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pollution of air and water Class 8 Notes - Chapter 18



Table of Contents

Meaning of pollution

Air pollution
Pollution of Air
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  • Pollution can be defined as the undesirable substances that are present in the air, water, and land that make them dirty. Pollution is the introduction of dangerous or poisonous substances into the environment, which can have negative consequences.
  • Pollution causes an imbalance in the environment. We ourselves are responsible for causing this pollution.
  • These undesirable substances that cause pollution are called pollutants. There are many causes of pollution, such as-population explosion, deforestation, burning of fuels specially fossil fuel, industrial emissions etc.
  • The Taj Mahal in Agra is affected by the pollution of the air. The white marble turns yellowish due to fumes emitted from the Mathura Refinery.

What is Air Pollution?

  • Air is a mixture of many gases in various amounts. It is made up of gases such as nitrogen (78%), oxygen (21%), carbon dioxide (4%), argon (0.93%), and water vapour (0.4 percent ). It also contains trace amounts of methane, ozone, and other gases.
  • When air is contaminated by unwanted substances which have a harmful effect on both living and non-living components, it is referred to as air pollution.
  • Air pollution can be defined as the presence of an undesirable substance present in the air which adversely affects the environment.
  • The unwanted substances which cause air pollution are called pollutants.
  • Air pollutants include the emission of harmful gases, dust, smoke, and fumes. These pollutants make the air unclean.
  • CFCS-CHLOROFLUOROCARBONS:- These are used in refrigerators, air conditioners, and aerosol sprays. CFCS damages the ozone layer of the atmosphere. The function of the ozone layer is to protect us from ultraviolet rays of the sun.

How does air get polluted ?

Increase in urbanization and industrialization

  • Due to the population explosion, the demand for land has also increased, which has led to the cutting down of trees. The cutting down of trees and forests changes the composition of the air.
  • The industries release air pollutants like carbon dioxide, sulphur dioxide, foul odour, fumes, smoke and dust.
  • Nitrogen dioxide and sulphur dioxide are the principal pollutants. Acid rain is caused by these pollutants in the Agra region.
  • Nitrogen dioxide reacts with water to generate nitric acid, and sulphur dioxide reacts with water to form sulphuric acid.

Acid Rain

  • Acid rain can cause damage to forests, soil resources, and even human death. When acid rain falls on leaves, they lose nutrients present in them.
  • Acid rain is a threat to living and non-living things both. The corrosion of buildings, monuments, and statues is caused by acid rain.
  • The combustion of fossil fuels such as coal and oil in automobiles emits gases into the atmosphere such as carbon dioxide, sulphur dioxide, and nitrogen oxide.
  • In clouds, these gases react with water vapour to form sulphuric acid, carbonic acid, and nitric acid.
  • The rain that falls as a result of such cloud precipitation is highly acidic and is thus referred to as acid rain.
  • The monuments made of marble are corroded by acid rain. Marble Cancer is another name for this phenomenon.

Why has the Taj Mahal located in Agra become a matter of concern?

  • Its marble has become discoloured as a result of pollution in the air. The yellowing of the marble has been exacerbated by suspended particulate matter, such as soot particles released by the Mathura oil refinery.
  • The Mathura oil refinery, as well as other businesses like as autos, rubber manufacturing, and chemicals, emit toxic compounds into the atmosphere are some of the major pollutants and their emission must be checked.
  • Several attempts have been taken by the Supreme Court to save the Taj. The government has directed enterprises to use greener fuels such as CNG and LPG.

Greenhouse effect

  • It is the atmosphere's action that allows heat in, but also prevents a part of it from returning to space.
  • Greenhouse gases are the gases that cause the greenhouse effect, such as carbon dioxide, water vapour, methane, nitrous oxide, and CFCs.
  • Life on Earth would not have been feasible without this mechanism. However, it is now a hazard to life.
  • One of the gases responsible for the greenhouse effect is an excess of carbon dioxide in the atmosphere.

What is Global Warming?

  • Increasing levels of greenhouse gases like carbon dioxide lead to global warming.
  • Carbon dioxide traps heat and does not allow it to escape into space, which results in a gradual increase in the earth's atmosphere.
  • Gradual melting of glaciers such as Gangotri Glacier in the Himalayas is a consequence of global

What can be done to reduce air pollution?

  • Using more and more public transport.
  • Avoid the use of crackers.
  • Using energy-efficient light bulbs and appliances.
  • Use of CNG
  • Using solar energy, hydro, and wind energy instead of fossil fuels might assist a lot.
  • Say no to plastic bags.
  • Turn off the lights when they are not in use.
  • Carpets and furniture are the major causes of indoor air pollution.
  • The Indian government has taken initiatives to combat air pollution. Pollution under control (PUC) certification is given to gasoline-powered vehicles that are tested for carbon monoxide and hydrocarbons.

What is Water Pollution?

Water pollution
Pollution of Water
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  • Water is one of the most important things for living things to live.
  • Water is also required for many daily activities, such as cleaning, washing clothes, bathing, cooking, and so on.
  • As a result of these acts, various contaminants become mixed up in the water, leaving it dangerous for future use.
  • Water pollution is the accumulation of biological, chemical, and physical contaminants in water.
  • In other words, we can say that water pollution is the contamination of water by unwanted and harmful substances.
  • Water pollutants are compounds that contaminate water and render it unfit for human and animal consumption.

Potable water

Water which is purified and fit for drinking is known as potable water.

How water is made safe for drinking?

Water can be made fit for drinking or potable by following the following methods. Physical methods and chemical methods

Physical method – By filtering and boiling the water. The Candle filter is a popular domestic filter. Boiling is a common method for obtaining safe drinking water. Boiling water eliminates bacteria and makes it safe to drink.

Chemical method – By using chlorine tablets. It involves adding chlorine pills or bleaching powder to water to disinfect it. But using more chlorine tablets than recommended is dangerous.

Another way to make water fit for drinking is through water treatment plants. Polluted water should not be dumped straight into rivers and lakes. All industrial regions should have water treatment systems.

Individuals should save water and not waste it. Reducing, reusing, and recycling should be a priority. Water used for washing can be utilised to water plants in the garden, whereas water used for brushing teeth or washing utensils should be turned off. Letting the tap run wastes several litres. Simple, common practices can help save water.

Causes of water pollution

  • Industries discharge their chemical waste into rivers and streams, causing pollution of water.
  • Industrial waste causes toxicity in flora and fauna.
  • Industrial waste affects the soil by causing changes in acidity and the growth of worms.
  • Domestic sewage is also released into water that causes pollution.
  • The use of pesticides and weedicides also results in pollution, as when the rain comes, the sprayed pesticides and weedicides wash off from the crop and reach the river where they cause pollution.

How does water get polluted?

Water can be contaminated by the things given below –

  1. Many industries release dangerous chemicals into rivers and streams, polluting the water. Arsenic, lead, and fluorides are among the substances released into the water, and they are hazardous to plants and animals. The contaminated water also affects the soil, creating changes in pH, worm growth, and other issues.
  2. Weedicides and pesticides contain chemicals that breakdown in water, wash into water bodies, or seep into the ground. These compounds in the water act as fertilisers for algae to grow, and they serve as nutrients for algae. This process consumes a large amount of oxygen, resulting in a drop in oxygen levels.
  3. Untreated sewage containing food wastes, detergents, microorganisms, etc. pollutes water bodies. Contaminated water can cause cholera, typhoid, and jaundice.
  4. Hot water can also pollute. When dumped into rivers by power plants and industries, it can elevate the temperature of the water body, which is harmful to the aquatic organisms, animals and plants that live in it because they are accustomed to a certain temperature of water. A sudden temperature change harms or kills the plants and fauna.

Consequences of water pollution

  • Water pollution results in the destruction of water plants and animals.
  • Water pollution is dangerous for aquatic life and many aquatic organisms face the threat of expansion as a result of it.
  • It leads to food chain destruction.

Ganga River Pollution Case Study

Let us understand this through a case study.

The Ganga is one of the most famous rivers in India. According to a study by WWF, the Ganga is found to be one of the ten most endangered rivers in the world. Pollution levels have been rising for many years. The river becomes polluted as towns and cities throw large quantities of garbage, untreated sewage, dead bodies, and many other harmful things directly into the river.

