Environmental Science / Unit 7: Air Pollution and Climate
7.2 Smog and Temperature Inversions
Notes
Smog is air pollution that forms a haze in cities.
- Photochemical smog forms when sunlight reacts with nitrogen oxides ($NO_x$) and volatile organic compounds (VOCs) to make ground-level ozone. It is worst on hot, sunny days with heavy traffic.
- Industrial (gray) smog comes from burning coal that releases $SO_2$ and particles.
- A temperature inversion occurs when a layer of warm air sits over cooler air near the ground, trapping pollution. Cities in valleys (like Los Angeles) are prone to this.
- Health effects: asthma, bronchitis, lung irritation, and heart disease.
- Reducing smog: public transit, cleaner fuels, catalytic converters (which convert harmful exhaust gases to less harmful ones), and scrubbers on smokestacks.
- Example: a hot, sunny afternoon after morning rush hour gives peak ozone levels.
Practice
Which two ingredients react in sunlight to form photochemical smog?
$NO_x$ and VOCs produce ground-level ozone in the presence of sunlight.
A temperature inversion makes air pollution worse because it:
The warm layer acts like a lid and stops pollutants from rising.
Which device on a car reduces emissions of harmful gases such as CO and $NO_x$?
The converter chemically changes pollutants into $CO_2$, $N_2$, and $H_2O$.
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