Environmental Issues Out of Syllabus

The correct answer is :

Option A : Eutrophication

Eutrophication is a process where water bodies receive excess nutrients that stimulate excessive plant growth (algae, phytoplankton, and nuisance plants weeds). This enhanced plant growth, often called an algal bloom, reduces dissolved oxygen in the water when dead plant material decomposes and can cause other organisms to die. Nitrates and phosphates are two essential nutrients that can cause eutrophication when they are present in large amounts.

Option A: Amount of dissolved oxygen in the lake will decrease

Explanation : Biochemical Oxygen Demand (BOD) is a measure of the quantity of oxygen used by microorganisms in the decomposition of organic matter. If a lake is contaminated with polluted water that has high BOD, it means there is a lot of organic matter in the water for bacteria to decompose.

During this decomposition process, the bacteria consume oxygen. This leads to a decrease in the amount of dissolved oxygen (DO) in the water. When oxygen levels in the water are depleted, aquatic organisms, especially fish and macroinvertebrates that rely on higher oxygen levels, may die or move to areas with higher oxygen levels. Hence, this form of water pollution can lead to significant changes in the ecosystem.

Deforestation refers to the conversion of forested areas to non-forested areas.

Reforestation is the process of restoring a forest that once existed but was removed.

The Greenhouse effect is responsible for heating the Earth's surface and atmosphere.

Eutrophication is the natural aging of a lake by nutrient enrichment of its water.

Hence, the correct combination is :

A-(II), B-(IV), C-(I), D-(III)

So, the correct answer is Option D.

The correct answer is :

Option B : (A), (B), (D), (E) only

Here's why :

(A) BOD (Biochemical Oxygen Demand) is indeed inversely related to dissolved oxygen. BOD is a measure of the quantity of oxygen used by microorganisms while decomposing organic matter in water. The more organic matter there is (i.e., the higher the BOD), the lower the amount of dissolved oxygen will be.

(B) Low dissolved oxygen levels and high BOD can lead to the loss of aquatic life. When dissolved oxygen levels in water are low, it can create a condition known as hypoxia, which can be harmful or lethal to aquatic organisms.

(C) High BOD does not lead to high dissolved oxygen. As explained above, high BOD usually leads to low levels of dissolved oxygen because the oxygen is consumed in the process of breaking down organic material. So, this statement is false.

(D) Both BOD and dissolved oxygen are indeed indicators of the health of a water body. High levels of BOD and low levels of dissolved oxygen can indicate pollution, often from organic waste.

(E) Both BOD and dissolved oxygen are affected by the amount of organic matter in the water body. The more organic matter there is in the water, the higher the BOD will be and the lower the level of dissolved oxygen will be, due to microbial decomposition of the organic matter.

So, statements (A), (B), (D), and (E) are correct, while statement (C) is incorrect.

The thickness of the ozone in a column of air from the ground to the top of the atmosphere is measured in terms of Dobson units (DU). Noise is measured in decibels.

Electrostatic precipitator is most widely used in thermal power plants.

It can remove over 99 percent particulate matter present in the exhaust from a thermal power plant.

CNG is better fuel than diesel and petrol because

(1) It burns more efficiently than diesel or petrol

(2) It is cheaper

(3) It can not be adulterated

Electrostatic precipitator can remove over 99% particulate matter present in the exhaust from a thermal power plant. Catalytic converters are fitted into automobiles for reducing emission of poisonous gases. STPs are associated with sewage treatment.

CNG is cheaper than petrol and it burns more efficiently unlike petrol or diesel. It also cannot be adulterated like diesel and petrol. The same diesel engine cannot be used in CNG buses for making the cost conversion low.

Scrubber is used by the industries which produce SO₂ as a by product.

The limestone present in slurry of scrubber remove SO₂ from the exhaust.

Electrostatic precipitator is the most effective device to remove 99% of particulate matter, 'even PM 2.5' present in the exhaust.

• (A) Eutrophication: This term refers to the natural aging of a lake by biological enrichment of its water. It is characterized by an increase in nutrients, leading to excessive growth of algae and other aquatic plants.

  • Therefore, (A) Eutrophication matches with (iii) Nutrient enrichment.

• (B) Sanitary landfill: A sanitary landfill is a method of waste disposal where wastes are dumped in a depression or trench, compacted, and covered with dirt daily. It is an engineering method for municipal solid waste disposal.

  • Therefore, (B) Sanitary landfill matches with (iv) Waste disposal.

• (C) Snow blindness: This is an inflammation of the cornea in the human eye caused by a high dose of UV-B radiation, which is particularly strong at high altitudes and over snow-covered areas.

  • Therefore, (C) Snow blindness matches with (i) UV-B radiation.

• (D) Jhum cultivation: Also known as 'slash and burn agriculture', Jhum cultivation is a traditional agricultural practice, especially in the north-eastern states of India, that involves clearing forest land by cutting and burning trees, leading to deforestation.

  • Therefore, (D) Jhum cultivation matches with (ii) Deforestation.

Combining these matches, we get:

• (A) $\rightarrow$ (iii)

• (B) $\rightarrow$ (iv)

• (C) $\rightarrow$ (i)

• (D) $\rightarrow$ (ii)

Comparing this with the given options, Option C correctly represents these matches.

The final answer is $\boxed{\text{Option C}}$