Phyto-extraction ability of <i>Digitaria exilis</i> (Fonio) to heavy metals

Abstract

Among the different contaminants in the environment, heavy metals are unique due to the fact that they cannot be broken down to non-toxic forms. The research was conducted to determine the remediation potential of Digitaria exilis and to identify the varieties that can tolerate heavy metals contamination. Soil was collected in an Automobile mechanic workshop, Government Reserved Area (GRA) Ado-Ekiti. Five kilograms (5 kg) of soils collected was air dried, sieved and filled into plastic buckets. The experiment was a completely randomized designed with three replicates. Three different accessions of Digitaria exilis namely; Jakah D Iburua (JAK), Dinat D Iburua (DID) and Jiw D Iburau (JIW) were planted. Soils were watered till field moisture capacity. Plant height was determined every two weeks after planting. Soil analysis was carried out to determine the physical and chemical properties before and after the experiment. Heavy metals including Cd, Fe, Zn, Pb, As and Cu were determined in the plant roots and shoots using Atomic Absorption Spectrophotometer (AAS). Accession JAK Bio-accumulated heavy-metals in their root than shoot, consequently, significant high plant height was recorded. However, shoot of accession JAK accumulated 22 % Pb, 46.78% Cu and 37.5% Cd and 20.3% Zn than others whereas accession DID accumulated As than accession JAK. Therefore, accession JAK demonstrated highest phyto-extraction of heavy-metals potentials at the root. Variety JIW has the lowest plant height, root and shoots heavy metals accumulation. Although heavy metals contaminated soil affected the growth of D. exilis, nevertheless accession JAK has the highest productivity under this condition and can be further recommended in phyto-extraction of heavy-metals in polluted sites.

Keywords: Phyto-extraction, Digitaria exilis and Heavy-metals