Japan Geoscience Union Meeting 2016

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

[A-AS12] Atmospheric Chemistry

Thu. May 26, 2016 10:45 AM - 12:15 PM 303 (3F)

Convener:*Hitoshi Irie(Center for Environmental Remote Sensing, Chiba University), Toshinobu Machida(National Institute for Environmental Studies), Hiroshi Tanimoto(National Institute for Environmental Studies), Yoko Iwamoto(Faculty of Science Division I, Tokyo University of Science), Chair:Yugo Kanaya(Department of Environmental Geochemical Cycle Research, Japan Agency for Marine-Earth Science and Technology), Taku Umezawa(National Institute for Environmental Studies)

12:00 PM - 12:15 PM

[AAS12-24] Estimating secondary formation of atmospheric HONO using triple oxygen isotopes as tracers

*Fumiko Nakagawa1, Ray Nakane1, Urumu Tsunogai1, Kengo Sudo1, Izumi Noguchi2, Takashi Yamaguchi2 (1.Graduate School of Environmental Studies, Nagoya University, 2.Hokkaido Institute of Environmental Sciences)

Keywords:HONO, tripple oxygen isotopes, secondary formation, direct emission, atmosphere

The photolysis of nitrous acid (HONO) has been recognized as a potentially important source of OH radicals, which is known as a major oxidant in the atmosphere removing reductive trace gases such as methane and NMHCs. Atmospheric HONO originates from both primary sources (direct emissions) and secondary sources (chemical formation in the atmosphere), however, their contributions to atmospheric HONO production have not been well understood. Here, we determined a triple oxygen isotope of HONO because Δ17O value of HONO produced via “secondary formation” is expected to have highly positive values as those of O3 (Δ17O = +30 ±10‰), while no Δ17O anomaly (Δ17O = 0‰) should be observed for HONO which is emitted directly from various sources on the ground, making it possible to quantify their contribution to the atmospheric HONO production with Δ17O measurement. Periodical sampling of atmospheric HONO was carried out once a month starting from December, 2014 at Hokkaido Institute of Environmental Sciences, Sapporo, Japan. The sample collection period was fixed to one week with a flow rate of 10 L/min. Δ17O value of HONO was determined by combining sensitive determination method on isotope compositions of NO2- (Komatsu et al., 2008; Tsunogai et al., 2010) with filter-pack method (Noguchi et al., 2007) in which to collect HONO as NO2-. The result of daily mean Δ17O value of HONO ranged from +6.9‰ to +10.7‰ through the observation periods. Δ17O value of HONO showed higher value on the day time than night time. The ratios of HONO derived from secondary formation in Sapporo was almost constant throughout the year (day and night : 34±2%, day : 66±8%, night : 21±2%) leading to conclusion that direct emissions are dominant HONO sources in Sapporo.