Air Pollution

Air Pollution
Lectured By-
Dr. Rajendra Singh Thakur

Air pollution :Definition
 The presence of one or more chemicals in the atmosphere in
sufficient quantities and duration to cause harm to humans etc.
Dr. Rajendra Singh Thakur 2
or
 Excessive discharge of undesirable foreign substances into the
atmospheric air thereby adversely affecting the quality of air and
causing damage to human, plants and animal lives.
 Air pollution is the introduction into the atmosphere of chemicals,
particulates, or biological materials that cause discomfort, disease, or
death to humans, damage other living organisms such as food crops,
or damage the natural environment or built environment.

Air Pollution
 Air pollution results from human activities such as burning fossil
fuels (oil, coal, and gasoline) to create electricity and power
automobiles, and manufacture industrial products such as
chemicals and plastic.
 The air pollutants are particulates, HC, CO2, CO, NO, NO2, SO3
--
source may be industrial, autos, etc.
 The increased carbon dioxide in the atmosphere contributes to the
warming of the global climate, the so-called "greenhouse effect."
 The increased Chloro-fluoro-carbons in the atmosphere has been
depleting stratospheric ozone.

Sources of Air Pollution
 Natural:
1. volcanoes, fumaroles and hot springs
2. decay from marshes, bogs
3. increase ozone due to thunderstorms, fires.

Man made
(most severe for human health):
 Stationary sources - those that are fixed in
location.
1. Point sources e.g. smoke stacks, 14% air pollution from plants
generating electricity;
2. Fugitive sources e.g. construction sites, exposed areas;
3. Area sources e.g. dense urban community or agricultural area
 Mobile sources - those that move while polluting,
e.g. trucks, cars, busses etc. 60% of air pollution from motor
vehicles. 80-88% in major cities!

CLASSIFICATION OF
AIR POLLUTANTS?

(a) According to Origin
 Primary Air Pollutants: those emitted directly into the air. The main primary
pollutants known to cause harm in high enough concentrations are the following:
1. Carbon compounds, such as CO, CO2, CH4, and VOCs
2. Nitrogen compounds, such as NO, N2O, NO2 and NH3
3. Sulfur compounds, such as H2S and SO2
4. Halogen compounds, such as chlorides, fluorides, and bromides
5. Particulate Matter (PM or “aerosols”), either in solid or liquid form, which is
usually categorized into these groups based on the aerodynamic diameter of the
particles.
 Secondary Air Pollutants: those that form as a result of a chemical reaction of the
primary pollutant with a natural component of the environment. The main secondary
pollutants known to cause harm in high enough concentrations are the following:
1. NO2 and HNO3 formed from NO
2. Ozone (O3) formed from photochemical reactions of nitrogen oxides and VOCs
3. Sulfuric acid droplets formed from SO2 and nitric acid droplets formed from NO2
4. Sulfates and nitrates aerosols (e.g., ammonium (bi) sulfate and ammonium
nitrate) formed from reactions of sulfuric acid droplets and nitric acid droplets
with NH3, respectively
5. Organic aerosols formed from VOCs in gas-to-particle reactions.

Primary pollutants
 The poisonous gases and
undesirable chemicals which
cause air pollution.
 Carbon particles from
unburned fuel,
 Ammonia (NH3),
 Sulphur dioxide (SO2),
Hydrocarbons,
 Oxides of nitrogen,
 Oxides of carbon,
 Lead.
Secondary pollutants
 Derived from Primary Air
Pollutants
 In bright sunlight nitrogen,
nitrogen oxides, oxygen and
hydrocarbons –
photochemical reaction –
powerful oxidants – Ozone,
Aldehydes, Sulphuric acid,
Peroxy acetyl nitrate (PAN),
Peroxides, etc.
 They form photochemical
Smog

