Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 118, Issue 16, Pages -Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.2102512118
Keywords
aerosol particles; phase behavior; atmospheric chemistry; air quality; climate
Categories
Funding
- Biological Services Laboratory at The University of British Columbia (UBC)
- UBC's Work Learn International Undergraduate Research program [10045]
- Natural Sciences and Engineering Research Council of Canada [RGPIN/04441-2016, RGPIN/04315-2014]
- Alfred P. Sloan Foundation [G-2019-12306]
- Swiss National Science Foundation [P2EZP2_191837]
- US NSF [AGS-1654104]
- Swiss National Science Foundation (SNF) [P2EZP2_191837] Funding Source: Swiss National Science Foundation (SNF)
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Individual atmospheric particles can contain mixtures of primary organic aerosol (POA), secondary organic aerosol (SOA), and secondary inorganic aerosol (SIA), with the potential to have three distinct liquid phases. The presence of these phases is influenced by the elemental oxygen-to-carbon (O:C) ratio of the SOA, impacting equilibration timescales and potential effects on cloud formation and atmospheric chemistry.
Individual atmospheric particles can contain mixtures of primary organic aerosol (POA), secondary organic aerosol (SOA), and secondary inorganic aerosol (SIA). To predict the role of such complex multicomponent particles in air quality and climate, information on the number and types of phases present in the particles is needed. However, the phase behavior of such particles has not been studied in the laboratory, and as a result, remains poorly constrained. Here, we show that POA+SOA+SIA particles can contain three distinct liquid phases: a low-polarity organic-rich phase, a higher-polarity organic-rich phase, and an aqueous inorganic-rich phase. Based on our results, when the elemental oxygen-to-carbon (O:C) ratio of the SOA is less than 0.8, three liquid phases can coexist within the same particle over a wide relative humidity range. In contrast, when the O:C ratio of the SOA is greater than 0.8, three phases will not form. We also demonstrate, using thermodynamic and kinetic modeling, that the presence of three liquid phases in such particles impacts their equilibration timescale with the surrounding gas phase. Three phases will likely also impact their ability to act as nuclei for liquid cloud droplets, the reactivity of these particles, and the mechanism of SOA formation and growth in the atmosphere. These observations provide fundamental information necessary for improved predictions of air quality and aerosol indirect effects on climate.
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