title: Secondary organic aerosol formation during evaporation of droplets containing atmospheric aldehydes, amines, and ammonium sulfate.
abstract: Reactions of carbonyl compounds in cloudwater produce organic aerosol mass through in-cloud oxidation and during postcloud evaporation. In this work, postcloud evaporation was simulated in laboratory experiments on evaporating droplets that contain mixtures of common atmospheric aldehydes with ammonium sulfate (AS), methylamine, or glycine. Aerosol diameters were measured during monodisperse droplet drying experiments and during polydisperse droplet equilibration experiments at 75% relative humidity, and condensed-phase mass was measured in bulk thermogravimetric experiments. The evaporation of water from a droplet was found to trigger aldehyde reactions that increased residual particle volumes by a similar extent in room-temperature experiments, regardless of whether AS, methylamine, or glycine was present. The production of organic aerosol volume was highest from droplets containing glyoxal, followed by similar production from methylglyoxal or hydroxyacetone. Significant organic aerosol production was observed for glycolaldehyde, acetaldehyde, and formaldehyde only at elevated temperatures in thermogravimetric experiments. In many experiments, the amount of aerosol produced was greater than the sum of all solutes plus nonvolatile solvent impurities, indicating the additional presence of trapped water, likely caused by increasing aerosol-phase viscosity due to oligomer formation.
authors.affiliation: Department of Chemistry and Biochemistry, University of San Diego , 5998 Alcalá Park, San Diego California 92110, United States.
authors.forename: Melissa M
authors.initials: MM
authors.lastname: Galloway
authors.forename: Michelle H
authors.initials: MH
authors.lastname: Powelson
authors.forename: Nahzaneen
authors.initials: N
authors.lastname: Sedehi
authors.forename: Stephanie E
authors.initials: SE
authors.lastname: Wood
authors.forename: Katherine D
authors.initials: KD
authors.lastname: Millage
authors.forename: Julia A
authors.initials: JA
authors.lastname: Kononenko
authors.forename: Alec D
authors.initials: AD
authors.lastname: Rynaski
authors.forename: David O
authors.initials: DO
authors.lastname: De Haan
mesh_terms: D000096:Acetone / Q000031:analogs & derivatives* / Q000737:chemistry; D000336:Aerosols; D000447:Aldehydes / Q000737:chemistry*; D000588:Amines / Q000737:chemistry*; D000645:Ammonium Sulfate / Q000737:chemistry*; D005998:Glycine / Q000737:chemistry; D006037:Glyoxal / Q000737:chemistry; D011765:Pyruvaldehyde / Q000737:chemistry; D014867:Water / Q000737:chemistry
chemical_list: D000336:Aerosols; D000447:Aldehydes; D000588:Amines; D014867:Water; D000096:Acetone; D006037:Glyoxal; D011765:Pyruvaldehyde; C004433:acetol; D000645:Ammonium Sulfate; D005998:Glycine