| The urban land is more precious and the site changes more and more frequently with the acceleration of China's economy development and urbanization process.Most factories and enterprises in the downtown areas have been moved to the industrial concentration zones as planned,while the original industrial land is gradually become into residential or public land.The remaining pollutants of original factories may have serious effect on the soil and underground water,endangering human health.In view of this situation,contaminated site investigation and risk assessment is important for maintaining a safe reuse of site.In this paper,the contami nated site of original Chlor-alkali Plant use calcium carbide process to produce PVC,which intends to be transformed into residential land.In order to ensure the soil quality and population health in safe range,investigation of environmental status and health risk assessment of contaminated site was conducted based on the technique of "Guidelines for Risk Assessment of Contaminated Sites" and related standards which include "Soil Environmental Quality Evaluation Standards for Land Use in the Exhibition?provisional?","Screening Value of Environmental Risk Assessment for Site Soil","The Quality Standard of Groundwater".In addition,the concentration of typical pollutants from soil-groundwater was determined,in order to analyze the spatial distribution and their sources in contaminated site.The proposal of recommended target value provided technical support for the subsequent site remediation and management.The main conclusions were as follows:?1?The pollutants of nickel,mercury,copper,benzene,chloroform overstep the criterion of Soil Environmental Standard.The maximum exceeded multiple of mercury,benzene and chloroform was 23.8times,5.05 times,37.3times,respectively.In groundwater,the excessive pollutants include iron,chloride and volatile phenols?in terms of phenol?,with the maximum exceed multiple was 3.15 times,11.6times,35.4times,respectively.?2?There are typical spatial difference in the distribution of pollutants in the soil of the studied site,which is highly correlated with the chemical raw material storage,producing process and production region.In the soil samples,the monitoring concentration change of most points follow the tendency that contaminant concentration decrease with the increase of soil sampling depth.The appearance of individual abnormal points was due to artificial disturbance.Groundwater contamination was related to brine in receiving plant and sewage discharge.Moreover,the pollutant in the monitoring well which is located in the downstream groundwater exceeded the standard seriously because of the migration of groundwater runoff.?3?The results of health risk assessment showed that the carcinogenic risk of benzene,chloroform and the non-carcinogenic hazard quotient of mercury,benzene in soil beyond the acceptable level(carcinogenic risk ranges were 2.22×10-84.80×10-5 and 2.10×10-77.91×10-5;total hazard index ranges were 1.11×10-17.57×100 and 3.66×10-33.89×100).It is necessary to carry out soil remediation.Pollutants of groundwater in studied site have proven not to be detrimental for human health as the hazard index within the acceptable level.However,in consideration of some pollutants of groundwater beyond class ? of water environment quality standard,Groundwater in studied site was unsuited for drinking.?4?The results of health assessment show that pollutants of mercury,benzene,chloroform may cause harm to human health.On account of soil risk control target of carcinogenic and non-carcinogenic effect,standard limits of residential land in "Screening value of environmental risk assessment for site soil",finalize the remediation target values: mercury: 2.41 mg.kg-1,benzene: 0.02 mg.kg-1,chloroform: 0.035 mg.kg-1. |
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