Groundwater Pollution Identification And Risk Assessment Of Riverside Source Field In Wulie River Basin

The riverside source field has sufficient groundwater and the water quality is good.It is widely used in the water supply of northern China.Groundwater pollution is very difficult to handle,that makes the prevention of groundwater pollution is more important than governance.Therefore,the accurate assessment of groundwater pollution risk is the key to maintain good water supply in the water source area,which is of great significance for the prevention and control of groundwater pollution in water sources.Based on the idea of the whole process control including pollution source,pollution route and groundwater risk,the pollution sources of groundwater in Wulie River Basin is identified.Based on the result of the pollution sources identification,the simulation of the solute transport of the characteristic pollutants in the groundwater is carried out,and the health risk of the water source is evaluated according to the simulation results.The results of the research are as follows:(1)According to the site investigation and data collection of riverside source field in the Wulie River Basin,the main sources of pollution in the study area are surface water,informal waste dump,industrial pollution sources,and livestock and poultry farms.Among them,because the shallow groundwater is the main source of drinking water,the surface water quality has great influence on the groundwater quality.The water quality of the surface water and the groundwater in the riverside source field was detected and analyzed.The quality of the surface water in the riverside source field was good.At present,there is no pollution to the groundwater in the riverside source field.Through the correlation analysis of surface water and groundwater quality in recent years,it is found that the overall change trend of p H value,copper,zinc,volatile phenol,permanganate index,ammonia nitrogen,anionic synthetic detergent,fluoride,total cyanide,total arsenic,selenium,cadmium,six valence chromium and lead are the same.Among them,the concentration of permanganate index and ammonia nitrogen change obviously.It is proved that the quality of groundwater is closely related to the quality of surface water.(2)The data of hydrogeology and other data of the groundwater of riverside source field in the Wulie River Basin were extracted and arranged by GIS,and the groundwater flow model of the water source was established by inserting into the MODFLOW module of the GMS.Then,by using the MODPATH module and GIS in GMS,the path relationship between the water intake well and riverside source field,including informal waste dump,industrial pollution sources,and livestock and poultry farms was traced and simulated.According to the analytic hierarchy process(AHP),the harmfulness of the source of water source was sorted,and the risk ranking results were as follows: the irregular garbage dump > small factory > livestock farm,and the irregular garbage yard in the northeast of the water source area had the greatest influence on the water quality.(3)Based on the above research results,the ammonia,mercury,fluoride and volatile phenol are selected as the characteristic pollutants in informal waste dump,and The MT3 D module in GMS was used to simulate the solute transport for 20 years.According to the simulation results,pollutants in groundwater of informal waste dump gradually spread to the water intake well of riverside source field after 10 years of migration.Due to the long-term large-scale exploitation of the water intake well,a groundwater level funnel was formed,which caused the pollutants to accumulate at water intake well and the concentration gradually increased,which affected the water quality of the water intake well.Subsequently,the pollutants continue to spread southward along with the flow of water,so that the concentration of pollutants at water intake well does not continue to increase.From the 15 th year of the simulation to the end of the simulation,the concentration of pollutants at the intake well was in a stable state of fluctuation.Regarding the groundwater level falling funnel appearing in the water intake well,the following measures are recommended,including the rational development of groundwater resources,control of the amount of exploitation,balance of water recovery,artificial recharge,development of water-saving industries and agriculture,and increasing of the depth of exploitation.(4)Based on the numerical simulation results,the health risk assessment model from the United States is used to predict the health risk of the riverside source field in the future.The primary concern is the damage to the human body through the diet of pollutants in the study area.From the calculation results of the model,it can be seen that in the next 20 years,the adult health risk value and child risk value in the study area are less than the maximum acceptable risk level(5.0×10-5 a-1)of human health,and are within the acceptable range,indicating that the environmental health risk of riverside source field of Wulie River Basin is good.It is recommended to strengthen the monitoring of groundwater in the informal waste dump,or to clean up and relocate it,or to establish a regular landfill with anti-seepage treatment so as to avoid the continued infiltration of pollutants and cause serious pollution of groundwater and reduce the potential safety hazards of the riverside source field.