Phytoremediating Potentials of Sida acuta and Duranta erecta for Lead, Cadmium, Cobalt and Zinc

Recently pollution of the environment has gathered an increased global interest. In this respect, contamination of soils with heavy metals has always been considered a critical challenge in the scientific community. Remediation of soil contaminated by heavy metals is necessary in order to reduce the associated risks, make the land resource available for agricultural production, enhance food security, and scale down land tenure problems. Immobilization, soil washing, and phytoremediation are frequently listed among the best available technologies for cleaning up heavy metal contaminated soils but have been mostly demonstrated in developed countries. Non-edible African plants Sida acuta and Duranta erecta were used to study the absorption of Cadmium, Lead Zinc and Cobalt from soils inoculated with the metal ions.0.1M, 0.5M and 1M solutions of the metal ions were used in the inoculation. The Leaves, stems and roots of Sida acuta and the stems and roots of Duranta erecta were collected in the first instance at six weeks, and then, at ten weeks of planting. Atomic Absorption Spectrophotometer was used to determine the metal ion concentration in the plants parts. Lead was more absorbed by Sida acuta than did Duranta erecta, with the highest absorption of 1.223mg/kg in the former occurring in the roots. Absorption increased as the concentration of the inoculant solution increased, and also on moving from 6 weeks to 10 weeks samples for concentrations less than 0.1M. Cadmium was the only absorbed by Sida acuta, with a highest value of 6.495mg/kg in the roots,. Duranta erecta was poisoned by Cd2+ in all concentrations. Zinc was more absorbed by Duranta erecta than did Sida acuta, with the highest absorption of 7.898mg/kg in the former occurring in stems. Absorption increased as the concentration of the inoculants solution increased. Cobalt was most absorbed by Sida acuta with the highest value of 9.354mg/kg found in the stem. Generally, Phytotoxicity was shown in the plants at inoculants concentration above 0.5M, after 6 weeks except for Duranta erecta inoculated with Zn2+. The tolerance for Lead, Cadmium, and Cobalt by Sida acuta show a good promise for its phytoremediation and recovery.