Environmental Issues

Step 1: Understanding photochemical smog.
फोटोकेमिकल स्मॉग सूर्य के प्रकाश की उपस्थिति में नाइट्रोजन ऑक्साइड्स और हाइड्रोकार्बन की अभिक्रिया से बनता है।

Step 2: Key component.
इस स्मॉग का मुख्य तत्व ओजोन (O ) होता है, जो हमेशा उपस्थित रहता है।

Step 3: Conclusion.
अतः सही उत्तर (B) O है।

Step 1: Causes of global warming.
Global warming is caused mainly by human-induced activities such as burning fossil fuels, deforestation, and rapid population growth.
Step 2: Analysis of options.
(A) Use of fossil fuels: Correct cause — Releases CO .
(B) Deforestation: Correct cause — Reduces carbon sinks.
(C) Population explosion: Correct cause — Increases resource use and emissions.
(D) Improvement in the efficiency of energy use: Not a cause — In fact, this helps reduce global warming.
Step 3: Conclusion.
Thus, the option Improvement in efficiency of energy use is not a cause of global warming.

Step 1: Understanding organic farming.
Organic farming is an agricultural method that avoids the use of synthetic chemicals and instead relies on natural processes for soil fertility and pest management.
Step 2: Analyzing the statements.
(A) It is cyclic: Correct — Organic farming follows natural nutrient cycles.
(B) Zero waste is generated: Correct — Waste is recycled back into the system.
(C) Maximum utilization of resources: Correct — Resources are efficiently used in organic farming.
(D) Use of chemical fertilizers: Incorrect — Organic farming strictly avoids chemical fertilizers.
Step 3: Conclusion.
Hence, the incorrect statement is Use of chemical fertilizers.

Step 1: Definition.
Dobson Unit (DU) is a unit used to measure the thickness of the ozone layer in the atmosphere.
Step 2: Explanation.
1 DU corresponds to a 0.01 mm thick layer of pure ozone at standard temperature and pressure (STP).
Step 3: Normal values.
Average ozone concentration is about 300 DU. Values below 220 DU indicate an ozone hole.
Step 4: Conclusion.
Dobson unit measures ozone layer thickness and is important for studying ozone depletion.

Groundwater refers to water that is stored beneath the earth's surface in aquifers, which are permeable rock formations that hold water. This water is replenished through precipitation that percolates down into the ground. Step 1: Understanding groundwater.
- Groundwater is an essential part of the hydrological cycle, serving as a major source of fresh water for drinking, irrigation, and industrial purposes. - It is stored in the spaces between soil particles and in cracks in rocks, and is accessed through wells or springs.
Step 2: Causes of groundwater depletion.
Groundwater depletion occurs when the rate of water extraction exceeds the rate of natural replenishment. Some of the key causes are: 1. Over-extraction for agriculture: The excessive use of groundwater for irrigation in regions with little rainfall has led to rapid depletion. 2. Urbanization and industrial use: Growing urban populations and industries rely heavily on groundwater for water supply, often leading to unsustainable usage. 3. Climate change: Changing weather patterns, with decreased rainfall and increased evaporation, reduce the natural replenishment of groundwater supplies. 4. Contamination: Overuse of groundwater can also lead to its contamination from pollutants, further depleting usable reserves.
Step 3: Remedies for groundwater depletion.
To address groundwater depletion, the following measures can be taken: 1. Water conservation: Promoting water-saving techniques such as rainwater harvesting, drip irrigation, and efficient domestic water use can reduce reliance on groundwater. 2. Sustainable extraction practices: Limiting groundwater extraction to levels that allow natural recharge through managed aquifer recharge (MAR) systems. 3. Government regulation: Implementing policies to regulate groundwater usage, ensuring equitable access and sustainable practices for industries and farmers. 4. Reforestation and watershed management: Protecting and restoring natural forests and watersheds can help increase groundwater recharge by improving the infiltration of rainwater.
Final Answer: Groundwater is an important source of fresh water stored below the earth's surface. Its depletion is caused by over-extraction, urbanization, climate change, and contamination. Remedies include water conservation, sustainable extraction, regulations, and watershed management.

Sewage, when not properly treated, can have several harmful effects on the environment and human health. Step 1: Harmful effects of sewage.
1. Water contamination.
Sewage can contaminate water sources with harmful bacteria, viruses, and chemicals, leading to waterborne diseases. 2. Eutrophication.
Nutrients in sewage (such as nitrogen and phosphorus) can promote algae growth in water bodies, leading to eutrophication and oxygen depletion.
Final Answer: 1. Water contamination with pathogens. 2. Eutrophication leading to oxygen depletion.

Step 1: Understand ozone depletion.
The ozone layer is depleted primarily by chlorine and bromine-containing compounds, notably chlorofluorocarbons (CFCs), commonly known as Freon.
Step 2: Review the options.
- SO (Sulfur dioxide) contributes to acid rain but is not directly involved in ozone layer depletion.
- CO (Carbon dioxide) contributes to global warming but does not affect the ozone layer significantly.
- Freon (CFCs) is the most harmful as it releases chlorine atoms, which break down ozone molecules.
- "All of these" is incorrect as only Freon is a significant ozone-depleting substance.
Step 3: Conclude.
Freon is the most harmful to the ozone layer, making option (C) the correct answer.
Final Answer:

Step 1: Understand SO pollution.
Sulfur dioxide (SO ) pollution primarily affects the cellular components involved in energy production.
Step 2: Review the options.
- The nucleus is responsible for genetic material and is not directly impacted by SO pollution.
- Mitochondria are responsible for energy production in the cell and are highly sensitive to SO pollution.
- Chloroplasts are involved in photosynthesis, but they are not as directly affected by SO pollution as mitochondria.
- Golgi bodies are involved in the modification and packaging of proteins, but they are not as affected by SO pollution.
Step 3: Conclude.
SO pollution affects mitochondria, making option (B) the correct answer.
Final Answer: