Quantitative Environmental Risk Assessment Of Cr-contaminated Sites And Study On The Effect Of Remediation Experiment

Heavy metal pollution is a very important source of current environmental issues. Because of the early extensive industrial production model, it resulted in severe environmental pollution in related industries, which heavy metal chromium contamination had become more prominent in industrial pollution. Preliminary investigation of chromium contaminatal site showed that chromium slag in history would cause serious pollution aroundthe soil,and the contaminated soilafter cleaning up chromium slag as contaminated sources still existed the risk of contamination for surrounding environment. Therefore, the chromium contaminated sites risk assessment and restoration work is one of the urgentto carry out currently undertaken.The chromium slag of Chongqing minfeng chemical plant had achieved a harmless utilization, but still there wasseriouschromium contamination. In this paper, studying on the contaminated sites,setting up 327 monitoring sites, collecting soil samples(including covering build slag) 1307, water samples 2. According analysismonitoring results, the total chromium content in monitoring sample was up to 81200 mg / kg, the highest content of hexavalent chromium was 1770 mg / kg.According to the relevant requirements of "Guidelines for the risk assessment of contaminated sites," the paper calculatd health risks in the human body of trivalent chromium and hexavalent chromium in different routes of exposure, and calculatd the site remediation target by the health riskmode. Obtain the following conclusions.①The carcinogenic risk of hexavalent chromium in surface soil by inhalation soil particles was 1.01E-04, was over than the acceptable level, and had the higher the risk. The non-carcinogenic risk hazard quotient of trivalent chromium in surface soil by oral intaken soil and skin contact with soil was only 0.17 and 0.004, did not exceed acceptable hazard quotient 1; The non-carcinogenic risk hazard quotient of hexavalent chromium by inhalation soil particles and oral intaken soil was 7.02 and 1.54, exceed acceptable hazard quotient 1; The non-carcinogenic risk hazard quotient of hexavalent chromium by skin contact with soil was 0.17;did not exceed acceptable hazard quotient 1; respectively, exceeding the acceptable hazard quotient value of 1; The hazard quotient of hexavalent chromium by washingwas 27.46,which was 27.46 times of hazard quotient,and had higher levels harmful to human health.② According to the actual situation of Chongqing minfeng chemical plant contaminated sites, taking into account the feasibility of restoration, and referring to "contaminated site risk assessment guidelines" to determine remediation target, it is proposed to set the remediation target of hexavalent chromium as 34.8mg / kg.③ The volume of Cr6 + contamination soil which concentration at34.8-200 mg / kg was 1,287,200 m3; The volume of Cr6 + contamination soil which concentration at 200-1000mg/kg was 1,171,800 m3; The volume of Cr6 + contamination soil which concentration over 1000mg/kg was 22,600m3. The total contaminated soil volume was 2,481,600m3. Coupled with the above surface play area contaminated construction waste about 13,400 m3, The totalvolume required to dispose of contaminationg soil was 2.495 million cubic meters with the suface building pollutants.④ On the basis of quantitative assessment, study the repair effectiveness of soil contaminated by chromium through leaching and curing experiments. For thedifferent levels contaminated by chromium pollution, selected different rehabilitation program.For heavily contaminated soils(> 1000 mg / kg); it can adopt in situ leaching technique to repair. By comparing the effects of different chemical leaching experiments, in view of Fe SO4 good reduction effect and lower cost price(about 1000 yuan /ton), and can be more than 80% Cr of the acid extractable converted into other forms, so as to effectively reduce Cr toxicity, in the actual repair work can choose Fe SO4 as the leaching agent. For the slightly contaminated soil(<1000mg/kg), solidification and stabilization techniques can be used to repair Through experimental analysis showed that it can effectively reduce the content of Cr in leachate with adding the new combination heavy metal curing agent. When increasing the amount of the agent, the curing effect will be significantly increased. When the amount of CCT03 + CCT01 was 6% + 10%, removal rate has been as high as 90%, and then add small changes in chemical curing effect.