ICSE Class 6 Biology Chapter 9 Pollution and Pollutants

Pollution And Pollutants

Syllabus

Pollution - different kinds, mentioning their causes, effects and prevention.

The need for conservation of all kinds of resources - a few examples of ways in which individuals can practice this in their daily lives (saving energy, fuels, materials, water, avoiding polluting practices).

Collection of magazine/newspaper clippings about pollution/conservation efforts and creating a bulletin board on the same - followed by discussion.

Find out about the Greenhouse Effect (E).

Introduction to Pollution

From the very beginning of human civilization, man has been interfering with the environment to suit his needs.

Human activities have not only damaged the environment but have also degraded the quality of water, air and soil in many ways. For example:

1. Discharging sewage, municipal and industrial wastes, chemicals, etc., into the rivers, lakes and seas.

2. Pesticides and fertilizers used on a large scale by farmers get washed by the rain water into ponds and rivers.

3. Burning of fossil fuels results in the discharge of poisonous gases into the air.

4. High intensity sounds from noisy buses, trucks, cars, loud speakers, music systems, jet planes, etc.

Pollution and Pollutant

Pollution is an addition of any such constituent to air, water or soil, which adversely alters the natural quality of the environment (ecological system). The constituent thus added is called a pollutant.

The pollutants in the environment, can be dispersed, broken down, stored or recycled naturally. As a result, it becomes dangerous to the lives of organisms (including man) in the environment. For example, if we pour a glass of hot water in a river, it would hardly affect the quality of water and the life living in it; but if we continuously drain hot water from a factory into the river, the river water would get warmed to an extent that it would disturb the river organisms and may affect aquatic life. In this example, heat is the pollutant.

Similarly, sewage is another kind of pollutant. In small proportions, sewage can be a good fertilizer; but too much of it can spread infection and create epidemics.

Major Kinds Of Pollution

There are four major kinds of pollution:

1. Air pollution 2. Water pollution

3. Soil pollution 4. Noise pollution

1. Air Pollution

Harmful gases, dust, smoke, etc., released by the factories, motor vehicles, burning of fuels (coal and wood), etc., pollute the air. Harmful pollutants, like sulphur dioxide and the oxides of nitrogen form acids during rain. Such gases do not allow heat of the earth to reflect into the space but sunlight continues to fall on the earth. Due to this, the temperature of the earth is rising. Such effect is called 'Green House Effect' and such gases are causing global warming.

Green House Effect

Green House Effect is the phenomenon in which the earth's atmosphere traps the heat of sunlight reflected from the surface of the earth and prevents it from escaping. The phenomenon is named so because earth's atmosphere acts like a green house made of glass in which sunlight enters through the transparent glass, but the heat is not allowed to escape (Fig. 9.2). As a result of this, the temperature increases inside the green-house and saves the plants from cold. This method is used in extremely cold areas for growing certain plants.

The Green House Effect is also referred to as Global Warming. The green house effect is leading to the progressive gradual warming of the earth's atmosphere, thus, disturbing the whole system in which the earth's climate is being maintained.

You already know that carbon dioxide is produced when fuels (oil, petrol, coal, etc.) are burnt. Plants use this carbon dioxide for preparing their food, and in return they release oxygen which is utilized by animals for respiration. In modern days, the amount of carbon dioxide produced due to human activities is increasing and at the same time, the number of plants is depleting. The plants in the world are thus unable to utilize this increased carbon dioxide. The situation is worsening day by day because many of the forests are being cut down by human beings to get more land for housing and industries.

Thus, more and more carbon dioxide is gathering in the atmosphere in the form of a blanket. Carbon monoxide, methane, etc. are other gases which act in similar fashion to form this blanket. The blanket does not allow the heat produced at the earth's surface to escape.

Effects of Air Pollution

(i) It causes respiratory diseases like asthma, bronchitis and lung cancer, etc.

(ii) It causes formation of smog (smoke plus fog) which irritates eyes and creates breathing problems. It also reduces visibility at night.

Prevention of Air Pollution

(i) Use public transport instead of single own vehicle.

(ii) Let the pollution rate of your vehicle be regularly checked.

(iii) Walk or use bicycle for shorter distances.

(iv) Try to do marketing from your nearby area, so that you don't have to use any vehicle for this purpose.

(v) Get CNG system installed in your vehicle. Nowadays, this is also a preventive measure to check air pollution.

2. Water Pollution

Addition of unwanted and harmful chemical substances into water bodies from various sources, e.g., sewage, industrial run off, pesticides, fertilizers, garbage, etc., causes water pollution. The physical and chemical properties of the water are changed when water gets polluted.

We should avoid throwing such pollutants into the water bodies directly. It should always be remembered that life is impossible without water.

Effects of Water Pollution

(i) Water pollution causes growth of such micro-organisms which cause water-borne diseases such as cholera, typhoid, jaundice and dysentery, etc.

(ii) It reduces oxygen availability to the marine life such as fishes.

(iii) Harmful substances like lead and mercury enter into the human body through the food chain.

Prevention of Water Pollution

(i) Do not throw wastes directly into the water bodies.

(ii) Stop people and animals defecating near the water sources.

(iii) Industrial effluents should be treated before their discharge into water.

(iv) Take care not to overuse pesticides and fertilisers. This will prevent runoffs of the material into nearby water sources.

Water and air pollution are very common and they cause harmful effects directly to our life.

3. Soil Pollution

Soil pollution is the result of two kinds of pollutants.

(i) Pollutants washed out of the atmosphere, as by acid rain, and

(ii) Insecticides and fertilizers used in agriculture.

Both of these alter the basic structure of the soil, kill minute organisms in it, and even reach the human body through crops grown in such fields.

Effects of Soil Pollution

Acid rain, chemicals and fertilizers, insecticides, pesticides, city garbage, etc., cause soil pollution.

They kill micro-organisms found in the soil which otherwise help to maintain soil fertility and even affect human health because of adulterated crops.

4. Noise Pollution

Noise pollution means unwanted sound. Noisy vehicles like buses, trucks, cars, loud speakers, music systems, television, jet planes, etc., cause noise pollution. High intensity sounds are harmful to man.

Some levels of sound and their sources are as follows:

Effects of Noise Pollution

Noise reduces concentration on work, reduces hearing efficiency, and causes headache.

Prevention of Noise Pollution

1. Play radios, televisions, stereos at low sound volume.

2. Close your doors if the outside noise is not under your control.

3. Do not scream, speak in soft voice.

Teacher's Note

Pollution affects our daily lives when we breathe polluted air, drink contaminated water, or experience loud traffic noise on our streets. Understanding these sources helps us make better choices at home and school.

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