AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
Abstract View
Broadband Measurements of the Mass Absorption Coefficient of Soot
Lindsay Renbaum-Wolff, Al Fischer, Taylor Helgestad, Andrew Lambe, Geoff Smith, Christopher Cappa, Arthur J. Sedlacek, Paul Davidovits, TIMOTHY ONASCH, Andrew Freedman, Aerodyne Research, Inc.
Abstract Number: 582 Working Group: Carbonaceous Aerosols in the Atmosphere
Abstract Emission of soot by combustion systems comprises the primary source of light absorbing carbon-based aerosols, a species which plays an important role in radiative transfer affecting climate change. We present wavelength dependent measurements of the mass absorption coefficient (MAC) of nascent soot produced by a methane diffusion flame at 10 points over a wide spectral range (300-660 nm) in order to determine the validity of the assumption that the Angstrom Absorption Exponent is 1.0. Polydisperse soot particles were generated by an inverted methane diffusion flame. Relatively uniform single mass samples were generated by using a DMA to produce a monodisperse soot distribution and then using a CPMA to select a specific per particle mass. The average mass of that sample was measured using a second CPMA and then corrected for the presence of doubly charged particles the concentration of which was determined using an SP2. The soot absorption was measured using three separate instruments including laser-based photoacoustic absorption monitors, a CAPS PM $_(ssa) monitor, and a photoacoustic monitor employing a lamp as a light source. TEM images and the measured mass/mobility diameter relationship indicated that the soot was fractal (dimension=1.8). The absolute MAC values for the soot at several wavelengths was in excellent agreement with previously reported values. The measured AAE was 1.25 ± 0.24 where the 2-sigma error is determined by the precision of the photoacoustic absorption measurements