Comparison of EDTA- and Citric Acid-Enhanced Phytoextraction of Heavy Metals in Artificially Metal Contaminated Soil by Typha Angustifolia

Abstract

A pot experiment was conducted to study the performance of EDTA and citric acid (CA) addition in improving phytoextraction of Cd, Cu, Pb, and Cr from artificially contaminated soil by T. angustifolia. T. angustifolia showed the remarkable resistance to heavy metal toxicity with no visual toxic symptom including chlorosis and necrosis when exposed to metal stress. EDTA-addition significantly reduced plant height and biomass, compared with the control, and stunted plant growth, while 2.5 and 5 mM CA addition induced significant increases in root dry weight. EDTA, and 5 and 10 mM CA significantly increased shoot Cd, Pb, and Cr concentrations compared with the control, with EDTA being more effective. At final harvest, the highest shoot Cd, Cr, and Pb concentrations were recorded in the treatment of 5 mM EDTA addition, while maximal root Pb concentration was found at the 2.5 mM CA treatment. However, shoot Cd accumulation in the 10 mM CA treatment was 36.9% higher than that in 2.5 mM EDTA, and similar with that in 10 mM EDTA. Shoot Pb accumulation was lower in 10 mM CA than that in EDTA treatments. Further, root Cd, Cu, and Pb accumulation of CA treatments and shoot Cr accumulation in 5 or 10 mM CA treatments were markedly higher than that of control and EDTA treatments. The results also showed that EDTA dramatically increased the dissolution of Cu, Cr, Pb, and Cd in soil, while CA addition had less effect on water-soluble Cu, Cr, and Cd, and no effect on Pb levels. It is suggested that CA can be a good chelator candidate for T. angustifolia used for environmentally safe phytoextraction of Cd and Cr in soils.

KEY WORDS:

• CA (citric acid)
• EDTA
• heavy metal
• phytoextraction
• Typha angustifolia

ACKNOWLEDGMENTS

This project was funded by the National Natural Science Foundation of China (30671256). We appreciate Miss Fang Wang, Miss Jing Dong, and Mr. Yue Cai, Agronomy Department of Zhejiang University, for their helpful assistance during the experimental work.

Notes

^[1]Treatments of control, EDTA 2.5, EDTA 5, and EDTA 10 correspond to 0, 2.5, 5, and 10 mM EDTA, respectively, and CA 2.5, CA 5, and CA 10 correspond to 2.5, 5, and 10 mM CA

^[2]Means for the same measurement in a particular column followed by the same letter are not significantly different according to Duncan's multiple range test at p = 0.05.

^[1]Treatments of control, EDTA 2.5, EDTA 5, and EDTA 10 correspond to 0, 2.5, 5, and 10 mM EDTA, respectively, and CA 2.5, CA 5, and CA 10 correspond to 2.5, 5, and 10 mM CA.

^[2]Means for the same measurement in a particular column followed by the same letter are not significantly different according to Duncan's multiple range test at p = 0.05.