Photolysis of pyruvic acid in ice: Possible relevance to CO and CO_2 ice core record anomalies
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 photochemica...
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ftcaltechauth:oai:authors.library.caltech.edu:8dvxq-qs427 2024-10-13T14:08:02+00:00 Photolysis of pyruvic acid in ice: Possible relevance to CO and CO_2 ice core record anomalies Guzmán, M. I. Hoffmann, M. R. Colussi, A. J. 2007-05-26 https://doi.org/10.1029/2006JD007886 unknown American Geophysical Union https://doi.org/10.1029/2006JD007886 eprintid:58466 info:eu-repo/semantics/openAccess Other Journal of Geophysical Research D, 112(D10), Art. No. D10123, (2007-05-26) info:eu-repo/semantics/article 2007 ftcaltechauth https://doi.org/10.1029/2006JD007886 2024-09-25T18:46:41Z 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. © 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. Published - jgrd13447.pdf Article in Journal/Newspaper ice core Caltech Authors (California Institute of Technology) Journal of Geophysical Research: Atmospheres 112 D10 |
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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. © 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. Published - jgrd13447.pdf |
format |
Article in Journal/Newspaper |
author |
Guzmán, M. I. Hoffmann, M. R. Colussi, A. J. |
spellingShingle |
Guzmán, M. I. Hoffmann, M. R. Colussi, A. J. Photolysis of pyruvic acid in ice: Possible relevance to CO and CO_2 ice core record anomalies |
author_facet |
Guzmán, M. I. Hoffmann, M. R. Colussi, A. J. |
author_sort |
Guzmán, M. I. |
title |
Photolysis of pyruvic acid in ice: Possible relevance to CO and CO_2 ice core record anomalies |
title_short |
Photolysis of pyruvic acid in ice: Possible relevance to CO and CO_2 ice core record anomalies |
title_full |
Photolysis of pyruvic acid in ice: Possible relevance to CO and CO_2 ice core record anomalies |
title_fullStr |
Photolysis of pyruvic acid in ice: Possible relevance to CO and CO_2 ice core record anomalies |
title_full_unstemmed |
Photolysis of pyruvic acid in ice: Possible relevance to CO and CO_2 ice core record anomalies |
title_sort |
photolysis of pyruvic acid in ice: possible relevance to co and co_2 ice core record anomalies |
publisher |
American Geophysical Union |
publishDate |
2007 |
url |
https://doi.org/10.1029/2006JD007886 |
genre |
ice core |
genre_facet |
ice core |
op_source |
Journal of Geophysical Research D, 112(D10), Art. No. D10123, (2007-05-26) |
op_relation |
https://doi.org/10.1029/2006JD007886 eprintid:58466 |
op_rights |
info:eu-repo/semantics/openAccess Other |
op_doi |
https://doi.org/10.1029/2006JD007886 |
container_title |
Journal of Geophysical Research: Atmospheres |
container_volume |
112 |
container_issue |
D10 |
_version_ |
1812814622710824960 |