Abstract:
The present study assessed potential use of Vetiver grass in phytoremediation of heavy metal contaminated Buriganga riverbank soil. Heavy metal (chromium, lead, copper, and zinc) uptake efficiencies of Vetiver grass without any chelate assistance were observed to be poor when compared to other locally available hyper-accumulators. However, dosing of chelating agent (EDTA or citric acid) significantly improved uptake efficiency of Vetiver grass. Dry mass yield of Vetiver grass grown in contaminated riverbank soil lowered to 70% of the same grown in uncontaminated garden soil. For lower range of dosing (i.e. ≤ 2 mmol/kg of soil) for either chelating agents, growth of Vetiver grass was found to be similar to that observed in contaminated soil. However, with increasing dose of chelating agent (EDTA or citric acid), from 5 to 12 mmol/kg of soil, further gradual reductions of dry mass yields were observed. Synthetic chelate EDTA was found to be more effective than organic chelate citric acid in enhancing chromium, lead, copper, and zinc uptake capacity of Vetiver grass. In case of EDTA, heavy metal uptake efficiency did not increase significantly beyond dosing values of 1–2 mmol/kg of soil. Increasing dose of citric acid (from 0.5–12 mmol/kg of soil) reflected a gradual increase of uptake efficiency. Post harvesting concentrations of heavy metals in riverbank soil exhibited a decreasing trend from initial values. Results also revealed greater mobility for lead, zinc and reduced mobility for chromium and copper in Vetiver grass.
