Maharashtra Board Class 8 Science Chapter 8 Pollution PDF Download

8. Pollution

8.1 Various Problems Of Environment

Why these problems in environment may have been arisen?

What should be done to overcome these problems?

Many problems have been arisen on the earth due to human interference in the nature. Industrialization, increasing population, mining, transportation, indiscriminate use of pesticides and fertilizers are causing pollution on the earth. It is affecting human beings.

Pollution: Contamination of natural environment that will be harmful to ecosystems is called as pollution.

Where do you see the pollution around you?

How does the pollution occur?

Pollutants: Factors affecting natural functions of ecosystem and causing harmful effects on abiotic and biotic factors are called as pollutants. Pollutants make the environment poisonous and unhealthy.

Pollutants may be natural or manmade. Natural pollutants are destroyed in due course of time by nature's rule; however, manmade pollutants are not.

If natural materials are pollutants, why do we not perceive their adverse effects during their use? When such materials are referred as pollutants?

Activity: You yourself survey your residential area and identify the polluted locations. Try to identify the pollutant at each polluted location.

Which types of pollutant are observed?

Whether the pollutants are degradable or non-degradable?

Teacher's Note

Pollution is all around us. When a factory releases dirty smoke or a car releases bad gases, that is pollution. We see it in our cities every day.

Exam Trick

Remember: Pollutants = bad things in nature. Just like trash in your home, pollutants are trash in the environment.

Points to Remember

Pollution is when bad things mix with our air, water, and soil.
Pollutants are made by nature or by humans.
Natural pollutants go away by themselves over time.
Manmade pollutants stay in the environment for a long time.
We can see pollution around us in cities and villages.

8.2 Save Me My Children!

8.3 Air Pollution Due To Different Factors

A. Air Pollution

Plot a graph showing the proportion of various gases in earth's atmosphere.

Why is it said that air is homogenous mixture of different gases?

Which different hazardous gases are released through fuel combustion?

Contamination of air by harmful substances like poisonous gases, smoke, particulate matter, microbes, etc. is called as air pollution.

Reasons Of Air Pollution

Which factors are responsible for pollution shown in the following pictures?

Natural Reasons

Volcanic eruption: Solid, gaseous and liquid materials emerge out through eruption. Ex. Hydrogen sulphide, sulphur dioxide, carbon dioxide, ammonium chloride, hydrogen, vapors, dust, etc.

Earthquake: Poisonous gases and water vapors from inside of earth are released into air.

Cyclones and dust storms: Dust, soil, garbage, pollens, microbes are mixed with air.

Forest fires: Forest fires release carbon dioxide, sulphur dioxide, hydrogen sulfide, smoke in air.

Microbes in air: spores of bacteria, fungi are mixed with air

Manmade Reasons

Fuel: Burning of fuel like coal, timber, LPG, kerosene, diesel, petrol releases carbon dioxide, carbon monoxide, nitrogen oxide, sulphur dioxide, lead compounds, etc. are released in air.

Burning of solid waste, agricultural waste, etc. in open space causes air pollution.

Industrialization: Smoke is released in large quantity from various factories. sulphur powder, nitrogen oxide, Cotten seed powder in air.

Atomic energy plants and blasts: Use of elements like uranium, thorium, graphite, plutonium release radiations in air and thus pollution occurs.

What are reasons other than above mentioned responsible for air pollution?

Whether the vehicles with two stroke engine cause more pollution than four stroke engine?

Teacher's Note

Air pollution comes from cars, factories, and burning things. In Delhi, you can see dark smoke in the sky during winter. This is air pollution.

Exam Trick

Remember: Natural pollution = from volcanoes and earthquakes. Manmade pollution = from cars and factories. Manmade is worse because it stays longer.

Points to Remember

Air pollution happens when bad gases and smoke mix with air.
Volcanoes, earthquakes, and forest fires cause natural air pollution.
Cars, buses, and factories cause manmade air pollution.
Manmade pollution is more harmful than natural pollution.
Smoke contains carbon dioxide, carbon monoxide, and other bad gases.

8.4 Air Pollutants: Sources And Effects

Effect Of Air Pollution On Plants And Animals

Plants

Stomata get closed.

Slowing down of rate of photosynthesis.

Growth is retarded. Leaves fall off or become yellow.

Animals

Respiration is adversely affected.

Irritation of eyes.

What is importance of ozone layer?

What are reasons for depletion in ozone layer?

Teacher's Note

Different pollutants cause different diseases. Sulphur dioxide makes your eyes hurt. Carbon monoxide makes it hard to breathe. In Mumbai, people near factories get lung diseases.

Exam Trick

Remember: Each pollutant = each disease. SO\(_2\) = eyes hurt. CO = hard to breathe. Write the pair correctly in exam.

Points to Remember

Sulphur dioxide comes from factories and makes eyes hurt.
Carbon monoxide comes from cars and makes it hard to breathe.
Dust and particulate matter cause lung diseases.
These pollutants harm both plants and animals.
Pesticides are very dangerous poisons for humans.

This is a preview of the first 3 pages. To get the complete book, click below.