Experimental Phase Diagram and Its Temporal Evolution for Submicron 2-Methylglutaric Acid and Ammonium Sulfate Aerosol Particles

02 June 2023, Version 1
This content is a preprint and has not undergone peer review at the time of posting.


Liquid–liquid phase separation (LLPS) in aerosol particles is important for the climate system due to its potential to impact heterogeneous chemistry, cloud condensation nuclei, and new particle growth. Our group and others have shown a lower separation relative humidity for submicron particles, but whether the suppression is due to thermodynamics or kinetics is unclear. Herein, we characterize the experimental LLPS phase diagram of submicron 2-methylglutaric acid and ammonium sulfate aerosol particles and compare it to that of supermicron-sized particles. Surprisingly, as the equilibration time of submicron-sized aerosol particles was increased to 60 min, the experimental phase diagram converges with the results for supermicron-sized particles. Our findings indicate that nucleation kinetics are responsible for the observed lower separation relative humidities in submicron aerosol particles. Therefore, experiments and models that investigate atmospheric processes of Aitken and accumulation mode organic aerosol particles may need to consider the temporal evolution of aerosol LLPS.


liquid-liquid phase separation
phase diagram
aerosol particles
cryogenic transmission electron microscopy

Supplementary materials

Supporting Information
The content of this supporting information includes the size distribution of submicron 2MGA+AS particles, example optical images of micrometer droplets at different RH, the measured ERH of submicron inorganic aerosol particles and literature values (KCl, K2SO4), and the AIOMFAC prediction of the viscosity of 2MGA+AS aerosols.


Comments are not moderated before they are posted, but they can be removed by the site moderators if they are found to be in contravention of our Commenting Policy [opens in a new tab] - please read this policy before you post. Comments should be used for scholarly discussion of the content in question. You can find more information about how to use the commenting feature here [opens in a new tab] .
This site is protected by reCAPTCHA and the Google Privacy Policy [opens in a new tab] and Terms of Service [opens in a new tab] apply.