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Issue 24, 2013
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A statistical description of the evolution of cloud condensation nuclei activity during the heterogeneous oxidation of squalane and bis(2-ethylhexyl) sebacate aerosol by hydroxyl radicals

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Abstract

The heterogeneous reaction of hydroxyl radicals with chemically reduced organic aerosol comprised of either squalane or bis(2-ethylhexyl) sebacate are used as model systems to examine how cloud condensation nuclei (CCN) activity evolves with photochemical oxidation. Over the course of the reaction, the critical super-saturation evolves both by the formation of new oxygen functional groups and by changes in aerosol size through the formation of gas phase reaction products. A statistical model of the heterogeneous reaction reveals that it is the formation, volatilization, solubility, and surface activity of many generations of oxidation products that together control the average changes in aerosol hygroscopicity. The experimental observations and model demonstrate the importance of considering the underlying population or subpopulation of species within a particle and how they each uniquely contribute to the average hygroscopicity of a multi-component aerosol. To accurately predict changes in CCN activity upon oxidation requires a reduction in the surface tension of the activating droplet by a subpopulation of squalane reaction products. These results provide additional evidence that surface tension–concentration parameterizations based on macroscopic data should be modified for microscopic droplets.

Graphical abstract: A statistical description of the evolution of cloud condensation nuclei activity during the heterogeneous oxidation of squalane and bis(2-ethylhexyl) sebacate aerosol by hydroxyl radicals

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Publication details

The article was received on 24 Jan 2013, accepted on 02 May 2013 and first published on 02 May 2013


Article type: Paper
DOI: 10.1039/C3CP50347J
Citation: Phys. Chem. Chem. Phys., 2013,15, 9679-9693
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    A statistical description of the evolution of cloud condensation nuclei activity during the heterogeneous oxidation of squalane and bis(2-ethylhexyl) sebacate aerosol by hydroxyl radicals

    C. W. Harmon, C. R. Ruehl, C. D. Cappa and K. R. Wilson, Phys. Chem. Chem. Phys., 2013, 15, 9679
    DOI: 10.1039/C3CP50347J

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