Volume 16, No. 2, February 2016, Pages 430-441 PDF(1.78 MB)
Supplementary MaterialPDF (126 KB)
Diagnosis of Photochemical Ozone Production Rates and Limiting Factors in Continental Outflow Air Masses Reaching Fukue Island, Japan: Ozone-Control Implications
Yugo Kanaya1, Hiroshi Tanimoto2, Yoko Yokouchi2, Fumikazu Taketani1, Yuichi Komazaki1, Hitoshi Irie1,3, Hisahiro Takashima1,4, Xiaole Pan1,5, Susumu Nozoe2,6, Satoshi Inomata2
1 Department of Environmental Geochemical Cycle Research, Japan Agency for Marine-Earth Science and Technology, 3173-25 Showa-machi, Kanazawa-ku, Yokohama, Japan
2 National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Japan
3 Now at Chiba University, Chiba, Japan
4 Now at Fukuoka University, Fukuoka, Japan
5 Now at Kyushu University, Fukuoka, Japan
6 Now at National Museum of Emerging Science and Innovation, Japan
- In-situ ozone formation in Asian continental outflow reaching western Japan is significant.
- In-situ ozone production is limited mainly by NOx, but occasionally by VOC.
- Control of domestic VOC emissions and NOx effectively avoids further ozone production.
- Uncertainty in radical chemistry mechanism had impact but did not change conclusion.
Asian continental outflow air masses reach western Japan in the springtime, carrying high levels of ozone produced over the Asian continent, and facilitating in-situ production. In this study, in-situ production was highlighted; the rate and limiting factors of net ozone production were diagnosed at Fukue Island, a remote island west of Japan, on 17 days during May–June 2009, when the continental outflow air mass arrived, using an observation-based modeling approach. The average ozone production was estimated to be 6.8 ppb per day. Information on the chemical status of the arriving air mass is important, because it affects how further ozone production in the air mass occurs after precursor addition from Japanese domestic emissions. The main limiting factor of ozone production for such air masses was usually nitrogen oxides (NOx), suggesting that domestic NOx emission control is important in reducing further ozone production. Volatile organic compounds (VOCs) also increased the ozone production rate, and occasionally (14% of time) became the dominant controlling factor. This analysis implies that the VOC reduction legislation recently enacted by the Japanese government should be effective. VOC-limited conditions occurred particularly when the air mass traveled within 6‒8 h, via the Korean Peninsula. The uncertainty in the radical chemistry mechanism governing ozone production had a non-negligible impact, but the main conclusion relevant to policy was not altered. When chain termination was augmented by HO2 + NO/NO2 reactions in the presence of H2O and by heterogeneous loss of HO2 on aerosol particle surfaces, as recently verified or hypothesized, the daily ozone production rate decreased by up to 24%, and the fraction of hours when the VOC-limited condition occurred varied from 14% to 13‒26%.
In-situ ozone photochemistry; East Asia; Policy implications; Observation-based model.