Research On The Temporal And Spatial Characteristics Of Agricultural Non-point Source Pollution And Its Relationship With Economic Development In The Loess Plateau

Agricultural ecological environment is the basis of agricultural production,is the premise of agricultural product quality and safety,is the guarantee of agricultural sustainable development.In recent years,with the rapid development of rural economy,agricultural production investment is increasing,agricultural non-point source pollution problem is becoming increasingly prominent.It is urgent to strengthen the control of agricultural non-point source pollution,promote the protection and control of agricultural ecological environment,change the mode of agricultural development,and promote the sustainable development of agriculture.At present,the government has issued a series of policies to control agricultural non-point source pollution,such as the 2015 release of the Ministry of agriculture on the implementation of the agricultural non-point source pollution prevention and control battle opinions;The report also proposed " strengthening soil pollution control and remediation,strengthening agricultural non-point source pollution prevention and control,to carry out rural habitat environment remediation action".However,because of the uncertainty of agricultural non-point source pollution and pollution source,the space-time difference is large,and the formation mechanism is complex,so it is difficult to control agricultural non-point source pollution.The Loess Plateau is the region with the most shortage of "water resources and the most fragile ecological environment in China.agricultural non-point source pollution seriously restricts the healthy development of agricultural ecological environment,and even endangers the quality of life and health of the people.Based on this,this paper takes 44 prefecture-level cities in the Loess Plateau as the research unit.firstly,using inventory analysis method,iso-standard pollution load method and statistical analysis method,the temporal and spatial variation characteristics of agricultural non-point source pollution emissions and iso-standard pollution load were analyzed,and the spatial correlation was explored by exploratory spatial data analysis method,and the concentration and discrete variation laws of agricultural non-point source pollution were studied.Secondly,the Kuznets curve(EKC)of agricultural non-point source pollution environment is verified by using panel data of loess plateau from 1990 to 2015,and the stage and future development trend are judged.Thirdly,the formation mechanism is analyzed from the factors of agricultural population scale,agricultural structure,planting structure and agricultural technology level.Finally,some policy suggestions are put forward to control agricultural non-point source pollution in the loess plateau.This will provide reference for the effective control and control of agricultural non-point source pollution,and has important theoretical and practical significance for the sustainable development of agricultural ecological environment in the Loess Plateau.Based on the above research,the main conclusions are as follows:(1)The agricultural non-point source pollution and other standard pollution load in the loess plateau showed an increasing trend year by year.Farmland chemical fertilizer and livestock and poultry breeding are the main pollution sources of agricultural non-point source pollution.the primary pollution sources have been changed from livestock and poultry breeding to farmland chemical fertilizer.total nitrogen(TN)and total phosphorus(TP)are the main pollutants of agricultural non-point source pollution,among which TN is the primary pollutant.From the point of view of each pollutant,agricultural non-point source TN,TP and chemical oxygen demand(cod)pollution emissions showed an increasing trend on the whole.Agricultural chemical fertilizer has been the main source of agricultural non-point source TN pollution,livestock and poultry breeding has been the main source of agricultural non-point source TP pollution and cod pollution.(2)The total amount of agricultural non-point source pollution load shows the trend of increasing and spreading.at present,the pollution is mainly distributed in agricultural irrigation area in southern inner Mongolia,Weihe plain in southern loess plateau and rocky mountain area in western Henan.From the point of view of each pollutant,agricultural non-point source TN,TP pollution showed a trend of increasing pollution and diffusion,agricultural.non-point source cod pollution showed a trend of decreasing.At present,agricultural non-point source TN pollution is mainly distributed in Weihe plain,ningbei agricultural irrigation area and southern agricultural irrigation area of inner Mongolia.Tp pollution of agricultural non-point source is mainly distributed in Weihe plain in the south of loess plateau,rocky mountain area in the west of Henan province,Fenhe valley and agricultural irrigation area in the south of inner Mongolia.Agricultural non-point source cod pollution is mainly distributed in Weihe plain in the south of loess plateau and earth-rock mountain area in the west of Henan province.From the point of each pollution source,agricultural non-point source agricultural chemical fertilizer,farmland solid waste and rural life pollution showed the trend of increasing pollution degree and spreading,agricultural non-point source livestock and poultry breeding pollution degree showed a decreasing trend.At present,agricultural non-point source agricultural chemical fertilizer pollution is mainly distributed in the agricultural irrigation area in southern inner Mongolia,the gully area in central south of Ningxia,the Weihe plain in southern loess plateau and the rocky mountain area in western Henan.Agricultural non-point source farmland solid waste pollution is mainly distributed in Weihe plain and Fenhe valley;Agricultural non-point source rural life pollution is mainly distributed in the earth-rock mountain area of western Henan,Fenhe river valley and Weihe river plain in the south of loess plateau.Agricultural non-point source livestock and poultry breeding pollution is mainly distributed in agricultural irrigation area in southern inner Mongolia,Weihe plain in southern loess plateau and rocky mountain area in western Henan province.