@article {37240,
	title = {Secondary organic aerosol from biomass burning phenolic compounds and nitrate radicals can be highly viscous over a wide relative humidity range},
	journal = {ENVIRONMENTAL SCIENCE \& TECHNOLOGY},
	volume = {58},
	year = {2024},
	month = {DEC 2024},
	pages = {21702-21715},
	abstract = {<p>Biomass burning events, including wildfires, can emit large amounts of phenolic compounds such as guaiacol. These phenolic compounds can undergo oxidation by nitrate radicals (NO<sub>3</sub>) to form secondary organic aerosol (SOA). Viscosity and hygroscopicity are key properties that affect SOA\&rsquo;s role in atmospheric chemistry, air quality, climate and public health. However, these properties have not been quantified for SOA formed from the reaction of phenolic compounds with NO<sub>3</sub>. We used the poke-flow technique and a quartz crystal microbalance (QCM) to measure the viscosity and hygroscopicity of SOA particles generated from the reaction of NO<sub>3</sub> with guaiacol, termed guaiacol-NO<sub>3</sub> SOA. The viscosity of this SOA is extremely high (≳5 \&times; 10<sup>7</sup> Pa s) at RH ≲ 70\% and drastically higher than other SOA types previously investigated with the poke-flow technique at RH ≳ 40\%. The high viscosity for guaiacol-NO<sub>3</sub> SOA can be attributed, at least in part, to the low hygroscopicity measured via the QCM. From the viscosity results, we calculated the mixing times of organic molecules within guaiacol-NO<sub>3</sub> SOA. The results suggest that mixing times within this type of SOA exceed 1 h for most tropospheric conditions, with possible implications for predicting the size, mass, and long-range transport of pollutants in phenolic SOA.</p>},
	doi = {10.1021/acs.est.4c06235},
	url = {https://pubs.acs.org/doi/10.1021/acs.est.4c06235},
	author = {Nikkho, S. and Bai, B. and Mahrt, F. and Zaks, J. and Peng, L. and Kiland, K.J. and Liu, P. and Bertram, A.K.}
}
