Ambient aerosol sampling using the Aerodyne Aerosol Mass Spectrometer

Creators: Jimenez, Jose L.; Jayne, John T.; Shi, Quan; Kolb, Charles E.; Worsnop, Douglas R.; Yourshaw, Ivan; Seinfeld, John H.; Flagan, Richard C.; Zhang, Xuefeng; Smith, Kenneth A.; Morris, James W.; Davidovits, Paul

Abstract

The Aerodyne Aerosol Mass Spectrometer (AMS) has been designed to measure size-resolved mass distributions and total mass loadings of volatile and semivolatile chemical species in/on submicron particles. This paper describes the application of this instrument to ambient aerosol sampling. The AMS uses an aerodynamic lens to focus the particles into a narrow beam, a roughened cartridge heater to vaporize them under high vacuum, and a quadrupole mass spectrometer to analyze the vaporized molecules. Particle size is measured via particle time-of-flight. The AMS is operated in two modes: (1) a continuous mass spectrum mode without size information; and (2) a size distribution measurement mode for selected m/z settings of the quadrupole. Single particles can also be detected and sized if they have enough mass of a chemical component. The AMS was deployed at a ground sampling site near downtown Atlanta during August 1999, as part of the Environmental Protection Agency/Southern Oxidant Study Particulate Matter "Supersite" experiment, and at a suburban location in the Boston area during September 1999. The major observed components of the aerosol at both sites were sulfate and organics with a minor fraction of nitrate, consistent with prior studies and colocated instruments. Different aerosol chemical components often had different size distributions and time evolutions. More than half of the sulfate mass was contained in 2% of the ambient particles in one of the sampling periods. Trends in mass concentrations of sulfate and nitrate measured with the AMS in Atlanta compare well with those measured with ion chromatography-based instruments. A marked diurnal cycle was observed for aerosol nitrate in Atlanta. A simple model fit is used to illustrate the integration of data from several chemical components measured by the AMS together with data from other particle instruments into a coherent representation of the ambient aerosol.

Additional Information

© 2003 American Geophysical Union. Received 25 July 2001; revised 2 September 2002; accepted 13 September 2002; published 15 April 2003. The authors are grateful to Rodney Weber and Douglas Orsini of the Georgia Institute of Technology (GIT) and Yin-Nan Lee of Brookhaven National Laboratory for the ongoing collaboration that has greatly helped the development and testing of the AMS. We thank Bill Chameides and C.S. Kiang of GIT and Eric Edgerton of Atmospheric Research and Analysis, Inc. for the organization and support of the Atlanta Supersite experiment. We also thank Sjaak Slanina of the Netherlands Energy Research Foundation (ECN) for allowing us to use their data; and Bob Prescott of Aerodyne for his logistical support during the experiments. Financial support for the development of the instrument was provided by the National Science Foundation (grant DMI-9705610) and the Office of Naval Research (grant N00014-98-C-0266). Our participation in the Atlanta field campaign was funded by the EPA/Southern Oxidants Study (grant CR 824849-01).

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