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Published December 15, 2011 | Published
Journal Article Open

Flight-based chemical characterization of biomass burning aerosols within two prescribed burn smoke plumes


Biomass burning represents a major global source of aerosols impacting direct radiative forcing and cloud properties. Thus, the goal of a number of current studies involves developing a better understanding of how the chemical composition and mixing state of biomass burning aerosols evolve during atmospheric aging processes. During the Ice in Clouds Experiment-Layer Clouds (ICE-L) in the fall of 2007, smoke plumes from two small Wyoming Bureau of Land Management prescribed burns were measured by on-line aerosol instrumentation aboard a C-130 aircraft, providing a detailed chemical characterization of the particles. After ~2–4 min of aging, submicron smoke particles, produced primarily from sagebrush combustion, consisted predominantly of organics by mass, but were comprised primarily of internal mixtures of organic carbon, elemental carbon, potassium chloride, and potassium sulfate. Significantly, the fresh biomass burning particles contained minor mass fractions of nitrate and sulfate, suggesting that hygroscopic material is incorporated very near or at the point of emission. The mass fractions of ammonium, sulfate, and nitrate increased with aging up to ~81–88 min and resulted in acidic particles. Decreasing black carbon mass concentrations occurred due to dilution of the plume. Increases in the fraction of oxygenated organic carbon and the presence of dicarboxylic acids, in particular, were observed with aging. Cloud condensation nuclei measurements suggested all particles >100 nm were active at 0.5% water supersaturation in the smoke plumes, confirming the relatively high hygroscopicity of the freshly emitted particles. For immersion/condensation freezing, ice nuclei measurements at −32 °C suggested activation of ~0.03–0.07% of the particles with diameters greater than 500 nm.

Additional Information

© 2011 Author(s). This work is distributed under the Creative Commons Attribution 3.0 License. Published by Copernicus Publications on behalf of the European Geosciences Union. Received: 14 April 2011. Published in Atmos. Chem. Phys. Discuss.: 22 June 2011. Revised: 19 November 2011. Accepted: 2 December 2011. Published: 15 December 2011. Jay Esperance, Kristi Bulock, and Aaron Mier at the Wyoming Bureau of Land Management are thanked for prescribed burn ground-based data. NSF and NCAR are acknowledged for financial support of the ICE-L field campaign, as well as the work of T. Campos, D. C. Rogers, and A. J. Heymsfield. K. A. Pratt and K. A. Prather acknowledge NSF for support of ICE-L (ATM-0650659), A-ATOFMS development (ATM-0321362), and a graduate research fellowship for K. A. Pratt.S. M. Murphy and J. H. Seinfeld acknowledge NSF for support of ICE-L (ATM-0340832) and NASA for an Earth and Space Sciences Fellowship for S. M. Murphy. R. Subramanian and G. L. Kok acknowledge NSF for ICE-L support (ATM-0631919). P. J. DeMott and A. J. Prenni acknowledge support from NSF (ATM-0611936). K. A. Pratt and S. M. Murphy also acknowledge a NOAA Climate & Global Change Postdoctoral Fellowship and a National Research Council Postdoctoral Fellowship, respectively. Daniel Cziczo (Pacific Northwest National Laboratory) is thanked for discussions. Edited by: O. Möhler.

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