1. CE8005 - Air Pollution and Control
Unit 1
Structure and composition of Atmosphere –
Definition, Scope and Scales of Air Pollution – Sources
and classification of air pollutants and their effect on
human health, vegetation, animals, property,
aesthetic value and visibility- Ambient Air Quality and
Emission standards –Ambient and stack sampling and
Analysis of Particulate and Gaseous Pollutants

2. Air Pollution and Air Pollutant
• Pollution in atmospheric air due to presence
of solid, liquid and gaseous material
• It causes problems to human, living
organizms.
• Pollutant is the material which creates the air
pollution.
• Pollutants affect the atmospheric air
considerably and creates harmful effects.

3. Structure of Earth’s Atmosphere

4. Structure of Earth’s Atmosphere

5. Vertical Structure of Atmosphere

6. Structure and composition of Atmosphere
• Earth’s atmosphere is composed of about 78% nitrogen, 21%
oxygen, and 0.93% argon.
• The remainder, less than 0.1%, contains such trace gases as
water vapor, carbon dioxide, and ozone.
• All of these trace gases have important effects on Earth’s
climate.
• The atmosphere can be divided into vertical layers determined
by the way temperature changes with altitude.
• The layer closest to the surface is the troposphere, which
contains over 80% of the atmospheric mass and nearly all the
water vapor.
• The next layer, the stratosphere, contains most of the
atmosphere’s ozone, which absorbs high-energy radiation from
the sun and makes life on the surface possible

7. Structure and composition of Atmosphere
• Above the stratosphere are the mesosphere and
thermosphere.
• These two layers include regions of charged atoms and
molecules, or ions.
• The upper mesosphere and lower thermosphere are called
the ionosphere, this region is important to radio
communications.
• Because radio waves can bounce off the layer and travel
great distances.
• There is a thought that the present atmosphere developed
from gases ejected by volcanoes.
• Human activities may be affecting the levels of some
important atmospheric components, particularly carbon
dioxide and ozone.

8. Troposphere
• Extends about 12 km from earth
• Troposphere consists of 70% of nitrogen and 21% of
oxygen and small % of other gases
• Solar radiation is the main heat from source from sun
absorbed by ground
• As the altitude increases, the temperature decreases
• The rate at which the temperature decreases is
known as Lapse Rate. (approximately
5 oC/km)
• Tropopause is the top level of troposphere.

9. Stratosphere
• It is the layer just above Troposphere.
• It extends upto 50 km
• Temperature range will be -80 oC to 0 oC from
troposphere to stratosphere
• Increase in temperature is due to absorption of
ultraviolet radiation from the sun by oxygen and
ozone.
• Little amount of water vapour is also present in this
layer.
• Ozone layer is the layer in stratosphere which exists
between 20 km to 40 km above earth’s surface.
• Stratosphere is sometimes called ozonosphere.

10. Stratosphere
• Stratosphere is completely free from clouds
and other forms of weather.
• Polar stratospheric or nacreous clouds are
occasionally seen in lower parts of
stratosphere.
• This is the highest layer that a jet-powered
aircraft can be accessed.

11. Mesosphere
• Third layer from Earth’s surface
• Extends from stratosphere about 50 km to 80 km
from ground surface
• It is the coolest place of earth’s atmosphere.
• Has an average temperature of -85 oC
• Top level of mesosphere is known as mesopause
(just below the mesosphere)
• Mesosphere lies above the maximum altitude for
aircraft and minimum altitude for orbital space craft.
• It can be accessed through the use of rockets only.
• Hence it is poorly understood part of atmosphere.

12. Thermosphere
• It is the zone above the mezopause.
• It extends to an altitude about 80 km upto 500 km of
themopause.
• Height varies considerably due to changes in solar
activity.
• Thermopause lies at the lower boundary of exosphere.
• It is also called exobase.
• Lower part of thermosphere contains many ions and free
electrons.
• Cosmic rays and radiations from the sun produce the
ions.
• Hence this part of thermosphere is called ionosphere.

