AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, USA
Abstract View
Hygroscopicity and Cloud Condensation Nucleation Activity of Fresh Biomass Burning Aerosol: Black Carbon Mixing States
SHUNSUKE NAKAO, Ezra Levin, Gavin McMeeking, Christian Carrico, Thilina Jayarathne, Elizabeth Stone, Sonia Kreidenweis, Colorado State University
Abstract Number: 387 Working Group: Biomass Burning Aerosol: From Emissions to Impacts
Abstract Biomass burning is an important source of atmospheric black carbon (BC). The atmospheric lifetime of BC depends on its ability to act as cloud condensation nuclei (CCN), which is governed by the hygroscopic coatings and particle size. Due to the strong dependence of CCN activities on biomass fuel types, it is essential to investigate the wide range of fuel types in well-controlled systems. During the fourth Fire Laboratory at Missoula Experiments (FLAME 4) study, we examined the single hygroscopicity parameter kappa of biomass burning aerosol emitted by the open combustion of 17 different biomass fuels. In addition to the conventional hygroscopic growth measurements and size-resolved CCN measurements, we determined the hygroscopicity of particles with and without BC-core individually by applying the recently developed combination of the Hygroscopicity Tandem Differential Mobility Analyzer – Single Particle Soot Photometer (HTDMA-SP2) (McMeeking et al., ACP, 2011), in which particles were first separated by the HTDMA based on the hygroscopicity and then the hygroscopic growth factors of particles with and without the refractory BC component were determined based on laser induced incandescence and light scattering. Kappa varied from 0.02 (weakly hygroscopic) to 0.6 (highly hygroscopic) depending of biomass fuel types, in agreement with previous studies. Kappa acquired by the HTDMA and the size-resolved CCN measurement agreed reasonably. HTDMA-SP2 measurements suggested varied extents of particle heterogeneity; overall, most BC-containing particles were inferred to be thickly coated with organics and inorganics, based on the similar kappa values of BC-containing particles and non BC-containing particles. This study suggests that the majority of BC particles emitted during the biomass burning experiments of this study was CCN active at the point of emission.