Effect of hydrocarbons and nitrogen oxides on ozone formation in smog chambers exposed to solar irradiance of Mexico City

Abstract

Outdoor smog chambers experiments were performed on air to determine the answer of maximum ozone levels to changes in the initial hydrocarbons, HC, and nitrogen oxide NOx. These captive-air experiments under natural irradiation were carried out. Typically, eight chambers were filled with Mexico City air in the morning. In some of those chambers, the initial HC and/or NOx concentrations were varied by 25%to +50% by adding various combinations of a mixture of HC, clean air, or NOx (perturbed chambers). The Os and NOx concentration in each chamber was monitored throughout the day to determine O₃ (max). The initial HC and NOx concentration effects were determined by comparing the maximum ozone concentrations measured in the perturbed and unperturbed chambers. Ozone isopleths were constructed from the empirical model obtained of measurements of the eight chambers and plotted in a graph whose axes were the initial HC and NOx values. For the average initial conditions that were measured in Mexico City, It was found that the most efficient strategy to reduce the maximum concentration of O₃ is the one that reduces NOx.