Industrial pollution: Sulfur dioxide oxidation in Mexico City

Air pollution is one of the major problems in Mexico City. The metropolitan area, located at 2240 m above sea level, lies within a closed basin, at a latitude of 19/sup 0/ N. This, plus the huge population of more than 14 million people, the ever increasing number of cars (about 1.7 million), the more than 170 000 trucks and buses (with diesel engines and not all of them in good shape), as well as the most important industrial concentration in the Country, forces this area to be one of the highest air pollution potential locations in the world. Photochemical smog problems have been recognized in Mexico City a long time ago, but industrial sources might do more than just adding a different kind of pollution to the total if their emissions get involved in photochemical reactions. Actually, and considering that there are no regulations for SO2 emissions, its ambient concentrations should be important. Since they are not, SO2 must be converted to some compound with a higher degree of oxydation, mainly sulfate. Observed sulfate concentrations are large and they could be responsible for an important part of the visibility reduction, specially in the northern part of the basin. Thismore » study is an attempt to find the main mechanism of oxydation for sulfur dioxide originated in industrial sources.« less