Atmos. Chem. Phys. Discuss., 7, 6687-6718, 2007
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Emissions from forest fires near Mexico City
R. Yokelson1, S. Urbanski2, E. Atlas3, D. Toohey4, E. Alvarado5, J. Crounse6, P. Wennberg7, M. Fisher4, C. Wold2, T. Campos8, K. Adachi9,10, P. R. Buseck9,10, and W. M. Hao2
1University of Montana, Department of Chemistry, Missoula, MT 59812, USA
2USDA Forest Service, Fire Sciences Laboratory, Missoula, MT, USA
3University of Miami, Rosenstiel School of Marine and Atmospheric Science, USA
4University of Colorado, Department of Chemistry, Boulder, USA
5University of Washington, College of Forest Resources, Seattle, USA
6Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, USA
7Divisions of Engineering and Applied Science and Geological and Planetary Science, California Institute of Technology, Pasadena, USA
8National Center for Atmospheric Research, Boulder, CO, USA
9School of Earth and Space Exploration, Arizona State University, Tempe, AZ, USA
10Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ, USA

Abstract. The emissions of NOx and HCN (per unit amount of fuel burned) from fires in the pine-savannas that dominate the mountains surrounding Mexico City (MC) are about 2 times higher than normally observed for forest burning. The NH3 emissions are about average for forest burning. The NOx/VOC mass ratio for the MC-area mountain fires was ~0.38, which is similar to the NOx/VOC ratio in the MC urban area emissions inventory of 0.43, but much larger than the NOx/VOC ratio for tropical forest fires in Brazil (~0.068). The nitrogen enrichment in the fire emissions may be due to deposition of nitrogen-containing pollutants in the outflow from the MC urban area. This effect may occur worldwide wherever biomass burning coexists with large urban areas (e.g. the tropics, southeastern US, Los Angeles Basin). The molar emission ratio HCN/CO for the mountain fires was ~0.0128±0.0096: 2–9 times higher than widely used literature values for biomass burning. The MC-area/downwind molar ratio of HCN/CO is about 0.003±0.0003. Thus, if other types of biomass burning are relatively insignificant, the mountain fires may be contributing about 23% of the CO production in the MC-area (~98–100 W and 19–20 N). Comparing the PM10/CO mass ratio in the MC Metropolitan Area emission inventory (0.011) to the PM1/CO mass ratio for the mountain fires (0.133) then suggests that these fires could produce as much as ~78% of the fine particle mass generated in the MC-area.

Citation: Yokelson, R., Urbanski, S., Atlas, E., Toohey, D., Alvarado, E., Crounse, J., Wennberg, P., Fisher, M., Wold, C., Campos, T., Adachi, K., Buseck, P. R., and Hao, W. M.: Emissions from forest fires near Mexico City, Atmos. Chem. Phys. Discuss., 7, 6687-6718, doi:10.5194/acpd-7-6687-2007, 2007.
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