Contamination of Soils and Plants Along Urmia-Salmas Highway (Iran) to Some Heavy Metals

 
      Vehicles contaminate soils and plants along the roadside by different ways and finally these contaminants enter the food chain. The aim of this study was to assess Pb, Cd, Zn and Ni contamination of soils and plants around the Urima-Salmas highway with heavy traffic. Geoaccumulation index (I_geo) was calculated for characterizing the contamination levels of heavy metals in the soils. Metal accumulation index (MAI) was also employed for assessing simultaneous accumulation of the studied metals by each plant. Results showed that concentrations of these metals were higher than those of the control samples (p ≤ 0.05) for soils and most of the plants grown in the roadside. In comparison with background areas, surface soils and plants grown along the roadside were relatively contaminated. Also soils and plants of the roadside were specifically contaminated with Pb. Therefore, animal grazing in this site would be of potential transfer risk of these metals (especially Pb) to the food chain. In general, concentration of the metals, specifically Pb, was higher in plants which were closer to the road. In comparison with other plants studied, Yarrow plant (Achillea millefolium) with MAI = 100.01 had better ability for simultaneous absorption of different metals. According to the results of this study, actions are needed to be applied for better management of the soils and grazing of the plants in the roadsides.