Air Pollution
Unit-4
Syllabus
• Air Pollution, Composition of Air, Structure of
atmosphere, Ambient air quality standards,
Classification of air pollutants, Sources of
common air pollutants like SPM, SO2, NOX,
Natural and anthropogenic Sources, and its
effects.
Air Pollution
• Definition:- Air pollution is define as
• “ Excessive concentration of foreign matter in
air, which adversely affects the well being of
individuals or causes damage to the property”.
Composition of Air
Atmosphere and its Structure
• Atmosphere:- The gaseous layer surrounding
the earth is known as atmosphere.
• The atmosphere is the life supporting mantle,
surrounding the earth.
• The atmosphere surrounds the earth up to
700 km, atmosphere is subdivided as
• Troposphere:- ( 0 To 12 Km) Contains 75 % of the
gases in the atmosphere. This is where we live
and weather occurs.
• Stratosphere:- (12 – 50 Km) this layer contains
ozone layer. Ozone acts as a shield for the earth’s
surface. It absorbs ultraviolet radiations from the
sun. This causes temperature increase in the
upper part of the layer.
• Mesosphere:- ( 50 to 80 Km) This is the coldest
region of the atmosphere. This layer protects the
earth from meteoroid. They burn up in this area.
• Thermosphere:- ( 80 Km and above) The air is
very thin in this region. Thermosphere means
“Heat Sphere”. The temperature is very high in
this region
• This layer contains:• (a) Ionosphere:-This is the lower part of the
thermosphere. It extends from 80 Km – 550 Km.
This
layer
generally
helps
in
radio
communication.
• (b) Exosphere:- The upper part of the
thermosphere. It extends from 550 km and
above. Air is very thin here this is the area where
satellite orbits the earth.
Structure of Atmosphere
* Ministry of Environment and Forests, Government of India notification,1994
** Particle size less than 10 µm
Ambient air Quality Standards
Pollutant
Time Weighted
Average
Concentration in Ambient Air
Industrial Area
Residential, Rural and
Sensitive Area
other
Sulphur Dioxide (SO2)
Annual
24 hours
80 µg/m3
120 µg/m3
60 µg/m3
80 µg/m3
15 µg/m3
30 µg/m3
Oxides of Nitrogen
(NO2)
Annual
24 hours
80 µg/m3
120 µg/m3
60 µg/m3
80 µg/m3
15 µg/m3
30 µg/m3
Suspended
Particulate Matter
(SPM)
Annual
24 hours
360 µg/m3
500 µg/m3
140 µg/m3
200 µg/m3
70 µg/m3
100 µg/m3
Annual
120 µg/m3
24 hours
150 µg/m3
60 µg/m3
100 µg/m3
50 µg/m3
75 µg/m3
Respirable **
Particulate Matter
(RPM)
Lead (pb)
Annual
24 hours
1.0 µg/m3
1.5 µg/m3
0.75 µg/m3
1.00 µg/m3
0.50 µg/m3
0.75 µg/m3
Carbon Monoxide(CO)
8 hours
1 hour
5.0 µg/m3
10.0 µg/m3
2.0 µg/m3
4.0 µg/m3
1.0 µg/m3
2.0 µg/m3
Major Sources of Air Pollution
• 1) Natural Sources:- The natural sources of air
pollution are volcanic eruptions, releasing of
poisonous gases like SO2 ( Sulfur dioxide),
Hydrogen
sulphide
(H2S),
Carbon
Monoxide(CO), Forest fires, natural organic
and inorganic decays, Pollen grains, wind
blown dust, among them pollen grain are
important because it causes allergic reactions
in individuals.
Anthropogenic sources
• (a) Rapid Industrialization:- The Industries such as
pulp and paper, chemical, metallurgical plants,
refineries are responsible for air pollution, the
most common pollutants are CO2, SO2, CO, NO,
H2S etc.
• (b) Transportation:- Automobile exhausts release
smoke. The smoke is a result of incomplete
combustion of carbonaceous matter. The
common pollutants are CO ( Carbon Monoxide),
CO2, and Hydrocarbons.
• (c) Burning of Fossil fuels and fires:- The
conventional sources of energy are wood,
coal, and fossil fuels. The byproducts of fossil
fuels is nothing but poisonous gases such as
CO, CH4 (methane), SO2, and NOX.
