SOURCES AND TYPES OF

AIR POLLUTANT

By
Dr.Pallavi Das
Assistant Professor
Deptt. of Environmental Science
IGNTU

Course Title: Environmental

Pollution and Control Technique-I
M.SC 2nd Semester
 AIR POLLUTION

Definition –
 Air pollution may be defined as the presence one or more
contaminants or combinations thereof in air in such quantities and of
such durations as may be or tend to be injurious to human, animal or
plant life, or property, or which unreasonably interferes with the
comfortable enjoyment of life or property or conduct of business.

AIR POLLUTANT
 It is a substance or effect dwelling temporarily or permanently in the air ,
which adversely alters the environment by interfering with the health, the
comfort, or the food chain, or by interfering with the property values of
people.

 A pollutant can be solid (large or sub-molecular), liquid or gas .

 SOURCES OF AIR POLLUTION
 Air Pollution may originate from a natural or anthropogenic source or
from both sources.

 E.g. of natural source – an erupting volcano, accidental fire etc

 Nonpoint Sources vs. Point Sources

The term "nonpoint source" is defined to mean any source of water
pollution that does not meet the legal definition of "point source" in
section 502(14) of the Clean Water Act

The term "point source" means any discernible, confined and

discrete conveyance, including but not limited to any pipe, ditch,
channel, tunnel, conduit, well, discrete fissure, container, rolling stock,
concentrated animal feeding operation, or vessel or other floating craft,
from which pollutants are or may be discharged. This term does not
include agricultural storm water discharges and return flows from
irrigated agriculture.
Non-point source pollution can include:
•Excess fertilizers, herbicides and insecticides from agricultural lands
and residential areas
•Oil, grease and toxic chemicals from urban runoff and energy
production
•Sediment from improperly managed construction sites, crop and
forest lands, and eroding streambanks
•Salt from irrigation practices and acid drainage from abandoned
mines
•Bacteria and nutrients from livestock, pet wastes and faulty septic
systems
•Atmospheric deposition and hydromodification
 TYPES OF AIR POLLUTANT
The primary pollutants are “directly”
emitted from the processes such as fossil
fuel consumption, Volcanic eruption and
factories. The major primary
pollutants are Oxides of Sulphur, Oxides of
Nitrogen, Oxides of Carbon, Particulate
Matter, Methane, Ammonia,
Chlorofluorocarbons, Toxic metals etc.

The secondary pollutants are not emitted

directly.
The secondary pollutants form when the
primary pollutants react with themselves or
other components of the atmosphere. Most
important secondary level Air
Pollutants are Ground Level Ozone, Smog
and POPs (Persistent Organic Pollutants).
INDUSTRIAL SOURCES OF POLLUTION

 Liquid soap factory

 Sulphuric Acid factory

 Plastic industry

 Acid manufacturing units

 Phosphate fertilized industry

 Inorganic chemical plants

 Metal industry

Aluminum plants
 MAJOR PRIMARY POLLUTANTS

Nitrogen Oxides (NOx)

Ammonia (NH3)

Carbon monoxide (CO)

Sulphur Oxides (SOx)

Heavy metals (As,Cd,Pb,Hg)

Volatile Organic Compounds

Nitrogen Oxides (NOx)

Nitrogen oxides, particularly nitrogen dioxide, are expelled

from high temperature combustion, and are also produced
during thunderstorms by electric discharge.

 Nitrogen oxides (NOX) are emitted during fuel combustion,

such as by industrial facilities and the road transport sector. As
with SO2, NOX contributes to acid deposition.

 NO2 that is associated with adverse affects on health, as high

concentrations cause inflammation of the airways (wind
pipe,layrnx).
Carbonmonoxide (CO)

colourless and odourless,toxic gas

comes from the incomplete combustion of fuel in vehicles.

 can be absorbed by haemoglobin in the blood, thus blood

can no longer absorb O2

 extra amounts of CO result in tiredness, headaches, heart

damage and small amounts can be lethal
Sulphur-dioxide (SO2)

Fuels (coal and petroleum) contain sulphur as an impurity;

when fuels are burnt, sulphur is oxidised or burnt to SO2

 Emitted from volcanoes eruptions

 Irritates the eyes and causes breathing difficulties causes

asthmetic problems.

 In the presence of a catalyst such as NO2, forms H2SO4, and

results of acid rain
 Ammonia (NH3)
 A gas with a characteristic pungent odor.

 Odors — such as from garbage, sewage, and industrial

processes

 Radioactive pollutants - produced by nuclear explosions,

nuclear events, war explosives, and natural processes such as
the radioactive decay of radon.

 come from the agricultural sector, from activities such as

manure storage, slurry spreading and the use of synthetic
ammonia fertilizers
 Heavy Metals

The heavy metals arsenic (As), cadmium (Cd), lead (Pb), mercury (Hg)
and nickel (Ni) are emitted mainly as a result of various combustion
processes and industrial activities.

 These chemicals are known as toxins and are linked to thyroid disorders,
cancer, women’s hormonal conditions, chronic fatigue syndrome,
fibromyalgia and other several illnesses & symptoms includes.

• Fatigue
• Lung Cancer
• Cardiopulmonary diseases
 Volatile organic compound (VOC)
VOC is emitted from a large number of sources including paint
application, road transport, dry-cleaning and other solvent uses.
• Methane VOC
• Non methane VOC
• Benzene Methyl Chloride
• CFCs

 Methylene chloride is highly dangerous to human health. It can be found in adhesive

removers and aerosol spray paints and the chemical has been proven to cause cancer in
animals. In the human body, methylene chloride is converted to carbon monoxide and a
person will suffer the same symptoms as exposure to carbon monoxide.

