Assessment of Heavy Metal Contamination in Soils Around Automobile Mechanic Workshops in Ibadan, Oyo State

This study assesses heavy metal contamination levels in soils surrounding automobile mechanic workshop clusters in Ibadan, Oyo State, located in Nigeria's South West geopolitical zone. Automobile repair activities generate waste oils, battery acid, and metallic debris that introduce lead, zinc, copper, cadmium, and iron into the local soil environment, creating human health risks through dermal contact, dust inhalation, and vegetable crop uptake in adjacent kitchen gardens. Using a descriptive survey design, surface soil samples (0 to 15 cm) were collected from three high-density mechanic workshop clusters and one control site in a residential area without workshop activities. Samples were digested by aqua regia and analysed for lead, zinc, copper, cadmium, iron, and manganese concentrations by atomic absorption spectrophotometry. Geo-accumulation indices and pollution load indices were calculated for each metal at each site. Findings revealed lead concentrations up to 348 mg/kg and cadmium up to 4.2 mg/kg at workshop sites, exceeding Dutch intervention values for contaminated soils. Pollution load indices indicated heavily polluted status at all three mechanic cluster sites compared to the clean reference. Spatial analysis showed contamination extending up to 30 metres from active workshop boundaries. The study recommends immediate remediation of the most contaminated sites, prohibition of food crop cultivation within 50 metres of workshop clusters, and regulatory enforcement of waste oil disposal standards in Ibadan municipality. Keywords: heavy metal contamination, mechanic workshops, Ibadan, soil pollution, lead.