Olympiad Test: Pollution Of Air And Water - 1 - Class 8 MCQ

Causes of Water Pollution:
There are several factors that contribute to water pollution, including:
Sewage:
- Sewage is the wastewater generated from homes, businesses, and industries.
- It contains a variety of contaminants, including bacteria, viruses, chemicals, and debris.
- When sewage is not properly treated before being released into water bodies, it can contaminate the water and pose a threat to aquatic life and human health.
Industrial Waste:
- Industrial activities produce a significant amount of waste, including chemicals, heavy metals, and other pollutants.
- If these wastes are not adequately managed and treated, they can find their way into water bodies and cause pollution.
- Industrial wastewater can contain harmful substances that can harm aquatic ecosystems and contaminate drinking water sources.
Fertilizers and Pesticides:
- The use of fertilizers and pesticides in agriculture is another significant source of water pollution.
- When these chemicals are applied to crops or gardens, they can be washed away by rainfall or irrigation and enter nearby water bodies.
- Excessive amounts of fertilizers can lead to eutrophication, which causes the overgrowth of algae and depletes the oxygen levels in water, negatively impacting aquatic life.
All of these:
- Water pollution is a complex issue that is influenced by various sources and factors.
- Sewage, industrial waste, and the use of fertilizers and pesticides are all significant contributors to water pollution.
- These pollutants can have detrimental effects on aquatic ecosystems, wildlife, and human health.
- Therefore, it is crucial to address and mitigate all these causes to reduce water pollution and protect our water resources.
In conclusion, water pollution is caused by a combination of factors, including sewage, industrial waste, and the use of fertilizers and pesticides. These pollutants can have severe consequences on the environment and human well-being. It is essential to implement proper waste management practices, improve wastewater treatment systems, and promote sustainable agricultural practices to prevent and reduce water pollution.

Conservation of Water

Conservation of water refers to the practice of using water efficiently and preventing it from getting polluted. It involves adopting various measures to reduce water consumption and protect water sources.

Benefits of water conservation:

• Preserves water resources for future generations


• Reduces water scarcity and ensures sustainable water supply


• Helps in saving energy and reducing water treatment costs


• Prevents pollution of water bodies


• Protects aquatic ecosystems and biodiversity

Methods of water conservation:

• Fixing leaks and repairing faulty plumbing


• Installing water-efficient fixtures and appliances


• Practicing water-saving habits, such as shorter showers and turning off taps when not in use


• Collecting and reusing rainwater for irrigation or non-potable purposes


• Using water-efficient landscaping techniques


• Implementing water recycling and greywater systems


• Educating and raising awareness about water conservation

Conclusion:
Conservation of water is crucial for ensuring sustainable water resources and protecting the environment. By adopting water-saving practices and preventing water pollution, we can contribute to the conservation efforts and ensure the availability of clean water for future generations.

Causes of Acid Rain:
- Acid rain is caused by air pollutants that react with water vapor in the atmosphere, forming acidic compounds.
- The primary pollutants that contribute to acid rain are sulfur dioxide (SO2) and nitrogen oxides (NOx).
- These pollutants are released into the atmosphere through human activities such as burning fossil fuels and industrial processes.
- Acid rain can also result from natural sources such as volcanic eruptions and decaying vegetation.
Specific Pollutants:
- Sulfur dioxide (SO2): This is a major contributor to acid rain. It is released primarily from burning fossil fuels, especially coal.
- Nitrogen oxides (NOx): These pollutants are released from the combustion of fossil fuels in vehicles and power plants. They are also produced naturally by lightning and microbial processes.
- Carbon dioxide (CO2): While CO2 is a greenhouse gas and contributes to climate change, it is not a direct cause of acid rain.
- Carbon monoxide (CO): This is a colorless, odorless gas that is produced from incomplete combustion of fossil fuels. It is not a direct cause of acid rain.
Conclusion:
- Among the given options, sulfur dioxide (SO2) and nitrogen oxides (NOx) are the pollutants that can cause acid rain.
- Carbon dioxide (CO2) and carbon monoxide (CO) do not directly contribute to acid rain.
- Therefore, option D, nitrogen (N), is the correct answer.

Explanation:
To remove germs from water, various processes can be used. However, one of the processes mentioned in the options is not effective in removing germs. Let's break down each process and determine which one cannot remove germs from water.
1. Boiling: Boiling water is a commonly used method to kill germs and remove them from water. When water is boiled for a certain period of time, the high temperature kills most of the germs present, making the water safe to drink.
2. Filtration through clay pot: Filtration through a clay pot can effectively remove impurities and sediments from water. However, it may not be able to remove all types of germs present in the water. Therefore, this process is not as effective in removing germs compared to other methods.
3. Reverse osmosis: Reverse osmosis is an advanced filtration process that can effectively remove various contaminants, including germs, from water. It uses a semi-permeable membrane to filter out impurities, ensuring safe and clean drinking water.
4. Exposure to UV light: UV light is a powerful germicidal method that can kill bacteria, viruses, and other microorganisms present in water. When water is exposed to UV light, it disrupts their DNA, rendering them inactive and unable to reproduce. This process is highly effective in removing germs from water.
Based on the above explanations, the process that cannot effectively remove germs from water is filtration through a clay pot (option B). While it can remove some impurities, it may not be as effective in eliminating all types of germs. Other processes like boiling, reverse osmosis, and exposure to UV light are more reliable for germ removal.

