Research Projects

Project at a Glance

Project Status: complete

Title: Size-time-compositional analyses of aerosols during SCAQS

Principal Investigator / Author(s): Cahill, Thomas A

Contractor: Air Quality Group, Crocker Nuclear Laboratory, UC Davis

Contract Number: A732-074

Research Program Area: Atmospheric Processes


This report describes the work done by the Air Quality Group of Crocker Nuclear Laboratory in the 1987 Southern California Air Quality Study. The main objective of the study was to form a comprehensive data base of aerosol and meteorological measurements in the South Coast Air Basin for further air quality and meteorological studies. Our participation in SCAQS consisted of monitoring four sites in the Los Angeles basin with high size-time-compositional resolution, emphasizing the fine aerosols that impact visibility. The subsequent analyses from two sampling methods (nine-stage impactors for high size resolution and cyclone samplers with teflon filters for high compositional sensitivity) led to a relatively complete elemental characterization of fine aerosols with their size distribution. Sampling and analysis methods are described along with their results and quality assurance.

Eighty to ninety percent of the fine aerosol mass was accounted for by the elements from H to Pb, while hydrogen had surprisingly high correlations with mass (R-squares from 0.88 to 0.99). The size resolved elemental data showed that sulfur had complicated size and time patterns across the Los Angeles Basin with two important patterns emerging in the optically important size region for sulfur from 0.34 to 2.12 Ķm. There can be a growth in total sulfur concentration with a constant size profile or there can be a change to a coarser size fraction, generally but not always with increasing concentration. This suggest there are two different formation modes for sulfur.


For questions regarding this research project, including available data and progress status, contact: Heather Choi at (916) 322-3893

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