ICSE Class 10 Biology Chapter 15 Pollution

Pollution - A Rising Environmental Problem

Syllabus

(i) Types of pollution - air, water (fresh and marine), soil, radiation and noise. Self explanatory.

(ii) Sources of pollution and major pollutants.

(iii) Effects of pollution on climate, environment, human health and other organisms and its abatement. Greenhouse effect and global warming, Acid rain, Ozone layer depletion.

Meaning of the terms, causes, effect on life on earth, idea about setting standards - Euro/Bharat stage vehicular standards.

Scope Of Syllabus

Sources of pollution and major pollutants.

Air: Vehicular, industrial, burning garbage, brick kilns.

Water: Household detergents, sewage, industrial waste, oil spills, thermal pollution.

Soil: Industrial waste, urban commercial and domestic waste, chemical fertilizers, biomedical waste like needles, syringes, soiled bandages etc., biodegradable waste like paper vegetable peels, etc., non-biodegradable waste like plastics, glass, styrofoam, etc, pesticides like DDT etc.

Radiation: X-rays, radioactive fall out from nuclear plants.

Pollution is a serious problem of the modern times due to very rapid advancement in several areas such as industries, transport, agriculture, residential set-ups, thermal and nuclear power generation plants. It is causing deterioration and even poisoning of the environment including air, water and soil. It is posing a serious threat to human health as well as to almost all kinds of our surroundings.

15.1 Pollution

Pollution is the addition of any such constituent to air, water or land which deteriorates the natural quality of the environment.

AND

Pollutant is any such constituent which causes pollution.

Types Of Pollution

There are five major types of pollution:

1. Air pollution

2. Water pollution

3. Soil pollution

4. Radiation

5. Noise

15.2 Air Pollution

Air pollution means degradation of the air quality harmfully affecting the living organisms as well as certain objects.

Types Of Air Pollution

The air pollution is basically of two types:

1. Gaseous pollution: Harmful gases given out from a variety of sources.

2. Particulate pollution: Particles such as those of dust, smoke, mining, stone drilling, wearing of rubber tyres of motor vehicles.

Sources Of Air Pollution

1. Natural sources

Examples: Ash from burning volcanoes, dust from storms and forest fires. These pollutions are beyond human control and will continue to occur.

2. Man-made sources

Examples: Vehicular (automobiles), industries, garbage, brick kilns. These are the four major sources which, to a great extent, are under human control and the methods for controlling them are being developed.

Teacher's Note

Air pollution affects our daily lives when we notice smog over cities or struggle with breathing on high-traffic days - it directly impacts the air we breathe every moment.

15.2.1 Vehicular Air Pollution

There are various kinds of vehicles - the motor cars, trucks, buses, scooters, tractors, motor cycles, railway engines, etc. They are mostly running on petrol and diesel. The exhaust given out contain three main gaseous pollutants: CO2, SO2 and CO. Simultaneously, there is the wearing of rubber tyres of the automobiles releasing rubber particles and furthermore, the speeding vehicles also raise the road dust particles into the air. You must have also experienced a lot of dust raised when the road cleaners sweep the roads every morning.

Control: Efficient engines, good quality automobile fuels, lead-free petrol, greater use of compressed natural gas (CNG).

Teacher's Note

When you see a vehicle's exhaust smoke or feel dust particles on a busy road, you're directly experiencing vehicular air pollution and its effects on air quality.

15.2.2 Industrial Air Pollution

The whole world is undergoing extensive industrial revolution. It ranges from small scale pottery and carpet weaving units to huge sugar factories, cloth factories, metal factories, automobile manufacturing units, drug manufacturers, oil refineries and so on. They give out all kinds of pollutants.

The chief industrial gaseous pollutants again consist of CO2, SO2 and CO and also oxides of nitrogen.

The smoke released by the factory chimneys into the air contains lot of particulate pollutants.

Smog (Smoke plus Fog)

The smoke released from various sources may get mixed with dust particles and small drops of fog to produce what is called smog. Smog is harmful to plants and, if inhaled, may cause asthma and allergies is humans.

