Distribution and Potential Mobility Assessment of Some Hazardous Metals in Soil of Mechanic Workshops: A Case Study of Akoko Land in Nigeria

Eventual ecotoxicological risks associated with the presence of hazardous metals depend on their identity, chemical forms of association in soil, mobility and bioavailability. Based on this understanding, determination of the chemical form of a metal in soil is important. Sequential extraction was used to fractionate Cd, Cr Cu, Fe, Mn, Ni, and Zn in soils from three different mechanic workshops in Ikare and Akungba Akoko, Ondo-Nigeria into seven operationally defined groups (exchangeable, carbonate, organic, MnOx, FeOx-amorphous, FeOx-crystalline, and residual) to assess the potential mobility and likely bioavailability of these metals in the soil profiles. The residual fraction was the most abundant pool for all seven metals examined. A significant amount of the metals with the exception of Zn were present in the potentially available fraction: non-residual fraction. Assuming that the potential mobility and bioavailability of these metals are related to their solubility and geochemical forms, and that they decrease in the order of extraction sequence, the potential mobility and bioavailability for these seven metals in the soils were: Fe > Cr > Cd >Mn> Cu > Ni >Zn. In the trend of fractions distribution, metal distributions in different chemical fractions in these soils depended on respective total metal concentrations.