Spatial Distribution Of Nitrogen And Phosphorus In Soil And Risk Assessment Of Soil Loss In Chaohu Basin Of Feidong County

Agricultural non-point nitrogen and phosphorus pollution is the main factor causing the deterioration of water quality in Chaohu Lake.The study shows that nitrogen and phosphorus are the main contributing factors to eutrophication of water body,among which nitrogen and phosphorus in farmland soil are the main sources of its output.The loss of nitrogen and phosphorus in farmland is closely related to the occurrence of eutrophication.In this dissertation,Chaohu watershed of Feidong was selected as the research area,the risk of soil nitrogen and phosphorus loss in farmland was studied,and the distribution of soil nitrogen and phosphorus source factors and migration factors,as well as the characteristics of non-point source loss in lake confluence area were analyzed and evaluated.Based on the analysis of nitrogen and phosphorus content in farmland soil and its spatial distribution,the nitrogen and phosphorus index method was used to analyze the nitrogen and phosphorus content in farmland soil.The risk of nitrogen and phosphorus loss was evaluated,the key sources of nitrogen and phosphorus loss were identified,and put forward targeted prevention and control measures.The main findings are as follows:1)The total nitrogen content in the study area was 0.648¹.896 g kg^-1,the average value was 1.19 g·kg^-1,and the available phosphorus content was 5.26³8.23 mg·kg^-1,with an average value of 14.19 mg·kg^-1.In spatial distribution,the total nitrogen content showed a distribution pattern of low in the north,middle in the middle and high in the south.The distribution of available phosphorus was higher in the southeast,lower in the middle,and lower in the north,while the distribution of relatively high total nitrogen was found in the southeast of Dianbu,Cuozhen and Qiaotou,and the distribution of available phosphorus was relatively high in the north.In the southeast of Qiaotou Town and Dianbu Town,the distribution characteristics of soil total nitrogen and available phosphorus content were correlated with land use patterns.2)the main factors of nitrogen and phosphorus loss and migration in the study area are soil erosion,surface runoff and distance from potential sources of pollution to water bodies.Soil erosion in Chaohu Lake basin of Feidong County is mainly micro-degree and mild erosion,and extreme intensity erosion and severe erosion are mainly distributed in the eastern hilly region and coastal area of Chaohu Lake in the eastern part of the study area.The spatial distribution of runoff in the study area shows that the middle and west reaches the maximum value,and the southeastern part is the lower value area of runoff,among which there are also low value areas in the north,which are mainly related to the land use type,soil properties and so on.The risk degree of the potential nitrogen and phosphorus pollutant distance from the water body in the study area is generally moderate and low wind.The more close the potential nitrogen and phosphorus pollutant is to the water body,tThe higher the risk of loss,and Conversely,the potential nitrogen and phosphorus pollutant is the lower.3)the key sources of nitrogen and phosphorus in Chaohu basin of Feidong County show certain regularity in space,and all of them are distributed along the river.The distribution of phosphorus high risk area and extremely high risk area is very small,which only accounts for 1.97%of the total basin area.It is mainly distributed in the southwest of Qiaotou Town in the study area and 150 meters on both sides of the river in Changlinhe Town area.The distribution range of high risk area and extremely high risk area of nitrogen loss is relatively small,which only accounts for 3.76%of the total area of the basin.It is mainly distributed in the middle and south of Jiangzhen Town,the western part of Changlinhe Town and the region along the lake and the southwest region of Qiaotou Town.4)the risk level of nitrogen and phosphorus loss in the study area is determined by both the source factor and the transport factor.In the region with high source factor value,the risk level of nitrogen and phosphorus loss is not necessarily high,on the contrary,the risk of nitrogen and phosphorus loss is not necessarily low in the region with low migration factor value.Only when the source factor value and migration factor value are high can the key source region be formed.In this study,the nitrogen and phosphorus index method was used to identify the keysources of nitrogen and phosphorus non-point source pollution easily and quickly.Based on the spatial differences of soil nitrogen and phosphorus non-point source pollution,the effective control measures were put forward.In order to provide theoretical basis and practical reference for agricultural nitrogen and phosphorus pollution prevention and control in Chaohu Lake Basin.