to the spatial and temporal pattern of non-point source pollutants,and optimization of land-use structure will be an effective and important way to reduce non-point source pollution in the future.