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| Titel |
Mass absorption efficiency of elemental carbon and water-soluble organic carbon in Beijing, China |
| VerfasserIn |
Y. Cheng, K.-B. He, M. Zheng, F.-K. Duan, Z.-Y. Du, Y.-L. Ma, J.-H. Tan, F.-M. Yang, J.-M. Liu, X.-L. Zhang, R. J. Weber, M. H. Bergin, A. G. Russell |
| 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. 22 ; Nr. 11, no. 22 (2011-11-18), S.11497-11510 |
| Datensatznummer |
250010201
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| Publikation (Nr.) |
 copernicus.org/acp-11-11497-2011.pdf |
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| Zusammenfassung |
| The mass absorption efficiency (MAE) of elemental carbon (EC) in Beijing was
quantified using a thermal-optical carbon analyzer. The MAE measured at 632 nm
was 8.45±1.71 and 9.41±1.92 m2 g−1 during winter and summer
respectively. The daily variation of MAE was found to coincide with the
abundance of organic carbon (OC), especially the OC to EC ratio, perhaps due
to the enhancement by coating with organic aerosol (especially secondary
organic aerosol, SOA) or the artifacts resulting from the redistribution of
liquid-like organic particles during the filter-based absorption
measurements. Using a converting approach that accounts for the discrepancy
caused by measurements methods of both light absorption and EC
concentration, previously published MAE values were converted to the
equivalent-MAE, which is the estimated value if using the same measurement
methods as used in this study. The equivalent-MAE was found to be much lower
in the regions heavily impacted by biomass burning (e.g., below 2.7 m2 g−1
for two Indian cities). Results from source samples (including
diesel exhaust samples and biomass smoke samples) also demonstrated that
emissions from biomass burning would decrease the MAE of EC. Moreover,
optical properties of water-soluble organic carbon (WSOC) in Beijing were
presented. Light absorption by WSOC exhibited strong wavelength (λ)
dependence such that absorption varied approximately as λ−7,
which was characteristic of the brown carbon spectra. The MAE of WSOC
(measured at 365 nm) was 1.79±0.24 and 0.71±0.20 m2 g−1 during
winter and summer respectively. The large discrepancy between the MAE of
WSOC during winter and summer was attributed to the difference in the
precursors of SOA such that anthropogenic volatile organic compounds (AVOCs)
should be more important as the precursors of SOA in winter. The MAE of WSOC
in Beijing was much higher than results from the southeastern United States
which were obtained using the same method as used in this study, perhaps due
to the stronger emissions of biomass burning in China. |
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