• Benzene, is a chemical found in environmental tobacco smoke, stored fuels, and exhaust
from cars. Benzene has also been known to contaminate food and water and if digested
can lead to vomiting, dizziness, sleepiness, rapid heartbeat, and at high levels, even death
may occur.

• Chlorofluorocarbons (CFCs) widely used cleaning products and refrigerants.

Tetrachloroethene is used widely in dry cleaning harmful to ozone layer which prevents
human by having skin cancer and various skin diseases,
 SECONDARY POLLUTANTS

Major Secondary Air Pollutant

Particulate matter (PM) Particulates created from gaseous primary

pollutants and compounds in photochemical smog. PM is one of the most
important pollutants as it penetrates into sensitive regions of the
respiratory system

• Particulate matter includes both primary and secondary PM

primary PM is the fraction of PM that is emitted directly into the

atmosphere, secondary PM forms in the atmosphere following the
oxidation and transformation of toxic gases (mainly SO2, NOX, NH3 and
some volatile organic compounds (VOCs).
 Ground level Ozone (O3)

Ground level ozone (O3) formed from NOx and VOCs.

Ozone (O3) is a secondary pollutant and a key constituent formed in the

troposphere.

 Photochemical and chemical reactions involving it drive many of the

chemical processes that occur in the atmosphere by day and by night.

 At abnormally high concentrations brought about by human activities

(largely the combustion of fossil fuel), it is a pollutant, and a constituent of
smog.

Ozone is a powerful and aggressive oxidising agent, elevated levels of

which cause respiratory and cardiovascular health problems and lead to
premature mortality.

High levels of O3 can also damage plants, leading to reduced agricultural

crop yields and decreased forest growth.
 What is Particulate Matter?
Particulate matter (PM) : A wide variety of airborne material. PM pollution
consists of materials (including dust, smoke, and soot), that are directly
emitted into the air or result from the transformation of gaseous pollutants.

Particles come from natural sources (e.g., volcanic eruptions) and human
activities such as burning fossil fuels, incinerating wastes, and smelting
metals.

Coal grinding, fugitive road dust and dust from rock quarries are examples
of physical processes that release particulate matter to the atmosphere. These
particles are usually large (>100 mm diameter), do not have a long residence
time in the atmosphere, and are not taken into the body during respiration.

PM formed through chemical reactions are typically much smaller (<10 mm
diameter) . Chemical processes that release particulate matter to the atmosphere
include all forms of combustion (automobiles, fossil fuel power plants, forest fires
and residential fireplaces) and. atmospheric emissions from volcanoes).
e.g NH4Cl,
SO42- / NO3- salts Sources Mineral dust from
weathering of rocks
and soils

Natural: forest fires,

volcanoes etc.
Man-made: fossil-fuel
combustion, industry
 PM10 particles with a diameter of 10 micrometres or less
PM2.5 particles with a diameter of 2.5 micrometres or less
TSP total suspended particulate

PM10 and Fuel combustion such as burning coal, oil, wood and light fuel
PM2.5 oil in domestic fires, transportation and industrial processes.
Sources include dusty roads, soil tiling, quarries and fuel
TSP
combustion.

These are classified as:

Figure compares the size of PM10 and PM2.5 particles to a strand of hair and a
type of beach sand. They are tiny – too small for the human eye to see.
 Particles in the Atmosphere

Term Meaning
Condensation Formed by condensation of vapors or reactions of
aerosol gases
Aerosol Colloidal-sized atmospheric particles
Dispersion aerosol Formed by grinding of solids, atomization of liquids,
or dispersion of dusts
Fog Denotes high level of water droplets
Haze Decreased visibility due to particles
Mists Liquid particles
Smoke Particles from incomplete fuel combustion
 Characteristics of Particles
The most important characteristic of particulate matter (PM) is
the particle size.

This property has the greatest impact on the behavior of

particulate matter in control equipment, the atmosphere, and the
respiratory tract.

Particles of importance in air pollution control span a broad size

range from extremely small (0.01 micrometer) to more than 1,000
micrometers. A human hair has a diameter of approximately 50
micrometers.

The chemical composition of the particulate matter is also important.

Absorption and heterogeneous nucleation of vapor phase pollutants

onto existing particles can create toxic particulate matter.
 Sources and sinks of atmospheric aerosols

After the emission of aerosol particles, they undergo various physical and
chemical processes. During these processes, size, composition and structure
of particles can be changed. Finally, they can be removed from the
atmosphere to the surfaces by dry or wet deposition processes
 Mechanism of aerosol formation

Nucleation: Defined as creation of molecular embryos or clusters

prior to formation of a new phase during the transformation of
vapour → liquid → solid. Nucleation can occur within the original
phase (homogeneous nucleation), or on another phase, e.g. on a small
particles (heterogeneous nucleation).

Condensation: gas to liquid phase change.

Cloud condensation nuclei (CCN): hygroscopic aerosol particles that

can serve as nuclei of atmospheric cloud droplets, that is, particles on
which water vapour condenses.

