CONCENTRATION OF HEAVY METALS IN LEAVES OF LIME TREES (TILIA SPP.) IN THE URBAN AREAS OF TIRANA, CAPITAL OF ALBANIA

Rapid urbanization leads to an increase in air pollution. The source of pollution that contributes mostly is the release of emissions from fossil fuels used in internal combustion engine vehicles. Vegetation can be used to mitigate urban pollution. Lime tree is a common urban tree, well adapted to the conditions of Tirana, the capital of Albania. Within this study, the concentration of the following heavy metals, Pb, Cd, Cr, Cu, Ni, Mn, Zn, Al, and Fe, have been measured in the leaves of three species of the Lime tree, and specifically Tilia tomentosa Moench, Tilia cordata Mill., and Tilia platyphyllos Scop. The leaf samples were collected in spring, summer, and autumn and in three stations with qualitatively evaluated different intensities of urban traffic (high,medium, low). Results show that the average concentration of heavy metals measured in the leaves of Lime tree followed the order: Fe>Al>Zn>Mn>Cu>Ni>Cr>Pb>Cd. Cr, Al, and Fe were measured at a higher concentration in the leaf samples collected in autumn, compared to the leaf samples collected in spring in the same stations. For Cu, it is exactly the opposite, meaning that the concentration was higher in the leaves collected in spring, compared to the ones collected in autumn in the same stations. Whereas, for the concentration of Pb, Cd, Ni, Mn, and Zn it was not noticed a straight seasonal trend. The average measured concentration of Cu, Cd, Ni, Cr, and Al, resulted in exceeding the recommended threshold of the World Health Organization, indicating pollution from these heavy metals.