Assessing the regional impacts of Mexico City emissions on air quality and chemistry M. Mena-Carrasco1,2, G. R. Carmichael3, J. E. Campbell4, D. Zimmerman5, Y. Tang3, B. Adhikary3, A. D'allura6, L. T. Molina2,7, M. Zavala2,7, A. García8, F. Flocke9, T. Campos9, A. J. Weinheimer9, R. Shetter9, E. Apel9, D. D. Montzka9, D. J. Knapp9, and W. Zheng9 1Universidad Andrés Bello, Department of Environmental Engineering, Santiago, Chile 2Massachusetts Institute of Technology, Department of Earth, Atmospheric and Planetary Sciences, Cambridge, MA, USA 3The University of Iowa, Center for Global and Regional Environmental Research, Iowa City, IA, USA 4University of California at Merced, School of Engineering, Merced, CA, USA 5The University of Iowa, Department of Statistical and Actuarial Science, Iowa City, IA, USA 6Arianet Environmental Modeling, Milan, Italy 7Molina Center for Energy and the Environment, La Jolla, CA, USA 8Universidad Nacional Autónoma de México, Delegación Coyoacán, México 9National Center for Atmospheric Research, Boulder, CO, USA
Abstract. The impact of Mexico City (MCMA) emissions is examined by studying its
effects on air quality, photochemistry, and on ozone production regimes by
combining model products and aircraft observations from the MILAGRO
experiment during March 2006. The modeled influence of MCMA emissions to
enhancements in surface level NOx, CO, and O3 concentrations
(10–30% increase) are confined to distances <200 km, near surface.
However, the extent of the influence is significantly larger at higher
altitudes. Broader MCMA impacts (some 900 km Northeast of the city) are
shown for specific outflow conditions in which enhanced ozone, NOy, and
MTBE mixing ratios over the Gulf of Mexico are linked to MCMA by source
tagged tracers and sensitivity runs. This study shows that the "footprint"
of MCMA on average is fairly local, with exception to reactive nitrogen,
which can be transported long range in the form of PAN, acting as a
reservoir and source of NOx with important regional ozone formation
implications. The simulated effect of MCMA emissions of anthropogenic
aerosol on photochemistry showed a maximum regional decrease of 40% in
J[NO2→NO+O], and resulting in the reduction of ozone production
by 5–10%. Observed ozone production efficiencies are evaluated as a
function of distance from MCMA, and by modeled influence from MCMA. These
tend to be much lower closer to MCMA, or in those points where modeled
contribution from MCMA is large. This research shows that MCMA emissions do
effect on regional air quality and photochemistry, both contributing large
amounts of ozone and its precursors, but with caveat that aerosol
concentrations hinder formation of ozone to its potential due to its
reduction in photolysis rates.
Citation: Mena-Carrasco, M., Carmichael, G. R., Campbell, J. E., Zimmerman, D., Tang, Y., Adhikary, B., D'allura, A., Molina, L. T., Zavala, M., García, A., Flocke, F., Campos, T., Weinheimer, A. J., Shetter, R., Apel, E., Montzka, D. D., Knapp, D. J., and Zheng, W.: Assessing the regional impacts of Mexico City emissions on air quality and chemistry, Atmos. Chem. Phys., 9, 3731-3743, doi:10.5194/acp-9-3731-2009, 2009.