Here below some basic MCQ’s about “Air, water and soil pollution” with answer which is explained in details. Let’s check one by one which is given below.
1. Which of the following is a primary air pollutant?
A) Ozone (O₃)
B) Sulfur dioxide (SO₂)
C) Nitric acid (HNO₃)
D) Peroxyacetyl nitrate (PAN)
Answer: B) Sulfur dioxide (SO₂)
Explanation:
Primary air pollutants are those emitted directly into the atmosphere. Sulfur dioxide (SO₂) is a primary pollutant produced from the burning of fossil fuels. Ozone (O₃) and peroxyacetyl nitrate (PAN) are secondary pollutants, formed by reactions between primary pollutants in the atmosphere. Nitric acid (HNO₃) is also a secondary pollutant formed when nitrogen oxides react with water vapor in the atmosphere.
2. Eutrophication of water bodies is primarily caused by which of the following?
A) Heavy metals
B) Plastic waste
C) Excessive nutrients like nitrates and phosphates
D) Pesticides
Answer: C) Excessive nutrients like nitrates and phosphates
Explanation:
Eutrophication is caused by an excess of nutrients, particularly nitrates and phosphates, entering water bodies. These nutrients promote the rapid growth of algae (algal blooms), which deplete oxygen in the water when they die and decompose, harming aquatic life. Heavy metals and pesticides may cause other forms of pollution but are not the main cause of eutrophication.
3. Which of the following pollutants is responsible for depleting the ozone layer in the stratosphere?
A) Carbon monoxide
B) Chlorofluorocarbons (CFCs)
C) Sulfur dioxide
D) Methane
Answer: B) Chlorofluorocarbons (CFCs)
Explanation:
Chlorofluorocarbons (CFCs) are the major cause of ozone layer depletion. When CFCs reach the stratosphere, they are broken down by ultraviolet (UV) radiation, releasing chlorine atoms. These chlorine atoms catalytically destroy ozone molecules, thinning the ozone layer and allowing more harmful UV radiation to reach the Earth’s surface.
4. Which of the following is not considered a consequence of soil pollution?
A) Loss of soil fertility
B) Bioaccumulation of toxins in the food chain
C) Increased water retention capacity of the soil
D) Harm to soil organisms
Answer: C) Increased water retention capacity of the soil
Explanation:
Soil pollution generally leads to a loss of soil fertility, bioaccumulation of toxins (which can enter the food chain), and harm to beneficial soil organisms like earthworms. It does not improve the soil’s water retention capacity; in fact, pollutants can degrade soil structure and reduce its ability to retain water.
5. Which gas is primarily responsible for acid rain?
A) Oxygen
B) Nitrous oxide
C) Sulfur dioxide (SO₂)
D) Carbon dioxide (CO₂)
Answer: C) Sulfur dioxide (SO₂)
Explanation:
Acid rain is caused by the emission of sulfur dioxide (SO₂) and nitrogen oxides (NOx), which react with water vapor in the atmosphere to form sulfuric acid and nitric acid. These acids fall to the ground as acid rain, harming ecosystems and structures. CO₂, while contributing to global warming, is not directly responsible for acid rain.
6. Which of the following methods is most effective for controlling vehicular air pollution?
A) Installing electrostatic precipitators
B) Using catalytic converters
C) Reforestation
D) Reducing industrial emissions
Answer: B) Using catalytic converters
Explanation:
Catalytic converters are devices fitted to the exhaust systems of vehicles to reduce the emission of harmful gases like carbon monoxide (CO), nitrogen oxides (NOx), and hydrocarbons (HC) by converting them into less harmful substances like carbon dioxide (CO₂), nitrogen (N₂), and water (H₂O). Electrostatic precipitators are used in industries, not vehicles, and reforestation helps reduce CO₂ but does not directly address vehicular pollution.
7. Which of the following water pollutants is most likely to cause biomagnification in food chains?
A) Nitrates
B) Phosphates
C) Heavy metals like mercury
D) Bacteria
Answer: C) Heavy metals like mercury
Explanation:
Biomagnification refers to the increasing concentration of toxins in organisms at higher levels of the food chain. Heavy metals like mercury and cadmium are persistent in the environment and accumulate in the tissues of organisms. As smaller organisms are eaten by larger ones, the concentration of these toxins increases at each trophic level, posing serious health risks.
8. Which of the following is the most effective way to prevent soil erosion?
A) Deforestation
B) Using chemical fertilizers
C) Crop rotation and contour plowing
D) Excessive irrigation
Answer: C) Crop rotation and contour plowing
Explanation:
Crop rotation helps maintain soil fertility and structure, while contour plowing helps prevent soil erosion by following the natural contours of the land, reducing water runoff. Deforestation and excessive irrigation lead to soil degradation, and chemical fertilizers can sometimes contribute to soil pollution rather than preventing erosion.
9. The Greenhouse Effect is primarily caused by which of the following gases?
A) Nitrogen
B) Oxygen
C) Carbon dioxide (CO₂)
D) Helium
Answer: C) Carbon dioxide (CO₂)
Explanation:
The greenhouse effect is caused by greenhouse gases like carbon dioxide (CO₂), methane (CH₄), and water vapor (H₂O), which trap heat in the Earth’s atmosphere, leading to global warming. Nitrogen and oxygen make up the bulk of the atmosphere but do not contribute to the greenhouse effect in a significant way.
10. Which pollutant is responsible for the phenomenon of “Blue Baby Syndrome”?
A) Lead
B) Arsenic
C) Nitrates
D) Mercury
Answer: C) Nitrates
Explanation:
“Blue Baby Syndrome,” or methemoglobinemia, occurs when nitrates in drinking water are converted to nitrites in the body, which interfere with the ability of hemoglobin to carry oxygen in infants. This causes a blue tint to the skin due to lack of oxygen, hence the name.
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