Mexico City's Air: What's The Cleanest Source?

Mexico City's air pollution reached its peak in the 1980s and 1990s, with the United Nations declaring it the world's most polluted city in 1992. The air quality has since improved, but the city remains one of the most polluted in the western hemisphere. This improvement can be attributed to various factors, including the Mexican government's efforts to reduce emissions, the closure or relocation of polluting factories, and restrictions on vehicle usage. However, certain factors unique to the city's geography, such as its high altitude and basin-like topography surrounded by mountains, contribute to the entrapment of air pollutants. While it is challenging to pinpoint the least contributing factor, the implementation of environmental sustainability initiatives, increased green areas, and the modernization of forest fire prevention programs are all positive steps towards mitigating air pollution in Mexico City.

Volcanic activity

Mexico City's air pollution has been a concern for the city's population and health officials for decades. The city's high altitude of 7382 feet above sea level results in oxygen levels that are 25% lower, and carbon-based fuels do not combust completely. The city's topography, situated in a basin surrounded by mountains, also contributes to trapping pollution. The proliferation of vehicles, rapid industrial growth, and population growth have further exacerbated the problem.

To address the air pollution issue, the Mexican government has implemented programs like "No-Drive Days" and promoted alternatives such as bus rapid transit lines and bike-sharing systems. The government has also introduced initiatives like ProAire, which aims to minimize unnecessary emissions by optimizing bus routes and introducing cleaner buses.

While volcanic activity can contribute to air pollution in Mexico City, it is not a constant or primary source of pollution like vehicular emissions or industrial activities. The intermittent nature of volcanic eruptions means that their impact on air quality varies over time and is subject to other environmental factors. Therefore, while volcanic activity may have temporarily elevated pollution levels, it is reasonable to assume that it has contributed the least to Mexico City's overall air pollution problem when compared to more consistent and human-induced sources.

To conclude, while volcanic activity can have a significant impact on air quality during periods of intense eruptions, other factors such as vehicle emissions, industrial growth, and geographical characteristics play a more consistent and prominent role in Mexico City's air pollution.

Solar radiation

The intensity of solar radiation varies throughout the year, with higher radiation typically occurring during the summer months. For example, in North Mexico City, the average monthly solar radiation ranged from a minimum of 14.90 MJ/m2 in December to a maximum of 21.60 MJ/m2 in April over a 14-year period from 1999 to 2012.

During the winter, when the sun's declination is more negative, solar radiation reaches the Earth's surface at a greater inclination, reducing the energy per unit area. This results in a predominantly latitudinal distribution of UVB radiation across the country, with modifications due to major topographic features such as the Volcanic Belt and the Sierra Madre mountain ranges.

While solar radiation itself is not a pollutant, it can interact with pollutants in the atmosphere and impact their dispersion. For example, in 2019, higher solar radiation, coupled with other factors like above-average temperatures, low rainfall, and a prolonged drought, contributed to worsening air pollution in Mexico City.

To address air pollution, Mexico City has implemented various measures, including vehicular restrictions, the promotion of public and active transport, and the expansion of green areas. These initiatives aim to reduce emissions and improve the overall air quality in the city.

High-pressure systems

Mexico City has long struggled with air pollution, which has been a concern for the city's population and health officials for decades. In 1992, the United Nations (UN) declared Mexico City the most polluted city in the world. While the city has since dropped to 917th place in terms of pollution, air pollution remains a significant issue.

One factor that has contributed to the city's air pollution problem is its topographical location. Mexico City is situated in a basin surrounded by mountains, which creates a bowl-like effect. This natural formation, combined with the city's high altitude, makes it more difficult for pollutants to disperse, trapping them in the city.

In 2019, wildfires further exacerbated the city's air pollution. The Ministry of Environment and Natural Resources reported at least 66 fires in the capital and 130 more in the neighbouring State of Mexico. The smoke and particles from these fires, coupled with above-average temperatures, low rainfall, drought, and high solar radiation, and a high-pressure system, created a perfect storm for worsening air quality.

To address the impact of high-pressure systems on air quality, it is crucial to implement strategies that facilitate the dispersion of pollutants. This can include increasing green areas and reforestation efforts, as outlined in Mexico's environmental policies. By expanding and restoring urban green spaces, the city can mitigate the resuspension of particles and improve overall air quality. Additionally, promoting public transport, regulating fuel consumption, and transitioning to cleaner and more efficient energy sources can help reduce the emission of pollutants, thereby minimising their impact on the atmosphere, even during high-pressure systems.

Low rainfall

In 2019, Mexico City experienced a period of low rainfall, which, when combined with other environmental factors, exacerbated the city's air pollution problem. During this time, the Ministry of Environment and Natural Resources reported at least 66 fires in the capital and 130 in the neighbouring State of Mexico. The smoke and particles from these wildfires contributed to the already poor air quality. Additionally, above-average temperatures, prolonged drought, higher solar radiation, and a high-pressure system prevented the dispersion of contaminants, leading to a further build-up of pollutants in the air.

The impact of low rainfall on air quality is a serious concern for Mexico City, particularly when coupled with other human activities that release pollutants. The city's administration and the Metropolitan Environmental Commission (MEC) have implemented programmes such as the Comprehensive Programme Against Air Pollution (PICCA) and ProAire to address this issue. These programmes promote actions such as reducing energy consumption, increasing the use of public and electric transportation, encouraging active transport like cycling and walking, and expanding green areas and reforestation efforts.

While low rainfall can contribute to air pollution, it is essential to recognise that human activities play a significant role as well. Mexico City's rapid industrialisation, population growth, and proliferation of vehicles have led to a substantial increase in emissions. The incomplete combustion of carbon-based fuels, the use of organic fuels for cooking and heating, and the emissions from a growing number of vehicles all contribute to the city's air pollution crisis. Therefore, addressing the complex interplay of geographical and human factors is crucial to improving air quality in Mexico City.

Population migration

Mexico City's population grew rapidly in the 20th century as industrialization drew thousands of migrants from across the globe. This population boom, coupled with the proliferation of vehicles, rapid industrial growth, and the city's high altitude, led to severe air quality issues. The basin-like topography of Mexico City, surrounded by mountains, also contributes to trapping air pollutants.

To address these issues, the Mexican government has implemented various measures over the years. In 1989, the "No-Drive Days" policy was introduced, prohibiting driving one day a week, later expanded to include Saturdays. The government has also promoted public transportation and bicycle-sharing systems, and implemented programs like the Comprehensive Programme Against Air Pollution (PICCA) and ProAire to improve air quality.

However, despite these efforts, air pollution in Mexico City remains a concern. The city's unique geographical location, with high altitude and a basin-like topography, makes it challenging to disperse pollutants. While the severity of air pollution has decreased significantly, dropping from the most polluted city to 917th, more action is needed to tackle the root causes of the problem, including the impact of population migration.

To further mitigate the effects of population migration on air pollution, a comprehensive approach is necessary. This includes continued promotion of public transportation and active transport like cycling and walking, as well as stricter emissions control regulations for vehicles. Additionally, addressing the energy consumption and industrial sectors, transitioning to cleaner and more efficient energy sources, and expanding green areas and reforestation efforts can help reduce the environmental impact of population migration.

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