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Carbon Dioxide Diffusivity in Single, Levitated Organic Aerosol Particles.
J Phys Chem Lett ; 10(15): 4484-4489, 2019 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-31295402
ABSTRACT
The diffusivity of molecules relevant to condensed-phase chemistry within viscous secondary organic aerosol (SOA) remains highly uncertain. Whereas there has been an effort to characterize water diffusivity as well as the diffusivity of larger compounds, data are lacking almost entirely for small molecules, such as carbon dioxide (CO2). Here we use photochemically generated CO2 in single particles of aqueous citric acid as a SOA proxy, levitated in an electrodynamic balance, to deduce CO2 diffusivity in the particle with unprecedented accuracy. For medium viscosities at intermediate relative humidities (∼25-40% RH), we find CO2 diffusivities DCO2 ≈ 10-14 m2 s-1, agreeing with the Stokes-Einstein relationship based on current viscosity data but 10 times lower than that for water. Conversely, under dry high-viscosity conditions, we find that DCO2 ≈ 10-16 m2 s-1, which is 10 times higher than for water. We infer that the chemical degradation of atmospheric SOA particles will likely not be limited by CO2 diffusivity.

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Texto completo: Disponível Coleções: Bases de dados internacionais Base de dados: MEDLINE Idioma: Inglês Revista: J Phys Chem Lett Ano de publicação: 2019 Tipo de documento: Artigo País de afiliação: Suíça