Mexico City is among the 10 largest cities of the world
(Ezcurra and Mazari, 1998), with people exposed daily to
high pollution episodes. Elevated ozone concentrations
in the city routinely violate the environmental air quality
standards (110 ppbv over 1 h). The city's location in the
tropics (19 N) and high elevation (2240 masl) create a
high-radiation environment, a condition that drives the
chemistry leading to the formation of photochemical
ozone. One of the key reactions in the ozone formation
in the troposphere is the photodissociation of NO2 at
j(430 nm.
NO2
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