Abstract
Phytoremediation of heavy metal contaminated soils is a new technology that is concerned with the use of plants in hyperextracting heavy metals from metalliferous soils. This study investigated the phytoextracting capacity of two weed species Chromoleana odorata and Portulaca oleraceae in pot experiments. Contaminated soils from a public dumpsite located in Orisumbare village on the outskirt of Ibadan were brought to the laboratory and dispensed in 10 litre sized pots and treated as follows:- Portulaca oleraceae planted in polluted soils (PP+), Portulaca oleraceae planted in unpolluted soils (PP-), Chromolaena odorata planted in polluted soils (CP+), Chromolaena odorata planted in unpolluted soils (PP-), Chromolaena odorata and Portulaca oleraceae mixture planted in polluted soils (CPP+), and Chromolaena odorata and Portulaca oleraceae mixture planted in unpolluted soils (CPP-). Each treatment was in three replicates. Levels of selected heavy metals in plant and soil were measured in each treatment at the end of the experiment. Both Chromoleana and Portulaca extracted most of heavy metals from the contaminated soils with Chromoleana extracting significantly (P > 0.05) higher concentration of metals than Portulaca. Sole planted Chromoleana extracted more Mg, Pb, Mn, Cd, As, Zn and Al than Portulaca while Portulaca absorbed more Cu, Fe, Hg, and Cr than Chromoleana from polluted soils. The metal hyperextracting capacities were lowered with mixed weeds compared to each weed which displayed significantly higher (P > 0.05) phytoextracting capacities when planted alone.
Keywords: Dumpsite soil, heavy metals, mixed planting, phyto-extraction, phytoremediation