Science Chapter 18 Pollution Of Air And Water

Water gets contaminated by following ways :

(i) Disposal of sewage in rivers.

(ii) Throwing of chemicals which are harmful and poisonous in the water bodies by various industrial units.

(iii) Mixing of harmful chemicals used in agricultural process with ground water, making it unfit for consumption. 

We can reduce the air pollution in the following ways-:
i Planting trees to reduce the level of carbon dioxide.
ii. Getting our vehicles serviced well to reduce incomplete consumption of fuels.
iii. Saying no to crackers during Diwali celebrations.
iv. Walking to nearby places and saving fuel.

No, clear or transparent water is not always fit for drinking as it may have microorganisms and dissolved impurities which cannot be seen with naked eyes. These impurities and microbes may cause diseases. 

To ensure the supply of clean water to all its residents the following measures can be taken :

(i) Strict laws should be enforced on industrial units, which dispose polluted water in water resources.

(ii) Open defecation in water resources by slum dwellers should be strictly prohibited.

(iii) The water supplied should be treated properly , made fit for use and  free from impurities and microorganisms. Chlorine tablets should be distributed for purification of water during rainy season.

(iv) People should be made aware and motivated to keep water resources clean.

Pure air has 78% nitrogen, 21% is oxygen and carbon dioxide, argon, methane, ozone and water vapour are also present in very small quantities. Pure air has balanced quantity of all its constituent gases and it is free from harmful gasesand is fit for breathing.
On the other hand polluted air has unwanted gases and other suspended impurities like dust and smoke. It is unfit for breathing and has a harmful effect on both the living and the non-living. 

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Acid rain is caused due to mixing of poisonous gases with rain. The industries emit harmful gases like sulphur dioxide and nitrogen dioxide, these gases react with moisture present in air and form nitric acid and sulphuric acid. These acids fall on the earth along with rain making rain water acidic and harmful. Acid rain causes the corrosion of buildings and make food grains, fruits and vegetables unfit for consumption.

B.

Sulphur dioxide

Green house effect is the process by which the heat energy of the sun is trapped inside the earth's atmosphere just like a green house. When the rays of sun reaches the earth, some of the heat is absorbed by the earth and rest of it is reflected back by the earth. Some of the heat is trapped by the environment of the earth. Carbon dioxide gas is mainly responsible for trapping the heat. This causes warming of the environment, which is necessary for the sustaining life. This trapping of the heat is called green house effect.

Global warming is a serious threat to earth. The continuous increase in the average  temperature of the earth is called global warming. It is caused by the excessive heat trapped by the green house gases. The increase in the green house gases due to the human activities and the cutting down of trees which utilize carbon dioxide a major green house gas is paving way for global warming.  
Global warming could result in wide ranging effects like rise in the sea level, submergence of the coastal area, change in rainfal, agriculture pattern etc. Research has shoen that if we do not keep the greenhouse gases at the present level, then, the temperature may rise by more than 2 degrees Celsius by the end of the century, which can be very dangerous for all the life forms. Therfore, we need to control global warming.

The pollution and soot prticles from industries are causing the yellowing of the marble of the Taj mahal. The industries like Mathura oil refineries increase the concentration of gases like sulphur dioxide and nitrogen dioxide. These gases react with water vapour in the air and fall along with the rain forming Acid rain. The acid corrodes the marble and causes marble cancer. The yellowing and the corrosion of the marble is a major threat to the beauty of the Taj Mahal. 

Increased level of nutrients result in the excessive growth of algae in the water. Death of the algae in turn, results in flourishing of the microorganisms. These microbes consume a lot of oxygen present in water. The insufficient oxygen content poses  trouble for other aquatic animals and leads to their death.

Causes of smoke are :

(i) Automobiles

(ii) Burning of fuels.

Respiratory problems.

Any undesirable change in the physical, chemical or biological characteristics of the natural environment is called pollution.

The presence of chemicals in the air in quantities harmful to human health and the environment is known as air pollution.

Carbon dioxide, carbon monoxide, nitrogen oxides, etc are released by vehicles.

Carbon monoxide.

A smog is mixture smoke and fog. 

Sulphur dioxide and nitrogen dioxide are responsible for acid rain. .

