EDTA-enhanced phytoextraction of Cd and Pb in spiked soil with Marigold and associated potential leaching risk
Abstract
EDTA is a common chelating agent used in phytoextraction for enhancing the trace elements uptake from soil to plants. But application of EDTA can cause ground water contamination, which is potentially a risk for human health. In this study EDTA -enhanced phytoextraction of Cd and Pb by Marigold. was evaluated. Application of EDTA could significantly increase Cd and Pb accumulation in the various part of plants, but EDTA addition also increased the Cd and Pb concentration in leached water about 8 to 12 time and 50 to 75 times respectively compared to the control. So, insitu application of EDTA can be potentially risk to ground water contamination with trace elements.
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Introduction
Trace elemen ts (TE) are of major concern in recent time. TEs accumulate in the soil and water due to human activities, such as mining and smelting, industrialization, use of TEs containing waste water, fertilizer, pesticides, fossil fuel burning etc . Some TEs like Zn, Cu, Co, Mn etc. are essential for human health; these elements are used for redox processes as components of various enzymes and for regulation of osmotic pressure in cells [1]. But all TEs are toxic at higher level. Phytoremediation is one most cost eff ective engineering based technologies for remediation of trace elements that use plant and their root -bound microbial communities to remove or absorb trace elements from soil [2]. Phytoextraction is one of the process of phytoremediation defined as the use of the plants that can accumulate, transport and concentrate trace elements from the soil to the roots and aerial plants parts[3]. Natural hyperaccumulating plants are capable to accumulate high amount of TEs, but all hyperaccumulating plants cannot used for phytoextraction because of their low biomass and limited growth [4], [5]. Chelating agent such as ethylenediamintetraacetic acid (EDTA), diethylenetrinitrilopentaacetic acid (DTPA), nitrilotriacetic acid (NTA), ethylenediaminedisuccinate (EDDS) have b een used for long time in nutrient solutions to increase the solubility and plant availability of trace elements [6]. EDTA has been the most effective chelating agent tested because of its less biodegradable nature, but it might cause groundwater contamin ation with TEs [7, 8, 9]. According to Thayalakumaran et al., [6]in situ application of such chelates can increase the risk of water pollution by promoting uncontrolled metal solubilisation and leaching. The objective of this study was to evaluate the effe ct of various concentration of EDTA application to TEs containing spiked soil on plant uptake and leaching of Cd and Pb.
Conclusion
It may be concluded from the present study, that applicat ion of EDTA could increase the mobility of the trace elements in the soil. It also revealed that addition of EDTA could sig nificantly increase the TEs accumulation in the various parts of the marigold compared to the no chelator applied soil . However, TEs accumulation by plant, after application of EDTA was insignificant compared to the amount of TE present into the soil. Most of trace elements were leached with water to the surrounding soil which is a risk of ground water pollution with trace elements.
