Pollution Characteristics And Monitoring Methods Of Groundwater Of The Uncontrolled Landfill Under The Surface Water And Groundwater Interaction

In order to propose the main technical methods for the investigation and monitoring of the uncontrolled landfills,this paper identified the characteristic pollutants and constructed a simulation system for the pollution process,based on the evaluation of the groundwater quality investigation of the uncontrolled landfills in Guangdong Province.This paper carried out laboratory physical simulations to investigate the migration and transformation of the characteristic pollutants,and combined numerical simulations to study the migration of the pollutants in the aquifer under the interaction between the surface water and groundwater.The main conclusions were as follows:（1）The characteristic pollutants of groundwater in the uncontrolled landfills were total hardness,total dissolved solids,sulfates,chlorides,fluoride,nitrates,ammonia nitrogen,iron,manganese,arsenic,lead,nickel,aluminum,thallium,permanganate index and total coliform bacteria,a total of 16 species.Among them,the five pollution indicators that were fluoride,lead,nickel,thallium and aluminum had obvious regional characteristics.（2）After the leakage of landfill leachate,the pollutants mainly migrated to the aquifer insulation floor where concentration accumulates in the direction of gravity,and further migrated downstream along the groundwater flow,and spread to the shallow groundwater after the intersection boundary between surface water and groundwater.The environmental investigation and assessment work should pay close attention to the deep groundwater.（3）The interaction between the surface water and groundwater prolonged the time for pollutants remained in the aquifer.The pollutants concentration increases from the initial value of 14.58 mg/L to the peak of 16.46 mg/L lasted 11 days,while it lasted 40 days under the influence of the interaction between the surface water and groundwater.The time for pollutants remained in the aquifer increased by 163.6%.（4）When the interaction between the surface water and groundwater changed periodically,the concentration of pollutants also fluctuates periodically.When the groundwater replenishes the surface water during the dry period,the concentration of pollutants in the groundwater showed a trend of shock reduction;When the surface water replenishes the groundwater during the flood period,the concentration of pollutants in the groundwater showed a trend of shock increase.Pollution range increased by about 122.6% in the flood period compared with that in the dry period.（5）This study determined the groundwater investigation and monitoring method for the uncontrolled landfill,including monitoring indicators,survey point location,sampling frequency and depth.The monitoring indicators included 16 Continuousmonitoring pollution indicators（characteristic pollution indicators）and 36 mandatory pollution indicators（groundwater pollution indicators detected）.After the groundwater in the uncontrolled landfill was polluted,the downstream pollution load of the groundwater was relatively heavy.Therefore,no less than 6 survey points were set up in the uncontrolled landfill,including 1 in upstream of the groundwater,1 on each side of the uncontrolled landfill,at least 2 in downstream of the groundwater,and 1 near the area of leachate collection and treatment device,combined with the technical specifications for environmental monitoring of groundwater.Groundwater samples were monitored densely after the flood period,and were sampled once a month,2months and 3 months after the end of the flood period,and once every quarter in other periods,at 0.5m above the groundwater diaphragm.