Research
| Title： | Bioelectrochemical modulation of sulfur oxidation enhances arsenic sequestration from sediments in Vallisneria natans through root iron plaque formation and arsenic oxidation: Processes and mechanisms |
|---|---|
| First author： | Xu, Peng; Sun, Linghong; Chen, Yun; Guo, Zhengzheng; Ding, Lei; Wu, Zhenbin |
| Journal： | WATER RESEARCH |
| Years： | 2025 |
| DOI： | 10.1016/j.watres.2025.123975 |
| Abstract： | This study investigated the potential of bioelectrochemical systems (BESs) in enhancing arsenic (As) sequestration in sulfur-rich sediments through submerged aquatic plant Vallisneria natans (V. natans). A mechanism entailing bioelectrogenesis-driven sulfur oxidation, which facilitated root iron plaque (IP) formation and As oxidation, was proposed. A 125-day microcosm study was conducted using coupled plant-BES configurations, comprising: a microbial fuel cell (MFC), microbial electrolysis cells (MECs) with voltage gradients, and V. natans. Results showed that As accumulation and enrichment efficiency in IPs increased proportionally with applied voltage. Electrogenesis enhanced IP development, with MECs outperforming the MFC. Rhizospheric phosphorus deficiency in MFC stimulated radial oxygen loss (ROL) and microbial Fe2+ oxidation for IP formation. In MECs, enhanced endogenous Fe2+ availability and reduction in Sigma H2S concentrations collectively facilitated IP development. As oxidation in MFC was significantly amplified within the rhizosphere by As-oxidizing microorganisms. Sulfite (SO32-), a metabolite of sulfur oxidation, was electrochemically activated in MECs to generate sulfite radicals (SO3 center dot-), demonstrating superior As oxidation efficacy compared to MFC. Metagenomic analysis revealed extracellular electron transfer (EET) efficiency dictated the sulfur oxidation pathway. MFC exhibited FeS2-dominated oxidation with terminal S-0 and intermediate S2O32- formation, suppressing Sigma H2S elimination. MECs displayed insufficient EET, driving Sigma H2S oxidation, FeS consumption, and SO32- accumulation. Intracellular sulfur oxidation pathways differed between systems: the rDsr pathway dominated in MFC, while Hdr process prevailed in MECs. Anode-associated keystone genera responsible for sulfur oxidation were Thiobacillus and Pseudomonas in MFC and MECs, respectively. Iron-oxidizing Collimonas and As oxidizing Halomonas/Acineto-bacter were crucial for mediating IP formation and As oxidization, respectively in MFC. These findings demonstrate that BESs are effective tools for augmenting As sequestration by submerged aquatic plants. This investigation establishes foundational insights for practical implementation of integrated plant-BESs in As-contaminated sediment remediation strategies. |
