HR: 1340h
AN: A13B-1180    [Abstracts]
TI: Analysis of Aerosol Mass Spectrometer Data in Pittsburgh, Mexico City, and Blodgett Forest by Positive Matrix Factorization
AU: * Ulbrich, I M
EM: ulbrich@colorado.edu
AF: Department of Chemistry and Biochemistry and CIRES, Univeristy of Colorado, Boulder, CO 80309, United States
AU: Zhang, Q
EM: qz@asrc.cestm.albany.edu
AF: Atmospheric Sciences Research Center, State University of New York, Albany, NY 12203, United States
AU: Canagaratna, M
EM: mrcana@aerodyne.com
AF: Aerodyne Research, Inc., 45 Manning Road, Billerica, MA 01821, United States
AU: Salcedo, D
EM: dara@ciq.uaem.mx
AF: Centro de Investigaciones Quimicas, Universidad Autonoma del Estado de Morelos, Cuernavaca, 62209, Mexico
AU: Dzepina, K
EM: katja.dzepina@coloado.edu
AF: Department of Chemistry and Biochemistry and CIRES, Univeristy of Colorado, Boulder, CO 80309, United States
AU: Farmer, D
EM: delphine.farmer@colorado.edu
AF: Department of Chemistry and Biochemistry and CIRES, Univeristy of Colorado, Boulder, CO 80309, United States
AU: Docherty, K
EM: kenneth.docherty@colorado.edu
AF: Department of Chemistry and Biochemistry and CIRES, Univeristy of Colorado, Boulder, CO 80309, United States
AU: Worsnop, D R
EM: worsnop@aerodyne.com
AF: Atmospheric Sciences Research Center, State University of New York, Albany, NY 12203, United States
AU: Jimenez, J L
EM: jose.jimenez@colorado.edu
AF: Department of Chemistry and Biochemistry and CIRES, Univeristy of Colorado, Boulder, CO 80309, United States
AB: Mass spectrometric measurements of ambient aerosols yield organic spectra that are a mix of nucleated particles, freshly emitted particles from many sources, and particles which have undergone some amount of processing (condensation, oxidative reaction, cloud processing, etc.). Further understanding of the important sources and processes for organic aerosols requires deconvolution of the organic fraction of ambient aerosols. A well-known source apportionment technique, Positive Matrix Factorization (PMF), has been applied to Aerodyne aerosol mass spectrometer (Q-AMS and HR-ToF-AMS) datasets acquired in Pittsburgh (2002), Mexico City (2003), Blodgett Forest (2007) and other sites. Sensitivity analysis of the Pittsburgh case is performed with synthetic datasets and characterizes the behaviour of PMF with AMS datasets. PMF is a least-squares fitting method for source apportionment commonly applied to speciated aerosol datasets (Paatero, Chemomet. Intell. Lab. Sys. 1997, 37, 23-35). The structure and precision of the AMS dataset are significantly different from datasets compiled from previous measurements of multiple aerosol components (metals, organic and elemental carbon, ions, etc.), are very large (~300 points per sample, with ~3000-10,000 samples for these campaigns), and fragmentation of molecules during ionization gives each mass spectrum strongly interrelated data. Additionally, because the Aerodyne AMS does not detect elemental carbon or metals (common and important in most PMF analyses), application of this technique to AMS data yields significantly different source profiles than in previous PMF studies. Each site has a hydrocarbon-like organic aerosol (HOA) factor that is likely primary OA and multiple oxygenated organic aerosol (OOA) factors that are likely secondary OA, and biomass burning organic aerosol (BBOA) can be separated in some locations. The OOA factors always include one highly-oxygenated factor (OOA-I) that resembles the spectrum of fulvic acid and less-oxygenated factors that resemble spectra from chamber studies of SOA. Assignment of factor spectra to these categories is aided by comparison to spectra collected by many research groups using the Aerodyne AMS to measure individual compounds, reactions in smog chambers, and primary emission sources. These spectra have been compiled in a publicly-available database (http://cires.colorado.edu/jimenez-group/AMSsd/spectra.html).
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0325 Evolution of the atmosphere (1610, 8125)
DE: 0345 Pollution: urban and regional (0305, 0478, 4251)
DE: 0365 Troposphere: composition and chemistry
DE: 0394 Instruments and techniques
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting