Chemistry : Environmental Chemistry - Class 11 Class 11 Notes | EduRev

Class 11 : Chemistry : Environmental Chemistry - Class 11 Class 11 Notes | EduRev

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186 
 
CHAPTER 14 
ENVIRONMENTAL CHEMISTRY 
 Environmental chemistry deals with the study of the 
origin,transport,reactions,effects,fates of chemical species in the environment. 
 ENVIRONMENTAL POLLUTION:-Environmental pollution is the effect of 
undesirable changes in our surroundings that have harmful effects on plants, 
animals and human beings.A substance which causes pollution is called a 
pollutant.they can be solid,liquid or in the gaseous state. 
 ATMOSPHERIC POLLUTION:-The atmosphere that surrounds the earth is 
not of the same thickness at different heights.Atmospheric pollution is 
generally studied as tropospheric and stratospheric pollution.The ozone layer 
prevents about 99.5%of the sun’s UV rays. 
 TROPOSPHERIC POLLUTION:-Tropospheric pollution  occurs due to the 
presence of undesirable solid  or  gaseous particles in the air. The following 
are the major gaseous and particulate pollutants present in the troposphere;  
 Gaseous air pollutants:These are oxides of sulphur, nitrogen and 
carbon, hydrogen sulphide, hydrocarbons, ozone and other 
oxidants.  
 Particulate  pollutants; these are dust, mist, fumes, smoke, smog 
etc 
 GLOBAL WARMING AND GREENHOUSE EFFECT:-About 75% of the 
solar energy reaching the earth is absorbed by the earth’s surface,which 
increases it’s temperature.The rest of the heat radiates back to the 
atmosphere.Some of the heat is trapped by the gases such as carbon 
dioxide,methane,ozone,CFCS and Water vapour.they add to the heating of the 
atmosphere causing Global warming 
In a greenhouse,visible light passes through the transparent glass and heats up 
the soil and the plants.The warm soil and plants emit infrared rays,it partly 
reflects and partly absorbs these radiations,this mechanism keeps the energy of 
the sun trapped in the greenhouse. 
 ACID RAIN:When the pH of the rain water drops below5.6, it is called acid 
rain.Acid rain is harmful for agriculture, trees and plants as it dissolves and 
washes away nutrients needed for their growth. It causes respiratory ailments 
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186 
 
CHAPTER 14 
ENVIRONMENTAL CHEMISTRY 
 Environmental chemistry deals with the study of the 
origin,transport,reactions,effects,fates of chemical species in the environment. 
 ENVIRONMENTAL POLLUTION:-Environmental pollution is the effect of 
undesirable changes in our surroundings that have harmful effects on plants, 
animals and human beings.A substance which causes pollution is called a 
pollutant.they can be solid,liquid or in the gaseous state. 
 ATMOSPHERIC POLLUTION:-The atmosphere that surrounds the earth is 
not of the same thickness at different heights.Atmospheric pollution is 
generally studied as tropospheric and stratospheric pollution.The ozone layer 
prevents about 99.5%of the sun’s UV rays. 
 TROPOSPHERIC POLLUTION:-Tropospheric pollution  occurs due to the 
presence of undesirable solid  or  gaseous particles in the air. The following 
are the major gaseous and particulate pollutants present in the troposphere;  
 Gaseous air pollutants:These are oxides of sulphur, nitrogen and 
carbon, hydrogen sulphide, hydrocarbons, ozone and other 
oxidants.  
 Particulate  pollutants; these are dust, mist, fumes, smoke, smog 
etc 
 GLOBAL WARMING AND GREENHOUSE EFFECT:-About 75% of the 
solar energy reaching the earth is absorbed by the earth’s surface,which 
increases it’s temperature.The rest of the heat radiates back to the 
atmosphere.Some of the heat is trapped by the gases such as carbon 
dioxide,methane,ozone,CFCS and Water vapour.they add to the heating of the 
atmosphere causing Global warming 
In a greenhouse,visible light passes through the transparent glass and heats up 
the soil and the plants.The warm soil and plants emit infrared rays,it partly 
reflects and partly absorbs these radiations,this mechanism keeps the energy of 
the sun trapped in the greenhouse. 
 ACID RAIN:When the pH of the rain water drops below5.6, it is called acid 
rain.Acid rain is harmful for agriculture, trees and plants as it dissolves and 
washes away nutrients needed for their growth. It causes respiratory ailments 
187 
 
in human beings and animals. When acid rain falls and flows as ground water 
to reach rivers, lakes etc. it affects plants and animal life in aquatic ecosystem 
 
 SMOG:The word smog is derived from smoke and fog.There are two types of 
smog:classical and photochemical smog. Classical smog occurs in cool humid 
climate. It is a mixture of smoke, fog and sulphur dioxide. It is also called 
reducing smog. Whereas photochemical smog occurs in warm and dry sunny 
climate. It has high concentration of oxidizing agents and therefore ,it is also 
called as oxidizing smog 
 
 OZONE HOLE:Depletion of ozone layer is known as ozone hole. 
 
 EFFECTS OF DEPLETION OF THE OZONE LAYER: With the depletion of 
ozone layer, more UV radiation filters into troposphere. UV radiations lead to 
ageing of skin, cataract, sunburn, skin cancer, killing of many phytoplanktons, 
damage to fish productivity etc 
 WATER POLLUTION:-contamination of water by foreign substances which 
make it harmful for health of animals or plants or aquatic life and make it unfit 
for domestic, industrial and agriculture use. 
 SOURCES/ CAUSES OF WATER POLLUTION- 
 Sewage and domestic wastes 
 Industrial effluents 
 Agriculture effluents 
 Siltation-mixing of soil or rock into water 
 Thermal pollutants 
 Radioactive discharge 
 EUTROPHICATION:The process in which nutrientenriched water bodies 
support a dense plantpopulation, which kills animal life by deprivingit of 
oxygen and results in subsequent loss ofbiodiversity is known 
asEutrophication 
 
 BOD: The amount of oxygen required by bacteria to break down the organic 
matter present in a certain volume of a sample of water, is called Biochemical 
Oxygen Demand (BOD) 
 
 SOIL POLLUTION:Insecticides, pesticides and herbicides cause soil 
pollution. 
 
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