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HERO ID
2369609
Reference Type
Journal Article
Title
OH-initiated heterogeneous oxidation of internally-mixed squalane and secondary organic aerosol
Author(s)
Kolesar, KR; Buffaloe, G; Wilson, KR; Cappa, CD
Year
2014
Is Peer Reviewed?
1
Journal
Environmental Science & Technology
ISSN:
0013-936X
EISSN:
1520-5851
Volume
48
Issue
6
Page Numbers
3196-3202
Language
English
PMID
24555558
DOI
10.1021/es405177d
Web of Science Id
WOS:000333776000015
URL
http://pubs.acs.org/doi/10.1021/es405177d
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Abstract
Recent work has established that secondary organic aerosol (SOA) can exist as an amorphous solid, leading to various suggestions that the addition of SOA coatings to existing particles will decrease the reactivity of those particles toward common atmospheric oxidants. Experimental evidence suggests that O3 is unable to physically diffuse through an exterior semisolid or solid layer thus inhibiting reaction with the core. The extent to which this suppression in reactivity occurs for OH has not been established, nor has this been demonstrated specifically for SOA. Here, measurements of the influence of adding a coating of α-pinene+O3 SOA onto squalane particles on the OH-initiated heterogeneous oxidation rate are reported. The chemical composition of the oxidized internally mixed particles was monitored online using a vacuum ultraviolet-aerosol mass spectrometer. Variations in the squalane oxidation rate with particle composition were quantified by measurement of the effective uptake coefficient, γeff, which is the loss rate of a species relative to the oxidant-particle collision rate. Instead of decreasing, the measured γeff increased continuously as the SOA coating thickness increased, by a factor of ∼2 for a SOA coating thickness of 42 nm (corresponding to ca. two-thirds of the particle mass). These results indicate that heterogeneous oxidation of ambient aerosol by OH radicals is not inhibited by SOA coatings, and further that condensed phase chemical pathways and rates in organic particles depend importantly on composition.
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