Oyebade, A*; Oloyede, H.O*; Omodara, N.B and Ojo, B.M.
Department of Chemistry, Adeyemi College of Education, Ondo, Nigeria
This study was designed to determine the total concentrations of various species of heavy metals in surface soils and associated sediments obtained from some major roads in Abeokuta, Ogun State; identify the major sources of the metals in each of the areas sampled and identify measures to prevent the contamination of the environment. The study involved sampling of roadside dusts of five major locations in Abeokuta, Ogun state to assess the level of contamination. Speciation studies were carried out to determine the various fractions of seven metals namely: Zn, Pb, Cu, Mn, As, Cr and Cd. Selective sequential extraction procedure developed by Tessier et al, (1979) was used to fractionate roadside dust samples. This method involves partitioning heavy metals into five operationally defined fractions: exchangeable, carbonate, Fe-Mn oxide bound, organic and residual. The concentration of Zinc in the investigated samples was the highest (164.83µg/g). Chromium had the second highest value with a concentration of 101.3µg/g. This was followed by Manganese and Lead with concentrations of 87.03 and 80.33 respectively. The percentage mobility factors reported were in the order: Mn > Zn > Pb > Cu > Cd > Cr > As. There were indications that the levels of Zn, Pb, Mn, and Cu detected for the sampled areas were mainly associated with the carbonate bound fraction in the soil samples. The distribution of the metals in the various fractions and results of mobility factors confirmed their differences in mobility and bioavailability. There was also an indication that sources of these metals were mainly anthropogenic.
Keywords: Heavy metals, Contamination, Roadside dusts, Speciation.