ABSTRACT
The detrimental effect of the activities in informal auto-mobile mechanic workshops is a major public health concern; and its impact on groundwater contamination cannot be ignored. We assessed the effect of activities of mechanics in auto-mobile workshops on the quality of groundwater sources. Water samples were collected from hand dug wells situated within 0 to 50 metres in twenty auto-mobile workshops randomly selected across three zones. A residential area was selected as the control site. Analysis of water for some physico-chemical parameters (pH, TDS, Electrical Conductivity, Alkalinity, Oil and Grease) and the heavy metals (Cu, Cd, Cr, and Pb) was done using standard methods. Sanitary inspection was also carried out at each well location. Results were compared with the control and regulatory standards Nigerian Industrial Standard for Drinking Water Quality (NISDQW) and World Health Organization (WHO) guidelines for drinking water quality. Results revealed that mean values of pH, TDS and Electrical conductivity for the three zones, Alphonso, Temidire, and Ojoo were within WHO limits. The concentrations of Cu, Cd Cr and Pb in the water samples ranged from 0.02 - 6.12 mg/l, 0.1 - 2.19 mg/l, 0.2 - 0.79 mg/l and 0.02 - 35.8 mg/l across the three zones respectively. Mean concentrations of Cu (mg/l) were significantly higher in Alphonso (2.5 ± 2.06) than in other zones. Mean concentration of Cr (mg/l) was 0.34 ± 0.28, 0.37 ± 0.13 and 0.31 ± 0.3 for Alphonso, Temidire and Ojoo respectively. Cadmium was also present in all the zones but Pb was only detected in Alphonso. The mean concentrations for heavy metals were significantly higher when compared with the permissible limits for both NISDQW and WHO. The degree of groundwater contamination indicates poor water quality in the study area, and this requires regular monitoring. Enforcement of environmental regulations guiding activities of auto-mechanics should be done so that they can embrace environmentally friendly practices to reduce pollution.