Effects of High Acidity on Phase Transitions of an Organic Aerosol

Delanie J. Losey, Emily Jean E. Ott, Miriam Arak Freedman

Research output: Contribution to journalArticlepeer-review

33 Scopus citations


Aerosol particle morphology influences the effect of particles on climate. Recent studies have documented the high acidity found in many ambient aerosol particles. The effect of this acidity on the phase transitions of mixed organic/inorganic aerosol particles has not been addressed. To investigate this effect, six organic compounds and ammonium sulfate were investigated individually with varying amounts of sulfuric acid to determine the role of low pH in the separation, efflorescence, and deliquescence transitions. All phase transitions were affected by the addition of sulfuric acid. This effect was attributed primarily to the change in the identity of the inorganic component as the ammonium/sulfate ratio (ASR) was changed from 2 to 1.5 to 1. The separation relative humidity (SRH) decreased with increasing amounts of sulfuric acid for each system studied, with the largest effect seen in compounds that have a lower SRH when mixed with ammonium sulfate. Control studies without an inorganic salt revealed that for some systems, phase separation occurs for mixtures of sulfuric acid and an organic acid. Overall, it was found that for aerosol particles at low pH (≤0.35) composed of organic acids and inorganic salts, phase separation can be impeded in some cases.

Original languageEnglish (US)
Pages (from-to)3819-3828
Number of pages10
JournalJournal of Physical Chemistry A
Issue number15
StatePublished - Apr 19 2018

All Science Journal Classification (ASJC) codes

  • Physical and Theoretical Chemistry


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