Effects of Synthetic Chelators and Low-Molecular-Weight Organic Acids on Chromium, Copper, and Arsenic Uptake and Translocation in Maize (Zea mays L.)

Chelate-assisted phytoextraction is a promising technique to remediate metal-contaminated soil. Batch and greenhouse experiments were conducted to assess the effects of synthetic chelators (ethylenediaminetetraacetic acid [EDTA], ethylenediaminedisuccinic acid [EDDS], and nitrilotriacetic acid) and low-molecular-weight organic acids (oxalic and citric acids) on the solubilization of copper, chromium, and arsenic (Cu, Cr, and As, respectively) in chromated Cu arsenate (CCA)-contaminated soil and on metal uptake and translocation in maize (Zea mays L.). Chelators significantly enhanced the solubilization of Cr, Cu, and As in the soil and markedly increased their accumulation in plant tissues. Applying 5 and 10 mmol kg(-1) EDDS increased plant Cu uptake by 2.8- and 3.5-fold greater than that in control soil (without chelate applications), respectively. EDTA and citric acid were more efficient for increasing Cr uptake by plant shoots, resulting in 5.0- and 5.5-fold increases, respectively, compared with that in the control. Maximum As uptake was observed in response to a treatment of 10 mmol kg(-1) citric acid, which was 1.9-fold greater than that in control soil. However, translocation factors, phytoextraction efficiencies, and remediation factors indicated that metal uptake was not high enough for successful phytoremediation of CCA-contaminated soil. Our results suggest that EDDS and citric acid as alternatives to EDTA may facilitate phytoextraction of contaminated soil.