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| Titel |
Measurement of carbonaceous aerosol with different sampling configurations and frequencies |
| VerfasserIn |
Y. Cheng, K.-B. He |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1867-1381
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Measurement Techniques ; 8, no. 7 ; Nr. 8, no. 7 (2015-07-01), S.2639-2648 |
| Datensatznummer |
250116470
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| Publikation (Nr.) |
 copernicus.org/amt-8-2639-2015.pdf |
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| Zusammenfassung |
| A common approach for measuring the mass of organic carbon (OC) and
elemental carbon (EC) in airborne particulate matter involves collection on
a quartz fiber filter and subsequent thermal–optical analysis. Although
having been widely used in aerosol studies and in PM2.5 (fine
particulate matter) chemical speciation monitoring networks in particular,
this measurement approach is prone to several types of artifacts, such as
the positive sampling artifact caused by the adsorption of gaseous organic
compounds onto the quartz filter, the negative sampling artifact due to the
evaporation of OC from the collected particles and the analytical artifact
in the thermal–optical determination of OC and EC (which is strongly
associated with the transformation of OC into char OC and typically results
in an underestimation of EC). The presence of these artifacts introduces
substantial uncertainties to observational data on OC and EC and
consequently limits our ability to evaluate OC and EC estimations in air
quality models. In this study, the influence of sampling frequency on the
measurement of OC and EC was investigated based on PM2.5 samples
collected in Beijing, China. Our results suggest that the negative sampling
artifact of a bare quartz filter could be remarkably enhanced due to the
uptake of water vapor by the filter medium. We also demonstrate that
increasing sampling duration does not necessarily reduce the impact of
positive sampling artifact, although it will enhance the
analytical artifact. Due to the effect of the analytical artifact, EC
concentrations of 48 h averaged samples were about 15 % lower than results
from 24 h averaged ones. In addition, it was found that with the increase of
sampling duration, EC results exhibited a stronger dependence on the
charring correction method and, meanwhile, optical attenuation (ATN) of EC
(retrieved from the carbon analyzer) was more significantly biased by the
shadowing effect. Results from this study will be useful for the design of
China's PM2.5 chemical speciation monitoring network, which can be
expected to be inaugurated in the near future. |
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