Air Pollution - Source , impacts and control measures.

2. Is contamination of the air, irrespective
of indoors or outside. One could claim
that air pollution started when humans
began burning fuels. In other words, all
man-made emissions into the air can be
called air pollution, because they alter
the chemical composition of the natural
atmosphere some natural processes
also cause air pollution.

3. Quantity of pollutants which is sufficient to cause injury
to human beings and their living creatures.
AIR POLLUTION categorised into two types on the basis
of origin of pollutants:
First type of pollutants are released into the atmosphere
from a specific source.
Second type of pollutants are resulted from chemical
changes that take place in the atmosphere.

4. According to the formation of pollutants, two categories
are recognized:
Primary pollutants:- These enter in the air directly.
Secondary pollutants:- These are created in the air from
other pollutants under the influence of electromagnetic
radiation from sun.
SOURCES OF AIR POLLUTION
Major sources of air pollution are as follows:
Stationary combustion sources:- They are produced mainly
by burning of fuels (coal and petroleum) and these my be
gaseous or particulate in nature. Coal is largely carbon
mixed with some incombustible minerals, sulphur and
nitrogen. Petroleum consists of mainly hydrocarbons,
sulphur and nitrogen. Both fuels which on burning produce a
mixture of oxides in addition to CO2 and water.

5. Coal also produces mineral ash, some of which are
discharged as fly ash. Oxidation of sulphur and nitrogen
in the fossil fuel produces mainly SO2 , SO3,
nitrites(NO2), nitrates(NO3), etc. CO is also produced
by these fuels. The incomplete combustion of
hydrocarbons produces many gaseous and particulate
pollutants include a number of trace elements contained
in fly ash such as Sb,As,Be, Cd, Ge, Pb, Hg, Ni, Se, Va,
Yttrium etc.

6. Mobile combustion sources:- Such sources include
automobiles, locomotives, aircrafts etc. Major
pollutants released through these sources are CO, NOx,
hydrocarbons. Combustion of petroleum containing
lead products such as tetraethyl lead [Pb(C2H3)] and
tetramethyl lead [Pb(CH3)4] emits various particulate
lead compounds.
Incomplete combustion of fossil fuels undergo
photochemical reactions with oxides of nitrogen to
produce photochemical smogwhich contains
ozone(O3), peroxyacetyl nitrate (PAN), aldehydes etc.
These are often called the secondary pollutants.

7. Industrial processing and other sources:- The
chemical industries are thee main sources of
pollutants such as CO and SOx. Compounds
containing chlorine and fluorine, especially CFCs
(chlorofluorocarbons) are widely used as propellants
for aerosol cans and as refrigerants. These escape in
air and produce pollution.
A kind of particles, ice nuclei are emitted from
steel mills and automobiles. These modify clouds and
precipitation.

8. MAJOR POLLUTANTS
Air pollutants are broadly be divided into two types:
 Gaseous pollutants such as oxides of sulphur
(SO2,SO3), oxides of carbon (CO,CO2), oxides of
nitrogen (NO,NO2), H2S,NH3, fluorine, ozone,
hydrocarbons, aldehydes etc.
 Particulate pollutants such as dust, fly ash, smoke,
soot, aerosol droplets, mist ,fog, substances in air etc.

9. Gaseous pollutants
These are grouped into:
(a) inorganic gases
(b) organic gases.
(a)Inorganic gases
The various inorganic gases are:-
1. Oxides of sulphur
The important oxide of sulphur in the atmosphere is
sulphur dioxide (SO2).

10. The composition of fossil fuels used for domestic and industrial
purposes has resulted in sulphur dioxide (SO2). It is a
colourless gas with a suffocating and strong pungent odour.
Under certain conditions , SO2 reacts with oxygen to form SO3
(sulphur trioxide), which in turn combines with H2O to form
H2SO3 (sulphurous acid) and H2SO4 (sulphuric acid). SO2 is
called primary pollutant and H2SO3 and H2SO4 as secondary
pollutants .
2.Oxides of carbon
The two common types are CO and CO2.
The major source of the production of CO is the incomplete
burning of fossil fuels and wood charcoal etc. Other common
sources are cigerette smoke, motor vehicles, industries, domestic
heating appliances, oil refineries etc. It is a colourless, odourless
and tasteless gas.

