International Research Fellowship Program: Analysis of Mexico City Air Pollution Using Nitrogen and Sulfur Dioxide Column Density Measurements From UV/visible Spectroscopy

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0653087MelamedThe International Research Fellowship Program enables U.S. scientists and engineers to conduct nine to twenty-four months of research abroad. The program's awards provide opportunities for joint research, and the use of unique or complementary facilities, expertise and experimental conditions abroad.This award will support a twenty-four-month research fellowship by Dr. Megan L. Melamed to work with Dr. Michel Grutter at Universidad Nacional Autonoma de Mexico in Mexico City, Mexico.Megacities (cities with a population greater than 10 million) play a critical role in local, regional, and global air pollution. One megacity of primary interest is Mexico City, the third largest city in the world with an estimated population of ~20 million within an area of 1,500 square kilometers. Mexico City is located in the tropics at 2,240 meters above sea level in a flat basin surrounded by mountains on three sides. The primary sources of pollution in Mexico City are transportation, electricity generation, and industrial processes. The high-density population, the unique geographical setting, and multiple emission sources lead to high pollution episodes on a regular basis in Mexico City. Two pollutants of primary concern are sulfur dioxide and nitrogen dioxide, which are involved in atmospheric processes that form acid rain, tropospheric ozone, and particles. This research addresses the analysis and interpretation of ultraviolet (UV)/visible spectroscopy measurements of sulfur dioxide and nitrogen dioxide from two research sites in the greater Mexico City basin area. One research site is located in the Mexico City basin at La Universidad Nacional Autonoma de Mexico (UNAM). The second research site is Altzomoni, which is located to the southeast of the Mexico City basin at ~2,000 meters in altitude above the UNAM research site. Analysis and interpretation of the sulfur dioxide and nitrogen dioxide measurements from these two research sites is providing important information in regards to the outflow and in flow of pollution to the Mexico City basin and to the boundary layer dynamics of the Mexico City air pollution plume. In addition to the stationary research sites at UNAM and Altzomoni, a mobile research platform is being used to measure emission fluxes of sulfur dioxide and nitrogen dioxide from point sources in the Mexico City basin. The measurements from the stationary and mobile research platforms are being applied to chemical transport models in order to better simulate the transport and transformation of urban pollutants on regional and global scales. The sulfur dioxide and nitrogen dioxide measurements are contributing to the understanding of the impacts of pollution from a megacity on a local, regional, and global level.