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Photochemical Smog Formation
AP Environmental Science · Unit 7 Atmospheric Pollution
Learning Objectives
NOx: Nitrogen Oxides emitted mostly by car exhaust during the morning commute.
VOCs: Volatile Organic Compounds (gasoline vapors, paint, pine trees).
Sunlight: Essential catalyst. UV rays break apart NOx so oxygen can form O3.
Ozone (O3): Tropospheric "Bad" Ozone. Highly irritating to lungs and plant tissue. Usually peaks in the afternoon.
Tags
Air PollutionSmogOzoneNOx
Time of Day (Diurnal Cycle)
06:00 (Early Morning)
The Chemical Recipe
NOx + VOCs + Sunlight = Tropo O3
Morning: Commuter traffic spikes NOx levels.
AP Exam Tip
"Ozone is Good Up High, Bad Nearby." Stratospheric ozone blocks UV radiation. Tropospheric (ground-level) ozone is a heavy oxidant that damages lungs and represents the primary component of photochemical smog. It ALWAYS peaks in the hot afternoon!