Analysis of Heavy Metal Pollution in Road Dust of Tianjin Xiqing District

Dust samples were collected for the heavy metals pollution survey from Xiqing District in Tianjin, including forty-three sites of Outer-ring West Road, Jinlai Road, Gong No.1Road and Xiuchuan Road. After collecting and pre-treatment about road surface dust, particle size, pH and heavy metal content were also measured and analyzed. Results show that the distribution of road dust particles in Xiqing District is irregular, most of them are between 106 ~ 250 and the average diameter of low-grade road dust particles is larger than that of high-grade road dust particles. The collected road dust samples imply that it is alkaline. Heavy metal concentrations witness a downward trend with increasing dust particle size. The average content of heavy metals in road dust is listed in the sequence of Gong No.1Road, Outer-ring West Road, Jinlai Road, and Xiuchuan Road, and the order of heavy metals is: Zinc (Zn); Chromium (Cr); Copper (Cu); Lead (Pb); and Cadmium (Cd) which are higher than those in Tianjin Soil background values, especially Cadmium (Cd) and Lead (Pb) which are 10 times more. Those Heavy metals including Cadmium (Cd), Lead (Pb), Copper (Cu), Chromium (Cr), and Zinc (Zn) are mainly associated with anthropogenic activities, such as transportation and industrial emissions. The sources of heavy metal Cadmium (Cd) are complex and may result from the wear and tear of automobile tires, brakes and so on. The potential ecological risk index method is implemented to evaluate ecological risk of heavy metals in road dust which shows that the area for study is at slight ecological risk.