西安市城市道路灰尘重金属污染及健康风险评价

Heavy metal pollution of the urban street dust and health risk assessment in Xi'an

在西安市典型旅游区、居民文教区、商业区和工业区内选择具有不同车流量的12条道路作为路面灰尘采样区域,于2013年10—11月采集路面灰尘样本72个,测试灰尘中重金属Pb、Zn、Cu、V、Ba、Cr、Cd、Ni、As的质量比,统计分析灰尘重金属污染空间分异特征,并应用美国EPA人体暴露风险评价方法评价其健康风险。结果表明:西安市道路灰尘重金属明显富集,除V外,Pb、Zn、Cu、Ba、Cr、Cd、Ni、As质量比分别是陕西土壤背景值的5.59、4.02、2.37、3.64、2.21、93.83、1.08和7.09倍,Pb、Zn、Ni质量比呈工业区最高、旅游区最小、工业区明显高于其他功能区的空间布局,Cr和Cd质量比各功能区差别不大且呈宽幅离散,居民文教区Cu、As质量比较其他功能区高,旅游区V质量比明显高于其他功能区;手-口接触摄入是路面灰尘风险暴露的主要途径,各类重金属非致癌风险从高到低为As、Cr、Pb、Ba、Cd、V、Ni、Cu、Zn,手-口接触摄入、呼吸吸入和皮肤接触3种途径对儿童和成人产生的非致癌总风险分别为2.75和0.372,灰尘暴露导致的儿童非致癌健康风险不容忽视,As、Cr、Pb、Ba是危害最大的污染物;Cr、Cd、Ni、As的致癌暴露风险从高到低为Cr、As、Cd、Ni,单一重金属的致癌风险及4种重金属总致癌风险均低于致癌风险量级水平。

The given paper is engaged in a study of heavy metal pollution of the urban street dust and the health risk assessment in Xi＇an City. As a matter of fact,long-term exposure to the dust environment may lead to the chronic disease through ways of inhalation,ingestion,and dermatitis. Some kinds of heavy metals,such as Cr,Cd,Ni,and As,are also likely to cause carcinogenic health hazards to the human sufferers. In order to evaluate the potential health risk of street dust in Xi＇an,the authors of the given paper has conducted an extensive survey in the urban areas of the city. For the purpose of our investigation,we have collected 72 dust samples from the 12 urban streets of Xi＇an with different traffic density in the different functional zones from Oct. to Nov. in 2013. The analysis of the concentrations of Pb,Zn,Cu,V,Ba,Cr,Cd,Ni,and As,let us determine and identify the spatial distribution density of such heavy metal pollutants in the street dust. In our work,we have adopted the human health risk assessment method established by USEPA in evaluating the potential health risk caused by the aforementioned heavy metals in the street dust. The results of our survey demonstrate that the said heavy metal pollutants contribute to the street dust composure significantly except for V. The average content rates of Pb,Zn,Cu,Ba,Cr,Cd,Ni,As in the street dust account for 5. 59,4. 02,2. 37,3. 64,2. 21,93. 83,1. 08 and 7. 09 times respectively higherthan those in the background soil elements of Shaanxi Province.More specifically speaking,the highest concentrations can be found of Pb,Zn,Ni in the street dust in industrial zones,whereas the lowest in the tourist spots but much higher in the industrial zones than those in other areas. Nevertheless,the concentrations of Cr and Cd are widely distributed in no difference with the area classification.Furthermore,the concentrations of Cu and As are highest in the residential and educational zones,while V is the highest in tourist areas. As for the exposure ways,ingestion tends to be the most obvious manner. As to the non-carcinogenic risk of exposure,the concentration rates can be shown in a descending order as is shown as follows：As Cr Pb Ba Cd V Ni Cu Zn. The total non-carcinogenic risk harmful rates for children and adults caused by the dust exposure may account for 2. 75 and 0. 372 respectively mainly via the three pathways,that is,ingestion,dermatitis and inhalation,which suggests rather higher health risk for children. In spite of this,As,Cr,Pb and Ba have to be regarded as the most harmful pollutants that may lead to non-cancer health risk,though the exposure to the cancer risk may include only Cr As Cd Ni. What is more,the risks of single heavy metal or all the inclusive should be considered lower than the average risk thresholds and therefore may not result in carcinogenic health hazards to human sufferers.