Chlorofluorocarbons and Ozone Depletion
Chlorofluorocarbons (CFCs) are synthetic chemicals that were widely used in aerosol propellants, refrigerants, and solvents. They have been found to significantly contribute to the depletion of the ozone layer in the Earth's atmosphere.
Ozone Layer
- The ozone layer is a region in the Earth's stratosphere that contains a high concentration of ozone molecules (O3).
- It is responsible for absorbing and filtering out a significant portion of the Sun's ultraviolet (UV) radiation, particularly the most harmful UV-B and UV-C rays.
- This protection is crucial for all life on Earth, as excessive exposure to UV radiation can lead to various health issues, including skin cancer, cataracts, and weakened immune systems.
Chlorofluorocarbons and Ozone Depletion Mechanism
- When CFCs are released into the atmosphere, they are relatively stable and do not break down easily.
- Eventually, these CFCs drift up into the stratosphere, where they are exposed to high-energy UV radiation.
- The UV radiation causes the CFC molecules to break apart, releasing chlorine atoms.
- These chlorine atoms are highly reactive and can participate in chemical reactions that deplete ozone.
- One of the most significant reactions is the destruction of ozone molecules by chlorine atoms, resulting in the overall depletion of the ozone layer.
Consequences of Ozone Depletion
- Increased levels of UV radiation reaching the Earth's surface can have detrimental effects on the environment and human health.
- UV-B radiation can damage DNA and other cellular structures, leading to an increased risk of skin cancer and other health issues.
- UV radiation can also harm marine ecosystems, including phytoplankton, which are vital for the ocean's food chain.
- Additionally, UV radiation can affect the growth and productivity of crops, leading to potential agricultural disruptions.
International Efforts and Regulation
- The consequences of ozone depletion led to international recognition and action to address the issue.
- The Montreal Protocol, an international treaty signed in 1987, aimed to phase out the production and use of ozone-depleting substances, including CFCs.
- The treaty has been successful in reducing the production and consumption of CFCs, resulting in a gradual recovery of the ozone layer.
In conclusion, chlorofluorocarbons (CFCs) damage the ozone layer present in the Earth's atmosphere. The release of CFCs leads to the breakdown of ozone molecules, resulting in ozone depletion. This depletion has significant consequences for human health, ecosystems, and agriculture. International efforts, such as the Montreal Protocol, have played a crucial role in reducing the production and use of CFCs, contributing to the recovery of the ozone layer.

The correct answer is option C, CO.
Here is a detailed explanation:
1. Carbon Monoxide (CO)
- Carbon monoxide is a colorless and odorless gas.
- When inhaled, it binds to hemoglobin in the red blood cells more strongly than oxygen.
- This binding prevents the red blood cells from carrying oxygen to the body's tissues and organs.
- This can lead to a condition called carbon monoxide poisoning, which can be life-threatening.
2. Carbon Dioxide (CO₂)
- Carbon dioxide is a waste product produced by cells during metabolism.
- Although it is transported in the blood, it does not prevent the blood from carrying oxygen.
- In fact, carbon dioxide plays a role in regulating the body's pH balance and is exchanged for oxygen in the lungs during respiration.
3. Nitrogen Dioxide (NO₂)
- Nitrogen dioxide is a toxic gas primarily found in vehicle emissions and industrial processes.
- It can irritate the respiratory system and cause respiratory problems, but it does not directly prevent the blood from carrying oxygen.
4. Nitrate (NO₃)
- Nitrate is a compound that can be found in fertilizers and food.
- While excessive consumption of nitrates can lead to health issues, it does not directly prevent the blood from carrying oxygen.
In conclusion, carbon monoxide (CO) is the gas that combines with the blood and prevents it from carrying oxygen to the body.

Explanation:
The question asks which of the following pollutants is not a pollutant unless present in excess. To answer this question, we need to understand the concept of pollutants and their effects on the environment.
Pollutants are substances that are released into the environment and have harmful effects on living organisms and ecosystems. However, not all pollutants are harmful in all concentrations. Some pollutants may have beneficial effects or be naturally occurring substances that are only harmful when present in excess.
In this question, we are given four options: sulphur dioxide, carbon monoxide, nitrogen dioxide, and carbon dioxide. Let's analyze each option to determine which one is not a pollutant unless present in excess:
- Sulphur dioxide: Sulphur dioxide (SO2) is a pollutant that is released into the atmosphere through various human activities, such as burning fossil fuels. It can contribute to air pollution and have harmful effects on human health and the environment. Therefore, sulphur dioxide is a pollutant regardless of its concentration.
- Carbon monoxide: Carbon monoxide (CO) is a colorless, odorless gas that is produced by the incomplete combustion of fossil fuels. It is a pollutant that can be harmful to humans and animals when present in high concentrations. Therefore, carbon monoxide is a pollutant regardless of its concentration.
- Nitrogen dioxide: Nitrogen dioxide (NO2) is primarily produced by the burning of fossil fuels, such as in vehicles and power plants. It is a pollutant that can contribute to the formation of smog and have harmful effects on human health. Therefore, nitrogen dioxide is a pollutant regardless of its concentration.
- Carbon dioxide: Carbon dioxide (CO2) is a naturally occurring greenhouse gas that is essential for life on Earth. It is produced through natural processes such as respiration and the combustion of fossil fuels. While carbon dioxide is not considered a pollutant in moderate concentrations, it becomes a pollutant when present in excess. Excessive levels of carbon dioxide in the atmosphere contribute to global warming and climate change. Therefore, carbon dioxide is the correct answer as it is not a pollutant unless present in excess.
In conclusion, the correct answer is D: carbon dioxide.

