Study On Spatial Characteristics And Influencing Factors Of Non-point Source Pollution In Shandong Province

Non-point source pollution is the biggest threat to the deterioration of water quality in the world.Shandong province is a populous and agricultural province.Meanwhile,intensive human activities have made non-point source pollution increasingly serious.Making clear the spatial distribution and influence of non-point source pollution in shandong province is of great reference value to the overall planning and management of water resources in shandong province.In this paper,the daily rainfall,DEM,soil classification and land use data of shandong province from 2010 to 2015were collected.The sub-watershed was used as the control unit,and the simulated values of TN and TP point source pollution were estimated by using the L-THIA model.The spatial differentiation and annual seasonal variation of non-point source pollution simulation results in Shandong province were studied and analyzed,and the different modes of non-point source pollution in Shandong province were defined by self-organizing mapping network(SOM).Finally,the natural and social factors affecting the non-point source pollution of TN and TP in different scales in Shandong province were explored based on geographical detector.The main research results are as follows:(1)The total loads of TN and TP of non-point source pollution in shandong province were 681404.33t and 38623.91t,and the average pollution load per unit area of TN and TP was 4434.19kg/km~2 and 252.87kg/km~2 by using the L-THIA model.From the perspective of spatial characteristics,the spatial variation trend of TN and TP shows the spatial distribution characteristics of high in the west and low in the east.The areas with high distribution of pollution load are mainly concentrated in the Nansi lake basin,the lower reaches of the Yi-shu river and the lower reaches of the Tuhai-majia river.(2)The seasonal variation of non-point source pollution load in different quarter in shandong province was obtained by using rainfall driven L-THIA model,which the changes of in the third quarter>in the second quarter>in the first and fourth quarters.The spatial variation of TP non-point source pollution is greatly affected by the quarter of the year.The spatial variation was larger in the second and third quarters and smaller in the first and fourth quarters.However,the spatial variation of TN non-point source pollution is less affected by the quarter of the year.(3)Based on the surface pollution data of sub-watershed,three different pollution patterns were obtained by SOM clustering model analysis and the analysis of surface pollution characteristics in Shandong province.The area of"high load risk model of plain"is mainly in the plains of the west lake and LuXiBei plains,TN load per unit area is 5262.36 kg/km~2,TP load per unit area is 293.27 kg/km~2.The area of"high-low altitude and high load risk model"is mainly located in some mountainous areas in the south of Shandong province,some hills in Jiaodong peninsula and the lower Yellow River plain.TN unit area load is 4503.03 kg/km~2,and TP unit area load is 252.475kg/km~2.The area of"high altitude and low load risk mode"is mainly located in the middle mountain area of shandong and the middle of Jiaodong peninsula,TN unit area load is 3225.32kg/km~2 and TP unit area load is 196.27kg/km~2.(4)The influence factors of non-point source pollution under"double scale"in Shandong province were investigated based on geographical detector.At the provincial level,soil clay content,soil sand content and cultivated land area,construction land area,fertilizer purity have a great influence on the spatial variation of TN and TP non-point source pollution.At the pollution pattern scale,the influence degree of both natural factors and social and economic factors showed a weakening trend,among which the weakening trend of natural factors was the most obvious,and the q statistical value was lower than 0.5.Social and economic factors,such as cultivated land area,construction land area,gross output value of agriculture,forestry,animal husbandry,fishery and conversion amount of chemical fertilizer,maintained a high q statistical value,and the influence degree of other social factors also decreased significantly.