Chelator-enhanced phytoextraction of heavy metals from contaminated soil irrigated by industrial wastewater with the hyperaccumulator plant (Sedum alfredii Hance)

Enhanced phytoextraction of heavy metals using chelating agents and metal-hyperaccumulators has been proposed as an effective approach to removing heavy metals from contaminated soils. The effects of application of EDTA and citric acid (CA) on the growth of Sedum alfredii and its heavy metal uptake and accumulation were investigated using the pot-culture experiments. The application of EDTA (5 and 8 mmol kg(-1)) and CA (5 and 8 mmol kg(-1)) had inhibitory effects on the growth of the plants, resulted in 60.0%, 50.0%, 55.6% and 85.0% reduction in shoot dry biomass, respectively, compared with that in the control. However, the addition of chelators effectively increased the mobility of target heavy metals (Cd, Cu, Pb and Zn) in soils, and significantly enhanced the accumulation of these heavy metals in aerial parts of the plants. The concentrations of Cd, Cu, Pb and Zn increased by 2.37-4.86. 0.09-3.73, 0.33-5.06 and 3.71-6.06 times, respectively, compared with the control. The application of EDTA (5 and 8 mmol kg(-1)) and CA (5 and 8 mmol kg(-1)) could markedly enhance Cd and Zn accumulation. up to 970.6-1463.9 and 3288.3-5376.6 mu g pot(-1) DW, respectively. The most effective method for Cd and Zn accumulation was the treatment of 8 mmol kg(-1) CA. As for Pb, the addition of 5 mmol kg(-1) CA was obtained the maximum value of phytoextraction. (C) 2009 Elsevier B.V. All rights reserved.