title: Effects of dissolved oxygen and pH on nitrous oxide production rates in autotrophic partial nitrification granules.
abstract: The effects of dissolved oxygen (DO) and pH on nitrous oxide (N2O) production rates and pathways in autotrophic partial nitrification (PN) granules were investigated at the granular level. N2O was primarily produced by betaproteobacterial ammonia-oxidizing bacteria, mainly Nitrosomonas europaea, in the oxic surface layer (<200μm) of the autotrophic PN granules. N2O production increased with increasing bulk DO concentration owing to activation of the ammonia (i.e., hydroxylamine) oxidation in this layer. The highest N2O emissions were observed at pH 7.5, although the ammonia oxidation rate was unchanged between pH 6.5 and 8.5. Overall, the results of this study suggest that in situ analyses of PN granules are essential to gaining insight into N2O emission mechanisms in a granule.
authors: Division of Environmental Engineering, Faculty of Engineering, Hokkaido University, North-13, West-8, Sapporo 060-8628, Japan. Electronic address: englashi@gmail.com.
authors: Rathnayake M L D
authors: RM
authors: Rathnayake
authors: Division of Environmental Engineering, Faculty of Engineering, Hokkaido University, North-13, West-8, Sapporo 060-8628, Japan; Department of Civil Engineering, Nagaoka National College of Technology, 1603-1 Kamitomioka, Nagaoka, Niigata 940-2188, Japan. Electronic address: oshiki@nagaoka-ct.ac.jp.
authors: Mamoru
authors: M
authors: Oshiki
authors: Division of Environmental Engineering, Faculty of Engineering, Hokkaido University, North-13, West-8, Sapporo 060-8628, Japan; Department of Soil, Water, and Climate, BioTechnology Institute, University of Minnesota, 140 Gortner Laboratory of BioChemistry, 1449 Gortner Avenue, St. Paul, MN 55108-1095, USA. Electronic address: ishi0040@umn.edu.
authors: Satoshi
authors: S
authors: Ishii
authors: Transdisciplinary Research Integration Center, National Institute of Polar Research, 10-3 Midori-cho, Tachikawa, Tokyo 190-8518, Japan. Electronic address: segawa@nipr.ac.jp.
authors: Takahiro
authors: T
authors: Segawa
authors: Division of Environmental Engineering, Faculty of Engineering, Hokkaido University, North-13, West-8, Sapporo 060-8628, Japan. Electronic address: qsatoh@eng.hokudai.ac.jp.
authors: Hisashi
authors: H
authors: Satoh
authors: Division of Environmental Engineering, Faculty of Engineering, Hokkaido University, North-13, West-8, Sapporo 060-8628, Japan. Electronic address: sokabe@eng.hokudai.ac.jp.
authors: Satoshi
authors: S
authors: Okabe
mesh_terms: D019149:Bioreactors / Q000382:microbiology*; D006863:Hydrogen-Ion Concentration; D058465:Nitrification; D043370:Nitrosomonas europaea / Q000378:metabolism*; D009609:Nitrous Oxide / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D010100:Oxygen / Q000737:chemistry*
chemical_list: D009609:Nitrous Oxide; D010100:Oxygen
keywords: 16S rRNA gene deep sequencing; Autotrophic partial nitrification granule; Dissolved oxygen effect; N(2)O emissions; N(2)O microsensor