Distribution of Heavy Metals in Some Tree Leaves along the Main Road in an Agricultural Area

Four types of tree leaves were investigated (olive, fig, oak, and carob). The tree leaf samples, washed and unwashed, were analyzed for lead (Pb), cadmium (Cd), copper (Cu), and zinc (Zn) by atomic absorption spectrophotometry. Variable levels were found in these plants. In addition, all heavy-metal concentrations of the samples were significantly higher than their counterparts of the control, indicating heavy-metal pollution was taking place. Very high correlations were found between heavy metals in the same plant, between different plants, and between plants and soil, indicating common sources of heavy metals, possibly soil and soil pollution sources such as traffic. The accuracy of the analytical method used for heavy metals was checked by analysis of standard reference materials, rye grass (CRM 281) and spinach leaf (SRM 1570a). The percentages of recovery of both reference materials for Cd, Cu, Pb, and Zn were better than 93%.