<span class="word">Microbial <span class="word">and <span class="word"><span class="changedDisabled">Physicochemical <span class="word"><span class="changedDisabled">Responses <span class="word">to <span class="word"><span class="changedDisabled">Spent <span class="word"><span class="changedDisabled">Engine <span class="word"><span class="changedDisabled">Oil <span class="word"><span class="changedDisabled">Contamination <span class="word">at <span class="word"><span class="changedDisabled">Varying <span class="word"><span class="changedDisabled">Chronological <span class="word"><span class="changedDisabled">Intervals <span class="word">in <span class="word"><span class="changedDisabled">Mechanic <span class="word"><span class="changedDisabled">Workshops

Spent engine oil (SEO) contamination and its implications for soil ecosystems are a growing global concern. This study investigates the trend of SEO pollution across four mechanic workshops, aiming to understand the impact of pollutants on soil physicochemical and microbiological parameters. Standard cultural methods were employed to determine the biomass of total heterotrophic bacteria (THB) and hydrocarbon-utilising bacteria (HUB), while chromatographic (GC-MS) methods were used to assess total petroleum hydrocarbons (TPH) and polyaromatic hydrocarbons (PAH). Additionally, atomic absorption spectroscopy (AAS) was used to quantify heavy metal concentrations in the soil. The results indicated that SEO contamination increases levels of TPH, PAHs, total heavy metals, and organic carbon, while reducing soil pH and total organic nitrogen. A correlation study revealed that hydrocarbon pollution negatively impacted total heterotrophic bacteria but stimulated the growth of hydrocarbon-utilising bacteria (HUB). Furthermore, soils polluted for 20 years acted as a sink for heavy metals, PAHs, and TPH, contributing to their accumulation in the soil. This long-term accumulation poses a significant health risk, especially in environments where exposure to such pollutants is persistent. The findings highlight the need for active measures to monitor and remediate SEO-contaminated soils. Effective pollution management strategies are essential to mitigate potential health risks and restore soil health in affected areas, particularly in mechanic workshops that have experienced prolonged contamination.