title: Reactive uptake and photo-Fenton oxidation of glycolaldehyde in aerosol liquid water.
abstract: The reactive uptake and aqueous oxidation of glycolaldehyde were examined in a photochemical flow reactor using hydrated ammonium sulfate (AS) seed aerosols at RH = 80%. The glycolaldehyde that partitioned into the aerosol liquid water was oxidized via two mechanisms that may produce aqueous OH: hydrogen peroxide photolysis (H2O2 + hν) and the photo-Fenton reaction (Fe (II) + H2O2 + hν). The uptake of 80 (±10) ppb glycolaldehyde produced 2-4 wt % organic aerosol mass in the dark (kH* = (2.09-4.17) × 10(6) M atm(-1)), and the presence of an OH source increased the aqueous uptake by a factor of 4. Although the uptake was similar in both OH-aging mechanisms, photo-Fenton significantly increased the degree of oxidation (O/C = 0.9) of the aerosols compared to H2O2 photolysis (O/C = 0.5). Aerosol organics oxidized by photo-Fenton and H2O2 photolysis resemble ambient "aged" and "fresh" OA, respectively, after the equivalent of 2 h atmospheric aging. No uptake or changes in particle composition occurred on dry seed aerosol. This work illustrates that photo-Fenton chemistry efficiently forms highly oxidized organic mass in aerosol liquid water, providing a possible mechanism to bridge the gap between bulk-phase experiments and ambient particles.
authors.affiliation: Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA. tbn@caltech.edu
authors.forename: T B
authors.initials: TB
authors.lastname: Nguyen
authors.forename: M M
authors.initials: MM
authors.lastname: Coggon
authors.forename: R C
authors.initials: RC
authors.lastname: Flagan
authors.forename: J H
authors.initials: JH
authors.lastname: Seinfeld
mesh_terms: D000336:Aerosols; D000447:Aldehydes / Q000737:chemistry*; D010084:Oxidation-Reduction; D010782:Photolysis; D014867:Water / Q000737:chemistry*
chemical_list: D000336:Aerosols; D000447:Aldehydes; D014867:Water