This document provides an overview of air pollution. It defines pollution and describes different types including air, water, noise, soil, and radioactive pollution. Major sources of air pollution are described such as industries, vehicles, and the burning of fuels. Specific air pollutants like carbon monoxide, sulfur dioxide, nitrogen oxides, lead, and particulate matter are examined in terms of their sources and effects. Methods to control vehicle and industrial emissions like catalytic converters and regulations like emission standards in the US, Europe, and over time are summarized. The health and environmental impacts of air pollution are also reviewed.

1. Unit-5 Air Pollution
Prepared by:
Ankur Sachdeva
Assistant Professor, ME

2. What is Pollution
• Pollution is the introduction of contaminants into
the natural environment that cause adverse
change, in the form of killing of life, toxicity of
environment, damage to ecosystem and
aesthetics of our surrounding.
• An unwanted change in the environment which
involves the physical, biological and chemical
changes involving air, water and land which
affects the human life in one way or the other”.

3. Contamination by Industries

4. Pollution is Everywhere!!!

5. Broader View of Pollution

6. Types of Pollution
• Air Pollution.
• Water Pollution.
• Noise Pollution.
• Littering (spilling of oils in oceans)
• Soil contamination (by lead, heavy metals)
• Radioactive contamination.
• Thermal pollution.
• Visual Pollution.

7. Air Pollution
• Air pollution is contamination of the indoor or
outdoor environment by any chemical,
physical or biological agent that modifies the
natural characteristics of the atmosphere.

8. Sources of Air Pollution

9. Types of Pollutants

10. Sources of Air Pollution from
Burning of fuels
• Sources of air pollution from burning fuels are
classified as follows:
– Stationary sources, mainly consisting of boilers,
furnaces and gas turbines
– Mobile sources consisting of transport means, whose
internal combustion engines are diesel (diesel-
consuming, also called compression-ignition engines)
and spark ignition engines, consuming gasoline.
– Lately there are used as stationary sources in heat
energy and electricity production in cogeneration and
internal combustion engines

11. Pollutants From Combustion
• Combustion pollutants are the gases and
particles made by burning any fuel, such as
wood, natural gas, kerosene, charcoal,
or tobacco.
• Gases released from combustion:
– CO2, SO2, H2O, N2, O2, CO, NOx, PAHs (polycyclic
aromatic hydrocarbons), VOCs (volatile organic
compounds), dioxins

12. Carbon Dioxide
• Carbon dioxide is the principal product of combustion of
fossil fuels since carbon accounts for 60–90 percent of the
mass of fuels that we burn.
• China has emerged as the largest single emitter of energy-
related CO2 emissions, reaching an all-time high of 8320
million metric tons of carbon dioxide in 2010.
• The United States emitted about 5610 million metric tons in
2010.
• The chart below shows the trend in carbon dioxide
emissions from 1980.
• For Asia and Oceania, and particularly for China and India,
emissions can be seen to have increased significantly in the
past two decades.

15. Carbon Monoxide
• Carbon monoxide, or CO, is a colorless, odorless gas that is formed
when carbon in fuel is not burned completely.
• Carbon Monoxide is a component of motor vehicle exhaust, which
contributes about 55 percent of all CO emissions nationwide.
• Other non-road engines and vehicles (such as construction
equipment and boats) contribute about 22 percent of all CO
emissions nationwide.
• Higher levels of CO generally occur in areas with heavy traffic
congestion. In cities, 85 to 95 percent of all CO emissions may come
from motor vehicle exhaust.
• Other sources of CO emissions include industrial processes (such as
metals processing and chemical manufacturing), residential wood
burning, as well as natural sources such as forest fires.
• Woodstoves, gas stoves, cigarette smoke, and unvented gas and
kerosene space heaters are sources of CO indoors.

16. Sources of Carbon-Monoxide

17. Sulphur-Dioxide
• Sulfur dioxide, or SO2, belongs to the family of
sulfur oxide gases (SOx).
• These gases dissolve easily in water.
• Sulfur is prevalent in all raw materials, including
crude oil, coal, and ores that contain common
metals, such as aluminum, copper, zinc, lead, and
iron.
• SOx gases are formed when fuel containing sulfur,
such as coal and oil, is burned, and when gasoline
is extracted from oil, or metals are extracted from
ore.

18. Sources of Sulphur Dioxide

19. Nitrogen Oxides
• Nitrogen oxides, or NOx, is the generic term for a
group of highly reactive gases, all of which
contain nitrogen and oxygen in varying amounts.
• Many of the nitrogen oxides are colorless and
odorless.
• Nitrogen oxides form when fuel is burned at high
temperatures, as in a combustion process.
• The primary sources of NOx are motor vehicles,
electric utilities, and other industrial, commercial,
and residential sources that burn fuels

20. Sources of NOx

21. Lead
• The major sources of lead emissions have
historically been motor vehicles (such as cars and
trucks) and industrial sources.
• Due to the phase-out of leaded gasoline, metals
processing is the major source of lead emissions
to the air today.
• The highest levels of lead in air are generally
found near lead smelters (devices that process
lead ores).
• Other stationary sources are waste incinerators,
utilities, and lead-acid battery manufacturers.