Particle coagulation: a process, in which small particles collide with

each other and coalesce completely to form a larger particle
  SO2 is emitted from fossil combustion and also forms from oxidation
reactions of the biogenically emitted organic sulfur compounds. OH forms
from the following atmospheric reactions:
hγ
O3 → O(1D) + O2 (4)
O(1D) + H2O→ 2OH

 Nucleation starts from the formation of sulfuric acid (H2SO4), because of

its low vapour pressure. Formation of H2SO4 involves the following reactions:

SO2 + OH → HSO3 (Rate limiting step) (1)

HSO3 + O2 → HO2 + SO3 (2)
SO3 + H2O → H2SO4 (3)

 Once formed, H2SO4 immediately becomes hydrated. The hydrated

H2SO4 molecules are nuclei, and nucleation takes place by condensation of
H2SO4 molecules and coagulation.
That is, monomer becomes dimer, and dimer becomes trimer, and so on.
H2SO4 + H2SO4 → 2 H2SO4 (6)
2 H2SO4 + H2SO4 → 3 H2SO4 (7)
3 H2SO4 + H2SO4 → 4 H2SO4 (8)
4 H2SO4 + H2SO4 → 5 H2SO4

HOMOGENOUS NUCLEATION
If NH3 dissolves in some H2O

NH3 + H2O NH4+ + OH-

2NH4+ + SO42- (NH4)2SO4(aq)

Thus, particles form through complex gas phase, heterogeneous, and

liquid phase reactions
 SINK PROCESSES
Wet deposition processes (the main sink of atmospheric aerosol particles)

 Rain-out and washout: a part of cloud droplets form precipitation which

reaches Earth’s surface removing aerosols from cloud and from the column of
air below the cloud.
 Cloud deposition: deposition form of aerosols in high elevation ecosystems
due to interception of cloud droplets by vegetation.
Dry deposition processes (less important on a global scale)

 Turbulent diffusion: for larger particles (with a diameter larger than 1 µm)
 Gravitational settling (sedimentation): larger particles are influenced more
by gravity and fall back to the surface. This process becomes increasingly
important for particle sizes above 1 µm.
 Impaction: if a particle cannot follow the flow streamline around an
obstacle, small particle can hit this obstacle
 Interception: if an object is not directly in the path of particle moving in
the gas stream but particle approaches the edge of the obstacles, it may
collected by the obstacle
 History of Smog
• Name comes from a mix of “Smoke” and
“Fog”
• First observed in London during the
industrial revolution
• There are 2 types of smog:
 Industrial Smog (London) and
 Photochemical Smog (Los Angeles)
 Industrial Smog (Reducing)
• Source: Pollution from the burning of coal and oil that
contains sulfur
• Consists mainly of: Sulfur Dioxide, Sulfur Trioxide,
soot and ash (particulate matter) and sulfuric acid
• It can cause breathing difficulties in humans, plus acid
rain damage to plants, aquatic systems, and metal or
stone objects
• London and Chicago have problems with industrial
smog.
• Methods of reducing this smog: Alkaline Scrubbers
reduce SO2 and SO3 levels; electrostatic precipitators
reduce particulates.
Photochemical Smog (Oxidizing)
• Source: Mainly automobile pollution
• Contains: Nitrogen Oxides, Ozone, Alkanals,
Peroxyacyl Nitrates (PANs), plus hundreds of other
substances
• Effects: PANs cause eyes to water and can damage
plants, O3 irritates eyes and deteriorates rubber and
plants, NOx causes acid rain.
• First observed in Los Angeles in the 1940s, Manila and
Mexico City also experience this kind of smog
• Catalytic Converters change NO to N2, Lean burning
engines reduce Nox, but create more CO and
Hydrocarbons.
 Reactions of Smog
• Sulfur Dioxide can be oxidized to Sulfur trioxide, a
secondary pollutant:

• Metallic Particulates act as a catalyst for this reaction.

• In addition, free radicals from NO2 also speed up the
reaction:
When fossil fuels are burnt, a variety of pollutants are emitted into
the earth's troposphere. Two of the pollutants that are emitted are
hydrocarbons (unburnt fuels) and nitric oxide (NO). When these
pollutants build up to suffidently high levels, a chain reaction occurs
from their interaction with sunlight in which NO is converted to
nitrogen dioxide (NO2). This NO2 absorbs energy from sunlight and
breaks up into nitric oxide and free oxygen atom.

NO + O2 ---> NO2 + u.v. ---> O + NO

 Oxygen atoms are very reactive and can combine with the O2 of the air
to produce ozone.

The ozone formed in the above reaction (H) reacts rapidly with the NO(g)
formed in reaction (i) to regenerate NO2. NO2 is a brown gas and at
sufficiently high levels can contribute to haze.

Ozone is a toxic gas and both NO2 and O2 are strong oxidising agents and can
react with the unburnt hydrocabrons in the polluted air to produce chemicals
such as formaldehyde (HCHO), acrolein CH2=CHO) and peroxy acetyl nitrate
(PAN).
Photochemical smog occurs in dry, stagnant air masses, usually
stabilized by a temperature inversion, that are subjected to
intense sunlight.

A smoggy atmosphere contains ozone, O3, organic oxidants, N

oxides, aldehydes, and other noxious species, as well as a haze of
fine particles.

The chemical ingredients of smog are nitrogen oxides and

organic compounds, both released from the automobile, as well
as from other sources.

The driving energy force behind smog formation is

electromagnetic radiation with a wavelength at around 400 nm or
less, in the ultraviolet region, just shorter than the limit for
visible light.

Formation of active species starting photochemical reactions.

 How Does Photochemical Smog Form?

The formation of photochemical smog involves three primary ingredients:

nitrogen oxides, hydrocarbons and sunlight. The nitrogen oxides and
hydrocarbons are by-products of fossil fuel-burning energy plants, and they
can even come from natural processes, but the main source is the internal
combustion engines in gasoline-powered automobiles.

Nitrous oxide and nitrogen dioxide dissociate in sunlight and combine with
trace hydrocarbons to ultimately produce a large number of pollutants. The
complex process proceeds in stages:
Sunlight causes the photo-dissociation of nitrogen and oxygen to yield ozone
and oxygen atoms.

Oxygen atoms react with water to form hydroxyl radicals (OH).

