Abstract

Most phyto-remediation studies have been conducted merely on a single type of contaminant element without consideration of the influence of other co-existent contaminants. In this study, Vetiveria zizanioides (Linn.) Nash was evaluated in both single and mixed heavy metal (Cd, Pb, Cu and Zn) spiked contaminated soil. The plant growth, metal accumulation and overall efficiency of metal uptake by different plant parts (lower root, upper root, lower tiller and upper tiller) were investigated in detail. The relative growth performance, metal tolerance and phyto-assessment of heavy metal in roots and tillers of Vetiver grass were assessed. Metals in plants were measured using the flame atomic absorption spectrometry (F-AAS) after acid digestion. The root-tiller (R/T) ratio, tolerance index (TI), translocation factor (TF), biological concentration factor (BCF), biological accumulation coefficient (BAC) and metal uptake efficacy were estimated to examine the ability of metal accumulation and translocation in Vetiver grass. No significant difference (p > 0.05) of plant height was observed among all single and mixed heavy metal spiked soils compared with the control. However, significantly higher (p < 0.05) heavy metal (Cd, Pb, Cu and Zn) accumulations were found in roots, tillers and overall total accumulation of the individual spiked metal as compared with other treatments. Vetiver grass grown in the mixed Cd + Pb + Cu + Zn spiked soils accumulated the highest Zn (3322 ± 21.6 mg/kg) followed by Cu (430 ± 11.4 mg/kg), Pb (197 ± 13.5 mg/kg) and Cd (100 ± 0.7 mg/kg). Vetiver grass grown in mixed Cd + Pb, Cu + Zn and Cd + Pb + Cu + Zn spiked soils accumulated higher heavy metal concentrations than from the single spiked soil with the following order of metals: Zn > > Cu > Pb > Cd. Moreover, lower roots and lower tillers of Vetiver grass revealed a strong tendency for greater uptake and accumulation of all four heavy metals in both single and/or mixed spiked contaminated soils.