Heavy metals contamination of soil and groundwater at automobile mechanic villagesin Ibadan, Nigeria

Abstract

The aim was to determine the concentrations of heavy metals, in soil and groundwater at automobile mechanic villages located in Ibadan, Nigeria, compare the results with guidelines from various countries, draw conclusions and make recommendations. Soil and groundwater samples from 7 automobile mechanic villages and a control site in Ibadan, Nigeria were analysed for selected heavy metals namely: Cd, Cu, Pb, Cr and Ni. Soil samples were obtained in triplicates and at depths of 0 to 15, 15 to 30, 30 to 45 and 45 to 60 cm. Water samples were obtained from dug wells at the sites. Overall, values of Cd, Cu, Pb, Ni and Cr in the workshop soil samples ranged from 0.41 to 17.23; 1.48 to 476.0; 18.25 to 15100; 2.0 to 25.0 and 2.0 to 29.75 mg.kg-1 respectively. Evidence of contamination of these soils was obvious when these values were compared to those of the control. Ni was below detection limit in all control samples while Pb and Cd were less than 0.05 and 0.002 mg.kg-1 respectively. Cu ranged from 4.30 to 10.05 mg.kg-1 while Cr ranged from 6.25 to 19.75 mg.kg-1. Compared to established limits set for soils in some countries, the values measured in this study were higher than these limits in several cases. Compared to the limits set by WHO for drinking water, values measured in the groundwater samples were lower than those limits for the heavy metals with the exception of Cu where all the values were higher than the limits. The recommendations of the study include execution of some form of phyto-remediation measures at the villages; strict compliance to regulatory limits in sludge to be released from these villages into the environment and the enforcement of other environmental protection regulations to arrest the ongoing buildup of these metals on those locations. Findings from this study will be of immense help to researchers and environmental regulators working in this area of interest in developing countries.   Key words: Soil, groundwater, lead, cadmium, copper, chromium, nickel.