Smog Basics
What is photochemical smog primarily caused by?
The reaction of sunlight with nitrogen oxides and volatile organic compounds.
Which nitrogen compound is involved in forming photochemical smog?
Nitrogen oxides (NO and NO₂).
What health effects can photochemical smog cause in humans?
Respiratory problems like asthma, coughing, and eye irritation.
What type of weather condition can trap pollutants near the surface and worsen smog?
Temperature inversion.
Which U.S. state is especially known for its smog problems due to car emissions and sunlight?
California.
What is the key natural element needed to initiate photochemical smog formation?
Sunlight (UV radiation).
What are volatile organic compounds (VOCs)?
Organic chemicals that easily evaporate and contribute to smog formation.
What is one visible sign of photochemical smog in the air?
A brownish or hazy appearance.
What is the main reason smog is more common in summer months?
Stronger sunlight and higher temperatures increase photochemical reactions.
Why is smog formation worse in urban areas than rural ones?
Urban areas have more vehicles and industrial emissions.
What gas, harmful to human health, is a major component of photochemical smog?
Ground-level ozone (O₃).
What is the role of VOCs in the formation of ground-level ozone?
They react with nitrogen oxides in sunlight to form ozone.
What long-term environmental damage can smog cause besides human health effects?
Damage to crops, forests, and building materials.
How does NO₂ contribute to photochemical smog when exposed to sunlight?
It breaks down to form NO and free oxygen, which reacts to form ozone.
How do catalytic converters help reduce photochemical smog?
They convert harmful exhaust gases (like NOₓ and VOCs) into less harmful ones.
In what time of day is photochemical smog typically the worst?
Afternoon.
What type of reaction is involved in photochemical smog formation?
Photochemical (sunlight-driven) reactions.
What are PANs (peroxyacyl nitrates) and how are they related to smog?
They are toxic compounds formed in smog that cause eye irritation and damage plants.
Explain how a thermal inversion layer forms and why it worsens smog.
A warm air layer traps cooler air beneath, preventing pollutants from dispersing.
How do topography and geography influence smog formation in cities like Los Angeles?
Mountains trap air, and valleys collect pollutants, limiting dispersal.
What type of transportation is a major contributor to photochemical smog?
Cars and trucks (motor vehicles).
Describe the role of radicals (like hydroxyl radicals) in the complex chemistry of photochemical smog.
They initiate chain reactions that lead to ozone and PAN formation.
What’s the difference between good ozone and bad ozone?
Good ozone is in the stratosphere (blocks UV); bad ozone is at ground level (pollutant).
Why do high NO levels in the morning sometimes result in lower ozone levels early in the day?
NO can react with ozone and temporarily reduce its concentration before sunlight increases formation.
What are secondary pollutants, and name one example in smog?
Pollutants formed by reactions in the atmosphere; ozone is a key example.