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| Titel |
Spectro-microscopic measurements of carbonaceous aerosol aging in Central California |
| VerfasserIn |
R. C. Moffet, T. C. Rödel, S. T. Kelly, X. Y. Yu, G. T. Carroll, J. Fast, R. A. Zaveri, A. Laskin, M. K. Gilles |
| 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 ; 13, no. 20 ; Nr. 13, no. 20 (2013-10-29), S.10445-10459 |
| Datensatznummer |
250085772
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| Publikation (Nr.) |
 copernicus.org/acp-13-10445-2013.pdf |
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| Zusammenfassung |
| Carbonaceous aerosols are responsible for large uncertainties in climate
models, degraded visibility, and adverse health effects. The Carbonaceous
Aerosols and Radiative Effects Study (CARES) was designed to study
carbonaceous aerosols in the natural environment of the Central Valley,
California, and learn more about their atmospheric formation and aging. This
paper presents results from spectro-microscopic measurements of carbonaceous
particles collected during CARES at the time of a pollution accumulation
event (27–29 June 2010), when in situ measurements indicated an increase in
the organic carbon content of aerosols as the Sacramento urban plume aged.
Computer-controlled scanning electron microscopy coupled with an energy
dispersive X-ray detector (CCSEM/EDX) and scanning transmission X-ray
microscopy coupled with near-edge X-ray absorption spectroscopy (STXM/NEXAFS)
were used to probe the chemical composition and morphology of individual
particles. It was found that the mass of organic carbon on individual
particles increased through condensation of secondary organic aerosol.
STXM/NEXAFS indicated that the number fraction of homogenous organic
particles lacking inorganic inclusions (greater than ~50 nm
equivalent circular diameter) increased with plume age, as did the organic
mass per particle. Comparison of the CARES spectro-microscopic dataset with a
similar dataset obtained in Mexico City during the MILAGRO campaign showed
that fresh particles in Mexico City contained three times as much
carbon as those sampled during CARES. The number fraction of soot particles
at the Mexico City urban site (ranging from 16.6 to 47.3%) was larger
than at the CARES urban site (13.4–15.7%), and the most aged samples
from CARES contained fewer carbon–carbon double bonds. Differences between
carbonaceous particles in Mexico City and California result from different
sources, photochemical conditions, gas phase reactants, and secondary organic
aerosol precursors. The detailed results provided by these
spectro-microscopic measurements will allow for a comprehensive evaluation of
aerosol process models used in climate research. |
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