These DAV Class 8 Science Notes and DAV Class 8 Science Chapter 19 Notes – Pollution of Air act as excellent revision resources, particularly in preparation for board exams.
Pollution of Air Class 8 DAV Notes
→ Pollution: A substance present in the environment in a greater proportion than its natural abundance so that it can cause harmful effects is called a pollutant and this phenomenon is known as pollution.
→ Air Pollution: When air is contaminated by unwanted substances which have harmful effects on the living and non-living, it is called air pollution.
→ Air Pollutants: Substances which contaminate air are called air pollutants.
→ Causes of Air Pollution:
- Excessive burning of fossil fuels.
- Smoke from factories and vehicles.
- Use of certain substances like chlorofluorocarbons.
→ Carbon Monoxide: Carbon monoxide is formed by incomplete combustion of fossil fuels.
→ Harmful effects of Carbon Monoxide:
- Carbon monoxide is a highly toxic gas. If it is inhaled, it can result in death of a person.
- A high concentration of carbon monoxide in air affects the growth of plants causing leaf drop.
→ Nitrogen Dioxide: It is produced by combustion of petrol/gasoline in automobiles.
→ Harmful effects of Nitrogen Dioxide:
- High concentration of nitrogen dioxide results in retardation of photosynthetic activity in plants and thus causes retardation of plants.
- It causes respiratory problems in human beings.
→ Smog: A mixture of smoke and fog is called smog. It makes a thick fog like layer in the atmosphere.
→ Harmful effects of smog:
It leads to respiratory diseases; such as bronchitis, asthma, etc.
→ Chlorofluorocarbons (CFCs)
They are normally used as refrigerants, as propellants, solvents and foaming agents.
→ Harmful effects of CFCs:
It can cause depletion of ozone layer by decomposing ozone to oxygen.
→ Acid Rain: Excessive carbon dioxide, smoke and nitrogen dioxide when released in the atmosphere come in contact with water vapours present and this results in the formation of sulphuric acid and nitric acid. The acid falls down with rain, making it acidic. This is called acid rain.
→ Harmful effects of acid rain:
- Acid rain corrodes the marble of a monument. This phenomenon is known as marble cancer.
- Articles made of metals, gold and silver ornaments slowly lose their luster.
- Acid rain washes a number of essential minerals from the soil.
- Acid rain has an adverse effect on aquatic life.
→ Greenhouse: Greenhouse is a glass house in which plants are grown. Because of glass enclosure, the temperature inside the greenhouse increases. The higher temperature facilitates faster growth of plants.
→ Greenhouse Effect: Some gases; like carbon dioxide, methane, water vapours, nitrous oxide and chlorofluorocarbon have the capacity to trap some of the radiations that are reflected from the earth. These gases are called greenhouse gases. The warming effect is known as greenhouse effect.
→ Causes of Greenhouse Effect:
- Burning of fossil fuels release carbon dioxide gas into the atmosphere.
- Increased deforestation causes imbalance in the concentration of carbon dioxide in the atmosphere.
→ Consequences of Greenhouse Effect:
- Global Warming: Due to greenhouse effect, the average temperature of the earth’s atmosphere is gradually increasing. This is called global warming.
→ Effects of global warming:
- Glaciers will melt at a higher rate and this will lead to rise in the sea level; resulting in floods and loss of life.
- Warming of atmosphere often leads to forest fires which have become very common over the years.
→ Measures to check global warming:
- Use of fossil fuels should be minimized.
- Nuclear reactors and hydroelectric plants should be used more for electricity generation.
- Deforestation must be stopped.
- More trees should be planted.
- Use of CFCs must be checked.
→ Methods to Control Air Pollution:
- Use smokeless chulhas, solar cooker and biogas.
- Use unleaded petrol in vehicles.
- Use CNG in automobiles.
- Use of alternative sources of energy; like solar energy, hydropower, wind energy and nuclear energy.
- Sticking to pollution emission norms for automobiles.
- Install tall chimneys with filters in factories away from residential areas.
- Plant more trees.
- Do not dry vegetable wastes.
→ Pollution : Addition of cont3minants in the environment leads to pollution.
→ Air pollutIon : Addition of contaminants in air which becomes harmful for living beings is called air pollution.
→ Ozone Layer : The stratosphere is also called ozone layer because it is composed of ozone.
→ CFCs : Chlorofluorocarbons
→ Fossil Fuels : Fuels which were formed from fossils.