Road Construction and Trace Heavy Metals in Roadside Soils along a Major Traffic Corridor in an Expanding Metropolis

City growth often time results in advancement and development in transportation which comes with its attendant changes in road infrastructure and transport support services such as road side mechanic workshops, vulcanizers and bus stops. A byproduct of these attendant contiguous activities and processes is the emission and release of trace heavy metals. Trace heavy metals have been identified as major carcinogens. This study aimed at determining the occurrence and concentration of heavy metals in roadside soils in an expanding third world metropolis. To achieve the aim of the research, the total length of the road within the study section was measured. Ten sample locations were indentified at about 2.5km intervals along the road section under review. The heavy metal concentration was determined the using Buck Scientific 210 VGP Atomic Absorption Spectrophotometer. Heavy metals such as Iron (Fe), Copper (Cu), Cadmium (Cd), Lead (Pb) and Mercury (Hg) were determined. The result of the analysis showed that the concentration values ranged from <0.001 to 48.90 µg/mg. The results also revealed that the experimental sample points recorded higher values than the control samples; however, some of the control points had relatively higher concentration values. This observation may have emanated from the low lying trajectory and topography of the surrounding area, which allows run-off from the road side soils to wash off heavy metals and deposit them at these lower lying areas. The sources of these trace heavy metals are attributed to emissions from motor vehicles that ply the road on a day to day basis. Emanating from the findings, this study recommends that improved public transportation and cleaner sources of energy is recommended.