Concentrations of Heavy Metals in surface soil of Zahedan City

Heavy metals in surface soil which originate from different sources (e.g. traffic, industrial emission, weathering of building) can be accumulated in human body via inhalation and dermal absorption pathways. Therefore, this study aimed to investigate heavy-metal pollution profile of the soils and assess the soil quality in Zahedan.
Heavy metal concentrations in surface soils were investigated by a cross–sectional study carried out in early autumn 2013. Street dust samples were collected from different areas (5 regions) using a clean plastic dustpan and broom. At each sampling location, 5 subsamples were randomly taken and mixed together to obtain a composite soil sample. In total 50 samples were taken from all regions. The street dust samples were dried at room temperature prior to acid digestion and the concentrations of Zn, Cd, Cr, Ni, Pb and Cu were measured using ICP-MS.
Results of analysis showed that in all studied areas; urban park, commercial area, high traffic, residential area and industrial area the concentrations of Cd, Cr, Cu, Ni, Pb, and Zn were 0.01± 0.06, 37.53 ± 6.96, 29.68 ± 10.25, 51.09 ± 8.53, 28.37±6.52 and 184.30 ± 25.94 mg/kg, respectively. The concentrations of Cd, Cr, Cu, Ni, Pb, and Zn in all the regions studied (except residential area) exceed the corresponding background levels (i.e. suburb area).
This study showed that land use significantly increase heavy metal levels of urban soil in Zahedan. The highest concentrations of heavy metals were found in commercial and high traffic areas where the traffic rates are high. Therefore, decrease in traffic rate and improving public transportation may increase quality of urban soils.