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| Titel |
Estimation of continuous anthropogenic CO2: model-based evaluation of CO2, CO, δ13C(CO2) and Δ14C(CO2) tracer methods |
| VerfasserIn |
S. N. Vardag, C. Gerbig, G. Janssens-Maenhout, I. Levin |
| 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 ; 15, no. 22 ; Nr. 15, no. 22 (2015-11-16), S.12705-12729 |
| Datensatznummer |
250120164
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| Publikation (Nr.) |
 copernicus.org/acp-15-12705-2015.pdf |
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| Zusammenfassung |
| We investigate different methods for estimating anthropogenic CO2 using
modeled continuous atmospheric concentrations of CO2 alone, as well as
CO2 in combination with the surrogate tracers CO, δ13C(CO2) and Δ14C(CO2). These methods are
applied at three hypothetical stations representing rural, urban and
polluted conditions. We find that, independent of the tracer used, an
observation-based estimate of continuous anthropogenic CO2 is not yet
feasible at rural measurement sites due to the low signal-to-noise ratio of
anthropogenic CO2 estimates at such settings. The tracers δ13C(CO2) and CO provide an accurate possibility to determine
anthropogenic CO2 continuously, only if all CO2 sources in the
catchment area are well characterized or calibrated with respect to their
isotopic signature and CO to anthropogenic CO2 ratio. We test different
calibration strategies for the mean isotopic signature and CO to CO2
ratio using precise Δ14C(CO2) measurements on
monthly integrated as well as on grab samples. For δ13C(CO2), a calibration with annually averaged 14C(CO2)
grab samples is most promising, since integrated sampling introduces large
biases into anthropogenic CO2 estimates. For CO, these biases are
smaller. The precision of continuous anthropogenic CO2 determination
using δ13C(CO2) depends on measurement precision of
δ13C(CO2) and CO2, while the CO method is mainly
limited by the variation in natural CO sources and sinks. At present,
continuous anthropogenic CO2 could be determined using the tracers
δ13C(CO2) and/or CO with a precision of about 30 %, a
mean bias of about 10 % and without significant diurnal discrepancies.
Hypothetical future measurements of continuous Δ14C(CO2)
with a precision of 5 ‰ are promising for anthropogenic
CO2 determination (precision ca. 10–20 %) but are not yet available. The investigated tracer-based approaches open the door to improving,
validating and reducing biases of highly resolved emission inventories using
atmospheric observation and regional modeling. |
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