11:00 AM - 11:15 AM
[AAS09-08] Seasonal variations and sources of brown carbon in the Asian outflow: co-analyses on the optical properties and organic tracers
Keywords:Brown carbon aerosols, Light absorption property, Organic tracer, Biomass burning
Light-absorbing organic aerosols (brown carbon, BrC) significantly impact climate, yet their detailed chemistry remains unclear. This study delves into the seasonal variations of optical properties of BrC and the relations with organic tracersat Fukue Island, a site in the Asian outflow region, from November 2019 to November 2020. In the study, we collected PM2.5 aerosols, analyzed their light absorption properties (water and methanol extracts), and quantified major organic components (organic carbon, water-soluble organic carbon, organic tracers). We found that the absorption coefficient of BrC exhibit distinct seasonal variations, peaking during winter-spring when influenced by air masses carrying emissions from Asian sources. Water-soluble BrC formation shows a strong correlation with a specific marker for fossil fuel combustion, phthalic acid, suggesting its significant influence during these seasons. Biomass burning emissions, as indicated by another marker, levoglucosan, contribute to BrC formation, particularly in spring. A distinct fraction of BrC, soluble in methanol, is more prevalent in summer, hinting at potential contributions from additional sources such as local biogenic emissions present in air masses from this period. This study sheds light on the seasonal dynamics and diverse sources of BrC in the Asian outflow region, even under generally clean atmospheric conditions. Our findings highlight the role of both anthropogenic and biogenic precursors, as well as potentially unique formation processes occurring in less polluted environments. This knowledge contributes to a better understanding of the complex factors influencing BrC formation and its implications for regional climate and air quality.