13. International Space Station
orbits in the layer between
320 and 380 km altitude from
earth’s surface.

14. Exosphere
• Outermost layer of atmosphere beyond the
height of 500 km and above.
• It is a low density, high temperature region
with minimum atomic collisions.
• The layer consists of low density H2 , He and
other heavier molecules such s N2, O2 and CO2
closer to exobase.
• The exosphere is located too far above earth.
• Most of the satelites orbiting the earth are
located in exosphere.

15. Important Air Pollution – Oxides of Sulphur
• SO2 and SO3 are pollutants in oxides of sulphur and SO2 is
harmful one.
• SO2 is an irritant gas, it is a major pollutant emitted from
man-made sources.
• Increases breathing rate and creates O2 deficiency in blood
circulation.
• Ashtma patients are affected very worst due to this pollutant.
• SO2 causes acidity in fog, smoke and also in rain.
• Corrodes the buildings and materials.
• When SO2 reacts with O2 it forms SO3 .
• SO3 dissolves in body fluid and forms H2 SO4
• SO3 + H2 O H2 SO4
• H2 SO4 causes high irritation and causes broncho-spasm.

16. Sources of SO2
• Refineries
• Chemical Plants
• Smelting operations
• Burning of fossil fuels
• Thermal power plants
• Open burning of garbage
• Incineration plants of municipalities

17. Limits of SO2
• Indian Ambient Air Quality Standards define
the 24 hours of concentration of SO2 as 50 –
80 μg/m3 .
Methods to measure SO2
- Modified West-Gaeke’s method
- Ultra-Violet Flourescence method

18. Carbon Monoxide
• It is a colourless, odourless, toxic gas.
• It is produced when organic materials (coal,
wood etc.) burnt incompletely.

19. Sources of CO
• When organic materials burnt completely, the
carbon present is completely oxidised and
forms CO2 .
• Incomplete combustion leads to CO
• Exhausts from automobile are the major
sources of CO

20. Effects of CO
• CO2 replaces O2 present in hemoglobin and
forms carboxy-hemoglobin (COHb )
• If COHb is less, it produces little headache.
• If COHb is high it creates difficulty in
breathing, heart problems etc.
• If COHb is more than 50 % it causes death.
• However, CO is not a permanent pollutant and
COs can be converted into other harmless
compounds.

21. Limits of CO
• Indian Ambient Air Quality Standards define
CO on hourly weighted average basis of 4
mg/m3 .
• Methods to measure CO
- Non-Dispersive Infra-red method (NDIR
method)
- Spectroscopy method

22. Oxides of Nitrogen (NOx)
• During combustion atmospheric nitrogen reacts with
oxygen at high temperature and forms oxides of
nitrogen.
• Oxides of nitrogen are NO (nitric oxide), NO2 and N2
O.
• It is generally expressed as Nox
• Nitric oxide is very harmful pollutant.
• High concentration of nitric oxide causes sudden
death.
• NO2 irritates human eye, nose and creates
discomfort in respiration system.

23. Sources of NOx
• Automobile exhausts
• Incineration plants
• Furnace smokes
• Combustion of fuel at high temperatures
Methods to measure Nox
- Modified Jacab and Hochheiser method
- Gas Phase Chemi-luminescence method

24. Hydrocarbon (HC) and Organic Compounds
• Group of simple compounds consisting of carbon and
hydrogen atoms
• Evaporated from petrol supplies or emitted from
automobile exhaust (when it is not completely burnt)
• Methane (CH4 ) is an important hydrocarbon
produced in nature by decomposition.
• Ambient Air Quality Standards of India sets the limits
on annual concentration of Benzene and Pyrene as 4
μg/m3 and 1 ηg/m3 respectively.

25. Tests for Hydrocarbon
• Benzene
- Gas chromatography based continuous
analyzer method
- Adsorption and desorption followed by GC
analysis method
• Pyrene
- Solvent extraction followed by HPLC / GC
analysis method.

26. Suspended Particulate Matter (SPM)
• Particulate substance present in air may occur in
solid form (dust and smoke) and liquid form (mist,
fog)
• Aerosol is a particle larger than molecule, but small
enough to remain suspended in air.
• Dusts are generated by handling or crushing or
grinding of organic and inorganic materials such as
rock, ore, metal, coal, wood, grain etc.
• Total Suspended Particulate Matter (TSPM) is the
particles include both solid and liquid particles of
suspended particulate matter.

27. Sources of SPM in Air
• By natural process like wind, pollen and pores,
volcanic eruption, decomposition of organic
materials.
• Human activities of mining, boring of fossil fuels etc.
Tulip anther with many grains
of pollen

28. Effects of SPM
• Larger particles (size more than 10 μ) will be trapped
by hair and present in lining of nose.
• Particles from 5 μ to 10 μ are also trapped by musus
and they sent back by spitting and swallowing.
• Less than 5 μ reach lungs and cause the following
defects.
- Damages lung tissues
- Causes asthma, bronchitis
- Causes cancer

29. SPM
• Smaller particles having size upto 10 μ are called
Respiratory Suspended Particulate Matter (RSPM) of
PM10
• upto 2.5 μ are called PM2.5
• Latest Ambient Air Quality Standards of India limited
the annual concentration of PM10 and PM2.5 as 60
μg/m3 and 40 μg/m3 respectively.
• Microscopic particulate materials cause allergic
reaction.
• Sneezing is one of the symptoms of allergy.

30. Lead
• Emitted all automobiles
• As per Indian Air Quality Standards a maximum of 5
μg/m3 is permitted as annual concentration of lead
in air.
Measuring methods of Lead
- ED – XRF (Using Teflon filter method)
- AAS/ICP Method

31. Other Pollutants – Smoke
• Smoke – Resultant incomplete combustion of
carbonaceous materials like coal, oil, tar and
tobacco.
• Consists of carbon particles less than 0.1 μm
in diameter.
• May be condensation aerosol with solid and
liquid particles.

32. Other Pollutants
• Fog – Aerosol of liquid droplets near the grounds as
distinct from clouds.
• Fumes – Solid particles generated by condensation
from gaseous state, after volatilization of from
molten metals.
• Mist – Suspended liquid droplets generated by
condensation from gaseous to liquid state or solid
state
• Smog – Mixture of smoke and fog
• Haze – Suspension of small particles in air which
makes distinct large objects indistinct.

33. Physical Effect of Air Pollution
• Effects on Visibility
• Effects on urban atmosphere and climate
changes
• Effects on atmospheric constituents

34. Effects on Visibiliy
• Visibility depends on transmission of light through
atmosphere and capacity of eye to differentiate the
object.
• Visibility can be reduced by pollutants in air depends
on following.
- Size, concentration and physical of particulate matter
- Nature of particulate matter in ambient air
- Volume of air into which it gets mixed up

35. Effects on Urban Atmospheric and Weather
Conditions
• Urban air pollution may be caused due to
- Smoke
- Dust
- Other aerosols
- Due to air pollution, solar radiation is reduced
by 36%

36. Effects of Atmospheric Constituents
• Main source of organic carbon in bio-sphere is
atmospheric CO2
• Due to combustion of fuels, atmospheric CO2
is increased rapidly.
-CO2 increases ambient temperature
- Increases infra-red absorption
- Increases green house effect

37. Effect of air pollution on human health
• Particles of small size 5 μ penetrate human
lungs and deposited.

38. Effect of air pollution on human health
S. No. Air Pollutant Properties Sources Effects on
human health
1 SO2 Colourless gas Combustion of
fuels
Breathing
prohlems
Lung disease
and death
Asthma
Problem
2 CO2 Colourless and
odourless gas
Incomplete
combustion of
fuels
Cardio-vascular
disease
Visual
perception
Mental
disability
Headache
Photochemical
smog