Hydroxyl radicals oxidize hydrocarbons to form hydrocarbon radicals.
Hydrocarbons oxidize to form a class of chemicals known as aldehydes.
Aldehydes oxidize to form aldehyde peroxides and aldehyde peroxyacids,
which are the pollutants that create most of the health problems.
Peroxyacetyl nitrate, CH3COOONO2

Hydrocarbons + O2 + NO2 + light → CH3COOONO2

Photochemical Smog is
an air pollution ,formed
when photons of
sunlight hit molecules of
different kinds of
pollutants in the
atmosphere
42
EFFECT AND CONTROL OF AIR POLLUTION

By
Dr.Pallavi Das
Assistant Professor
Deptt. of Environmental Science
IGNTU
Course Title: Environmental Pollution
and Control Technique-I
M.SC 2nd Semester
EFFECT OF AIR POLLUTION ON HUMAN HEALTH
 INTRODUCTION

Air pollution : one of the greatest “ENVIRONMENTAL EVIL”.

 The air we breathe has not only LIFE SUPPORTING properties

but also LIFE DAMAGING properties.

 An average man breathes 22,000 times a day and takes in 16 kg of

air each day.

All the impurities in the inhaled air do not necessarily cause harm.
Some may be harmful when present in air in small concentration
and others only if they are present in high concentration.
 Factors affecting human health

 Nature of the pollutants

 Concentration of the pollutants

Duration of exposure

State of health of the receptor

Age group of the receptor

Target organ systems of air pollution

Cancer
Asthma, Kidney,
Chronic Liver
Bronchitis Damage

Birth Defects, Skin

Miscarriages Rashes

Cough, Development
Throat of problem in
Irritation Children
Nervous
System
Damage
• Exposure to air pollution can cause both acute
(short-term) and chronic (long-term) health effects.
• Acute effects are usually immediate and often reversible
when exposure to the pollutant ends. Some acute health
effects include eye irritation, headaches, and nausea.

• Chronic effects are usually not immediate and tend not to

be reversible when exposure to the pollutant ends.
– Some chronic health effects include decreased lung
capacity and lung cancer resulting from long-term
exposure to toxic air pollutants.
 Effects on Human respiratory system

 Both gaseous and particulate air

pollutants can have negative
effects on the lungs.
• Solid particles can settle on the
walls of the trachea, bronchi, and
bronchioles.
• Continuous breathing of polluted
air can slow the normal
cleansing action of the lungs and
result in more particles reaching
the lower portions of the lung.
• Damage to the lungs from air
pollution can inhibit this process
and contribute to the occurrence
of respiratory diseases such as
bronchitis, emphysema, and
cancer.
Table 1: Sources, Health and Welfare Effects for Criteria Pollutants.
Pollutant Description Sources Health Effects Welfare Effects
Carbon Colorless, odorless Motor vehicle exhaust, Headaches, reduced mental Contribute to the formation of
Monoxide gas indoor sources include alertness, heart attack, smog.
(CO) kerosene or wood burning cardiovascular diseases,
stoves. impaired fetal development,
death.

Sulfur Dioxide Colorless gas that Coal-fired power plants, Eye irritation, wheezing, chest Contribute to the formation of
(SO2) dissolves in water petroleum refineries, tightness, shortness of breath, acid rain, visibility impairment,
vapor to form acid, manufacture of sulfuric acid lung damage. plant and water damage,
and interact with other and smelting of ores aesthetic damage.
gases and particles in containing sulfur.
the air.

Nitrogen Reddish brown, highly Motor vehicles, electric Susceptibility to respiratory Contribute to the formation of
Dioxide (NO2) reactive gas. utilities, and other infections, irritation of the lung smog, acid rain, water quality
industrial, commercial, and and respiratory symptoms deterioration, global warming,
residential sources that (e.g., cough, chest pain, and visibility impairment.
burn fuels. difficulty breathing).

Ozone (O3) Gaseous pollutant Vehicle exhaust and certain Eye and throat irritation, Plant and ecosystem damage.
when it is formed in other fumes. Formed from coughing, respiratory tract
the troposphere. other air pollutants in the problems, asthma, lung
presence of sunlight. damage.

Lead (Pb) Metallic element Metal refineries, lead Anemia, high blood pressure, Affects animals and plants,
smelters, battery brain and kidney damage, affects aquatic ecosystems.
manufacturers, iron and neurological disorders,
steel producers. cancer, lowered IQ.

Particulate Very small particles of Diesel engines, power Eye irritation, asthma, Visibility impairment,
Matter (PM) soot, dust, or other plants, industries, bronchitis, lung damage, atmospheric deposition,
matter, including tiny windblown dust, wood cancer, heavy metal aesthetic damage.
droplets of liquids. stoves. poisoning, cardiovascular
effects.
 Effects of Air Pollution
 Reduced lung functioning
 Irritation of eyes, nose, mouth and throat
 Asthma attacks
 Respiratory symptoms such as coughing and wheezing
Increased respiratory disease such as bronchitis
Reduced energy levels
 Headaches and dizziness
 Disruption of endocrine, reproductive and immune systems
 Neuro behavioural disorders
 Cardiovascular problems
 Cancer
Premature death
 Particulate Matter effect
 Health effects
 Wheezing and coughing
 Heart attacks and death
 TSP (Total Suspended Particles)
 In presence of SO2, direct correlation between TSP and
hospital visits for bronchitis, asthma, emphysema,
pneumonia, and cardiac disease
 ~60,000 deaths from PM

