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Atmospheric Simulation Chamber Studies of the Gas-Phase Photolysis of Pyruvic Acid.

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Title: Atmospheric Simulation Chamber Studies of the Gas-Phase Photolysis of Pyruvic Acid.
Authors: Harris, Allison E. Reed1, Cazaunau, Mathieu2, Gratien, Aline2, Pangui, Edouard2, Doussin, Jean-François2 Jean-Francois.Doussin@lisa.u-pec.fr, Vaida, Veronica1 Vaida@colorado.edu
Source: Journal of Physical Chemistry A. 11/9/2017, Vol. 121 Issue 44, p8348-8358. 11p.
Subjects: Pyruvic acid, Gas phase reactions, Troposphere, Photolysis (Chemistry), Acetaldehyde
Abstract: Pyruvic acid is an atmospherically abundant α-keto-acid that degrades efficiently from the troposphere via gas-phase photolysis. To explore conditions relevant to the environment, 2-12 ppm pyruvic acid is irradiated by a solar simulator in the environmental simulation chamber, CESAM. The combination of the long path length available in the chamber and its low surface area to volume ratio allows us to quantitatively examine the quantum yield and photochemical products of pyruvic acid. Such details are new to the literature for the low initial concentrations of pyruvic acid employed here. We determined photolysis quantum yields of ϕobsN2 = 0.84 ± 0.1 in nitrogen and ϕobsAir = 3.2 ± 0.5 in air, which are higher than those reported by previous studies that used higher partial pressures of pyruvic acid. The quantum yield greater than unity in air is due to secondary chemistry, driven by O2, that emerges under the conditions in these experiments. The low concentration of pyruvic acid and the resulting oxygen effect also alter the product distribution such that acetic acid, rather than acetaldehyde, is the primary product in air. These results indicate that tropospheric pyruvic acid may degrade in part via photoinduced mechanisms that are different than previously expected. [ABSTRACT FROM AUTHOR]
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Abstract:Pyruvic acid is an atmospherically abundant α-keto-acid that degrades efficiently from the troposphere via gas-phase photolysis. To explore conditions relevant to the environment, 2-12 ppm pyruvic acid is irradiated by a solar simulator in the environmental simulation chamber, CESAM. The combination of the long path length available in the chamber and its low surface area to volume ratio allows us to quantitatively examine the quantum yield and photochemical products of pyruvic acid. Such details are new to the literature for the low initial concentrations of pyruvic acid employed here. We determined photolysis quantum yields of ϕobsN2 = 0.84 ± 0.1 in nitrogen and ϕobsAir = 3.2 ± 0.5 in air, which are higher than those reported by previous studies that used higher partial pressures of pyruvic acid. The quantum yield greater than unity in air is due to secondary chemistry, driven by O2, that emerges under the conditions in these experiments. The low concentration of pyruvic acid and the resulting oxygen effect also alter the product distribution such that acetic acid, rather than acetaldehyde, is the primary product in air. These results indicate that tropospheric pyruvic acid may degrade in part via photoinduced mechanisms that are different than previously expected. [ABSTRACT FROM AUTHOR]
ISSN:10895639
DOI:10.1021/acs.jpca.7b05139