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| Titel |
Spatial and seasonal variations of fine particle water-soluble organic carbon (WSOC) over the southeastern United States: implications for secondary organic aerosol formation |
| VerfasserIn |
X. Zhang, Z. Liu, A. Hecobian, M. Zheng, N. H. Frank, E. S. Edgerton, R. J. Weber |
| 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. 14 ; Nr. 12, no. 14 (2012-07-25), S.6593-6607 |
| Datensatznummer |
250011346
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| Publikation (Nr.) |
 copernicus.org/acp-12-6593-2012.pdf |
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| Zusammenfassung |
| Secondary organic aerosol (SOA) in the southeastern US is investigated by
analyzing the spatial-temporal distribution of water-soluble organic carbon
(WSOC) and other PM2.5 components from 900 archived 24-h Teflon filters
collected at 15 urban or rural EPA Federal Reference Method (FRM) network
sites throughout 2007. Online measurements of WSOC at an urban/rural-paired
site in Georgia in the summer of 2008 are contrasted to the filter data.
Based on FRM filters, excluding biomass-burning events (levoglucosan
< 50 ng m−3), WSOC and sulfate were highly correlated with
PM2.5 mass (r2~0.7). Both components comprised a large mass
fraction of PM2.5 (13% and 31%, respectively, or
~25% and 50% for WSOM and ammonium sulfate). Sulfate and
WSOC both tracked ambient temperature throughout the year, suggesting the
temperature effects were mainly linked to faster photochemistry and/or
synoptic meteorology and less due to enhanced biogenic hydrocarbon emissions.
FRM WSOC, and to a lesser extent sulfate, were spatially homogeneous
throughout the region, yet WSOC was moderately enhanced (27%) in
locations of greater predicted isoprene emissions in summer. A Positive
Matrix Factorization (PMF) analysis identified two major source types for the
summer WSOC; 22% of the WSOC were associated with ammonium sulfate, and
56% of the WSOC were associated with brown carbon and oxalate. A
small urban excess of FRM WSOC (10%) was observed in the summer of 2007,
however, comparisons of online WSOC measurements at one urban/rural pair
(Atlanta/Yorkville) in August 2008 showed substantially greater difference in
WSOC (31%) relative to the FRM data, suggesting a low bias for urban
filters. The measured Atlanta urban excess, combined with the estimated
boundary layer heights, gave an estimated Atlanta daily WSOC production rate
in August of 0.55 mgC m−2 h−1 between mid-morning and
mid-afternoon. This study characterizes the regional nature of fine particles
in the southeastern US, confirming the importance of SOA and the roles of
both biogenic and anthropogenic emissions. |
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