130
L. T. Molina et al.
also increase particulate matter (PM) concentrations. The rainy season from June to
October has lower PM concentrations; however, because of intense photochemistry
occurring just before the afternoon showers, the ozone levels continues to be relatively high. The cool-dry season from November to February is characterized by
high levels of PM due to strong surface inversions and weak wind that also induce
higher concentrations of primary pollutants during the morning hours. As a result,
air pollution is a concern for MCMA residents throughout the year.
In addition to the topographic and meteorological drivers of air pollution in the
MCMA, the rapid population growth, uncontrolled urban development, high rates of
motorization, industrialization and consumption of fossil fuels combined to severely
impact the air quality in the region. With ozone peaked above 300 ppb 40–50 days a
year and high concentrations of all criteria pollutants in the late 1980s, Mexico City
was ranked as the most polluted megacity in the world [17]. The Mexico City government addressed the air pollution problem by establishing an air quality monitoring
network, and developing and implementing air quality management programs that
combined modifications to the regulatory framework with technological changes. In
collaboration with the Integrated Program on Urban, Regional and Global Air Pollution at the Massachusetts Institute of Technology, the project “Integrated strategy
for the air quality management in the Valley of Mexico 2001–2010” was also pivotal
for understanding the drivers of air pollution in the MCMA and providing scientific
basis for the design of air quality control strategies. Major measures implemented by
the government in the transport sector included removal of lead from gasoline and
its reformulation, mandatory use of catalytic converters in automobiles, reduction
of sulfur content in diesel fuel, reinforcement of the vehicle inspection and maintenance program, and implementation of the air pollution contingency program and “no
driving day” programs; other implemented measures in the industrial and residential
sectors included substitution of fuel oil in industry and power plants with natural
gas, and reformulation of liquefied petroleum gas for cooking and water heating [7].
These and other strategies led to significant reduction of ambient concentrations of
criteria air pollutants in the MCMA (see Fig. 21.2). However, there are still many
days with poor air quality with respect to O 3 , PM 10 and PM 2.5 . It is necessary to
implement new and effective strategies to continue improving air quality, especially
in the residential and transport sectors.
21.2.1 Field Measurement Studies in the MCMA
The high levels of aerosols and intense photochemical activities in the MCMA’s atmosphere and the unique combination of topographical and meteorological drivers have
attracted several large international collaborative studies on the emissions, transformations, and transport of air pollutants since the 1990s. The Mexico City Air Quality
Research Initiative (MARI) project obtained surface and vertical profile observations
of air pollutants and meteorology during 1990–1994 to support air quality modeling
studies [15]. The Aerosol and Visibility Evaluation (IMADA-AVER) campaign in
L. T. Molina et al.
also increase particulate matter (PM) concentrations. The rainy season from June to
October has lower PM concentrations; however, because of intense photochemistry
occurring just before the afternoon showers, the ozone levels continues to be relatively high. The cool-dry season from November to February is characterized by
high levels of PM due to strong surface inversions and weak wind that also induce
higher concentrations of primary pollutants during the morning hours. As a result,
air pollution is a concern for MCMA residents throughout the year.
In addition to the topographic and meteorological drivers of air pollution in the
MCMA, the rapid population growth, uncontrolled urban development, high rates of
motorization, industrialization and consumption of fossil fuels combined to severely
impact the air quality in the region. With ozone peaked above 300 ppb 40–50 days a
year and high concentrations of all criteria pollutants in the late 1980s, Mexico City
was ranked as the most polluted megacity in the world [17]. The Mexico City government addressed the air pollution problem by establishing an air quality monitoring
network, and developing and implementing air quality management programs that
combined modifications to the regulatory framework with technological changes. In
collaboration with the Integrated Program on Urban, Regional and Global Air Pollution at the Massachusetts Institute of Technology, the project “Integrated strategy
for the air quality management in the Valley of Mexico 2001–2010” was also pivotal
for understanding the drivers of air pollution in the MCMA and providing scientific
basis for the design of air quality control strategies. Major measures implemented by
the government in the transport sector included removal of lead from gasoline and
its reformulation, mandatory use of catalytic converters in automobiles, reduction
of sulfur content in diesel fuel, reinforcement of the vehicle inspection and maintenance program, and implementation of the air pollution contingency program and “no
driving day” programs; other implemented measures in the industrial and residential
sectors included substitution of fuel oil in industry and power plants with natural
gas, and reformulation of liquefied petroleum gas for cooking and water heating [7].
These and other strategies led to significant reduction of ambient concentrations of
criteria air pollutants in the MCMA (see Fig. 21.2). However, there are still many
days with poor air quality with respect to O 3 , PM 10 and PM 2.5 . It is necessary to
implement new and effective strategies to continue improving air quality, especially
in the residential and transport sectors.
21.2.1 Field Measurement Studies in the MCMA
The high levels of aerosols and intense photochemical activities in the MCMA’s atmosphere and the unique combination of topographical and meteorological drivers have
attracted several large international collaborative studies on the emissions, transformations, and transport of air pollutants since the 1990s. The Mexico City Air Quality
Research Initiative (MARI) project obtained surface and vertical profile observations
of air pollutants and meteorology during 1990–1994 to support air quality modeling
studies [15]. The Aerosol and Visibility Evaluation (IMADA-AVER) campaign in