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

Abstract

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.