title: Drying-Induced Evaporation of Secondary Organic Aerosol during Summer.
abstract: This study characterized the effect of drying on the concentration of atmospheric secondary organic aerosol (SOA). Simultaneous measurements of water-soluble organic carbon in the gas (WSOCg) and particle (WSOCp) phases were carried out in Baltimore, MD during the summertime. To investigate the effect of drying on SOA, the WSOCp measurement was alternated through an ambient channel (WSOCp) and a "dried" channel (WSOCp,dry) maintained at ∼35% relative humidity (RH). The average mass ratio between WSOCp,dry and WSOCp was 0.85, showing that significant evaporation of the organic aerosol occurred due to drying. The average amount of evaporated water-soluble organic matter (WSOM = WSOC × 1.95) was 0.6 μg m(-3); however, the maximum evaporated WSOM concentration exceeded 5 μg m(-3), demonstrating the importance of this phenomenon. The systematic difference between ambient and dry channels indicates a significant and persistent source of aqueous SOA formed through reversible uptake processes. The wide-ranging implications of the work are discussed, and include: new insight into atmospheric SOA formation; impacts on particle measurement techniques; a newly identified bias in PM2.5 measurements using the EPA's Federal Reference and Equivalent Methods (FRM and FEM); atmospheric model evaluations; and the challenge in relating ground-based measurements to remote sensing of aerosol properties.
authors.affiliation: Department of Chemical, Biochemical and Environmental Engineering, University of Maryland , Baltimore County, Baltimore, Maryland 21250, United States.
authors.forename: Marwa M H
authors.initials: MM
authors.lastname: El-Sayed
authors.affiliation: Department of Chemical, Biochemical and Environmental Engineering, University of Maryland , Baltimore County, Baltimore, Maryland 21250, United States.
authors.forename: Dziedzorm
authors.initials: D
authors.lastname: Amenumey
authors.affiliation: Department of Chemical, Biochemical and Environmental Engineering, University of Maryland , Baltimore County, Baltimore, Maryland 21250, United States.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Hennigan
mesh_terms: D000336:Aerosols / Q000032:analysis*; D001272:Atmosphere / Q000737:chemistry; D015142:Baltimore; D002244:Carbon / Q000737:chemistry; D003890:Desiccation; D005740:Gases / Q000737:chemistry; D006813:Humidity; D009930:Organic Chemicals / Q000032:analysis*; D012621:Seasons; D012995:Solubility; D014835:Volatilization; D014867:Water / Q000737:chemistry
chemical_list: D000336:Aerosols; D005740:Gases; D009930:Organic Chemicals; D014867:Water; D002244:Carbon