11. CO2 is not a pollutant itself but human activities are
dangerously increasing its amount in the atmosphere. One of the
main reasons for its increase in the temperature is the widespread
use of combustible fuels. A continuous increase of unabsorbed
CO2 in the atmosphere would have a disastrous effect on the flora
and fauna, play havoc with the ecological balance and bring about
a catastrophic warming effect to the atmosphere resulting in the
green house effect or global warming.
3.Oxides of Nitrogen (NOx)
The main source of NOx are thermal power stations,factories,
automobiles and air crafts where fossil fuels are used. On global
level about 60% of nitrogen oxides are produced from natural
sources, including biomass burning, fixation by lighting, inflow
from the stratosphere, chemical conversion from ammonia in the
troposphere and loss from the soil.

12. NO and NO2 combine with water to form nitrous acid or nitric
acid which are highly corrosive and reactive in nature.
2NO2+H2O—>HNO2+HNO3
These also give rise to the most dangerous pollutants i.e.,
photochemical smog and peroxyacetyl nitrate(PAN). PAN (CH3-
CO-O-O-NO2) is the most notorious organic oxidant.
4.Ozone (O3)
It is a colourless gaseous secondary pollutant, produced by
chemical reactions between reactive organic gases and oxides of
nitrogen, particularly through the interaction of nitrogen oxide,
sunlight and hydrocarbons-
Nitrogen oxides+Hydrocarbons—> PAN+O3. Ozone is a major
component of photochemical smog. It is life savior ,if present in
stratosphere but a pollutant , if present in troposphere.

13. 4.Other inorganic gases
inorganic gases like hydrogen fluoride(HF),hydrogen sulphde
(H2S), ammonia(NH3),chlorine(Cl),arsine and phosgene etc. are
strong pollutants of the atmosphere . These are emitted from
various industries.
(b). Organic gases: The important organic gases pollutants are :
1.Aldehydes
The thermal decomposition of fats, oil, and glycerol releases
aldehydes in the form of organic gases. They affect nasal and
respiratory tract causing extreme irritation.
2.Hydrocarbons
Various hydrocarbons which pollute the atmosphere are methane
,volatile terpenes ,ethylene etc.Anaerobic degradetion of organic
matter produces about one billion metric tonnes of methane
annually.Hydrocarbons cause irritation and injury to the mucous
membrane.

14. PARTICULATE POLLUTANTS
These may be in the form of solid particiles or liquid
droplets including
fumes,smoke,fogg,dust,pollen,bacteria,fungi and aerosols.
1.Smoke and grit
The release of smoke and grit from domestic hearths and
factory chimneys is a major source of pollution in
industrial areas. These are released due to incomplete
combustion of fuels. These pollutants cause lung
irritation, asthma, bronchitis etc.

15. 2.Photochemical smog
The term smog was given to the atmospheric condition
to describe the unpleasant combinations of smoke and
fog. The toicity of smog is due to the presence of
various chemical compounds such as PAN and ozone
mixed in it.
3.Biocides and pesticides
These chemicals are commonly applied in the form of
sprays and as such an appreciable quantity of these
chemicals diffuses into the atmosphere in the form of
granules. Since such chemicals are non- biodegradable,
these seriously affect the human health when inhaled
and absorbed in the body.

16. 4.Heavy metals
The gaseous products of fuel combustion emitted from factories
and automobiles contain particles of toxic heavy metals harmful
to human beings. Lead poisoning or plumbism develops in man
when he is exposed to an atmosphere containing lead.
5.Radio-active elements
The radio-active dust that falls on earth or remains suspended in
the atmosphere is called radio active fall out.
6.Liquid particulates
Particulate of liquid nature are released by sprays and liquid
aerosols. Aerosols are chemicals which are released in the air
with force in the form of a mist or vapours. The liquid aerosols
contain fluoro-carbons which deplete the ozone layer permitting
UV radiations to reach the earth’s surface.

