A passive phytoremediation study to investigate the environmental purification efficacy of water hyacinth (Eichhornia crassipes) was carried out at Mbat-Abiati and Oberekkai Creeks of the Great Kwa River in Southeastern Nigeria. The study assessed the levels of Pb, Zn, Cu, Ni and Co in the water column and underlying sediments (abiotic monitors) in comparison with their levels in E. crassipes (biomonitor). Generally, observed values of heavy metals in sediment and water hyacinth of the two Creeks did not vary significantly (p>0.05), and the sequence that was frequently encountered in the accumulation of the heavy metals was: SEDIMENT>PLANT ROOTS>PLANT LEAVES>WATER. Relative Accumulation Indices (RAI) revealed that the concentration of the heavy metals in the sediments are much higher than values recorded for the waters. This appear normal since sediments are reservoirs for all contaminants and dead organic matter descending from the ecosystem above. The pattern of heavy metal concentrations in the organs of E. crassipes are closely associated with that of its geological substrate (water and sediments). Although zinc displayed the highest accumulation in both root and leaves tissues, and appeared more mobile from roots to leaves than other heavy metal, the bioconcentration factor (BCF) revealed Co as the metal with the highest phytoaccumulation capability in the area, followed by Ni, Cu, Pb and Zn, in that order. Indication from the study is that water hyacinth (Eichhornia crassipes) can effectively absorb and translocate Pb, Zn, Cu, Ni and Co, even when the concentrations of the metals in the abiotic components of the environment is low.
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