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| Titel |
Organic matter and non-refractory aerosol over the remote Southeast Pacific: oceanic and combustion sources |
| VerfasserIn |
L. M. Shank, S. Howell, A. D. Clarke, S. Freitag, V. Brekhovskikh, V. Kapustin, C. McNaughton, T. Campos, R. Wood |
| 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. 1 ; Nr. 12, no. 1 (2012-01-11), S.557-576 |
| Datensatznummer |
250010451
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| Publikation (Nr.) |
 copernicus.org/acp-12-557-2012.pdf |
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| Zusammenfassung |
| Submicron aerosol physical and chemical properties in remote marine air were
measured from aircraft over the Southeast Pacific during VOCALS-REx in 2008
and the North Pacific during IMPEX in 2006, and aboard a ship in the
Equatorial Pacific in 2009. A High Resolution – Particle Time of Flight
Aerosol Mass Spectrometer (HR-ToF-AMS) measured non-refractory submicron
aerosol composition during all campaigns. Sulfate (SO4) and organics
(Org), during VOCALS and the cruise show lower absolute values than those
reported for previous "clean air" studies. In the marine boundary layer,
average concentrations for SO4 were 0.52 μg m−3 for the
VOCALS region and 0.85 μg m−3 for the equatorial region while
average Org concentrations were 0.10 and 0.07 μg m−3,
respectively. Campaign average Org/SO4 ratios were 0.19 (VOCALS) and
0.08 (equatorial Pacific). Black carbon (BC) measurements from a single
particle soot photometer (SP2) and carbon monoxide (CO) concentrations over the Southeast
Pacific provided sensitive indicators of pollution. CO and BC were used to
identify the least polluted air, which had average concentrations of
SO4 and Org of 0.14 and 0.01 μg m−3, respectively, with an
average Org/SO4 of 0.08. Data from IMPEX was constrained to similar
clean air criterion, and resulted in an average Org/SO4 ratio of 0.19. Under
the cleanest MBL conditions during VOCALS, identified by CO below 61 ppbv, a
robust linear relationship between Org and BC concentrations revealed that
even at very low pollution levels, combustion sources dominated organic
aerosol, suggesting little to no marine source of submicrometer Org to the
atmosphere over the eastern South Pacific. This means marine organics cannot
be identified by merely setting a standard for background conditions below
which anthropogenic influence can be disregarded. Other methods must be used
to exclude non-marine sources. |
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