The Role of EDTA on Heavy Metals Phytoextraction by Jatropha gossypifolia Grown on Soil Collected from Dumpsites in Ekiti State Nigeria

Jatropha gossypifolia has been known to thrive well in tropical climate, most importantly in Nigeria where they are found to grow naturally on dumpsites. The potential use of this robust tropical plant in phytoremediation technology should be advocated especially for developing countries. This study investigates the effect of enhanced phytoextraction on the accumulation of the following heavy metals; (Cd, Cr, Fe, Mn, Pb, Zn, Ni, Cu, Co and Sn) by J. gossypifolia cultivated on soil collected from dumpsites in Ekiti state, South Western Nigeria, with application of 1g/kg EDTA (Experiment) and without (control). Application of 1g/kg EDTA did not adversely affect plant growth, except at preflowering stage where were yellowing of leaves.
The concentration of heavy metals in tissues of plant were higher in the experiment than control, with concentration of Pb (376.0, 350.0, 355.2 and 328 mg/kg; experiment, 184.0, 180.0, 169.0 and 159.0 mg/kg; control), Cu ( 962.0, 958.0, 898.0 and 818.0; experiment, 650.0, 526.0 464.2 and442.0 mg/kg; control) and Cd (416.8, 418.2, 399.0 and 377.5; experiment, 167.3, 164.2, 147.8 and 142.2 mg/kg) at Aba Egbira, Atikankan, Igbehin and Moshood street dumpsites respectively in the shoot of the plant. Highest concentrations of heavy metals were obtained in leaves of the plant. Notably, concentration of Pb, Cu and Cd were greater than the threshold value of 100mg/kg, indicative of the fact that J. gossypifolia could be a good candidate for Pb, Cu and Cd-phytoextraction. Bioaccumulation factor (BF), translocation factor (TF) and remediation ratio (RR) values greater than one also revealed the effectiveness of the plant to translocate Pb, Cu and Cd to their harvestable portion and phytoextraction efficiency under the chelant-assisted phytoremediation. However, the concentration of heavy metals did not vary significantly at p<0.05, least significant difference (LSD test) in all dumpsites investigated. Therefore, the use of J. gossypifolia is advocated as a candidate plant for restoring dumpsites polluted with heavy metals.