Spatial Distribution of Some Heavy Metals in Soils of Zanjan Industrial Region

Soil pollution because of heavy metals not only can directly affect the soil physical and chemical properties but also may turn out to be a serious hazard to human health due to affecting both the food chain and groundwater. Zanjan Province in Iran is considered as one of the most industrialized areas in country due to its heavy metal mining industries. The main purpose of the present study was to evaluate the spatial distribution of heavy metal concentrations using geostatistics approach and to provide the detailed soil maps in order to identify the contaminated farmlands affected greatly by Zanjan contaminated industrial site. Hence, 150 topsoil (0-10 cm) samples were randomly gathered from the area surrounding the contaminated industrial sites to adjacent farmlands with 20,000 ha area in order to assess the spatial variation of heavy metals such as zinc, copper, lead and cadmium. Total zinc, copper, lead and cadmium after the digestion process were measured using atomic absorption spectroscopy (AAS). Therefore, soil enrichment factor (EF) was calculated to identify heavy-metal affected sites. The results of kriging interpolation analysis showed that heavy metals concentrations in the eastern and central parts of the Zanjan area generally exceeded the threshold values (Pb=402.5 mg/kg, Zn=670 mg/kg, Cu=585 mg/kg and Cd=10.5 mg/kg). Therefore, the eastern and central parts of the study area seem to have a high priority for the both soil leaching and phytoremediation operations.