Combined effects of boundary layer dynamics and atmospheric chemistry on aerosol composition during new particle formation periods

Research output: Contribution to journalArticle

Abstract

Characterizing aerosol chemical composition in response to meteorological changes and atmospheric chemistry is important to gain insights into new particle formation mechanisms. A BAECC (Biogenic Aerosols - Effects on Clouds and Climate) campaign was conducted during the spring 2014 at the SMEAR II station (Station for Measuring Forest Ecosystem-Aerosol Relations) in Finland. The particles were characterized by a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS). A PBL (planetary boundary layer) dilution model was developed to assist interpreting the measurement results. Right before nucleation events, the mass concentrations of organic and sulfate aerosol species were both decreased rapidly along with the growth of PBL heights. However, the mass fraction of sulfate aerosol of the total aerosol mass was increased, in contrast to a decrease for the organic mass fraction. Meanwhile, an increase in LVOOA (low-volatility oxygenated organic aerosol) mass fraction of the total organic mass was observed, in distinct comparison to a reduction of SVOOA (semi-volatile OOA) mass fraction. Our results demonstrate that, at the beginning of nucleation events, the observed sulfate aerosol mass was mainly driven by vertical turbulent mixing of sulfate-rich aerosols between the residual layer and the newly formed boundary layer, while the condensation of sulfuric acid (SA) played a minor role in interpreting the measured sulfate mass concentration. For the measured organic aerosols, their temporal profiles were mainly driven by dilution from PBL development, organic aerosol mixing in different boundary layers and/or partitioning of organic vapors, but accurate measurements of organic vapor concentrations and characterization on the spatial aerosol chemical composition are required. In general, the observed aerosol particles by AMS are subjected to joint effects of PBL dilution, atmospheric chemistry and aerosol mixing in different boundary layers. During aerosol growth periods in the nighttime, the mass concentrations of organic aerosols and organic nitrate aerosols were both increased. The increase in SVOOA mass correlated well with the calculated increase in condensed HOMs' (highly oxygenated organic molecules) mass. To our knowledge, our results are the first atmospheric observations showing a connection between increase in SVOOA and condensed HOMs during the nighttime.

Details

Authors
  • Liqing Hao
  • Olga Garmash
  • Mikael Ehn
  • Pasi Miettinen
  • Paola Massoli
  • Santtu Mikkonen
  • Tuija Jokinen
  • Pontus Roldin
  • Pasi Aalto
  • Taina Yli-Juuti
  • Jorma Joutsensaari
  • Tuukka Petäjä
  • Markku Kulmala
  • Kari E.J. Lehtinen
  • Douglas R. Worsnop
  • Annele Virtanen
Organisations
External organisations
  • University of Eastern Finland
  • University of Helsinki
  • Aerodyne Research, Inc.
  • Finnish Meteorological Institute
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Meteorology and Atmospheric Sciences
Original languageEnglish
Pages (from-to)17705-17716
Number of pages12
JournalAtmospheric Chemistry and Physics
Volume18
Issue number23
Publication statusPublished - 2018
Publication categoryResearch
Peer-reviewedYes