HR: 17:15h
AN: A34B-06    [Abstracts]
TI: Electron Tomography of Soot Aggregates: Quantitative Measurements of Individual Atmospheric Particles
AU: * van Poppel, L H
EM: Laura.vanpoppel@asu.edu
AF: Arizona State University, Dept. of Geological Sciences Box 871404, Tempe, AZ 85287-1404 United States
AU: Friedrich, H
EM: heiner.friedrich@asu.edu
AF: Arizona State University, Dept. of Geological Sciences Box 871404, Tempe, AZ 85287-1404 United States
AU: Spinsby, J
EM: jacob.spinsby@asu.edu
AF: Arizona State University, Dept. of Geological Sciences Box 871404, Tempe, AZ 85287-1404 United States
AU: Buseck, P R
EM: pbuseck@asu.edu
AF: Arizona State University, Dept. of Geological Sciences Box 871404, Tempe, AZ 85287-1404 United States
AB: Soot (also called black carbon) is a widespread type of aerosol particle that contributes to uncertainties in estimates of climate forcing. It typically occurs in complex clusters having highly variable physical properties, compositions, and surface coatings, and thus presents significant challenges for assessing the optical parameters used in modeling. Morphological variations arise from differences in fuel sources, combustion conditions, and atmospheric aging. Transmission electron microscopy (TEM) images have been widely used for recording the 2D shapes of soot clusters, and these have commonly been interpreted through fractal analysis. Fractal dimensions, D${f}$ are generally inferred from the analysis of 2D TEM images, although problems arise because of finite size effects, primary particle overlap, screening effects, and cluster anisotropy. Electron tomography (ET) is the first experimental approach that provides direct 3D information about soot aggregates. Soot surface character, porosity, and morphology can now all be determined quantitatively. Also, ET creates a 3D intensity map of the object, from which quantitative volume and surface areas can be derived. Using ET, we analyzed soot aggregates from diesel exhaust and a biomass-burning plume. Through comparisons of surface area, volume, and D${f}$ measurements derived from the tomograms, we describe differences in morphology between these two types of soot.
DE: 4801 Aerosols (0305)
DE: 0305 Aerosols and particles (0345, 4801)
DE: 0345 Pollution--urban and regional (0305)
DE: 0394 Instruments and techniques
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting