Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 9 1 2009 10.5194/acpd-9-767-2009 http://www.atmos-chem-phys-discuss.net/9/767/2009/ http://www.atmos-chem-phys-discuss.net/9/767/2009/acpd-9-767-2009.html http://www.atmos-chem-phys-discuss.net/9/767/2009/acpd-9-767-2009.pdf 767 835 2009-01-09 Emissions from biomass burning in the Yucatan R. Yokelson J. D. Crounse P. F. DeCarlo T. Karl S. Urbanski E. Atlas T. Campos Y. Shinozuka V. Kapustin A. D. Clarke A. Weinheimer D. J. Knapp D. D. Montzka J. Holloway P. Weibring F. Flocke W. Zheng D. Toohey P. O. Wennberg C. Wiedinmyer L. Mauldin A. Fried D. Richter J. Walega J. L. Jimenez K. Adachi P. R. Buseck S. R. Hall R. Shetter University of Montana, Department of Chemistry, Missoula, MT 59812, USA Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, USA University of Colorado, Cooperative Institute for Research in the Environmental Sciences (CIRES), and Department of Atmospheric and Oceanic Sciences, Boulder, USA Now at the Paul Scherrer Institut, Villigen Switzerland National Center for Atmospheric Research, Boulder, CO, USA USDA Forest Service, Fire Sciences Laboratory, Missoula, MT, USA University of Miami, Rosenstiel School of Marine and Atmospheric Science, USA School of Ocean and Earth Sciences and Department of Oceanography, University of Hawaii, Honolulu, USA NOAA ESRL/CSD, Boulder, CO, USA University of Colorado, Department of Atmospheric and Oceanic Sciences, Boulder, USA Divisions of Engineering and Applied Science and Geological and Planetary Science, California Institute of Technology, Pasadena, USA University of Colorado, Cooperative Institute for Research in the Environmental Sciences (CIRES) and Department of Chemistry and Biochemistry, Boulder, USA School of Earth and Space Exploration and Department of Chemistry and Biochemistry, Arizona, State University, Tempe, USA In March 2006 two instrumented aircraft made the first detailed field measurements of biomass burning (BB) emissions in the Northern Hemisphere tropics as part of the MILAGRO project. The aircraft were the National Center for Atmospheric Research C-130 and a University of Montana/US Forest Service Twin Otter. The initial emissions of up to 49 trace gas or particle species were measured from 20 deforestation and crop residue fires on the Yucatan peninsula. This included two trace gases useful as indicators of BB (HCN and acetonitrile) and several rarely, or never before, measured species: OH, peroxyacetic acid, propanoic acid, hydrogen peroxide, methane sulfonic acid, and sulfuric acid. Crop residue fires emitted more organic acids and ammonia than deforestation fires, but the emissions from the main fire types were otherwise fairly similar. The Yucatan fires emitted unusually high amounts of SO₂ and particle chloride, likely due to a strong marine influence on this peninsula. As smoke from one fire aged, the ratio &Delta;O₃/&Delta;CO increased to ~15% in <~1 h similar to the fast net production of O₃ in BB plumes observed earlier in Africa. The rapid change in O₃ occurs at a finer spatial scale than is employed in global models and is also faster than predicted by micro-scale models. Fast increases in PAN, H₂O₂, and two organic acids were also observed. The amount of secondary organic acid is larger than the amount of known precursors. Rapid secondary formation of organic and inorganic aerosol was observed with the ratio &Delta;PM_2.5/&Delta;CO more than doubling in ~1.4&plusmn0.7 h. The OH measurements revealed high initial OH levels >1&times;10⁷ molecules/cm³. Thus, more research is needed to understand critical post emission processes for the second-largest trace gas source on Earth. It is estimated that ~44 Tg of biomass burned in the Yucatan in the spring of 2006. Mexican BB (including Yucatan BB) and urban emissions from the Mexico City area can both influence the March–May air quality in much of Mexico and the US. Adachi, K. and Buseck, P. 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