22. Particulate Matter
• Particulate matter (PM) is the general term used to
describe a mixture of solid particles and liquid droplets
found in the air.
• Some particles are large enough to be seen as dust or dirt.
• Others are so small they can be detected only with an
electron microscope.
• Different sizes of Particles include:
– PM 2.5 describes the “fine” particles that are less than or equal
to 2.5 µm (micro meter) in diameter.
– “Coarse fraction” particles are greater than 2.5 µm, but less
than or equal to 10 µm in diameter.
– PM 10 refers to all particles less than or equal to 10 µm in
diameter (about one-seventh the diameter of a human hair).
PM can be emitted directly or formed in the atmosphere.

23. Sources of Particles
• "Primary" particles are formed from combustion
sources and are emitted directly into the
atmosphere.
– Examples of primary particles are dust from roads or
black carbon (soot).
• "Secondary" particles are formed in the
atmosphere from primary gaseous emissions.
– Examples of secondary particles are sulfates formed
from SO2 emissions from power plants and industrial
facilities; nitrates formed from NOx emissions from
power plants, automobiles, and other combustion
sources; and carbon formed from organic gas
emissions from automobiles and industrial facilities.

24. Pollutions from Mobile Sources

25. Vehicular Population in India

26. Principal Engine Emissions
All IC engines produce undesirable emissions as a result of
combustion, including hydrogen fuelled engines.
Other engine emissions include aldehydes such as
formaldehyde and acetaldehyde primarily from the
alcohol fuelled engines, benzene and polyaromatic
hydrocarbons (PAH).

27. Sources of Emissions in SI Engine
• Engine Exhaust
• Crankcase blow by and
• Fuel evaporation from fuel tank and fuel system

28. Emission Formation in SI Engines

29. SI Engine Emissions
SI engine vehicles without emission control have three
sources of emissions
CI engines on the other hand release all of harmful emissions
into atmosphere through its exhaust gases

30. Sources of Emissions in CI Engine

31. Emission Formation in CI Engines

32. Hydrocarbon Emission Sources
in C.I. Engines
• Over-mixing of fuel and air –
– During the ignition delay period
evaporated fuel mixes with the
air, regions of fuel-air mixture
are produced that are too lean
to burn.
– Some of this fuel makes its way
out the exhaust. Longer ignition
delay more fuel becomes over-
mixed.
• Under-mixing of fuel and air –
– Fuel leaving the injector nozzle
at low velocity, at the end of the
injection process cannot
completely mix with air and
burn

33. Emission Formation in CI Engines

34. Typical Exhaust Emission
Concentrations
SI Engine (Gasoline fuelled)
Depending upon engine operating conditions without catalytic control
engine out emissions range :
*ppmc1= parts per million as methane measured by Flame Ionization
Analyzer/Detector(FIA or FID)
CO emissions are high under engine idling and full load operation
when engine is operating on fuel rich mixtures.
HC emissions are high under idling, during engine warm-up and light
load operation, acceleration and deceleration.
NOx are maximum under full engine load conditions.

35. Typical Exhaust Emission
Concentrations
CI (Diesel) Engines
Diesel engines usually operate with more than 30% excess air and the
emissions are accordingly influenced.

36. Effects of Air Pollution
• Green House Effect
– Global Warming
– Climate Change
• Smog
• Acid Rain
• High Altitude Ozone
• Health Effects

37. The Sun’s energy
passes through the
car’s windshield.
This energy (heat)
is trapped inside
the car and cannot
pass back through
the windshield,
causing the inside
of the car to warm
up.
Example of the
Greenhouse Effect

38. Difference
GLOBAL WARMING
is the increase of the
Earth’s average surface
temperature due to a
build-up of greenhouse
gases in the
atmosphere.
CLIMATE CHANGE
is a broader term that
refers to long-term
changes in climate,
including average
temperature and
precipitation.

39. How Global Warming Works
Fossil fuels (coal, oil, natural gas)
Carbon Dioxide (CO2)

40. Global Atmospheric Concentration
of CO2

41. Carbon Dioxide and Global Warming
Carbon dioxide (CO2) is an emission that is not regulated but is one of the
primary greenhouse gases, water vapour and methane are the others,
believed to be responsible for global warming.
Global warming occurs because the greenhouse gases are transparent to
the high frequency solar radiation that heat up the earth’s surface but
absorb the lower frequency radiation from the earth’s surface.

