The Potential Of Biodegradable Chelating Agents For Phytoremediation Of Heavy Metals From Contaminated Soils

Heavy metal contamination of soils has seriously restricted the sustainable development of human society. Thereby, remediation of the soils contaminated by heavy metal has been a worldwide urgent issue. As an environmental friendly and an in-situ environmental remediation technique for heavy metal contaminated soils, phytoremediation is being a focus in soil remediation research. The chelate-enhanced phytoremediation is an important branch of this area. In recent years, EDTA is the chelating agent which is the most commonly used in the research. Many research found, It promote the remediation efficieny, but It also may lead to the potential environmental risk, because it is nondegradable chelating agent, therefore, to find and research biodegradable chelating agent is a direction in this field. The current research about biodegradable chelating agent for phytoremediation focuses on EDDS. AES, ISA, PESA are biodegradable chelating agents, which are found recently. These chelating agents are Amino-acid derivatives.Through comparing five chelating agents EDTA, EDDS, AES, ISA and PESA, we intend to find their potential which can promote the efficiency of remediation .we found these following conclusions:1. Following AES addition, the desorption of Zn in the contaminated soil is significantly higher than that of other chelating agents. After adding ISA, the desorption of Cu is significant, compared with the control and other chelating agents, except EDDS.The effect of PESA in Pb, Zn, Cu, Cd desorption is not significant.2. In the efficiency experiment of different chelating agents on remediation, The dry weight of shoots added all kinds of chelating agents has a trend of decrese, compared with the control.In the new chelating agents, Following ISA addition, the concentration of Cu in the shoot root and the concentration of Cu which was extracted by water in the soils was significantly greater than that of the control, but it is less than EDDS. After adding AES, the concentration of Zn in the roots and in the soil extracted by water was significantly higher than that of control and other chelating agents. The result in the shoot is obviously than that of the root. Following AES addition, the concentration and the accumulation of Cd in the shoot is higher than that of control, but in the root, it is not obvious. Adding EDTA and EDDS, they can significantly increase the concentratin of Cd in the shoot and root compared with the control and other chelating agents. Following EDTA addition, the concentration of Pb in the shoot and root is higher than that of control and other chelating agent. The effect of PESA on the concentration of heavy metals in plants and the accumulation is not significant compared with the control.3. In hydroponic experiment, the concentration of heavy metals in root reduces obviously as a whole. AES can significantly promote the absorption of Zn, ISA can significantly promote the absorption of Cd. The impact of the chelating agents to the heavy metals in the root is obvious compared with the shoot. The concentration of heavy metals in the shoot is not obvious compared with control.4. In the root, AES, ISA promoted the transportion of Zn, Cu, Cd from the cell wall to the symplasm, EDTA promoted the accumulation of Pb in the cell wall. Following EDTA addition, the concentration of Pb in the apoplast is significantly higher compared to the symplasm, the total content of Pb is significantly higher than that of the control and other chelating agent addition...