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Diffusion of Organic Molecules as a Function of Temperature in a Sucrose Matrix (a Proxy for Secondary Organic Aerosol)

TitleDiffusion of Organic Molecules as a Function of Temperature in a Sucrose Matrix (a Proxy for Secondary Organic Aerosol)
Publication TypeJournal Article
Year of Publication2019
AuthorsKiland, KJ, Maclean, AM, Kamal, S, Bertram, AK
JournalTHE JOURNAL OF PHYSICAL CHEMISTRY LETTERS
Volume10
Issue19
Pagination5902-5908
Date PublishedOCT 2019
Abstract

Knowledge of diffusion coefficients as a function of temperature in secondary organic aerosol (SOA) or proxies of SOA is needed to predict atmospheric chemistry, climate, and air quality. We determined diffusion coefficients as a function of temperature of a fluorescent organic molecule in a sucrose matrix (a proxy for SOA). Diffusion coefficients were a strong function of temperature (e.g., at water activity = 0.43, diffusion coefficients decreased by a factor of ∼40 as the temperature decreased by 20 K). Interestingly, the apparent activation energy for diffusion of the fluorescent organic molecule was similar to the apparent activation for diffusion of water in the sucrose matrix. On the basis of these measurements, the mixing time of organic molecules by diffusion in some types of SOA particles will often be >1 h in the free troposphere, if a sucrose matrix is an accurate proxy for these types of SOA.

URLhttps://pubs.acs.org/doi/10.1021/acs.jpclett.9b02182
DOI10.1021/acs.jpclett.9b02182