Factors controlling atmospheric DMS and its oxidation products (MSA and nssSO₄^2-) in the aerosol at Terra Nova Bay, Antarctica

Silvia Becagli , Elena Barbaro , Simone Bonamano , Laura Caiazzo , Alcide Di Sarra , Matteo Feltracco , Paolo Grigioni , Jost Heintzenberg , Luigi Lazzara , Michel Legrand (1, 2) , Alice Madonia , Marco Marcelli , Chiara Melillo , Daniela Meloni , Caterina Nuccio , Giandomenico Pace , Ki-Tae Park , Suzanne Preunkert (1) , Mirko Severi , Marco Vecchiato , Roberta Zangrando , Rita Traversi

1 IGE - Institut des Géosciences de l’Environnement
2 LISA (UMR_7583) - Laboratoire Interuniversitaire des Systèmes Atmosphériques

This paper presents the results of simultaneous high time-resolution measurements of biogenic aerosol (methane sulfonic acid (MSA), non-sea salt sulfate nssSO₄^2-) with its gaseous precursor dimethylsulfide (DMS), performed at the Italian coastal base Mario Zucchelli Station (MZS) in Terra Nova Bay (MZS) during two summer campaigns (2018-2019 and 2019-2020). Data on atmospheric DMS concentration are scarce, especially in Antarctica. The DMS maximum at MZS occurs in December, one month earlier than at other Antarctic stations. The maximum of DMS concentration is connected with the phytoplanktonic senescent phase following the bloom of Phaeocystis antarctica that occurs in the polynya when sea ice opens up. The second plankton bloom occurs in January and, despite the high dimethylsufoniopropionate (DMSP) concentration in seawater, atmospheric DMS remains low, probably due to its fast biological turnover in seawater in this period. The intensity and timing of the DMS evolution during the two years suggest that only the portion of the polynya close to the sampling site produces a discernible effect on the measured DMS. The closeness to the DMS source area and the occurrence of air masses containing DMS and freshly formed oxidation products allow us to study the kinetic of biogenic aerosol formation and the reliable derivation of the branch ratio between MSA and nssSO₄^2- from DMS oxidation that is estimated to be 0.84±0.06. Conversely, for aged air masses with low DMS content, an enrichment of nssSO₄^2- with respect to MSA, is observed. We estimate that the mean contribution of freshly formed biogenic aerosol to PM₁₀ is 17 % with a maximum of 56 %. The high contribution of biogenic aerosol to the total PM₁₀ mass in summer in this area highlights the dominant role of the polynya on biogenic aerosol formation. Finally, due to the regional and year-to-year variability of DMS and related biogenic aerosol formation, we stress the need for long-term measurements of seawater and atmospheric DMS and biogenic aerosol along the Antarctic coast and in the Southern Ocean.

Domaines: Planète et Univers [physics]

Silvia Becagli, Elena Barbaro, Simone Bonamano, Laura Caiazzo, Alcide Di Sarra, et al.. Factors controlling atmospheric DMS and its oxidation products (MSA and nssSO₄^2-) in the aerosol at Terra Nova Bay, Antarctica. Atmospheric Chemistry and Physics, 2022, 22, pp.9245-9263. ⟨10.5194/acp-22-9245-2022⟩. ⟨insu-03839375⟩