Aerosol monitors provide a means to measure airborne particulate matter and droplets, and we have worked with different monitors aimed at measuring fugitive dust and bioaerosol particulate matter for various projects.
Wind-Tunnel Fugitive Dust Analysis with TSI DustTraks
TEOM, MetOne, DustTrak testing in a Wind-Tunnel Dust Chamber
The TSI DustTrak can sample an intake air volume of air and return a concentration value every second. The aerosol monitor uses light scattering technology to determine mass concentration in “real-time”. An aerosol sample is drawn into the sensing chamber in a continuous stream. One section of the aerosol stream is illuminated with a small beam of laser light scattering light in all directions. A lens that is 90 degrees to both the aerosol stream and laser beam collects some of the collected light and focuses it onto a photodetector. The detection circuitry converts the light into a voltage, which is proportional to the amount of light scattered, which in turn is proportional to the mass concentration of the aerosol.
The voltage is read by the processor and multiplied by an internal calibration constant to yield mass concentration, where the calibration constant is determined from the ratio of the voltage response of the DustTrak to the known mass concentration of the test aerosol. This type of monitor responds linearly to the aerosol mass concentration—i.e., two particles scatter twice as much light as one particle, etc. In addition, the DustTrak has specialized orifices to selectively choose the size range of particles reaching the sampler. There are orifices specifying the following size ranges: particles less than 10 microns, particles less than 2.5 microns, and particles less than 1.0 microns.
Dust Emission Rate Set-up
Dust Threshold Set-up
At the University of California at Davis, the Environmental Boundary Layer Wind Tunnel (Saltation Wind Tunnel) was modified to create a dust chamber to do side-by-side comparison of DustTraks, MetOne GT 641, and a Tapered Element Oscillating Microbalance (TEOM). The wind tunnel was used to develop well-mixed dust aerosols from Owens (dry) Lake soils samples that was expelled into the chamber from the diffuser section of the wind tunnel. The TEOM is an EPA accepted PM10 measuring instrument that was used at Owens (dry) Lake to monitor fugitive dust emissions. The research was done in coordination with CH2M HILL and the University of California at Davis.
In collaboration with Phoenix Analysis and Design Technologies (PADT) and the University of Utah, Dr. Roney helped test a prototype bioaerosol monitor for a DOD Small Business Innovative Research (SBIR) Phase I grant. The prototype instrument sampling methodology is proprietary, but a GRIMM analyzer and DustTrak aerosol monitors were used in side-by-side wind-tunnel testing with the prototype at the University of Utah. A test dust was used to verify that the prototype instruments was working as planned and collected at the proper cut-off particulate matter sizes. This research was instrumental in Phoenix Analysis and Design advancing to Phase II of the SBIR program.
Bioaerosol prototype monitor was tested in the University of Utah boundary layer wind tunnel.
University of Utah Boundary Layer Wind Tunnel
At UCCS, Dr. Roney supervised an undergraduate student project called the Atmospheric Particle Sampler (APS) which attempted to make to autonomous samples of upper atmospheric aerosol particles during a weather balloon ascent to 100,000 feet and the subsequent descent. The aerosol particle systems consisted of a programmable pump connected to a Personal Environment Monitor (PEM) which operates on the principal of inertial separation of airborne particles using an impactor. The objective was to attempt to capture meteoric dust and upper atmospheric pollens. A HOBO pressure measuring devices was used to turn on the samplers at the appropriate altitudes.
A second project was aimed at capturing bioaerosols (standard bacteria) in the lower atmosphere with a similar set-up, but with bioaerosol fixtures attached to the programmable pump. The collections were then used to grow cultures in the lab to indicate the existence of bioaerosols. During testing an Aerostat balloon was used to to sample tropospheric aerosols with a TSI SidePak Aerosol monitor while simultaneously measuring with the APS. There was some indication of airborne particles, but the APS did not collect anything that grew a culture.
J.A. Roney, “Wind-Tunnel Physical Modeling and Numerical Simulation of Fugitive Dust Entrainment”, Presentation to the Department of Aerospace Engineering and Engineering Mechanics, Iowa State University, March 21, 2001
J.A. Roney, D. Kim, R.V. Coquilla, and B.R. White, “Simulation and Analysis of Factors Leading to High PM10 Emissions Fluxes at Owens Dry Lake Using an Environmental Boundary Layer Wind Tunnel”, Poster Presentation, AGU Fall Meeting, 1999.
D. Kim, J.A. Roney, R.V. Coquilla, and B.R. White, “Wind Tunnel Methods for Estimating Atmospheric Fugitive Dust Emissions”, Poster Presentation, AGU Fall Meeting, 1999.