Evaluation of the Transport and Deposition of Fugitive Dust Using Lidar
Document ID: 159
Fitz, Dennis1
Pankratz, David1
Philbrick, C. Russell2
Li, Guangkun2
1 University of California, Riverside, College of Engineering, Center for Environmental Research and Technology, Riverside, CA, U.S.A.
2 The Pennsylvania State University, Department of Electrical Engineering, University Park, PA, U.S.A.
Presented: U.S. Environmental Protection Agency's 11th Annual Emission Inventory Conference
Atlanta, Georgia, April 16-18, 2002
Abstract
Ambient measurements suggest that source inventories of PM10 from geologic sources are overestimated by 50 percent or more. This discrepancy may be due to inaccurate emission calculations and/or due to the rapid deposition of PM10 after entrainment into the atmosphere. Tests were conducted during December 2000 and December 2001 using a two-wavelength scanning backscatter lidar to investigate PM10 deposition rates from artificially generated fugitive dust. Dust was generated by vehicles on unpaved roads and with a blower dispersing known amounts of finely ground calcium carbonate (paint pigment) or native soil. The size and concentration of the resulting dust plumes were monitored for up to a half-hour and a distance of several kilometers. The changes in these dust plumes’ characteristics with time, including particle size and density, were estimated from the relationship between backscatter and extinction for the two wavelengths used. The lidar was calibrated using dust of known size distribution and concentration generated in a contained volume during a set of tests conducted in December 2001. An approximation of the backscatter and extinction signals has been obtained using model calculations that are based upon Mie theory for spherical particles. These models show that the backscatter signal does not depend strongly on the particle density but does depend strongly upon size and wavelength of the scattering radiation. However, the extinction depends strongly on the concentration and size of the scattering particles but not on the wavelength. Therefore, simultaneous measurements of the backscatter and extinction at two different wavelengths should permit analysis to reveal the approximate settling rates for the various types (i.e., sources) of fugitive dust.