Lesson: Pollution of Air and Water
Topic 1: Air Pollution

# Question: 1

What is air pollution?

## Solution:

The presence of contaminants and substances harmful to both the living and the environment is known as air pollution and the substances which are responsible for air pollution are called air pollutants.

# Question: 2

What are the sources of air pollution?

## Solution:

Sources of air pollution include:

CFCs emitted from air conditioners, old refrigerators and aerosol sprays.

Harmful gases like sulphur dioxide and nitrogen dioxide emitted from factories and vehicles.

Harmful gases like carbon monoxide released from vehicle exhausts due to unburnt petrol and diesel.

Fly ash released by burning wood is also a major contributor along smoke and dust from volcanoes and forest fires.

# Question: 3

What is smog? Why is it harmful?

## Solution:

Smog is thick fog-like layer that forms in the atmosphere, especially during winters. It is a mix of smoke and fog with some harmful chemicals. Smog triggers breathing difficulties such as asthma, cough and wheezing in children.

# Question: 4

What is acid rain?

## Solution:

Emissions of sulphur dioxide and nitrogen oxide from factories and vehicles react with water molecules in the atmosphere, forming dilute solutions of sulphuric acid and nitric acid. When it rains, these acids fall on earth in the form of acid rain.

# Question: 5

How is the Taj Mahal affected by air pollution?

## Solution:

Harmful gases emitted by the nearby oil refineries react with the Taj Mahal’s white marble and give it a yellowish tinge. These harmful gases also give rise to acid rain, which further corrodes the marble.

# Question: 6

What is Van Mahotsav?

## Solution:

Van Mahotsav is celebrated in the first week of July. It is an annual tree-planting festival to promote afforestation.

# Question: 7

Write the full forms of the following:

a)      CFC

b)      CNG

c)      LPG

d)      WWF

## Solution:

a)      Chlorofluorocarbons

b)      Compressed Natural Gas

c)      Liquefied Petroleum Gas

d)      World Wide Fund for Nature.

# Question: 8

What causes acid rain and what are its effects?

## Solution:

Smoke from factories and motor vehicles contain poisonous oxides of sulphur and nitrogen.  These gases mix with water vapour in the atmosphere and form dilute acids and come down in the form of acid rain.

Effects of acid rain are:

·         It damages crops and vegetation due to acidification of soil.

·         It corrodes buildings and structures.

·         Leaching of rocks and soil, whereby the acid neutralises vital salts in the soil.

·         It increases the acidity level of water bodies and adversely affects aquatic life.

# Question: 9

What steps has the Supreme Court ordered to save the Taj Mahal from air pollution?

## Solution:

The following steps have been ordered by the Supreme court of India to save the Taj Mahal from the effects of pollution:

Neighbouring factories must switch to cleaner fuels like CNG (Compressed Natural Gas) and LPG (Liquefied Petroleum Gas).

Only electric automobiles are permitted in the Taj zone.

Vehicles within 500 metres of the monument have been banned.

# Question: 10

Suggest some ways by which we can help reduce air pollution?

## Solution:

We can help reduce air pollution by:

Planting trees, as they reduce air pollution by absorbing carbon dioxide during photosynthesis.

Using public transportation and encouraging car-pooling.

Travel by foot or bicycle over short distances, instead of going in a vehicle.

Saying no to fire crackers, which will minimize air as well as noise pollution.

Not burning garbage and dry leaves. This releases carbon dioxide in the air, which adds to global warming.

# Question: 11

Explain the greenhouse effect.

## Solution:

The greenhouse effect is caused by greenhouse gases. Examples of greenhouse gases are carbon dioxide, methane and water vapour. When solar radiation reaches the earth, some of this radiation is absorbed and a part is reflected back to the atmosphere. Greenhouse gases present in the atmosphere traps a part of the reflected radiation, preventing it from escaping the earth’s atmosphere and warming it up. This helps keep the earth warm for human survival. However, an excess of greenhouse gases leads to further trapping of the sun’s radiation, which adversely increases the earth’s temperature, causing global warming. This phenomenon is known as the greenhouse effect.

Topic 2: Water Pollution

# Question: 1

What is potable water?

## Solution:

Water which is safe for human consumption is called potable water.

# Question: 2

Why do we say that the river Ganges is dead at many places?

## Solution:

This phrase is mostly used to describe stretches of the river where pollution levels are so high that the river is devoid of any aquatic life.

# Question: 3

List some methods by which water can be made safe for drinking.

## Solution:

Methods by which water can be made safe for drinking include:

$•$        Using candle-type filters

$•$        Boiling

$•$        Adding chlorine tablets or bleaching powder

$•$        Reverse osmosis

# Question: 4

Define water pollution? Give two examples of water pollutants.

## Solution:

Water pollution is the contamination of water by harmful substances. It occurs when harmful substances or pollutants are discharged into water bodies. Two common water pollutants are sewage and agricultural waste.

# Question: 5

What are the different ways by which water can get contaminated?

## Solution:

Water gets contaminated by the addition of:

a)      Agricultural run-offs: Farmers use excessive amounts of pesticides and fertilisers to increase crop production. These chemicals get washed into the water bodies due to rains and floods, which lead to water pollution.

b)      Industrial waste: Industries release harmful chemical wastes into water sources, thereby polluting them.

c)      Sewage waste: Waste materials from kitchens, toilets and laundry sources are also responsible for contaminating water.

d)      Plastics and detergents: Throwing of plastics, bathing and washing clothes near water bodies contaminate water.

# Question: 6

Analyse the statement ‘Clear, transparent water is always fit for drinking’.

## Solution:

No, clarity and transparency are not the only parameters through which we judge water for its fitness to drink. Water might appear clean, but unless purified, it may contain disease-causing microorganisms and several other dissolved impurities. Hence, it is advised to always purify water before drinking it. Purification can be done by different filtration techniques or by boiling the water.

# Question: 7

What are the measures you would want your municipal body to undertake to supply clean drinking water?

## Solution:

To ensure the supply of clean water to all residents the following steps must be taken:

a)      The main water source must be built in clean surroundings and should be maintained properly.

b)      Chemical methods such as chlorination must be used for purifying water.

c)      The area around water pipes should also be clean.

# Question: 8

State ways in which aquatic organisms are killed due to air and water pollution.

## Solution:

Smoke from industries and vehicles containing oxides of sulphur and nitrogen rise up and mix with atmospheric water vapour. They form acids and come down as acid rain. Acid rain alters the acidity level of water bodies and in the long run and kills fish and other aquatic organisms.

Discharging industrial effluents, agricultural run-offs and bathing and washing clothes in water bodies result in contamination of water bodies with chemical effluents and physical impurities. These harmful effluents alter the acidity level of water that give rise to the growth of algae and also reduce the oxygen content of water resulting in the death of aquatic organisms.