Articles | Volume 11, issue 13
Atmos. Chem. Phys., 11, 6445–6463, 2011

Special issue: POLARCAT (Polar Study using Aircraft, Remote Sensing, Surface...

Atmos. Chem. Phys., 11, 6445–6463, 2011

Research article 07 Jul 2011

Research article | 07 Jul 2011

Boreal forest fire emissions in fresh Canadian smoke plumes: C1-C10 volatile organic compounds (VOCs), CO2, CO, NO2, NO, HCN and CH3CN

I. J. Simpson1, S. K. Akagi2, B. Barletta1, N. J. Blake1, Y. Choi3, G. S. Diskin3, A. Fried4, H. E. Fuelberg5, S. Meinardi1, F. S. Rowland1, S. A. Vay3, A. J. Weinheimer4, P. O. Wennberg6, P. Wiebring4, A. Wisthaler7, M. Yang3,1, R. J. Yokelson2, and D. R. Blake1 I. J. Simpson et al.
  • 1Department of Chemistry, University of California-Irvine, Irvine, CA 92697, USA
  • 2Department of Chemistry, University of Montana, Missoula, MT 59812, USA
  • 3NASA Langley Research Center, Hampton, VA 23681, USA
  • 4National Center for Atmospheric Research, 1850 Table Mesa Dr., Boulder, CO 80305, USA
  • 5Department of Meteorology, Florida State University, Tallahassee, FL 32306, USA
  • 6Division of Engineering and Applied Science and Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA
  • 7Institute of Ion Physics and Applied Physics, University of Innsbruck, Innsbruck, Austria

Abstract. Boreal regions comprise about 17 % of the global land area, and they both affect and are influenced by climate change. To better understand boreal forest fire emissions and plume evolution, 947 whole air samples were collected aboard the NASA DC-8 research aircraft in summer 2008 as part of the ARCTAS-B field mission, and analyzed for 79 non-methane volatile organic compounds (NMVOCs) using gas chromatography. Together with simultaneous measurements of CO2, CO, CH4, CH2O, NO2, NO, HCN and CH3CN, these measurements represent the most comprehensive assessment of trace gas emissions from boreal forest fires to date. Based on 105 air samples collected in fresh Canadian smoke plumes, 57 of the 80 measured NMVOCs (including CH2O) were emitted from the fires, including 45 species that were quantified from boreal forest fires for the first time. After CO2, CO and CH4, the largest emission factors (EFs) for individual species were formaldehyde (2.1 ± 0.2 g kg−1), followed by methanol, NO2, HCN, ethene, α-pinene, β-pinene, ethane, benzene, propene, acetone and CH3CN. Globally, we estimate that boreal forest fires release 2.4 ± 0.6 Tg C yr−1 in the form of NMVOCs, with approximately 41 % of the carbon released as C1-C2 NMVOCs and 21 % as pinenes. These are the first reported field measurements of monoterpene emissions from boreal forest fires, and we speculate that the pinenes, which are relatively heavy molecules, were detected in the fire plumes as the result of distillation of stored terpenes as the vegetation is heated. Their inclusion in smoke chemistry models is expected to improve model predictions of secondary organic aerosol (SOA) formation. The fire-averaged EF of dichloromethane or CH2Cl2, (6.9 ± 8.6) × 10−4 g kg−1, was not significantly different from zero and supports recent findings that its global biomass burning source appears to have been overestimated. Similarly, we found no evidence for emissions of chloroform (CHCl3) or methyl chloroform (CH3CCl3) from boreal forest fires. The speciated hydrocarbon measurements presented here show the importance of carbon released by short-chain NMVOCs, the strong contribution of pinene emissions from boreal forest fires, and the wide range of compound classes in the most abundantly emitted NMVOCs, all of which can be used to improve biomass burning inventories in local/global models and reduce uncertainties in model estimates of trace gas emissions and their impact on the atmosphere.

Final-revised paper