Comparative assessment of heavy metals changes in the ambient air of two different zones of Tabriz City, Iran

Tabriz is a large and industrial city in the north west of Iran which suffers from severe air pollution due to being surrounded by mountains. Considering lack of official reports about the levels of heavy metals in Tabriz air, two zones of the city were selected for measurement of heavy metals in the air of this city. One of the two zones was located in a very heavy traffic zone of the city center, while the other was situated in a zone with relatively low levels of pollution. Three metals of lead, cadmium, and mercury were measured in these two zones. Among the three measured metals, lead with a concentration of 662 ng m^-3 had the highest concentration, followed by cadmium and mercury with concentrations of 92 and 8 ng m^-3 respectively. The concentrations of lead and cadmium in cold seasons were 30-50% greater than in warm seasons, whereas no significant correlation was observed between the concentration of mercury and the ambient temperature. No significant difference was observed between the concentrations of these metals in the two sampling sites; the levels of lead in winter in the city center were 20% greater than that in the countryside.