10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
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Modelling Biomass Burning Plumes: The Impacts of Dilution, Chemistry, and Coagulation on the Size Distribution and Resulting Direct and Indirect Effects
ANNA HODSHIRE, Qijing Bian, Shantanu Jathar, Sonia Kreidenweis, Jeffrey R. Pierce, Colorado State University
Abstract Number: 100 Working Group: Aerosol Transport and Transformation
Abstract Biomass burning is an important source of carbonaceous species to the atmosphere, with significant implications for air quality, climate, and human health. The direct and indirect radiative impacts of these particles depend on the size, composition, and amount of these particles in the atmosphere; hence, we need to understand biomass burning particle evolution in the atmosphere. Fires emit both primary organic aerosol (POA) and organic vapors of varying volatility that depend on the fuel and burning conditions. These particles and vapors evolve in the atmosphere due to chemistry and dilution. Many of the emitted vapors can undergo oxidation to become lower-volatility products that can then contribute to SOA production; some of the POA may be semivolatile and evaporate upon dilution; and some of the POA evaporation products may then oxidize to form lower-volatility products that can again participate in SOA production. The net production/loss of biomass burning organic aerosol depends both on chemistry and dilution in the plumes (Bian et al., 2017). Further, particles in the plume undergo coagulation, which reduces particle number and shifts the size distribution towards larger sizes. Coagulation, evaporation, and SOA production each depend, in part, on fire size and ambient conditions such as the atmospheric stability conditions (Bian et al., 2017; Sakamoto et al., 2016).
In this study, we use an expanding Lagrangian box model to simulate biomass burning plumes as they disperse and chemically and physically evolve. We simulate small to large fire sizes with areas between 1×10-4 and 1×102 km2, different stability conditions, and different background aerosol concentrations. For each fire/meteorological/background case, we perform sensitivity tests of each available combination between coagulation on/off and chemistry on/off to determine the role of coagulation, chemistry, and dilution on the evolution of the aerosol size distribution in biomass burning plumes. Finally, we calculate the efficiencies of the particles in each case to impact aerosol direct and indirect effects and determine the role of coagulation, chemistry, and dilution on direct and indirect effects.
Bian, Q., Jathar, S. H., Kodros, J. K., Barsanti, K. C., Hatch, L. E., May, A. A., Kreidenweis, S. M., and Pierce, J. R.: Secondary organic aerosol formation in biomass-burning plumes: Theoretical analysis of lab studies and ambient plumes, Atmos. Chem. Phys., 17, 5459-5475, doi:10.5194/acp-2016-949, 2017.
Sakamoto, K. M., Laing, J. R., Stevens, R. G., Jaffe, D. A., and Pierce, J. R.: The evolution of biomass-burning aerosol size distributions due to coagulation: dependence on fire and meteorological details and parameterization, Atmos. Chem. Phys., 16, 7709-7724, doi:10.5194/acp-16-7709-2016, 2016.