(b) According to Chemical Composition
 Organic Pollutants: e.g
 Hydrocarbons.,
 Aldehydes,
 Ketones,
 Amines and
 Alcohals
 Inorganic Pollutants: :
 Carbon compounds (e.g. CO and Carbonates)
 Nitrogen compounds (e.g. Nox and NH3)
 Sulphure compounds (e.g. H2S, SO2, SO3 and H2SO4)
 Halogen compounds (e.g. HF, HCl and metalic fluorides)
 Oxidizing agents (e.g. O3)
 Inorganic particles (e.g. flyash, silica, asbestos and dusts from transport,
mining, metallurgical and other industrial activities)

(c) According to State of matter
 Gaseous pollutants: which get mixed with the air and do not
normally settleout : e.g
 CO,
 NOx, and
 SO2
 Particulate pollutants: which comprise of finally divided solids or
liquids and often exist in colloidal state as aerosols e.g.
 Smoke,
 fumes,
 dust,
 mist,
 fog,
 smoge and sprays.

Biochemical effects of some important air pollutants
 Sulfur oxides (SOx)
 Colorless, odorless gas.
 Particulates of SO4 which combines with water to form acid rain.
 Toxic to plants and animals; paint damage.
 Sulfur oxide refers to many types of sulfur and oxygen containing compounds.
 Sulfur oxide (SOx) refers to one or more of the following:
1. Lower sulfur oxides (SnO, S7O2 and S6O2)
2. Sulfur monoxide (SO)
3. Sulfur dioxide (SO2)
4. Sulfur trioxide (SO3)
5. Higher sulfur oxides (SO3+x where 0<x≤1)
6. Disulfur monoxide (S2O)
7. Disulfur dioxide (S2O2)
 Biochemical effects:
 Sulphur dioxide irritates respiratory tissues and chronic exposure
causes bronchitis.
 Sulphur dioxide also reacts with water, oxygen and other materials to
form sulphur containing acids – The acids can become attached to
particles which when inhaled are very corrosive to the lung.

 Nitrogen oxides, (NOx)
 Nitric oxide and nitrogen dioxide NO2,
 NO2 yellow brown to reddish gas.
 (NOx) Converted to nitrates in atmosphere causing acid rain.
 Biochemical effects
 Nitrogen oxides and suspended particles both can irritate lungs,
aggravate asthma or chronic bronchitis and increase respiratory
infections.

 Carbon monoxide (CO)
 Colorless, odorless gas, readily combines with hemoglobin in blood to
Toxic.
 (Under normal condition) O2 + Hb = O2Hb (Oxyhaemoglobin)
 (In presence of CO) O2Hb + CO = COHb + O2 (Carbxyhaemoglobin)
 Cigarette smoking is responsible for the greatest exposure to carbon
monoxide.
 CO is attached to blood hemoglobin reduces the oxygen carrying
capacity of blood. This impairs perception and thinking, slows
reflexes and causes headaches, drowsiness, dizziness and
nausea and blurred vision.
 CO, carbon monoxide, 90% natural, 10% from incomplete
combustion, cigarettes, combines with hemoglobin and reduces
bloods ability to carry oxygen. 1,50,000 to 3,50,000 deaths/yr.

 Ozone (O3)
 Ozone or trioxygen, is an inorganic compound with the chemical
formula O3.
 It is a pale blue gas with a distinctively pungent smell.
 It is an allotrope of oxygen that is much less stable than
the diatomic allotrope O2, breaking down in the lower atmosphere to
normal dioxygen.
 Ozone is formed from dioxygen by the action of ultraviolet light and
also atmospheric electrical discharges, and is present in low
concentrations throughout the Earth's atmosphere.
 Biochemical effects- Ground Level Ozone
 Damage to crops
 Irritates the respiratory tract and eyes
 High levels of O3 results in chest tightness, coughing and wheezing
 Increased hospital admissions and premature death

 Hydrocarbons (other volatile organic
compounds): very reactive. React with many kinds of
compound yielding many kinds of products. Volatile HC and other
organic compounds participate in atmospheric reactions generating
ozone.
 Many volatile organic compounds such as benzene and
formaldehyde and toxic particulates such as lead and cadmium
can cause mutations, reproductive problems and cancer,
breathlessness and irritation of the eye, nose and throat.