• (d) Deforestation:- The balance of O2 and CO2
is maintained in the nature by the vegetation.
The deforestation by man for his own needs
has disturbed the balance of CO2 and O2,
Concentration.
• (e) Increase in Population:- an increase in
population leads to global warming and
emission of green house gases. It also
contributes to losses in forest cover and loss
of wild life.
• (f) Agriculture activities:- Various pesticides
and insecticides are used for agricultural
purposes. Thus they cause air pollution.
• (g) Radioactive fallout:- Nuclear reaction,
nuclear weapon testing contributes towards
Nuclear pollution. Nuclear Pollutants are very
harmful to man, animals and vegetations.
Classification of air pollutants
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Air pollutants are broadly classified as
(a) According to origin
(b) According to chemical composition
(c) According to State of matter.
According to Origin
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Air Pollutants can be classified as
(a) Primary Pollutants
(b) Secondary Pollutants
Primary Pollutants:- Primary pollutants are
those which are directly emitted from
identifiable source
• These pollutants are emitted directly to the
atmosphere.
• Ex:(a) Particulate matter
(b) Oxides of Sulphur
(c) Oxides of Nitrogen
(d) Carbon Monoxide
(e) Radioactive Compounds
• Secondary air pollutants:- Secondary air
pollutants are those which are produced in
the air by the reaction of two or more primary
pollutants.
• Ex:• Ozone
• Formaldehyde
• Photochemical smog
• Peroxy acetyl nitrate (PAN)
According to Chemical Composition
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All the air pollutants are classified as
(a) organic pollutants
(b) In organic pollutants
(a) Organic Pollutants:- Organic Pollutants contain
carbon and hydrogen.
Ex:Hydro Carbon
Aldehyde and Ketones
Alcohols
Organic Sulphur compounds
• Inorganic Pollutants:- Inorganic compounds
mainly includes
• (a) Carbon monoxide (CO)
• (b) Carbon dioxide (CO2)
• (c)Carbonates
• (d) Oxides of sulphur, nitrogen
• (e) Ozone
According to State of Matter
• Air pollutants according to state of matter are
classified as
• (a) Natural Contaminants
• (b) Particulate matter
• (c) Gases and vapours
Natural Contaminants
• The air contaminants which are produced
from natural sources are called natural
contaminants
• Eg. Pollen grains are emitted from weeds,
grasses and trees
• This pollen grains are irritating to some
individuals
• Size of pollen grains = 10 to 50 (µ)
Particulate matter
• These may be liquid or solid.
The particulate matter are
identified as aggregates which
are larger than 0.002 µ but
smaller than 500 µ
• (a) Dust (1 To 10,000 µ) : Small
solid particles resulting from
break up of large masses
through processes such as
crushing, grinding or blasting.
• (b) Smoke ( 0.5 To 1 µ) Consist
of finely divided solid particles
produced
by
incomplete
combustion of organic particles
such as coal, wood, or tobacco.
• Mist:- These are liquid particles formed by
condensation of vapor
• Fog (1 to 40 µ ):- High concentration of mist is
called as fog. It is dispersion of liquid particles in
air.
• Fumes ( 0.03 to 0.3 µ ):- Fine solid particles
formed by the condensation of vapors of solid
material. The fumes are generally emit from
melting operations.
• Ash ( 1 to 1000 µ ):- fine, noncombustible
particles are known as fly ash.
• Spray (10 to 1000 µ):- Liquid particles formed by
automation
Gases And Vapors
• (a) Carbon Monoxide:- (CO) This is an odorless,
tasteless and colorless gas formed due to incomplete
combustion of carbonaceous matter. The sources of
carbon monoxide are motor vehicles, burning of fossil
fuel and industrial processes.
• (b) Oxides of Sulphur:- They Include 4 different gaseous
compounds such as Sulfur monoxide ( SO), Sulfur
dioxide ( SO2), Sulphur trioxide ( SO3) and sulphur tetra
oxide (SO4).
• Sulphur dioxide is a colorless, non flammable gas with
suffocating odor.
Oxides of Nitrogen
• Oxides of Nitrogen Include
4 gaseous
compound:- Nitric oxide ( NO), Nitrogen
dioxide (NO2), Nitrous Oxide (N) Nitrogen
penta oxide (N2O5)
• In air pollution, Nitric oxide (NO) and Nitrogen
dioxide are of prime concern.
