Air quality in the Mexico City Metropolitan Zone as a tool to evaluate the effect of the weekend strategy to control atmospheric ozone.

摘要

Since the mid 1970′s the behavior of the air quality from different pollutants has been determined for weekdays and weekends in several USA cities. The Mexico City Metropolitan Zone (MCMZ) presents different behaviors in the activities which are potential sources of atmospheric pollutants, being Saturday a critical day with greater vehicular emissions. With the purpose of reducing the emissions of atmospheric pollutants from mobile sources, some measures have been applied; inspection and maintenance (I/M), use of catalytic converters in vehicles (since 1991), some gasoline reformulations, restriction of vehicular traffic, etc. In relation to the restriction of vehicular traffic since 1989 there was applied the program “a day without a car” which restricts the circulation of vehicles based on the license plates numbers one day a week. New vehicles are left exempt of this restriction for eight years, and recently for older vehicles the program has been made stricter extending the not circulation (in a well defined lottery) to Saturdays. This paper has the purpose to evaluate the temporal (days of the week) and spatial (5 sites) variations of atmospheric ozone which for several decades has been the main atmospheric pollutant problem in the MCMZ. These air quality data are analyzed considering two periods, a first period from July to December of 2006 and 2007 (before weekend strategy) and the second subsequent to the implementation of this program, from July to December of 2008 (after the beginning of weekend strategy).