Why does the concentration of ozone in metropolitan areas decrease at night?

The concentration of ozone in metropolitan areas decreases at night primarily due to the fact that ozone formation relies on the presence of sunlight. During the day, ultraviolet (UV) light from the sun catalyzes chemical reactions between pollutants such as volatile organic compounds (VOCs) and nitrogen oxides (NOx) in the atmosphere, resulting in the creation of ozone at ground level.

At night, the absence of sunlight halts these reactions, leading to a decrease in ozone production. Even though other factors, such as traffic and temperature changes, can influence air quality and pollution levels, they do not directly result in the significant reduction of ozone itself as the lack of sunlight does.

Understanding the role of sunlight in the chemical processes that generate ground-level ozone is essential for comprehending daily variations in ozone levels in urban environments.