Evaluation of physicochemical properties and heavy metal levels in soils from selected auto mechanic workshops in imo state, nigeria

Environmental contamination as a result of indiscriminate disposal of spent engine is a serious global issue. The study was carried out to evaluate the physicochemical properties and selected heavy metal levels in soils collected from auto mechanic workshops in Owerri, Okigwe and Orlu zones of Imo State. A total of 27 soil samples (9 from each zone) were randomly collected from a depth of 0 – 20 cm with an improvised soil auger. At each auto mechanic workshop, three sampling points were mapped out for sample collection and homogenized to obtain a composite. Physicochemical properties of soil were analyzed using standard analytical protocols while metal analysis was carried out using AAS. Results showed that all the physicochemical properties of the soil were marginal when compared to the control across the zones. The textural class was sandy loam and moderately acidic. Heavy metal (Pb, Cr, Cd, Zn, Al, Fe, Cu, Ni, Co, and As) were detected in the soil at varying levels but were observed to be below the permissible limits set by the DPR in the studied sites. Pollution index showed that the soil quality was moderately contaminated with moderate potential ecological risk factor in all the sites. The study revealed a gradual buildup of heavy metals in the sampled areas and therefore underscores the need for proper disposal of spent engine oil to avert heavy metals toxicity in the soil as most of these metals are leached down the profile thereby polluting underground waters and posing danger to human health. Continuous monitoring and the use of ecofriendly method (phytoremediation) to remediate the heavy metals are recommended.