Japan Geoscience Union Meeting 2015

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Symbol A (Atmospheric and Hydrospheric Sciences) » A-AS Atmospheric Sciences, Meteorology & Atmospheric Environment

[A-AS21] Atmospheric Chemistry

Thu. May 28, 2015 2:15 PM - 4:00 PM 201B (2F)

Convener:*Yousuke Sawa(Oceanography and Geochemistry Research Department, Meteorological Research Institute), Nobuyuki Takegawa(Graduate School of Science and Engineering, Tokyo Metropolitan University), Yugo Kanaya(Research Institute for Global Change, Japan Agency for Marine-Earth Science and Technology), Kenshi Takahashi(Research Institute for Sustainable Humanosphere, Kyoto University), Hiroshi Tanimoto(National Institute for Environmental Studies), Chair:Kei Sato(Regional Atmospheric Environment Section, Center for Regional Environmental Research, National Institute for Environmental Studies)

2:15 PM - 2:30 PM

[AAS21-20] Seasonal variations of nitrogen and oxygen isotopic signature of atmospheric nitrate in coastal Antarctica

*Sakiko ISHINO1, Shohei HATTORI1, Nicolas CAILLON2, Albane BARBERO2, Elsa GAUTIER2, Bruno JOURDAIN2, Susanne PREUNKERT2, Michel LEGRAND2, Naohiro YOSHIDA1, Joel SAVARINO2 (1.Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, Japan, 2.Universite Grenoble Alpes/CNRS, LGGE, F-38000 Grenoble, France)

Keywords:Antarctic, Aerosol, Nitrate, Stable isotopic analysis

Nitrate (NO3-) is the end-product of oxidation of nitrogen oxides (NOX=NO+NO2) in the atmosphere and one of the major ions preserved in Antarctic snow and ice. Therefore, there has been great interest in using concentration and isotopic signature of nitrate in ice cores to reconstruct past atmospheric NOX sources and their oxidation processes to nitrate. For interpretation of nitrate records in Antarctic ice cores, it is necessary to know the long-term changes of concentration and isotopic compositions (15N/14N, 17O/16O and 18O/16O) of nitrate in the atmosphere which deposits on the surface snow. In this study, we present seasonal variation of nitrogen and triple oxygen isotopic composition of nitrate collected at French Antarctic Station Dumont d'Urville (66o40'S, 140o01'E) throughout the year 2011. The significant increase of nitrate concentration during spring and summer period was observed and 15N were depleted in the nitrates, indicating that there was the substantial NOX input to the atmosphere by photolysis of nitrate in the surface snow. In addition, relatively low 17O excess in summer period suggests that NOX oxidation to nitrate by OH radicals was increased. On the other hand, high 17O excess with low concentration in fall and winter period suggests that OH oxidation pathway was depleted and other oxidation pathways related to O3 were dominant. Additionally, the small nitrate increase in winter period might be attributed to the transport of stratospheric nitrate to troposphere due to the formation of polar stratospheric clouds. In the presentation, we will discuss the long-term change of the seasonal trends and compare the result with that of 2001 year-round isotopic analysis using nitrate aerosols at the same station.