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Updated: Apr 26, 2026

Single-throughput Complementary High-resolution Analytical Techniques for Characterizing Complex Natural Organic Matter Mixtures
Published on: January 7, 2019
Dissolved organic matter regulates MnO2-mediated ammonia oxidation through structural transformation and interfacial
Huan Tang1, Xiangyu He1, Wenzhe Wang1
1Key Laboratory of Northwest Water Resource, Environment and Ecology, MOE, Xi'an University of Architecture and Technology, Xi'an, 710055, China; Shaanxi Key Laboratory of Environmental Engineering, Xi'an University of Architecture and Technology, Xi'an, 710055, China; Collaborative Innovation Center of Water Pollution Control and Water Quality Security Assurance of Shaanxi Province, Xi'an University of Architecture and Technology, Xi'an 710055, China.
None:
Abiotic oxidation of ammonium (NH4+) by layered manganese oxides (δ-MnO2) represents an important yet incompletely understood pathway in aquatic nitrogen cycling, particularly under the influence of dissolved organic matter (DOM). Here, we investigate how representative DOM components regulate NH4+ oxidation by layered δ-MnO2 through long-term structural evolution and interfacial reaction processes. Pristine δ-MnO2 initially exhibited negligible NH4+ oxidation capacity but gradually developed reactivity during incubation, accompanied by changes in Mn redox speciation, surface hydroxyl density, and electron-transfer behavior. Among the tested DOM types, humic acid (HA) markedly enhanced NH4+ oxidation, achieving complete conversion to NO3-, whereas other DOM fractions suppressed or altered oxidation pathways. Structural and electrochemical analyses reveal that HA promotes Mn(III) accumulation, stabilizes layered MnO2 structures, and replenishes surface hydroxyl groups via DOM-mediated dissolution-recrystallization, thereby enhancing interfacial electron transfer. In contrast, low-molecular-weight DOM suppresses NH4+oxidation by inducing reductive dissolution of MnO2 and competitively occupying Mn redox-active sites. These findings demonstrate that DOM regulates MnO2-driven NH4+ oxidation through both long-term structural modulation and competitive interactions during the reaction process, highlighting the dynamic role of DOM in abiotic nitrogen transformation in aquatic environments.
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