Carbon dioxide.

Global warming is the increase in the average temperature of the earth's atmosphere.

Green house effect.

Chloro fluoro carbon (CFCs)

The phenomenon whereby the Earth's atmosphere traps solar radiation because of the presence of gases such as carbon dioxide, water vapour and methane is called green house effect.

Water which is suitable for drinking is called potable water.

Infra-red radiation.

Sea water is not fit for drinking because it contains high concentration of salts which may induce dehydration and vomiting. 

The suspended impurities present in a sample of water can be removed by filtering water through a fine muslim cloth.

Chlorine is added to the filtered water before supplying it to the people in a city to purify the water.

The process of nutrient enrichment of aquatic ecosystems and the subsequent over-growth of algae on the surface of water is called eutrophication.

Excess growth and decay of algae serves as food for the microorganisms. This leads to excessive growth of microorganism and use of oxygen by them. Thus, causing depletion of oxygen.

Reduce, Reuse and Recycle.

Sewage must be treated to obtain pure and clean water. Untreated sewage contains many bacteria, viruses, fungi and parasites which cause diseases like cholera, typhoid and jaundice. Therefore to ensure that the water is free from such harmful agents, the sewage must be treated. 

Corrosion of marble due to acid present in the rain is called marble cancer.

CNG (Compressed Natural Gas) and LPG (Liquefied Petroleum Gas).

CNG—Compressed Natural Gas.

LPG—Liquefied Petroleum Gas.

Air pollution can be controlled :

(i) By using use of CNG in automobiles .

(ii) By replacing wood, coal and kerosene with LPG for domestic use.

Methods to control water pollution :

(i) Avoid throwing of the garbage into rivers/ lakes. The rivers/lakes should be cleaned from time to time.

(ii) The sewage and the effluents must be treated before releasing them into water bodies. Strict laws should be implemented so that industries do not dispose the polluted water in the rivers or lakes directly.

Following are various causes of air pollution :

(i) Smoke emitted due to fires in forests or burning of wood and charcoal.

(ii) Poisonous gases released into the atmosphere by various industries.

(iii) Poisonous gases like carbon monoxide, carbon dioxide, nitrogen oxides and smoke etc. emitted by vehicles. 

Vehicles are a major cause of air pollution. The combustion of fuel in the vehicles emit high levels of pollutants like carbon monoxide, carbon dioxide, nitrogen oxides and smoke. Carbon monoxide is produced by incomplete combustion of fuel. It is highly poisonous and reduces the oxygen carrying capacity of blood. These gases pollute air. 

Global warming is the increase in the average temperature of the earth's atmosphere.
Gases responsible for global warming are carbon dioxide, methane, nitrogen oxide and water vapours. These are known as green house gases. 

Global warming has many ill effects.

(i) It may lead to rise in the sea level and submergence of the coastal areas.

(ii) It can have negative impact on rain fall pattern, agriculture , human and animal life.

(iii) It may lead to rise in temperature which will have many ill effects on the life forms.

Ozone is a gas which forms a protective layer around earth. It protects the earth from the harmful ultraviolet radiations of the sun. It does not allow the ultraviolet rays of the sun from reaching the earth. U.V. radiations can cause great damage to our earth and life forms. Thus, ozone is helpful in protecting the earth from the harmful effects of U.V. radiations.

Ozone depletion is the thining of the ozone layer due to the chemicals like CFCs.The layer is completely depleted and holes are created in some regions like the Antarctic.  These holes are called ozone holes.

Air pollution has harmful effects on living as well as non-living beings. It causes many diseases in human beings like respiratory diseases. It causes harm to our building and monuments. It reduces visibility as smog which may lead to many serious accidents. The smog causes respiratory, skin and eye infections. 

The Taj Mahal is one of the seven wonders of the world. The white marble is turning yellow, due to the deposition of the soot particles emitted from the industries. The release of gases like sulphur dioxide and nitogen dioxide leads to formation of acid rain. Acid rain corrodes the marble of the monument and causes marble cancer. The discolouring and corrosion of marble is decreasing the beauty of the Taj Mahal. 

