title: Measuring Mass-Based Hygroscopicity of Atmospheric Particles through in Situ Imaging.
abstract: Quantifying how atmospheric particles interact with water vapor is critical for understanding the effects of aerosols on climate. We present a novel method to measure the mass-based hygroscopicity of particles while characterizing their elemental and carbon functional group compositions. Since mass-based hygroscopicity is insensitive to particle geometry, it is advantageous for probing the hygroscopic behavior of atmospheric particles, which can have irregular morphologies. Combining scanning electron microscopy with energy dispersive X-ray analysis (SEM/EDX), scanning transmission X-ray microscopy (STXM) analysis, and in situ STXM humidification experiments, this method was validated using laboratory-generated, atmospherically relevant particles. Then, the hygroscopicity and elemental composition of 15 complex atmospheric particles were analyzed by leveraging quantification of C, N, and O from STXM, and complementary elemental quantification from SEM/EDX. We found three types of hygroscopic responses, and correlated high hygroscopicity with Na and Cl content. The mixing state of 158 other particles from the sample broadly agreed with those of the humidified particles, indicating the potential to infer atmospheric hygroscopic behavior from a selected subset of particles. These methods offer unique quantitative capabilities to characterize and correlate the hygroscopicity and chemistry of individual submicrometer atmospheric particles.
authors.affiliation: Chemical Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
authors.forename: Dominique S
authors.initials: DS
authors.lastname: Piens
authors.affiliation: Chemical Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
authors.forename: Stephen T
authors.initials: ST
authors.lastname: Kelly
authors.affiliation: Chemical Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.|Department of Chemistry, University of California , Berkeley, California 94720, United States.
authors.forename: Tristan H
authors.initials: TH
authors.lastname: Harder
authors.affiliation: Department of Marine Earth and Atmospheric Sciences, North Carolina State University , Raleigh, North Carolina 27695, United States.
authors.forename: Markus D
authors.initials: MD
authors.lastname: Petters
authors.affiliation: Chemical Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
authors.forename: Rachel E
authors.initials: RE
authors.lastname: O'Brien
authors.affiliation: William R. Wiley Environmental and Molecular Sciences Laboratory, Pacific Northwest National Laboratory , Richland, Washington 99352, United States.
authors.forename: Bingbing
authors.initials: B
authors.lastname: Wang
authors.affiliation: Atmospheric Radiation Monitoring (Southern Great Plains Climate Research Facility), 109596 Coal Road, Billings, Oklahoma 74630 United States.
authors.forename: Ken
authors.initials: K
authors.lastname: Teske
authors.affiliation: Atmospheric Radiation Monitoring (Southern Great Plains Climate Research Facility), 109596 Coal Road, Billings, Oklahoma 74630 United States.
authors.forename: Pat
authors.initials: P
authors.lastname: Dowell
authors.affiliation: William R. Wiley Environmental and Molecular Sciences Laboratory, Pacific Northwest National Laboratory , Richland, Washington 99352, United States.
authors.forename: Alexander
authors.initials: A
authors.lastname: Laskin
authors.affiliation: Chemical Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
authors.forename: Mary K
authors.initials: MK
authors.lastname: Gilles
mesh_terms: D000336:Aerosols / Q000737:chemistry; D002244:Carbon; D008855:Microscopy, Electron, Scanning; D010316:Particle Size; D017155:Wettability
chemical_list: D000336:Aerosols; D002244:Carbon