42. Acid Rain

43. Acid Rain
• Acid rain describes any form
of precipitation that
contains high levels of nitric
and sulfuric acids.
• It can also occur in the form
of snow, fog, and tiny bits of
dry material that settle to
Earth.
• Normal rain is slightly acidic,
with a pH of 5.6, while acid
rain generally has a pH
between 4.2 and 4.4

44. Photochemical Smog

45. Photochemical Smog
• Photochemical smog is a brownish-gray haze resulting
from the reactions caused by solar ultraviolet radiations
between hydrocarbons and oxides of nitrogen in the
atmosphere

46. Ground Level Ozone
• Ground-level ozone is one of the major components of
photochemical smog. It is a secondary pollutant, meaning that it is
not directly emitted.
• Instead, it is produced when carbon monoxide (CO), methane, or
other volatile organic compounds (VOCs) are oxidized in the
presence of nitrogen oxides (NOx) and sunlight.
• In addition to their role as ozone precursors, CO, VOCs and NOx are
dangerous air pollutants themselves.
• Major sources of NOx and VOCs include emissions from motor
vehicle exhaust, industrial facilities, and chemical solvents.
• Major sources of methane include waste and the fossil fuel and
agricultural industry.
• Effects of Ground Level Ozone
– Leads to breathing problems, asthma, reduced lung function and
respiratory diseases.
– Aside from its health impacts, tropospheric ozone is a short-lived
climate pollutant and one of the most important greenhouse gases.

47. PM and its effects
• Particulate Matter (PM):
– Particulate matter (PM) are inhalable and respirable
particles composed of sulphate, nitrates, ammonia,
sodium chloride, black carbon, mineral dust and
water.
– Effects of Particulate Matter (PM):
– Particles with a diameter of less than 10 microns
(PM10), including fine particles less than 2.5 microns
(PM2.5) pose the greatest risks to health, as they are
capable of penetrating people’s lungs and entering
their bloodstream.

48. Black Carbon
• Black carbon is a major component of PM2.5 and
driver of climate change, also known as a “short-
lived climate pollutant.“
• SLCPs persist in the atmosphere for a shorter
period compared to CO2.
• Effect of Black Carbon
– Despite its short atmospheric lifetime, black carbon is
one of the largest contributors to global warming after
CO2.
– It also known to decrease agricultural yields and
accelerate glacier melting.

49. Health Effects of Air Pollutants

50. Control of Evaporative Emissions
• When engine is running, the vacuum
created in the intake manifold is used
to draw fuel vapours from the canister
into the engine.
• Purging air is sucked through the
canister which leads the fuel vapours
from canister to the engine.
• An electronically controlled purge
valve is used.
• During engine acceleration additional
mixture enrichment can be tolerated
and under these operating conditions
the stored fuel vapours are usually
purged into the intake manifold.
• This system is a fully closed system.
• A sealed fuel tank filler cap is used and
a stable fuel tank pressure is
maintained by the purging process of
the canister.

51. Positive Crankcase Ventilation
• Blowby must be removed
from the engine before it
condenses in the
crankcase and reacts with
oil, which forms sludge.
• Sludge will corrode and
accelerate the wear of
piston rings, valves,
bearings and other parts of
the engine.
• To prevent this pollution,
modern engines employ
closed or PCV system, in
which blowby is sent back
into the cylinder.

52. Control of Exhaust Emissions
• Two categories:
– Combustion modifications
– Exhaust after-treatment

53. Combustion Modification
• Reduction in HC and CO formation
– Increasing the exhaust gas temperature
– More oxygen in the exhaust
– Lesser mass in the quench region
– More time for reaction
• Reduction in NOx formation
– Decreasing the combustion temperature- EGR
– Decreasing the availability of oxygen

54. Exhaust Gas Recirculation (EGR)
• In internal combustion engines, exhaust gas
recirculation (EGR) is a nitrogen oxide (NOx) emissions
reduction technique used in petrol/gasoline and diesel
engines.
• EGR works by recirculating a portion of an engine's exhaust
gas back to the engine cylinders.
• This dilutes the O2 in the incoming air stream and provides
gases inert to combustion to act as absorbents of
combustion heat to reduce peak in-cylinder temperatures.
• NOx is produced in high temperature mixtures of
atmospheric nitrogen and oxygen that occur in the
combustion cylinder, and this usually occurs at cylinder
peak pressure.

