[A-AS08] Atmospheric Chemistry

[AAS08-P15] Optical and Chemical Properties of Brown Carbon in PM_2.5 at Yongin, Korea, Downwind of Seoul, during Winter 2026

*Minseo Lee¹, Chisung Yun¹, Yongjoo Choi¹, Greem Lee² (1.Department of Environmental Sciences, Hankuk University of Foreign Studies, 2.Air Quality Environment Research Division, National Institute of Environmental Research, Incheon, Republic of Korea)

Keywords:

Brown Carbon,Light-absorption properties,PAHs

Brown carbon (BrC) is one of the organic aerosol components that exhibits strong wavelength-dependent light absorption in the ultraviolet–visible spectral range and contributes to atmospheric radiative effects. BrC is mainly produced by biomass and fossil fuel combustion as well as secondary oxidation of volatile organic compounds, and its light absorption characteristics vary with chemical composition. The optical properties of BrC in water-soluble organic carbon (WSOC) and methanol-soluble organic carbon (MSOC) are generally evaluated using indicators such as the light absorption coefficient (Mm^-1) and the absorption Ångström exponent (AAE). This study focused on the behavior of BrC in PM_2.5 during December 2025–March 2026 at Yongin (37.33°N, 127.26°E, 113 m), downwind of Seoul. The light absorption of BrC in WSOC and MSOC were obtained using a UV–Vis spectrophotometer (UV-1280, Shimadzu). WSOC concentration was measured by a total organic carbon analyzer (TOC-LCPH, Shimadzu). OC and MSOC concentrations were analyzed using a DRI Model 2015 thermal–optical reflectance (TOR) analyzer following the IMPROVE-A protocol. GC/MS (6890 Series, Agilent) was used to analyze molecular-level organic compounds, including polycyclic aromatic hydrocarbons (PAHs). This study aims to examine how differences in chemical composition are associated with variations in BrC light absorption during winter. By elucidating the emission sources of BrC and key factors influencing BrC light absorption, this study provides scientific evidence for mitigating strategies to reduce the BrC and climate changes.