Soil Metal Sorption Characteristics and its Influence on the Comparative Effectiveness of EDTA and Legume Intercrop on the Phytoremediative Abilities of Maize (Zea mays), Mucuna (Mucuna pruriens), Okra (Abelmoschus esculentus), and Kenaf (Hibiscus cannabinus)

Heavy metal pollution in soils and the high costs of remediation necessitate the evaluation of cheaper alternatives. The aim of this experiment was to evaluate Cd, Pb, Zn, and Cu sorption characteristics of three soils and their influence on the comparative effectiveness of EDTA and legume intercrop on the remediative abilities of maize, mucuna, okra, and kenaf. The sorption studies were done using standard procedures. The EDTA-assisted phytoextraction (6mmol kg(-1)) and the cowpea intercrop trials were conducted in triplicate. The metal-spiked soils were planted with maize, kenaf, and mucuna in the EDTA trial and maize, kenaf, and okra were planted in the cowpea intercrop experiment. Cadmium was prefentially sorbed in acid and alkaline soils and Cu in slightly acid soil. Cadmium uptake was significantly lower (P < 0.05) in all the plants. Bioconcentration factors of Pb, Cu, and Zn were higher (P < 0.05) in maize compared with other plants. Phytoremediative ability of the plants in trials were maize > kenaf > mucuna and okra > maize > kenaf, respectively. It was concluded that a legume intercrop can substitute EDTA- assisted phytoextraction to prevent groundwater contamination resulting from high solubility of metals by EDTA.