Set 7 | Important Environment Pollution MCQs

Correct Answer is C.

• The combustion of petrol (gasoline) in automobiles can release lead into the air, especially when leaded gasoline is used. Lead is a toxic metal that was historically added to gasoline to improve engine performance. However, due to its harmful effects on human health and the environment, the use of leaded gasoline has been phased out in most countries.
• While carbon dioxide (option D) is also produced during the combustion of petrol, it is not a metal. Mercury (option A) and cadmium (option B) are not typically produced by the combustion of petrol in automobiles.
• Therefore, the correct answer is [C] Lead.

Correct Answer is C.

• The molecular weight of carbon monoxide (CO) is close to that of air, allowing it to blend seamlessly with air in any ratio. This means CO can disperse evenly and remain undetected in the environment. Unlike some gases, carbon monoxide is completely odorless, tasteless, and invisible, making it impossible for humans to detect through their senses.
• When inhaled, CO enters the bloodstream and binds with hemoglobin, the protein in red blood cells responsible for carrying oxygen. This reaction forms carboxyhemoglobin (COHb), which prevents hemoglobin from transporting oxygen to tissues and organs.
• As a result, carbon monoxide exposure can lead to oxygen deprivation in the body, posing serious health risks, including poisoning and even death.

Correct Answer is C.

The non-biotic pollutant in underground water refers to a contaminant that is not derived from living organisms. Among the options provided:

• [A] Bacteria and [D] Viruses are biotic pollutants, as they are microorganisms.
• [B] Algae are also biotic, as they are living photosynthetic organisms.
• [C] Arsenic is a non-biotic pollutant because it is a toxic chemical element that can naturally occur in groundwater or enter it through industrial or agricultural activities.

Thus, arsenic is the correct answer as it is a non-living, chemical pollutant.

Correct Answer is D.

• Water pollution in rivers is often measured by the amount of dissolved oxygen (DO) present in the water. Dissolved oxygen is critical for the survival of aquatic life, as it is necessary for the respiration of fish, invertebrates, and other organisms.
• When water is polluted, especially with organic waste (e.g., sewage or agricultural runoff), the decomposition of this waste consumes oxygen, reducing the DO levels. This can lead to hypoxia (low oxygen levels) or anoxia (complete lack of oxygen), harming aquatic ecosystems.

Other methods of measuring water pollution include:

• Biochemical Oxygen Demand (BOD): The amount of oxygen required by microorganisms to decompose organic matter in water.
• Chemical Oxygen Demand (COD): The amount of oxygen required to oxidize organic and inorganic chemicals in water.

While the amount of chlorine, ozone, or nitrogen dissolved in water can provide additional information about water quality, they are not the primary indicators used to measure river pollution. Dissolved oxygen is the most direct and widely used parameter for assessing the health of aquatic ecosystems.

Correct Answer is D.

The indiscriminate use of fertilizers has led to multiple environmental issues, including:

1. [A] Soil Pollution: Excessive use of fertilizers can alter the chemical composition of the soil, reducing its fertility over time. It can also lead to the accumulation of harmful substances like nitrates and phosphates, which degrade soil quality.
2. [B] Water Pollution: When fertilizers are overused, they can be washed away by rainwater or irrigation into nearby water bodies (e.g., rivers, lakes, and groundwater). This causes eutrophication, a process where excess nutrients (like nitrogen and phosphorus) promote the growth of algae, depleting oxygen levels in the water and harming aquatic life.
3. [C] Air Pollution: Fertilizers, especially nitrogen-based ones, can release gases like ammonia (NH₃) and nitrous oxide (N₂O) into the atmosphere. Nitrous oxide is a potent greenhouse gas that contributes to global warming and climate change.

Thus, the indiscriminate use of fertilizers impacts all three—soil, water, and air—making [D] All of the above the correct answer.

Correct Answer is A.

• The industrial sector that contributes the most to chemical pollution through its effluents is the leather industry. This industry is a major source of environmental degradation, particularly in terms of water and soil pollution.
• During the leather production process, various toxic chemicals are used, such as chromium salts, sulfides, and tannins, which are often discharged as untreated or poorly treated effluents. These harmful substances contaminate nearby water bodies, making the water unsafe for drinking, irrigation, and aquatic life.
• Additionally, the chemicals seep into the soil, reducing its fertility and disrupting ecosystems. The leather industry’s pollution is a significant environmental concern, as it affects both human health and biodiversity.

