AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Absorption Enhancement of Cook Stove Soot Coated with SOA: Measurements and Modeling
GEORGES SALIBA, Adam Ahern, Antonios Tasoglou, Rawad Saleh, Eric Lipsky, Ryan Sullivan, Janarjan Bhandari, Claudio Mazzoleni, Allen Robinson, R. Subramanian, Carnegie Mellon University
Abstract Number: 251 Working Group: Carbonaceous Aerosols in the Atmosphere
Abstract Direct radiative forcing by black carbon (BC)-containing aerosols (BCA) is affected by the relative fraction of non-BC material and the morphology of individual particles – collectively referred to as “mixing state”. Uncertainties in absorption properties of atmospherically aged BC particles, due to their mixing state, complicates its quantitative assessment. Some studies show absorption enhancement of coated BC while others suggest a lack of enhancement in ambient aerosols. We conducted BC coating experiments, in a smog chamber, using cook-stove soot coated with secondary organic aerosol from the ozonolysis of alpha-Pinene or from oxidation of primary vapors. Emissions from a range of cook-stoves and fuels were used during the study. A suite of instruments measuring aerosol absorption, size distribution, mass, and black carbon concentrations, were used to characterize fresh and aged cook-stove emissions. TEM/SEM images were collected to explore morphology changes before and after aging of BC fractals. We report a mass absorption cross section (MAC) of fresh cook-stove emissions of 10.14 m$^2.g$^-1 (±1.43) at 405 nm. Rayleigh-Debye-Gans (RDG) calculations (monomer size of 33.2 ± 5.4 nm) reproduced the measured absorption enhancement. However, Mie theory over-predicted absorption enhancement for non-BC to BC ratios less than 10. Mie theory reproduced the data at higher ratios, suggesting substantial collapse of BC particles with heavy coatings.