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INTERCOMPARISON OF NEAR REAL-TIME MONITORS OF PM2.5 NITRATE AND SULFATE AT THE U.S. ENVIRONMENTAL PROTECTION AGENCY ATLANTA SUPERSITE
Citation:
Weber, R., D. Orsini, Y. Duan, K. Baumann, C. S. Kiang, W. L. Chameides, Y. N. Lee, F. Brechtel, P. Klotz, P. Jongejan, H. ten Brink, J. Slanina, C. B. Boring, Z. Genfa, P. Dasgupta, S. Hering, M. Stolzenburg, D. D. Dutcher, E. Edgerton, B. Hartsell, P A. Solomon, AND R. Tanner. INTERCOMPARISON OF NEAR REAL-TIME MONITORS OF PM2.5 NITRATE AND SULFATE AT THE U.S. ENVIRONMENTAL PROTECTION AGENCY ATLANTA SUPERSITE. JOURNAL OF GEOPHYSICAL RESEARCH: ATMOSPHERES 108(D7):9-1 to 9-13, (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:
Five new instruments for semi-continuous measurements of fine particle (PM2.5) nitrate and sulfate were deployed at the Atlanta Supersite Experiment during an intensive study in August 1999. The instruments measured bulk aerosol chemical composition at rates ranging from every 5 minutes to once per hour. The techniques included a filter sampling system with automated water extraction and on-line ion chromatographic analysis (IC), two systems that directly collected particles into water for IC analysis, and 2 techniques that converted aerosol nitrate or sulfate either catalytically or by flash vaporization to gaseous products that were measured with gas analyzers. During the one-month study 15-minute integrated nitrate concentrations were low ranging from about 0.1 to 3.5 ug m-3 with a mean value of 0.5 ug m-3. Ten-minute integrated sulfate concentrations varied between 0.3 and 40 ug m-3 with a mean of 14 ug m-3. By the end of the one-month study most instruments were in close agreement with r-squared values between instrument pairs typically ranging from 0.7 to 0.94. Based on comparison between individual semi-continuous devices and 24-h integrated filter measurements, most instruments were within 20 to 30% for nitrate (~0.1-0.2 ug m-3) and 10 to 15% for sulfate (1-2 ug m-3). Within 95% confidence intervals, linear regression fits suggest no biases existed between the semi-continuous techniques and the 24-h integrated filter measurements of nitrate and sulfate, however, for nitrate, the semi-continuous intercomparisons showed significantly less variability than intercomparisons amongst the 24-h integrated filters.
The United States Environmental Protection Agency through its Office of Research and Development (funded and managed or partially funded and collaborated in) the research described here under (CR824849) to the Georgia Institute of Technology. It has been subjected to Agency review and approved for publication.