A study of EDDS enhanced phytoremediation by ryegrass grown in E-waste soils

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A study of EDDS enhanced phytoremediation by ryegrass grown in E-waste soils


Author: Yang, Zi
Title: A study of EDDS enhanced phytoremediation by ryegrass grown in E-waste soils
Degree: M.Sc.
Year: 2012
Subject: Soil remediation.
Soils -- Heavy metal content.
Hong Kong Polytechnic University -- Dissertations
Department: Dept. of Civil and Structural Engineering
Pages: xi, 101 leaves : ill. ; 30 cm.
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b2512019
URI: http://theses.lib.polyu.edu.hk/handle/200/6533
Abstract: The main objective of this research was to investigate the feasibility of ryegrass as a potential phytoremediation approach for heavy metal contaminated soil with the aid of 3 mmol kg⁻¹ EDDS. The soil solution and plant biomass were collected for the laboratory analyses of total organic carbon, cation and anion concentrations and metal concentrations. The dry weights of the shoots and roots of ryegrass were measured at Day 30 after the EDDS treatment. The percentage of the shoots to total weight increased from 64% to 73%, but the percentage of the roots to total weight decreased from 36% to 27%. The TOC concentration was greatly enhanced with the EDDS application, reached the highest level of 2397 mg 1⁻¹ in ryegrass pots, which was 21-fold than that of the control group, proving that the 3 mmol kg⁻¹ EDDS had a considerable capability to increase the TOC concentration in the soil. The ion analysis showed that the concentrations of Ca²⁺ and Mg²⁺ slightly decreased with the EDDS treatment which accorded with the results of metal analysis of Ca and Mg. However, the Cu concentration in soil solution was dramatically increased from 3.361 mg 1⁻¹ to 647.150 mg 1⁻¹ with the EDDS treatment. The increment of Zn concentration reached to 305-fold in the bare pots and 179-fold in the ryegrass pots as compared with that of the control group. The increase of soluble Pb and Cd concentrations were also observed in the soil solution with the EDDS treatment. The enhanced uptakes of Cu, Pb, Zn and Cd by ryegrass were mostly found in the roots. The accumulated concentrations of Cu in the shoots and roots of ryegrass reached 139.518 mg kg⁻¹ and 456.326 mg kg⁻¹ respectively, which were 6-fold and 2-fold than the control group. EDDS was less effective on Zn and Pb uptake as compared with Cu although the enhanced uptake was also observed. The removal percentage of Cu was increased from 2.27 % to 4.68 % with the EDDS treatment. It indicated that the combination of ryegrass and EDDS have a potential remediation ability in Cu contaminated soil.

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