Correct Answer is D.

Acid rain is primarily caused by air pollution from nitrous oxide (NOₓ) and sulphur dioxide (SO₂). These gases are released into the atmosphere through human activities such as burning fossil fuels (e.g., coal, oil, and natural gas), industrial processes, and vehicle emissions. When these gases react with water, oxygen, and other chemicals in the atmosphere, they form nitric acid (HNO₃) and sulphuric acid (H₂SO₄), which fall to the ground as acid rain.

• Carbon dioxide (CO₂) and methane (CH₄) are greenhouse gases that contribute to global warming and climate change but do not directly cause acid rain.
• Carbon monoxide (CO) is a toxic gas but does not play a significant role in the formation of acid rain.

Thus, the primary contributors to acid rain are nitrous oxide and sulphur dioxide, making [D] the correct answer.

Correct Answer is C.

Acid rain is primarily caused by the release of nitrous oxide (NOₓ) and sulphur dioxide (SO₂) into the atmosphere. These pollutants are emitted from human activities such as burning fossil fuels (e.g., coal, oil, and natural gas), industrial processes, and vehicle emissions. When these gases react with water, oxygen, and other chemicals in the atmosphere, they form nitric acid (HNO₃) and sulphuric acid (H₂SO₄), which fall to the ground as acid rain.

• [A] Carbon dioxide and Nitrogen: Carbon dioxide contributes to global warming but does not directly cause acid rain. Nitrogen in its natural form (N₂) is inert and does not contribute to acid rain.
• [B] Carbon monoxide and Carbon dioxide: Carbon monoxide is a toxic gas but does not play a role in acid rain formation. Carbon dioxide, while contributing to climate change, is not a primary cause of acid rain.
• [D] Ozone and Carbon dioxide: Ozone is a secondary pollutant that forms in the lower atmosphere and contributes to smog but does not cause acid rain. Carbon dioxide, as mentioned, is not a direct cause of acid rain.

Thus, the pollutants responsible for acid rain are nitrous oxide and sulphur dioxide, making [C] the correct answer.

Correct Answer is B.

Acid rain occurs when rainwater and snow become contaminated by specific pollutants, primarily sulphur dioxide (SO₂) and nitrogen oxides (NOₓ). These pollutants are released into the atmosphere through human activities such as burning fossil fuels (e.g., coal, oil, and natural gas), industrial processes, and vehicle emissions. When these gases react with water, oxygen, and other chemicals in the atmosphere, they form sulphuric acid (H₂SO₄) and nitric acid (HNO₃), which fall to the ground as acid rain.

• Sulphur dioxide (1) and nitrogen oxide (2) are the primary contributors to acid rain.
• Carbon dioxide (3) and methane (4) are greenhouse gases that contribute to global warming and climate change but do not directly cause acid rain.

Thus, the correct pollutants responsible for acid rain are 1 and 2 only, making [B] the correct answer.

Correct Answer is C.

Acid rain occurs due to the reaction between sulphur dioxide (SO₂) and nitrogen oxides (NOₓ) pollutants with water vapour, oxygen, and other chemicals in the atmosphere. These pollutants are released into the air primarily from burning fossil fuels (e.g., coal, oil, and natural gas), industrial processes, and vehicle emissions. When sulphur dioxide and nitrogen oxides react with water and oxygen in the atmosphere, they form sulphuric acid (H₂SO₄) and nitric acid (HNO₃), which then fall to the ground as acid rain.

• [A] Acid vapour reaching the clouds: This is not accurate, as acid rain is not caused by acid vapour but by chemical reactions involving pollutants.
• [B] Reaction between rainwater and carbon dioxide pollutants: Carbon dioxide (CO₂) contributes to the formation of weak carbonic acid in rainwater, but this is not the primary cause of acid rain.
• [D] Reaction between water vapour and electric ions during lightning and cloud burst: This describes natural processes like lightning but is unrelated to acid rain.

Thus, the correct explanation is [C] reaction between clouds and sulphur dioxide pollutants, as sulphur dioxide is a key contributor to acid rain formation.