Answer: A layer of warm air sits above cooler, denser surface air, creating stable atmospheric stratification that suppresses convective uplift of pollutants, causing them to accumulate near the ground.
- A A warm surface generates strong updrafts that carry pollutants above the cloud layer, which then reflect them back as acid precipitation under typical physiological conditions according to standard texts
- B A layer of warm air sits above cooler, denser surface air, creating stable atmospheric stratification that suppresses convective uplift of pollutants, causing them to accumulate near the ground
- C Rapid cooling of the upper atmosphere causes pollutants to condense into droplets that fall back to the surface before dispersing in general clinical practice as frequently documented in most reference accounts
- D Easterly trade winds reverse during a temperature inversion, trapping urban air in a closed circulation cell with little ventilation under normal conditions as generally observed in typical laboratory settings
Correct answer: B. A layer of warm air sits above cooler, denser surface air, creating stable atmospheric stratification that suppresses convective uplift of pollutants, causing them to accumulate near the ground
Explanation: Normally, air temperature decreases with altitude and warm, buoyant surface air rises, dispersing pollutants. During a temperature inversion, a layer of warmer, lighter air caps a cooler, denser layer near the surface. The surface air cannot rise through the warmer air above, so pollutants accumulate and intensify in the stable lower layer. This is what allowed the 1952 Great London Smog to reach lethal concentrations over four days, killing approximately 4,000 people.
Classical smog is a reducing mixture of SO₂ and fog, while photochemical smog is an oxidising mixture generated by UV-driven reactions of NOx and hydrocarbons.
Concept context
Understand how human activities alter the atmosphere, water, and soil. Covers air pollutants, smog types, ozone depletion, acid rain, greenhouse effect, water and soil pollution, and the principles of green chemistry.