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| Titel |
Characteristics and sources of submicron aerosols above the urban canopy (260 m) in Beijing, China, during the 2014 APEC summit |
| VerfasserIn |
C. Chen, Y. L. Sun, W. Q. Xu, W. Du, L. B. Zhou, T. T. Han, Q. Q. Wang, P. Q. Fu, Z. F. Wang, Z. Q. Gao, Q. Zhang, 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. 22 ; Nr. 15, no. 22 (2015-11-19), S.12879-12895 |
| Datensatznummer |
250120173
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| Publikation (Nr.) |
 copernicus.org/acp-15-12879-2015.pdf |
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| Zusammenfassung |
| The megacity of Beijing has experienced frequent severe fine particle
pollution during the last decade. Although the sources and formation
mechanisms of aerosol particles have been extensively investigated on the
basis of ground measurements, real-time characterization of aerosol particle
composition and sources above the urban canopy in Beijing is rare. In this
study, we conducted real-time measurements of non-refractory submicron
aerosol (NR-PM1) composition at 260 m at the Beijing 325 m meteorological
tower (BMT) from 10 October to 12 November 2014, by using an
aerosol chemical speciation monitor (ACSM) along with synchronous
measurements of size-resolved NR-PM1 composition near ground level
using a high-resolution time-of-flight aerosol mass spectrometer
(HR–ToF–AMS). The NR-PM1 composition above the urban canopy was
dominated by organics (46 %), followed by nitrate (27 %) and sulfate
(13 %). The high contribution of nitrate and high
NO3− / SO42− mass ratios illustrates an important role of
nitrate in particulate matter (PM) pollution during the study period. The
organic aerosol (OA) was mainly composed of secondary OA (SOA), accounting
for 61 % on an average. Different from that measured at the ground site,
primary OA (POA) correlated moderately with SOA, likely suggesting a high
contribution from regional transport above the urban canopy. The
Asia–Pacific Economic Cooperation (APEC) summit with strict emission
controls provides a unique opportunity to study the impacts of emission
controls on aerosol chemistry. All aerosol species were shown to have
significant decreases of 40–80 % during APEC from those measured before
APEC, suggesting that emission controls over regional scales substantially
reduced PM levels. However, the bulk aerosol composition was relatively
similar before and during APEC as a result of synergetic controls of aerosol
precursors. In addition to emission controls, the routine circulations of
mountain–valley breezes were also found to play an important role in
alleviating PM levels and achieving the "APEC blue" effect. The evolution
of vertical differences between 260 m and the ground level was also
investigated. Our results show complex vertical differences during the
formation and evolution of severe haze episodes that are closely related to
aerosol sources and boundary-layer dynamics. |
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