title: Airborne measurements of organosulfates over the continental U.S.
abstract: Organosulfates are important secondary organic aerosol (SOA) components and good tracers for aerosol heterogeneous reactions. However, the knowledge of their spatial distribution, formation conditions, and environmental impact is limited. In this study, we report two organosulfates, an isoprene-derived isoprene epoxydiols (IEPOX) (2,3-epoxy-2-methyl-1,4-butanediol) sulfate and a glycolic acid (GA) sulfate, measured using the NOAA Particle Analysis Laser Mass Spectrometer (PALMS) on board the NASA DC8 aircraft over the continental U.S. during the Deep Convective Clouds and Chemistry Experiment (DC3) and the Studies of Emissions and Atmospheric Composition, Clouds, and Climate Coupling by Regional Surveys (SEAC4RS). During these campaigns, IEPOX sulfate was estimated to account for 1.4% of submicron aerosol mass (or 2.2% of organic aerosol mass) on average near the ground in the southeast U.S., with lower concentrations in the western U.S. (0.2-0.4%) and at high altitudes (<0.2%). Compared to IEPOX sulfate, GA sulfate was more uniformly distributed, accounting for about 0.5% aerosol mass on average, and may be more abundant globally. A number of other organosulfates were detected; none were as abundant as these two. Ambient measurements confirmed that IEPOX sulfate is formed from isoprene oxidation and is a tracer for isoprene SOA formation. The organic precursors of GA sulfate may include glycolic acid and likely have both biogenic and anthropogenic sources. Higher aerosol acidity as measured by PALMS and relative humidity tend to promote IEPOX sulfate formation, and aerosol acidity largely drives in situ GA sulfate formation at high altitudes. This study suggests that the formation of aerosol organosulfates depends not only on the appropriate organic precursors but also on emissions of anthropogenic sulfur dioxide (SO2), which contributes to aerosol acidity.
  
  
  CONCLUSIONS
  IEPOX sulfate is an isoprene SOA tracer at acidic and low NO conditions Glycolic acid sulfate may be more abundant than IEPOX sulfate globally SO2impacts IEPOX sulfate by increasing aerosol acidity and water uptake.
authors.affiliation: Chemical Sciences Division, Earth System Research Laboratory, NOAA Boulder, Colorado, USA ; Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder Boulder, Colorado, USA.
authors.forename: Jin
authors.initials: J
authors.lastname: Liao
authors.affiliation: Chemical Sciences Division, Earth System Research Laboratory, NOAA Boulder, Colorado, USA ; Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder Boulder, Colorado, USA.
authors.forename: Karl D
authors.initials: KD
authors.lastname: Froyd
authors.affiliation: Chemical Sciences Division, Earth System Research Laboratory, NOAA Boulder, Colorado, USA.
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Murphy
authors.affiliation: Department of Chemistry, University of Wisconsin-Madison Madison, Wisconsin, USA ; Now at Department of Chemistry and Chemical Biology, Harvard University Cambridge, Massachusetts, USA.
authors.forename: Frank N
authors.initials: FN
authors.lastname: Keutsch
authors.affiliation: Department of Chemistry, University of Wisconsin-Madison Madison, Wisconsin, USA.
authors.forename: Ge
authors.initials: G
authors.lastname: Yu
authors.affiliation: Division of Geology & Planetary Sciences Pasadena, California, USA ; Division of Engineering and Applied Science Pasadena, California, USA.
authors.forename: Paul O
authors.initials: PO
authors.lastname: Wennberg
authors.affiliation: Division of Geology & Planetary Sciences Pasadena, California, USA.
authors.forename: Jason M
authors.initials: JM
authors.lastname: St Clair
authors.affiliation: Division of Geology & Planetary Sciences Pasadena, California, USA.
authors.forename: John D
authors.initials: JD
authors.lastname: Crounse
authors.affiliation: Institut für Ionenphysik und Angewandte Physik, Leopold-Franzens Universität Innsbruck Innsbruck, Austria ; Now at Department of Chemistry, University of Olso Oslo, Norway.
authors.forename: Armin
authors.initials: A
authors.lastname: Wisthaler
authors.affiliation: Institut für Ionenphysik und Angewandte Physik, Leopold-Franzens Universität Innsbruck Innsbruck, Austria ; Now at Department of Chemistry, University of Olso Oslo, Norway.
authors.forename: Tomas
authors.initials: T
authors.lastname: Mikoviny
authors.affiliation: Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder Boulder, Colorado, USA ; Department of Chemistry and Biochemistry, University of Colorado Boulder Boulder, Colorado, USA.
authors.forename: Jose L
authors.initials: JL
authors.lastname: Jimenez
authors.affiliation: Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder Boulder, Colorado, USA ; Department of Chemistry and Biochemistry, University of Colorado Boulder Boulder, Colorado, USA.
authors.forename: Pedro
authors.initials: P
authors.lastname: Campuzano-Jost
authors.affiliation: Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder Boulder, Colorado, USA ; Department of Chemistry and Biochemistry, University of Colorado Boulder Boulder, Colorado, USA.
authors.forename: Douglas A
authors.initials: DA
authors.lastname: Day
authors.affiliation: Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder Boulder, Colorado, USA ; Department of Chemistry and Biochemistry, University of Colorado Boulder Boulder, Colorado, USA.
authors.forename: Weiwei
authors.initials: W
authors.lastname: Hu
authors.affiliation: Chemical Sciences Division, Earth System Research Laboratory, NOAA Boulder, Colorado, USA.
authors.forename: Thomas B
authors.initials: TB
authors.lastname: Ryerson
authors.affiliation: Chemical Sciences Division, Earth System Research Laboratory, NOAA Boulder, Colorado, USA ; Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder Boulder, Colorado, USA.
authors.forename: Ilana B
authors.initials: IB
authors.lastname: Pollack
authors.affiliation: Chemical Sciences Division, Earth System Research Laboratory, NOAA Boulder, Colorado, USA ; Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder Boulder, Colorado, USA.
authors.forename: Jeff
authors.initials: J
authors.lastname: Peischl
authors.affiliation: NASA Langley Research Center Hampton, Virginia, USA.
authors.forename: Bruce E
authors.initials: BE
authors.lastname: Anderson
authors.affiliation: NASA Langley Research Center Hampton, Virginia, USA.
authors.forename: Luke D
authors.initials: LD
authors.lastname: Ziemba
authors.affiliation: Department of Chemistry, University of California Irvine, California, USA.
authors.forename: Donald R
authors.initials: DR
authors.lastname: Blake
authors.affiliation: Department of Chemistry, University of California Irvine, California, USA.
authors.forename: Simone
authors.initials: S
authors.lastname: Meinardi
authors.affiliation: NASA Langley Research Center Hampton, Virginia, USA.
authors.forename: Glenn
authors.initials: G
authors.lastname: Diskin
keywords: IEPOX sulfate; aerosol acidity; free troposphere aerosols; glycolic acid sulfate; organosulfate; relative humidity