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| Titel |
Maintaining consistent traceability in high-precision isotope measurements of CO2: a way to verify atmospheric trends of δ13C and δ18O |
| VerfasserIn |
L. Huang, A. Chivulescu, D. Ernst, W. Zhang, A.-L. Norman, Y.-S. Lee |
| 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 ; 6, no. 7 ; Nr. 6, no. 7 (2013-07-17), S.1685-1705 |
| Datensatznummer |
250017921
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| Publikation (Nr.) |
 copernicus.org/amt-6-1685-2013.pdf |
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| Zusammenfassung |
| Maintaining consistent traceability of high-precision measurements of
CO2 isotopes is critical in order to obtain accurate atmospheric trends of
δ13C and δ18O (in CO2). Although a number of
laboratories/organizations around the world have been conducting baseline
measurements of atmospheric CO2 isotopes for several decades, reports
on the traceability and maintenance are rare. In this paper, a principle and
an approach for maintaining consistent traceability in high-precision
isotope measurements (δ13C and δ18O) of
atmospheric CO2 are described. The concept of Big Delta is introduced and
its role in maintaining traceability of the isotope measurements is
described and discussed extensively. The uncertainties of the traceability
have been estimated based on annual calibration records over the last 10 yr.
The overall uncertainties of CO2 isotope measurements for
individual ambient samples analyzed by the program at Environment Canada
have been estimated (excluding these associated with the sampling). The
values are 0.02 and 0.05‰ in δ13C and δ18O, respectively, which are
close to the World Meteorological Organization (WMO) targets for data compatibility. The annual rates of change in δ13C and
δ18O of the primary anchor (which links the flask measurements
back to the VPDB-CO2 scale) are close to zero (−0.0016 ± 0.0012‰,
and −0.006 ± 0.003‰ per
year, respectively) over a period of 10 yr (2001–2011). The average
annual changes of δ13C and δ18O in air CO2 at
Alert GAW station over the period from 1999 to 2010 have been evaluated and
confirmed; they are −0.025 ± 0.003‰ and
0.000 ± 0.010‰, respectively. The results are
consistent with a continuous contribution of fossil fuel CO2 to the
atmosphere, having a trend toward more negative in δ13C,
whereas the lack of change in δ18O likely reflects the
influence from the global hydrologic cycle. The total change of δ13C
and δ18O during this period is ~0.27‰ and
~0.00‰, respectively. Finally, the challenges and
recommendations as strategies to maintain a consistent traceability are
described. |
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