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FIELD EVALUATION OF SAMPLERS FOR EPA'S NATIONAL PM 2.5 CHEMICAL SPECIATION NETWORK-PRELIMINARY RESULTS FROM ATLANTA
Citation:
Solomon, P A., W J. Mitchell, D B. Gemmill, M P. Tolocka, G A. Norris, AND R W. Wiener. FIELD EVALUATION OF SAMPLERS FOR EPA'S NATIONAL PM 2.5 CHEMICAL SPECIATION NETWORK-PRELIMINARY RESULTS FROM ATLANTA. Presented at Real World 2000, Clean Air Conference, Atlanta, GA, May 15-18, 2000.
Impact/Purpose:
The core aerosol research for FY01 includes evaluation of newly developed and developing methods for the chemical analysis and sampling of PM in ambient air, especially state-of-the-art continuous and non-invasive aerosol measurement methods, and the study of the aerosol sampling processes to better assess the true aerosol concentration and size distributions observed in the ambient environment. An additional emphasis is placed on integrated sampling for stable and semi-volatile organic aerosol species. This latter area addresses the state-of-the-art in this measurement area. This program supports Title I of the Clean Air Act in its mandate for performing research to support the NAAQS, GPRA goal 1.1.5, and ORD's main research objective on PM.
Much of this work directly supports OAQPS and may be applied within the Supersites Program managed jointly by OAQPS and ORD. This research also will support many of ORD's long-term research goals by providing more reliable information (decrease uncertainty) on ambient aerosols that can be utilized for characterizing risk.
Finally, an APM, has been established to develop measurement methods for causal factors, due in 2004. Currently, there are a number of causal factor hypotheses, but none have sufficient evidence to support developing one measurement/analytical method over another. The PM methods team will support and work with Joellen Lewtas on methods for the collection and analysis of semi-volatile and aerosol phase organic species to help address this APM. The PM methods team will continue to work within the Supersites program and with OAQPS and their new partners in ORIA to further evaluate continuous species specific methods and aerosol physical property measurement methods.
Description:
The US EPA bas established a national network at nearly 1100 sites to monitor PM2.5 mass for testing compliance with the PM2.5 National Ambient Air Quality Standards. The objective of the field evaluation is to determine the performance characteristics for the collection of the chemical components of PM2.5 by the chemical speciation monitors developed for the national PM2.5 network relative to each other, to the Federal Reference Method (FRM), and to other historically accepted monitors. The samplers were initially compared in 4 cities throughout the US during January and February of 1999. The evaluations in Atlanta during August of 1999 represent a summertime test of these samplers. The samplers were compared for PM, mass, sulfate, nitrate, ammonium, OC, EC, and 10 elements. While the FRM is the standard for mass, there are no such standards for the chemical components of PM2.5, Thus, these intercomparison studies established equivalency among methods on a species by species basis. For volatile species (e.g., ammonium nitrate and semi-volatile organic compounds), the FRM provides only a lower limit on the expected mass loading for that species, as there is potential for loss of these species from the inert Teflon filters. For stable species, the FRM should provide an accurate estimate of the mass loading for those species. The historical samplers will provide an additional set of samples for comparison; however, they still can only be compared on an equivalent basis as none represent a reference method sampler.
Statistical analysis of the data involved comparisons among the different samplers to examine differences in the determined chemical components due to sampler design characteristics. The preliminary results of the Atlanta study will be presented and differences found among the samplers performance will be discussed in light of sampler characteristics. Results will also be compared to the 4 City Study intercomparison.
This work has been funded wholly or in part by the United States Environmental Protection Agency. Portions of the work were performed under Contract No. 68-D5-0040 by Research Triangle Institute. It has been subjected to Agency review and approved for publication. Mention of trade names or commercial products does not constitute endorsement or recommendation for use.