1% increase in mortality for every 10 mg/m3 increase in

PM
• Respiratory mortality up 3.4% for the same
• Cardiovascular mortality up 1.4% for the same
 PM10 (<10 µm, coarse (2.5-10 µm) and fine particles) –
Anything larger deposited in the HAR (nasal- pharangycal)

 PM2.5 (<2.5 µm, fine particles)

 Most serious health effects in alveolar/gas exchange region

shift in regulation focus

May adsorb chemicals & intensify their effects

Toxic or carcinogenic – pesticides, lead, arsenic, radioactive

material
8% increase in lung cancer for each 10 µg/m3 increase of
PM2.5
 Carbon Monoxide effect

 Colorless, odorless, tasteless gas --“Silent Killer”

 Cause: incomplete combustion
Source: transportation sector, energy production, residential heating
units, some industrial processes
Ambient concerns addressed by NAAQS
Reacts with hemoglobin in blood – Forms carboxyhemoglobin (HbCO)
rather than oxyhemoglobin (HbO2) – Prevents oxygen transfer

Toxic effects on humans

Low-level: cardiovascular and neurobehavioral

High-level: headaches/nausea/fatigue to possible death

Oxygen deficient people esp. vulnerable (anemia, chronic heart or lung

disease, high altitude residents, smokers)

 Cigarette smoke: 400-450 ppm; smoker’s blood 5- 10% HbCO vs 2% for

non-smoker
 Ozone effect

Cause: product of photochemical reactions

Source: cars, power plants, combustion, chemical
industries

Acute Health effects

 Severe E/N/T (ear/nose/throat) irritation
Eye irritation at 100 ppb
Interferes with lung functions
• Coughing at 2 ppm

 Chronic Health Effects - Irreversible, accelerated lung

damage
 NOx effect

Cause: Fuel combustion at high temps

Source: mobile and stationary combustion sources
 Prolonged exposure
 pulmonary fibrosis, emphysema, and higher LRI (lower respiratory
tract illness) in children
 Toxic effects at 10-30 ppm –
 Nose and eye irritation
 Lung tissue damage
 Pulmonary edema (swelling)
 Bronchitis
Pneumonia
Aggravate existing heart disease
 SOx effect
 Cause: Burning fuel that contains sulfur

Source: Electric power generation, diesel trucks

Gas and particulate phase
 Soluble and absorbed by respiratory system
 Short-term intermittent exposures
Bronchoconstriction (temporary breathing difficulty)
E/N/T irritation
 Mucus secretion
 Long-term exposures
 Respiratory illness
Aggravates existing heart disease
 Intensified in presence of PM
London issues were combination of the two
 Lead (Pb) effect

Source: burning fuels that contain lead (phased out), metal

processing, waste incinerators

 Absorbed into blood; similar to calcium

Accumulates in blood, bones, muscles, fat

 Damages organs – kidneys, liver, brain, reproductive system,
bones (osteoporosis)
Brain and nervous system – seizures, mental retardation,
behavioral disorders, memory problems, mood changes,
• Young children - lower IQ, learning disabilities
Heart and blood – high blood pressure and increased heart
disease
Chronic poisoning possible
 Bio-aerosols effect
Aerosols with organic origin
 Non-viable: pollen, dander, insect excreta, sea salt
Viable: microorganisms
Cause: aerosolization of organic material
Sources:
Human: sneezing, coughing
 Non-human: wind, waves, WWTP
Health Effects: allergies (pollen) to death (pathogenic organisms) –
Pathogenic – Minimum Infectious Dose
Allergies
 Pollen, dander, fungi (spores)
Airborne transmission of disease – Bird flu, SARS, Legionnella (pneumonia)
Indoor Air Quality
•Ventilation Systems – moist ductwork, protection, recycled air
• Office Buildings – Sick Building Syndrome – Hospital (nosocomial)
• Biological Warfare – Anthrax, Ebola virus
EFFECT OF AIR POLLUTION
ON VEGETATION

PRESENTED BY
DR PALLAVI DAS
 AIR POLLUTANTS
 Air pollutants affect plants worldwide.

 These effects may be severe or subtle.

 Various air pollutants have been identified as phytotoxic agents.

 Phytotoxicity of sulfur dioxide (SO2) has been recognized for

about a century .

 Effects of ozone (O3) for more than 30 years).

 Acidic precipitation for almost 20 years .

 Effects of elevated levels of nitrogen compounds (nitrogen oxides

[NOX] and ammonia [NH3]) in the last decade .
HOW TO DETERMINE EFFECTS OF AIR
POLLUTANTS ON PLANTS

• Under field conditions detection of physiological

changes in plants and identification of their causes is
difficult.
• Therefore visible symptoms of injury are most
commonly used for detecting air pollution damage.
• However, changes in physiology of plants may occur
before visible, morphological damage takes place.
 Pollutant deposition to plants
 Pollutants can be deposited to plants as
 gases.
wet precipitation.
 particulate matter.
 Gaseous pollutants may be taken up by plants via
stomata or
 cuticle.
 The effects of pollutants can be observed at various levels of
biological. Organs like:
subcellular,
cellular,
plant organ,
whole plant,
plant population
community.
 EFFECTS ON VEGETATİON

Injury vs damage

Injury: An observable alteration in the plant

when exposed to air pollution
Damage: An economic or aesthetic loss due to
interference with the use of a plant
Injury - Generally, pollution injury first appears as leaf injury.
Spots between the veins, leaf margin discoloration, and tip burns are
common.
Two ways of pollutant entrance to plant

