Study of fractionation, mobility and risk assessment of selected metals in suburban, urban and roadside soil from Pakistan

This study was carried out to elucidate the chemical fractionation pattern of selected metals (Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Pb, Sr and Zn) in the soil collected from roadside, urban and suburban environment. Modified sequential extraction method was applied to assess the exchangeable, reducible, oxidisable and residual fractions of the metals in soil samples. Quantification of the metals was performed by atomic absorption spectrometry. Various statistical methods were used to evaluate the comparative distribution and mutual relationships among the metals. In addition, risk assessment employing contamination factor, enrichment factor and risk assessment code were also carried out. Among the metals, Ca, Sr, Mn, Mg, Cd, Co and Pb exhibited significant mobility and availability whereas Zn, Fe, Cu and Cr were mainly found in the residual fraction. Most of the soil samples exhibited low risk for Fe, Zn, Cu and Cr, but medium risk was associated with Co, Mn, Pb and Cd, while Ca and Sr showed high risk in most of the cases. Similarly, Zn, Co, Sr, Pb and Cd exhibited moderately severe to extremely severe enrichment of the metals in soil. Cluster analysis indicated significant anthropogenic contamination of the metals in soil.