15.2.3 Burning Garbage

The garbage mainly consists of items such as peelings of vegetables and fruits, shells taken off from dry fruits, washings of pulses, rice, etc., and also the leftovers in food dishes. Such waste is either used in composting (making manure for agricultural use) or burnt in special enclosures. On burning, the garbage releases CO2 and some other harmful gases too. The smoke given out adds to the particulate air pollution.

15.2.4 Brick Kilns

Brick kilns (Hindi: "centon ke bhatte")

The brick kilns are fire-heated enclosures for making construction bricks. Raw moist clay bricks are arranged in heaps with fire-wood in between and then covered by layer of some special mud mixture to contain the burning flames inside. This set-up is left for a few days. The smoke collecting inside is released through a hole. On opening, the original mud-coloured bricks are found to be red, and there is a huge quantity of ash. The wastes produced are large quantities of ash and broken brick bits. These are all pollutants, which are either somehow reused or just dumped. Lot of smoke and heat given out are the pollutants.

Progress Check

1. Mention whether the following statements are true (T) or false (F)

(i) Pollution and pollutant are one and the same thing. (T/F)

(ii) Rubber tyres of motor vehicles contribute to particulate pollution. (T/F)

(iii) The chief gaseous air pollutants are CO2 and SO2. (T/F)

(iv) Kitchen garbage and leftovers in food dishes can be used for making manure (compost). (T/F)

(v) Brick kilns give out both gaseous and particulate pollutants. (T/F)

Teacher's Note

When you see factories belching smoke or smell burning garbage, you're witnessing industrial and burning sources of air pollution that we encounter regularly in urban environments.

15.3 Water Pollution

Water pollution means any change in the water quality which makes it unsuitable for use by humans and by other living organisms.

Sources Of Water Pollution

The five major sources of water pollution are as follows:

1. Household detergents - 2. Sewage

3. Industrial wastes - 4. Oil spills

5. Thermal pollution

15.3.1 Household Detergents

Every home uses some detergents (cleansing agents) to wash and clean the soiled or worn garments, crockery, utensils, etc. The dirty water flows down the drains.

15.3.2 Sewage

Sewage is the liquid waste from domestic activities. It consists of kitchen waste, toilet and other household waste water. Most cities have sewage treatment plants to remove the dirty part and release the cleaned fluid water into nearby water bodies or rivers. Small towns and villages may still be releasing their fluid wastes directly into some nearby large water body (river/lake).

[At some places, people are still following the practice of disposing off the dead bodies into the rivers, specially in India. If not the dead bodies, the ashes after cremation are very commonly immersed into rivers like Ganga at many places. We like it or not, such practices are sources of water pollution].

15.3.3 Industrial Waste

A large number of industries (small scale as well as large scale) produce waste water which contains various types of chemical pollutants. Such wastes are commonly discharged into the rivers. Fish processing industries set up near sea coasts release toxic wastes into the sea causing pollution.

15.3.4 Oil Spills

Oil spills are the accidental discharges of petroleum in oceans or estuaries. The sources of spills are the overturned oil tankers, offshore oil mining, oil refineries. Oil pollution kills a lot of marine life (fish, birds, etc.).

15.3.5 Thermal Pollution

Many industries (thermal power plants, oil refineries and even nuclear power plants) use water for cooling their machinery. This hot waste water may be 8-10-C warmer than the intake water, and is released into the nearby streams, rivers or the sea and causes warming. This warming of water harmfully affects the animals (even killing the fish), and harms the plant life living in it.

Progress Check

1. Mention whether the following statements are true (T) or false (F)

(i) Liquid kitchen waste alone constitutes the sewage. (T/F)

(ii) Household detergents are safe and non-contributors to water pollution. (T/F)

(iii) Industrial wastes mainly consist of chemical pollutants. (T/F)

(iv) Thermal power plants give out a lot of hot waste water. (T/F)

(v) Hot water discharged into water bodies hardly affects the fish and other aquatic life. (T/F)

Teacher's Note

When you wash dishes or see polluted rivers, you're witnessing water pollution sources that directly impact the freshwater resources our communities depend on daily.

15.4 Soil Pollution

The soil pollution is largely localised whereas the air and water pollutions can spread to long distances. The major sources of soil pollution are:

1. Industrial wastes

2. Urban commercial and domestic waste

3. Chemical fertilizers

4. Biomedical waste

5. Pesticides

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