17. Impacts of Air Pollution

18. Acid Rain
e.g. Taj Mahal - Madurai refinery

19. Eutrophication
Accumulation of nutrients in water resources obstructing the life
or aquatic organism

20. Greenhouse Effect and Global
Warming.

21. Green house gases
CFC

23. Solutions
•
Reduce emissions: We must significantly reduce the heat-trapping emissions we are
putting into the atmosphere.
• Stop deforestation: Reducing tropical deforestation can significantly lower global
warming emissions and plays an integral role in a comprehensive long-term solution to
global warming.
•
Fight misinformation special interest groups raise doubts about the truth of global
warming. This barrage of misinformation
misleads and confuses the public — and makes it more difficult to implement effective
solutions.
•
Prepare for impacts: Certain consequences of global warming are now inevitable,
including sea level rise, more frequent and severe heat waves, and growing wildfire
risks.

24. Ozone layer
Depletion
Ozone is a gas that occurs
both at ground-level and in
the Earth's upper
atmosphere, known as the
stratosphere. At ground
level, ozone is a pollutant
that can harm human
health. In the stratosphere,
however, ozone forms a
layer that protects life on
earth from the sun's
harmful ultraviolet
(UV)rays.

26. Effect on environment:
• Effects on materials
1) The acid rains and photochemical smog cause considerable
effect on materials and buildings.
2) Acidic products cause disintegration of textiles, paper and
marbles.
3) Damages historical monuments.
4) Hydrogen sulphide decolorizes silver and lead pains.
5) Ozone oxidises rubber goods and cause damage to fabrics and
dyes.
• Effect on climate
1. Green house gases causing rise in global temperature.
2. Lead to melting of glaciers and polar ice caps, flooding of low
lying coastal plains, increase in flow of river, change in rain fall
pattern and submersion of islands.
3. Freon gas and nitrogen oxides deplete ozone layer.

27. • Effects on plants
1. SO2 produces bleached spots on leaves, chlorosis, early abscission, reduced
yield etc.
2. Oxides of nitrogen reduce crop yield, produces brown spots on leaves and
suppression of growth.
3. Fluorides reduce the crop yield and damage leaf tissues.
4. Chlorine induces bleaching, leaf tip and margin browning, dropping of leaves,
yellow spot etc.
5. Photochemical smog bleaches and blazes leaves of foliage crops. PAN develops
glazing, silvering or bronzing of lower surface of leaves.
6. Unsaturated hydrocarbons cause leaf fall, floral shedding, curling of petals,
decolouration of sepals, chlorosis, growth suppression etc.
7. Ozone causes tree to lose their leaves prematurely.
• Effects on animals
1. Air pollution causes wide spread damage to animals those are similar to human
beings.
2. Cause fluorosis (fluoride toxicity) commonly in domestic animals. This will
results in lameness, loss of weight, frequent diarrhoea and abnormal
calcification

28. Health Impacts 1. SO2 produces drying of mouth,
scratchy throat and smarting
eyes. H2SO4 damages tissue.
2. Nitrogen oxides impaires the
functioning of lungs by causing
accumulation of water in the air
pores.
3. CO2 leads to laziness, exhaustion
of body, headache, disturbance
of psychotor function, decrease
in visual perception, cardio-
vascular systems etc.
4. Radio-active elements cause
severe skin diseases and
deformities.
5. Silicon particles and fibres of
abestos cause silicosis, fibrosis,
byssinosis.
6. Air born spores, pollen grains,
bacteria, fungi, fur, hairs etc
cause allergic reactions. Like
bronchial asthma, hay fever and
diseases such as tuberculosis,
dermatitis etc.

29. Control of air
pollution

30.  Air pollution control is the elimination or
prevention of wastes (air emissions, water
discharges, or solid/hazardous waste) at the
source. In other words, pollution prevention is
eliminating wastes before they are generated.
Control approaches can be applied to all
pollution generating activity: hazardous and
nonhazardous, regulated and unregulated.

