AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, USA
Abstract View
Ice Nucleating Particle Emissions from Biomass Combustion and the Potential Importance of Soot Aerosol
EZRA LEVIN, Gavin McMeeking, Paul DeMott, Christina S. McCluskey, Christian Carrico, Shunsuke Nakao, Chelsea Stockwell, Robert J. Yokelson, Sonia Kreidenweis, Colorado State University
Abstract Number: 226 Working Group: Biomass Burning Aerosol: From Emissions to Impacts
Abstract Ice nucleating particles (INP) are required for ice crystal formation at temperatures warmer than -36 ºC and thus play a crucial role in cloud and precipitation formation. Soot, or black carbon (BC), is a potential INP, although laboratory and field studies suggest highly varied and sometimes little efficacy of different BC sources. Biomass burning has been found to be a source of INP in previous studies, and is also a major contributor to atmospheric BC concentrations. This study focuses on isolating the BC contribution to INP from biomass combustion sources. Measurements of the emissions from a number of globally relevant biomass fuels were made during the fourth Fire Lab at Missoula Experiment (FLAME 4). Concentrations of INP active in the immersion-freezing mode were measured using a Colorado State University Continuous Flow Diffusion Chamber (CFDC). For a subset of the burns, the contribution of refractory black carbon (rBC) to INP concentrations was determined through the use of laser induced incandescence (LII) for removing rBC particles. For these experiments, the sample was passed through an LII device, the Single Particle Soot Photometer (SP2; Droplet Measurement Technologies) placed in series ahead of the CFDC. By alternating the SP2 laser power on and off, the contribution of rBC to INP concentrations was determined. Over all, combustion emissions from 13 of 22 different biomass fuel types produced measurable INP concentrations for at least one burn. On average, all burns which produced measureable INP had higher combustion efficiency, which is associated with higher BC emissions, than those that did not produce measureable INP. Reductions in INP of 0 – 70% were observed when the SP2 laser was turned on, indicating the important contribution of rBC particles to INP concentrations for some burns.