Sources and Optical Properties of Marine Organic Aerosols Under the Influence of Marine Emissions, Asian Dust, and Anthropogenic Pollutants

The compositions and optical properties of marine organic aerosols (OA) were investigated through shipboard measurements in autumn, spring, and summer over the Yellow Sea and Bohai Sea (YBS), East Asian marginal seas. Water-soluble organics averagely accounted for 45%–75% of the OA mass concentrations and 53%–87% of the OA light absorption at 300 nm (Abs₃₀₀) in the fine particles over the YBS. However, the water-insoluble organic fractions among marine OA increased obviously during periods dominated by dust or marine emissions. Source apportionment and fluorescent components of OA were further analyzed to gain a quantitative insight into the seasonal variations of the marine OA sources. During autumn, the severe influence of continental anthropogenic pollutants led to a dominant presence of water-soluble components in the marine OA. Anthropogenic secondary formation contributed 61% and 82% of the mass concentrations and the Abs₃₀₀ of water-soluble OA in autumn. Asian dust led to an obvious elevation of OA and brown carbon (BrC) light absorption over the YBS in spring, which contributed 70% and 66% of the water-insoluble OA mass and Abs₃₀₀, respectively. In spring, 59% of the OA fluorescence intensity was attributed to the dust-related protein-like organics. During the summer cruise, marine emissions contributed 64%–69% to the mass concentration, 53%–79% to the Abs₃₀₀, and 60% to the fluorescent intensity of OA over the YBS. Our result highlights the distinct sources of marine OA and BrC light absorption across seasons, as well as their vital roles in solar absorption relative to black carbon over marginal seas.