Photochemical Smog
Definition and meaning of Photochemical Smog in chemistry.
Photochemical smog is a mixture of pollutants that are formed when nitrogen oxides and volatile organic compounds react to sunlight, creating a brown haze above cities.
In more detail
This type of air pollution typically develops in warm, sunny urban areas with heavy automobile traffic. The ultraviolet radiation from the sun provides the energy needed to initiate photochemical reactions between primary pollutants from vehicle exhaust, leading to the creation of secondary pollutants like ozone and peroxyacetyl nitrate. These secondary pollutants are highly reactive oxidants that can cause respiratory problems, eye irritation, and damage to plant life. Because the reactions depend on sunlight, photochemical smog levels usually peak in the mid-afternoon.
Key facts
| Field | General Chemistry |
|---|---|
| Primary Pollutants | Nitrogen oxides, volatile organic compounds |
| Formula Example | O3 (Ozone) |
The thick, brownish-yellow haze often seen over Los Angeles or Beijing during hot summer days is a classic example of severe photochemical smog.
Frequently asked questions
What is the main cause of photochemical smog?
Vehicle exhaust emissions are the primary source of the nitrogen oxides and volatile organic compounds that react to form the smog.
Why is photochemical smog worse in the summer?
The reactions that create it require sunlight and are accelerated by higher temperatures and longer daylight hours.