title: Aerosol Chemistry Resolved by Mass Spectrometry: Linking Field Measurements of Cloud Condensation Nuclei Activity to Organic Aerosol Composition.
abstract: Aerosol hygroscopic properties were linked to its chemical composition by using complementary online mass spectrometric techniques in a comprehensive chemical characterization study at a rural mountaintop station in central Germany in August 2012. In particular, atmospheric pressure chemical ionization mass spectrometry ((-)APCI-MS) provided measurements of organic acids, organosulfates, and nitrooxy-organosulfates in the particle phase at 1 min time resolution. Offline analysis of filter samples enabled us to determine the molecular composition of signals appearing in the online (-)APCI-MS spectra. Aerosol mass spectrometry (AMS) provided quantitative measurements of total submicrometer organics, nitrate, sulfate, and ammonium. Inorganic sulfate measurements were achieved by semionline ion chromatography and were compared to the AMS total sulfate mass. We found that up to 40% of the total sulfate mass fraction can be covalently bonded to organic molecules. This finding is supported by both on- and offline soft ionization techniques, which confirmed the presence of several organosulfates and nitrooxy-organosulfates in the particle phase. The chemical composition analysis was compared to hygroscopicity measurements derived from a cloud condensation nuclei counter. We observed that the hygroscopicity parameter (κ) that is derived from organic mass fractions determined by AMS measurements may overestimate the observed κ up to 0.2 if a high fraction of sulfate is bonded to organic molecules and little photochemical aging is exhibited.
authors.affiliation: Institute for Inorganic Chemistry and Analytical Chemistry, Johannes Gutenberg-University Mainz , 55128 Mainz, Germany.
authors.forename: Alexander L
authors.initials: AL
authors.lastname: Vogel
authors.affiliation: Particle Chemistry Department, Max Planck Institute for Chemistry , 55128 Mainz, Germany.
authors.forename: Johannes
authors.initials: J
authors.lastname: Schneider
authors.affiliation: Institute for Inorganic Chemistry and Analytical Chemistry, Johannes Gutenberg-University Mainz , 55128 Mainz, Germany.
authors.forename: Christina
authors.initials: C
authors.lastname: Müller-Tautges
authors.affiliation: Air Chemistry Department, Max Planck Institute for Chemistry , 55128 Mainz, Germany.
authors.forename: Gavin J
authors.initials: GJ
authors.lastname: Phillips
authors.affiliation: Multiphase Chemistry Department, Max Planck Institute for Chemistry , 55128 Mainz, Germany.
authors.forename: Mira L
authors.initials: ML
authors.lastname: Pöhlker
authors.affiliation: Multiphase Chemistry Department, Max Planck Institute for Chemistry , 55128 Mainz, Germany.
authors.forename: Diana
authors.initials: D
authors.lastname: Rose
authors.affiliation: Institute for Inorganic Chemistry and Analytical Chemistry, Johannes Gutenberg-University Mainz , 55128 Mainz, Germany.
authors.forename: Christoph
authors.initials: C
authors.lastname: Zuth
authors.affiliation: Finnish Meteorological Institute , FI-00560, Helsinki, Finland.
authors.forename: Ulla
authors.initials: U
authors.lastname: Makkonen
authors.affiliation: Finnish Meteorological Institute , FI-00560, Helsinki, Finland.
authors.forename: Hannele
authors.initials: H
authors.lastname: Hakola
authors.affiliation: Air Chemistry Department, Max Planck Institute for Chemistry , 55128 Mainz, Germany.
authors.forename: John N
authors.initials: JN
authors.lastname: Crowley
authors.affiliation: Multiphase Chemistry Department, Max Planck Institute for Chemistry , 55128 Mainz, Germany.
authors.forename: Meinrat O
authors.initials: MO
authors.lastname: Andreae
authors.affiliation: Multiphase Chemistry Department, Max Planck Institute for Chemistry , 55128 Mainz, Germany.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Pöschl
authors.affiliation: Institute for Inorganic Chemistry and Analytical Chemistry, Johannes Gutenberg-University Mainz , 55128 Mainz, Germany.
authors.forename: Thorsten
authors.initials: T
authors.lastname: Hoffmann