39. Effect of air pollution on human health
S. No. Air Pollutant Properties Sources Effects on
human health
3 NOx Reddish brown gas
Highly reactive
Thermal power
stations
Automotives
Formation of
ozone
Irritation in
lungs and nose
Possibility of
viral attacks
4 CO2 Colourless gas Combustion of
coal, diesel and
petrol
Climate
changes
Global
warming
Green house
effect
5 SPM Solid particles (dust and
smoke)
Liquid particles (mist
and fog)
Smoke from
agencies
Burning of
garbage
Other burnings
Breathing
effects
Lung disease
Cardio-vascular
disease

40. Effect of air pollution on human health
S. No. Air Pollutant Properties Sources Effects on human
health
6 Head (heavy
metal)
Colourless Vapour Leaded petrol in
automobiles
Consumed with
the food, water,
soil or dust
Mental retardation
Behavioural
disorders
Increases blood
pressure
Heart diseases
7 Ozone (O3 ) Colourless gas Secondary
pollutant
produced by
photochemical
reaction
Reduces long
functions
Creates cough,
sneezing, chest pain
Affects respiratory
system
8 Nuclear wastes Invisible
radioactive
emissins
Nuclear weapon
testing
Nuclear power
plants
Cancer
Mutations, death

41. Effects of Air pollution on Plants
• Pollutant cause effect on plant is Flourine.
• Flourine is mixed with air by
- Manufacturing process of Aluminium, Glass
and phosphate fertilisers
- Clay baking operations

42. Effects of Air pollution on Plants
• Reduces yield crop
• Reduces photosynthesis of plant
• Reduces quantities and nutrients in vegetable,
fruits etc.
• Creates harmful effect on animals and human
health, who use the affected plants.

43. Effects of Air-pollution on Animals
• The important pollutants of animals are,
- Flolurine
- Reduces milk production
- Lack of appetite
- Ill-health
- Reduced fertility
- Growth reduction

44. Effects of Air-pollution Materials and Services
• Corrosion
• Chemical attack
• Abrasion
• Deposition and removal

45. Effects of Air Pollution on Materials
S. No. Air Pollutant Other factors Materials Effects
1 SO2 , Acids and Gases With moisture Building
materials
Colour
deformation
2 SO2 , Acids and Gases With moisture
and
temperature
Building
materials
Tamishing of
surface
Losses of
material
3 SO2 , Acids and Gases With sunlight
and moisture
Paper Embrittlement
4 SO, Acids and Gases With moisture
and sunlight
Textiles Reduction in
tensile strength
5 Oxidants With sunlight Rubber Reduction in
tensile strength
6 SO2 , H2 S and SPM With sunlight
moisture and
fungus
Paints Cracking
Colour
deformation

46. Economic Effects on Air Pollution
• Wastage of fuel through improper combustion
• Vegetation and planting damaged due to pollutants such as
smog, dust etc.
• Non repairable damages to art-treasures of country
(Tajmahal, Colosseum in Rome, San Marco Basilica in Venice
show decay)
• Low power electrical conduits sensitive with air pollution lead
to malfunctioning of equipment
• Paper industry is affected. Paper becomes brittle and difficult
to fold due to the effect of SO2.
• Additional lighting required to improve visibility. Power loss.
• Glass materials and ceramic materials are highly affected to
air pollution.

47. Economic Effects on Air Pollution
• Leather industries and rubber tyred wheels
get cracked, due to contact with atmospheric
pollutants.

48. Effects of Nuclear Power Reactors
• Nuclear reactors doesn’t produce air pollution.
• Nuclear reactors doesn’t produce carbon di oxide.
• Emissions from fossils fuels while burning pollute the
atmosphere.
• Nuclear wastes from radio active emission cause
cancer.
• Nuclear waste cause mutation, death.
• Nuclear weapon testing, nuclear operation of nuclear
reactors needs skill and practice.
• Nuclear reactors are operated in controlled manner.

49. Acid Rain
• Rain pH value equal to or less than 5.6 has harmful effects on
humans, animals, plants, aquatics and infrastructure.
• Normal rain has the pH value of 6.9 (little acidic), when
atmosphere is free.
• When concentration of SOx, NOx, CO2 increase in atmosphere,
the rain water becomes more acidic.
• Sometimes, pH value may be less than 5 or 4.
• The primary pollutant which causes 2/3 of the acid rain is SO2.
• SO2. produced by the burning of coals and oils largely used
for generation of heat and power in industries and domestic
uses.

50. Ozone Depletion
• Reduction of thickness of ozone layer due to attach
of chemical pollutants.
• Ultraviolet radiation are highly harmful to all kinds of
life on earth.
• If UV rays are not filtered, it creates impacts to
human, animals and plants.
• Extreme effect of UV radiation is mutation of DNA
• Skin cancers, deadly melenoma.

51. Causes of Ozone Depletion
• Use of CFCs
• Nuclear tests
• Supersonic transports, rockets and space
shuttles
• Nitrogeneious fertilizers

52. Ozone Hole
• Ozone layer is also known as ozone depletion
• Thickness of ozone layer is less than 150 DU (Dobson
Unit) (1 DU = 0.01 mm)
• Ozone hole may permit the UV radiation to reach the
earth.
• UV radiations are highly harmful.
• The maximum area covered by ozone hole was found
about 30 million km2 in September 2000.

53. Global Warming
• Increase of earth’s average temperature due to effect of green
house gases.
• Green houses are from burning of fossil fuels or deforestation.
• Global warming is a type of green house effect.
• The climate of earth is influenced by 10 to 12 km from earth’s
surface.
• During past few years, earth’s climate has been changed to
be getting hotter and hotter year after year.
• If earth is viewed from space, the climate layer of atmosphere
would be a thin layer like a skin or an onion.
• Earth is surrounded by gaseous cover and atmosphere
provides oxygen to living things and maintains heat balance
on earth.

54. Gases Cause Global Warming
• Carbon dioxide (CO2 )
• Methane (CH4)
• Nitrogen oxides (NOx)
• Chloro – Fluro – Carbon (CFC)

55. Air Quality Standards
• Assesses current or historical air quality
• Develop long term air management stragegies
and evaluate the progress
• Air regulatory development
• Guide decisions for permitting of new or
modified facilities

56. Steps in Air Quality Standards
• Prepare the air quality criteria
• Air Quality criteria indicates the relationship
between pollutant concentrations in the air. It
is also called as Guide.
• Develop quality goals from quality criteria.
• Complete elimination of air pollution is not
possible practically.
• Some level of pollutants are permitted in
atmosphere.

57. Ambient Air Quality Standards
• Legal limits placed on the concentration of air pollutants in a
community where the people and things are exposed.
• First Ambient Air Quality Standards was adopted by Central
Pollution Control Board (CPCB) during 1982.
• Agencies responsible for air quality standards are Central
Pollution Control Board (CPCB) and State Pollution Control
Board (SPCB).
• Both CPCB and SPCB are functioning under Ministry of
Environment and Forest (MoEF)

58. Annual Time Weighted Average
• Arithmetic mean of minimum 104 measurements in
a year of a particular site taken twice a week 24
hourly at uniform intervals.
• 24 hourly or 8 hourly or 1 hourly monitored values as
applicable shall be complied with 98% of the time in
a year.

59. Other Air Quality Standards
• Point of Impingement Standards
• Soiling Index
• Odour Standards
• Visibility Standards
• Standards for Particulate Matter Deposited

60. Emission Standards
• Emission standards are applicable for all national ,
regional and local emitters.
• Emission standards are designed to protect human
life.
• Emission intensity is the emission rate of a given
pollutant relative to the intensity of specific activity
such as industrial production process.
• Types of emission standards
- Emission standards for Mobile standards
- Emission standards for stationary sources

61. Emission Sources for Mobile Sources
• Mobile sources are ships, aircraft, automobile, locomotives in
rails.
• Bharath Stage Emission standards instituted by Govt. of India
is to regulate the pollutants for motor vehicles.
• The standards are set by CPCB under MoEF.
• The standards based on European standards were established
in 2000.
• Progressively stringent norms have been rolled out.
• Till 2014 the country was under the combination of Euro 3
and Euro 4
• Euro 6 norms are planned by April 2020

62. Emission Standards for Stationary Sources
• Stationary site
• Stack
• Chimney
The emission standards also include
• Buffer zones
• Stack height
• Design of equipment
• Fuel composition

63. Sampling Analysis
• To measure quality and quantity of pollutant
• To determine the effect of emissions through out the
year
• To know the nature of source of pollutant
• To determine the effect of emission in different zones
• To estimate single pollutant and multiple pollutant
sources
• To determine the method fo control of air pollution
• To implement the local air pollution control system

64. Air Sampling Analysis
• Gas composition analysis
• Moisture content determination
• Temperature analysis
• Pressure and velocity analysis

65. Concentration of Air Pollutants

66. Methods of Sampling
• Sedimentation
• Filtration
• Impingement methods
• Electrostatic precipitation
• Thermal precipitation
• Centrifugal methods
• Solution impinger

67. Sedimentaion
• Simplest method of sampling
• Adopted for particles whose diameter exceeds
10μ
• Can be sampled by placing in open container
• Sedimentation collectors are made up of glass,
stainless steel and polyethylene

68. Filtration
• Used for dust particles less than 10μ
• Particles less than 10μ are known as suspended particles.
• Suspended particles are removed quantitatively from gas
stream flowing through dense material.
• Result of filtration process depends upon filter material.
• The following factors are to be considered for selecting filter
material.
- Type of particulates to be collected
- Chemical nature of filter
- Efficiency of collection

69. Impingement Methods
• Separation of particulates from a gas-stream by collision
against a flat surface.
• The instruments used are
- Dry impinger
- Wet impinger
Dry Impinger
- Also known as impactors
- Collection of particles by impaction on dry
surface
Wet Impinger
- Collection of particles by impinging them on a liquid sub-
merged surface.

70. Thermal Precipitation
• Gas containing suspended particles brought into
contact with hot surface.
• Dust free space developed between surface an
particles.
• It is due to the thermal force of action.
• It causes particles to migrate from high temperature
zone to low temperature zone.
• Great range of particle size of 0.01 μ to 10 μ
• Low sampling rate of 0.02 to 0.2 litres/min.
(Disadvantage)

71. Electrostatic precipitation
• The gas passes between two electrodes charged to a
potential difference of 10 to 40 kV.
• The electric discharge between the electrodes will
emit electrons and ions from negative electrode.
• It will be drawn towards the positive electrode.
• Particles are separated from the gas stream.
• Collection of 100% particles over a reasonable length
is possible.
• Particle diameter ranges from 0.2 μ to 10 μ.

72. Centrifugal methods
• It works on the principle of cyclone.
• Dust laden air is directly tangentially to a
cylindrical chamber, in which it forms a vortex.
• The centrifugal force drives the suspended
particles to the wall of cyclonic body.
• From the cyclonic body, the dusts drop into
the collection chamber.
• An axial outlet is provided for the clean gas.

73. Thank you
Dr A R Pradeep Kumar, B.E., M.E., Ph.D.
Professor and Head/Mech.
Dhanalakshmi College of Engineering, Chennai
email : dearpradeepkumar@gmail.com
99 41 42 43 37