Lecture 2: Air Pollution
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What is Environmental Pollu on
Defini on of Air Pollu on with examples.
Classifica on of Air Pollutants
Causes/Sources of Air Pollu on or Air Pollutants
Control/Preven ve /Remedial Measures to Minimize Air Pollu on
WHAT IS ENVIRONMENTAL POLLUTION
• For normal and healthy living a conduc ve environment is required by
all living beings including humans, plants, micro-organisms and the
wildlife.
• The favourable unpolluted environment has a specific composi on.
When this composi on gets changed by addi on of harmful
substances, the environment is called polluted environment and the
substances pollu ng it are called pollutants.
• Environmental pollu on can, therefore be defined as any undesirable
change in the physical, chemical or biological characteris cs of any
component of the environment (air, water, soil) which can cause
harmful effects on various forms of life or property.
DEFINITION OF AIR POLLUTION
• Air pollu on is an atmospheric condi on in which certain substances
(including the normal cons tuents in excess) are present in
concentra ons which can cause undesirable effects on man and his
environment. These substances include gases, par culate ma,er,
radioac ve substances etc.
• Gaseous pollutants: include oxides of sulphur (mostly SO2, SO3), oxides
of nitrogen (mostly NO and NO2 and NOx), carbon monoxide (CO),
vola le organic compounds (mostly hydrocarbons) etc.
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Par culate pollutants: include smoke, dust, soot, fumes, aerosols, liquid
droplets, pollen grains etc.
Radioac ve pollutants: include radon-222, iodine-131, stron um-90,
plutonium-239 etc.
CLASSIFICATION OF AIR POLLUTANTS
• On the basis of origin of pollutants, air pollutants can be classified as
primary or secondary pollutants.
(a) Primary Pollutants: These are emi,ed directly from the point
source (iden fiable source) e.g., carbon monoxide (CO), oxides of
nitrogen (NOx), oxides of sulphur (SOx), hydrocarbons, radioac ve
substances etc.
(b) Secondary Pollutants: These are formed by interac on of primary
pollutant (s) with other primary pollutant (s) or with some natural
cons tuents of atmosphere, e.g., ozone (O3), peroxyacetyl nitrate
(PAN), photochemical smog etc.
CAUSES/SOURCES OF AIR POLLUTANTS
• Sources of air pollu on are Natural and Man-made (Anthropogenic).
• Natural Sources:
1. Volcanic Erup ons
2. Forest Fires
3. Sea Salt Sprays
4. Biological Decay
5. Photochemical Oxida on of Terpenes
6. Marshes
7. Extra Terrestrial Bodies
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8. Pollen Grains of Flowers, spores etc.
9. Radioac ve minerals present in the earth crust are the sources of
radioac vity in the atmosphere.
Man-made Sources (Anthropogenic):
1. Thermal Power Plants
2. Industrial Units
3. Vehicular Emissions
4. Fossil Fuel Burning
5. Agricultural Ac vi es etc.
CONTROL/PREVENTIVE/RENEDIAL MEASURES TO MINIMIZE AIR POLLUTION
• Si ng of industries aAer proper Environmental Impact Assessment
studies.
• Using low sulphur coal in industries.
• Removing sulphur from coal (by washing or with the help of bacteria).
• Removing NOx during the combus on process.
• Vehicular pollu on can be checked by regular tune-up of engines;
replacement of more pollu ng old vehicles; installing cataly c
converters; by engine modifica on to have fuel efficient (lean) mixtures
to reduce CO and hydrocarbon emissions; and slow and cooler burning
of fuels to reduce NOx emission (Honda Technology).
• Using mass transport system, bicycles etc.
• ShiAing to less pollu ng (clean) fuels (hydrogen gas).
• Using non-conven onal sources of energy.
• Using biological filters and bio-scrubbers.
• Plan ng more trees.
• Reduc on of pollu on at source.
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