Impact/Purpose:

The NERL SEM/EDX facility was established to provide a state-of-the-art resource for individual particle analysis. Specific goals of the laboratory are as follows: 1) Provide chemical, morphological, and size characterization of particles in support of ambient air characterization studies, source apportionment, exposure and health studies, and other particulate matter research.; 2) Develop analytical capabilities to support research objectives; 3) Communicate results to clients and the scientific community.

Description:

Computer-controlled scanning electron microscopy combined with individual-particle X-ray analysis (CCSEM or SEM/EDX) is being used to measure the chemical and physical characteristics of ambient and source-derived particles. CCSEM can determine particle size, shape and major chemistry on particles larger than approximately 0.3 - 0.5 Fm, depending on particle composition and other factors. Photomicrographs of individual particles can be acquired to provide particle morphology. Statistical methods or user-defined classification rules are used to sort particles into distinct particle classes based on chemical and physical characteristics to aid in source identification. Chemical and physical characterization of individual particles can potentially reveal source information which cannot be determined through bulk chemical analysis, such as x-ray fluorescence.

Most projects for this task support human exposure, particle resuspension, and methods evaluation and will be conducted through in-house contract support, with additional technical support and overall program management from the EPA principal investigator. SEM and source apportionment methods will be developed in conjunction with a Cooperative Research and Development Agreement (CRADA) between the EPA's National Exposure Research Laboratory (NERL) and R.J. Lee Group, Inc.(Monroeville, PA).

Record Details:

Record Type:PROJECT

Start Date:10/01/2004

Projected Completion Date:10/01/2007

Record ID: 15836

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Project Information:

Progress :Work continued on the third year of a CRADA between the NERL and R.J. Lee Group, Inc. The overall goal of this CRADA is to advance the state-of-the-science of SEM/EDX and CCSEM techniques for the chemical and physical characterization of particles found in outdoor and indoor air. Research areas addressed include computer-controlled analysis techniques, particle classification, and source apportionment methods for SEM data.

Samples from the EPA's National Health and Environmental Effects Laboaratory (NHEERL) Coarse Particle Concentrator Study were analyzed by SEM/EDX to characterize the chemical composition and size distribution of the particles and, if possible, determine the contribution of bioaerosols (e.g., spores, bacteria) to coarse particle mass. Analyses of these samples not only addressed the NHEERL objectives, but addressed another of the CRADA objectives, which is to evaluate and recommend approaches to the SEM/EDX and CCSEM analysis of carbonaceous and other light-element particles.

Particles on carpet-fiber samples from EPA's National Risk Management Research Laboaratory (NRMRL) were analyzed to determine the size distribution of particles attached to the carpet fibers as a function of distance along the fiber. These data will be compared with data on particles re-suspended from the carpet to determine the fraction contributing to indoor air PM.

A previous collaboration between the NERL, Region 10, and the Shoshone-Bannock Tribes identified the major sources or processes that contributed to exceedances of the NAAQS for 24-h averaged PM10 mass recorded at sampling sites located directly downwind of an elemental phosphorous plant on the Fort Hall Indian Reservation (near Pocatello, Idaho). Follow-on work with the Tribe and the Region completed to identify any residual contamination from the now shut-down phosphorous plant.

Relevance :Work conducted under this task will provide measurements of particulate matter (PM) by species and size, thereby contributing to the identification of sources of PM and enhancing modeling efforts. These data will be used to link PM sources with exposures, and will guide compliance with the National Ambient Air Quality Standard (NAAQS) for PM.

Clients :OAR (OAQPS); ORD - NERL, NRMRL, NHSRC, NHEERL, EPA Regional Offices (e.g., EPA Region 10); State, Local, and Tribal Air Pollution Organizations

Project IDs:

ID Code :6940

Project type :OMIS