Evaluation of soil metal sorption characteristics and heavy metal extractive ability of indigenous plant species in Abeokuta, Nigeria.

Heavy metals sorption behavior and phytoremediative potentials of 14 indigenous tropical plants were evaluated with EDTA and Urea as amendments. Order of preferential sorption of metals are: Pb > Cu > Zn > Cd. In competitive sorption, Pb sorption was increased by 4.98, Cu by 4.24, Zn by 1.40, and Cd by -6 units, implying potential Cd pollution. Order of plants' dry matter accumulation was: Panicum maximum > Zea mays > Amaranthus cruentus > Vetiveria zizanoides > Andropogon tectorum > Tithonia diversifolia > Ocimum gratissimum. Andropogon tectorum and O. gratissimum preferentially translocate Cu and Zn, while V. zizanoides and Z. mays translocated Zn, Cu, and Pb. Amaranthus cruentus, P. maximum, and T. diversifolia preferentially translocated Cu, Pb, Cd, and Zn. The plants are preferentially enriched in Cu and Zn, Pb was selected by P. maximum, T. diversifolia and V. zizanoides. Urea and EDTA enhanced the metal uptake in the plants by 130% and 145%, respectively. Tolerance index (TI) of the plants were reduced by the amendments except in A. tectorum, P. maximum, V. zizanoides, and Z. mays. Amaranthus spinosus, Cassia occidentalis, Pennisetum purpureum, Chromolena odorata, Hibiscus sabdariffa, Hibiscus cannabinus, and Cochorus olitorus could not tolerate the metals.