Adsorptive uptake of water by semisolid secondary organic aerosols

Aki Pajunoja, Andrew T. Lambe, Jani Hakala, Narges Rastak, Molly J. Cummings, James F. Brogan, Liqing Hao, Mikhail Paramonov, Juan Hong, Nønne L. Prisle, Jussi Malila, Sami Romakkaniemi, Kari E.J. Lehtinen, Ari Laaksonen, Markku Kulmala, Paola Massoli, Timothy B. Onasch, Neil M. Donahue, Ilona Riipinen, Paul DavidovitsDouglas R. Worsnop, Tuukka Petäjä, Annele Virtanen

Research output: Contribution to journalArticleScientificpeer-review

129 Citations (Scopus)


Aerosol climate effects are intimately tied to interactions with water. Here we combine hygroscopicity measurements with direct observations about the phase of secondary organic aerosol (SOA) particles to show that water uptake by slightly oxygenated SOA is an adsorption-dominated process under subsaturated conditions, where low solubility inhibits water uptake until the humidity is high enough for dissolution to occur. This reconciles reported discrepancies in previous hygroscopicity closure studies. We demonstrate that the difference in SOA hygroscopic behavior in subsaturated and supersaturated conditions can lead to an effect up to about 30% in the direct aerosol forcing - highlighting the need to implement correct descriptions of these processes in atmospheric models. Obtaining closure across the water saturation point is therefore a critical issue for accurate climate modeling.

Original languageEnglish
Pages (from-to)3063-3068
Number of pages6
JournalGeophysical Research Letters
Issue number8
Publication statusPublished - 28 Apr 2015
MoE publication typeA1 Journal article-refereed


  • adsorption
  • aerosol
  • hygroscopicity
  • SOA
  • solubility


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