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GATE 2021 CE (CE2) – Question 42

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

Consider: (i) wind-profile exponent is smaller for very unstable than neutral air; (ii) downwind concentration from an elevated source is inversely proportional to wind speed; (iii) neutral exponent is smaller than very unstable; (iv) concentration is directly proportional to wind speed. Choose correct combination.

  1. (i) false and (iii) true
  2. (i) true and (iv) true
  3. (ii) false and (iii) false
  4. (iii) false and (iv) false

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Show answer and explanation

Correct answer: (D) (iii) false and (iv) false

Explanation

Strong convective mixing in unstable air reduces vertical wind shear and its power-law exponent relative to neutral conditions. For fixed dispersion parameters, Gaussian-plume concentration has wind speed in the denominator. Thus (i),(ii) are true and (iii),(iv) are false, making **D** correct.