Influence Of Comprehensive Agricultural Development Project On Non-point Source Pollution In Chengdu Plain Area

Agricultural non-point source pollution in small watershed is the main source of water pollution,and its pollution control has gradually become an important measure to control agricultural non-point source pollution.Based on Sichuan Province’s Project of Agricultural Comprehensive Development of Yangtze River Green Ecological Corridor with Loan from Asian Development Bank,the impact of the project construction in Anzhou District on agricultural non-point source pollution in a small watershed in Anluo Village was studied.The study area is located in Chengdu Plain,which is an important grain production area with rapid urbanization and a fragile ecological environment in the upper reaches of the Yangtze River.The Chengdu Plain has dense water systems and complex hydrological conditions,and the harmful substances lost from agricultural production enter the water body quickly and are difficult to control.Through a combination of household surveys and data collection,estimate the agricultural non-point source pollution load by Johns output coefficient model;analyze and evaluate the soil nutrient and soil risk by Nemerow index method;evaluate the water environment quality by comprehensive index evaluation method;calculate the soil erosion by sand pool method,at the same time,after the project before a total of three stages of data results,analyze the impact of the project,put forward targeted management measures,the hierarchical analysis of research area non-point source pollution system evaluation,in order to Chengdu plain agricultural comprehensive development basin non-point source pollution assessment to provide effective reference,to a certain extent,make up for the deficiency of the research.The main study conclusions are summarized as follows:(1)The main sources of agricultural non-point source pollution from 2020 in the study area to 2022 are chemical fertilizer pollution and livestock and poultry breeding,and the equal standard discharge are 42.01×10~6m~3,29.19×10~6m~3and 22.76×10~6m~3respectively.The main reason for the decreasing pollution is the decrease of fertilizer pollution in the study area after the ADB project,and the construction of slope ladder is also beneficial to the soil conservation and fertilizer conservation of cultivated land.(2)The water quality in the study area was poor in 2020,improved in 2021,and deteriorated again in the small basin in 2022,mainly because the monitoring points in the basin are located near the cultivated land.After the completion of the project,the increased pollution and water quality in the basin.However,The export water quality of small watershed is still Grade II,and compared with 2020,the export water quality has been significantly improved,indicating that the projects in the basin have a great improvement effect on the pollution of small watershed and have a positive impact on the environmental quality..(3)The soil in the study area is all silty loam,and the slope and ladder project will lead to the increase of soil sand grains and the decrease of powder grains.In terms of soil nutrients,the composite index of soil fertility at each monitoring point decreased in 2022,mainly due to the low nutrient content and heavy metals and pesticide residues in the past three years,indicating the lower soil quality and risk in the study area.(4)The amount of soil and water loss in the study area was 25 t in 2021 and 13.26 t in 2022,a decrease of 46.95%,partly due to the decrease of rainfall intensity and the fact of the slope to the soil.(5)Taking the regional non-point source pollution evaluation index system as the target layer;planting industry pollution,livestock and poultry breeding pollution,rural life pollution,runoff pollution and water and soil environment pollution as the criterion layer;15 specific indicators as the index layer,and the non-point source pollution in the study area is analyzed before and after the construction.The scores from 2020 to 2022 were0.64,0.54 and 0.52,respectively.The results show that the initial pollution in the study area was relatively serious,and the environmental quality improved year by year after the implementation of the project,and the project had a positive effect on the improvement of environmental quality.