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    Author(s): R.J. Yokelson; S.P. Urbanski; E.L. Atlas; D.E. Toohey; E.C. Alvarado; J.D. Crounse; P.O. Wennberg; M.E. Fisher; C.E. Would; T.L. Campos; K. Adachi; P.T. Buseck; W.M. Hao
    Date: 2007
    Source: Atmospheric Chemistry and Physics. 7: 5569-5584
    Publication Series: Scientific Journal (JRNL)
    PDF: Download Publication  (2.73 MB)


    The emissions of NOx (defined as NO (nitric oxide) + NO2 (nitrogen dioxide)) and hydrogen cyanide (HCN), per unit amount of fuel burned from fires in the pine forests that dominate the mountains surrounding Mexico City (MC) are about 2 times higher than normally observed for forest burning. The ammonia (NH3) emissions are about average for forest burning. The upper limit for the mass ratio of NOx to volatile organic compounds (VOC) for these MC-area mountain fires was ~0.38, which is similar to the NOx/VOC ratio in the MC urban area emissions inventory of 0.34, 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 United States, Los Angeles Basin). The molar emission ratio of HCN to carbon monoxide (CO) for the mountain fires was 0.0123 ± 0.007, which is 2 to 9 times higher than widely used literature values for biomass burning. The ambient molar ratio HCN/CO in the MC-area outflow is about 0.003 ± 0.0003. Thus, if only mountain fires emit significant amounts of HCN, these fires may be contributing about 25 percent of the CO production in the MC-area (~98 to 100 W and 19 to 20 N). Comparing the PM10/CO and PM2.5/CO mass ratios in the MC Metropolitan Area emission inventory (0.0115 and 0.0037 to the PM1/CO mass ratio for the mountain fires (0.133) then suggests that these fires could produce as much as ~79 to 92 percent of the primary fine-particle mass generated in the MC area. Considering both the uncertainty in the HCN/CO ratios and secondary aerosol formation in the urban and fire emissions implies that about 50 ± 30 percent of the "aged" fine particle mass in the March 2006 MC-area outflow could be from these fires.

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    Yokelson, R.J.; Urbanski, S.P.; Atlas, E.L., et al. 2007. Emissions from forest fires near Mexico City. Atmospheric Chemistry and Physics. 7: 5569-5584

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