EGUsphere EGUsphere EGUsphere EGUsphere Copernicus Publications Göttingen, Germany 10.5194/egusphere-2026-6595 Wintertime VOC distributions, emission signatures, and transboundary transport over the Seoul Metropolitan Area and the Yellow Sea from airborne observations during ASIA-AQ Lee Jimin 1 Park Jinsoo 2 Kim Jeongho https://orcid.org/0000-0002-4333-9333 3 Chang Limseok https://orcid.org/0000-0002-3296-546X 2 Choi Jinsoo 2 Sung Minyoung 2 Lee Gangwoong https://orcid.org/0000-0002-7929-7921 4 Kim Jeonghwan 4 Kim Jongho 5 Apel Eric C. https://orcid.org/0000-0001-9421-818X 6 Hornbrook Rebecca S. https://orcid.org/0000-0002-6304-6554 6 Blake Donald R. 7 Simpson Isobel J. 7 Wisthaler Armin https://orcid.org/0000-0001-5050-3018 8 9 Wojnowski Wojciech https://orcid.org/0000-0002-8433-917X 8 10 Piel Felix 8 14 Diskin Glenn S. https://orcid.org/0000-0002-3617-0269 11 Miech Jason A. https://orcid.org/0000-0002-0356-5088 11 12 DiGangi Joshua P. https://orcid.org/0000-0002-6764-8624 11 Choi Yonghoon https://orcid.org/0000-0001-6529-4722 11 12 Franchin Alessandro 6 Cho Changmin https://orcid.org/0000-0002-5977-2705 6 Kim Saewung https://orcid.org/0000-0003-4847-3272 13 Lee Meehye https://orcid.org/0000-0001-6622-7003 1 Department of Earth and Environmental Sciences, Korea University, Seoul, South Korea Environmental Satellite Center, National Institute of Environmental Research, Incheon, South Korea Open Space Co., Seoul, South Korea Department of Environmental Science, Hankuk University of Foreign Studies, Yongin, South Korea Environmental Research Center, Hanseo University, Seosan, South Korea Atmospheric Chemistry Observations & Modeling Laboratory, U.S. National Science Foundation National Center for Atmospheric Research, Boulder, CO, USA Department of Chemistry, University of California, Irvine, CA, USA Department of Chemistry, University of Oslo, Oslo, Norway Institute for Ion Physics and Applied Physics, University of Innsbruck, Innsbruck, Austria Department of Analytical Chemistry, Gdańsk University of Technology, Gdańsk, Poland NASA Langley Research Center, Hampton, VA, USA Analytical Mechanics Associates, Hampton, VA, USA Department of Earth Science, University of California, Irvine, CA, USA now at: Advanced Monitoring Solutions (adMS), Oslo, Norway 10 11 2026 2026 1 35 Copyright: © 2026 Jimin Lee et al. 2026 This work is licensed under the Creative Commons Attribution 4.0 International License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/4.0/ This article is available from https://egusphere.copernicus.org/preprints/2026/egusphere-2026-6595/ The full text article is available as a PDF file from https://egusphere.copernicus.org/preprints/2026/egusphere-2026-6595/egusphere-2026-6595.pdf

Volatile organic compounds (VOCs) are key precursors of ozone and secondary organic aerosol, yet wintertime constraints on how local emissions, chemical lifetime, and regional transport jointly shape VOC distributions over Korea and the Yellow Sea remain limited based on airborne measurements. We analyzed proton-transfer-reaction time-of-flight mass spectrometry (PTR-ToF-MS) measurements from 17 Beechcraft 1900D flights during the 2024 Airborne and Satellite Investigation of Asian Air Quality (ASIA-AQ) campaign. The sum of seven VOC species or groups was 2.4 times higher over Seoul than over the Yellow Sea. Toluene, C₈ aromatics, and a methyl ethyl ketone (MEK)-equivalent signal were strongly enhanced in low-altitude, source-influenced air masses, whereas benzene, acetone, and acetonitrile showed weaker regional and vertical contrasts. Seoul-to-Yellow Sea VOC-to-benzene slope ratios generally increased with chemical reactivity, but toluene and C₈ aromatics showed positive deviations, indicating an additional influence of urban aromatic source composition. Yellow Sea observations, supported by NASA DC-8 measurements, indicated continental outflow. An order-of-magnitude transport analysis estimated distance scaled Yellow Sea transport equivalents of approximately 30 % of Seoul benzene emissions in the Clean Air Policy Support System inventory and 6 % for toluene. Wintertime VOC variability is thus species dependent: urban and industrial emissions dominate reactive aromatic VOCs, whereas longer-lived benzene is more sensitive to regional transport. Effective wintertime VOC management requires species-specific strategies considering domestic emissions and regional inflow.

 National Institute of Environmental Research NIER-2024-01-01-005 Korea Environmental Industry and Technology Institute RS-2026-25501457 National Science Foundation 1852977 National Aeronautics and Space Administration 80NSSC23K0818 Österreichische Forschungsförderungsgesellschaft FO999900547 Politechnika Gdańska DEC-4/1/2024/IDUB/II.1b/Am