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Published October 15, 1999 | Supplemental Material
Journal Article Open

Size and Composition Distribution of Atmospheric Particles in Southern California

Abstract

Continuous measurements of single particle size and chemical composition in the atmosphere are made using aerosol time-of-flight mass spectrometers (ATOFMS) operated alongside more conventional reference air sampling instruments at a network of three urban air monitoring sites in southern California. Electrical aerosol analyzers and optical particle counters are employed to acquire continuous particle size distribution data, and inertial impactor and bulk filter samples with 4-h resolution are taken for determination of particle size and chemical composition. Filter and impactor samples also are taken upwind of the air basin at Santa Catalina Island in order to characterize background air quality. The airborne particle size and composition distribution as measured by the cascade impactors at inland sites differ from that over the ocean principally due to depletion of sea salt particles accompanied by the addition of fine carbon-containing particles and secondary aerosol nitrate. Data from the ATOFMS systems create a continuous time series of sodium-, ammonium-, nitrate-, and carbon-containing particle counts that provide a high-resolution view of differences in particle composition as a function of location in the air basin. Results show that the characteristic peak in the Los Angeles area aerosol mass distribution in the 0.2−0.3-μm size range observed during the 1987 SCAQS experiments has been reduced, consistent with reductions in diesel soot and elemental carbon emissions since that time.

Additional Information

© 1999 American Chemical Society. Received for review August 26, 1998. Revised manuscript received July 6, 1999. Accepted July 20, 1999. The Caltech portion of this work was supported by the U.S. Environmental Protection Agency Center on Airborne Organics under Grant R824970-01-0 and by the Center for Air Quality Analysis at Caltech. The UCRiverside portion of this work was supported by California Air Resources Board under Contract 95-305. Thanks are due to Mr. Joe Cassmassi and the staff of the South Coast Air Quality Management District for assistance with meteorological support for these experiments. Aerosol carbon analyses were performed by Bob Cary at Sunset Laboratory, Inc., Forest Grove, OR. VOC canister analyses were performed by Dr. Rei Rassmussen at BRC/Rassmussen, Portland, OR. INAA analyses were performed by Drs. Ilhan Olmez, Michael Ames, and Jec Gone at the Nuclear Reactor Laboratory, Massachusetts Institute of Technology.

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August 19, 2023
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