Evaluation Of Source-sink Risk Pattern Of Agricultural Non-point Source Pollution In Cultivated Land Based On MCR Model

With the development of science and technology,the agricultural development of our country has stepped into the stage of specialization,intensification and industrialization.The use of a large number of pesticides and fertilizers increased the productivity of crops on the one hand,and on the other hand,it would cause eutrophication of the water body.In the process of agricultural activities,people use a lot of agricultural chemicals(fertilizers and pesticides),livestock manure and rural sewage treatment,without the wanton discharge of rural residents in the concept of environmental protection publicity and rural management subject in environmental protection failed to fulfill its duties,are the main cause of agricultural non-point source pollution.The main cause of the agricultural non-point source pollution is the residual nitrogen,phosphorus and other nutrients,which are outflow from the cultivated land.In addition to the impact of human activity on the occurrence of source pollution,the influence of external natural conditions also has an important impact.Therefore,it is important to study the influence of natural conditions on the source pollution and identify the high risk areas of non-point source pollution by natural factors.This study takes Beibei District of Chongqing city as the research object,through the 8km offset buffer is set on the Jialing River as the center of the way,the land source of Beibei landscape is divided into 4 grades,and the topography,soil,vegetation,climate and other natural factors on the impact of non-point source pollution overlay Analysis on formation model of resistance surface the minimum cumulative resistance model to measure different levels of landscape source resistance surface,Con function to extract the surface resistance of Dryland and paddy,finally,arable land non-point source pollution source sink risk pattern,the results of the study show that:(1)classification results of source landscapeBy setting up the Jialing River as the center to establish the buffer zone,the cultivated land in Beibei is divided into 4 levels.A source of cultivated land landscape distance of Jialing River 0~8km,mainly distributed in the town of North Spring Street,Dragon Bridge Street,Dongyang street,Chengjiang Town,town,town,town,and Tianfu Shijiang Town,Fuxing Town,Zhen Caijiaying,tong.It accounts for 42.84%of the total arable land in Beibei.The area of dry land is more than that of paddy field.The distribution of dryland landscape is concentrated in Tianfu town and Longfeng Bridge Street,while the concentration of water Tian Yuan landscape in Chengjiang town is relatively high.The proportion of the landscape area of the first grade paddy field and the dry land is above 40%.Two level of cultivated land landscape of Jialing River source distance 8~16km,mainly distributed in the town,Tianfu town,town,town,and contemplation,Sansheng town renaissance town.The area is 59.68km~2,which accounts for 26.57%of the total arable land.The area of dry land is 33.40km~2,and the area of paddy field is 26.28km~2.The area of dry land is larger than that of paddy field.Three level of cultivated land landscape distribution in the Jialing River from the source in the range of 16~24km,located in the town of Trinity,the contemplation of the town and the town of willow.The area is 50.66km~2,accounting for 22.56%.Four source landscape distance of Jialing River Zuiyuan,in the 24~32km buffer area,18.03km~2 area.The proportion of cultivated land in the whole area is 8.03%.Four source landscape is mainly distributed in the territory of Jindaoxia town and the town of willow,paddy field and dry land area ratio is less than 10%.(2)construction result of evaluation index system of land source pollution in cultivated landTo construct a natural factor evaluation index system which affects the agricultural non-point source pollution in Beibei district.The data sources related to the key factors affecting the non-point source pollution of cultivated land were decomposed into 7indicators,namely,relative elevation,relative slope,surface roughness,rainfall erosivity,landform wetness index,soil erodibility and vegetation coverage.(3)risk identification result of source-sink land source landscape source pollution(3)Beibei district agricultural non-point source pollution is divided into 5 levels,each level area in order as follows,very high risk zone(509.10km~2)>high risk area(144.41km~2)>medium risk area(62.02km~2)>low risk area(27.68km~2)>Extremely low risk area(9.13km~2),the high risk and high risk ratio 86.88%,agricultural non-point source pollution in Beibei area visible situation is grim.High risk and high risk areas are mainly distributed in the streets of Dongyang,Fuxing town and Chengjiang Town,the town,town,town,see Sam Tianfu town and other areas,and most of these areas in the hilly Valley,valley flat terrain,fertile soil,abundant water resources,is conducive to the development of Agriculture,the region from the Jialing River is near.The source of cultivated land landscape distribution,upland and water Tian Yuan landscape main gathering area,the main agricultural development zone and Beibei district.The low risk areas and extremely low risk areas of non-point source pollution are mainly distributed in the mountainous and urban functional areas.Such as the Chengjiang town of West and East,West,east of the town of Sam Xiema town and Jindaoxia town in northern mountainous areas,these areas are respectively in the Beibei District of"five four zone"Jinyun Mountain natural protection zone,ecological restoration in Liangshan,with the dragon hole mountain ecological conservation zone and Jindaoxia ecological conservation zone.In the ecological area,the vegetation coverage rate is high,the ecological environment is excellent,and it is a national restricted and prohibited development area.Therefore,the distribution of cultivated land in the region is scarce.