• Direct way: Through stomates which open

and close to allow air through the interior
parts
• Indirect way: Through the root system.
Pollutants deposit in soil and water and
these pollutants were taken by the roots of
the plant.
 Leafs are important because of its
functions
• Photosynthesis accomplished by chloroplasts
6CO2+6H2O C2H12O6+6O2
• Transpiration: Movement of water from the
root system up to the leaves. Nutrient
movement and cooling
• Respiration:Oxidation of carbonhydrates,
energy producing process.
• C2H12O6+6O2 6CO2+6H2O
COMMON SYMPTOMS OF DAMAGE ON PLANTS DUE TO
AIR POLLUTION

 CHLOROSIS (Yellowing of leaf)

 Due to lack of chlorophyll
 Damage of system where chlorophyll is produced

 NECROSIS : When the chlorotic area is exposed to pollutants for a

larger duration then the chlorosis become necrosis. That area is called
necrotic.
Most of time this area become red and brittle. The cell or tissue is not
remain alive and became dead cells.
They are not metabolically active. They are unable to respire.
Necrosis is the acute stage of damage. This is the point where no
return to the original stage takes place.
 OZONE INJURY

 Symptoms vary depending on the concentration of

ozone in the air and the length of exposure, Ozone
.
injury occurs on the most recently emerged leaves.

 Typical ozone injury may not be evident on leaves

exposed to a mixture of pollutants. Symptoms differ in
different areas of the province

 Ozone, the major component of oxidants is formed by

the action of sunlight on products of fuel combustion
and can be moved to nearby growing areas by wind.
 Ozone damage Note stippling
Foliage with flecking "pepper symptoms on leaves
spotting" injury typical of ozone
injury
Ozone injury to soybean foliage
PAN İNJURY

Typical of Peroxyacetyl Nitrate (PAN) creates a glazy bronzing on the

underside of newly expanded potato leaves.
SO2 Damage: SO2 causes an interveinal necrosis.
 Acute sulfur dioxide injury to raspberry. The injury
occurs between the veins and that the tissue nearest the
vein remains healthy.
Fluorine Damage: Marginal necrosis
Fluoride injury to plum foliage. The fluoride enters the leaf through the stomata and is
moved to the margins where it accumulates and causes tissue injury. Note, the
characteristic dark band separating the healthy (green) and injured (brown) tissues of
affected leaves.
Cement-dust coating on apple leaves and fruit. The dust had no
injurious effect on the foliage, but inhibited the action of a pre-
harvest crop spray.
Damage by acid rain
Severe ammonia injury to apple foliage and subsequent
recovery through the production of new leaves.
 Examples of physiological changes in trees
caused by air pollution

Chlorophyll fluorescence: also proved to be a good indicator of ozone effects. Under

the conditions of a well-defined ozone stress ponderosa pine seedlings showed a wide
range of responses:
1- Gradual increase of visible injury (chlorotic mottle) was accompanied by reduction
of net photosynthesis, stomatal conductance, starch accumulations and pigment
concentrations.
2- More pronounced reduction of net photosynthesis than stomatal conductance
suggested that ozone injury to mesophyll, carboxylation, or excitation components of
the CO2 diffusion pathway were greater than injury to the stomata. As a result of all
these changes plants reduced their growth and biomass production (TEMPLE &
BYTNEROWICZ 1993).
 Effects on materials
Effects on metals
• Rusting
• Corrosion due to moisture, temperature and
pollutants
• Alteration of electrical properties
 Effects on stone
• Discoloration
• Blackening
• gypsum formation
• Cracking
Gypsum formation
CaCO3+H2SO4+2H2O CaSO4.2H2O+H2CO3

CaCO3+H2CO3 Ca(HCO3)2
These damaged areas seem to receive rain or rain runoff and seem to be formed by sulfur dioxide
uptake, in the presence of moisture, on the stone surface.
Subsequent conversion of the sulfur dioxide to sulfuric acid results in the formation of a layer of
gypsum on the marble surface.
 EFFECT OF AIR POLLUTION

 GLOBAL WARMING

 Global warming is largely caused by increasing CO2 and other heat

trapping gases (e.g. methane) in the atmosphere.

 Large amount of heat trapped on Earth; Earth becomes hotter.

 It results in rise in sea levels, flooding of low-lying lands, melting of polar

ice caps and changes in global climate.

Measures to reduce global warming-use of fossil fuels (to reduce CO2

emission)

 Use tidal, wind and hydroelectric energy to generate electricity -use of solar
energy.
 ACID RAIN
WHAT IS ACID RAIN?

 Generally, rain water has a pH valueof 5.6 because of the carbondioxide

from air dissolved in it.

Any rainfall has a pH value lessthan 5.6 is defined as acid rain.

When emissions of sulphur dioxide and nitric oxide from stationary

sources are transported long distances by winds, they form secondary
pollutants such as nitrogen dioxide, nitric acid vapor, and droplets
containing solutions of sulphuric acid, sulphate, and nitrate salts.

 These chemicals descend to the earth's surface in wet form as rain or

snow and in dry form as a gases fog, dew, or solid particles, it is known as
acid rain or acid deposition
When gas pollutants e.g. sulphurdioxide, nitrogen
dioxide dissolve in rain water, various acids are
formed.

CO2 + H2O → H2CO3 (carbonic acid)

SO2 + H2O → H2SO4 (Sulphuric acid )
NO2 + H2O → HNO3 (nitric acid)
 IMPACT OF ACID RAIN

Acid Rain can impact

 Surface water (lakes, river etc) and aquatic

animals

Soils

 Forest and Vegetation

 Human Health

Building and the urban environment

Effect On Buildings

Causes extensive damage to buildings,

structural materials of marble ,limestone, slate
etc.
CaC03+H2S04+ CaS04+H20+C02

In Greece and Italy invaluable stone statues

have been partially dissolved by acid rain.

