Nitrogen transformation mediated by nitrate-dependent iron oxidation in anoxic freshwater

• Published in: Journal of soils and sediments Vol. 20; no. 2; pp. 1087 - 1096
• Main Authors: Cheng, Boyi, Hua, Yumei, Zhao, Jianwei, Liu, Guanglong, Wan, Xiaoqiong
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.02.2020; Springer Nature B.V
• Subjects: Abundance; Anoxia; Anoxic conditions; Anoxic sediments; Bacteria; Denitrification; Earth and Environmental Science; Emission analysis; Environment; Environmental Physics; Enzymatic activity; Enzyme activity; Enzymes; Freshwater; Freshwater lakes; Incubation period; Inland water environment; Iron; Lake sediments; Lakes; Microorganisms; Nitrate reduction; Nitrates; Nitrogen; Nitrogen cycle; Nitrous oxide; Oxidation; Oxidation process; Reduction; Sec 2 • Physical and Biogeochemical Processes • Research Article; Sediments; Soil Science & Conservation; Transformations; Denitrification; Iron oxidation; Sediment; Nitrate-dependent Fe(II)-oxidising bacteria; Denitrification enzyme activity
• ISSN: 1439-0108; 1614-7480
• DOI: 10.1007/s11368-019-02461-w

Purpose Fe(III) transformation to Fe(II) via the nitrate-dependent iron oxidation process, occurring in anoxic sediments, has an important role in the nitrogen cycle. In this study, laboratory experiments were performed to investigate the denitrification properties driven by nitrate-dependent iron oxidation. Materials and methods A 30-day incubation study of sediments and overlying water from Lake Moshui in Wuhan, China, was conducted in an anoxic condition. The nitrate reduction during the incubation was evaluated by the N 2 O emission and various forms of nitrogen in the overlying water. The denitrification enzyme activity and abundance of nitrate-dependent Fe(II)-oxidising bacteria were determined periodically, and their correlations with nitrogen and iron were analysed to illustrate the denitrification characteristics linked to Fe(II) oxidation in sediments. Results and discussion After the Fe(II) and nitrate input, the decrease of Fe(II) and nitrate concentrations was accompanied by an increase in nitrite and N 2 O production. The contribution of Fe(II) oxidation to the nitrate reduction accounted for 27.7% at the end of the incubation, and the rate of Fe(II) decrease was significantly correlated ( P  < 0.05) with the production of N 2 O. In addition, a positive correlation between denitrification enzyme activity and nitrate concentrations was observed. During incubation, the abundance of nitrate-dependent Fe(II)-oxidising bacteria in the sediment ranged from 1.1 × 10 5  cell g −1 wet sediment to 1.4 × 10 6  cell g −1 wet sediment, and increased with the increase of Fe(II) input concentration. The nitrate reduction coupled with Fe(II) oxidation was mainly mediated by microbial processes. Conclusions Sediment denitrification was enhanced with increasing Fe(II) concentrations, and Fe(II) may play an important role in regulating nitrogen transformation in freshwater lakes.