Graduate School of Agriculture, Tokyo University of Agriculture and Technology
Center for Ecological Research, Kyoto University Institute of Agriculture, Tokyo University of Agriculture and Technology
Graduate School of Engineering, Tokyo University of Agriculture and Technology
Department of Chemical Engineering, Tokyo University of Agriculture and Technology Institute of Global Innovation Research, Tokyo University of Agriculture and Technology
Hitachi, Ltd. Department of Applied Chemistry, Faculty of Science and Engineering, Toyo University
Center for Regional Environmental Research, National Institute of Environmental Sciences
Hitachi, Ltd.
Institute of Agriculture, Tokyo University of Agriculture and Technology Project Team for Development of New-generation Research Protocol for Submarine Resources, Japan Agency for Marine-Earth Science and Technology Present address: Institute for Extra-cutting-edge Science and Technology Avant-garde Research (X-star), Super-cutting-edge Grand and Advanced Research (SUGAR) Program, Japan Agency for Marine-Earth Science and Technology
Graduate School of Agriculture, Tokyo University of Agriculture and Technology Center for Ecological Research, Kyoto University
Department of Life Science and Medical Bioscience, Waseda University Present address: Department of Biological Sciences, Faculty of Science and Engineering, Chuo University
Department of Life Science and Medical Bioscience, Waseda University
Department of Life Science and Medical Bioscience, Waseda University
Institute of Agriculture, Tokyo University of Agriculture and Technology
2020 Volume 35 Issue 4 Article ID: ME20031
Isotopic fractionation factors against 15N and 18O during anammox (anaerobic ammonia oxidization by nitrite) are critical for evaluating the importance of this process in natural environments. We performed batch incubation experiments with an anammox-dominated biomass to investigate nitrogen (N) and oxygen (O) isotopic fractionation factors during anammox and also examined apparent isotope fractionation factors during anammox in an actual wastewater treatment plant. We conducted one incubation experiment with high δ18O of water to investigate the effects of water δ18O. The N isotopic fractionation factors estimated from incubation experiments and the wastewater treatment plant were similar to previous values. We also found that the N isotopic effect (15εNXR of –77.8 to –65.9‰ and 15ΔNXR of –31.3 to –30.4‰) and possibly O isotopic effect (18εNXR of –20.6‰) for anaerobic nitrite oxidation to nitrate were inverse. We applied the estimated isotopic fractionation factors to the ordinary differential equation model to clarify whether anammox induces deviations in the δ18O vs δ15N of nitrate from a linear trajectory of 1, similar to heterotrophic denitrification. Although this deviation has been attributed to nitrite oxidation, the O isotopic fractionation factor for anammox is crucial for obtaining a more detailed understanding of the mechanisms controlling this deviation. In our model, anammox induced the trajectory of the δ18O vs δ15N of nitrate during denitrification to less than one, which strongly indicates that this deviation is evidence of nitrite oxidation by anammox under denitrifying conditions.