Pollution: vehicle catalytic converters increased platinum concentration by up to 700 times

In the last 14 years, polluting metals in the atmospheric environment of Mexico City have decreased drastically, such as lead; cars now have catalysts that use platinum to decompose carbon monoxide into carbon dioxide (CO2), which could explain why the concentration of this metal increased up to 700 times, said Ofelia Morton Bermea, a specialist from the Institute of Geophysics (IGf).

Participating in the discussion "The crude truth of pollution in Mexico", university experts agreed that the biggest generators of pollutants in the Mexican capital are public and private transport; in addition, the "Hoy no Circula" ("Today do not circulate") program has reduced emissions, although the presence of other elements has increased, as is also the case of antimony since this city has more than five million motor vehicles.

It should be noted that, according to UN-Habitat, in some metropolitan areas, such as the Valley of Mexico, emissions generated by vehicles represent up to 60 percent of the total pollution by coarse suspended particles (PM-10).

The specialist in Environmental Geochemical Evaluation and Contamination explained that, as part of the tests carried out during 11 years with a group of researchers to determine the origin of the contaminating sources, it was determined that, on average, 65 percent of the metals in the atmosphere of Mexico City are of geogenic origin; that is, they come from the diffusion of dust, especially from the northern zone.

In turn, Ricardo Torres Jardón, from the Institute of Atmospheric Sciences and Climate Change (ICACC), indicated that most of the country's emissions come from energy production and, mainly, from the use of oil, taking into account that most of the crude oil obtained is "dirty" despite the refining process to which it is subjected. Historically, we have always lagged in the application of control technologies in this area. The Institute's proposal, supported by data, is to stop using this type of fuel to avoid greenhouse gases, he said.

During his speech at the "Science and Humanities Fair 2021", the chemical engineer pointed out that from 2010 to date the levels of fine suspended particles, ozone, and other pollutants of photochemical origin, including hydrocarbons, have been sustained or are growing again.

Bertha Oliva Aguilar, a specialist in Materials Physics, recalled that a study by the World Health Organization ranked Monterrey, Toluca, Guadalajara, Salamanca, León, and Irapuato as the most polluted Mexican cities, with Mexico City in seventh place.

"If we consider that most of the pollutants are particulate material, which is not only dangerous to health because of its size, but also because of its composition, we are faced with the problem that if we have a monitoring station installed in a tricky way, that is, on rooftops or in places far from the critical points where there are specific emissions of pollutants, it will acquire values that are not real", continued the expert.

It is important, she said, to consider the natural sources that sometimes can give a greater contribution than the anthropic ones, as in the case of the volcanic emissions of Popocatepetl, which in the last 20 years have been active, and a great part of the suspended material comes from there.

Meanwhile, Nimcy Arellanes Cancino, from the Academic Unit of Regional Studies of the Humanities Coordination, mentioned that there are 11 sources of atmospheric pollution, including water, radioactive, soil, garbage generation, acoustic, visual, and light pollution. These last ones affect sleep and also the rest of the animals.

For the university professor, reforestation is one of the main actions to control it in the cities with the use of native species, a process that began in the 19th century with trees increasingly different from those common in the country. The historian and anthropologist suggested being aware of the urgent need to save energy, reduce the consumption of clothing and footwear, as well as take advantage of daylight to carry out most of our activities.

Other sources of pollution in Mexico City

In the Megalopolis of the Valley of Mexico Metropolitan Area, composed of the capital and five neighboring states in constant interaction -Puebla, Hidalgo, Tlaxcala, Morelos, and the State of Mexico-, there are 400 open-air dumps, whose garbage generates a methane gas that causes ozone when the temperature rises to 30 degrees Celsius. In this territory of 30 million people, there are some 50,000 industrial boilers, many of them in hotels and shops that continue to operate despite the emergency.

The boilers burn gas or diesel, a fuel used by the 350,000 cargo trucks and buses that circulate in the area, and which in Mexico is distributed by the state-run oil company Pemex with 500 parts per million (ppm) of sulfur when it should have 15 ppm in order not to contaminate. The time of year does not play in favor of dispersing the contaminants, due to the lack of rain and wind, and the increase in consumption of heaters and stoves in the houses due to the confinement, as well as the forest fires.

The National Forestry Commission reported a daily average of more than 50 active forest fires. Although none were close to the capital, their ashes did reach it because of the winds, as happened with the contamination of the Pemex refinery in Tula, in the central state of Hidalgo. Another black spot is the capital's airport, which each year generates 12 million tons of carbon dioxide and eight million tons of nitrogen oxide.

Among the contaminants reported by the capital's government are the so-called PM2.5 particles, which because of their tiny size can penetrate the bloodstream and organs, causing serious diseases.

Sources: UNAM