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| Titel |
A case study of aerosol processing and evolution in summer in New York City |
| VerfasserIn |
Y. L. Sun, Q. Zhang, J. J. Schwab, W. N. Chen, M. S. Bae, Y. C. Lin, H. M. Hung, K. L. Demerjian |
| 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 ; 11, no. 24 ; Nr. 11, no. 24 (2011-12-16), S.12737-12750 |
| Datensatznummer |
250010275
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| Publikation (Nr.) |
 copernicus.org/acp-11-12737-2011.pdf |
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| Zusammenfassung |
| We have investigated an aerosol processing and evolution event from 21–22
July during the summer 2009 Field Intensive Study at Queens College in New
York City (NYC). The evolution processes are characterized by three
consecutive stages: (1) aerosol wet scavenging, (2) nighttime nitrate
formation, and (3) photochemical production and evolution of secondary
aerosol species. Our results suggest that wet scavenging of aerosol species
tends to be strongly related to their hygroscopicities and also mixing
states. The scavenging leads to a significant change in bulk aerosol
composition and average carbon oxidation state because of scavenging
efficiencies in the following order: sulfate > low-volatility oxygenated
organic aerosol (LV-OOA) > semi-volatile OOA (SV-OOA) > hydrocarbon-like
OA (HOA). The second stage involves a quick formation of nitrate from
heterogeneous reactions at nighttime. During the third stage, simultaneous
increases of sulfate and SV-OOA were observed shortly after sunrise,
indicating secondary aerosol formation. Organic aerosols become
highly oxidized in ~ half day as the result of photochemical
processing, consistent with previously reported results from the CO-tracer
method (OA/ΔCO). The photochemical reactions appear to progress
gradually associated with a transformation of SV- OOA to low-volatility
species based on the evolution trends of oxygen-to-carbon (O/C) ratio,
relationship between f44 (fraction of m/z 44 in OA) and f43 (fraction of m/z 43 in
OA), and size evolution of OOA and HOA. Aerosols appear to become more
internally mixed during the processing. Our results suggest that
functionalization by incorporation of both C and O plays a major role in the
early period of OA oxidation (O/C < 0.5). Our results also show that
photochemical production of LV-OOA during this event is approximately 2–3
h behind of sulfate production, which might explain, sometimes, the lack
of correlations between LV-OOA and sulfate, two secondary aerosol species
which often exist in internal mixtures over regional scales. |
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