| The eastern part of the city is located in the northern fissure karst area of our country,the CT contents of 24 public water supply wells and 20 facilities self-provided wells in the area more than the limits of life and drinking health standard?0.002 mg/L?,CT pollution is a serious problem.At present,it is urgent to find the pollution sources and find out the solutions.In this work,through identify the region hydrogeological condition,master the CT pollution history and current situation to establish the model of groundwater flow model and solute transport model.MODPATH was applied to perform reverse particle tracing to delineate the capture zones of CT pollution;Combined with the history use of CT,the range of suspected companies was delineated.At the same time,the prediction and evaluation of health risk for CT pollutants in the study area was quantitatively linked to human health.The results can assess and predict the health risk of CT pollutants and provide scientific basis and technical support for the treatment and repair of CT pollution areas as well.The results show that the range of pollution sources in the study area is probably:steel plant B in the southwest,machine tool plant in the middle,plastic plant,petrochemical plant,steel plant A and fertilizer plant in the northeast.CT in groundwater can enter the body through outdoor respiratory inhalation,indoor respiratory inhalation and drinking water.The majority of the carcinogenic risk caused by groundwater in the study area exceeds the level of acceptable carcinogenic risk(10-6 orders of magnitude),and the carcinogenic risk is generally high.Among them,the maximum carcinogenic risk value for subarea 12 is 1.09E-04,and the minimum carcinogenic risk value for subdivisions 1 and 2 is 0.The majority of the hazard index is less than the acceptable hazard quotient?the value is 1?.Only four subdivisions,including subdivisions 12,19,20,and 23 have a hazard index greater than 1,and the overall carbon tetrachloride risk in the study area is non-carcinogenic.The degree of harm is not high.The order of the harms caused by three pathways is as follows:Inhalation of outdoor air pathways<Inhalation of indoor air pathways<Drinking water.During the forecast period?10 years,20 years,and 30 years?,the total hazard index of the subdivisions in the study area was less than 1,indicating that the non-carcinogenic effects of the population were lower.The cancer risk in the district has also shown a slowing trend.The number of areas with serious carcinogenic risk(>10-5)decreased from 5 in the current situation to 2,2 and 1,respectively;the number of areas with middle serious carcinogenic risk(>10-6)decreased from the current 12 in the current situation to 8,7 and 8,respectively.The number of areas(<10-6)with low carcinogenic risk increased from 11 in the current status to 18,19,and 19,respectively.With the increase of time,pollutants migrated under the effect of convection diffusion,the effect of pollution and the overall concentration of pollutants gradually decreased.In addition,the degree of carcinogenic risk in the area was slowing down,and the level of acceptable levels of carcinogenic risk increased gradually. |
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