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GATE 2023 CE (CE1) – Question 50

Air Pollution and Municipal Solid Wastes · Air pollution: pollutants, sources, impacts, control and air quality index · 2 marks · Multiple select

Which of the following statements is/are TRUE in relation to the Maximum Mixing Depth (or Height) 'D$_{max}$' in the atmosphere?

  1. D$_{max}$ is always equal to the height of the layer of unstable air
  2. Ventilation coefficient depends on D$_{max}$
  3. A smaller D$_{max}$ will have a smaller air pollution potential if other meteorological conditions remain same
  4. Vertical dispersion of pollutants occurs up to D$_{max}$

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Show answer and explanation

Correct answer: (B) Ventilation coefficient depends on D$_{max}$; (D) Vertical dispersion of pollutants occurs up to D$_{max}$

Explanation

The ventilation coefficient is the mixing depth times the mean wind speed, so it depends on $D_{max}$ (B). Pollutants mix vertically up to the mixing depth (D). A smaller mixing depth confines the pollutants to a smaller volume, so the pollution potential is larger, not smaller (C false). The mixing depth is not always the height of the unstable layer (A false).