Atmospheric Chemistry and Physics www.atmos-chem-phys.net 1680-7316 1680-7324 9 19 2009 10.5194/acp-9-7325-2009 http://www.atmos-chem-phys.net/9/7325/2009/ http://www.atmos-chem-phys.net/9/7325/2009/acp-9-7325-2009.html http://www.atmos-chem-phys.net/9/7325/2009/acp-9-7325-2009.pdf 7325 7342 2009-10-02 Eddy covariance flux measurements of pollutant gases in urban Mexico City E. Velasco evelasco@mce2.org S. Pressley R. Grivicke E. Allwine T. Coons W. Foster B. T. Jobson H. Westberg R. Ramos F. Hernández L. T. Molina B. Lamb Molina Center for Energy and the Environment (MCE2), La Jolla, CA, USA Laboratory for Atmospheric Research, Dept. of Civil and Environmental Engineering, Washington State University, Pullman, WA, USA Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA Secretaría del Medio Ambiente del Gobierno del Distrito Federal, México D.F., México now at: Dept. of Geography, Faculty of Arts and Social Sciences, National University of Singapore, Singapore now at: William J. Clinton Foundation, Clinton Climate Initiative, México D.F., México Eddy covariance (EC) flux measurements of the atmosphere/surface exchange of gases over an urban area are a direct way to improve and evaluate emissions inventories, and, in turn, to better understand urban atmospheric chemistry and the role that cities play in regional and global chemical cycles. As part of the MCMA-2003 study, we demonstrated the feasibility of using eddy covariance techniques to measure fluxes of selected volatile organic compounds (VOCs) and CO₂ from a residential district of Mexico City (Velasco et al., 2005a, b). During the MILAGRO/MCMA-2006 field campaign, a second flux measurement study was conducted in a different district of Mexico City to corroborate the 2003 flux measurements, to expand the number of species measured, and to obtain additional data for evaluation of the local emissions inventory. Fluxes of CO₂ and olefins were measured by the conventional EC technique using an open path CO₂ sensor and a Fast Isoprene Sensor calibrated with a propylene standard. In addition, fluxes of toluene, benzene, methanol and C₂-benzenes were measured using a virtual disjunct EC method with a Proton Transfer Reaction Mass Spectrometer. 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