EDTA-assisted Phytoextraction of Heavy Metals by Amaranthus hybridus Cultivated on Soil Collected from Selected Dumpsites in Ekiti State, Nigeria

Aim: This study was carried out to asses the effectiveness of EDTA phytoextraction of heavy metals by Amaranthus hybridus cultivated on selected dumpsites, with a view to applying the plant in environmental restoration.
Study Design: It is an analytical study.
Place and Duration of Study: This study was conducted at Ekiti State University Ado Ekiti, Nigeria between November 2010 and June 2012.
Methodology: Topsoil (0-15cm) samples were randomly collected on selected dumpsites. The pH and organic matter content of soil were determined prior to plant cultivation. Sequential extraction of heavy metal from soil samples were conducted using modified Tessier’s procedure and acid digestion to obtain the distribution pattern of metals in soil samples. The heavy metals concentration inddiferent sections of plant with or without EDTA application was determined using Flame Atomic Absorption Spectrophotometer, leading to the calculation of phytoextraction efficiency.
Results: The results revealed the mean pH and organic matter content torange from 6.12±0.08-6.56±0.14 and 5.40±0.02-5.84±0.15% respectively; these values were observed to be higher on dumpsites when compared with control sites. Application of synthetic chelate effectively increased the mobility of heavy metals from root to shoot of the plants and as a result of this, concentrations of heavy metals in the shoots of plants were higher in the experiment than control with concentrations of Cd (139.3, 130.0, 126.0 and 123.8 mg/kg; experiment,46.9, 44.2, 37.9 and 23.5 mg/kg; control), Cr (60.5, 59.2, 56.0 and 53.0; experiment, 24.4, 18.2, 16.6 and 16.6 mg/kg; control), Cu (189.3, 180.6,176.0 and 173.8; experiment, 69.0, 66.2, 59.9 and 44.5 mg/kg; control), Pb (227.2, 228.8, 296.3 and 278.7; experiment, 110.1, 104.8, 82.4 and 78.2 mg/kg; control) and Zn (148.0, 129.2, 121.0 and 116.4; experiment, 68.2, 63.0, 58.0 and 51.8 mg/kg; control) at Aba Egbira, Atikankan, Igbehin and Moshood street dumpsites respectively . Bioaccumulation factor (BF), translocation factor (TF) and remediation ratio (RR) were obtained to be greater than one for Cd, Cu and Pb, which showed that these metals were translocated in the plant’s shoot and as a result, Amaranthus hybridus is effective in chelant-assisted phytoextraction.
Conclusion: Therefore, the use of Amaranthus hybridus is advocated as a candidate plant for restoring dumpsites polluted with heavy metals.