Uptake of lead, nickel and copper by three mucuna species

Agricultural soils of oil producing states in Nigeria have been severely affected by oil exploration activities and there is need to restore such soils to a manageable level. Phytoremediation uses plants whose rhizospheres are able to accumulate heavy metals from the soil. In order to know the capacity of Mucuna species to grow in soils polluted with crude oil and assess their capability to accumulate heavy metals which are normal components of crude oil, a field experiment was carried out. This experiment was a factorial (3 x 5) arrangement in a completely randomized design. Factors and levels were three species of Mucuna (M. veracruz, M. jaspodea and M. ghana) and crude oil concentrations (volume/weight) in the soil (0 %, 1 %, 2 %, 3 %, and 4 %). Heavy metals (nickel, lead, copper and vanadium) concentrations of crude oil provoked soils were determined prior to planting and then 12 WAP. The three Mucuna species accumulated heavy metals in their vegetative parts. Nickel accumulated more in the roots, than in the leaves, while copper and lead were more concentrated in leaves of the three Mucuna species, the concentration of copper was higher (highest value of 87 mg/g). However, the highest percentage of heavy metals reduction in the contaminated soils was that of lead with a percentage of 47.37 % reduction in the soil. The uptake of these three heavy metals by the vegetative parts of these Mucuna species in response to oil pollution was discussed as a possible use in phytoremediation.