Parameterization of Thermal Properties of Aging Secondary Organic Aerosol Produced by Photo-Oxidation of Selected Terpene Mixtures

Research output: Contribution to journalArticle

Abstract

Formation and evolution of secondary organic aerosols (SOA) from biogenic VOCs influences the Earth's radiative balance. We have examined the photo-oxidation and aging of boreal terpene mixtures in the SAPHIR simulation chamber. Changes in thermal properties and chemical composition, deduced from mass spectrometric measurements, were providing information on the aging of biogenic SOA produced under ambient solar conditions. Effects of precursor mixture, concentration, and photochemical oxidation levels (OH exposure) were evaluated. OH exposure was found to be the major driver in the long term photochemical transformations, i.e., reaction times of several hours up to days, of SOA and its thermal properties, whereas the initial concentrations and terpenoid mixtures had only minor influence. The volatility distributions were parametrized using a sigmoidal function to determine T-VFR0.5 (the temperature yielding a 50% particle volume fraction remaining) and the steepness of the volatility distribution. T-VFR0.5 increased by 0.3 +/- 0.1% (ca. 1 K), while the steepness increased by 0.9 +/- 0.3% per hour of 1 x 10(6) cm(-3) OH exposure. Thus, aging reduces volatility and increases homogeneity of the vapor pressure distribution, presumably because highly volatile fractions become increasingly susceptible to gas phase oxidation, while less volatile fractions are less reactive with gas phase OH.

Details

Authors
  • Eva U. Emanuelsson
  • T. F. Mentel
  • Ågot Watne
  • C. Spindler
  • B. Bohn
  • T. Brauers
  • H. P. Dorn
  • Åsa M. Hallquist
  • R. Haseler
  • A. Kiendler-Scharr
  • K. P. Muller
  • Håkan Pleijel
  • F. Rohrer
  • F. Rubach
  • E. Schlosser
  • R. Tillmann
  • Mattias Hallquist
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Earth and Related Environmental Sciences
Original languageEnglish
Pages (from-to)6168-6176
JournalEnvironmental Science & Technology
Volume48
Issue number11
Publication statusPublished - 2014
Publication categoryResearch
Peer-reviewedYes
Externally publishedYes