55. Exhaust Gas Recirculation (EGR)

56. Exhaust After-Treatment
• Thermactor or Air Injection System
• Thermal reactor,
• Catalytic converter,
• Particulate trap

57. Three Way Catalytic Converter
• A three-way catalyst oxidizes exhaust gas pollutants - both
hydrocarbons (HC) and carbon monoxide (CO) - and reduces
nitrogen oxides (NOx) into the harmless components water (H2O),
nitrogen (N2) and carbon dioxide (CO2).
• Three catalysts are used: Platinum, Palladium and Rhodium.
• Platinum and Palladium removes CO and HC whereas Rhodium is
used to remove NOx emissions

58. Emission Standards

59. Emission Standards
• Emission standards are requirements that set specific
limits to the amount of pollutants that can be released
into the environment.
• Many emissions standards focus on regulating
pollutants released by automobiles (motor cars) and
other powered vehicles but they can also regulate
emissions from industry, power plants, small
equipment such as lawn mowers and diesel generators.
• Vehicle emission performance standard:
An emission performance standard is a limit that sets
thresholds above which a different type of emission
control technology might be needed.

60. Implementation Timeline of
Global Emissions Standards

61. Emission Standards in US
• In the United States, emissions standards are
managed by the Environmental Protection Agency
(EPA).
• The state of California has special dispensation to
promulgate more stringent vehicle emissions
standards, and other states may choose to follow
either the national or California standards.
• California's emissions standards are set by the
California Air Resources Board, known locally by its
acronym "CARB".
• Given that California's automotive market is one of the
largest in the world, CARB wields enormous influence
over the emissions requirements that major
automakers must meet if they wish to sell into that
market.

63. European Emission Norms
• Although emissions regulations date back to 1970, the first
EU-wide standard – known as Euro 1 – wasn’t introduced
until 1992, which saw catalytic converters became
compulsory on new cars, effectively standardizing fuel
injection.
• Since then, there have been a series of Euro emissions
standards, leading to the current Euro 6, introduced in
September 2014 for new type approvals and rolled out for
the majority of vehicle sales and registrations in September
2015.
• The regulations, which are designed to become more
stringent over time, define acceptable limits for exhaust
emissions of new light duty vehicles sold in EU and EEA
(European Economic Area) member states.

65. Bharat Stage Norms
• Bharat stage emission standards (BSES) are
emission standards instituted by the Government
of India to regulate the output of air pollutants
from internal combustion engines and Spark-
ignition engines equipment, including motor
vehicles.
• The standards and the timeline for
implementation are set by the Central Pollution
Control Board under the Ministry of Environment
& Forests and climate change.

66. Bharat Stage Norms
• The first stage of mass emission norms came into force for petrol
vehicles in 1991 and in 1992 for diesel vehicles.
• From April 1995, mandatory fitment of catalytic converters in new
petrol passenger cars sold in the four metros, Delhi, Calcutta,
Mumbai and Chennai along with supply of Unleaded Petrol (ULP)
was affected.
• In the year 2000, passenger cars and commercial vehicles met Euro
I equivalent India 2000 norms, while two wheelers were meeting
one of the tightest emission norms in the world.
• Euro II equivalent Bharat Stage II norms were in force 2001 onwards
in Delhi, Mumbai, Chennai and Kolkata.
• The first Auto Fuel Policy was announced in August 2002 which
layed down the Emission and Fuel Roadmap upto 2010.
• As was given in the roadmap, four-wheeled vehicles moved to
Bharat Stage III emission norms in 13 metro cities from April 2005
and rest of the country moved to Bharat Stage II norms.

67. Bharat Stage Norms
• In 2016, the Indian government announced that the country would
skip the BS-V norms altogether and adopt BS-VI norms by 2020.
• While the norms help in bringing down pollution levels, it invariably
results in increased vehicle cost due to the improved technology &
higher fuel prices
• Currently, BS VI norms have been enforced across the country since
1st April 2020.
• However, recently the Supreme Court of India ordered barring of
sale of Bharat Stage IV vehicles from April 1, 2020.
• In 2014, Saumitra Chaudhary committee gave recommendations on
Auto Fuel Vision Policy 2025 which had recommended
implementation of BS-IV (2017), BS-V (2019) and BS-VI (2024)
standards.

68. Implementation of BS Norms

69. Major Differences in BS VI
• Selective Catalytic Reduction Technology-
– It reduces oxides of nitrogen by injecting an aqueous urea
solution into the system.
– Hence, NOx from diesel cars can be brought down by nearly
70%.
– In the petrol cars, they can be reduced by 25%.
• Sulphur Content- While the BS-IV fuels contain 50 parts per
million (ppm) sulphur, the BS-VI grade fuel only has 10 ppm
sulphur content.
• Particulate Matter- in diesel cars will be reduced by 80%.
• Mandatory on-board diagnostics (OBD)- which inform the
vehicle owner or the repair technician about how efficient
the systems in the vehicles are.
• RDE (Real Driving Emission) will be introduced for the first
time that will measure the emission in real-world conditions
and not just under test conditions.