Effects of Air Pollutants
Interferes with photosynthesis,
carbohydrate production
Cancer, asthma, birth defects,
eye & respiratory system
irritation, and genetic mutation.
contribute to sick building
syndrome indoors
Acid rain: soil, buildings &
materials, forest & aquatic life.
prolonged exposure to high CO
concentrations, unconsciousness,
convulsions and death would
occur; severe effects on the baby
of a pregnant woman.
It is important to remember that air pollutants are transboundary,
i.e. they know no borders and travel easily from their sources
towards other locations spreading pollution throughout the world.

Air Pollution Effects..

Effect of Air Pollutants
 On Human Health
 Irritate respiratory tract
 Irritate eyes, nose and throat
 Lead particles - cause Lead Poisoning
 Cadmium particles – Cardio vascular disease,
Kidney and Liver damage
 Nickel particles – respiratory damage
 Mercury – Central nervous system, kidney and brain
 Radioactive substances - affect future generations

 On Animals
 Feeding particulate coated plants (fluorine, lead, arsenic) –
Arsenic Poisoning
 Lead Poisoning – Bronchitis, Lack of appetite in pet animals

 On Plants
 Spraying Pesticides, Organic manure and agricultural
applications – affect growth of plants
 Destroy chlorophyll formation – disturb photosynthesis
 SO2 – decreases chlorophyll content – causes Chlorosis
 NO2 – permanent leaf fall
 Ozone – Necrosis - dead area on leaf – damages the leaves

 On Materials
 Corrosion
 Abrasion
 Deposition
 Chemical attack on surface

 On Climate
 Increase in CO2
– increase temperature of atmosphere
– ice and polar glaciers melt
– flooding of coastal towns
– change rainfall pattern
– agricultural output changes
 Depletion of Ozone layer
– increase penetration of harmful UV rays on earth
– skin diseases, sunburns, inactivation of RNA, DNA and
protein molecules

Photochemical Smog and Ozone
 Smog is a kind of air pollution, originally named for the mixture of
smoke and fog in the air.
 HC and NO react in presence of sunlight to produce ozone and
PAN (peroxy acetyl nitrate)
 Nitrogen oxides + hydrocarbons + Ultraviolet radiation -----> Peroxy-acetyl
nitrate PAN + O3 ozone.

Generation Mechanism contd..

Nitrogen Oxide Emissions (NOx)

Volatile Organic Compound Emissions
(VOC’s)

Generation Mechanism:
Three ingredients required:
 Ultraviolet Light
 Hydrocarbons
 Nitrogen oxides
• HC
• NO
UV Light
• O3
• PANs
• Other Oxidants
(Aldehydes, Ketones etc)
Photochemical Reaction

The Ingredients of Smog

Photochemical Reactions:
Troposphere Ozone:
 NO2 + hn NO + O
 O + O2 O3
Sources:
 Exhaust gases From Motor vehicles
 Unburnt Hydrocarbons

Photochemical Reaction Contd..
Volatile Organic Compounds (VOC)
Carbon-based molecules such as Aldehydes,
Ketones and Hydrocarbons
RCH3 + 2O2 + 2NO RCHO + 2NO2 + H2O
Sources:
 Paint thinners, solvents and petroleum constituents
 Trees: emits isoprene and terpenes
 Methane from termites, cows and cultivation

Photochemical Reaction Contd..
Peroxyacetyl Nitrates (PAN)
Are secondary pollutants formed from peroxyacid
radicals and NO2
 CH3CHO + OH• CH3C•O + H2O
 CH3C•O + O2 CH3C(O)OO• (acetylperoxy)
 CH3C(O)OO• + •NO2
CH3C(O)OONO2
(PAN)

