Effect of HEDTA, CDTA, and EGTA Chelates on Remediation of Pb- and Zn-Polluted Soil Using Sunflower and Canola Plants: A Case Study; Soil Around Bama Pb and Zn Mine

Abstract

Background: The soil heavy metal pollution caused by human activities is one of the main environmental problems. Therefore, it is necessary to use appropriate methods to remediate such soils. Objectives: The current study aimed at investigating the effect of Hydroxyl Ethylene Diamine Tetra Acetic Acid (HEDTA), Trans-1,2-Cyclohexylene Dinitrilo Tetra Acetic Acid (CDTA), and Ethylene Glycol-bis (β-Aminoethyl Ether)-N,N,N’,N’-Tetra Acetic Acid (EGTA) chelates on Pb and Zn removal efficiency in a Pb and Zn contaminated soil. Methods: This research was performed as a factorial experiment in a randomized complete block design with four levels of chelate application rate (0, 1.5, 3, and 4.5 mM/kg soil), two levels of chelates application times (one or two weeks before harvesting), and plant types (sunflower or canola). At the end of the experiment, Pb and Zn concentrations in the soil and plant samples were measured and the least significant difference (LSD) test was employed to determine the differences between the means. Results: The effectiveness of studied chelates on the availability of Zn and Pb in soil was in the descending order as HEDTA > CDTA > EGTA. Application of 4.5 mM/kg soil of CDTA chelate under sunflower and canola cultivation caused a significant increase in the availability of Zn and Pb in soil compared to 1.5 mM/kg by 12.2% and 13.3%, respectively. Plant type also had a significant effect on increasing the availability of Pb and Zn in soil. Conclusions: Plant type, application rate, and chelates type are important factors on remediation of heavy metals in contaminated soil. However, the role of physicochemical properties of soil on its heavy metal availability cannot be ignored.