Level of Heavy Metals in Soil Samples from Farmlands along Highways in Parts of Owerri, Nigeria

Abstract

The research was designed to ascertain the concentrations of heavy metals (Cu, Pb, Zn, Ni, Cd) in soil samples from farmlands along highways in parts of Owerri. Soil samples were collected from cassava farms along three major roads with high traffic density and a rural road that served as control location, for possible heavy metals contamination due to vehicular emission. Standard laboratory procedures were adopted to determine the concentration of heavy metals using Atomic Absorption Spectrophotometer (AAS). Contamination factor (CF) and Pollution Load Index were mathematically calculated. The results revealed that the mean concentrations of metals in soil samples in mg/kg ranged from 3.00-6.31 for Cu; Pb, 0.09-4.00; Zn, 3.97-8.59; Ni, 0.001-0.96; and Cd, 0.31-0.79. These metals showed decrease in concentrations with increase in distance away from the highway. The values of contamination factor (CF) were low except for Cd and Pollution Load Index (PLI) for all soil studied showed no sign of pollution. There was no correlation between traffic density and concentration of heavy metal in soil except for Cd (Rs= 0.800). The overall results showed evidence of some heavy metal pollution on the soils with possible cumulative effect over time.