The Potential of Chromolaena Odorata (L) to Decontaminate Used Engine Oil Impacted Soil Under Greenhouse Conditions

This study reports on the use of Chromolaena odorata (L) R.M. King and H. Robinson, an Asteraceae (compositae) and an invasive alien weed in Africa for the remediation of soil contaminated with used engine oil. Used engine oil from a motor service garage was used to artificially contaminate soil taken from a garden to give total petroleum hydrocarbon (TPH) of between 1 and 40 g kg-1. Chromolaena odorata (L), propagated by stem cuttings were transplanted into the contaminated soil and watered just enough to keep the soil at about 70% water holding capacity for 90 day. A set of control experiments containing 40 g kg-1 used engine oil but without plants was set up. All experiments were set up in triplicates. Although the plants in the experiments containing higher than 30 g kg-1 used engine oil showed relatively slower growth (fewer branches and leaves, and shorter in height) compared to those containing lower concentrations, the plants in all the experiments continued to grow until the end of the 90 day period. Residual TPH after 90 days showed that between 21 and 100% of oil was lost from the planted soil while only 11.5% was lost in the control, which did not contain plants during the same period. Analysis of plant tissues showed that both shoot and root tissues contained detectable levels of TPH and selected PAHs were also detectable. Biomass accumulation by Chromolaena odorata was affected adversely by concentrations of oil higher than 20g kg-1. Results of germination rates and germination energy measurements showed that Chromolaena odorata was able to reduce the toxicity of the contaminated soil after 90 days as compared to soils containing freshly contaminated soil.