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| Titel |
Aerosol composition, oxidation properties, and sources in Beijing: results from the 2014 Asia-Pacific Economic Cooperation summit study |
| VerfasserIn |
W. Q. Xu, Y. L. Sun, C. Chen, W. Du, T. T. Han, Q. Q. Wang, P. Q. Fu, Z. F. Wang, X. J. Zhao, L. B. Zhou, D. S. Ji, P. C. Wang, D. R. Worsnop |
| 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 ; 15, no. 23 ; Nr. 15, no. 23 (2015-12-10), S.13681-13698 |
| Datensatznummer |
250120219
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| Publikation (Nr.) |
 copernicus.org/acp-15-13681-2015.pdf |
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| Zusammenfassung |
| The mitigation of air pollution in megacities remains a great
challenge because of the complex sources and formation mechanisms of aerosol
particles. The 2014 Asia-Pacific Economic Cooperation (APEC) summit in
Beijing serves as a unique experiment to study the impacts of emission
controls on aerosol composition, size distributions, and oxidation
properties. Herein, a high-resolution time-of-flight aerosol mass
spectrometer was deployed in urban Beijing for real-time measurements of
size-resolved non-refractory submicron aerosol (NR-PM1) species from 14 October
to 12 November 2014, along with a range of collocated measurements. The
average (±σ) PM1 was 41.6 (±38.9) μg m−3
during APEC, which was decreased by 53 % compared with that before APEC.
The aerosol composition showed substantial changes owing to emission
controls during APEC. Secondary inorganic aerosol (SIA: sulfate + nitrate + ammonium)
showed significant reductions of 62–69 %,
whereas organics presented much smaller decreases (35 %). The results from
the positive matrix factorization of organic aerosol (OA) indicated that
highly oxidized secondary organic aerosol (SOA) showed decreases similar to those of SIA
during APEC. However, primary organic aerosol (POA) from cooking, traffic, and
biomass-burning sources were comparable to those before APEC, indicating the
presence of strong local source emissions. The oxidation properties showed
corresponding changes in response to OA composition. The average
oxygen-to-carbon level during APEC was 0.36 (±0.10), which is lower
than the 0.43 (±0.13) measured before APEC, demonstrating a decrease
in the OA oxidation degree. The changes in size distributions of primary and
secondary species varied during APEC. SIA and SOA showed significant
reductions in large accumulation modes with peak diameters shifting from
~ 650 to 400 nm during APEC, whereas those of POA remained
relatively unchanged. The changes in aerosol composition, size
distributions, and oxidation degrees during the aging processes were further
illustrated in a case study of a severe haze episode. Our results elucidated
a complex response of aerosol chemistry to emission controls, which has
significant implications that emission controls over regional scales can
substantially reduce secondary particulates. However, stricter emission
controls for local source emissions are needed for further mitigating air
pollution in the megacity of Beijing. |
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