Heavy Metal Uptake Responses in Plants Grown on Crude Oil-Polluted Soils as Prospects for Phytoremediation

Abstract

The demand and utilization of petroleum products have re-energized its exploration and exploitation globally and this upsurge in world production, refining and distribution of petroleum products have brought with it various problems of environmental pollution, which have effects on the ecosystems. Twenty (24) polyethylene pots each containing 7 kg of sandy loam soil mixed with 50 ml of crude oil, were arranged in the Botanical garden of the University of Ilorin, Nigeria, to assess their ability to phytoextract heavy metals in Crude oil-polluted soil. Seeds of Amaranthus hybridus L., Tithonia diversifolia, Abelmoschus esculentus L. and Zea mays were sown in polyethylene containers containing 7 kg of contaminated or Control soil. The containers were arranged in a complete randomized design. Plants were left to grow for two months with regular watering. Plants were harvested, separated into roots and shoots and oven-dried to constant weight. The experimental plants have been able to reduce the concentration of Cu in both soils by about 45% to 85%, Cr in the soil by 92.08% to 96.72%, as the residual concentration varied between 66.00 mg/kg and 99.00 mg/kg, Cd in the soil was reduced to 4.00 mg/kg and 17 mg/kg which represented 96.8% and 86.4% reduction. Tithonia had the highest Pb reduction in crude oilpolluted soil. Ni concentration was reduced by 85.84% by Tithonia planted in crude oil-polluted soil, 94.59% by Amaranthus hybridus planted in Control soil. These show that all the test plants were good phytoextractors of the metals.

Keywords: Heavy metals, phytoremediation, Amaranthus hybridus L., Tithonia diversifolia, Abelmoschus esculentus L, Zea mays