AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
Abstract View
Measured Direct In-situ Mass Specific Absorption Spectra from Nine Forms of Carbonaceous Aerosol
CHRISTOPHER ZANGMEISTER, Rian You, James Radney, Michael Zachariah, National Institute of Standards and Technology
Abstract Number: 295 Working Group: Carbonaceous Aerosols in the Atmosphere
Abstract This study will focus on quantitative measurements of black carbon (BC) across a wide spectral range to better understand the range of mass specific absorption cross sections (MAC) values of BC. In 2006 Bond and Bergstrom first assessed BC MAC as 7.5 m2 g-1 at a single wavelength (550 nm). This value is typically used in determination of the impact of BC climate forcing. Recent technical advances have allowed the MAC of BC to be re-assessed using new quantitative methods based on direct in-situ spectroscopic measurements across a broad wavelength range.
Mass specific absorption spectra were measured between λ = 500 nm and 840 nm for nine forms of carbonaceous aerosol, some of which meet the definition of BC: five samples generated from flames, fullerene soot, graphene, reduced graphene oxide (rGO), and C60. Data were reported as mass specific absorption cross sections (MAC) for each sample. Particles generated from flames had morphologies consistent with black carbon (BC) and measured MAC between 3.8 m2 g-1 and 8.6 m2 g-1 at λ = 550 nm. MAC spectra were dependent on fuel type and formation conditions across the measured spectral window. Wavelength dependencies were determined using the absorption Angstrom exponent (AAE) and ranged between 0.5 and 1.3 for most samples; the AAE of C60 was 7.5 ± 0.9. The results illustrate that accurate quantification of carbonaceous aerosol absorption requires detailed measurements of aerosols with known mass across a broad spectral window.