 |
| Titel |
Origins and composition of fine atmospheric carbonaceous aerosol in the Sierra Nevada Mountains, California |
| VerfasserIn |
D. R. Worton, A. H. Goldstein, D. K. Farmer, K. S. Docherty, J. L. Jimenez, J. B. Gilman, W. C. Kuster, J. Gouw, B. J. Williams, N. M. Kreisberg, S. V. Hering, G. Bench, M. McKay, K. Kristensen, M. Glasius, J. D. Surratt, J. H. Seinfeld |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 11, no. 19 ; Nr. 11, no. 19 (2011-10-12), S.10219-10241 |
| Datensatznummer |
250010122
|
| Publikation (Nr.) |
 copernicus.org/acp-11-10219-2011.pdf |
|
|
|
|
|
| Zusammenfassung |
| In this paper we report chemically resolved measurements of organic aerosol
(OA) and related tracers during the Biosphere Effects on Aerosols and
Photochemistry Experiment (BEARPEX) at the Blodgett Forest Research Station,
California from 15 August–10 October 2007. OA contributed
the majority of the mass to the fine atmospheric particles and was
predominately oxygenated (OOA). The highest concentrations of OA were during
sporadic wildfire influence when aged plumes were impacting the site. In
situ measurements of particle phase molecular markers were dominated by
secondary compounds and along with gas phase compounds could be categorized
into six factors or sources: (1) aged biomass burning emissions and oxidized
urban emissions, (2) oxidized urban emissions (3) oxidation products of
monoterpene emissions, (4) monoterpene emissions, (5) anthropogenic
emissions and (6) local methyl chavicol emissions and oxidation products.
There were multiple biogenic components that contributed to OA at this site
whose contributions varied diurnally, seasonally and in response to changing
meteorological conditions, e.g. temperature and precipitation events.
Concentrations of isoprene oxidation products were larger when temperatures
were higher during the first half of the campaign (15 August–12 September) due to more substantial emissions of isoprene and enhanced
photochemistry. The oxidation of methyl chavicol, an oxygenated terpene
emitted by ponderosa pine trees, contributed similarly to OA throughout the
campaign. In contrast, the abundances of monoterpene oxidation products in
the particle phase were greater during the cooler conditions in the latter
half of the campaign (13 September–10 October), even though
emissions of the precursors were lower, although the mechanism is not known.
OA was correlated with the anthropogenic tracers 2-propyl nitrate and carbon
monoxide (CO), consistent with previous observations, while being comprised
of mostly non-fossil carbon (>75%). The correlation between OA and an
anthropogenic tracer does not necessarily identify the source of the carbon
as being anthropogenic but instead suggests a coupling between the
anthropogenic and biogenic components in the air mass that might be related
to the source of the oxidant and/or the aerosol sulfate. Observations of
organosulfates of isoprene and α-pinene provided evidence for the
likely importance of aerosol sulfate in spite of neutralized aerosol
although acidic plumes might have played a role upwind of the site. This is
in contrast to laboratory studies where strongly acidic seed aerosols were
needed in order to form these compounds. These compounds together
represented only a minor fraction (<1%) of the total OA mass, which
may be the result of the neutralized aerosol at the site or because only a
small number of organosulfates were quantified. The low contribution of
organosulfates to total OA suggests that other mechanisms, e.g. NOx
enhancement of oxidant levels, are likely responsible for the majority of
the anthropogenic enhancement of biogenic secondary organic aerosol observed
at this site. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|