Photochemical Smog (College Board AP® Environmental Science): Flashcards
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Define photochemical smog.
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Define photochemical smog.
Photochemical smog is air pollution formed when the primary pollutants nitrogen oxides and volatile organic compounds react with heat and sunlight to produce secondary pollutants, often seen as a brown or gray haze over urban areas.
Which secondary pollutants are produced in photochemical smog?
Photochemical smog produces tropospheric ozone, aldehydes, and peroxyacyl nitrates (PANs).
Define industrial smog.
Industrial smog is a thick, yellowish fog created by the burning of fossil fuels.
True or False?
The ozone in photochemical smog is the same ozone that protects Earth from ultraviolet radiation.
False.
Smog contains tropospheric ozone, which harms life at high concentrations. The protective ozone that absorbs ultraviolet radiation is stratospheric ozone.
Which four factors affect the frequency and severity of smog in an area?
The frequency and severity of smog depend on local topography, climate conditions, population density, and the amount of fossil fuel use.
Why does Mexico City experience severe smog?
Mexico City lies at high altitude in an extinct volcano crater. Lower air oxygen makes fuel burn incompletely, emitting more carbon monoxide and other chemicals that are trapped within the crater.
High-rise buildings can create 'urban ' that reduce air movement and trap pollutants.
High-rise buildings can create 'urban canyons' that reduce air movement and trap pollutants.
Why do cities such as Los Angeles and Mumbai experience severe photochemical smog?
Los Angeles and Mumbai have high levels of insolation, and sunlight drives the chemical reactions that produce ozone.
What role does ultraviolet (UV) sunlight play in forming tropospheric ozone?
UV radiation breaks the bonds in NO₂, forming NO and releasing a single oxygen atom, which then bonds with atmospheric O₂ to form O₃.
Ozone levels are highest in the and during the summer due to higher levels of insolation.
Ozone levels are highest in the afternoon and during the summer due to higher levels of insolation.
What happens to ozone in the late afternoon and evening?
Ozone production slows and stops, and O₃ reacts with newly formed NO to form NO₂ and O₂.
What does nitrogen dioxide (NO₂) form when it reacts with water vapor?
Nitrogen dioxide reacts with water vapor to form nitric acid (HNO₃) and nitric oxide (NO).
How can lightning add smog-forming pollutants to the atmosphere?
Lightning strikes can convert nitrogen gas (N₂) in the atmosphere into nitrogen oxides (NOₓ).
What are some everyday sources of VOCs?
VOCs evaporate into the air from sources such as paints, cleaning products, new furniture, and gasoline.
True or False?
Only urban areas release the VOCs that contribute to brown smog.
False.
Trees release VOCs, so forested places can also contribute to brown smog, even if they are cooler.
Why is smog common in low-lying basins surrounded by mountains?
In a low-lying basin, smog is trapped in the valley and cannot be carried away by wind.
True or False?
Urban ozone levels tend to be low compared with rural ozone levels.
True.
In cities, ozone reacts with nitric oxide (NO) from vehicle emissions to form nitrogen dioxide, which keeps urban ozone levels low.
How can people reduce their fossil fuel use to cut photochemical smog?
People can reduce fossil fuel use by driving less, carpooling, using public transportation, and making homes and cars more energy efficient.
Fueling up during times of the day prevents gas fumes from heating up and producing ozone.
Fueling up during cooler times of the day prevents gas fumes from heating up and producing ozone.
How does maintaining vehicles help reduce smog?
Regular servicing, scheduled oil changes, and properly inflated tires improve gas mileage, which reduces emissions.
How does tropospheric ozone in smog affect the respiratory system?
Tropospheric ozone irritates the respiratory system, causing coughing and throat irritation and contributing to asthma. Prolonged exposure can reduce lung function.
Which groups are especially at risk from the hazards of smog?
Children and pregnant women are especially at risk from the hazards of smog.
How can exposure to smog affect the eyes?
Smog can irritate the eyes, causing inflammation, redness, tearing, and discomfort.
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