A STUDY OF AIR-POLLUTION WITH HEAVY-METALS IN THESSALONIKI CITY (GREECE) USING TREES AS BIOLOGICAL INDICATORS

The air pollution of the city of Thessaloniki was studied, using park trees as biomonitors. The species analyzed were Ligustrum japonicum, N erium oleander, Olea europea, Pinus brutia, Platanus orientalis, Popul us alba, Populus nigra, and Robinia pseudoacacia. Acid digestion of le af tissues and subsequent use of atomic absorption spectrometry was th e analytical methodology used for the determination of heavy metals (C u, Zn, and Pb). The concentration of heavy metals in the tree leaves d epended on the metal species as well as on the position of the tree in the city. The mean concentrations of Cu ranged between 5 and 10 mg kg (-1) dry weight, of Zn between 19 and 85 mg kg(-1) DW and of Pb betwee n <1.5 and 4.5 mg kg(-1) DW. In some cases, the effect of road junctio ns proved more significant than the traffic load for the contamination of leaves. Some differentiation was also observed between tree specie s. Old leaves collected during the fall were more contaminated than yo ung leaves collected during the spring. The roughness of the outer sur face leaves contributed to the trapping and retention of air particles . The results were compared with corresponding results from lichens an d mosses which were also collected for a similar study.