This set of Pollution Control Multiple Choice Questions & Answers (MCQs) focuses on “Sources and Classification of Air Pollutants”.
1. Which of the following is an example of natural air contaminants?
a) Carbon dioxide
b) Oxygen
c) Dust
d) Pollen grains
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Explanation: Pollen grains fall into the category of natural air contaminants. Other such contaminants are particulate matter and gases released from volcanic eruptions, airborne microorganisms, and fog, et cetera.
2. Which of the following given options is not an aerosol?
a) Fumes
b) Smoke
c) Mercaptans
d) Dust
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Explanation: Aerosols or particulates are solid or liquid particles that get airborne. Mercaptans are sulphur-containing gases, and hence, not aerosols. However, sulphurous gases may convert to aerosols in the atmosphere.
3. Which of the following is NOT gaseous or vaporous contaminant?
a) Hydrogen sulphide
b) Aerosols
c) Ammonia
d) Hydrogen sulphide
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Explanation: Aerosols are tiny solid or liquid particles suspended in the air. The other listed options, like hydrogen sulphide, ammonia, and hydrogen sulphide, are gaseous compounds, which aerosols are not.
4. What is the residence time of methane?
a) Between 4 to 7 years
b) 3 years
c) 5 years
d) 8 years
View Answer
Explanation: Residence time or retention time is the time duration for which a gas remains in the atmosphere. Its value varies for different gases. For methane, the residence time is between 4 to 7 years.
5. What are aerosols?
a) Gas particles
b) A colloidal system
c) Solid particles
d) Liquid particles
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Explanation: Aerosols can be both solid or liquid in nature. These particles can get dispersed in air, which gives them the name aerosols. For this reason, aerosols are sometimes called as colloidal systems.
6. What is the range of diameters for fine aerosols?
a) 1 micron to 100 microns
b) 0.1 microns to 100 microns
c) 0.01 microns to 100 microns
d) 0.1 micron to 150 microns
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Explanation: Generally, for particulates to be characterised as fine aerosols, they need to have diameters between 0.01 microns (or less) to 100 microns. Beyond 100 microns, the particulates then classified into coarse aerosols.
7. Which of the following is not a source of atmospheric dust?
a) Fuel-burning
b) Biological treatment
c) Crushing
d) Mining
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Explanation: Except for biological treatment, all the given options are sources of dust. Dust is primarily released as a by-product of mining, crushing, and combustion operations. Various industries, like cement manufacture, release dust.
8. In which category do line sources fall?
a) Mobile sources
b) Stationary sources
c) Area sources
d) Point sources
View Answer
Explanation: Line sources of air pollutants are a sub-classification of mobile sources of air pollutants. Line sources of pollutants are those sources of mobile sources which have a defined, unchanging route with respect to time.
9. Which of the following is an example of line sources?
a) Airplanes
b) Ships
c) Cars
d) Railroad vehicles
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Explanation: Mobile sources that have a defined pathway are line sources. Railroad vehicles or trains that follow specific routes, so they fall into this classification. The other options given are all mobile area sources.
10. Which of the following is a mobile area source?
a) Trains on the railways
b) Trucks in the city
c) Trucks on the highway
d) Cars on the highway
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Explanation: Mobile sources that do not have a specific pathway or route are area sources. Trucks in the city are mobile area sources. Unlike on a highway, which is a defined route, trucks are not confined to specific routes in cities.
11. What are area sources of air pollutants?
a) They are stationary sources
b) They are large sources
c) They are small sources
d) They are mobile sources
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Explanation: Area sources can be both mobile and stationary. They are small sources which do not have a ‘definite route.’ This definition implies that such type and amount of emissions vary over time.
12. Which of the following are NOT point sources of air pollution.
a) Residential heating
b) Industrial plants
c) Waste disposal
d) Waste disposal
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Explanation: Point sources are a sub-classification of stationary air pollutant sources. These are stationary sources which are large in nature and their emissions remain fairly constant over time. Among the listed options, only residential heating does not fall into this category.
13. Which of the following is an example of stationary point sources?
a) Domestic heating
b) Trucks on the highway
c) Waste disposal
d) Cars in the city
View Answer
Explanation: Waste disposal is an example of stationary point sources. Domestic heating is an example of a stationary area source, trucks on a highway are a mobile line source, and cars in a city are an example of a mobile point source.
14. Air pollutants are not classified based on natural and anthropogenic sources.
a) True
b) False
View Answer
Explanation: One way of classifying air pollutants is by their emission sources. Emission sources are natural sources (ex. volcanic eruptions), or anthropogenic sources (ex. combustions). Several other ways of classification also exist.
15. Which of the following is a classification of air pollutants based on their state?
a) Particulates and aerosols
b) Gases and dust
c) Gases and vapours
d) Particulate matter and gases
View Answer
Explanation: Air pollutants are classified into particulate matter and gases based on their state. Particulates and aerosols do not cover gases, so the option is incorrect. Dust is an example of particulate matter.
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