Imaging and Classification of Ultrafine Particles in Indoor AirEPA Grant Number: R826688
Title: Imaging and Classification of Ultrafine Particles in Indoor Air
Investigators: Cohen, Beverly S. , Chen, Lung Chi , Li, Wei , Xiong, Judy Q.
Current Investigators: Cohen, Beverly S. , Guo, Hai , Heikkinen, Maire SA , Li, Wei , Xiong, Judy Q.
Institution: New York University
EPA Project Officer: Hunt, Sherri
Project Period: October 1, 1998 through September 30, 2001
Project Amount: $387,384
RFA: Exploratory Research - Human Health (1998) RFA Text | Recipients Lists
Research Category: Health Effects , Human Health , Health
The ultrafine particle fraction of ambient aerosols consisting of particles with diameters <200 nm accounts for more than 90% of the total number concentration. Other than number concentration and size distribution, little is known about the physical-chemical properties of ultrafine aerosol particles. We propose to use Scanning Probe Microscopy (SPM), a new technology that can resolve nanometer scale surface features, to examine and identify common indoor aerosol particles. Ultimately , this will provide a method to differentiate outdoor from indoor exposure, and allow identification and estimation of personal exposure to specific indoor-generated pollutants.
Morphometric methods have been used extensively for counting, studying and classifying micrometer sized particles and it is evident that important information has been revealed by microscopic examination. We expect that a morphometric study with SPM will provide a similar critical understanding for ultrafine particles. SPM is superior to scanning or transmission electron microscopy for studying ambient particles because it is relatively inexpensive, does not require sample treatment, and can be performed at ambient pressure.
Common indoor aerosol particles in ultrafine sizes will be generated and deposited onto test substrates. The samples will be examined with SPM to examine the morphometry of the particles, and whether, as for optically observable particles, these properties can be used as a qualitative classification method. In addition to discrimination by particle morphometry, we plan to test several chemically reactive substrates that may allow us to infer particle surface composition. The initiatory studies proposed here focus on well identified specific indoor particles rather than outdoor contaminants in order to explore the best use of this new technology.
Because the mass concentration of ultrafine particles is extremely low, it is difficult to collect enough mass to analyze them by current methods. If the particles can be classified by morphometric properties, this problem can be overcome by combining SPM technology with a low flow diffusion sampler developed in our laboratory for ultrafine ambient acid particles. We will evaluate the applicability of a low flow sampling system and SPM analysis in several representative indoor environments, e.g. a home, an institutional cafeteria, and a secretarial office. The work will provide a foundation for utilization of a low cost monitor to determine the number concentration of indoor and outdoor ultrafine particles.