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| Titel |
Haze types in Beijing and the influence of agricultural biomass burning |
| VerfasserIn |
W. J. Li, L. Y. Shao, P. R. Buseck |
| 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 ; 10, no. 17 ; Nr. 10, no. 17 (2010-09-01), S.8119-8130 |
| Datensatznummer |
250008740
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| Publikation (Nr.) |
 copernicus.org/acp-10-8119-2010.pdf |
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| Zusammenfassung |
| Emissions from agricultural biomass burning (ABB) in northern China have a
significant impact on the regional and global climate. The monthly average
aerosol optical depth (AOD) at 550 nm in northern China in 2007 had a
maximum of 0.7 in June. The AOD measurements are consistent with regional
brown hazes that occurred at that time, which was a period of severe aerosol
pollution. Aerosol particles were collected in urban Beijing from 12 to 30 June
2007, during a period of high haze, and studied using transmission
electron microscopy with energy-dispersive X-ray spectrometry. The dominant
particle types collected in the fine fraction (diameter <1 μm) were
ammonium sulfate, soot, K2SO4, KNO3, and organic matter,
except that the K salts were minor between 21 and 30 June. K-rich particles
as tracers of biomass burning, together with wildfire maps, show that
intense regional ABB in northern China contributed significantly to the
regional haze between 12 and 20 June. We therefore grouped the episodes into
type-1 and -2 haze, with the former occurring between 12 and 20 June and the
latter between 21 and 30 June. After long-range transport, ABB particles in
the type-1 haze exhibited marked changes in morphology, composition, and
mixing state. KCl particles were absent, presumably having been converted by
heterogeneous reactions to K2SO4 and KNO3. Soot particles
were mixed with the other particle types. Abundant organic matter and
soluble salts emitted by ABB increased their sizes during transport and
resulted in more hygroscopic aerosol particles in downwind areas, becoming
additional cloud condensation nuclei. The high AOD (average value 2.2) in
Beijing during 12 to 20 June is partly explained by the hygroscopic
growth of fine aerosol particles and by the strong absorption of internally
mixed soot particles, both coming from regional ABB emissions. Therefore, it
is important to consider the origins of the haze, which in turn leads to the
different particle types. |
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