title: Multiphase Photochemistry of Pyruvic Acid under Atmospheric Conditions.
abstract: Aerosol and molecular processing in the atmosphere occurs in a complex and variable environment consisting of multiple phases and interfacial regions. To explore the effects of such conditions on the reactivity of chemical systems, we employ an environmental simulation chamber to investigate the multiphase photolysis of pyruvic acid, which photoreacts in the troposphere in aqueous particles and in the gas phase. Upon irradiation of nebulized pyruvic acid, acetic acid and carbon dioxide are rapidly generated, which is consistent with previous literature on the bulk phase photolysis reactions. Additionally, we identify a new C6product, zymonic acid, a species that has not previously been reported from pyruvic acid photolysis under any conditions. Its observation here, and corresponding spectroscopic signatures, indicates it could be formed by heterogeneous reactions at the droplet surface. Prior studies of the aqueous photolysis of pyruvic acid have shown that high-molecular-weight compounds are formed via radical reactions; however, they are inhibited by the presence of oxygen, leading to doubt as to whether the chemistry would occur in the atmosphere. Identification of dimethyltartaric acid from the photolysis of multiphase pyruvic acid in air confirms radical polymerization chemistry can compete with oxygen reactions to some extent under aerobic conditions. Evidence of additional polymerization within the particles during irradiation is suggested by the increasing viscosity and organic content of the particles. The implications of multiphase specific processes are then discussed within the broader scope of atmospheric science.
authors.affiliation: Department of Chemistry and Biochemistry, CIRES, University of Colorado , Boulder, Colorado 80309, United States.
authors.forename: Allison E
authors.identifier: http://orcid.org/0000-0002-1731-1687
authors.initials: AE
authors.lastname: Reed Harris
authors.affiliation: Department of Applied Physics, University of Eastern Finland , Kuopio Campus, P.O. Box 1627, 70211 Kuopio, Finland.
authors.forename: Aki
authors.initials: A
authors.lastname: Pajunoja
authors.affiliation: LISA, UMR CNRS 7583, Université Paris Est Cretéil (UPEC), Université Paris Diderot (UPD), Institut Pierre Simon Laplace (IPSL), 94010 Cretéil, France.
authors.forename: Mathieu
authors.initials: M
authors.lastname: Cazaunau
authors.affiliation: LISA, UMR CNRS 7583, Université Paris Est Cretéil (UPEC), Université Paris Diderot (UPD), Institut Pierre Simon Laplace (IPSL), 94010 Cretéil, France.
authors.forename: Aline
authors.initials: A
authors.lastname: Gratien
authors.affiliation: LISA, UMR CNRS 7583, Université Paris Est Cretéil (UPEC), Université Paris Diderot (UPD), Institut Pierre Simon Laplace (IPSL), 94010 Cretéil, France.
authors.forename: Edouard
authors.initials: E
authors.lastname: Pangui
authors.affiliation: Aix Marseille Université, CNRS, LCE, 13331, Marseille, France.
authors.forename: Anne
authors.initials: A
authors.lastname: Monod
authors.affiliation: Department of Chemistry and Biochemistry, CIRES, University of Colorado , Boulder, Colorado 80309, United States.
authors.forename: Elizabeth C
authors.initials: EC
authors.lastname: Griffith
authors.affiliation: Department of Applied Physics, University of Eastern Finland , Kuopio Campus, P.O. Box 1627, 70211 Kuopio, Finland.
authors.forename: Annele
authors.initials: A
authors.lastname: Virtanen
authors.affiliation: LISA, UMR CNRS 7583, Université Paris Est Cretéil (UPEC), Université Paris Diderot (UPD), Institut Pierre Simon Laplace (IPSL), 94010 Cretéil, France.
authors.forename: Jean-Francois
authors.initials: JF
authors.lastname: Doussin
authors.affiliation: Department of Chemistry and Biochemistry, CIRES, University of Colorado , Boulder, Colorado 80309, United States.
authors.forename: Veronica
authors.identifier: http://orcid.org/0000-0001-5863-8056
authors.initials: V
authors.lastname: Vaida