ENVIRONMENTAL IMPACT OF WASTE LUBRICATING OIL ON SOIL QUALITY IN AUTOMOBILE WORKSHOPS IN DELTA STATE

This study assessed the impact of waste lubricating oil (WLO) management on soil quality in automobile workshops across three local government areas in Delta State, Nigeria. Soil samples were collected using a soil auger from five sites in Uwvie, Warri, Oghara and Sapele automobile workshops. Physicochemical and heavy metal analyses were conducted to evaluate contamination levels. Results showed moderately acidic soils (pH 4.60–7.20) except WARS1, which was slightly basic. Cadmium concentrations exceeded WHO limits, while heavy metals followed the trend Cr > Zn > Pb > Cd. Total petroleum hydrocarbons (TPH) were high (724.09–8630.39 µg/kg), indicating hydrocarbon contamination. ANOVA showed significant variation only in Total Organic Carbon (TOC%) and n-hexadecane, while PCA explained 96% of the dataset variance. The TPH contamination trend was WARS2 > SAPS2 > WARS1 > OGHS1 > SAPS1. The study concludes that improper WLO disposal significantly degrades soil quality, posing ecological and sustainability risks.