A13B-0324
Ice nucleating particles from biomass combustion: emission rates and the role of refractory black carbon
Monday, 14 December 2015
Poster Hall (Moscone South)
Ezra JT Levin1, Gavin R McMeeking2, Christina S. McCluskey3, Christian M Carrico4, Shunsuke Nakao5, Chelsea Stockwell6, Robert J Yokelson6, Ryan C Sullivan7, Paul J DeMott3 and Sonia M Kreidenweis3, (1)Colorado State University, Department of Atmospheric Science, Fort Collins, CO, United States, (2)Handix Scientific, Boulder, CO, United States, (3)Colorado State University, Fort Collins, CO, United States, (4)New Mexico Institute of Mining and Technology, Socorro, NM, United States, (5)Clarkson University, Potsdam, NY, United States, (6)University of Montana, Missoula, MT, United States, (7)Carnegie Mellon University, Pittsburgh, PA, United States
Abstract:
Ice nucleating particles (INPs) allow initial ice crystal formation in clouds at temperatures warmer than about -36 °C and are thus important for cloud and precipitation development. One potential source of INPs to the atmosphere is biomass combustion, such as wildfires, prescribed burning and agricultural burning, which emits large quantities of particulate matter into the atmosphere and is a major source of black carbon (BC) aerosol. To better understand and constrain INP emissions from biomass combustion, globally relevant fuels were used in a series of burns during a study called FLAME 4 at the USFS Fire Sciences Laboratory in Missoula, MT. Concentrations of immersion mode INPs were measured using a Colorado State University Continuous Flow Diffusion Chamber (CFDC). During the first part of the study, emissions were measured in real time as fires progressed from ignition to flaming and smoldering phases. INP emissions were observed predominately during periods of intensely flaming combustion. Roughly 75% of measured burns produced detectable INP concentrations and these had, on average, higher combustion efficiencies and higher BC emissions. During the second half of FLAME 4, we directly measured the contribution of refractory black carbon (rBC) to INP concentrations by selectively removing these particles via laser-induced incandescence (LII) using a Single Particle Soot Photometer (SP2; Droplet Measurement Technologies). The SP2 uses a 1064 nm Na:YAG laser to heat rBC aerosol to their vaporization temperatures, thus removing them from the sampled aerosol. By passing combustion aerosol through the SP2 with the laser on and off while measuring the remaining aerosol with the CFDC, we were able to determine the contribution of rBC to the INP population. Reductions in INPs of 0 – 70% were observed when removing rBC from the combustion aerosol, indicating the importance of rBC particles to INP concentrations for some burn scenarios.
