CONCENTRATION DISTRIBUTION AND COMPOSITION OF HEAVY METALS IN STREET DUST FROM SMALL TOWNS IN YONGCHUAN, CHONGQING

摘要

To examine the status and risk of heavy metal pollution in street dust in small towns, the distribution of several heavy metals (e.g., Cd, Cu, Ni, Pb, Zn, Mn and Fe) in small towns of Yongchuan District, Chongqing City, was investigated. The results revealed that the total concentrations of heavy metals in street dust in small towns were lower than in large cities overall (e.g., concentrations of Cd, Ni, Mn, Zn, Pb, Cu and Fe were in the range of 2.97-8.44 μg/g, 22.87-92.30μg/g, 275.84-1502.63 (μg/g, 47.89-439.72 μg/g, 39.81-133.30 μg/g, 12.57-241.52 μg/g, and 10485.07-26845.35 μg/g, respectively). However, the total concentrations were still higher than background values of soil in China, especially for Cd (e.g., 30.6-87 times higher than the background value). Fe and Cu were in a low bioavailability, and Cd was found to be biologically active almost in every site according to the modified Community Bureau of Reference (BCR) sequential extraction procedure. Meanwhile, Risk Assessment Code (RAC) was used to evaluate release risk of heavy metals, which revealed that Fe and Cu had no or low risk to the environment, while the release risk of Cd was medium or high in all monitored sites. In addition, we also analyzed the release risk of other monitored heavy metals.