Plant growth and development were investigated from selected dumpsites and simulated-polluted soils with heavy metals were investigated using two plant species: Tithonia diversifolia (Td) and Chromolaena odorata (Co). The plant biomass capabilities in phytoremediation of this plant species had not been fully exploited in Nigeria. The effect of soil heavy metal pollution has been of global concern since plants pass these toxic metals to living organisms through the food chain. Therefore, this study was designed to determine the ability of Td tolerance to heavy metal polluted soils.
Three selected dumpsites and control site soil samples of 6.5 kg were used in setting up the experiment for Td and Co. Triplicate from each dumpsite soil samples were assessed for tolerance using Tithonia diversifolia and Chromolaena odorata. Triplicate of the soil samples obtained from IJ were simulated with 10 g/kg each of cadmium (Cd), zinc (Zn), iron (Fe), copper (Cu) and lead (Pb) and used in assessing the tolerance abilities of Td and Co. Composite (2g/kg) of each of the heavy metals were used in simulating three soil samples collected from IJ and tolerance abilities of Td and Co assessed. Triplicate of control experiment was also conducted for Td and Co. Soil analyses were carried out before the experiment in part per million (ppm). Plant biomass was assessed. Data obtained were subjected to one way Analysis of Variance at α0.05.
The most contaminated soil sample before and after the experiment was obtained in soil sample (ppm) from OD with Cd=0.08 and 0.071, Zn=1.92 and 1.85, Fe=8.44 and 6.94, Cu=3.04 and 2.54 and Pb=1 and 0.93 respectively. The highest fresh and dry weights (mg) for Td and Co were recorded in the plants grown in the control soil. The fresh weight (mg) for Td and Co shoots and roots were 110.58 and 52.90; and 48.41 and 7.18respectively. The dry weights (mg) for Td and Co shoots and roots were 20.56 and 4.68; and 16.66 and 0.36 respectively.
This study showed T. diversifolia was capable of tolerating heavy metals than C. odorata in polluted soils. Thus the plants may be good candidates for the cleaning of heavy metals from polluted soils because of their tolerance to toxicity.
Keywords: Phytoremediation, Plant biomass; Soil; T. diversifolia, C. odorata, Heavy metals.