Phytoremediation of heavy metals in spent engine oil-polluted soil by Senna alata L.

Senna alata L. was used to remediate heavy metals in soil polluted with spent engine oil (SEO). One hundred and twenty polythene bags filled with 20 kg of soil each were separated into parts A and B. Part A contained S. alata seedlings while part B had no plant. They were set up in completely randomized design. To simulate spillage, 0.15% v/w, 0.75% v/w and 3.75% v/w concentrations of SEO were used to pollute soil planted with seeds of S. alata, 57 days after planting. These treatments were repeated in soil without seeds. Control had no pollution. Heavy metal analyses of SEO, vegetated and non-vegetated soil, leaves, stems and roots of S. alata were determined using Flame Atomic Absorption Spectroscopy, 106 days after pollution. Vegetative and reproductive parameters were also determined. Copper, Lead, Zinc, Iron and Aluminium were detected in SEO. Concentrations of heavy metals in vegetated soils were significantly (P < 0.05) less than those of non-vegetated soils. Cu accumulation in stem was significantly (P < 0.05) higher than those of leaves and roots. Zn and Al were significantly (P < 0.05) higher in root than those in leaves and stems. Fe and Pb were significantly (P < 0.05) higher in leaves than in stems and roots. Aerial roots were formed by S. alata which increased significantly with increase in concentrations of SEO applied. However, many vegetative parameters such as plant height, number of pinnules, number of roots, leaf area and stem circumference increased significantly (P < 0.05) but some reproductive parameters such as number of inflorescence and dry weight of seeds decreased after pollution. Hence, S. alata is suitable for phytoremediation and in particular, phytoaccumulation of heavy metals in SEO contaminated soil.