Remediation of Spent Engine Oil Polluted Soil Using Indigenous Plant Species

Background and Objective: Soil contamination with engine oil and other petroleum hydrocarbons is a major problem in Nigeria. The study was carried out to assess the potential of Chromolaena odorata, Aspilia africana and Axonopus compressus in the remediation of used motor oil-contaminated soil. Materials and Methods: An equal volume of soil was spiked with 16% (w/w) of used motor oil and monitored for 90 days. The experiment was laid out in a complete randomized design in three replicates each. The test plants were harvested after 90 days and analyzed for the presence of heavy metals using AAS. The results obtained were analyzed using Microsoft Excel. Results: The variable concentrations of heavy metals and TPH were accumulated by the test plants from the contaminated soil and were stored in the root, shoot and leaf. Metal accumulation patterns were in the order: Chromolaena odorat>A. africana>A. compressus. Chromolaena odorata and A. africana exhibited characteristics typical of a phytoextractor while A. compressus could be applied as a phytostabiliser of spent engine oil-polluted soils. The result further showed that TPH content of C. odorata accumulated the highest level of TPH (178.43 mg/kg) in the leaf followed by A. compressus (46.58 mg/kg) and A. africana (26.26 mg/kg). Conclusion: Thus, Chromolaena odorata, Aspilia africana and Axonopus compressus possess hyper-accumulative uptake capacity for bioavailable residual oil heavy metals and therefore could be suitable for the phytoremediation of spent engine oil-contaminated soil.