Characterization andmetals fractionation of street dust samples from Tehran, Iran

Fifty street dust samples were collected from Southern and Eastern parts of Tehran, the capital of Iran. Samples were collected during summer under dry and stable weather conditions. Total concentrations of copper (Cu), cadmium (Cd), lead (Pb), chromium (Cr), nickel (Ni), zinc (Zn), iron (Fe), manganese (Mn) and lithium (Li) were determined. Ten samples were then selected for characterization, metals fractionation and single stage extraction studies. X-ray diffraction (XRD) and X-ray fluorescence (XRF) were utilized to study the crystalline forms of metals and chemical compositions. In addition, sequential and single extraction procedures were used to determine the concentrations of six heavy metals (i.e. Cu, Cd, Pb, Cr, Ni and Zn), and also the mobility and bioavailability of elements. The risk assessment code (RAC) and IPOLLwere employed for the risk assessment and pollution intensity of metals, respectively. Results showed that the single extraction procedure could be used to estimate the total concentrations of most metals as an appropriate alternative for total digestion. The mobility and potential availability of metals in Tehran street dust followed the order of Cd > Zn > Pb > Cu > Ni > Cr. The risk assessment code results showed high risk for Pb, Cd and Zn and lowmedium risk for Ni, Cr and Cu, and correlated positively with IPOLL result.