The lichen, Rizocarpon geographicum (L.) DC, grown on walls and roofs along the main streets in Amman city-Jordan, was used as a bioindicator for atmospheric pollution. The samples were collected from three areas representing high traffic, residential, and remote sites. The results of heavy metals concentration (Zn, Cu, Pb, Cd and Co) showed clear variations between the investigated sites comparedto that of the remote site. The highest concentrations occurred at the busy traffic sites and the lowest at the remote site. Peak concentrations of zinc (1206 μg g-1), copper (255 μg g-1), lead (400 μg g-1), cadmium (1.8 μg g-1) and cobalt (4.1 μg g-1) were observed at the city center of Amman that characterized busy road traffic. The heavy metal concentrations of lichens at Amman city were found to be at the upper limit values reported in the literature for temperate countries. Furthermore, lichens were found to be comparable to dust deposits and tree bark in terms of heavy metals content for the metropolitan area.
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