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The Relationship Between Real-Time and Time-Integrated Coarse (2.5-10mm), Intermediate (1-2.5MM), and Fine (<2.5MM) Particulate Matter in the Los Angeles Basin

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Abstract: Population exposure to ambient particulate matter (PM) has received considerable attention due to the association between ambient particulate concentrations and mortality. Current toxicological and epidemiological studies and controlled human and animal exposures suggest that all size fractions of PM may be responsible for observed health effects. Recently, the governments of European countries and the U.S. have been discussing a new PM1 standard. The purpose of this standard is to preclude invasion of coarse particles into the fine PM mode. This notion is predicated on evidence that suggests that PM1-2.5 is dominated by coarse PM.

In this study, coarse (PM10-PM2.5), intermodal (PM1-2.5), and fine (PM2.5) PM mass concentrations in four different sites are measured with both continuous and time-integrated sampling devices. Two source sites, USC and Downey, CA and two receptor sties, Claremont and Riverside, CA, were monitored for at least three months each. The main objective is to document both short-term and diurnal variations in ambient fine, intermodal, and coarse particulate mass concentrations with respect to each other while considering the effects of sources, weather, wind speed, and wind direction. Of particular interest are the relationships between PM1 and PM1-2.5 and coarse PM with PM1-2.5. Results show strong correlations between PM1 and intermodal PM in receptor sites. These two modes in source sites show moderate correlation (R2~0.5). The contribution of PM1-2.5 to PM2.5 shows seasonal variation with the largest contribution in the summer months, most likely due to enhanced long range transport. Coarse PM is poorly correlated with intermodal PM in USC and Riverside. The correlation is dependent upon the mass concentration at Claremont, with smaller mass concentrations being moderately-to-well-correlated. This correlation becomes moderate in Downey, most likely because the local freeway is a source of all particle sizes. Continuous data yield insight into the possibility that PM1 is growing into PM1-2.5 via a complex process that involves stagnation of the ambient aerosol during high relative humidity conditions, followed by advection during daytime hours.

This is an abstract of a proposed presentation and does not necessarily reflect the United States Environmental Protection Agency (EPA) policy. The actual presentation has not been peer reviewed by EPA. Mention of trade names or commercial products does not constitute endorsement or recommendation for use.
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Citation:Geller, M. D., P. M. Fine, C. Sioutas, and P. A. Solomon. The Relationship Between Real-Time and Time-Integrated Coarse (2.5-10mm), Intermediate (1-2.5MM), and Fine (<2.5MM) Particulate Matter in the Los Angeles Basin. Presented at American Association for Aerosol Research, Anaheim, CA, October 20-24, 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: Abstrct/Oral
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Presented: 10/23/2003
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Related Entries:
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Bullet Item PM Supersites Program
spacer Relationship Reason:   A Project of the Product
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