HR: 1340h
AN: B43A-0890    [Abstracts]
TI: Isotopomer Analysis of N₂O Produced During Waste Water Treatment
AU: * Toyoda, S
EM: toyoda.s.aa@m.titech.ac.jp
AF: Department of Environmental Chemistry and Engineering, Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama, 226-8502, Japan
AU: Fujiwara, A
EM: Akimitsu.Fujiwara@showa-shell.co.jp
AF: Department of Environmental Science and Technology, Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama, 226-8502, Japan
AU: Yoshida, N
EM: naoyoshi@depe.titech.ac.jp
AF: Department of Environmental Chemistry and Engineering, Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama, 226-8502, Japan
AU: Yoshida, N
EM: naoyoshi@depe.titech.ac.jp
AF: Department of Environmental Science and Technology, Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama, 226-8502, Japan
AB: Nitrous oxide (N₂O) is an important trace gas in the atmosphere since it is radiatively active in the troposphere and also a precursor of nitric oxide which catalytically destroys ozone in the stratosphere. Isotopomer ratios (elemental N and O isotope ratios and site-specific N isotope ratios in asymmetric molecule of NNO) have been studied to understand its complex geochemical cycle. Microbial processes such as nitrification and denitrification are the largest N₂O sources, and pure culture incubation studies showed that intramolecular ¹⁵N-site preference (SP) in N₂O can differentiate the two N₂O producing processes, hydroxylamine oxidation and nitrite reduction. However, there have been still few studies on N₂O isotopomer ratios in complex bacterial systems. In this paper, we investigated the isotopomer ratios in N₂O produced in waste water treatment system in order to evaluate characteristics of N₂O emitted from human sewage and to understand N₂O dynamics in microbial consortia (activated sludge). Water and gas samples were collected step by step in two different treatment systems in a sewage plant in Tokyo. High dissolved N₂O concentration (up to 7600%\ saturation) was observed in biological reaction tanks and isotopomer ratios confirmed active N₂O production by microbes. Moreover, isotopomer ratios showed large variations throughout the whole treatment system and suggested that N₂O is produced in settling and chlorination steps as well as biological reaction steps.
DE: 0322 Constituent sources and sinks
DE: 0454 Isotopic composition and chemistry (1041, 4870)
DE: 0469 Nitrogen cycling
DE: 1615 Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 4805, 4912)
DE: 1834 Human impacts
SC: Biogeosciences [B]
MN: 2007 Fall Meeting