The sources of this pollutants are Industrial
Processes, automobile exhausts.
Hydrocarbon
• Organic compounds containing only carbon and
hydrogen are classified as Hydrocarbons.
• They are of 2 types.
• (a) Aliphatic hydrocarbon
• (b) Aromatic hydrocarbon
• Hydrocarbon present in the atmosphere in the
atmosphere from both natural and man made
sources.
• The major sources of hydrocarbon is burning of
gasoline and industrial processes.
Effects of some common air pollutants
• 1) Particulate Matter:• Effects on human:• The pollutants of size less than 1 µ causes lung
damage
• Asbestos fibers causes cancer
• Lead from automobile exhaust affects brain
• It causes several respiratory diseases
• Silica , arsenic, dust causes cancer
• Effects on plants:• Deposition of particulate matter containing
toxic metals affects the growth of plants
• The particulate matter after deposition on
plant leaves block stomata opening of plants
and reduce plant growth.
• The particulate matter with acid rain, reduces
pH of the soil which makes the infertile.
• Effect on Material:
• The particulate matter causes damage to
building
• The corrosion is enhanced
• It causes cracks and fading of pointed surface
• Particulates accumulate on the soil and
reduces fertility of soil.
Carbon Monoxide
• Effects on humans:• The high concentration of CO can cause death
• The combination of CO and hemoglobin leads to the
formation of carboxylhaemoglobin (COHb) reduces the
oxygen carrying capacity of blood.
• At concentration of 100 ppm people experience
dizziness and headache.
• The cigarette smoke contains 400 to 450 ppm CO the
percentage of COHb in blood of cigarette smokers
increases with increase in smoking.
• At concentration of 750 ppm of CO it will cause death.
• Effects on plants:• CO reduces nitrogen fixing capacity of
bacteria. Which affects the plant growth.
• High concentration of causes leaf drops,
reduces the size of leaf and ageing
• Effects on materials:• Carbon monoxide appears to have no
detrimental effect on materials.
Oxides of Sulphur
• Effects on human health:• It causes irritation of eyes and respiratory
tracts.
• Increase in SO2 concentration in the
atmosphere, may lead to lung cancer
• SO2 may obstruct breathing
• SO2 leads to the formation of H2 SO4 which is
20 times more irritant than SO2
• Effects on Plants:• The low concentration for long period may
cause discoloration of leaves
• SO2 affects the growth of plants
• At high concentration the leaf tissues gets
damaged.
• H2SO4 is extremely toxic to plants and soil
fertility.
• Effects on materials:• The sulphuric acid will attack building
materials containing carbonates. This will form
CaSO4 the CaSO4 gets easily washed away
leaving discolored surface
• Paper absorb SO2 causing the paper to
become brittle
• Leather looses the strength and flexibility.
Oxides of Nitrogen
• Effects on Human Health: nitric Oxide reduces
the Oxygen carrying capacity of blood.
• Nitrogen dioxide causes irritation of lungs
• High level of NOx causes pneumonia, lung
cancer, oxygen deficiency.
• NOx causes irritation of respiratory system,
nervous system and digestive tracts.
• NOx is extremely dangerous to human health.
• Effects on vegetation:• NO2 and primary pollutants can damage plant
tissues
• High concentration of NO Causes Damage to
leaves.
• Secondary Pollutants such as smog, O3 may
damage the vegetation
• Effects on materials:• Nitric acid causes corrosion to metal surface
• NO2 fades the color of clothes
• NO2 causes cracking of rubber
Hydrocarbon
• Effects on human health:• Aromatic hydrocarbon may lead to cancer
• Inhalation of hydrocarbon causes irritation of
respiratory tract.
• Methane creates narcotic effects on human
beings
• Most of the hydrocarbon are carcinogenic to
lungs
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Effects on Vegetation:HC affects plant growth
Discoloration of leaves
Effects on Materials:It causes discoloration of materials
Material becomes less elastic and more
brittle.
Notations
• parts-per-million (ppm) 10–6, parts-per-billion
(ppb) 10–9, and parts-per-trillion (ppt) 10–12
level
Prevent Air Pollution