Direct In Situ Mass Specific Absorption Spectra of Biomass Burning Particles Generated from Smoldering Hard and Softwoods

Abstract

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 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) × 10 m g spanning from 83 femtograms (fg) to 517 fg (500 nm ≤ mobility diameter ≤950 nm), MAC values in parentheses are the 16 and 84 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 × 10 m g to 7.9 × 10 m g 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.

Laboratory studies of fresh and aged biomass burning aerosols emitted from east African biomass fuels – Part 1 – Optical properties

“…S1, aerosol emitted where the aerosol is dominated by organic carbon (Christian et al, 2003;Ward et al, 1992). This is consistent with the finding that low temperature biomass burning results in the formation of primary BrC (Bahadur et al, Radney et al, 2017). Like combustion at 800 o C, the SSA depends on fuel type, which might be due to the 400 difference in the chemical compositions of the emitted aerosol.…”

NIST interlaboratory study of aerosol absorption measurements using photoacoustic spectroscopy

“…Absorption coefficients, αAbs, measured by the spectrometer are the quotient of the particle absorption cross-section (CAbs) and the particle number density (P), or CAbs = αAbs/P; P can be measured using a condensation particle counter (CPC) or other comparable technique. Aerosol CAbs are reported in units of m 2 and most often as function of particle size (or mobility diameter, Dm). Recent developments in the field of mass-based aerosol metrology have enabled particle selection and reporting as a function of particle mass (mp) for aerosol that has also been Dm selected [2,3].…”

“…Aerosol CAbs are reported in units of m 2 and most often as function of particle size (or mobility diameter, Dm). Recent developments in the field of mass-based aerosol metrology have enabled particle selection and reporting as a function of particle mass (mp) for aerosol that has also been Dm selected [2,3].…”

Amplification of black carbon light absorption induced by atmospheric aging: temporal variation at seasonal and diel scales in urban Guangzhou

“…One way is to adopt empirical MAEp in the literature (Cui et al, 2016a). Since the real-world MAEp could be highly diverse by different sources and varies temporally and spatially (Roden et al, 2006;Adler et al, 2010;Shen et al, 2013;McMeeking et al, 2014;Healy et al, 2015;Cheng et al, 2016;Weyant et al, 125 2016; Dastanpour et al, 2017;Radney et al, 2017;Conrad and Johnson, 2019), empirical MAEp at one site might not be applicable at other sites.…”