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COMPARISON OF INTEGRATED SAMPLERS FOR MASS AND COMPOSITION DURING THE 1999 ATLANTA SUPERSITES PROJECT
Citation:
Solomon, P A., K. Baumann, E. Edgerton, R. Tanner, D J. Eatough, W. Modey, H. Marin, D. Savoie, S. Natarajan, M. B. Meyer, AND G A. Norris. COMPARISON OF INTEGRATED SAMPLERS FOR MASS AND COMPOSITION DURING THE 1999 ATLANTA SUPERSITES PROJECT. JOURNAL OF GEOPHYSICAL RESEARCH: ATMOSPHERES 108(D7):SOS 11-1 - SOS 11-26, (2003).
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 first of EPA's Particulate Matter (PM) Supersites projects was established in Atlanta, GA during the summer of 1999 in conjunction with the Southern Oxidants Study. The short-term primary focus was a one month intensive field campaign to evaluate advanced PM measurement methods for measuring PM mass and the chemical and physical properties of PM. Long-term objectives are being met through coordination and cooperation with existing programs in Atlanta and the southeastern U.S. Three categories of PM instruments were deployed during August 1999: time-integrated or discrete filter based methods like those used in EPA's PM2.5 Chemical Speciation Network; continuous or semi-continuous species specific methods, most of which are still in development; and single particle mass spectrometers, the most advanced methods looking at the chemical composition of single particles. The focus of this paper is on comparison of the discrete filter based methods. Samples were collected by 12 discrete filter-based samplers on an every other day basis during the study period at the Jefferson Street SEARCH (Southeastern Aerosol Research and Characterization) study site. Samples were analyzed for PM2.5 mass, sulfate, nitrate, ammonium, organic carbon, elemental carbon, and trace elements, the latter by XRF. Samplers used a variety of filters, denuder-filter combinations in the case of nitrate and organic carbon, particle size fractionating devices, and flow rates. Ambient concentrations for most species were sufficiently above detection limits for testing comparability among samplers with nitrate being the most notable exception for the major components having an average reported value of 0.5 ug/m3. Several trace species, e.g., As and Pb, also were often below limits of detection of the analysis method.
Results indicate real differences exist among the samplers tested for most species, with sulfate and ammonium being the exceptions, under the conditions tested. Differences are due to sampler design and in the case of elemental carbon also due to the use of different chemical analysis methods. Comparability among most of the samplers for a given species was: mass (plus/minus 20%); sulfate (plus/minus 10%); nitrate (plus/minus 30-35%); ammonium (plus/minus 10-15%); organic carbon either with or without denuders (plus/minus 20%) or including samplers both with and without denuders (plus/minus 35-45%); elemental carbon (plus/minus 20 to +/- 200%, the latter if different analysis methods are used); and minor and trace elements (plus/minus 20-30%). A net organic carbon sampling artifact on quartz-fiber filters was estimated from the comparison of denuded versus undenuded samples and is in the range of 1-4 ug/m3.
The US EPA through its Office of Research and Development (funded and managed or partially funded and collaborated in) the research described here under Contract # 68-D-00-206 to Research Triangle Institute. It has been subjected to Agency review and approved for publication.