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Sources, Occurrence and Characteristics of Fluorescent Biological Aerosol Particles Measured over the Pristine Southern Ocean
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  • Alireza Moallemi,
  • Sebastian Landwehr,
  • Charlotte Mary Robinson,
  • Rafel Simó,
  • Marina Zamanillo,
  • Gang Chen,
  • Andrea Baccarini,
  • Martin Schnaiter,
  • Silvia Henning,
  • Robin L Modini,
  • Martin Gysel-Beer,
  • Julia Schmale
Alireza Moallemi
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Sebastian Landwehr
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Charlotte Mary Robinson
Curtin University
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Rafel Simó
Institut de Ciències del Mar (CSIC)
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Marina Zamanillo
Institut de Ciències del Mar
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Gang Chen
Paul Scherrer Institute
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Andrea Baccarini
Paul Scherrer Institute
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Martin Schnaiter
Karlsruher Institut für Technologie
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Silvia Henning
Institute for Tropospheric Research
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Robin L Modini
Paul Scherrer Institute

Corresponding Author:[email protected]

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Martin Gysel-Beer
Paul Scherrer Institute
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Julia Schmale
École Polytechnique Fédérale de Lausanne
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In this study we investigate the occurrence of primary biological aerosol particles (PBAP) over all sectors of the Southern Ocean (SO) based on a 90-day dataset collected during the Antarctic Circumnavigation Expedition (ACE) in austral summer 2016-2017. Super-micrometer PBAP (1 to 16 µm diameter) were measured by a wide band integrated bioaerosol sensor (WIBS-4). Low (3σ) and high (9σ) fluorescence thresholds are used to obtain statistics on fluorescent and hyper-fluorescent PBAP, respectively. Our focus is on data obtained over the pristine ocean, i.e. more than 200 km away from land. The results indicate that (hyper-)fluorescent PBAP are correlated to atmospheric variables associated with sea spray aerosol (SSA) particles (wind speed, total super-micrometer aerosol number concentration, chloride and sodium concentrations). This suggests that a main source of PBAP over the SO is SSA. The median fraction of fluorescent and hyper-fluorescent PBAP to super-micrometer SSA is 1.6% and 0.13%, respectively. We demonstrate that the fraction of (hyper-)fluorescent PBAP to total super-micrometer particles positively correlates with concentrations of bacteria and several taxa of phytoplankton measured in seawater, indicating that marine biota concentrations modulate the PBAP source flux. We investigate the fluorescent properties of (hyper-)fluorescent PBAP for several events that occurred near land masses. We find that the fluorescence signal characteristics of particles near land is much more variable than over the pristine ocean. We conclude that the source and concentration of fluorescent PBAP over the open ocean is similar across all sectors of the SO.
16 Jun 2021Published in Journal of Geophysical Research: Atmospheres volume 126 issue 11. 10.1029/2021JD034811