Emissions from forest fires near Mexico City

R. Yokelson (1) , S. Urbanski (2) , E. Atlas (3) , D. Toohey (4) , E. Alvarado (5) , J. Crounse (6) , P. Wennberg (7, 8) , M. Fisher (4) , C. Wold (2) , T. Campos (9) , K. Adachi (10, 11) , P. R. Buseck (10, 11) , W. M. Hao (2)

1 University of Montana
2 USDA Forest Service
3 University of Miami
4 University of Colorado [Boulder]
5 University of Washington [Seattle]
6 Division of Chemistry and Chemical Engineering
7 Division of Geological and Planetary Sciences [Pasadena]
8 EAS - Division of Engineering and Applied Science [Pasadena]
9 NCAR - National Center for Atmospheric Research [Boulder]
10 SESE - ASU School of Earth and Space Exploration
11 Department of Chemistry and Biochemistry [Tempe]

The emissions of NO_x 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 NO_x/VOC mass ratio for the MC-area mountain fires was ~0.38, which is similar to the NO_x/VOC ratio in the MC urban area emissions inventory of 0.43, but much larger than the NO_x/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.

Domaines: Océan, Atmosphère

R. Yokelson, S. Urbanski, E. Atlas, D. Toohey, E. Alvarado, et al.. Emissions from forest fires near Mexico City. Atmospheric Chemistry and Physics Discussions, 2007, 7 (3), pp.6687-6718. ⟨hal-00302784⟩