All questions of Pollution for UPSC CSE Exam

Understanding Greenhouse Gases
Greenhouse gases (GHGs) trap heat in the Earth's atmosphere, contributing to global warming. Among the various GHGs, carbon dioxide (CO2) is the most significant.
Why Carbon Dioxide is the Primary Greenhouse Gas
- Prevalence: CO2 is the most abundant GHG emitted by human activities, primarily from burning fossil fuels (coal, oil, and natural gas) for energy, transportation, and industrial processes.
- Longevity: Carbon dioxide remains in the atmosphere for a long time—up to thousands of years—allowing it to accumulate and exert a sustained warming effect.
- Impact on Climate: The increased concentration of CO2 enhances the greenhouse effect, leading to higher global temperatures, changing weather patterns, and contributing to extreme weather events.
Comparison with Other Greenhouse Gases
- Methane (CH4): While methane is more potent than CO2 in terms of heat-trapping ability (approximately 25 times more effective over a 100-year period), it is present in smaller quantities. Methane emissions primarily come from agriculture (especially livestock), landfills, and oil and gas extraction.
- Nitrous Oxide (N2O): This gas is less abundant but has a significant warming potential (about 298 times that of CO2 over 100 years). It mainly arises from agricultural fertilizers and industrial processes.
- Ozone (O3): Ground-level ozone is a secondary pollutant formed by chemical reactions between volatile organic compounds (VOCs) and nitrogen oxides in the presence of sunlight. While it has warming effects, it is not emitted directly.
Conclusion
Carbon dioxide's high volume of emissions, long atmospheric lifespan, and significant impact on climate change make it the primary greenhouse gas responsible for global warming. Addressing CO2 emissions is crucial in combating climate change.

Point source pollution refers to the release of pollutants from a single, identifiable source, such as a pipe, chimney, or drain. It is called "point source" because the pollution can be traced back to a specific point of origin. Among the given options, the discharge from a factory piped is the best example of point source pollution. Let's explore this answer in detail.

Definition of Point Source Pollution:
Point source pollution refers to the contamination of the environment through the discharge of pollutants from a single, identifiable source. These sources typically have a distinct point of origin, such as an industrial facility, wastewater treatment plant, or power plant. The pollutants are discharged directly into a body of water, land, or air through pipes, drains, or chimneys.

Explanation of the Example:
The discharge from a factory piped is a classic example of point source pollution. Here's why:

1. Identifiable Source:
In this case, the factory serves as the identifiable source of pollution. The pollutants are released from the factory through a specific pipe or drainage system. This makes it easy to identify the source of pollution.

2. Direct Release:
The pollutants are directly discharged into a body of water or land through the factory's pipe system. The discharge is controlled and regulated, allowing for the easy tracking and monitoring of the pollution.

3. Traceability:
Since the factory's discharge is channeled through a specific pipe, it becomes relatively straightforward to trace the pollution back to its source. This traceability is a defining characteristic of point source pollution.

4. Environmental Impact:
The discharge from a factory can contain various pollutants, such as heavy metals, chemicals, or organic waste. These pollutants can have detrimental effects on the environment and surrounding ecosystems, including water pollution, soil contamination, and harm to aquatic life.

Conclusion:
In summary, the discharge from a factory piped is an example of point source pollution because it originates from an identifiable source, is directly released through a specific pipe system, can be easily traced back to the factory, and has a significant environmental impact. It is important to regulate and manage such pollution sources to minimize their adverse effects on the environment.

Understanding Ozone Layer Depletion
The ozone layer, located in the stratosphere, serves as a protective shield, absorbing the majority of the sun's harmful ultraviolet (UV) radiation. However, this layer has been threatened mainly by human-made chemicals, particularly chlorofluorocarbons (CFCs).
What are CFCs?
- CFCs are synthetic compounds used in refrigeration, air conditioning, aerosol propellants, and foam-blowing agents.
- They are stable and non-toxic, making them popular in various industrial applications.
Mechanism of Ozone Depletion
- When CFCs are released into the atmosphere, they eventually reach the stratosphere.
- Ultraviolet radiation breaks down CFC molecules, releasing chlorine atoms.
- A single chlorine atom can destroy thousands of ozone molecules before it is removed from the atmosphere.
Consequences of Ozone Layer Depletion
- Increased UV radiation leads to higher rates of skin cancer, cataracts, and other health issues.
- It also negatively impacts ecosystems, particularly marine life and plant growth.
Comparison with Other Options
- a) Greenhouse gases primarily contribute to climate change, not ozone depletion.
- c) Volatile organic compounds (VOCs) can affect air quality but are not the main cause of ozone layer depletion.
- d) Carbon monoxide emissions do not directly affect the ozone layer.
In summary, the primary culprit of ozone layer depletion is chlorofluorocarbons (CFCs), making option 'B' the correct answer. Addressing CFC use is crucial for ozone recovery and environmental protection.

Introduction to Greenhouse Gases
Greenhouse gases are components of the atmosphere that trap heat, contributing to the greenhouse effect and global warming. Among these gases, methane (CH4) stands out as a significant contributor released during agricultural activities.
Why Methane is Significant
- Source of Methane:
- Livestock digestion (enteric fermentation) releases methane as part of their digestive process.
- Manure management practices, such as storage and treatment, also produce methane.
- Rice paddies generate methane due to anaerobic decomposition of organic matter in flooded fields.
- Global Warming Potential:
- Methane is approximately 25 times more effective than carbon dioxide in trapping heat over a 100-year period.
- Its potency makes it a crucial focus in climate change mitigation strategies.
Comparison with Other Gases
- Carbon Monoxide:
- Primarily a product of incomplete combustion, not significantly linked to agricultural activities.
- Sulphur Dioxide:
- Mainly produced from burning fossil fuels and has a more direct role in air pollution, rather than agriculture.
- Nitrogen Dioxide:
- Emitted from vehicle exhaust and industrial processes, not a major player in agriculture compared to methane.
Conclusion
Understanding the role of methane in agriculture is essential for developing strategies to reduce greenhouse gas emissions. Addressing methane emissions can significantly contribute to combating climate change and promoting sustainable agricultural practices.