Atmos. Chem. Phys. Discuss., 12, 22891-22943, 2012
© Author(s) 2012. This work is distributed
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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.
Modeling the impacts of biomass burning on air quality in and around Mexico City
W. Lei1, G. Li1,2, and L. Molina1,2
1Molina Center for Energy and the Environment, La Jolla, CA, USA
2Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA

Abstract. The local and regional impacts of open fires and trash burning on ground-level ozone (O3) and fine carbonaceous aerosols in the Mexico City Metropolitan Area (MCMA) and surrounding region during two high fire periods in March 2006 have been evaluated using WRF-CHEM model. The model captured reasonably well the measurement-derived magnitude and temporal variation of the biomass burning organic aerosol (BBOA), and the simulated impacts of open fires on organic aerosol (OA) were consistent with many observation-based estimates. We did not detect significant effects of open fires and trash burning on surface O3 concentrations in the MCMA and surrounding region. In contrast, they had important influences on OA and elemental carbon (EC), contributing about 60, 22, 33, and 22% to primary OA (POA), secondary OA (SOA), total OA (TOA), and EC, respectively, on both the local and regional scales. Although the emissions of trash burning are substantially lower than those from open fires, trash burning made slightly smaller but comparable contributions to OA as open fires did, and exerted an even higher influence on EC. SOA formation due to the open fires and trash burning enhanced the OA concentration by about 10 and 5% in the MCMA, respectively. On the annual basis and taking the biofuel use emissions into consideration, we estimated that biomass burning contributed about 60, 30, and 25%, respectively, to the loadings of POA, SOA and EC in both the MCMA and its surrounding region, with about 35, 18, and 15% from open fires and trash burning. The estimates of biomass burning impacts in this study may contain considerable uncertainties due to the uncertainties in their emission estimates, extrapolations and the nature of spot comparison. More observation and modeling studies are needed to accurately assess the impacts of biomass burning on tropospheric chemistry, regional and global air quality, and climate change.

Citation: Lei, W., Li, G., and Molina, L.: Modeling the impacts of biomass burning on air quality in and around Mexico City, Atmos. Chem. Phys. Discuss., 12, 22891-22943, doi:10.5194/acpd-12-22891-2012, 2012.
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