Gas-Particle Uptake and Hygroscopic Growth by Organosulfate Particles

Paul E. Ohno, Junfeng Wang, Fabian Mahrt, Jonathan G. Varelas, Eleonora Aruffo, Jianhuai Ye, Yiming Qin, Kristian J. Kiland, Allan K. Bertram, Regan J. Thomson*, Scot T. Martin*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

5 Scopus citations


Organosulfate compounds make up a substantial fraction of the particle mass concentration in some regions of the Earth's atmosphere, and organosulfate particles can have sufficiently high viscosity to limit rates of gas-particle interactions. Viscosity varies with relative humidity (RH). Herein, organosulfate particles were exposed to the gas-phase products of α-pinene photooxidation. The gas-particle partitioning of these species was studied from 15 to 70% RH and <1 to 16 ppb NO at 299 K. The uptake of the α-pinene oxidation products increased with the increase in RH, and higher gas-phase NO concentrations resulted in increased particle-phase concentrations of nitrogen compounds. Particle hygroscopicity was examined by optical microscopy. Hygroscopic growth at elevated RH was sufficient to explain the RH-dependent uptake measurements, and kinetic limitations tied to particle viscosity were not observed. The lack of kinetic limitations combined with the Stokes-Einstein equation implied a viscosity much less than 1 × 106 Pa s. This value is consistent with estimated viscosities based on literature parameterizations for water mass fractions in the particles of at least 0.05 at 15% RH. Overall, these results suggest that organosulfate hygroscopicity plays a key role in their viscosity and hence in regulating gas-particle partitioning, thereby simplifying the treatment of atmospheric chemistry and transport of pollutants in models of the Earth's atmosphere. The role of organosulfates is expected to take on increasing importance for projected future emission trends.

Original languageEnglish (US)
Pages (from-to)2481-2490
Number of pages10
JournalACS Earth and Space Chemistry
Issue number10
StatePublished - Oct 20 2022


  • aerosol mass spectrometry
  • aerosol particles
  • environmental chamber
  • gas-particle partitioning
  • hygroscopicity
  • organosulfates
  • viscosity

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Atmospheric Science
  • Space and Planetary Science


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