Evaluation of the phytoremediation potential of lemongrass (cymbopogon citratus) and vetiver grass (chrysopogon zizanioides) in lead contaminated soils of kabwe.

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Mwansa, Mukuka
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The University of Zambia
Heavy metal contamination commonly results from human activities such as mining, and it has become a serious environmental problem. Heavy metals are an important category of the industrial pollutants due to their non-biodegradability. One of the most cost-effective strategies for dealing with heavy metal contamination is phytoremediation. Phytoremediation is a general term for using plants to remove or degrade different kinds of soil pollutants such as heavy metals, pesticides and landfill leachates. In Kabwe, Lead pollution arising from the Lead and Zinc mine tailing has continued up to date because the erosion by wind and water of the tailing materials, has not been remediated. This study evaluated the potential of vetiver and lemongrass for use in phytoremediation of lead (Pb) polluted soils. Soil samples were collected from Kabwe mine tailings and near the mine (Chowa community) for the pot experiments in Pb concentrations of 0 mg/kg, 720.5 mg/kg 865.5 mg/kg, 1510 mg/kg, 1551.8 mg/kg and 1587.7 mg/kg. The test plants (vetiver and lemongrass) were cut to uniform heights (lemongrass 10 cm and vetiver 13 cm). The treatments (Pb concentration) were replicated four times and the study was done for 120 days. Both vetiver and lemongrass grew in all the Pb contaminated and Pb-free soils. There was a decrease in biomass yield with increase in soil Pb concentrations (from 134.0 g in 0 mg/kg to 64.3 g in 1587.7 mg/kg, and from 98.0. g in 0 mg/kg to 52.1 g in 1587 mg/kg for vetiver and lemongrass respectively). Both vetiver and lemongrass accumulated Pb which was more in the roots than the shoots (P < 0.05, bioaccumulation factor < 1). Lemongrass accumulated on average 0.73% Pb in the roots, and 0.13% Pb in the shoot. In contrast, vetiver grass took up on average 0.4% Pb in the roots and 0.29% Pb in the shoots. The translocation factor was less than 1 for both vetiver and lemongrass hence, both plant types may not be suitable for phytoextraction but for phytostabilization and revegetation of the Pb contaminated tailings. Keywords: Lead, Vetiver grass, Lemongrass, Phytoremediation and Mine Tailings.