31. Use of purified petrol:
use of purified unleaded and good quality of petrol reduces
the level of sulphur and lead oxides in automobile exhaust.
Modernisation of industries:
the industrial machines and vehicle engines should be made
energy efficient to use fuels at the maximum level to reduce
the release of pollution.
Installation of air treatment plants: large number of
treatment plants for air purification must be installed and run
throughout the clock.
Use of alternative energy sources:
the common alternative sources are wind, water and sun.
Air pollution can be reduced by:

32. Treatment of emission:
the emission from factories and industries should be
treated by various techniques before releasing into
atmosphere.
Gravitational Settling Chamber
Cyclone Separator
Wet and Gas Scrubbers
Bag Filter
Electrostatic Precipitators
Adsorption
Incineration And Catalytic Combustion

33. Settling chamber:
These are large chambers in which
large particulates can be settled
down.
Example: gravitational settling
chamber.

34. Cyclone separator:
Works on the principle of
cyclone, in which the polluted air
is introduced into a conical
cylinder and made to whirl at a
high speed. As a result, the larger
particles strike against the wall
and drops down to the bottom of
the conical. The partially cleaned
air exists from the upper region.

35. Wet and gas scrubbers:
This is an effective and simple method for removing large particulates and
effluents gases. The polluted airs is introduced through a narrow opening and
water sprayed through the upper end. As a result of collision, the particulates are
scrubbed out from the air and settled down at the bottom. The poisonous gases
dissolve in water to form by products.

36. Bag filter:
Bag filters works on the principle of
vacuum cleaners. All particulates of
the polluted air are removed and clean
air is released from the top.

37. Electrostatic precipitators:
These are effective in removing fine particulates which the polluted air is
subjected to highly charged electrons, by passing through a pipe fitted
with electrodes. The particulates are collect in the pipe and are removed
at intervals of time. These are mainly used in power plants, carnet and
paper mills etc.

38. Adsorption:
the pollutants are captured from the polluted air through
adsorption by the use of activated carbons. This process is useful
in removing organic compounds.

39. Incineration
Gaseous pollutants are removed by burning them to CO2, H2O and
inert gases.

40. Catalyst Combustion
catalyst may be used to absorb the pollutants

41. Particulate Plantation of trees:
tree plantation should be made a national priority. Green plants
absorb CO2 for photosynthesis and thus reduce CO2 pollution
from the air. The tree lines function as dust or particulate filters.

42. Change in life style:
life style change may have considerable change in the reduction of air pollution.
Important measures are:
Use of energy more efficiently
Use of alternative sources of energy
Industries to install away from cities
Plantation of trees as green belt
Ideal traffic planning
Removal of unnecessary speed breakers and check posts
Checking of undesirable burning of vegetation
Car pooling etc.

43. Enforcement of Air (Prevention and Control) Pollution
Act, 1981
Air quality standards as recommended by CPCB (central pollution
control board) must be maintained strictly.
Clean Air Act (1963) - First national air pollution control.
Clean Air Act (1970) rewrote original.
Identified critical pollutants.
Established ambient air quality standards.
Primary Standards - Human health
Secondary Standards - Materials, environment, aesthetic and
comfort.

44. Environmental education:
The most important and fundamental programmes for
dealing with environmental problems is to impart
environmental education. Every citizen from his
childhood should be made aware of the problems of
environmental pollutions.

45. Control of air pollution is a difficult problem and
requires all round precaution and treatment. Use of
purified petrol, modernization of industries, use of
alternative energy sources are some preventive
measures. Treatment of emission can be tackled through
settling chambers, cyclones, wet and gas scrubbers, bag
filters, electrostatic precipitators, incineration and
catalytic combustion etc. plantation of trees and change
in life style also help in minimizing air pollution. Govt.
Of India has constituted Central Pollution Control
Board (CPCB) and has enforced “Air Pollution
(Prevention and Control) Act, 1981. Environmental
education also helps in reducing air pollution.