Taj Mahal in Agra is also due to acid fumes

from refinery. suffering Mathura Acid Rain
Effects on Sculptures
Effect on Soil
Acid Rain also affects the soil by the soil neutralizing the acids.

Soils that contain Limestone and Calcium Carbonate can neutralize

the acids.

Leaching- a process in which acid deposition adds hydrogen ions

which displaces important nutrients like Calcium, Magnesium, and
Potassium.

Leaching pushes the ions deeper in the soil so the plants roots can’t
reach them.
Effect on Fish
During the winter dangerously acidic pollutants have built up in the
snow and when the snow melts in spring all the acid drains into the water
system killing many fish.
Even those who survive suffer from Acid Stress
Other affect on the fish are reduced egg composition, decreased growth,
inability to regulate there own body chemistry, and deformities in young
fish and increased susceptibility to naturally occurring diseases.
These mass fish disappearances affects the birds and eventually our
whole ecosystem.

Destruction of Forests and Natural Resources

The extinction of the plants and animals leads to diminished gene pool.
The lack of biodiversity and a reduced planetary gene pool could have many
unforeseen consequences, some of which could be fatal to the future of humanity.
Acid Rain can contaminate drinking water supplies . If someone were to drink
water from this supply then they could sustain many health related problems.
AIR POLLUTION CONTROL TECHNIQUE

By
Dr.Pallavi Das
Assistant Professor
Deptt. of Environmental Science
IGNTU
Course Title: Environmental Pollution
and Control Technique-I
M.SC 2nd Semester
 Objectives of control equipment

 Prevention of nuisance

Prevention of physical damage to property

Elimination of health hazards to plant personnel

 Recovery of valuable waste product

Minimization of economic losses

Improvement of product quality

Control Devices for Particulate Contaminants:
(1) Gravitational Settling Chamber
 Vs= hV/ L ----------- (i)
L= length of chamber
V= horizontal velocity of carrier gas
Vs= settling velocity of particulates
h= height through which particulates travel before settling down

By stokes law
Vs= g(ρp- ρ)D2/18μ --------- (ii)
D= dia of particle; g= acceleration due to gravity; ρp= density of
particle; ρ = density of gas; μ= viscosity of gas

From eq- i and ii

D= [18Vhμ/ Lg (ρp- ρ)]1/2

D = is minimum size of particle that can be removed in a settling

chamber
(2) Cyclone Separators (Reverse flow Cyclone)

Instead of gravitational force, centrifugal force is

utilized by cyclone separators, to separate the
particulate matter from the polluted gas.

 A simple cyclone separator consists of a cylinder

with a conical base. A tangential inlet discharging
near the top and an outlet for discharging the
particulates is present at the base of the c

The dust laden gas enters tangentially, receives a

rotating motion and generates a centrifugal force
due to which the particulates are thrown to the
cyclone walls as the gas spirals upwards inside the
cone.

The particulates slide down the .walls of the cone

and are discharged from the outlet.
 (3) Fabric Filters (Baghouse Filters)

In a fabric filter system, a stream of the

polluted gas is made to pass through a
fabric that filters out the particulate
pollutant and allows the clear gas to pass
through.

The particulate matter is left in the form

of a thin dust mat on the insides of the bag.

This dust mat acts as a filtering medium

for further removal of particulates
increasing the efficiency of the filter bag to
sieve more sub mi-cron particles (0.5 µm).
A typical filter is a tubular bag which is closed at the upper
end and has a hopper attached at the lower end to collect the
particles when they are dislodged from the fabric.

Many such bags are hung in a baghouse.

For efficient filtration and a longer life the filter bags must
be cleaned occasionally by a mechanical shaker to prevent too
many particulate layers from building up on the inside
surfaces of the bag.
 APPLICATION

 Metallurgical Industry

 Foundries

 Cement Industry

 Chalk and Lime

 Brick Works

 Ceramic Industry

Flour mills
 Electrostatic precipitators
Works on the principle of electrical charging of particulate
Matter (-ve) and collecting it in a (+ve) charged surface. 99%
efficiency. Can remove particle size range of 0.1 μm to 1 μm.

 Six major components

 A source of high voltage
Discharge electrodes and collecting electrodes
Inlet and outlet for gas
A hopper for disposal of collected material A
An electronic cleaning system
An outer casing to form an enclosure around electrodes
Principles
 Gas stream passed two electrodes.
High potential difference is maintained.

 Out of two electrodes, one is discharging other collecting.

 Potentials of 100 kv are used. Ionization creates active glow zone

called “corona”.

Gas ionization is dissociation of gas molecules into free ions. As

particulates pass through field, they get charged and migrate to
oppositely charged electrode.

Particles deposited on collecting electrodes, lose charge and removed

mechanically by rapping., vibration or washing to a hopper.
Single stage and two stage precipitators

Single stage gas ionization and particulate collection in a

single stage.

 Two stage, particle ionized in first chamber and collected

in second chamber.

Industrial precipitators single stage design.

 Two stage used for lightly loaded gases.

 Single stage for more heavily loaded gas streams.

Advantages
High collection efficiency.
Particles may be collected dry or wet.
 Can be operated at high temp. (300-450˚c).
 Maintenance is normal.
Few moving parts

 Disadvantages
High initial cost.
Require high voltage.
Collection efficiency reduce with time.
 Space requirement is more.
 Possible of explosion during collection of combustible gases
or particulates.
Applications

Cement factories

 Pulp and paper mills

Steel plants

 Non- ferrous metal industry

 Chemical industry

Petroleum industry

Carbon black industry

 Electric power industry

(5) Wet Collectors (Scrubbers):

In wet collectors or scrubbers, the particulate contaminants are

removed from the polluted gas stream by incorporating the
particulates into liquid droplets.

