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Published: 2008

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This project was one of three collaborating grants designed to understand the atmospheric chemistry and aerosol particle microphysics impacting air quality in the Mexico City Metropolitan Area (MCMA) and its urban plume. The overall effort, titled MCMA- 2006, focused on: 1) the primary emissions of fine particles and precursor gases leading to photochemical production of atmospheric oxidants and secondary aerosol particles and 2) the measurement and analysis of secondary oxidants and secondary fine particular matter (PM) production, with particular emphasis on secondary organic aerosol (SOA). MCAM-2006 pursued it goals through three main activities: 1) performance and publication of detailed analyses of extensive MCMA trace gas and fine PM measurements made by the collaborating groups and others during earlier MCMA field campaigns in 2002 and 2003; 2) deployment and utilization of extensive real-time trace gas and fine PM instrumentation at urban and downwind MCMA sites in support of the MAX-Mex/MILAGRO field measurements in March, 2006; and, 3) analyses of the 2006 MCMA data sets leading to further publications that are based on new data as well as insights from analysis and publication of the 2002/2003 field data. Thirteen archival publications were coauthored with other MCMA-2003 participants. Documented findings included a significantly improved speciated emissions inventory from on-road vehicles, a greatly enhanced understanding of the sources and atmospheric loadings of volatile organic compounds, a unique analysis of the high fraction of ambient formaldehyde from primary emission sources, a much more extensive knowledge of the composition, size distributions and atmospheric mass loadings of both primary and secondary fine PM, including the fact that the rate of MCMA SOA production greatly exceeded that predicted by current atmospheric models, and evaluations of significant errors that can arise from standard air quality monitors for ozone and nitrogen dioxide. Deployment of the Aerodyne mobile laboratory, equipped with instruments from five collaborating laboratories, at the T0 urban supersite, four downwind sites and the Tula industrial area yielded unique trace gas and fine PM data sets during the March 2006 MAXMex/MILAGRO campaign. In addition, on-road measurements as the mobile laboratory moved between sites provided extensive data on 2006 MCMA fleet averaged vehicle emissions. Analyses of 2006 data sets have yielded the identification of a close correlation between the rate of production of SOA and "Odd Oxygen" (O3 + NO2) and primary organic PM with CO in the MCMA urban plume, a more sophisticated understanding of the interplay between nitrogen oxide speciation and ozone production, the identification of significant vehicular emission sources of HCN and CH3CN (usually associated with biomass burning), characterization of the aging of primary carbonaceous PM, and updated 2006 MCMA fleet on-road trace gas and fine PM emissions. Results from analyses of 2002/2003 and 2006 emissions and ambient measurements have conveyed to Mexican air quality managers who are using these data to devise and assess air quality management strategies. All data sets and published analyses are available to DOE/ASP researchers evaluating the impact of urban emissions on regional climate.