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| Titel |
Characterization of submicron particles influenced by mixed biogenic and anthropogenic emissions using high-resolution aerosol mass spectrometry: results from CARES |
| VerfasserIn |
A. Setyan, Q. Zhang, M. Merkel, W. B. Knighton, Y. Sun, C. Song, J. E. Shilling, T. B. Onasch, S. C. Herndon, D. R. Worsnop, J. D. Fast, R. A. Zaveri, L. K. Berg, A. Wiedensohler, B. A. Flowers, M. K. Dubey, R. Subramanian |
| 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 ; 12, no. 17 ; Nr. 12, no. 17 (2012-09-11), S.8131-8156 |
| Datensatznummer |
250011438
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| Publikation (Nr.) |
 copernicus.org/acp-12-8131-2012.pdf |
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| Zusammenfassung |
| An Aerodyne high resolution time-of-flight aerosol mass spectrometer
(HR-ToF-AMS) was deployed during the Carbonaceous Aerosols and Radiative
Effects Study (CARES) that took place in northern California in June 2010.
We present results obtained at Cool (denoted as the T1 site of the project)
in the foothills of the Sierra Nevada Mountains, where intense biogenic
emissions are periodically mixed with urban outflow transported by daytime
southwesterly winds from the Sacramento metropolitan area. During this
study, the average mass loading of submicrometer particles (PM1) was
3.0 μg m−3, dominated by organics (80%) and sulfate
(9.9%). The organic aerosol (OA) had a nominal formula of
C1H1.38N0.004OM0.44, thus an average organic
mass-to-carbon (OM/OC) ratio of 1.70. Two distinct oxygenated OA factors
were identified via Positive matrix factorization (PMF) of the
high-resolution mass spectra of organics. The more oxidized MO-OOA (O/C = 0.54)
was interpreted as a surrogate for secondary OA (SOA) influenced by
biogenic emissions whereas the less oxidized LO-OOA (O/C = 0.42) was found
to represent SOA formed in photochemically processed urban emissions. LO-OOA
correlated strongly with ozone and MO-OOA correlated well with two 1st
generation isoprene oxidation products (methacrolein and methyl vinyl
ketone), indicating that both SOAs were relatively fresh. A hydrocarbon like
OA (HOA) factor was also identified, representing primary emissions mainly
due to local traffic. On average, SOA (= MO-OOA + LO-OOA) accounted for
91% of the total OA mass and 72% of the PM1 mass observed at
Cool. Twenty three periods of urban plumes from T0 (Sacramento) to T1 (Cool)
were identified using the Weather Research and Forecasting model coupled
with Chemistry (WRF-Chem). The average PM1 mass loading was
considerably higher in urban plumes than in air masses dominated by biogenic
SOA. The change in OA mass relative to CO (ΔOA/ΔCO) varied
in the range of 5-196 μg m−3 ppm−1, reflecting large variability in
SOA production. The highest ΔOA/ΔCO was reached when air
masses were dominated by anthropogenic emissions in the presence of a high
concentration of biogenic volatile organic compounds (BVOCs). This ratio,
which was 97 μg m−3 ppm−1 on average, was much higher than when
urban plumes arrived in a low BVOC environment (~36 μg m−3 ppm−1)
or during other periods dominated by biogenic SOA
(35 μg m−3 ppm−1). These results demonstrate that SOA
formation is enhanced when anthropogenic emissions interact with biogenic precursors. |
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