The reaction of gases like sulphur dioxide and nitogen dioxide with the water vapour in the atmosphere forms sulphuric acid and nitric acid. These acids precipitate along with the rain forming acid rain. 

The Supreme Court has taken several steps to save the Taj Mahal from air pollution. It has given orders that -:
i. Unleaded petrol must be used by the vehicles in the Taj zone.  
ii. industries should switch to cleaner fuels like CNG (Compressed Natural Gas) and LPG (Liquefied Petroleum Gas).

The fuels which can be used instead of fossil fuels are :

(i) Solar energy,

(it) Hydropower and

(iii) Wind energy.

Throwing of garbage in the rivers causes pollution. They act as nutrients and enhance the growth of algae. As these algae die, they serve as food for microorganisms like bacteria. The bacteria uses up the oxygen of the water body. The lack of oxygen proves harmful for the aquatic organisms and may lead to their death. 

Water can be purified by the following methods :

(i) By filtration : Any suspended impurity in the water from well, river or lake can be removed by filtering water through a fine muslin cloth.

(ii) By boiling : Boiling of water for 10-15 minutes kills the germs present in it.

(iii) By using domestic water filters and purifiers : The simplest form of domestic water filter consists of a porous pot made of clay/ceramic. The porous pot acts as a filter and removes all suspended impurities from the water.

(iv) By using water purifiers. These purifiers apart from removing suspended impurities also remove harmful salts and kill harmful microorganisms by ultraviolet radiation.

P : Fertilizer. Q : Algae

R : Bacteria S : Oxygen.

(a) Sewage is the common name for such waste.

(b) Bacteria, protozoa, fungi, viruses, parasites (worms) are found in the sewage.

(c) Diseases like cholera, tyhpoid, diarrhoea, dysentery, jaundice are caused by drinking water contaminated with such waste.

(i) The burning of fossil fuels may cause acid rain which turns the river water acidic leading to the death of the fishes.

(ii) Farmers use fertilisers in agricultural practices. These fertilisers run into lake water and cause too much growth of algae. Decomposition of dead algae by bacteria by using dissolved oxygen of lake water decreases the oxygen concentration of the lake. Fish may die due to lack of oxygen.

X is carbon monoxide.

Y is haemoglobin ( pigment of the blood) and

Z is oxygen.

Following factors are responsible for air pollution.

(i) Industrial Emissions : Various dangerous and poisonous gases emitted by different industries cause air pollution. These gase causes smog and acide rain. 

(ii) Vehicles : The combustion of fuel inside the vehicle  releases many pollutants like carbon monoxide, carbon dioxide, nitrogen oxides and smoke.

(iii) Natural Pollutant : Forest fire, volcanic eruption, dust storms etc., also cause air pollution.

(iv) Other activities of Man : Besides above described causes many other human activities like using cow dung, coal, wood as fuels etc. pollute the air. Burning of crackers on Diwali and other celebrations releases many harmful gases in the atmosphere.

Water pollution is caused by many factors  :

(i) Industrial discharges : Various harmful and poisonous chemicals and substances are discharged by industries directly into water bodies. 

(ii) Domestic discharges : Sewage from homes are collected and disposed off in rivers nearby. This untreated sewage is one of the prominent causes of water pollution.

(iii) Religious Rituals : Various religious rituals like dispersion of dead bodies or remains of dead bodies in rivers is causes water pollution .

(iv) Other Human Activities : Human activities like washing of clothes on garbage in water bodies aalso pollutes the water bodies.

The characteristics of potable water are :

(i) It should be colourless and odourless.

(ii) It should be free from any suspended impurities.

(iii) It should be free from any harmful germs.

(iv) It should be free from large quantity of salts.

(v) It should be free from any harmful salt such as nitrates, cyanides, urea etc.

Ganga Action Plan was a programme launched in 1985 to save the river Ganga. It aimed to reduce the pollution level in the river. 

water

carbon dioxide 

potable

carbon monoxide

untreated sewage

chlorine

avoided

pollution

ozone

increase

B.

Air pollution

B.

Respiratory diseases

D.

Carbon dioxide

D.

All the above

C.

Marble cancer.

C.

Nitrogen

C.

acid rain

B.

domestic sewage and animal excreta

B.

ultra violet rays

A.

chlorine