HR: 17:45h
AN: A24B-08    [Abstracts]
TI: Experimental validation of light scattering and absorption theories of fractal-like carbonaceous aerosol agglomerates
AU: * Chakrabarty, R
EM: rajan@dri.edu
AF: Chemical Physics Program, University of Nevada Reno, Reno, NV 89557, United States
AU: * Chakrabarty, R
EM: rajan@dri.edu
AF: Desert Research Institute, 2215 Raggio Parkway, Reno, NV 89512, United States
AU: Moosmuller, H
EM: hansm@dri.edu
AF: Desert Research Institute, 2215 Raggio Parkway, Reno, NV 89512, United States
AU: Arnott, W P
EM: patarnott@physics.unr.edu
AF: Department of Physics, University of Nevada Reno, Reno, NV 89557, United States
AU: Garro, M
EM: garro@fas.harvard.edu
AF: Harvard University, Division of Engineering and Applied Sciences, Cambridge, MA 02138, United States
AU: Slowik, J
EM: jslowik@chem.utoronto.ca
AF: University of Toronto, Department of Chemistry, Ontario, ON M5S3H6, Canada
AU: Cross, E
EM: crosse@bc.edu
AF: Boston College, Department of Chemistry, Boston, MA 02467, United States
AU: Han, J
EM: jhan0110@gmail.com
AF: Boston College, Department of Chemistry, Boston, MA 02467, United States
AU: Davidovits, P
EM: paul.davidovits@bc.edu
AF: Boston College, Department of Chemistry, Boston, MA 02467, United States
AU: Onasch, T
EM: onasch@aerodyne.com
AF: Aerodyne Research Inc., Billerica, Billerica, MA 01821, United States
AU: Worsnop, D
EM: worsnop@aerodyne.com
AF: Aerodyne Research Inc., Billerica, Billerica, MA 01821, United States
AB: The optical coefficients of size-selected carbonaceous aerosol agglomerates measured at a wavelength of 870 nm are compared with those predicted by three theories, namely Rayleigh-Debye-Gans (RDG) approximation, volume-equivalent Mie theory, and integral equation formulation for scattering (IEFS). Carbonaceous agglomerates, produced via flame synthesis, were size-selected using two differential mobility analyzers (DMAs) in series, and their scattering and absorption coefficients were measured with nephelometry and photoacoustic spectroscopy. Scanning electron microscopy, along with image processing techniques, were used for the parameterization of the structural properties of the fractal-like agglomerates. The agglomerate structural parameters were used to evaluate the predictions of the optical coefficients based on the three light scattering and absorption theories. The results indicate that the RDG approximation agrees within 10% of the experimental results and the exact electromagnetic calculations of the IEFS theory. The experimental scattering coefficient is over predicted by the volume-equivalent Mie theory by a factor of ~3.2. Also, the RDG approximation-predicted optical coefficients showed pronounced sensitivity to changes in monomer mean diameter, the count median diameter of the agglomerates, and the geometric standard deviation of the agglomerate number size distribution.
DE: 0345 Pollution: urban and regional (0305, 0478, 4251)
DE: 0649 Optics (4264)
DE: 4801 Aerosols (0305, 4906)
DE: 4906 Aerosols (0305, 4801)
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting