| With the rapid urbanization,and economical and social development in Pearl River Delta region,some organic pollutants were released into groundwater body,posing the great challenges to groundwater security.Therefore,it is necessary to reveal the pollution characteristics of organic compounds in groundwater at Pearl River Delta,and evaluate its environmental impact and vulnerability.In the current paper,a typical area of the Pearl River Delta was used as a representative to investigate the distribution characteristics,evolution mechanism of organic pollutants in groundwater.The migration and transformation mechanism of the characteristic organic pollutants in water-soil system was analyzed in combination with the static experiment.Subsequently,a quantitative evaluation method for the pollution source of typical organic pollutants in groundwater was established.Coupling with the migration and transformation analytical model,and vulnerability assessment model,the distribution characteristics,health risk,migration prediction and vulnerability of organic pollutants in the study areas of groundwater were comprehensively evaluated.The findings would be utilized as the scientific evidence and technical approaches for the local governments to perform groundwater organic pollution prevention and control.The primary findings and insights of the current paper are as follows.1)The analysis of groundwater samples in the study area was optimized.The methods could be used to detect several kinds of organic pollutants.The purifying and trapping gas chromatography-mass spectrometry,high performance liquid chromatography-tandem mass spectrometry and solid-phase extraction methods were used to detect 53 kinds of typical organic pollutants?halogenated hydrocarbons,polyalkane aromatics,benzene homologues,pharmaceutical and personal care products?in groundwater.2)The distribution of groundwater organic pollutants in groundwater showed that 22organic pollutants in the groundwater were detected?5 halogenated hydrocarbons,6polyalkane aromatics,7 benzene homologues,4 pharmaceutical and personal care products?.The potential hazard index and weighted scoring method were used to screen the groundwater organic pollutants in the study areas.The results showed that the priority pollutants in the studied area were benzene,naphthalene and chloroform,respectively.3)For the carcinogenic risk of characteristic organic pollutants in study area,it was found that the contribution of chloroform was greater than that of benzene.Among the 37sampling points,the carcinogenic risk of chloroform in 4 sampling sites was in an unacceptable range,however,the occurrence probability of carcinogenic risk was less than14%,while the distribution of risk values mainly ranged at 7.52×10-9 to 1.52×10-7.The certainty level was 54.43%.As for benzene,its carcinogenic risk was in an acceptable range,the probability of carcinogenic risk,risk distribution and certainty level were less than 6%,6.88×10-92.92×10-8 and 52.08%,respectively.Moreover,the study found that the risk of respiratory inhalation was the primary pathway for carcinogenic and non-carcinogenic risks to the overall risk among three pathways?drinking water intake,skin contact and respiratory inhalation?.Regarding to carcinogenic risk,the carcinogenic risk caused by respiratory pathway accounted for 90.19%of the total carcinogenic risk arising from the three routes of exposure,while the non-carcinogenic risk caused by respiratory pathway accounted for88.81%of the total non-carcinogenic risk.4)The adsorption and biodegradation characteristics of the typical organic pollutants under typical conditions and in different media were studied.The migration process of these typical organic pollutants,including benzene,naphthalene and chloroform,was evaluated in unsaturated zone by using HYDRUS-1D model.Subsequently,the prediction model of the source pollution in the study area was established.It was found that the main source of organic pollution risk of groundwater in the area was dotted and striped distribution,and the contaminative effects of characteristic pollutants benzene,naphthalene and chloroform in the study area were concentrated in south area.In addition,due to the distribution of gas stations and chemical enterprise in the study area,organic contaminated areas were also scattered in northwest area and midland.5)The nature vulnerability and environmental impact characteristics of the organic pollution process in study area were revealed.The assessment model was established and used to assess the organic pollution vulnerability of regional groundwater in the study area.The results showed that the vulnerability of shallow groundwater pollution in study area was at the moderate level due to the shallow groundwater level,the rapid urbanization and the increase in health risk posed by organic pollution.The results showed that the vulnerability assessment of south area,a petrochemical industry and chemical storage area,is a strong risk vulnerability,and northwest area was also under the high risk,whereas,northeast area was the low risk areas. |
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