Common wet scrubbers are:

(i) Spray Tower

(ii) Venturi Scrubber

(iii) Cyclone Scrubber

 (i) Spray Tower

Water is introduced into a spray tower

by means of a spray nozzle (i.e. there is
downward flow of water).

As the polluted gas flows upwards, the

particulates (size exceeding 10 µm) present
collide with the water droplets be-ing
sprayed downward from the spray nozzles.

Under the influence of gravita-tional

force, the liquid droplets containing the
particulates settle to the bottom of the
spray tower.
 (ii) Venturi Scrubber

Submicron particulates (size 0.5 to 5 µn)

associated with smoke and fumes are very
effectively removed by the highly efficient

Venturi Scrubbers. Venturi Scrubber has

a Venturi shaped throat section.

The polluted gas passes downwards

through the throat at the velocity of 60 to
180 m/sec.
A coarse water stream is injected upwards into the throat where
it gets atomised (i.e. breaks the water into droplets) due to the
impact of high velocity of the gas.

The liquid droplets collide with the particulates in the polluted

gas stream.

The particles get entrained in the droplets and fall down to be

removed later on.

Venturi Scrubbers can also remove soluble gaseous

contami-nants. Due to the atomisation of water there is proper
contact between the liquid and the gas increasing the efficiency of
the Venturi Scrubber (their power cost is high because of the high
inlet gas velocity).
 (iii) Cyclone Scrubber

The dry cyclone chamber can be

converted into a wet cyclone
scrubber by in-serting high pressure
spray nozzles at various places
within the dry chamber

The high pressure spray nozzles

generate a fine spray that intercepts the
small particles in the polluted gas. The
centrifugal force throws these particles
to-wards the wall from where they are
drained downwards to the bottom of the
scrubber.
 (d) Vegetation:

Plants contribute towards controlling air-pollution by utilizing

carbon dioxide and releasing oxygen in the process of photosynthesis.
This purifies the air (re-moval of gaseous pollutant—CO2) for the
respiration of men and animals.

Gas-eous pollutants like carbon monoxide are fixed by some plants,

namely, Coleus Blumeri, Ficus variegata and Phascolus Vulgaris.
Species of Pinus, Quercus, Pyrus, Juniperus and Vitis depollute the air
by metabolising nitrogen oxides.

Plenty of trees should be planted especially around those areas which

are de-clared as high-risk areas of pollution.
(e) Zoning:
This method of controlling air pollution can be adopted at the
planning stages of the city. Zoning advocates setting aside of
separate areas for industries so that they are far removed from
the residential areas. The heavy industries should not be located
too close to each other.
Control of gaseous pollutants from stationary
sources

 The most common method for controlling gaseous

pollutants is the addition of add-on control
devices to recover or destroy a pollutant.
• There are four commonly used control
technologies for gaseous pollutants:
– Absorption,
– Adsorption,
– Condensation, and
– Incineration (combustion)
Equipments using principles of absorption for removal of
gaseous pollutants

Packed tower

 Plate tower

Bubble cap plate tower

Spray tower

 Liquid jet scrubber absorbers

 Absorption
 Effluent gas passed through absorbers (scrubbers), which
contain liquid absorbent.

 Efficiency depends on
1. Amount of surface contact between gas and liquid
2. Contact time
3. Conc. of absorbing medium
4. Speed of reaction between the absorbent and gases

 Absorbents used to remove SO2, H2S, SO3, F and oxides of

nitrogen.
 Adsorption
 Surface phenomenon, require large solid surface

 Adsorption towers use adsorbents to remove the impurities

from the gas stream.

 The impurities bind either physically or chemically to the

adsorbing material.

The impurities can be recovered by regenerating the

adsorbent.

Adsorption towers can remove low concentrations of

impurities from the flue gas stream.
Construction and Operation

 Adsorption towers consist of cylinders packed with the adsorbent.

 The adsorbent is supported on a heavy screen.

 Since adsorption is temperature dependent, the flue gas is temperature

conditioned.

 Vapor monitors are provided to detect for large concentrations in the

effluent. Large concentrations of the pollutant in the effluent indicate that
the adsorbent needs to be regenerated.

Advantages of Adsorption Towers

Very low concentrations of pollutants can be removed.
 Energy consumption is low.
 Do not need much maintenance.
 Economically valuable material can be recovered during regeneration.
 Condensation

 Condensation is the process of converting a gas or

vapor to liquid. Any gas can be reduced to a liquid by
lowering its temperature and/or increasing its pressure.

• Condensers are typically used as pretreatment devices.

They can be used ahead of absorbers, absorbers, and
incinerators to reduce the total gas volume to be treated by
more expensive control equipment. Condensers used for
pollution control are contact condensers and surface
condensers.
 Incineration
Incineration, also known as combustion, is most used to control
the emissions of organic compounds from process industries.
This control technique refers to the rapid oxidation of a
substance through the combination of oxygen with a combustible
material in the presence of heat.
When combustion is complete, the gaseous stream is converted
to carbon dioxide and water vapor.
Equipment used to control waste gases by combustion can be
divided in three categories:
Direct combustion or flaring,
Thermal incineration and
Catalytic incineration.
 ECONOMICAL ASPECTS

1. Cyclones:- cheap to install, power consumption

moderate, maintenance cost normal.

2. Filters:- expensive to install, power consumption

moderate. Maintenance cost high.

3. Electrostatic precipitators:- most expensive

regarding installation, power consumption moderate
to low as pressure drops. Maintenance cost moderate

4. Scrubbers :- installation cost moderate, maintenance

cost not high, high rate of power consumption.