title: Influence of Humic Acid Complexation with Metal Ions on Extracellular Electron Transfer Activity.
abstract: Humic acids (HAs) can act as electron shuttles and mediate biogeochemical cycles, thereby influencing the transformation of nutrients and environmental pollutants. HAs commonly complex with metals in the environment, but few studies have focused on how these metals affect the roles of HAs in extracellular electron transfer (EET). In this study, HA-metal (HA-M) complexes (HA-Fe, HA-Cu, and HA-Al) were prepared and characterized. The electron shuttle capacities of HA-M complexes were experimentally evaluated through microbial Fe(III) reduction, biocurrent generation, and microbial azoreduction. The results show that the electron shuttle capacities of HAs were enhanced after complexation with Fe but were weakened when using Cu or Al. Density functional theory calculations were performed to explore the structural geometry of the HA-M complexes and revealed the best binding sites of the HAs to metals and the varied charge transfer rate constants (k). The EET activity of the HA-M complexes were in the order HA-Fe > HA-Cu > HA-Al. These findings have important implications for biogeochemical redox processes given the ubiquitous nature of both HAs and various metals in the environment.
authors.affiliation: College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
authors.forename: Shungui
authors.initials: S
authors.lastname: Zhou
authors.affiliation: College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
authors.forename: Shanshan
authors.initials: S
authors.lastname: Chen
authors.affiliation: Guangdong Institute of Eco-environmental and Soil Sciences, Guangzhou 510650, China.
authors.forename: Yong
authors.initials: Y
authors.lastname: Yuan
authors.affiliation: Guangdong Institute of Eco-environmental and Soil Sciences, Guangzhou 510650, China.
authors.forename: Qin
authors.initials: Q
authors.lastname: Lu
mesh_terms: D000535:Aluminum / Q000737:chemistry*; D001674:Bioelectric Energy Sources; D056831:Coordination Complexes / Q000737:chemistry; D003300:Copper / Q000737:chemistry*; D004560:Electricity; D004579:Electron Transport; D004583:Electrons; D004777:Environment; D004785:Environmental Pollutants / Q000737:chemistry*; D006801:Humans; D006812:Humic Substances / Q000032:analysis*; D007501:Iron / Q000737:chemistry*; D010084:Oxidation-Reduction; D020592:Shewanella / Q000737:chemistry* / Q000502:physiology
chemical_list: D056831:Coordination Complexes; D004785:Environmental Pollutants; D006812:Humic Substances; D003300:Copper; D000535:Aluminum; D007501:Iron