Particles from smoldering biomass burning (BB) represent a major source of carbonaceous aerosol in the terrestrial atmosphere. In this study, mass specific absorption spectra of laboratory- generated smoldering wood particles (SWP) from 3 hardwood and 3 softwood species were measured in-situ. Absorption data spanning from λ = 500 nm to 840 nm were collected using a photoacoustic spectrometer coupled to a supercontinuum laser with a tunable wavelength and bandwidth filter. SWP were size- (electrical mobility) and mass-selected prior to optical characterization allowing data to be reported as mass-specific absorption cross sections (MAC). The median measured MAC at λ = 660 nm for smoldering oak particles was 1.1 (0.57/1.8) x 10-2 m2 g-1 spanning from 83 femtograms (fg) to 517 fg (500 nm ≤ mobility diameter ≤ 950 nm), MAC values in parenthesis are the 16th and 84th percentiles of the measured data (i.e. 1σ). The collection of all six wood species (Oak, Hickory, Mesquite, Western redcedar, Baldcypress and Blue spruce) had median MAC values ranging from 1.4 x 10-2 m2 g-1 to 7.9 x 10-2 m2 g-1 at λ = 550 nm with absorption Ångström exponents (AAE) between 3.5 and 6.2. Oak, Western redcedar and Blue spruce possessed statistically similar (p > 0.05) spectra while the spectra of Hickory, Mesquite and Baldcypress were distinct (p < 0.01) as calculated from a point-by-point analysis using the Wilcox rank-sum test.
Citation: Environmental Science & Technology
Pub Type: Journals
Aerosol, spectroscopy, biomass burning, photoacoustic