Effects on human health:
 Ozone
 Cause acute respiratory problems
 Aggravate asthma
 Cause temporary decreases in lung function in healthy adults
 Lead to hospital admissions and emergency room visits
 Impair the body's immune system
 Peroxyacetylnitrate (PANs)
 Respiratory and eye irritants
 Mutagenic- causing skin cancer

Effects on human health contd..
 Volatile organic compounds (VOCs)
 Global warming- Methane
 Carcinogenic- benzene
 Form Ozone

Photochemical Smog

Greenhouse Effect And
Global Warming

GREENHOUSE EFFECT
 The atmosphere over the earth contains certain gases that play significant role in
maintaining the mean effective planetary temperature.
 To allows short- wave solar radiation to enter the greenhouse but the long- wave and
infrared heat- producing re- radiation from inside the greenhouse can not pass through the
walls.
 Due to the presence of certain gases, the atmosphere strongly absorbs the infrared
radiation resulting in atmospheric heating.
 Thus the temperature within the greenhouse becomes higher than outside.
 The gases that absorb strongly in long wave and particularly in infrared region are
commonly called “Greenhouse Gases”.
 The heating of atmosphere due to presence of these greenhouse gases is commonly
called “Greenhouse Effect”
 This greenhouse effect is thought to be responsible for global warming.
 Carbon dioxide contributes to only 56% of greenhouse heating.
 The average surface temperature of Earth is about 15 to 18°C .
 Global Warming is increase in the average temperature of the atmosphere, oceans, and
landmasses of Earth.

.Variations of Solar Radiation
ns of Solar Radiation

Greenhouse effect

Greenhouse Gases (GHGs)
 These include those gases present in the atmosphere that have the
property of trapping and absorbing strongly the long-wave and
infrared terrestrial re-radiation thus causing the atmospheric
heating.
 Some greenhouse gases occur naturally in the atmosphere,
while others result from human activities.
 Important such gases are discussed briefly.
1) Carbon dioxide (CO2)
2) Methane (CH4)
3) Nitrous oxide (N2O)
4) Ozone (O3)
5) Chlorofluorocarbons (CFCs)
6) Water vapour

Greenhouse gases

Greenhouse Gases (GHGs)
 1) Carbon dioxide (CO2):
 The percentage of this gas by volume in dry air is about 0.035%.
 The gas is involved in a complex global cycle.
 It is released from the interior of the earth and is produced by respiration
of living organisms, soil processes, combustion of organic matter and
oceanic evaporation.
 On the other hand, it is dissolved in the water bodies on the earth and is
also consumed in the photosynthesis of plants.
 2) Methane (CH4):
 In dry air, the proportion of this gas by volume is about 0.0017%.
 It is produced primarily by anaerobic processes in the natural wetlands,
rice paddies, digestive processes of animals, biomass burning and other
human activities.
 It is destroyed in the troposphere by a reaction with hydroxyl (OH) ion.

 3) Nitrous oxide (N2O):
 This gas is produced by biological processes in the oceans as well as
soils, by industrial combustion, burning of fossil fuels and by use of
chemical fertilizers.
 It is destroyed by photochemical reactions in the stratosphere involving
the production of nitrogen oxides (NOx).
 The gas has quite long lifetime of about 132 years in the atmosphere.
 4) Ozone (O3):
 The volume wise proportion of this gas in atmosphere is about 0.00006%.
 It is produced by high level breakup of oxygen molecules by solar ultra-violet
radiation and is destroyed by photochemical reactions involving
nitrogen oxides and chlorine in the middle and upper stratosphere.