Answer:
The method that does not result in conservation of water is cutting vegetation so that less water is lost by transpiration. Here's a detailed explanation:
Drip Irrigation:
- Drip irrigation is a method where water is delivered directly to the roots of plants, minimizing water loss due to evaporation and runoff.
- This method conserves water by providing it only where it is needed, reducing wastage.
Recycling of Water:
- Recycling of water involves treating and reusing wastewater for various purposes such as irrigation, industrial processes, and even drinking water.
- By recycling water, we reduce the demand for freshwater resources, thus conserving water.
Planting of Trees:
- Planting trees helps in water conservation in several ways.
- Trees absorb water through their roots, reducing runoff and preventing soil erosion.
- They also provide shade, which reduces evaporation from the soil and helps retain moisture.
- Furthermore, trees contribute to the water cycle by releasing water vapor through transpiration.
Cutting Vegetation:
- Cutting vegetation to reduce transpiration may initially seem like a method to conserve water, but it is not an effective long-term solution.
- Vegetation plays a crucial role in maintaining the water cycle and ecosystem balance.
- Cutting vegetation can lead to increased soil erosion, decreased biodiversity, and loss of habitat for various species.
- It may temporarily reduce transpiration, but it disrupts the natural balance of the ecosystem and can have negative consequences on water availability in the long run.
In conclusion, while methods like drip irrigation, recycling of water, and planting trees contribute to water conservation, cutting vegetation to reduce transpiration is not an effective approach and can have detrimental effects on the environment.

Water is renewed continuously in nature through the water cycle.
The water cycle, also known as the hydrological cycle, is the continuous movement of water on, above, and below the Earth's surface. It involves various processes that help in the renewal and distribution of water across the planet. Below are the key points explaining how water is renewed through the water cycle:
1. Evaporation: The process by which water changes from a liquid to a gas (water vapor) and rises into the atmosphere. This occurs when the Sun's heat energy causes water bodies like oceans, lakes, and rivers to vaporize.
2. Condensation: As water vapor rises into the atmosphere, it cools down and condenses into tiny water droplets, forming clouds. This process occurs due to the decrease in temperature at higher altitudes.
3. Precipitation: When the water droplets in the clouds combine and become heavy enough, they fall back to the Earth's surface as precipitation. Precipitation can be in the form of rain, snow, sleet, or hail, depending on the temperature.
4. Runoff: When precipitation reaches the Earth's surface, it either infiltrates into the ground or flows over the land as runoff. Runoff occurs when the ground is saturated or unable to absorb all the water.
5. Groundwater: Some of the infiltrated water seeps deeper into the ground, filling up spaces between rocks and soil particles. This stored water is called groundwater and can be accessed through wells and springs.
6. Transpiration: Plants absorb water from the soil through their roots and release it into the atmosphere through their leaves. This process is known as transpiration and contributes to the water vapor content in the atmosphere.
7. Repeat: The water cycle is a continuous process, where water is constantly evaporating, condensing, and precipitating. This ensures the renewal and distribution of water across different regions, supporting life on Earth.
Overall, the water cycle plays a vital role in maintaining the Earth's water balance and ensuring the availability of freshwater resources for various purposes like drinking, agriculture, and industrial use.

SPM stands for Suspended Particulate Matter.
Here is a detailed solution explaining the answer:
Definition:
- Suspended Particulate Matter (SPM) refers to the solid particles suspended in the air, such as dust, smoke, and soot.
- These particles are small enough to be suspended in the air rather than settling to the ground.
Explanation:
- The correct answer is C: Suspended Particulate Matter.
- Let's go through the options and eliminate the incorrect ones:
A: Suspended Particle Mixture
- While it may seem like a plausible answer, this term is not commonly used or recognized in the context of air pollution or environmental science.
B: Sand Particles Matter
- This option is incorrect because SPM refers to a wide range of solid particles suspended in the air, not just sand particles.
C: Suspended Particulate Matter
- This is the correct answer. SPM specifically refers to the solid particles suspended in the air.
D: None of These
- This option is incorrect because the correct answer is option C.
To summarize, SPM stands for Suspended Particulate Matter, which includes a variety of solid particles suspended in the air like dust, smoke, and soot.