Air Pollution Control Questions and Answers – Plume Behaviour and Characteristics – Set 3

This set of Air Pollution Control Multiple Choice Questions & Answers (MCQs) focuses on “Plume Behaviour and Characteristics – Set 3”.

1. Other than the presence of a structure near the stack, which factor affects the plume dispersion?
a) Irregular terrain
b) Height of stack
c) Wind speeds
d) Temperature of atmosphere
View Answer

Answer: a
Explanation: Both irregular terrains, alongside the presence of buildings near stacks, affect the dispersion of the plume. Due to these factors, the displacement of the plume will heavily vary from the standard plume behaviour.

2. If a stack is constructed near a building, what should its height be to ensure characteristic plume dispersion?
a) Equal to the adjacent building
b) 2.5 times the height of the surrounding building
c) It should never be built near a building
d) 10 metres
View Answer

Answer: b
Explanation: If a stack is built adjacent to another building, its height should be about 2.5 times that of the building. This rule ensures that the plume does not get trapped in the wake zone of the building.

3. What happens when the stack height is less than 2.5 times the height of an adjacent building?
a) The pollutants disperse rapidly
b) There is no effect
c) Pollutants remain trapped near the building
d) There is too little information
View Answer

Answer: c
Explanation: The pollutants remain in the wake zone of the building. This is because a cavity exists behind the building, where the air pollutants get trapped. They will be unable to join the mainstream wind currents immediately.

4. What happens to the plume if the stack is situated in a valley?
a) It disperses upwards
b) It disperses rapidly
c) No dispersion occurs
d) Driven to the surface of the earth
View Answer

Answer: d
Explanation: In case of the stack built in a valley, the wind current carries the plume towards the ground. The wind coming from the top of the valley is headed downwards at an angle, and it carries the plume in the same direction.

5. What is known as downwash?
a) When the wind carries pollutant plume towards the ground
b) When water current drives pollutants downstream
c) When water washes away pollutants in the soil
d) When solid waste is washed away by water
View Answer

Answer: a
Explanation: The downwash condition occurs in valleys. This condition occurs when an emission stack is constructed in a valley. The wind is incident in such a way that it carries the plume towards the ground.

6. When can the downwash of the plume be avoided?
a) When the stack height is short
b) When the stack is taller than the valley rim
c) When the wind speeds are low
d) When there is an inversion
View Answer

Answer: b
Explanation: Downwash occurs in a valley, and sometimes in the vicinity of a chimney. The wind currents drive the pollutant plume towards the ground. The stack should be taller than the mouth of the valley to avoid this.

7. Building a stack behind a chimney can also cause downwash of the pollutants.
a) True
b) False
View Answer

Answer: a
Explanation: Air pollutant plumes can also be down-washed if the stack is built near a chimney. When the wind flows towards the stack from the chimney, the plume is pushed towards the surface. This condition is undesirable.

8. What happens to the plume if its velocity is equal to the wind velocity?
a) Plume does not disperse vertically
b) Slow dispersion
c) Downwashing
d) Plume disperses horizontally
View Answer

Answer: c
Explanation: The plume gets down-washed if its velocity is equal or less than that of the wind. When this condition occurs near a plant with tall stacks, the plume may get stuck behind it, instead of dispersing rapidly.

9. How is the behaviour of the plume determined to optimise dispersion?
a) From experience
b) Modelling
c) Calculations
d) Wind tunnel testing
View Answer

Answer: d
Explanation: Understanding plume behaviour is necessary to optimise its dispersion. Aerodynamic disturbances are difficult to estimate, and practical testing at the small scale needs to be done. Wind-tunnel testing is helpful when mapping the behaviour of the plume in a particular area.

10. Why is it crucial to understand plume behaviour?
a) To reduce pollution
b) For pollutant emission
c) To ensure pollutant dispersion
d) For a clean environment
View Answer

Answer: c
Explanation: Plume behaviour needs to be understood to ensure the dispersion of air pollutants. The atmosphere dissipates the air pollutants based on its meteorological characteristics. To benefit from this natural property, an understanding of its mechanics will avoid pollutant buildup.

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]

Subscribe to our Newsletters (Subject-wise). Participate in the Sanfoundry Certification contest to get free Certificate of Merit. Join our social networks below and stay updated with latest contests, videos, internships and jobs!

Youtube | Telegram | LinkedIn | Instagram | Facebook | Twitter | Pinterest
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.

Subscribe to his free Masterclasses at Youtube & discussions at Telegram SanfoundryClasses.