Comparison of trace element concentrations in ambient air of industrial and residential areas in Tehran city.

Tehran is densely populated possessing unhealthy and polluted air. There are 22 municipality districts in Tehran, and considerable numbers of industries are located within each district. Due to adverse environmental and health effects of trace elements in urban air, this study has been carried out to measure and compare concentration of trace elements including Ag, As, Br, Ce, Co, Cr, Cs, Cu, Mn, Hf, La, Sb, Sc, Sm, Th, and Zn in industrial (district 21) and residential (district 22) areas. For this purpose, total suspended particles were collected in two different time intervals in the year 2008. As a result, maximum and minimum concentrations in residential area associated with Mn (2.9 μg/m(3)) and Hf (2.92 × 10(-4) μg/m(3)), respectively. Also, in industrial sites, these concentrations are higher for Mn (4.79 × 10(-1) μg/m(3)) and Hf (6.65 × 10(-4) μg/m(3)). The concentrations of Mn (2.07 μg/m(3)) and Hf (7.46 × 10(-4) μg/m(3)) in traffic zone are close to residential values. General, concentrations of Ce, Co, Cs, La, Sc, Sm, Th, Br, and Hf in industrial area were higher than in residential area. The source of these elements in Tehran's air is mainly anthropogenic. According to the achieved results, the concentration levels of As, Cr, and Zn were close together in both residential and industrial zones. Therefore, these elements could have been originated from natural sources. Also, results show that levels of Ag, Mn, Sb, and Cu in residential area were higher than in industrial area. Finally, obtained data indicated that the trends of average concentration of trace elements in industrial area (from low to high) follow as Hf<Cs<Sm<Th<La<Ce<Sc<Co<Ag<As<Sb<Cr<Br<Zn<Cu<Mn and, in residential area, are in order of Hf<Cs<La<Th<Ce<Sc<Sm<Co<As<Ag<Br<Sb<Cr<Zn<Cu<Mn.