United States Environmental Protection Agency Office of Research and Development National Exposure Research Laboratory FY02 Research Abstract Government Performance Results Act (GPRA) Goal 1 APM23 Significant Research Findings: Guidelines for the Application of SEM/EDX Analytical Techniques to Particulate Matter Samples In July 1997, the U.S. Environmental Protection Agency (EPA) promulgated a new National Ambient Air Quality Standard (NAAQS) for particulate matter (PM). The new standard is aimed at regulating ambient concentrations of PM10 and PM25, particles with aerodynamic diameter <10 fj.m and <2.5 fj.m, respectively. The new NAAQS was developed in response to studies that showed a significant association between human morbidity and mortality and PM concentrations. Additional studies indicate that transition metals may play a significant role in the health consequences of particle exposure. These studies coupled with the new NAAQS have generated increased interest in analytical techniques capable of measuring the size, morphology, and chemical composition of individual aerosol particles. These data are essential to the understanding of particle formation, transport and transforma- tion, and deposition mechanisms as well as the impact of particles deposited in the respiratory system. Furthermore, chemical and physical characteriza- tion of individual particles can reveal source information that cannot be determined through bulk chemical characterization such as X-ray fluor- escence (XRF). Individual particle analysis is thus a complement to bulk elemental analysis techniques as well as a potentially powerful tool in source apportionment research. Research The National Exposure Research Laboratory (NERL) of the U.S. EPA has Approach been developing and evaluating the use of scanning electron microscopy (SEM) combined with energy-dispersive x-ray analysis (EDX) to characterize coarse and fine ambient and source-derived particles. With the SEM/EDX analysis technique, particles can be imaged by SEM, providing information on the physical properties of particles including size, shape, and surface morphology, while EDX provides information on the chemistry of individual particles. SEM/EDX can be conducted both manually and in a computer-controlled fashion (CCSEM). Results of this research and development work are presented in an EPA report entitled "Guidelines for the Application of SEM/EDX Analytical Scientific Problem and Policy Issues National Exposure Research Laboratory — November 2002 ------- Techniques to Particulate Matter Samples. The document provides an introduction to the SEM/EDX techniques, including basic concepts and hardware, and a description of the NERL SEM/EDX facilities. Procedures are recommended for sample preparation and analysis. Research related to SEM/EDX data validity and quality assurance and quality control issues conducted by the NERL and others is presented, with recommendations specific to the air particle analysis application. Finally, examples of research applications are presented. Results and The present document, which evolved over several years as a product of Implications research carried out in support of the U.S. EPA/NERL SEM/EDX Laboratory, provides guidelines for researchers using SEM/EDX in both a manual and computer-controlled fashion for aerosol characterization and source apportionment. The document fulfills the requirements of Annual Performance Measure (APM) 23, which helps to attain Annual Performance Goal (APG) 24 under Government Performance Results Act (GPRA) Goal 1.1.8. APM 23 contributes to GPRA 1.1.8 goal and objectives by 1) providing techniques to improve understanding of the relationship among PM sources, ambient concentrations, and human exposure and 2) enhancing receptor modeling capabilities, thus improving the chances for successful SIP strategies and NAAQS compliance. Results of this research and development work (conducted by the NERL principal investigator for SEM/EDX and by scientists of ManTech Environmental Technology, Inc. under contract to NERL) are presented in the following EPA report: "Guidelines for the Application of SEM/EDX Analytical Techniques to Particulate Matter Samples," R. Willis, F. Blanchard, T. Conner, EPA Report No. 600/R-02/070, September 2002. Future Research Future development and applications of SEM/EDX will directly support the NERL long-term research goals. SEM/EDX techniques will be used to support the application of source apportionment techniques to personal and indoor air samples. In addition, SEM/EDX analyses will be used to confirm multi-variate source apportionment model results as well as demonstrate limits of the models using ambient data. To further enhance source apportionment modeling techniques, individual particle data obtained by SEM/EDX will be applied directly in one or more multi-variate source apportionment models. Research Collaboration and Publications National Exposure Research Laboratory — November 2002 ------- Contacts for Additional Information Questions and inquiries can be directed to: Teri L. Conner, Ph.D. U.S. EPA, Office of Research and Development National Exposure Research Laboratory (D205-03) Research Triangle Park, NC, 27711 Phone: 919/541-3157 E-mail: conner.teri@epa.gov Federal funding for this research was administered under EPA contracts 68- D5-0049 and 69-D-00-206. National Exposure Research Laboratory — November 2002 ------- |