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Published April 16, 2003 | Published
Journal Article Open

A comparison of particle mass spectrometers during the 1999 Atlanta Supersite Project


During the Atlanta Supersite Project, four particle mass spectrometers were operated together for the first time: NOAA's Particle Analysis by Laser Mass Spectrometer (PALMS), University of California at Riverside's Aerosol Time-of-Flight Mass Spectrometer (ATOFMS), University of Delaware's Rapid Single-Particle Mass Spectrometer II (RSMS-II), and Aerodyne's Aerosol Mass Spectrometer (AMS). Although these mass spectrometers are generally classified as similar instruments, they clearly have different characteristics due to their unique designs. One primary difference is related to the volatilization/ionization method: PALMS, ATOFMS, and RSMS-II utilize laser desorption/ionization, whereas particles in the AMS instrument are volatilized by impaction onto a heated surface with the resulting components ionized by electron impact. Thus mass spectral data from the AMS are representative of the ensemble of particles sampled, and those from the laser-based instruments are representative of individual particles. In addition, the AMS instrument cannot analyze refractory material such as soot, sodium chloride, and crustal elements, and some sulfate or water-rich particles may not always be analyzed with every laser-based instrument. A main difference among the laser-based mass spectrometers is that the RSMS-II instrument can obtain size-resolved single particle composition information for particles with aerodynamic diameters as small as 15 nm. The minimum sizes analyzed by ATOFMS and PALMS are 0.2 and about 0.35 μm, respectively, in aerodynamic diameter. Furthermore, PALMS, ATOFMS, and RSMS-II use different laser ionization conditions. Despite these differences the laser-based instruments found similar individual particle classifications, and their relative fractions among comparable sized particles from Atlanta were broadly consistent. Finally, the AMS measurements of the nitrate/sulfate mole ratio were highly correlated with composite measurements (r^2 = 0.93). In contrast, the PALMS nitrate/sulfate ion ratios were only moderately correlated (r^2 ∼ 0.7).

Additional Information

© 2003 by the American Geophysical Union. Received 23 March 2001; revised 31 January 2002; accepted 5 February 2002; published 10 April 2003. We thank Eric Edgerton (ARA) for assisting with the logistics of bringing the four instruments together in Atlanta. Deborah Gross, Alex Barron, and Ben Warren (Carleton College) and Rebecca Washenfelder (CalTech) are gratefully acknowledged for their assistance with acquiring data. We also thank Susanne Hering (ADI) for the composite measurements of sulfate and nitrate as well as Peter McMurry (UMinn) for the particle density data. This work was funded in part by the U. S. EPA, NARSTO (Southern Oxidants Study), and Georgia Institute of Technology (SCISSAP).

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