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Photolysis of pyruvic acid in ice: Possible relevance to CO and CO_2 ice core record anomalies

Guzmán, M. I. and Hoffmann, M. R. and Colussi, A. J. (2007) Photolysis of pyruvic acid in ice: Possible relevance to CO and CO_2 ice core record anomalies. Journal of Geophysical Research D, 112 (D10). Art. No. D10123. ISSN 0148-0227.

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The abnormal spikes detected in some CO and CO_2 polar ice core records indicate persistent chemical activity in glacial ice. Since CO and CO_2 spikes are correlated, and their amplitudes scale with reported CO/CO_2 yields for the photolysis of dissolved natural organic matter, a common photochemical source is implicated. Given that sufficient actinic radiation is constantly generated throughout ice by cosmic muons (Colussi and Hoffmann, 2003), it remains to be shown that the photolyses of typical organic contaminants proceed by similar mechanisms in water and ice. Here we report that the photodecarboxylation of pyruvic acid (PA, an ubiquitous ice contaminant) indeed leads to the same products nearly as efficiently in both media. CO_2 is promptly released from frozen PA/H_2O films upon illumination and continues to evolve after photolysis. By analogy with our studies in water (Guzmán et al., 2006b), we infer that ^3PA* reacts with PA in ice producing CH_3C(O)C(O)O· and (CH_3C•(OH)C(O)OH) radicals. The barrierless decarboxylation, CH3C(O)C(O)O· → CH_3C(O)· + CO_2, accounts for prompt CO_2 emissions down to ∼140 K. Bimolecular radical reactions subsequently ensue in fluid molecular environments, both in water and ice, leading to metastable intermediates that decarboxylate immediately in water, but protractedly in ice. The overall quantum yield of CO_2 production in the λ ~313 nm photolysis of PA in ice at 250 K is ∼60% of that in water at 293 K. The in situ photolysis of natural organic matter is, therefore, a plausible explanation of CO and CO_2 ice core record anomalies.

Item Type:Article
Related URLs:
URLURL TypeDescription
Guzmán, M. I.0000-0002-6730-7766
Hoffmann, M. R.0000-0001-6495-1946
Colussi, A. J.0000-0002-3400-4101
Additional Information:© 2007 American Geophysical Union. Received 4 August 2006; revised 19 January 2007; accepted 28 January 2007; published 26 May 2007. This work was financed by NSF grant ATM-0228140. Nathan Dalleska (Caltech Environmental Analysis Center) provided valuable technical assistance.
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Issue or Number:D10
Record Number:CaltechAUTHORS:20150623-154752526
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Official Citation:Guzmán, M. I., M. R. Hoffmann, and A. J. Colussi (2007), Photolysis of pyruvic acid in ice: Possible relevance to CO and CO2 ice core record anomalies, J. Geophys. Res., 112, D10123, doi:10.1029/2006JD007886.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:58466
Deposited By: George Porter
Deposited On:29 Jul 2015 15:09
Last Modified:09 Mar 2020 13:18

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