Trace metal concentrations in street dusts of Dhaka city, Bangladesh

Street dust samples were collected from differing areas (industrial—medium traffic density, commercial—high traffic density, and residential 1 and 2—low traffic density) in Dhaka City, Bangladesh, and their major oxide and trace element compositions were determined. The results show significant concentrations of Pb, Zn, Cu, Ni, and Cr in the Dhaka dusts, and some variations among the four sample groups. The samples in the commercial area had Pb concentrations two- to seven-fold those of the industrial and residential areas. Contents of Zn, Cu, Ni, and Cr in the industrial areas were greater than those in the commercial and residential areas. Levels of Pb, Cu, Ni, and Cr exceeded the maximum permissible limits for common soil. Increases in these anthropogenic trace metals in the surface environment can most likely be attributed to rapid urbanization and industrialization and increased vehicle emissions to the atmosphere. Elevated Zn concentrations in an industrial area can be ascribed to discharges of industrial activities, while elevated Zn abundances in commercial areas probably originate from traffic sources. The street dusts contaminated with Cu, Ni, and Cr occur mainly in industrial areas. However, Pb contamination in the Dhaka dusts is probably caused by Pb particles from vehicle emissions.