Rapid heterogeneous oxidation of organic coatings on submicron aerosols

Laboratory studies have found that heterogeneous oxidation can affect the composition and loading of atmospheric organic aerosol particles over time scales of several days, but most studies have examined pure organic particles only. In this study, in order to probe the reactivity of organic species...

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Bibliographic Details
Published in:Geophysical research letters 2017-03, Vol.44 (6), p.2949-2957
Main Authors: Lim, C. Y., Browne, E. C., Sugrue, R. A., Kroll, J. H.
Format: Article
Language:English
Subjects:
aerosol mass spectrometry
Aerosol particles
Aerosols
Ammonium
Ammonium compounds
Ammonium sulfate
Atmospheric aerosols
Atmospheric chemistry
Biological evolution
Carbon
chemical aging
Coated particles
Coatings
Constants
heterogeneous oxidation
Laboratories
morphology
organic aerosol
Organic coatings
Oxidation
Rate constants
Sulfate particles
Sulfates
Time
Valence
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Summary:Laboratory studies have found that heterogeneous oxidation can affect the composition and loading of atmospheric organic aerosol particles over time scales of several days, but most studies have examined pure organic particles only. In this study, in order to probe the reactivity of organic species confined near the particle surface, the rates and products of the OH‐initiated oxidation of pure squalane particles are compared to oxidation of thin coatings of squalane on ammonium sulfate particles. The squalane reaction rate constant shows a linear dependence on the organic surface area‐to‐volume ratio, with rate constants for coated particles up to 10 times larger than for pure particles. Changes in the carbon oxidation state and fraction of particulate carbon remaining show similar enhancements, implying that heterogeneous oxidation may exhibit a stronger effect on the loadings and properties of organic aerosol than previously estimated from laboratory studies. Key Points Organic coatings on aerosol particles are shown to undergo heterogeneous oxidation by OH much more rapidly than pure organic particles The rate constant describing the reactive loss of particulate organic species is linearly dependent on organic surface area‐to‐volume ratio The loading and composition of morphologically complex organic particles may evolve on faster time scales than previously assumed
ISSN:0094-8276
1944-8007
DOI:10.1002/2017GL072585