21. The major source of indoor air pollution in rural areas is:
A) Burning of fossil fuels
B) Use of biomass for cooking
C) Industrial emissions
D) Photochemical reactions
Answer: B) Use of biomass for cooking
Explanation:
In rural areas, indoor air pollution is primarily caused by the burning of biomass fuels like wood, crop waste, and dung for cooking and heating. This produces harmful pollutants like carbon monoxide, particulate matter, and polycyclic aromatic hydrocarbons (PAHs), which lead to respiratory diseases.
22. Which of the following heavy metals can cause itai-itai disease?
A) Lead
B) Mercury
C) Cadmium
D) Chromium
Answer: C) Cadmium
Explanation:
Itai-itai disease is caused by cadmium poisoning, often due to contamination of water or food sources. It is characterized by severe pain in the bones and joints and kidney failure.
23. Which of the following pollutants causes ozone depletion?
A) Carbon dioxide
B) Nitrous oxide
C) Chlorofluorocarbons (CFCs)
D) Methane
Answer: C) Chlorofluorocarbons (CFCs)
Explanation:
Chlorofluorocarbons (CFCs) release chlorine atoms in the stratosphere when broken down by ultraviolet radiation. These chlorine atoms catalytically destroy ozone molecules, leading to depletion of the ozone layer, which protects the Earth from harmful UV radiation.
24. Which of the following is used in the treatment of sewage?
A) Electrostatic precipitators
B) Anaerobic bacteria
C) Scrubbers
D) Ultraviolet rays
Answer: B) Anaerobic bacteria
Explanation:
Anaerobic bacteria are used in sewage treatment processes, particularly in the breakdown of organic matter in the absence of oxygen. This results in the production of methane and other by-products that can be used for energy.
25. Which method is used to reduce soil erosion in mountainous regions?
A) Strip mining
B) Contour plowing
C) Monocropping
D) Paving
Answer: B) Contour plowing
Explanation:
Contour plowing is a farming practice used in hilly or mountainous regions where plowing follows the natural contours of the land. This reduces runoff and minimizes soil erosion, helping to preserve the soil’s structure and fertility.
26. Which of the following gases is responsible for the greenhouse effect but is not toxic to humans?
A) Carbon monoxide
B) Sulfur dioxide
C) Methane
D) Chlorine
Answer: C) Methane
Explanation:
Methane (CH₄) is a potent greenhouse gas that contributes significantly to global warming. It is not toxic to humans in low concentrations but has a strong impact on climate change due to its heat-trapping abilities.
27. What is the main source of mercury pollution in aquatic ecosystems?
A) Industrial discharge
B) Use of insecticides
C) Sewage disposal
D) Agricultural runoff
Answer: A) Industrial discharge
Explanation:
Mercury pollution in aquatic ecosystems primarily comes from industrial discharges, such as those from coal-burning power plants, mining operations, and manufacturing facilities. Mercury is converted to methylmercury by aquatic organisms and accumulates in fish, leading to serious health risks for animals and humans who consume contaminated seafood.
28. Which of the following air pollutants is a major contributor to acid rain?
A) Methane
B) Sulfur dioxide
C) Carbon monoxide
D) Hydrogen sulfide
Answer: B) Sulfur dioxide
Explanation:
Sulfur dioxide (SO₂), released from the combustion of fossil fuels, reacts with water vapor in the atmosphere to form sulfuric acid, a primary component of acid rain. This leads to soil acidification, damage to aquatic ecosystems, and the erosion of buildings.
29. What is the primary cause of water pollution in developing countries?
A) Acid rain
B) Oil spills
C) Untreated sewage
D) Excessive irrigation
Answer: C) Untreated sewage
Explanation:
In many developing countries, untreated or partially treated sewage is discharged into rivers and lakes, leading to contamination of water bodies with harmful pathogens, organic matter, and chemicals. This leads to health issues like waterborne diseases and affects aquatic ecosystems.
30. Thermal pollution of water bodies is often caused by which of the following?
A) Dumping of plastic waste
B) Runoff of pesticides
C) Discharge of hot water from industries
D) Accumulation of heavy metals
Answer: C) Discharge of hot water from industries
Explanation:
Thermal pollution occurs when industries discharge heated water into natural water bodies, raising the water temperature. This affects aquatic life, as many organisms are sensitive to temperature changes, and reduces the oxygen-carrying capacity of the water.
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