Temporal And Spatial Variability Of Lead Levels In Salsola Kali Near Razan-hamadan Highway

The contribution to environmental pollution of heavy metals from automotive emissions has been the subject of intensive investigation in recent years. Airborne metal particulates, such as Pb, have been attributed mainly to emissions from motor vehicle exhausts. The objectives of this study were to evaluate the temporal and spatial variability of lead levels in Salsola kali in the vicinal soils of Razan-Hamadan highway, Iran. In both sides of the highway sampling was carried out on a transect (200-m long), in vertical direction from highway with a separation distance of 20 m, thereby providing 10 actual sampling locations for each side of highway. During 2 seasons of 2002, plant samples were taken from shoots and roots with 3 replicates. Root and shoot organs of samples separately analyzed for Pb concentration with dry ash method by atomic absorption spectroscopy. Lead levels in most of the analyzed plant samples were higher than the natural levels. Lead concentration in the plant organs was decreased exponentially with distance from the road. In both seasons the decrease constant for Pb in root organ was higher than that for shoot organ. The decrease constants for Pb in root and shoot organs of the plant were higher in spring compared to those in autumn. Lead accumulation was significantly higher in shoot organs compared to root organs. The highest lead contents may exceed 37.66 μgg^-1 in the shoot organs of the plant in east side of the road. In both organs of the plant especially in shoot organs lead concentration in autumn compared to that in spring was relatively higher. Translocation factor for lead in the plant sampled in autumn was also higher than that for those sampled in spring.