 5) Chlorofluorocarbons (CFCs):
 These gases are produced solely by human activities i.e. by aerosol propellants,
refrigeration coolents, cleansers and air conditioning plants.
 Chief among these are CFCl2 and CFCl3.
 These gases released into the atmosphere near ground level quickly move up and
reach the stratosphere.
 Within the stratosphere, the gases move towards poles.
 These gases are decomposed to chlorine by photochemical reactions. The average
lifetime of these gases in atmosphere is 55- 116 years.
 6) Water vapour:
 Water vapor in clouds re-radiate heat back to Earth.
 Though water vapour is not a gas in the strict chemical sense, it is an important
atmospheric constituent.
 Its average proportion in the air by volume is about 1.0%.
 The amount of water vapour in the atmosphere is highly variable depending upon the
place ant time.

Impact Of Global Warming
• Temperature extremes
• Rise in sea level, and change in precipitation
• Injuries from storms, coastal flooding
• Interruption of power supply, contamination of drinking water
• Drought
• Food shortages due to shift in agricultural food production
• Air pollution (made worse by warming)
• Asthma, bronchitis, emphysema complications
• Increased need due to population migrations
• Unable to contain spread of infectious diseases

The Ozone Layer:
Formation and Depletion

Ground Level Ozone
 Ozone (O3) is a key constituent of the troposphere.
 Ozone (Greek word ozein, mean “to smell”), pale blue, highly
poisonous gas with a strong odor.
 Ozone is considered a pollutant at ground level.
 Breathing O3 affects both the respiratory and nervous systems,
resulting in respiratory distress, headache, and exhaustion.
 Ozone is damaging to plants, resulting in leaf mottling and reduced
growth.

The Ozone Layer
 The stratosphere contains the ozone shield, a layer of ozone (O3) in
the stratosphere, 50 km above the ground.
 Ozone layer is a thin, fragile shield that contains relatively high
concentrations of ozone.
 It shields the entire Earth from much of the harmful UV radiation that
comes from the sun
 Damage in the ozone layer will naturally mean the entry of harmful
rays in to the atmosphere.
 In the 1970s, the scientists discovered that the ozone layer is being
depleted.

Ozone formation
Ozone (O3)
Chemically forms when UV hits on stratosphere
Oxygen molecules dissociate into atomic oxygen
sunlight
O2 O + O
 Atomic oxygen quickly combines with other oxygen molecules
to form ozone
O + O2 O3

Ozone formation
Ozone (O3)
A component of photochemical smog
Important for our survival
Absorbs some of the potentially harmful UV radiation which can
cause skin cancer and damage to vegetation
Highest concentration in the upper atmosphere
Occurs naturally as a layer in the stratosphere
The layer is thinnest around the equator and the concentration
increases towards the poles
The amount of ozone above a point on the earth’s surface is measured
in Dobson units (DU)
– ~ 260 DU near the Tropics
– higher elsewhere

What is CFCs?
Chlorofluorocarbons (CFCs)
Composed of elements chlorine, fluorine, and carbon
Developed in 1930 by DuPont
CFCs were welcomed by industries:
– Low toxicity
– Chemical stability
– Cheap
Usage:
– As refrigerants
– As blowing agents
– For making flexible foam
– As cleaning agents
– As propellants

What is CFCs?
CFCs are used in aerosol sprays
(Sources: http://www.yahoo.com) CFCs were used as refrigerants in the
past (Sources: http://www.yahoo.com )

Present situation
Stratospheric ozone over Antarctica:
– Has been depleted over the last 15 years
– The ozone hole:
enlarging
large enough to cover most of the North America
would take at least 50 years to restore

Destruction of ozone layer
Chlorine atoms from CFCs attack the ozone, taking away ozone and
forming chlorine monoxide (ClO).
O3 + Cl  O2 + ClO
Chlorine monoxide then combines with another oxygen atom to form a
new oxygen molecule and a chlorine atom.
ClO + O  Cl + O2
The chlorine atom is free to destroy up to 3,00,000 ozone molecules

The Ozone Layer

The Ozone Hole – Explained!

The largest Antarctic ozone hole
ever recorded (September 2006).
 The Antarctic ozone hole
is an area of the Antarctic
stratosphere in which the
recent ozone levels have
dropped to as low as 33%
of their pre-1975 values.

