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| Titel |
Chemical evolution of secondary organic aerosol from OH-initiated heterogeneous oxidation |
| VerfasserIn |
I. J. George, J. P. D. Abbatt |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 10, no. 12 ; Nr. 10, no. 12 (2010-06-22), S.5551-5563 |
| Datensatznummer |
250008569
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| Publikation (Nr.) |
 copernicus.org/acp-10-5551-2010.pdf |
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| Zusammenfassung |
| The heterogeneous oxidation of laboratory Secondary Organic Aerosol (SOA)
particles by OH radicals was investigated. SOA particles, produced by
reaction of α-pinene and O3, were exposed to OH radicals in a
flow tube, and particle chemical composition, size, and hygroscopicity were
measured to assess modifications due to oxidative aging. Aerosol Mass
Spectrometer (AMS) mass spectra indicated that the degree of oxidation of
200 nm diameter SOA particles was significantly enhanced due to OH-initiated
oxidation, as evidenced by the increase in the fraction of m/z 44 fragment
of total organic mass concentration (F44). F44 values of the SOA particles,
initially in the range F44=0.04–0.07, increased by up to ΔF44~0.01 under equivalent atmospheric aging timescales of 2 weeks,
assuming a 24-h average OH concentration of 106 cm−3. Particle
O/C ratios calculated from F44 values, initially in the range O/C=0.25–0.35,
rose by a maximum of ΔO/C~0.04 units for 2 weeks of
aging. Particle densities also increased with heterogeneous oxidation,
consistent with the observed increase in the degree of oxidation. Minor
reductions in particle size, with volume losses of up to 10%, were
observed due to volatilization of oxidation products. The SOA particles
activated more readily to form cloud droplets with an increase in the
κ hygroscopicity parameter of up to a factor of two for the
equivalent of 2 weeks of OH atmospheric exposure. These results indicate
that OH heterogeneous oxidation of typical SOA needs to be considered as an
atmospheric organic aerosol aging mechanism, most likely of higher relative
importance away from VOC source regions, where other aging mechanisms are
less dominant. |
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