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Research Article

Factors controlling surface ozone in the Seoul Metropolitan Area during the KORUS-AQ campaign

Authors:

Heejeong Kim,

Department of Earth and Environmental Sciences, Korea University, Seoul, KR
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Junsu Gil,

Department of Earth and Environmental Sciences, Korea University, Seoul, KR
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Meehye Lee ,

Department of Earth and Environmental Sciences, Korea University, Seoul, KR
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Jinsang Jung,

Center for Gas Analysis, Korea Research Institute of Standards and Science, Daejeon, KR
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Andrew Whitehill,

US EPA, Research Triangle Park, Durham, NC, US
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James Szykman,

US EPA, Research Triangle Park, Durham, NC, US
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Gangwoong Lee,

Department of Environmental Sciences, Hankuk University of Foreign Studies, Yongin, KR
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Deug-Soo Kim,

Department of Environmental Engineering, Kunsan National University, Kunsan, US
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Seogju Cho,

Seoul Metropolitan Government Research Institute of Public Health and Environment, Gyeonggi-do, KR
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Jun-Young Ahn,

Department of Climate and Air Quality, National Institute of Environmental Research, Incheon, KR
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Jinkyu Hong,

Department of Atmospheric Sciences, Yonsei University, Seoul, KR
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Moon-Soo Park

Research Center for Atmospheric Environment, Hankuk University of Foreign Sturdies, Yongin, KR
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Abstract

To understand the characteristics of air quality in the Seoul Metropolitan Area, intensive measurements were conducted under the Korea-United States Air Quality (KORUS-AQ) campaign. Trace gases such as O3, NOx, NOy, SO2, CO, and volatile organic compounds (VOCs), photochemical byproducts such as H2O2 and HCHO, aerosol species, and meteorological variables including planetary boundary layer height were simultaneously measured at Olympic Park in Seoul. During the measurement period, high O3 episodes that exceeded the 90 ppbv hourly maximum occurred on 14 days under four distinct synoptic meteorological conditions. Furthermore, local circulation such as land–sea breeze and diurnal evolution of the boundary layer were crucial in determining the concentrations of precursor gases, including NOx and VOC as well as O3. During such episodes, the nighttime NOx and VOC and daytime UV levels were higher compared to non-episode days. The overall precursor levels and photochemical activity were represented fairly well by variations in the HCHO, which peaked in the morning during the high O3 episodes. This study revealed that toluene was the most abundant VOC in Seoul, and its concentration increased greatly with NOx due to the large local influence under stagnant conditions. When O3 was highly elevated concurrently with PM2.5 under dominant westerlies, NOx and VOCs were relatively lower and CO was noticeably higher than in other episodes. Additionally, the O3 production efficiency was the highest due to a low NOx with the highest NOz/NOy ratio among the four episodes. When westerlies were dominant in transport-south episode, the nighttime concentration of O3 remained as high as 40~50 ppbv due to the minimum level of NOx titration. Overall, the Seoul Metropolitan Area is at NOx-saturated and VOC-limited conditions, which was diagnosed by indicator species and VOC/NOx ratios.

Knowledge Domain: Atmospheric Science
How to Cite: Kim, H., Gil, J., Lee, M., Jung, J., Whitehill, A., Szykman, J., Lee, G., Kim, D.-S., Cho, S., Ahn, J.-Y., Hong, J. and Park, M.-S., 2020. Factors controlling surface ozone in the Seoul Metropolitan Area during the KORUS-AQ campaign. Elem Sci Anth, 8(1), p.46. DOI: http://doi.org/10.1525/elementa.444
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 Published on 25 Aug 2020

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