This set of Pollution Control Multiple Choice Questions & Answers (MCQs) focuses on “Behaviour of Air Pollutants”.
1. Which of the following is not a dry removal method of particulates from the atmosphere?
a) Flotation
b) Diffusion
c) Impact on the ground
d) Sedimentation
View Answer
Explanation: All the given options, except for flotation, are methods of natural dry removal of particulates from the atmosphere. Flotation is used in industries to remove solid waste from liquid effluents.
2. Dry removal is one way of removal of particulates from the atmosphere. Which is the other?
a) Solid removal
b) Wet removal
c) Gaseous removal
d) Sedimentation
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Explanation: Wet removal and dry removal are natural methods of elimination of particulates from the atmosphere. The wet removal occurs by way of precipitation, while the dry removal occurs by sedimentation.
3. Which of the following is not a natural method of gaseous pollutant elimination from the atmosphere?
a) Absorption
b) Dry removal
c) Chemical removal
d) Wet removal
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Explanation: Except for dry removal, all the given options are methods to remove gaseous pollutants from the atmosphere. Dry removal involves the settling of the pollutants, which cannot happen in the case of gases.
4. Which of the following is a chemical reaction method of removal of gaseous pollutants?
a) Conversion to nitrates
b) Conversion to acids
c) Conversion to sulphates
d) Conversion to aerosols
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Explanation: Conversion of gaseous pollutants to aerosols is a method to remove gaseous pollutants from the atmosphere. Subsequently, wet or dry methods are used to eliminate aerosols. The other given options are examples of aerosols, which are conversion products of aerosols.
5. Which sinks remove gaseous pollutants by absorption?
a) Ocean and land
b) Ocean and clouds
c) Clouds and land
d) Clouds and trees
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Explanation: Oceans and land surfaces can remove gaseous pollutants from the atmosphere. This process occurs by way of absorption of the pollutants by the ocean. On the land surfaces, trees primarily act as sinks.
6. One of the methods of wet removal of particulates from the atmosphere is by raining-out. Which is the other?
a) Precipitation
b) Wash-out
c) Gravity settling
d) Sedimentation
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Explanation: Rain-out and wash-out are the two methods of removal of particulates and gaseous pollutants from the atmosphere. In the former, the pollutants make the centre of the raindrop. In the latter, the particulates get weighed down by the rain.
7. Which method is the most effective method of removal of pollutants from the atmosphere?
a) Dry removal
b) Chemical removal
c) Wet removal
d) Absorption
View Answer
Explanation: Wet removal is the most efficient method of elimination of pollutants from the atmosphere. This process includes the removal of both particulate matter as well as gaseous pollutants.
8. Which method is most efficient for removing particles smaller than 0.1 microns?
a) Dry removal by the impact on the ground
b) Dry removal by sedimentation
c) Wet removal by washing out
d) Wet removal by rain-out
View Answer
Explanation: Particulates smaller than 10-1 microns are effectively removed from the atmosphere by rain-out, which is a wet mechanism. These particles become the centre of the raindrops, where the water vapour coalesces.
9. Washing out from the atmosphere is the most effective way to remove particulates of which sizes?
a) Particles smaller than 1 micron
b) Particles larger than 1 micron
c) Particles smaller than 2 microns
d) Particles larger than 2 microns
View Answer
Explanation: Particulates larger than 2 microns get washed out from the atmosphere. These particles are too large to be centres of raindrops, and consequently, they cannot be removed by the raining out method.
10. Which gaseous particles get eliminated by the washing out method of precipitation?
a) Sulphur dioxide
b) Carbon dioxide
c) Water vapour
d) Nitrogen dioxide
View Answer
Explanation: Sulphur dioxide molecules are removed by washing out method, a wet method of removal. The gas molecules migrate to the clouds, where they are converted to aerosols and then precipitated as acid rain.
11. Which of the following statements about wet precipitation is not true?
a) Sulphates get removed from the atmosphere by this method
b) Particulates larger than 2 microns are removed by this method
c) Acids are removed by this method
d) Particulates of 0.09 microns are removed by this method
View Answer
Explanation: Sulphates and acid particles get removed by wet removal of pollutants from the atmosphere. Particulates smaller than 10-1 microns are also removed. Large particles, however, are not.
12. Which dry removal method is responsible for the removal of very small particles from the atmosphere?
a) Diffusion
b) Impact on the surface
c) Sedimentation
d) Precipitation
View Answer
Explanation: Very small particles, smaller than 1 micron, are too small to settle on their own. They coagulate in the atmosphere and then settle due to gravity. They coalesce due to Brownian motion.
13. Settling rate of particulates in the atmosphere depends on which factor?
a) Settling velocity
b) Particle size
c) Stoke’s law
d) Density of particle
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Explanation: Settling rate of particles in the atmosphere depends on the settling velocity. Stoke’s law is used to estimate the settling velocity. Particle size and density of particle both affect the settling velocity of a particle.
14. The speed of sedimentation of particulates does not depend on which factor?
a) Particulate density
b) Temperature of atmosphere
c) Atmosphere density
d) Size of the particulate
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Explanation: Except for the temperature, all the given options affect the rate at which the particulate settles. The bigger and denser the particle, the faster it settles. Dependence varies with conditions.
15. Dry removal is responsible for eliminating what per cent of the particles from the atmosphere?
a) 5%
b) 10%
c) 20%
d) 30%
View Answer
Explanation: 20% of all particulates suspended in the atmosphere are removed by the dry settling method. The rest of the 80% get settled on the surface by other means like precipitation and other wet methods.
Sanfoundry Global Education & Learning Series – Pollution Control.
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