Biomass burning organic aerosol (BBOA) from wildfires has multiple phases and is more viscous than laboratory generated BBOA

07 May 2024, Version 1
This content is a preprint and has not undergone peer review at the time of posting.


Biomass burning organic aerosol (BBOA) is a major contributor to organic aerosol in the atmosphere. The impacts of BBOA on climate and health depend strongly on their physicochemical properties, including viscosity and phase behaviour (number and types of phases); these properties, and their relationships to BBOA chemistry, are not yet fully characterized. We collected BBOA field samples during the 2021 British Columbia wildfire season to constrain the viscosity and phase behaviour at a range of relative humidities, and compared them to laboratory generated BBOA made from smoldering pine wood. Particles from all samples exhibited two-phased behaviour with a higher polarity hydrophilic core and a lower polarity hydrophobic shell. We used the poke-flow viscosity technique to estimate the viscosity of the particles. We found that both phases of the field samples had viscosities >108 Pa s at relative humidities up to 50%, which is more viscous than any laboratory generated BBOA or BBOA proxies previously measured. Aerosol mass spectrometry showed that the field samples were more oxidized than those generated in the lab, which is a likely explanation for the higher viscosity. The two phases and high viscosity have implications for how BBOA should be treated in atmospheric models


biomass burning
organic aerosol
phase behaviour
phase separation

Supplementary materials

Supporting Information
Additional figures: maps showing the locations of satellite-detected forest fires and calculated air back-trajectories during field sampling, air quality station data, and a schematic of the experimental setup.


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.