Abstract
Mexico City is far advanced in its urban evolution, and cities in currently developing nations may soon follow a similar course. This paper investigates the strengths and weaknesses of infrastructures for the emerging megacities. The major driving force for infrastructure change in Mexico City is concern over air quality. Air chemistry data from recent field campaigns have been used to calculate fluxes in the atmosphere of the Valley of Mexico, for compounds that are important to biogeochemistry including methane (CH 4 ), carbon monoxide (CO), nonmethane hydrocarbons (NMHCs), ammonia (NH 3 ), sulfur dioxide (SO 2 ), nitrogen oxides (NO x and NO y ), soot, and dust. Leakage of liquified petroleum gas approached 10% during sampling periods, and automotive pollutant sources in Mexico City were found to match those in developed cities, despite a lower vehicle-to-person ratio of 0.1. Ammonia is released primarily from residential areas, at levels sufficient to titrate pollutant acids into particles across the entire basin. Enhancements of reduced nitrogen and hydrocarbons in the vapor phase skew the distribution of NO y species towards lower average deposition velocities. Partly as a result, downwind nutrient deposition occurs on a similar scale as nitrogen fixation across Central America, and augments marine nitrate upwelling. Dust suspension from unpaved roads and from the bed of Lake Texcoco was found to be comparable to that occurring on the periphery of the Sahara, Arabian, and Gobi deserts. In addition, sodium chloride (NaCl) in the dust may support heterogeneous chlorine oxide (ClO x ) chemistry. The insights from our Mexico City analysis have been tentatively applied to the upcoming urbanization of Asia.
Highlights
The Valley of Mexico contains what is arguably the world's largest metropolis with 20 million people coexisting in a space of 1000 km2 (UN, 1992; Villareal et al, 1996)
Extrema in the Mexico City measurements suggest that nonstandard oxidation and removal mechanisms exist for species including nonmethane hydrocarbons (NMHCs), peroxyacetyl nitrate (PAN), NH3, nitrates, particulates, and chlorine oxide (ClOx)
Increased global anthropogenic inputs of CH4 and certain NMHCs could occur if the 10% leakages of lique®ed petroleum gas (LPG) that were estimated in Mexico City applied to commercial gas infrastructures across coastal Asian cities
Summary
World's largest metropolis with 20 million people coexisting in a space of 1000 km (UN, 1992; Villareal et al, 1996). S. Elliott et al / Environmental Science & Policy 3 (2000) 145±156 dented characterization of the composition in the basin atmosphere (Doran et al, 1998; Edgerton et al, 1999). While Mexico City's air environment has been found to resemble peak smog years in cities of the Western United States (Seinfeld, 1989; Finlayson Pitts and Pitts, 1997), pollution extremes have been reached in the Valley of Mexico which may be more relevant to studies ofmegaurban' zones of the developing world. Whereas just 33% of Asia's population of 3 billion people currently live in urban areas, Organization for Economic Cooperation and Development (OECD) urbanization levels of 75±80% could be attained within two generations (UN, 1992, 1994). Strengths and weaknesses of the megainfrastructure are assessed, and the results are tentatively applied to the industrialization of Asia
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
