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INDIVIDUAL PARTICLE ANALYSIS OF INDOOR, OUTDOOR, AND PERSONAL SAMPLES FROM THE 1998 BALTIMORE RETIREMENT HOME STUDY
Citation:
Conner, T L., G A. Norris, M S. Landis, AND R W. Williams. INDIVIDUAL PARTICLE ANALYSIS OF INDOOR, OUTDOOR, AND PERSONAL SAMPLES FROM THE 1998 BALTIMORE RETIREMENT HOME STUDY. Presented at PM 2000 AWMA Conference, Charleston, SC, January 24-28, 1999.
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:
Particle sampling was conducted outdoors, indoors, in apartment residences, and on individual residents (i.e., personal samples) at a retirement center in the Towson area of northern Baltimore County. Concurrent particle sampling was conducted at a central community site closer to downtown Baltimore. The major objective o# this work was to use computer-controlled scanning electron microscopy with individual-particle x-ray analysis (CCSEM) to measure the chemical and physical characteristics of particles collected on polycarbonate filters at the indoor, outdoor and community sampling locations. Apartment residence and personal samples collected on Teflon& fiber filters were examined manually. These data and observations will contribute to the understanding of the sources of particulate matter found in various micro-environments.
The PERSONAL SEM? (PSEM) manufactured by R. J. Lee Instruments, Ltd., Trafford, PA, was used to conduct the analyses. The PSEM is capable of computer-controlled analysis of particles with a physical diameter greater than approximately 0.5 Vim, or smaller for particles composed of elements with bright backscattered-electron images (e.g., Pb). Rules were developed to classify particles based on their size, shape (aspect ratio), elemental composition, number of x-ray counts, and/or image brightness level. While the process of generating userdefined rules can be very timeconsuming and is, by nature, subject to human judgement, this approach was used to take advantage of the wealth of information provided by particle images and the unique ability of the human eye to interpret them.
The CCSEM results were consistent with the trajectories of the air masses associated with the samples examined (e.g., increased NaCl with the marine transport regime). Differences in particle number concentrations for certain rule-based particle classes were observed among the community, outdoor and indoor samples. These differences indicate the presence of local outdoor particle sources, as well as particles originating from indoor sources or activities. Qualitative differences among the selected personal and apartment residence samples were also observed. The CCSEM results show that, for the particles characterized by CCSEM, community-based sampling may not yield samples which are representative of the particles found indoors.
This work has been funded wholly or in part by the United States Environmental Protection Agency under contract #68-D5-0040 to the Research Triangle Institute and. under contract #68-D5-0040 to ManTech Environmental Technology, Inc. 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.