Chemical Fractionation of Lead, Copper, Zinc and Cadmium in Soils along the Highway From Tafo to Aboaso in the Ashanti Region of Ghana

Knowledge of the mobility and bioavailability of heavy metals in soils is necessary for the design of remediation processes and the establishment of environmental guidelines for heavy metal pollution. Single extractions were used to fractionate four heavy metals (Pb, Zn, Cu and Cd) from a total of fifty-four roadside soil samples into four operationally defined groups: acid soluble, reducible, organic and residual fractions. Pb was mostly bound to the reducible fraction (51.14%). The next most important fraction for Pb was the residual fraction (21.98%) followed by the acid soluble fraction (14.15%) then the organic fraction (12.73%). Zn was mostly associated with the residual fraction (48.37%). The percentages of Zn bound to the reducible and acid soluble fractions were 38.95% and 6.64% respectively. The organic fraction contained 6.04% of total Zn. The trend of Cu distribution among the fractions was: organic fraction (48.59%), reducible fraction (25.61%), residual fraction (20.58%) and acid soluble fraction (5.01%) while that of Cd was: reducible fraction (45.09%), the acid soluble fraction (34.71%), residual fraction (20.19%) and organic fraction (0.00%). The percentage of the metals which were found to be bioavailable and the order of potential bioavailability was: Cu (79.21%) > Cd (79.16%) > Pb (77.97%) > Zn (51.55%).