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| Titel |
Assessment of fossil fuel carbon dioxide and other anthropogenic trace gas emissions from airborne measurements over Sacramento, California in spring 2009 |
| VerfasserIn |
J. C. Turnbull, A. Karion, M. L. Fischer, I. Faloona, T. Guilderson, S. J. Lehman, B. R. Miller, J. B. Miller, S. Montzka, T. Sherwood, S. Saripalli, C. Sweeney, P. P. Tans |
| 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. 2 ; Nr. 11, no. 2 (2011-01-25), S.705-721 |
| Datensatznummer |
250009194
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| Publikation (Nr.) |
 copernicus.org/acp-11-705-2011.pdf |
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| Zusammenfassung |
| Direct quantification of fossil fuel CO2 (CO2ff) in atmospheric
samples can be used to examine several carbon cycle and air quality
questions. We collected in situ CO2, CO, and CH4 measurements and
flask samples in the boundary layer and free troposphere over Sacramento,
California, USA, during two aircraft flights over and downwind of this urban
area during spring of 2009. The flask samples were analyzed for Δ14CO2 and CO2 to determine the recently added CO2ff
mole fraction. A suite of greenhouse and other trace gases, including
hydrocarbons and halocarbons, were measured in the same samples. Strong
correlations were observed between CO2ff and numerous trace gases
associated with urban emissions. From these correlations we estimate
emission ratios between CO2ff and these species, and compare these with
bottom-up inventory-derived estimates. Recent county level inventory
estimates for carbon monoxide (CO) and benzene from the California Air
Resources Board CEPAM database are in good agreement with our measured
emission ratios, whereas older emissions inventories appear to overestimate
emissions of these gases by a factor of two. For most other trace species,
there are substantial differences (200–500%) between our measured
emission ratios and those derived from available emission inventories. For
the first flight, we combine in situ CO measurements with the measured
CO:CO2ff emission ratio of 14 ± 2 ppbCO/ppmCO2 to derive an
estimate of CO2ff mole fraction throughout this flight, and also
estimate the biospheric CO2 mixing ratio (CO2bio) from the
difference of total and fossil CO2. The resulting CO2bio varies
dramatically from up to 8 ± 2 ppm in the urban plume to −6 ± 1 ppm in
the surrounding boundary layer air. Finally, we use the in situ estimates of
CO2ff mole fraction to infer total fossil fuel CO2 emissions from
the Sacramento region, using a mass balance approach. The resulting
emissions are uncertain to within a factor of two due to uncertainties in
wind speed and boundary layer height. Nevertheless, this first attempt to
estimate urban-scale CO2ff from atmospheric radiocarbon measurements
shows that CO2ff can be used to verify and improve emission inventories
for many poorly known anthropogenic species, separate biospheric CO2,
and indicates the potential to constrain CO2ff emissions if transport
uncertainties are reduced. |
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