Air Pollution Control Questions and Answers – Plume Behaviour and Characteristics

This set of Air Pollution Control Multiple Choice Questions & Answers (MCQs) focuses on “Plume Behaviour and Characteristics”.

1. Which of the following factors controls the air pollutant plume behaviour?
a) Atmospheric instability only
b) Wind turbulence only
c) Wind turbulence and degree of atmospheric instability
d) Turbulence, instability of atmosphere and lapse rate
View Answer

Answer: c
Explanation: The lapse rate controls the wind turbulence and the degree of the atmospheric instability; hence, it is already a criterion for consideration. These two factors determine the movement of an air pollutant plume emitted from industries.

2. Which of the following diagrams shows the plume behaviour of looping?
a)

b)

c)

d)

View Answer

Answer: b
Explanation:

It shows the plume behaviour of looping. This plume is emitted from industry stacks in superadiabatic atmospheric conditions, which are highly unstable. The plume reaches the ground as it moves away from the stack.

3. Which plume behaviour is represented in this diagram?

a) Fanning
b) Coning
c) Lofting
d) Fumigation
View Answer

Answer: a
Explanation: The given diagram illustrates the phenomenon of fanning. It occurs in the case of the surface inversion. The dispersion of air pollutants occurs due to light winds. The atmosphere is stable in this case.
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4. When does looping occur, when the atmosphere is unstable?
a) During stability
b) During inversion
c) During subadiabatic conditions
d) During superadiabatic conditions
View Answer

Answer: d
Explanation: Looping is a condition of plume dispersion when the atmosphere is unstable. It happens when the atmosphere is in superadiabatic condition. Here, the environmental lapse rate is greater than the dry adiabatic lapse rate.

5. Which plume behaviour does the illustrated temperature profile indicate?

a) Looping
b) Coning
c) Lofting
d) Trapping
View Answer

Answer: a
Explanation: The illustrated altitude versus temperature plot indicates the plot of looping. As shown, the environmental lapse rate (dotted line) is greater than the dry adiabatic lapse rate (solid line). This is the case for the superadiabatic lapse rate.

6. In which case of turbulence does the looping of air pollutant plume occur?
a) Biological
b) Physical
c) Mechanical
d) Thermal
View Answer

Answer: d
Explanation: Looping occurs in the case of thermal turbulence on hot sunny days. The thermal eddies carry the plume towards the ground and then upwards. The wind speeds range from moderate to high.

7. Fanning is a preferred method of air pollutant dispersion for tall stacks.
a) False
b) True
View Answer

Answer: b
Explanation: Fanning is a preferred plume dispersal method for tall stacks. It is because the plume moves parallel to the ground and does not contribute to ground-level pollution, which is desirable.
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8. The altitude-temperature plot represent which of the following plume behaviour behaviours?

a) Trapping
b) Fumigation
c) Fanning
d) Looping
View Answer

Answer: c
Explanation: In the case of fanning, the atmosphere is stable. The plot shows that temperature increases with altitude, which is the condition of inversion. Here, the plume undergoes horizontal mixing and no vertical mixing.

9. Which kind of mixing occurs in the case of fanning type of plume behaviour?
a) Diagonal mixing
b) Vertical mixing
c) Horizontal mixing
d) Both horizontal and vertical mixing
View Answer

Answer: c
Explanation: Fanning is a type of plume behaviour when the atmosphere is stable in cases of inversion. For a stable atmosphere, there is no vertical mixing. The plume, then, experiences horizontal mixing.
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10. Under which condition does the fanning plume behaviour occur?
a) Unstable
b) Inversion
c) Superadiabatic
d) Subadiabatic
View Answer

Answer: b
Explanation: Both superadiabatic and subadiabatic conditions form unstable atmospheric conditions. Fanning occurs during an inversion, when the temperature increases with altitude. This is a stable atmospheric condition.

11. Which plume behaviour condition is illustrated in the diagram?

a) Fanning
b) Lofting
c) Fumigation
d) Coning
View Answer

Answer: d
Explanation: The phenomenon represented in the diagram is coning. In this case, the environmental lapse rate is between dry and moist adiabatic lapse rate. Therefore, the atmosphere is neutral and stable.

12. Fanning is associated with which of the following wind speeds?
a) Very light speeds
b) Moderated speeds
c) Very high speeds
d) High speeds
View Answer

Answer: a
Explanation: Fanning is associated with very light speeds of winds. The winds move parallel to the ground, when the atmosphere is very stable. In stable atmospheres, the plume is visible upto a distance of 20 km from the stack.

13. Which of the following temperature profiles represents coning?
a)

b)

c)

d)

View Answer

Answer: a
Explanation: Coning is represented as the below figure.

Here the environmental lapse rate lies between dry and wet adiabatic lapse rates. The atmosphere is neutral and stable. The plume is symmetrical about the plume line.

14. In which two kinds of plume behaviour do the air pollutants reach the ground-level?
a) Fanning and Trapping
b) Looping and coning
c) Looping and fanning
d) Fanning and coning
View Answer

Answer: b
Explanation: Among the given options, fanning plume moves parallel to the ground and does not reach the ground. Trapping plume behaviour occurs when the plume is trapped between two inversion layers, so it does not reach the surface. Only looping and coning plumes reach the ground-level.

15. Coning is associated with which kind of wind speeds?
a) Low to moderate speeds
b) Low speeds
c) Moderate to high speeds
d) Moderate speeds
View Answer

Answer: c
Explanation: Coning is a plume behaviour when the atmosphere is neutral and the plume disperses in the form of a cone. The wind speeds associated with this type of plume dispersion range between moderate to high speeds. Looping occurs with low to moderate wind speeds.

Sanfoundry Global Education & Learning Series – Air Pollution Control.

To practice all areas of Air Pollution Control, here is complete set of 1000+ Multiple Choice Questions and Answers.

If you find a mistake in question / option / answer, kindly take a screenshot and email to [email protected]

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Manish Bhojasia - Founder & CTO at Sanfoundry
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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