Electro-assisted phytoremediation (EAPR) of heavy metals in synthetic wastewater using Pistia Stratiotes: Physiological and transcriptomic analyses

Chan, Mun Yee (2026) Electro-assisted phytoremediation (EAPR) of heavy metals in synthetic wastewater using Pistia Stratiotes: Physiological and transcriptomic analyses. PhD thesis, UTAR.

PDF Download (6Mb)

Abstract

Landfilling is the most common solid waste disposal approach, yet leachate treatment remains challenging due to the presence of toxic heavy metals (HMs) that pose long-term environmental and health risks. Electro-Assisted Phytoremediation (EAPR) is an electrical enhancement of phytoremediation designed to improve leachate remediation. EAPR overcomes mass-transfer limitations by driving mobilization of dissolved metals and charged contaminants toward the rhizosphere. The primary aim of this study was to evaluate the HM removal from synthetic leachate between EAPR and non-EAPR, alongside changes in leachate physicochemical parameters, P. stratiotes’s physiological responses, and Pb-induced molecular responses. EAPR significantly reduced Biochemical Oxygen Demand, colour and turbidity (p < 0.05) with minimal impact on growth. HMs accumulated more in roots, with Pb and Fe displaying the highest Bioconcentration Factor and removal efficiency, while translocation factor values less than one implied restricted root transport. Antioxidative enzyme assays revealed increased activity of superoxide dismutase, ascorbate peroxidase, and glutathione reductase in leaves and root peroxidase, suggesting enhanced reactive oxygen species scavenging. RNA-Sequencing revealed Pb stress upregulated root differentially expressed genes (DEGs), but downregulated leaf DEGs, while EAPR reversed this trend. Functional enrichment analysis revealed distinct tissue-specific expression profiles, with Pb stress upregulated DEGs enriched in the Mitogen Activated Protein Kinase (MAPK)-plant, Ras and cyclic adenosine monophosphate (cAMP) signalling pathwayin root, which EAPR suppressed. Ten key regulatory genes were identified through which EAPR reverses Pb-induced transcription across MAPK, hormone and metal-homeostasis signaling networks. Quantitative Reverse Transcription-Polymerase Chain Reaction confirmed MAPK pathway involvement. Overall, EAPR enhanced leachate remediation by improving HM removal and water quality, while maintaining plant growth. Electro-assisted increased root accumulation and antioxidant defenses, while transcriptomic regulation alleviated Pb-induced stress. These findings demonstrate that EAPR is an effective, mechanistically driven strategy for accelerating phytoremediation and support its practical application for leachate treatment.

Actions (login required)