(3)The total amount of agricultural non-point source pollution load showed positive spatial correlation,with strong spatial agglomeration,spatial agglomeration distribution pattern,spatial agglomeration decreased.From the point of view of each pollutant,TN,TP and cod and other standard pollution load showed a spatial agglomeration distribution pattern,TP and TN spatial agglomeration decreased,cod spatial agglomeration slightly increased.From the point of view of various pollutionsources,the pollution load of farmland chemical fertilizer,farmland solid waste,livestock and poultry breeding and rural life shows a pattern of agglomeration in space.the spatial agglomeration of livestock and poultry breeding has been enhanced,while the spatial agglomeration of rural life,farmland solid waste and farmland chemical fertilizer has been reduced.(4)The total amount of agricultural non-point source pollution load was significantly higher-the number of high concentration areas showed a decreasing trend,and the center of gravity shifted westward to Weihe plain and Yuncheng city;The number of low-low concentration areas increased obviously but the distribution was scattered.The number of negative spatial autocorrelation and spatial heterogeneity increased significantly.From the point of each pollutant,TN,TP pollution significantly high-high concentration area showed an increasing trend,cod pollution showed a decreasing trend and fragmentation,spatial heterogeneity were reduced.At present,TN pollutant concentration area center of gravity to the north of Weihe plain and northern Shaanxi hilly area,TP pollution concentration area consists of two areas,Weihe plain area and western Henan earth-rock mountain area,the Weihe plain concentration area center of gravity to the east,spatial heterogeneity is reduced.From the point of view of each pollution source,the quantity of farmland chemical fertilizer pollution significantly high-high concentration area showed a downward trend,concentrated in the Weihe river plain and northern Shaanxi hilly area,spatial heterogeneity is stable.The amount of farmland solid waste pollution was significantly high-high concentration area unchanged,the center of gravity moved eastward to the Weihe river plain and Fenhe river valley,spatial heterogeneity increased.The number of livestock and poultry breeding pollution significantly high-high concentration area showed an increasing trend,concentrated in qingdonggou gully area and western Henan earth-rock mountainous area,spatial heterogeneity decreased.The number of high-concentration areas of rural life pollution is decreasing and dispersed,which is distributed in Weihe plain,Fenhe valley and western Henan earth-rock mountainous area,and the spatial heterogeneity is decreasing.(5)The total load of agricultural non-point source pollution with the evolution trend of agricultural economic growth presents an inverted u-shaped typical EKC relationship,the turning point is located at the critical point of per capita agricultural gross output value of 8015 yuan,at present,the process of agricultural economic growth in most areas will still be accompanied by the increase of total load of agricultural non-point source pollution.From the point of view of each pollutant,there are different EKC relationships between different pollutants with the growth of agricultural economy.Tn pollution presents inverted u-type EKC relationship,TP pollution presents n-type EKC relationship,cod pollution presents monotonically decreasing EKC relationship.From the point of view of each pollution source,there are different EKC relationships between different pollution sources along with agricultural economic growth.The relationship between fertilizer pollution in farmland and solid waste pollution in farmland was inverted u-shaped EKC,and n-shaped EKC.there was no significant relationship between livestock and poultry breeding pollution and per capita agricultural output value.the relationship between rural life pollution and typical curve was inverted u-shaped EKC.(6)The change trend of agricultural non-point source pollution load with per capita agricultural gross output value is still inverted u-shaped typical EKC relationship,and the turning point is at the critical value of 7924 yuan per capita agricultural gross output value,which is obtained by adding regression model of agricultural population scale factor,agricultural structure factor,planting structure factor and agricultural technology level factor.The increase of agricultural population and planting area of cash crops will increase the emission of agricultural non-point source pollution.The proportion of livestock and poultry breeding output value in total agricultural output value is increased,and agricultural non-point source pollution may show a decreasing trend.In addition,the improvement of agricultural technology level has not yet played a role in alleviating agricultural non-point source pollution emissions.