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Environ Sci Technol

Title:		The Cooling Rate- and Volatility-Dependent Glass-Forming Properties of Organic Aerosols Measured by Broadband Dielectric Spectroscopy
Author(s):		Zhang Y; Nichman L; Spencer P; Jung JI; Lee A; Heffernan BK; Gold A; Zhang Z; Chen Y; Canagaratna MR; Jayne JT; Worsnop DR; Onasch TB; Surratt JD; Chandler D; Davidovits P; Kolb CE;
Address:		"Department of Chemistry , Boston College , Chestnut Hill , Massachusetts 02459 , United States. Aerodyne Research Inc. , Billerica , Massachusetts 01821 , United States. Department of Environmental Sciences and Engineering, Gillings School of Global Public Health , University of North Carolina at Chapel Hill , Chapel Hill , North Carolina 27599 , United States. Department of Chemistry , University of California, Berkeley , Berkeley , California 94720 , United States"
Journal Title:		Environ Sci Technol
Year:		2019
Volume:		20191009
Issue:		21
Page Number:		12366 - 12378
DOI:		10.1021/acs.est.9b03317
ISSN/ISBN:		1520-5851 (Electronic) 0013-936X (Linking)
Abstract:		"Glass transitions of secondary organic aerosols (SOA) from liquid/semisolid to solid phase states have important implications for aerosol reactivity, growth, and cloud formation properties. In the present study, glass transition temperatures (T(g)) of isoprene SOA components, including isoprene hydroxy hydroperoxide (ISOPOOH), isoprene-derived epoxydiols (IEPOX), 2-methyltetrols, and 2-methyltetrol sulfates, were measured at atmospherically relevant cooling rates (2-10 K/min) by thin film broadband dielectric spectroscopy. The results indicate that 2-methyltetrol sulfates have the highest glass transition temperature, while ISOPOOH has the lowest glass transition temperature. By varying the cooling rate of the same compound from 2 to 10 K/min, the T(g) of these compounds increased by 4-5 K. This temperature difference leads to a height difference of 400-800 m in the atmosphere for the corresponding updraft induced cooling rates, assuming a hygroscopicity value (kappa) of 0.1 and relative humidity less than 95%. The T(g) of the organic compounds was found to be strongly correlated with volatility, and a semiempirical formula between glass transition temperatures and volatility was derived. The Gordon-Taylor equation was applied to calculate the effect of relative humidity (RH) and water content at five mixing ratios on the T(g) of organic aerosols. The model shows that T(g) could drop by 15-40 K as the RH changes from <5 to 90%, whereas the mixing ratio of water in the particle increases from 0 to 0.5. These results underscore the importance of chemical composition, updraft rates, and water content (RH) in determining the phase states and hygroscopic properties of organic particles"
Keywords:		Aerosols *Atmosphere *Dielectric Spectroscopy Phase Transition Volatilization;
Notes:		"MedlineZhang, Yue Nichman, Leonid Spencer, Peyton Jung, Jason I Lee, Andrew Heffernan, Brian K Gold, Avram Zhang, Zhenfa Chen, Yuzhi Canagaratna, Manjula R Jayne, John T Worsnop, Douglas R Onasch, Timothy B Surratt, Jason D Chandler, David Davidovits, Paul Kolb, Charles E eng 2019/09/07 Environ Sci Technol. 2019 Nov 5; 53(21):12366-12378. doi: 10.1021/acs.est.9b03317. Epub 2019 Oct 9"