Pollution Characteristics,environmental And Health Risk Assessment Of Heavy Metals In Street Dust Of Beijing Urban Areas

Urban street dust is composed of a variety of pollutants and formed after the long-term accumulation of atmospheric particles and surface dust due to the influence of long-term external forces.In this study,urban dust samples along five Ring Road of Beijing were collected to assess the pollution degrees of heavy metals pollutants(Zn,Cd,Pb and Cu)and better understand their mobility and potential toxicity to the environment based on the speciation analysis by the voltammetry method.The modified BCR sequential extraction method is applied to measure the four kinds of chemical forms of the metals—weak acid extraction state(F1),Reducible state(F2),Oxidizable state(F3),Residual state(F4)The spatial distribution of the four chemical forms of heavy metals and their total concentrations are studied and the potential sources and the health risks of the four heavy metals were also discussed based on the Geo-accumulation Index,Potential Ecological Pollution Index and EPA Health Risk Model.The results are as follows:(1)The pH of the street dust in Beijing urban area is alkaline on the whole,and the particle size is dominated by the sand.(2)The percentage of the heavy metals speciation varied in the following order:F2>F1>F4>F3 for Zn and Cd;F2>F4>F3>F1 for Pb and Cu.The mean concentrations of Zn,Cd,Pb and Cu in the dust samples were all higher than those in the soil background of Beijing.(3)The Kriging interpolation method of Arc GIS was used to analyze the spatial distribution of heavy metals in the urban street dust of Beijing.The high value areas of the four heavy metals in the urban street dust of Beijing were mainly concentrated within the Fourth Ring Road of Beijing,with a sporadic distribution of these metals in the Fifth Ring Road.(4)Correlation analysis,cluster analysis and principal component analysis were used to study the potential sources of heavy metals.The results showed that Pb and Cu might be mainly related to traffic activities,while the sources of Cd were different from Zn,Pb and Cu.(5)Pb is moderately enriched,while Zn,Cd and Cu are significantly enriched based on the enrichment factor.Based on Geoaccumulation Index Method,Cu in a moderate to heavy pollution,while Zn and Cd in a moderate pollution,and Pb in a light pollution.Zn,Pb and Cu in a low risk and Cd in a relatively high risk based on the Potential Ecological Risk Index Method.The total potential ecological risk coefficient(RI)of the four heavy metals in a medium level.The result of EPA Health Risk Model suggested that hand-mouth exposure is the main route of heavy metals of street dust entering human body.Compared with adults,children are more susceptible to heavy metals.