AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
Abstract View
The Influence of Calibration Standards on the Measurement of the Mass Absorption Coefficient of Black Carbon
ELIZABETH WIGGINS, Richard Moore, Luke Ziemba, Gregory Schuster, NASA
Abstract Number: 455 Working Group: Carbonaceous Aerosol
Abstract Black carbon aerosol (BC) emitted from fossil fuel combustion and biomass burning absorbs incoming solar radiation and influences the physical and chemical properties of the atmosphere. The climate forcing of BC is a highly uncertain and critical parameter in the radiation balance of the planet. Light absorption by BC per mass, the mass absorption coefficient (MAC), is a value widely used by the scientific community to quantify the influence of BC light absorption on the atmosphere and climate. Considerable disagreement exists between past and present laboratory and field-based measurements of the MAC of uncoated BC particles. These disagreements could be an artifact of changing instrumental calibration standards or measurement techniques. For example, a single particle soot photometer (SP2) is often used to measure BC mass through laser induced incandescence. However, the SP2 has to be calibrated using a BC standard with a known effective density. The community recently shifted from using Aquadag as a calibration standard to using fullerene soot, and there has been a corresponding shift in measurements of BC MACs that rely on SP2 derived mass measurements. In this study we measured the MAC of commonly used calibration standards, including fullerene soot, Aquadag (Classic and Lot 9267), and carbon black (Cab-o-jet 200). Our experimental setup included a centrifugal particle mass analyzer (CPMA) to measure mass, a scanning mobility particle sizer (SMPS) to measure size, a single particle soot photometer (SP2) to determine the relationship between BC incandescence and mass, and a differential photoacoustic absorption spectrometer (DPAS) to measure absorption. The results from this study will improve our understanding of the true MAC of BC and highlight the cause of discrepancies between measurement techniques while offering correction factors for previous studies.