Contamination Assessment of Potentially Toxic Metals in Road-Side Surface Soils Along Iwo-Ibadan Expressway, Nigeria

This study was carried out to assess the contamination levels of road-side surface soils by potentially toxic metals due to their persistence and bioaccumulative nature in the ecosystem. Surface soils were sampled at various equidistance points along Iwo-Ibadan expressway, Nigeria and were then digested and analyzed for elemental concentrations using Atomic Absorption Spectrophotometer. Zn (72.91 mg/kg) had the highest mean concentration followed by Pb (54.66 mg/kg), Mn (31.32 mg/kg), Fe (12.16 mg/kg), Cd (11.92 mg/kg) and Cu (4.06 mg/kg). Variation in the elemental levels across the sampling points was a reflection of the variation in traffic density. The results of the contamination factor and geoaccumulation index indicated varying degrees of contamination. The modified degree of contamination and the pollution load index suggested that the road-side surface soils are contaminated with the metals. Cluster analysis indicated that the metals are associated with car components and vehicular emissions. It is therefore recommended that strict regulations be put in place against the use of leaded gasoline as vehicular fuels. Adequate and frequent monitoring of highway contamination by metals as a result of their bioaccumulative tendencies is also suggested.