Health effects of Ozone depletion
 Each 1% drop in ozone is thought to increase human skin
cancer rates by 4-6%.
 The United Nations Environment Program predicts a 26 percent
rise in cataracts and non-melanoma skin cancers for every
10% drop in ozone.

 This translates to 1.75 million cases of cataracts and 3,00,000
more cases of skin cancer every year.

Impact on Humans
 The effect of ozone depletion is the increased UV-B
radiation reaching Earth’s surface.
 Skin cancer: Exposure to ultraviolet rays poses an
increased risk of developing several types of skin cancers,
including malignant melanoma, basal and squamous
cell carcinoma.
 Eye damage: Direct exposure to UV radiations can result
in photokeratitis (snow blindness), and cataracts.
 Immune system damage: Effects of UV rays include
impairment of the immune system.
 Increased exposure to UV rays weakens the response of
the immune system.
 Accelerated aging of skin: Constant exposure to UV
radiation can cause photo allergy, which results in the
outbreak of rash in fair-skinned people.
 Other effects: Respiratory illness and heart problems
 Ozone chemicals can cause difficulty in breathing, chest
pain, throat irritation, and hamper lung functioning.

Effects on Amphibians
Ozone depletion is listed as one of the causes for the declining
numbers of amphibian species. Ozone depletion affects many
species of amphibians at every stage of their life cycle. Some of
the effects are mentioned below.
 Hampers growth and development in larvae
 Changes behaviour and habits
 Causes deformities in some species
 Decreases immunity. Some species have become more
vulnerable to diseases and death
 Retinal damage and blindness in some species

Effects on Marine Ecosystems
 In particular, plankton (phytoplankton and bacterioplankton) are
threatened by increased UV radiation.
 Marine phytoplankton play a fundamental role in both the food
chain as well as the oceanic carbon cycle.
 Plankton play an important role in converting atmospheric carbon
dioxide into oxygen.
 Ultraviolet rays can influence the survival rates of these
microscopic organisms, by affecting their orientation and
mobility.
 This eventually disturbs and affects the entire ecosystem.

Impact on Plants
 In some species of plants, UV radiation can alter the
time of flowering, as well as the number of flowers.
 Plant growth can be directly affected by UV-B
radiation.
 Despite mechanisms to reduce or repair these
effects, physiological and developmental processes
of plants are affected.

Effects on the Environment
 Global warming
 Climate change
 Crop and forest damage
 Infections and skin diseases on animals
 Less ocean plankton
 Less fish harvest

Food supply
 Reduce photosynthesis - crops
affected.
 Kills plankton  fish ¯

Impacts on other animals
 Reduces plankton population
 Reduces penguin population
 Reduces the percentage of hatching of frog eggs

What is Acid Rain;
what are its Causes and Effects?

Acid Rain
 Nitric oxide sulfur dioxide released primarily from electric power plants
motor vehicles
 SO2 + water vapor + ozone --- H2SO4
 NO + sunlight + O2 --- NO2 + various atmospheric gases --- HNO3

Wet and dry acid deposition
 Caused by SO2 and NO2.
 Alone cause dry acid deposition, with all forms of water vapor,
these form sulfuric and nitric acid - acid rain downwind of sites of
emission.
 Normal rain water pH 5.0-5.6 approx. Acid rain 5.0
Affects industrialized areas worldwide.
 Developing countries have more pollution, fewer controls than
developed countries.

Acid Precipitation

Environmental Impact of Acid deposition
Sterilization of lakes and forests.
Reducing the populations of small invertebrates and decomposers.
Reducing agricultural yields.
Causing extensive structural damage by corroding marble, metal,
and stonework.
Degrading water supplies by leaching heavy metals from the soil into
drinking-water supplies.
Increases in lung cancer and colon cancer.
kill fish, plants; stress and defoliate trees due to moss growth, insect
attack, and loss of nutrients.

Thank
You

Air Pollution

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