Abstract

Investigations were carried out on the effect of heavy vehicular traffic on the deposition of some heavy metals, namely; Lead (Pb), Cadmium (Cd) and Zinc (Zn) on an arable soil (under vegetable cultivation) very close to a major highway using spectrophotometric technique (AAS - Perkin Elmer Analyst 400). Also investigated was the correlation between heavy metal residue in the soil and distance (10, 20 and 30 m) from this major highway as well as, the effect of a barrier on the level of heavy metal fall-out in this soil. Results from this study shows a significantly higher concentration for all the heavy metals on the study site at the different distances considered when compared to those of the control. Pb for instance ranged from between 0.073 to 0.354 mg/kg at the experimental site and 0.053 to 0.063 mg/kg at the control site. Further still, it was observed that in all cases, concentration of heavy metals in the soil has an inverse variation with distance from the road. Also, the construction of a barrier (a fence of about 2.5 m high) at a distance of about 20 m from the highway was suspected to have contributed to a reduction in the level of all the heavy metals, particularly Zn, where the reduction was found to be significantly lower at the distances (20 and 30 m) from where this barrier was present.

Key words: Heavy metals, arable soil, toxic pollutants, vehicular emissions.