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| Titel |
Chemistry of new particle growth in mixed urban and biogenic emissions – insights from CARES |
| VerfasserIn |
A. Setyan, C. Song, M. Merkel, W. B. Knighton, T. B. Onasch, M. R. Canagaratna, D. R. Worsnop, A. Wiedensohler, J. E. Shilling, Q. Zhang |
| 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 ; 14, no. 13 ; Nr. 14, no. 13 (2014-07-01), S.6477-6494 |
| Datensatznummer |
250118845
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| Publikation (Nr.) |
 copernicus.org/acp-14-6477-2014.pdf |
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| Zusammenfassung |
| Regional new particle formation and growth events (NPEs) were observed on
most days over the Sacramento and western Sierra foothills area of California
in June 2010 during the Carbonaceous Aerosols and Radiative Effect Study
(CARES). Simultaneous particle measurements at both the T0 (Sacramento, urban
site) and the T1 (Cool, rural site located ~40 km northeast of
Sacramento) sites of CARES indicate that the NPEs usually occurred in the
morning with the appearance of an ultrafine mode at ~15 nm (in
mobility diameter, Dm, measured by a mobility particle size
spectrometer operating in the range 10-858 nm) followed by the growth of
this modal diameter to ~50 nm in the afternoon. These events were
generally associated with southwesterly winds bringing urban plumes from
Sacramento to the T1 site. The growth rate was on average higher at T0
(7.1 ± 2.7 nm h−1) than at T1 (6.2 ± 2.5 nm h−1),
likely due to stronger anthropogenic influences at T0. Using a
high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS), we
investigated the evolution of the size-resolved chemical composition of new
particles at T1. Our results indicate that the growth of new particles was
driven primarily by the condensation of oxygenated organic species and, to a
lesser extent, ammonium sulfate. New particles appear to be fully neutralized
during growth, consistent with high NH3 concentration in the region.
Nitrogen-containing organic ions (i.e., CHN+, CH4N+,
C2H3N+, and
C2H4N+) that are indicative of the presence of
alkyl-amine species in submicrometer particles enhanced significantly during
the NPE days, suggesting that amines might have played a role in these
events. Our results also indicate that the bulk composition of the ultrafine
mode organics during NPEs was very similar to that of anthropogenically
influenced secondary organic aerosol (SOA) observed in transported urban
plumes. In addition, the concentrations of species representative of urban
emissions (e.g., black carbon, CO, NOx, and toluene) were
significantly higher whereas the photo-oxidation products of biogenic VOCs
(volatile organic compounds) and the biogenically influenced SOA also
increased moderately during the NPE days compared to the non-event days.
These results indicate that the frequently occurring NPEs over the Sacramento
and Sierra Nevada regions were mainly driven by urban plumes from Sacramento
and the San Francisco Bay Area, and that the interaction of regional biogenic
emissions with the urban plumes has enhanced the new particle growth. This
finding has important implications for quantifying the climate impacts of
NPEs on global scale. |
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