Abstract

This study was designed to assess the natural and chemically enhanced phytoextraction ability ofEleusine indica (grass). Three sets of laboratory pot experiment were conducted. Viable seeds of the grass were seeded into one kilogram of the experimental soil placed in each plastic pot. The shoot, root and the experimental soil around root were analyzed for the preliminary levels of the heavy metals: Copper (Cu), Cadmium (Cd), Chromium (Cr), Cobalt (Co) and Lead (Pb). The preliminary levels of Cu, Cd, Cr, Co and Pb in soil, root and shoot of the grass are: soils: 104.5, 5.1, 36.4, 13.3, 14.4 μg/g; root: 164.2, 4.3, 153.9, 11.5 and 24.7 μg/g and shoot of the grass are: 111.5, 2.9, 51.2, 11.1, and 60.7 μg/g respectively. The phytoextraction ability was assessed in terms of its metal transfer factors; Enrichment Coefficient (EC) and Translocation Factor (TF). Copper, Chromium and Lead had the highest EC of 1.07, 1.41 and 4.22 respectively. The levels of the elements in the roots and shoots of the grass at the end of the laboratory experiment shows that more than the bioavailable pool of Cu, Cd, Cr Co and Pb were taken up in the roots with slow translocation of Pb to the shoot: t₁Cu 236.0 to 108.2 μgg^-1 root-shoot; t₂Cu 137.5 to 316.8 μgg-1 root to shoot; t₁Cr 228 to 84.3 μgg^-1 root-shoot; t₂ Cr 242.6 to 94.2 μgg^-1 root to shoot; t₁Pb 54.8 to 176.2 μgg^-1 root to shoot and t₂ Pb 96.0 to 326.0 μgg^-1root-shoot. Inductively Coupled Plasma to Optical Emission Spectroscopy - ICP-OES (for Pb determination) and X-ray fluorescence (XRF) (for Cu, Cr, Cd and Co determination) were used for heavy metals determination in this study. The grass showed relatively good response to EDTA application and the higher levels of Cu and Cr concentration in the root suggested that the grass may be a good metal excluder with the possibility of extracting Pb from contaminated soils.

Key words: Phytoextraction, phytostabilization, pollution, soil, grass, cadmium, cobalt, copper, lead and chromium.