Estimation of atmospheric stability for the city of Zacatecas, Mexico

In the present work, due to the importance of the dispersion of pollutants in the air, the modified Pasquill-Gifford classification was used to determine the classes of atmospheric stability, which serve to indirectly identify the increase or decrease of the existing mechanical and convective turbulence, conditions that at the same time affect the dispersion of pollutants; the above was carried out in the municipality of Zacatecas in the years of 2019 and 2020; the data of concentrations of Carbon monoxide (CO), sulfur dioxide (SO2), nitrogen oxides (NOX), PM10 and PM2.5 particles, and ozone (O3) released from a monitoring station and were contrasted with the estimated atmospheric stability classes in order to observe the influence of these classes on these pollutants; and finally, based on the results obtained, it was identified in which seasons of the year there is a greater and lesser dispersion of pollutants. Once this process was carried out, a series of recommendations were issued about the feasibility of using this classification in the city of Zacatecas. Maximum frequencies of class A were obtained between 9:00 and 12:00 hours, considered the most unstable with 52.22% for spring, 53.57% for summer, 44.87% for autumn, and 40% for winter. When class A increased its frequency, the concentration of particles decreased, and when class F increased, the concentration of particles increased. Therefore, it is recommended to consider different factors that may influence the dispersion of pollutants in the city of Zacatecas and, regarding the results obtained, make use of this classification only in hourly averages. Likewise, the Pasquill-Gifford classification could be combined with atmospheric models to determine the behavior of particles in different periods with greater confidence.