Modeling the impacts of biomass burning on air quality in and around Mexico City
- ISSN: 16807316
- DOI: 10.5194/acp-13-2299-2013
The local and regional impacts of open fires and trash burning on ground-level ozone (O3) and fine car- bonaceous aerosols in the Mexico City Metropolitan Area (MCMA) and surrounding region during two high fire pe- riods 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 sim- ulated 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 burn- ing on surface O3 concentrations in the MCMA and sur- rounding region. In contrast, they had important influences on OA and elemental carbon (EC), increasing primary OA (POA) by ∼60 %, secondary OA (SOA) by ∼22 %, total OA (TOA=POA+SOA) by ∼33 %, and EC by ∼22 %, on both the local (urban) and regional scales. Although the emis- sions of trash burning are substantially lower than those from open fires, trash burning made slightly smaller but compara- ble contributions toOAas open fires did, and exerted an even higher influence on EC. Of the ∼22% enhancement in SOA concentrations (equivalent to a∼15%increase in TOA) sim- ulated, about two third was attributed to the open fires and one-third to the trash burning. On the annual basis and taking the biofuel use emissions into consideration, we estimated that open fires, trash burning and biofuel use together con- tributed about 60%to the loading of POA, 30%to SOA, and 25% to EC in both the MCMA and its surrounding region, of which the open fires and trash burning contributed about 35% to POA, 18% to SOA, and 15% to EC. The estimates of biomass burning impacts in this study may contain consid- erable uncertainties due to the uncertainties in their emission estimates in magnitude, temporal and spatial distribution, ex- trapolations and the nature of spot comparison. More obser- vation and modeling studies are needed to accurately assess the impacts of biomass burning on tropospheric chemistry, regional and global air quality, and climate change.