Variations in plant and soil lead and cadmium content in urban parks in Athens, Greece

The concentrations of Pb and Cd were studied in the plant species Pittosporum sinensis (Mock-orange) and Nerium oleander (Oleander) and in the soil of two major parks of Athens. The composition and the density of vegetation differs remarkably in the two parks. The concentrations of both metals were considerably higher at the peripheral zones and decreased towards the interior of the parks. At a distance of 60 m from the periphery to central zones the values almost reached background levels. The degree of plant and soil contamination was well correlated to the density and the structure of vegetation, the traffic volumes, the nature of the leaf surface of the two plants and the wind velocity.