Chemical fractionation of heavy metals in soils around the vicinity of automobile mechanic workshops in Kaduna Metropolis, Nigeria

Abstract

The study of heavy metals in environmental niches is essential, especially with their potential toxicity to human life. Metal toxicity depends on chemical associations in soils. For this reason, determining the chemical form of a metal in soils is important to evaluate its mobility and bioavailability. In this manner sequential extraction was used to fractionate seven heavy metals (Cd, Cu, Ni, Zn, Cr, Fe and Pb) from ten contaminated soils into six operationally defined groups: water soluble, exchangeable, carbonate, Fe -Mn oxide, organic, and residual. The residual fraction was the most abundant pool for all the metals examined. A significant amount (2.00 to 73.47, 1.77 to 17.78, 9.76 to 58.54 and 1.71 to 54.11% respectively) of Cu, Cd, Cr and Pb was present in the potentially available fraction: non residual fraction. Contamination of Zn, Ni and Fe in these soils was not as severe as Cu, Cd, Cr and Pb. Overall, the order of contamination was Cu > Cr > Pb > Cd > Ni > Zn > Fe. The study indicated that the possible pollution of soils of this environment was as a result of activities carried out within these areas. Key words: Fractionation, heavy metals, mechanic, workshops, Kaduna.