Phytoremediation of Heavy Metals Contaminated Agricultural Soil Planted to Jatropha curcas

This study was conducted to assess the potential of Jatropha curcas in remediating soils contaminated with heavy metals from hydrocarbon fuel. Matured cuttings of Jatropha plant were planted in the plastic pots filled with soils contaminated with three different level of HMs concentration; 250mg/kg, 500mg/kg and 1000mg/kg respectively arranged in a Completely Randomized Design (CRD). The aim was to appraise if Jatropha curcas can be used to treat the heavy metals; Zn, Ni, Cd, Pb and Cu in the contaminated soils and determine whether the treated metals complied to soil permissible limit concentration of agricultural soils advocated by Nigerian and other related international standards. Findings indicated that all the analysed metals recorded a significant statistical difference with different level of soil contamination (P<0.05). However, despite their concentration achieved compliance at their initial soil contamination, Cu, Zn and Ni were highly removed by Jatropha plant though the latter metal failed compliance to Nigerian standard at both pre and post Jatropha planting period. Moreover, the metals showed highest removal efficiency in the range of 57%-95% at 500mg/kg hydrocarbon fuel soil contamination. In contrast, Cd metal concentration was low and above compliance limit at pre and post Jatropha planting period except at 1000mg/kg hydrocarbon fuel contamination that achieved compliance of United States (US) with removal efficiency in the range of 8%-42%. However, Pb metal concentration was high and variable at both initial contamination and concentration after Jatropha planting, with the metal achieving and failing compliance of some countries at certain level of concentration after the Jatropha phytoremediation. Overall, the outcome of this research indicates that the Jatropha plant has depurated the metals effectively from the contaminated soils particularly Cu, Zn and Ni at 500mg/kg level of contamination despite the fact that the phytoremediation process was within the period of two months. Hence, the continuation of the experiment is needed in order to fully determine the actual period and appropriate level of soil contamination required for the optimum metal phytoremediation and type of metals the Jatropha plant prefers most in terms of the remediation compared to others.