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| Titel |
Improved measurement of carbonaceous aerosol: evaluation of the sampling artifacts and inter-comparison of the thermal-optical analysis methods |
| VerfasserIn |
Y. Cheng, K. B. He, F. K. Duan, M. Zheng, Y. L. Ma, J. H. Tan, Z. Y. Du |
| 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 (2010-09-10), S.8533-8548 |
| Datensatznummer |
250008766
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| Publikation (Nr.) |
 copernicus.org/acp-10-8533-2010.pdf |
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| Zusammenfassung |
| The sampling artifacts (both positive and negative) and the influence of
thermal-optical methods (both charring correction method and the peak inert
mode temperature) on the split of organic carbon (OC) and elemental carbon
(EC) were evaluated in Beijing. The positive sampling artifact constituted
10% and 23% of OC concentration determined by the bare quartz filter
during winter and summer, respectively. For summer samples, the adsorbed
gaseous organics were found to continuously evolve off the filter during the
whole inert mode when analyzed by the IMPROVE-A temperature protocol. This
may be due to the oxidation of the adsorbed organics during sampling
(reaction artifact) which would increase their thermal stability. The backup
quartz approach was evaluated by a denuder-based method for assessing the
positive artifact. The quartz-quartz (QBQ) in series method was demonstrated
to be reliable, since all of the OC collected by QBQ was from originally
gaseous organics. Negative artifact that could be adsorbed by quartz filter
was negligible. When the activated carbon impregnated glass fiber (CIG)
filter was used as the denuded backup filter, the denuder efficiency for
removing gaseous organics that could be adsorbed by the CIG filter was only
about 30%. EC values were found to differ by a factor of about two
depending on the charring correction method. Influence of the peak inert
mode temperature was evaluated based on the summer samples. The EC value was
found to continuously decrease with the peak inert mode temperature.
Premature evolution of light absorbing carbon began when the peak inert mode
temperature was increased from 580 to 650 °C; when further increased
to 800 °C, the OC and EC split frequently occurred in the He mode,
and the last OC peak was characterized by the overlapping of two separate
peaks. The discrepancy between EC values defined by different temperature
protocols was larger for Beijing carbonaceous aerosol compared with North
America and Europe, perhaps due to the higher concentration of brown carbon
in Beijing aerosol. |
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