Comparison of EDDS- and EDTA-Assisted Uptake of Heavy Metals by Elsholtzia Haichowensis

Chemically enhanced phyto-extraction has been proposed as an effective approach to removing heavy metals from contaminated soil through use of high biomass plants. A pot study was conducted to investigate the potential of Elsholtzia haichowensis in phytotemediation of contaminated soils with the application of non-degradable (EDTA) and biodegradable chelate (EDDS). The results showed that the treatments with EDDS to soil contaminated with Cu and Zn significantly increased the dry mass yields of shoots in the Elsholtzia haichowensis. It was found that EDDS was more effective than EDTA at increasing the concentrations and total uptake amounts of Cu and Zn in the shoots of Elsholtzia haichowensis. The application of 5 mmol·kg-1 EDDS to soil significantly increased the concentrations and total uptake amounts of Cu in shoots, with maximum levels of 1 322 mg ·kg-1 DW and 855 μg, respectively, which were 90 and 44 fold higher than that in the corresponding control plants to which chelate had not been applied. The concentrations and total uptake amounts of Zn in shoots were also higher in the plants treated with EDDS than in those treated with EDTA. For Pb and Cd, EDDS was less effective than EDTA. The results of metal extraction with chelates showed that EDDS was more effective than EDTA at solubilizing soil Cu and Zn, but for Pb and Cd, that the EDDS was less effective than EDTA.