Hygroscopicity of Organic Compounds as a Function of Carbon Chain Length and Carboxyl, Hydroperoxy, and Carbonyl Functional Groups.

Autor:	Petters SS; Department of Atmospheric Science, Colorado State University , Fort Collins, Colorado 80523-1371, United States., Pagonis D; Department of Chemistry and Biochemistry, University of Colorado at Boulder , Boulder, Colorado 80309-0216, United States., Claflin MS; Department of Chemistry and Biochemistry, University of Colorado at Boulder , Boulder, Colorado 80309-0216, United States., Levin EJT; Department of Atmospheric Science, Colorado State University , Fort Collins, Colorado 80523-1371, United States., Petters MD; Department of Marine Earth and Atmospheric Sciences, North Carolina State University , Raleigh, North Carolina 27695-8208, United States., Ziemann PJ; Department of Chemistry and Biochemistry, University of Colorado at Boulder , Boulder, Colorado 80309-0216, United States., Kreidenweis SM; Department of Atmospheric Science, Colorado State University , Fort Collins, Colorado 80523-1371, United States.
Jazyk:	angličtina
Zdroj:	The journal of physical chemistry. A [J Phys Chem A] 2017 Jul 13; Vol. 121 (27), pp. 5164-5174. Date of Electronic Publication: 2017 Jun 30.
DOI:	10.1021/acs.jpca.7b04114
Abstrakt:	The albedo and microphysical properties of clouds are controlled in part by the hygroscopicity of particles serving as cloud condensation nuclei (CCN). Hygroscopicity of complex organic mixtures in the atmosphere varies widely and remains challenging to predict. Here we present new measurements characterizing the CCN activity of pure compounds in which carbon chain length and the numbers of hydroperoxy, carboxyl, and carbonyl functional groups were systematically varied to establish the contributions of these groups to organic aerosol apparent hygroscopicity. Apparent hygroscopicity decreased with carbon chain length and increased with polar functional groups in the order carboxyl > hydroperoxy > carbonyl. Activation diameters at different supersaturations deviated from the -3/2 slope in log-log space predicted by Köhler theory, suggesting that water solubility limits CCN activity of particles composed of weakly functionalized organic compounds. Results are compared to a functional group contribution model that predicts CCN activity of organic compounds. The model performed well for most compounds but underpredicted the CCN activity of hydroperoxy groups. New best-fit hydroperoxy group/water interaction parameters were derived from the available CCN data. These results may help improve estimates of the CCN activity of ambient organic aerosols from composition data.
Databáze:	MEDLINE
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