Evans, F. G.; Amachree, D.; Soberekon, I. J.; Akhigbe, E. O.; Nicholas, D. O.; Eli, A. A.; Okoro, E.; Gamage, I. E.; Nathaniel, A. M.; Raimi, M. O.

Rationale: The contamination of soil with crude oil poses significant environmental and ecological threats. Bioremediation, particularly through the use of organisms like Pleurotus ostreatus (mushroom) and Eisenia fetida (earthworm), has emerged as a promising approach to mitigate crude oil pollution. Understanding the effectiveness of these organisms in reducing hydrocarbon levels in contaminated soil is crucial for devising sustainable remediation strategies. Objectives: This study aimed to evaluate the efficacy of Pleurotus ostreatus and Eisenia fetida in remediating crude oil-polluted soil. Specifically, it sought to assess the hydrocarbon profiles in soil treated with these organisms across varying concentrations of crude oil pollution. Method: Crude oil concentration levels ranging from 0% to 10% were applied to soil samples, alongside control treatments including soil only, soil with earthworms, and soil with mushrooms. Each treatment was replicated five times using a randomized complete block design. Standard methods were employed to determine the hydrocarbon contents of the soil. Results: The results indicated a significant increase (P<0.05) in various hydrocarbon parameters, including total organic carbon (TOC), total hydrocarbons (TPH), total petroleum hydrocarbons (TPH), polycyclic aromatic hydrocarbons (PAH), and total oil and grease (TOG), with escalating concentrations of crude oil pollution. However, soil treated with Pleurotus ostreatus and Eisenia fetida exhibited noteworthy reductions in these hydrocarbon levels. At the three-month mark, mushrooms demonstrated a remarkable ability to reduce hydrocarbon content by 70%-90% compared to the pollution treatment. In contrast, earthworms exhibited minimal potential for hydrocarbon reduction, particularly at both three and six month intervals. For instance, TOC reduction reached a maximum of 96% with mushroom treatment and 85% with earthworm treatment at 5% crude oil pollution over six months. Conclusion: The findings highlight the effectiveness of Pleurotus ostreatus in significantly reducing hydrocarbon levels in crude oil-polluted soil compared to Eisenia fetida. Mushroom-treated soils consistently exhibited substantial reductions in TOC, TPH, TOG, PAH, and THC over the study period, suggesting their potential as a viable bioremediation agent. In contrast, while earthworms showed some capability in reducing hydrocarbon content, their effectiveness was comparatively limited. Recommendation: Based on the results, it is recommended to utilize Pleurotus ostreatus for the bioremediation of crude oil-polluted soils. Further research could explore optimizing remediation protocols involving mushroom-based treatments for enhanced efficiency. Statement of Significance: This study contributes valuable insights into the application of bioremediation techniques for mitigating crude oil contamination in soil. The demonstrated efficacy of Pleurotus ostreatus underscores its potential as a sustainable and eco-friendly solution for remediating hydrocarbon-polluted environments, offering a promising avenue for environmental restoration and conservation efforts.