Preprints
https://doi.org/10.5194/acp-2021-729
https://doi.org/10.5194/acp-2021-729

  04 Oct 2021

04 Oct 2021

Review status: this preprint is currently under review for the journal ACP.

An evaluation of new particle formation events in Helsinki during a Baltic Sea cyanobacterial summer bloom

Roseline Cutting Thakur1, Lubna Dada1,2,3, Lisa J. Beck1, Lauriane L. J. Quéléver1, Tommy Chan1, Marjan Marbouti1, Xu-Cheng He1, Carlton Xavier1, Juha Sulo1, Janne Lampilahti1, Markus Lampimäki1, Yee Jun Tham1,11, Nina Sarnela1, Katrianne Lehtipalo1,4, Alf Norkko8,9, Markku Kulmala1,5,6,7, Mikko Sipilä1, and Tuija Jokinen1,10 Roseline Cutting Thakur et al.
  • 1Institute for Atmospheric and Earth System Research/Physics, Faculty of Science, 00014 University of Helsinki, Helsinki, Finland
  • 2School of Architecture, Civil and Environmental Engineering, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
  • 3Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland
  • 4Finnish Meteorological Institute, Helsinki, Finland
  • 5Aerosol and Haze Laboratory, Beijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology, 100089 Beijing, China
  • 6Joint International Research Laboratory of Atmospheric and Earth System Sciences, Nanjing University, 210023 Nanjing, China
  • 7Lomonosov Moscow State University, Faculty of Geography, 119991, Moscow, GSP-1, 1 Leninskiye Gory
  • 8Tvärminne Zoological Station, University of Helsinki, J.A. Palméns väg 260, FI-10900 Hangö, Finland
  • 9Baltic Sea Centre, Stockholm University, Stockholm, Sweden
  • 10Climate & Atmosphere Research Centre (CARE-C), The Cyprus Institute, P.O. Box 27456, Nicosia, CY-1645, Cyprus
  • 11School of Marine Sciences, Sun Yat-Sen University, Zhuhai 519082, China

Abstract. Several studies have investigated New Particle Formation (NPF) events from various sites ranging from pristine locations, including (boreal) forest sites to urban areas. However, there is still a dearth of studies investigating NPF processes and subsequent aerosol growth in coastal yet semi-urban sites, where the tropospheric layer is a concoction of biogenic and anthropogenic gases and particles. The investigation of factors leading to NPF becomes extremely complex due to the highly dynamic meteorological conditions at the coastline especially when combined with both continental and oceanic weather conditions. Herein, we engage a comprehensive study of particle number size distributions and aerosol-forming precursor vapors at the coastal semi-urban site in Helsinki, Finland. The measurement period, 25 June 2019–18 August 2019, was timed with the recurring cyanobacterial summer bloom in the Baltic Sea region and coastal regions of Finland. Our study recorded several regional/local NPF and aerosol burst events during this period. Although the overall anthropogenic influence on Sulfuric Acid (SA) concentrations was low during the measurement period, we observed that the regional or local NPF events, characterized by SA concentrations in the order of 107 molecules per cm−3 occurred mostly when the air mass travelled over the land areas. Interestingly, when the air mass travelled over the Baltic Sea, an area enriched with Algae and cyanobacterial blooms, high Iodic Acid (IA) concentration coincided with an aerosol burst or a spike event at the measurement site. Further, SA-rich bursts were seen when the air mass travelled over the Gulf of Bothnia, enriched with cyanobacterial blooms. The two most important factors affecting aerosol precursor vapor concentrations, and thus the aerosol formation, were (1) the type of phytoplankton species and intensity of bloom present in the coastal regions of Finland/ Baltic Sea and (2) the wind direction. During the events, most of the growth of sub-3 nm particles was probably due to SA, rather than IA or MSA, however much of the particle growth remained unexplained indicative of the strong role of organics in the growth of particles, especially in the 3–7 nm particle size range. Further studies are needed to explore the role of organics in NPF events and the potential influence of cyanobacterial blooms in coastal locations.

Roseline Cutting Thakur et al.

Status: open (until 18 Nov 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse

Roseline Cutting Thakur et al.

Roseline Cutting Thakur et al.

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Short summary
Every year intense cyanobacterial and macroalgal blooms occur in the Baltic Sea and in the coastal areas surrounding Helsinki, yet no studies address the impact of biogenic emissions from these blooms on the gas-vapor concentrations, which in turn could influence new particle formations. This is the first of its kind study, which addresses the chemistry driving the new particle formations (NPF) during a bloom period in this region, highlighting the role of biogenic sulphuric acid and iodic acid.
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