Forms of Cd, Pb, Zn and Cr in contaminated soils from Raiwind, Lahore, Pakistan

The metals Cd, Ph, Zn and Cr occurring in the area of Raiwand (Lahore), which has been subjected to severe metal contamination due to municipal solid waste, were studied via sequential extraction analyses. Concentrations of the metals ranged from background levels to levels well in excess of the maximum tolerable limits in agricultural soils. Concentrations of Cd ph, Cr and Zn ranged from 0.2 to 70, 2.6 to 640, 4.7 to 1134 and 8.4 to 300 mg/kg of soil respectively. Higher amounts of noresidual fractions of Cd, Pb, Cr and Zn ranged from 59 to 88.5, 60 to 89, 51 to 83, 35 to 81 percent of contaminated soil, respectively. Assuming that mobility and bioavailability bf these metals are related to their solubility and geochemical forms, and decrease in the order of extraction sequence, the apparent mobility and potential bioavailability for these four metals in the soils decrease in the order: Pb > Cd > Cr> Zn.