Contamination Characteristics And Health Risk Assessment Of Heavy Metals In Urban Dusts Of Hefei City

Five metals Cu, Zn, Pb, Cr and Cd in urban dusts of Hefei Citywere taken to be the research object in this paper. Fifth-two samplingpoints were selected and set in six land-use types, that is, commercialarea, residential area, industrial area, traffic area, educational area aswell as public landscapes and city squares. Correspondingly, fifth-twosamples were collected from above sites and contents of Cu, Zn, Pb, Cr,Cd and organic matter were measured. And then, the distributioncharacteristics, pollution degree and health risk of the five heavy metalswere investigated and evaluated. The results can be summarized asfollows:(1) Based on the AcrGIS software, the Kriging interpolation for Cu,Zn, Pb, Cr and Cd contents were conducted and corresponding distribution maps were drawn up. The results showed that the contentsof Cu and Cr decreased from city center to outside; the concentration ofZn was high in the east and west of the city, but low in the middle; andthe regularity of Cd distribution was not very obvious.(2) The correlation analysis showed that there were remarkablecorrelations between Pb and Cu, Zn, Cd and organic matter. Accordingto cluster analysis, six kinds of pollutants were divided into threecategories, including Pb, organic matter, Cu and Cd for the first category,Cr for the second category, and Zn for the third category. Moreover,fifth-two sampling points were classified into six categories. By usingfactor analysis, four principal component factors were extracted. Inaccordance with the rotated factor loadings, it was preliminarilydeduced that Pb and Cd contents were mainly affected by buildingdecoration activities, Zn and Pb by automotive vehicle, Cu by domesticand industrial wastes, and Cr by metal plating products in the urbandusts of Hefei. The contribution rates of four factors to each heavymetal can be further obtained by multiple linear regression of absolute principal scores.(3) According to the Nemerow single index, the urban dust of Hefeiwas polluted seriously by Cu, Zn, Pb, Cr and Cd (especially Zn and Cd).From Nemerow synthetic pollution values, the pollution degree was inthe decreasing order: public landscapes and city squares＞commercialarea＞educational area＞industrial area＞residential area＞traffic area.The Geoaccumulation index evaluation results also illustrated that theurban dust was polluted by the five heavy metals, with the pollutiondegree in the order: Cd＞Zn＞Pb＞Cu＞Cr.(4) In consideration of the uncertainties of health risk assessmentsystem, the assessment models based on trapezoidal fuzzy numbers weredeveloped to evaluate human health risks of heavy metals, as well as adiscrimination technique and assessment standards were proposed forcancer risks, which were used to assess the health risk of the heavymetals in urban dusts of Hefei City. In addition, considering thestochastic characteristics of health risk assessment system, the heavymetal contaminations of Cu, Zn, Pb, Cr and Cd in urban dusts were modeled by using Monte-Carlo approach and then health riskassessment was carried out. Traditional certain study results showed thatthe non-carcinogenic risk of children was significantly higher than thatof adults; non-carcinogenic risk of each function area was in thedecreasing order: industrial area＞public landscapes and city squares＞commercial area＞educational area＞residential area＞traffic area;non-carcinogenic risk of each metal was in the order of Pb＞Cr＞Zn＞Cd＞Cu. Generally, Cr and Cd have very low carcinogenic risk tohuman health.