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Impacts of nonrefractory material on light absorption by aerosols emitted from biomass burning
Author(s) -
McMeeking G. R.,
Fortner E.,
Onasch T. B.,
Taylor J. W.,
Flynn M.,
Coe H.,
Kreidenweis S. M.
Publication year - 2014
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1002/2014jd021750
Subject(s) - aerosol , soot , absorption (acoustics) , single scattering albedo , absorption cross section , wavelength , analytical chemistry (journal) , particle (ecology) , chemistry , materials science , optics , optoelectronics , combustion , cross section (physics) , environmental chemistry , physics , oceanography , organic chemistry , quantum mechanics , composite material , geology
We present laboratory measurements of biomass‐burning aerosol light‐scattering and light absorption coefficients at 405, 532, and 781 nm and investigate their relationship with aerosol composition and fuel type. Aerosol composition measurements included nonrefractory components measured by a high‐resolution aerosol mass spectrometer (AMS), composition of refractory black carbon‐containing particles by a soot particle aerosol mass spectrometer (SP‐AMS), and refractory black carbon measured by a single‐particle soot photometer (SP2). All measurements were performed downstream of a thermal denuder system to probe the effects of nonrefractory material on observed optical properties. The fires studied emitted aerosol with a wide range of optical properties with some producing more strongly light‐absorbing particles (single‐scattering albedo or SSA at 781 nm = 0.4) with a weak wavelength dependence of absorption (absorption Ångström exponent or AAE = 1–2) and others producing weakly light‐absorbing particles (SSA at 781 nm ~1) with strong wavelength dependence of absorption (AAE ~7). Removal of nonrefractory material from the particles by the thermal denuder system led to substantial (20–80%) decreases in light absorption coefficients, particularly at shorter wavelengths, reflecting the removal of light‐absorbing material that had enhanced black carbon absorption in internally mixed untreated samples. Observed enhancements of absorption by all mechanisms were at least factors of 1.2–1.5 at 532 nm and 781 nm as determined from the heated samples. A mass absorption cross‐section‐based approach indicated larger enhancements, particularly at shorter wavelengths.