Concentration of Selected Heavy Metals in Atmospheric Dust of Isfahan and Neighboring Metropolitan Areas

Atmospheric dust is an important source of heavy metals, particularly in urban environments. Heavy metals can easily attach to dust particles and be distributed in large areas. The objective of this study was to evaluate the status of major heavy metals in the atmospheric dust of Isfahan and adjacent cities. A total of 144 dust samples were taken during a period from August to December 2010 from Isfahan, Khomeynishahr, Falavarjan, Mobarake and Zarinshahr cities. Dust samples were extracted with HNO3 65% and the total concentration of metals including Pb, Zn, Cd, Cu, Ni, Co, Cr and Mn in the samples was measured by an atomic absorption spectrometer. The mean concentration of these metals was 223.5, 470.3, 3.5, 71.0, 82.0, 26.5, 24.4 and 426.3 mg kg-1, respectively. Results indicated that heavy metals concentration in any area was different depending on the source of pollution and it was much higher than the mean concentration of the corresponding heavy metal in soils. Besides, the highest deposition rate of all the heavy metals in this study was found in November-December period. This could be attributed to an increase in the use of heating systems and also to a temperature inversion event prevailed in the area. Atmospheric deposition seems to be an important pathway of heavy metals addition to soils. For example, it is responsible for 35-91% and 12-47% of Pb and Cd entering the soil in the area, respectively.