Abstract

Otote Tobi Obehi

This study investigated the remediation potential of Ageratum conyzoides and Chromolaena odorata. The
objectives of this research were to: (i) assess the amounts of Pb, Ni and Cr that C. odorata and A. conyzoides
remove from polluted soil (ii) Determine which species best accumulated these heavy metals in their shoot. (iii)
Assess the extent to which Pb, Ni and Cr affected the growth of these species. The plants species were raised
from seeds in a greenhouse using a dumpsite soil containing concentration of heavy metals (Pb, Ni, Cr) above
standard levels. The ability of A. conyzoides and C. odorata to grow and accumulate Pb, Ni and Cr was
assessed for ten weeks. The height of these plants was measured on a weekly basis and the concentration of
heavy metals was determined at the end of the study. C. odorata and A. conyzoides significantly depleted the
amounts of heavy metals in the dumpsite soil. The mean concentration of Pb and Cr were reduced by 17.91%
and 24.04% respectively in the dumpsite soil after the growth of A. conyzoides but there was no significant
difference in Ni concentration. A significant decrease was observed in the concentrations of the Pb (17.39%), Ni
(81.57%) and Cr (54.12%) in the dumpsite soil after the growth of C. odorata. A. conyzoides had a higher
translocation factor for Lead (1.34) than for Chromium (0.15), but it was highest for Ni (6.34). C. odorata also had
a low translocation factor for both Ni (0.47) and Cr (0.57) compared to Pb (5.83). There was no significant
difference in the heights of these species throughout the experiment. Certain plants have the ability to tolerate
heavy metal soil contamination without their growths being significantly impaired as was the case with C.
odorata and A. conyzoides in this study. C. odorata has a higher capability to remove heavy metals from soil
than A. conyzoides. Both species are potential candidates for the bioremediation of Pb and Ni in soils.