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Extramural Research

Grantee Research Project Results

NCER Grantee Research Project Results

Passive Aerosol Sampler To Estimate Long-Term Average Concentrations and Size Distributions

EPA Grant Number: U915321
Title: Passive Aerosol Sampler To Estimate Long-Term Average Concentrations and Size Distributions
Investigators: Wagner, Jeffrey R.
Institution: University of North Carolina at Chapel Hill
EPA Project Officer: Jones, Brandon
Project Period: June 1, 1998 through May 1, 2000
Project Amount: $50,059
RFA: STAR Graduate Fellowships (1998)
Research Category: Fellowship - Environmental Engineering , Engineering and Environmental Chemistry , Academic Fellowships

Description:

Objective:

The objective of this research project is to develop a miniature, passive aerosol sampler to estimate long-term average concentrations and size distributions. The passive sampler will monitor indoor or outdoor aerosols over a period of weeks, and will have potential utility as a personal sampler.

Approach:

Particles collect by gravity, convective diffusion, and inertia in a small cavity of the passive sampler. Scanning electron microscopy and automated image analysis are used to count and size collected particles with dp > 0.1 µm. Alternatively, more advanced techniques can be used for ambient-pressure analysis or elemental characterization. The measured particle flux and a particle size-dependent deposition velocity model are used to calculate the average concentration and size distribution over the sampling period. To determine the empirical portion of the deposition velocity model and test sampler precision, a special wind tunnel was developed. The small-scale tunnel incorporates a nonvolatile, polydisperse, high-output aerosol generator. An eight-stage impactor is connected to the tunnel with an isoaxial, isokinetic probe, and is equipped with oleic acid-saturated, polycarbonate-membrane substrates to minimize particle bounce. The empirical factor was determined as a function of particle size by minimizing error with respect to impactor mass and size measurements. Precision and accuracy were assessed as a function of wind speed, relative humidity, and aerosol concentration level. In addition, the precision and accuracy of the passive sampler will be tested in field studies under more realistic, fluctuating conditions.

Supplemental Keywords:

fellowship, aerosols, sampling techniques, microscopy, deposition models, exposure assessment, wind tunnel, impactor, particle size, aerosol sampler, personal sampler., RFA, Scientific Discipline, Air, Ecosystem Protection/Environmental Exposure & Risk, Environmental Chemistry, Air Pollutants, Monitoring/Modeling, Environmental Monitoring, Ecology and Ecosystems, Environmental Engineering, monitoring, atmospheric dispersion models, environmental measurement, long term average concentration, indoor air, outdoor air sampling, aerosol analyzers, aerosols

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The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.

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