Distribution And Health Risk Assessment Of Organic Pollutants In Groundwater In The Receiving Area Of The South-to-North Water Transfer Project In Mihuaishun

The South-to-North Water Diversion Project has effectively alleviated the water resource crisis.However,there are many hazards of pollutants in the process of groundwater replenishment by South Water,and organic pollutants rank first among all pollutants.This article takes the receiving area of the South-to-North Water Transfer Project in Mihuaishun as the research object.A total of 30 sets of water samples were collected in dry season,wet season and median water period.Piper diagram and multivariate statistical methods were used to explore the hydraulic connection of the study area,and 56 kinds of VOCs,106 kinds of SVOCs and 82 kinds of pesticides were selected as the target pollutants.Based on the Gis platform and GUS classification,the pollution distribution characteristics and influencing factors were explored,and the US EPA health risk model was used to evaluate the health risk of target pollutants in groundwater.The results of this study have identified the organic pollutants risks of groundwater and provided technical support for groundwater risk assessment and pollution prevention and control.The main research results are as follows:Water chemistry analysis showed:The central area of the groundwater funnel was strongly affected by the replenishment of South Water.The water chemistry type changed from HCO₃-Ca·Na·Mg type to the same HCO₃-Ca·Mg type as South Water,and the salinity level changed from550 mg/L to 200 mg/L.The study area can be divided into three categories according to different water chemistry characteristics.Category A includes South water and groundwater in the central of the funnel.TDS ranges from 141 mg/L to 282 mg/L.Category B is mainly reclaimed water with high TDS characteristics,and the range is from 664 mg/L to 1080 mg/L.Category C mainly includes groundwater downstream of the wastewater treatment plant.TDS ranges from 460 mg/L to 772 mg/L.The clustering results showed obvious spatial distribution characteristics.The result of factor analysis showed that the groundwater quality in the study area is mainly affected by the replenishment and evaporation of reclaimed water,which can explain 87%of the water chemistry data.The spatio-temporal distribution of organic pollutants:Organic pollutants in the 30 groups of samples were widely detected in the study area,and the 242 organic pollutants analyzed and tested were respectively detected 43,49 and 58 in dry season,wet season and median water period.Spatially,the total concentration of organic pollution exhibited a decreasing law along the flow of groundwater.At the center of the groundwater funnel,with the replenishment of South Water,organic pollutants gradually accumulated here,and the wet season dad the most obvious characteristics.The GUS classification proved that the detection of organic pollutant was closely related to DT₅₀ and Koc.The detection rate of 71 organics was less than 20%,of which 18 had higher leachability and 33 had lower leachability;among the 18 organic pollutants with a detection rate of more than 20%,6 kinds had higher leachability and 3 kinds had lower leachability.Indicating that the higher leachability of organic pollutants,the easier it is to enter the groundwater environment.Health risk assessment indicated:Female children showed the most sensitive exposure characteristics,and age had a greater impact on risk than gender.The total carcinogenic risk showed a higher risk in the wet season.The carcinogenic risks of organic pollutants detected were all lower than the maximum acceptable risk of 1.0×10^-4 stipulated by US EPA.