Multiwavelength Photoacoustic Measurements of Light Absorption and Scattering by Wood Smoke More Spe

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Multiwavelength Photoacoustic Measurements of
Light Absorption and Scattering by Wood
SmokeMore Specific TitleEvidence for light
absorption by organic carbon species in
woodsmoke.Kristin Lewis, William P. Arnott, and
Stephanie WinterUniversity of Nevada Reno
Physics Department Hans Moosmuller and the
Desert Research Institute Reno Nevada USA
Claudio Mazzoleni Los Alamos National
Laboratory Los Alamos NM USA
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People and Instruments
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Missoula Wood Smoke Optics and Chemistry
Experiment

• Optical, chemical, and microphysical properties
  of varied wood smoke aerosols were measured at
  the Missoula Fire Sciences Laboratory June 2006.
  
• For each of the 16 fuel types, 200 grams of fuel
  were ignited. The smoke was contained in a burn
  chamber and sampled for two hours.

• Photoacoustic instruments at1047 nm870 nm780
  nm532 nm405 nm
• 7 wavelength Aethalometer
• Aerodyne Mass Spec
• TDMA, CCN, SEM, CRD, Mercury, NO2, Ozone, TSI 3
  lamba Neph, Radiance Nephs, Scattering
  hygroscopicity, TEOM, EC/OC, and more

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Photoacoustic Instrument Schematic First
Measurements with a Multi-Wavelength
Photoacoustic Instrument for Aerosol Light
Scattering And Absorption
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Angström Coefficients and Single Scattering Albedo
Measurements at 2 wavelengths are used to obtain
a, b, c, and d Angström coefficients for
absorption and scattering. The typical assumption
for absorption is d 1 for elemental
carbon. Single scattering albedo is obtained at
each wavelength.
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Absorption by Wood Smoke

• For certain fuel types burned aerosol light
  absorption did not display the 1/? dependence on
  incident wavelength that is characteristic of
  small elemental carbon aerosol.
• Absorption can be far more efficient at the
  near-UV wavelength than in the near-infrared.

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Conclusion

• Non-elemental-carbon components, such as organic
  species, exist on smoke aerosol of certain fuel
  types and preferentially absorb light at shorter
  wavelengths. In addition to particle size,
  differences in refractive index at widely
  differing wavelengths contribute to spectral
  properties of the aerosol.
• Casual use of the inverse wavelength dependence
  of aerosol light absorption in remote sensing
  retrievals with sun photometers and satellite
  data can bring errors of a factor of 6 in the UV
  and a factor of 2 in the visible when compared
  with near IR absorption for certain types of wood
  smoke.

ACKNOWLEDGEMENTS DOE ASP Program and the
National Parks Service, field work. NSF MRI
program for instrument development. All
participants in the Missoula Fire Experiment.