Characteristics of biogenically-derived aerosols over the Amundsen Sea, Antarctica

To investigate the influence of marine biological activity on aerosols, aerosol and seawater samples were collected over the Southern Ocean (43° S−70° S) and the Amundsen Sea (70° S−75° S) during the ANA06B cruise conducted in the austral summer of 2016 aboard the Korean icebreaker IBR/V Araon. Over the Southern Ocean, atmospheric methanesulfonic acid (MSA) concentration was low (0.10 ± 0.002 µg m−3), whereas its concentration increased sharply up to 0.57 µg m−3 in the Amundsen Sea where Phaeocystis antarctica (P. antarctica), a producer of dimethylsulfide (DMS), was the dominant phytoplankton species. Unlike MSA, mean non-sea-salt sulfate (nss-SO42−) concentration in the Amundsen Sea was comparable to that in the Southern Ocean, suggesting significant influences of marine biological activity on atmospheric sulfur species in the Amundsen Sea. Water-soluble organic carbon (WSOC) concentrations over the Southern Ocean and the Amundsen Sea varied from 0.048–0.16 µgC m−3 and 0.070–0.18 µgC m−3, with averages of 0.087 ± 0.038 µgC m−3 and 0.097 ± 0.038 µgC m−3, respectively. For water-insoluble organic carbon (WIOC), its mean concentrations over the Southern Ocean and the Amundsen Sea were 0.25 ± 0.13 µgC m−3 and 0.26 ± 0.10 µgC m−3, varying from 0.083–0.49 µgC m−3 and 0.12–0.38 µgC m−3, respectively. WIOC was the dominant organic carbon species in both the Southern Ocean and the Amundsen Sea, accounting for 73–75 % of total aerosol organic carbon. WSOC and WIOC were highly enriched in the submicron sea spray particles, especially in the Amundsen Sea where biological productivity was much higher than the Southern Ocean. In addition, the submicron WIOC concentration was quite related to the relative biomass of P. antarctica, suggesting that extracellular polysaccharide mucus produced by P. antarctica was a significant factor affecting atmospheric WIOC concentration in the Amundsen Sea. The fluorescence properties of WSOC investigated using fluorescence excitation-emission matrix coupled with parallel factor analysis (EEM-PARAFAC) revealed that protein-like components were dominant in our marine aerosol samples, representing 69–91 % of the total intensity. Protein-like components also showed positive relationships with the relative biomass of diatoms; however, they were negatively correlated with the relative biomass of P. antarctica. These results suggest that protein-like components are most likely produced as a result of biological processes of diatoms, which play a crucial role in forming the submicron WSOC observed over the Southern Ocean and the Amundsen Sea, and that phytoplankton community structure is a significant factor affecting atmospheric organic carbon species. The results from this study provide significant new observational data on biogenically-derived sulfur and organic carbon species in the Amundsen Sea.