Study On Groundwater Environmental Risk Assessment In "Red Bed" Area Of Sichuan Province

Landfill is the main final disposal method of domestic waste in China for a long time.Due to the influence of design specifications,impervious integrity and systematic operation and maintenance of landfills,the environmental problem of landfill leachate entering groundwater system is widespread,which causes incalculable harm to the health of residents with close groundwater around landfills.Therefore,a two-level probabilistic risk assessment model based on groundwater environmental pollution risk and human health hazard degree is constructed in this study.Typical landfills are selected for evaluation and the evaluation system is checked.At the same time,it designs a targeted treatment scheme for the domestic waste landfill in A County,which has a high risk of evaluation,and verifies the effectiveness of the scheme.(1)Based on the analysis of groundwater sampling around four red-bed domestic refuse landfills in Sichuan,the main pollution factors of groundwater environment in this area are total hardness,total soluble solids,sulfate,chloride,manganese,CODMn,nitrate,fluoride and ammonia nitrogen.(2)In the second-level probabilistic risk assessment model,the first-level assessment draws lessons from the traditional DRASTIC model and forms an improved pollution risk assessment model after considering the influence of engineering factors and pollution sources.Secondary assessment uses a four-step assessment model to describe the impact of pollution receptors on health risk assessment.The first-level evaluation model is constructed from three aspects:hydrogeological factors,engineering factors and pollution source factors.Qualitative description is used as index quantification method,and expert scoring method is used as weight determination method.Secondary evaluation combined with the results of first-grade evaluation and the status quo of the external environment and sensitive targets of the project,emphasized the characteristics of groundwater pollution hazards,and studied the toxicological risk through oral absorption.(3)The groundwater pollution risk of four selected landfills was evaluated comprehensively.The groundwater pollution risk of each landfill ranked from high to low:A County>B City=D Ctiy>C County,urban domestic refuse landfill.The risk degree of groundwater pollution in landfills is mainly influenced by engineering design and pollution status quo,which directly corresponds to that in informal landfills,the risk of groundwater pollution is greater than that in regular landfills,and in landfills with high groundwater pollution degree,the risk of groundwater pollution is greater than that in landfills with low pollution degree.(4)Contrast the groundwater recovery status between pollution control measures and non-pollution control measures.It is determined that the pollution control measures of"barrier technology combined with P+T technology" can effectively restore groundwater pollution in landfill sites.The specific performance is to reduce 65-80%of the groundwater environment recovery time and 54-72%of the groundwater pollution migration distance.This study provides a feasible method for effectively judging the degree of groundwater environment and human health hazards of domestic waste landfills in Sichuan red bed area,and provides scientific basis and technical support for risk management and control of landfills,as well as engineering reference for remediation of polluted landfills.