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| Titel |
Carbonaceous aerosols in China: top-down constraints on primary sources and estimation of secondary contribution |
| VerfasserIn |
T.-M. Fu, J. J. Cao, X. Y. Zhang, S. C. Lee, Q. Zhang, Y. M. Han, W. J. Qu, Z. Han, R. Zhang, Y. X. Wang, D. Chen, D. K. Henze |
| 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 ; 12, no. 5 ; Nr. 12, no. 5 (2012-03-14), S.2725-2746 |
| Datensatznummer |
250010873
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| Publikation (Nr.) |
 copernicus.org/acp-12-2725-2012.pdf |
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| Zusammenfassung |
| We simulated elemental carbon (EC) and organic carbon (OC) aerosols in China
and compared model results to surface measurements at Chinese rural and
background sites, with the goal of deriving "top-down" emission estimates
of EC and OC, as well as better quantifying the secondary sources of OC. We
included in the model state-of-the-science Chinese "bottom-up" emission
inventories for EC (1.92 TgC yr−1) and OC (3.95 TgC yr−1), as well
as updated secondary OC formation pathways. The average simulated annual
mean EC concentration at rural and background sites was 1.1 μgC m−3, 56%
lower than the observed 2.5 μgC m−3. The average
simulated annual mean OC concentration at rural and background sites was 3.4 μgC m−3, 76% lower than the observed 14 μgC m−3.
Multiple regression to fit surface monthly mean EC observations at rural and
background sites yielded the best estimate of Chinese EC source of 3.05 ± 0.78 TgC yr−1. Based on the top-down EC emission estimate and observed
seasonal primary OC/EC ratios, we estimated Chinese OC emissions to be
6.67 ± 1.30 TgC yr−1. Using these top-down estimates, the simulated
average annual mean EC concentration at rural and background sites was
significantly improved to 1.9 μgC m−3. However, the model still
significantly underestimated observed OC in all seasons (simulated average
annual mean OC at rural and background sites was 5.4 μgC m−3), with
little skill in capturing the spatiotemporal variability. Secondary
formation accounts for 21% of Chinese annual mean surface OC in the
model, with isoprene being the most important precursor. In summer, as high
as 62% of the observed surface OC may be due to secondary formation in
eastern China. Our analysis points to four shortcomings in the current
bottom-up inventories of Chinese carbonaceous aerosols: (1) the
anthropogenic source is underestimated on a national scale, particularly for
OC; (2) the spatiotemporal distributions of emissions are misrepresented;
(3) there is a missing source in western China, likely associated with the
use of biofuels or other low-quality fuels for heating; and (4) sources in
fall are not well represented, either because the seasonal shifting of
emissions and/or secondary formation are poorly captured or because specific
fall emission events are missing. In addition, secondary production of OC in
China is severely underestimated. More regional measurements with better
spatiotemporal coverage are needed to resolve these shortcomings. |
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