Analysis Of Influencing Factors Of Agricultural Non-point Source Pollution In The Three Gorges Reservoir Area(Chongqing Section)

The Three Gorges Reservoir(TGR) is world-renowned large water conservancy project. Since water storage in 2003, agricultural non-point source pollution(ANSP) has been one of the main causes of water pollution and soil pollution, which restricts the sustainable development of the ecological environment and economic.Water environment safety is related to reservoir area and even the whole Yangtze river basin ecological environment security, so find out the crucial of the rural non-point source pollution source is significant.In the current study of non-point source pollution to a certain extent reveals the sources of pollutants and influence degree.But the limitation is lack of research on spatial correlation between pollutants and the pollution sources, without which fully considering to study the driving factors affecting agricultural non-point source pollution from the relationship between the distribution of pollution sources.This paper aims to analyze the relationship between the discharge amounts of the sources of the ANSP including total nitrogen(TN), total phosphorus(TP), COD and BOD5 and their influencing factors in the TGR area of Chongqing section which 21 districts(counties) involve. Firstly, this paper analyzes the character of the discharge amounts of each pollutant in 2011 by adopting hot spot analysis and fuzzy cluster analysis. This paper chooses the ordinary Kriging interpolation method on natural factors by the contrast test analysis.The traditional linear regression model and the traditional autoregressive model are constructed to analyze the relationship between natural factors and the emission rate of pollutants. At last, the spatial error model is constructed to analyze the relationship between social economic driving factors and the emission rate of pollutants.The purpose is to enrich the research about ANSP of the TGR,and to take corresponding measures to provide scientific basis for prevention and control ANSP. The results indicated that:(1)The total discharge amounts of the four pollutants are mainly concentrated on the periphery of the hinderland and along the Yangtze River region of the hinderland in the TGR area of Chongqing section.While the total discharge amounts of the four pollutants in urban area especially the Dadukou District and Nan’an District is low.(2)OK, IDW and SPLINE interpolation methods are adopted to compare precision, which indicates the priority is SPLINE<IDW<OK.The ordinary Kriging interpolation method is used on analysis of precipitation and slope.(3)P value of precipitation in AR model reaches the significant level.There is a positive correlation between precipitation and pollutant emission rate, which means the greater the amount of precipitation is, the more serious soil erosion is, and the degree of pollution may be more serious.In the spatial distribution, there is a good corresponding relationship between the precipitation and the degree of ANSP.At the same time scale, heavy rain or rainstorm early can affect ANSP greatly, which carry large amounts of particulate N, P into the water.While in different time scales, effect of precipitation on ANSP in TGR area is mainly concentrated in summer and autumn, when which the scope and extent of pollutants N, P in runoff is obviously higher than that of the spring season.P value of slope in AR model reaches the significant level.There is a positive correlation between slope and pollutant emission rate, which means the greater the farmland slope is, the bigger nutrient loss in the soil is, and the degree of pollution may be more serious.In the spatial distribution, there is a good corresponding relationship between the slope and the degree of ANSP.The slope of which the periphery of the hinderland and along the Yangtze River region of the hinderland in the TGR area of Chongqing section is steeper, and the intensity of soil erosion in farmland is greater.(4)The factor“fertilizer” has the largest impact on agricultural ANSP in the TGR area of Chongqing section, which is the main source of pollution; the two factors “type of land use”and “breeding”are significant sources of pollution; the impact factor “rural environment”on agricultural NPSP in the TGR area of Chongqing section is negatively correlated.(5)The factor“fertilizer”is an important part of ANSP.The use of pesticides and fertilizers directly affects the production of pollutants, which enrich the nutrients in the soil.Otherwise unreasonable cultivation and fertilization lead to TN and TP in the soil retaining time longer.The factor“fertilizer”has the greatest impact on the periphery of the hinderland and along the Yangtze River region of the hinderland in the TGR area, in which have the high level of the unit area of pesticide and fertilizer and TN and TP have the large amount of pollution.The factor“fertilizer”has greater impact on the central of the TGR area, while the core area of the city uses the least amount of fertilizer.There is a strong positive correlation between the factor“breeding”and pollutant TP,TN and COD emission intensity.A lot of waste into water lead to eutrophication. The factor“breeding”has the greatest impact on the Kaixian County, Yunyang County and Wanzhou County, and greater impact on the central of the TGR area such as Fengdu County and Fuling County, while the least impact on the urban area.The factor“type of land use”has the greatest impact on the parallel ridge valley region and the end of the TGR area, but the impact on the periphery of the hinderland and along the Yangtze River region of the hinderland in the TGR area is relatively small.The amount of the loss of nutrients is dry land> paddy field > forestland > grassland.With the rising proportion of cultivated land, the organic pollutants in the field emission rate is of larger growth rate, which the trend of ANSP may increase.With the rising proportion of forestland, it can be certain inhibitory action to the emission rate of pollutants.The factor“rural environment”has the greatest impact on the emission rate of pollutants COD and BOD5.The better rural environment is, the smaller domestic garbage and domestic sewage emissions is, which it can be certain inhibitory action to the emission rate of pollutants.The factor“rural environment”has the greatest impact on the Kaixian County, Wanzhou County and Jiangjin County, while the least impact on the urban area.(6)Impact of the driving factors in region on the discharge amounts of COD and BOD5 is greater than that of driving factors in the adjacent region, while impact of the diffusion factors in the adjacent region on the discharge amounts of TN and TP is extremely important.