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A Comparison of Particle Mass Spectrometers During the 1999 Atlanta Supersites Experiment

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Abstract: During the Atlanta SuperSite Experiment, four particle mass spectrometers were operated together for the first time: NOAA's PALMS (Particle Analysis by Laser Mass Spectrometry), U. C. Riverside's ATOFMS (Aerosol Time-of-Flight Mass Spectrometry), U. Delaware's RSMS-II (Rapid Single-Particle Mass Spectrometer II), and Aerodyne's AMS (Aerosol Mass Spectrometer). 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. 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 about 0.2 and 0.35 um, 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 the quantitative semi-continuous measurements (r 2 = 0.93). In contrast, the PALMS nitrate/sulfate ion ratios were only moderately correlated (r 2 ~ 0.7).

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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Citation:Middlebrook, A. M., D. M. Murphy, S. H. Lee, D. S. Thomson, K. A. Prather, R. J. Wenzel, D. Y. Liu, D. J. Phares, K. P. Rhoads, A. S. Wexler, M. V. Johnston, J. L. Jiminez, J. T. Jayne, D. R. Worsnop, I. Yourshaw, J. H. Seinfeld, R. C. Flagan, S. V. Hering, R. J. Weber, P. Jongejan, J. Slanina, and P. K. Dasgupta. A Comparison of Particle Mass Spectrometers During the 1999 Atlanta Supersites Experiment. JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES 108(D7):SOS 12-1 - 12-13, (2003).
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Contact: Liz Hope - (919) 541-2785 or hope.elizabeth@epa.gov
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Division: Human Exposure & Atmospheric Sciences Division
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Branch: Process Modeling Research Branch
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Product Type: Journal
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Published: 04/01/2003
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Bullet Item A Comparison of Particle Mass Spectrometers During the 1999 Atlanta Supersites Experiment
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Related Entries:
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Bullet Item PM Supersites Program
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