Identification And Assessment Of Surface Pollution Risk Sources After Groundwater Level Rise Due To Recharge Of South Water In Mi-Huai-shun Area

The Mi-Huai-Shun area is an important source of groundwater in Beijing.Longterm exploitation has formed a huge landing funnel.It is an important decision for Beijing to ensure the safety of water resources by using South-North Water Diversion to replenish it.In the process of the recovery of the South Water Replenishment level,it is of paramount importance to ensure the safety of groundwater quality.Therefore,it is of great significance to carry out pollution risk identification and assessment research to ensure the safety of groundwater recharge water quality.In this paper,based on the process of surface pollution sources releasing pollutants from the surface environment through the vadose zone and groundwater aquifer to the water source,a method system for surface pollution source risk identification and assessment was constructed.The main conclusions of the study are as follows:(1)Establishing a surface pollution source screening method system that combines the quantification of surface pollution source load,the reduction of pollutants in the aeration zone,the hazards of pollution sources reaching the groundwater surface,and the contaminants at the aquifer level.The system first considers the surface pollution source load and characterizes the reduction reaction of lithologic media in the aerated zone to pollutants.Based on the two factors influencing the surface source load and the transport of pollutants in the aerated zone and aquifer,and using groundwater The coupling of medium pollutant value and attribute is regarded as a hazard,and the time when the pollutant finally reaches the water source in the aquifer is regarded as a horizontal risk,which makes the identification method system of surface pollution sources with greater potential risk more scientific.(2)The quantitative grading of surface pollutant loads shows that in the highest coupled load area per unit area,surface pollution rivers,industrial beverage industry,and landfill pollution sources are the main sources of pollution,and industrial enterprises account for the highest proportion of pollution source types.The results of the comparative analysis of the hazards of pollution sources before and after replenishment show that the ranking of the hazards of pollution sources has changed and the hazard values of the same pollution sources have increased.Among them,the time for the pollutant level in the north to reach the water source is longer than that in the south.(3)The result of the risk source identification based on the reverse evaluation of the groundwater comprehensive pollution risk assessment before and after replenishment shows that the horizontal risk in the north of the water source is less than that in the south,and the horizontal risk in the west of the water source is greater than that in the east.The areas with higher risks are mainly concentrated in the sewage rivers of the Huaihe River and Chaobai River,flat agriculture,urban and rural residential areas,scattered point landfills,industrial enterprises and farms represented by beverages,food,printing,etc.,among which Surface drainage rivers,industrial enterprises,and landfills are key prevention and control areas.