The effects of rice husk ashes and inorganic fertilizers application rates on the phytoremediation of gold mine tailings by vetiver grass

摘要

This study investigated the effect of rice husk ash (RHA) and inorganic fertilizer on the phytoremediation of heavy metals in mine tailings by vetiver grass (Vetiveria zizanioides L. Nash). The mine tailings were amended with either RHA or iron-coated RHA (Fe-RHA) at 0 or 10% (w/w) application rates and vetiver grass was planted on the tailings. The vetiver grass was fertilized with three rates (0, 50 and 100 kg ha(-1)) of NPK fertilisers during the 75 days growth period in a glasshouse and the experimental units were arranged in a randomized complete block design. At harvest, the shoot and root of the plants were separated and their uptake of As, Cd, Cu, Cr, Pb, Mn and Zn were determined. Application of RHA showed an increase (p < 0.05) in pH and dissolved organic carbon (DOC) contents of the tailings. Growth and total dry biomass of the vetiver was higher (p < 0.05) in the tailings applied with NPK only compared to RHA and Fe-RHA amended tailings Meanwhile, application of NPK and RHA enhanced the heavy metals uptake by vetiver grass from the mine tailings. The plants grown in tailings amended with RHA + 100 kg ha(-1) NPK had the highest (p < 0.05) As uptake while the highest (p < 0.05) Cd and Cr uptake was observed in plants grown on tailings amended with Fe-RHA + 100 kg ha(-1) NPK. The highest (p < 0.05) Cu and Mn uptake were observed in plants grown on tailings receiving only NPK. The bioaccumulation coefficient (BAC) values for all elements were < 1.0 while the biotranslocation coefficient (BTC) for Cu, Cr, Mn, and the bioconcentration (BCF) factor for Zn were > 1.0. The results suggest that the vetiver grass can be recommended for stabilisation of Zn and for phytoextraction of Cr, Cu and Mn from the mine tailings.