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Seasonal and diurnal variations of ^(13)C^(18)O^(16)O in air: Initial observations from Pasadena, CA

Affek, Hagit P. and Xu, Xiaomei and Eiler, John M. (2007) Seasonal and diurnal variations of ^(13)C^(18)O^(16)O in air: Initial observations from Pasadena, CA. Geochimica et Cosmochimica Acta, 71 (21). pp. 5033-5043. ISSN 0016-7037.

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The budget of atmospheric CO_2 is widely studied using records of temporal and spatial variations of concentrations, δ^(13)C and δ^(18)O values. However, the number and diversity of sources and sinks prevents these alone from fully constraining the budget. Molecules containing two rare isotopes can serve as additional tracers and potentially provide additional, independent, constraints. We present data documenting seasonal and diurnal variations of CO_2 having a mass of 47 u (mostly ^(13)C^(18)^O(16)O) in air from Pasadena, CA. We report these data using the ‘mass 47 anomaly’ (Δ_(47)), which is defined as the deviation of R^(47)(=[47]/[44]) from that expected for a random distribution of isotopologues. Between February 2004 and December 2005, Δ_(47) showed a seasonal pattern that differed significantly from that expected based on thermodynamic equilibrium. During the year 2004 Δ_(47) was 0.76‰ in winter, increased to 0.87‰ in summer and gradually decreased through the autumn to 0.81‰ at the end of the year. Δ_(47) then increased again through the winter and spring of 2005 to 0.97‰ in summer followed by a decrease to 0.88‰ at the end of 2005. The seasonal variations cannot be accounted for by variations in the relative contribution of local fossil fuel sources. Diurnal variations were the combined effect of both fuel combustion and respiration having Δ_(47) values of 0.41‰ and ca. 0.77‰, respectively. The seasonal cycle may be interpreted as a competition between low Δ_(47) values in respiration and higher Δ_(47) values resulting from CO_2-water exchange in photosynthesis.

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Additional Information:© 2007 Elsevier Ltd. Received 26 March 2007; accepted in revised form 15 August 2007; available online 14 September 2007. Associate editor: Miryam Bar-Matthews. We thank Eric Klinkner of the Pasadena Water and Power for local electricity production estimates, Michael Bender for the Cape Grim and Barrow air samples and constructive comments as well as Sally Newman and Lisa Welp for helpful discussion. We thank M. Bar-Mathews and two anonymous reviewers for helpful comments. This work is supported by Grants NSF-EAR-0345905, the GPS Davidow Endowment Fund and the David and Lucile Packard Fund.
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GPS Davidow Endowment FundUNSPECIFIED
David and Lucile Packard FoundationUNSPECIFIED
Issue or Number:21
Record Number:CaltechAUTHORS:20121031-112603660
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Official Citation:Hagit P. Affek, Xiaomei Xu, John M. Eiler, Seasonal and diurnal variations of 13C18O16O in air: Initial observations from Pasadena, CA, Geochimica et Cosmochimica Acta, Volume 71, Issue 21, 1 November 2007, Pages 5033-5043, ISSN 0016-7037, 10.1016/j.gca.2007.08.014. (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:35208
Deposited By: Ruth Sustaita
Deposited On:31 Oct 2012 18:42
Last Modified:15 Nov 2019 18:39

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