AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
Abstract View
Detection and Quantification of Organic Aerosol Species with Thermal Vaporization-Electron Impact Ionization in the Aerodyne Aerosol Mass Spectrometer
WEN XU, Manjula Canagaratna, Philip Croteau, Andrew Lambe, Leah Williams, Lindsay Renbaum-Wolff, Timothy Onasch, John Jayne, Douglas Worsnop, Aerodyne Research, Inc.
Abstract Number: 241 Working Group: Instrumentation and Methods
Abstract Organic aerosol (OA) constitutes a large fraction of the ambient submicron particulate mass. Real-time detection and quantification of OA is complicated by the fact that it consists of hundreds of individual species. In the Aerodyne aerosol mass spectrometer (AMS), OA is detected via a two-step process of thermal vaporization and electron impact ionization. Quantification of the detected OA mass is dependent on empirically parameterized particle collection efficiency and relative ionization efficiencies (RIE). In this study we compare OA measurements obtained with a standard AMS vaporizer (where solid particles are known to experience particle bounce) and a capture vaporizer that has near unity particle collection efficiency. Commercially available organic species with varying functionalities are used on their own or as mixed solutions with ammonium nitrate (the primary calibrant of AMS ionization efficiency) to generate pure as well as mixed aerosol particles in the laboratory. Secondary organic aerosols generated with a Potential Aerosol Mass (PAM) oxidation flow reactor are also examined. We utilize the results to obtain more detailed information about the OA detection process and to evaluate the current empirical parameterization of RIE that is utilized in AMS quantification of organics.