To save the river, the Ganga Action Plan was launched in 1985. It aimed to reduce pollution levels in the river.

How to prevent water pollution?

  • Domestic sewage water must be treated before being released into rivers.
  • Industrial waste should be chemically treated to remove harmful substances before being dumped into water bodies.
  • Bathing of animals should be restricted.
  • Disposing of human and animal excrement into water should be avoided.

Water conservation

Conservation of water refers to the preservation of water and its resources. Conserving water means using our water supply wisely and being responsible.

The Importance of Water Conservation:-

  • Water conservation is important as it helps to keep water pure and clean.
  • It minimizes the effects of drought and water shortages.

Methods of conserving water

  • The best way to conserve water is through rainwater harvesting.
  • Turning the tap off while not in use.
  • Use of improved faming and irrigation techniques.
  • Preventing the cutting of trees.
  • Reuse of waste water from the kitchen to water the plants in the garden.

Questions and Answers

What is the Ozone Layer?

The earth's atmosphere is surrounded by ozone gas. This ozone gas blocks the sun's harmful ultraviolet rays from reaching the earth's surface. The sun's UV radiation can cause serious difficulties if it reaches the earth's surface. They have the potential to destroy plants, cause cancer in humans, and cause skin and eye disorders. Thus, the ozone layer is vital to the environment.

What is the ozone layer depletion?

The ozone layer is depleting due to hazardous compounds in the environment. CFCs, or chlorofluorocarbons, are the principal contributors in ozone depletion. They combine with ozone to generate molecular oxygen.

What is the difference between clean air and polluted air?

Clean air is made up of a mixture of gases that, by volume, are 78 percent nitrogen, 21 percent oxygen, and trace amounts of argon, methane, ozone, and water vapours. Polluted air, on the other hand, contains undesired elements known as air pollutants that are hazardous to both living and non-living things.

What are harmful substances which cause air pollution?

Air pollutants are compounds that contaminate the air. Major pollutants of air are compounds like oxides of nitrogen, sulphur dioxides etc that collect at large concentrations in the air, posing a threat to all organisms or materials exposed. Such pollutants can sometimes arise from natural sources, such as smoke and dust from forest fires or volcanic eruptions, or from certain human activities.

What is the difference between air pollution and water pollution?

Air pollution is defined as the contamination of air by undesirable elements that are damaging to both living and non-living things. Water pollution is defined as the polluting of water by undesirable and hazardous substances.

What is Oxygen for Animals?

The presence of oxygen in the air is vital for the survival of all species.

What are the major pollutants in the air?

The main pollutants in the air include the toxic chemicals like carbon dioxide, nitrogen oxides, carbon monoxide, methane, and sulphur dioxide.

What Is Environmental Pollution?

Environmental pollution is defined as unwanted changes in the environment that have a negative impact on plants, animals, and other biological and physical components of the ecosystem.

What is a pollutant?

Pollutants are substances that pollute the environment and contributes to pollution

What are the sources of carbon dioxide?

Carbon dioxide emissions are caused by cement manufacture, deforestation, and the combustion of fuels such as gasoline, natural gas, oil, coal, and wood.

How Crucial Is Air and Water?

Both these resources are crucial for existence of humans and other living organisms on Earth. Water plays an important role in life. It provides food for all living organisms including us. Without clean drinking water, people will die within days. Similarly, without clean air, many people would not live long enough to see another day. The quality of air affects everyone’s daily routine.

What is indoor air quality (IAQ)?

Indoor air quality refers to the air inside homes, offices, and other structures. Poor indoor air quality can cause eye discomfort, redness, headaches, and disorientation. It may potentially cause long-term problems like asthma. Many homes and offices use air purifiers to ensure clean air.

How is water purified?

  1. By filtering the water.
  2. Boiling is a common method of obtaining safe drinking water. Boiling water eliminates bacteria and makes it safe to drink.
  3. Chlorination is a typical chemical approach for purifying water by adding chlorine tablets or bleaching powder to the water. But using more chlorine tablets than recommended is dangerous.
  4. Polluted water should not be dumped straight into rivers and lakes. All industrial regions should have water treatment systems.

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