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| Titel |
Characterization of ultrafine particle number concentration and new particle formation in an urban environment of Taipei, Taiwan |
| VerfasserIn |
H. C. Cheung, C. C.-K. Chou, W.-R. Huang, C.-Y. Tsai |
| 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 ; 13, no. 17 ; Nr. 13, no. 17 (2013-09-06), S.8935-8946 |
| Datensatznummer |
250085679
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| Publikation (Nr.) |
 copernicus.org/acp-13-8935-2013.pdf |
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| Zusammenfassung |
| An intensive aerosol characterization experiment was performed at the Taipei
Aerosol and Radiation Observatory (TARO, 25.02° N, 121.53° E) in the
urban area of Taipei, Taiwan, during July 2012. Number concentration and size
distribution of aerosol particles were measured continuously, which were
accompanied by concurrent measurements of mass concentration of submicron
particles, PM1 (d ≤ 1 μm), and photolysis rate of ozone,
J(O1D). The averaged number concentrations of total (Ntotal),
accumulation mode (Nacu), Aitken mode (NAitken), and nucleation
mode (Nnuc) particles were 13.9 × 103 cm−3,
1.2 × 103 cm−3, 6.1 × 103 cm−3, and 6.6 × 103 cm−3,
respectively. Accordingly, the ultrafine particles (UFPs, d ≤ 100 nm)
accounted for 91% of the total number concentration of particles measured
in this study (10 ≤ d ≤ 429 nm), indicating the importance of UFPs
to the air quality and radiation budget in Taipei and its surrounding areas.
An averaged Nnuc / NOx ratio of 192.4 cm−3 ppbv−1 was
derived from nighttime measurements, which was suggested to be the
characteristic of vehicle emissions that contributed to the "urban
background" of nucleation mode particles throughout a day. On the contrary,
it was found that the number concentration of nucleation mode particles was
independent of NOx and could be elevated up to 10 times of the "urban
background" levels during daytime, suggesting a substantial amount of
nucleation mode particles produced from photochemical processes. Averages
(± 1σ) of the diameter growth rate (GR) and formation rate of
nucleation mode particles, J10, were 11.9 ± 10.6 nm h−1 and
6.9 ± 3.0 cm−3 s−1, respectively. Consistency in the time
series of the nucleation mode particle concentration and the proxy of
H2SO4 production, UVB · SO2/CS, for new particle formation
(NPF) events suggested that photooxidation of SO2 was likely one of
the major mechanisms for the formation of new particles in our study area.
Moreover, it was revealed that the particle growth rate correlated
exponentially with the photolysis of ozone, implying that the condensable
vapors were produced mostly from photooxidation reactions. In addition,
this study also revealed that Nnuc exhibited a quadratic relationship
with J10. The quadratic relationship was inferred as a result of aerosol
dynamics and featured NPF processes in urban areas. |
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