Presentation Topic On: Air Pollution by computer 6th sem

Environmental Chemistry
• In simple word we can say that the study of
effect human activities on chemical processes in
the environment/nature that is called by
environmental chemistry
• Environmental chemistry is one of most
important branch of the environmental science.
The field of chemistry that deals with study of
reactions, sources, transport, effect along with
facts of all the chemical species present in soil,
water and air environment and also effect of
technology theorem.

Some scope of
Environmental chemistry
1. Environmental chemistry is applied in the waste
management and cleaner production.
2. Environmental chemistry is applied in the study of new
products and their effects on the environment.
3. It is used in the method of protection of groundwater
which is polluted by soil, dust, and the waste particles.
4. It studies the risk of all the chemical in the depth to get
a solution for the safety purpose of the environment.
5. It is used for protection of surface water from
contaminants through the process of bacteria and
radiation etc.

Nomenclature
→ A system through which, organism, including
plants, animals microorganism and other living
beings are given distinct scientific names is
called by nomenclature.
Environmental Segment
→The environment consist of various segments
such as atmosphere, hydrosphere, lithosphere
and biosphere.

 A natural process in which elements are
continuously cycled in various forms between
different compartments of the environment
(e.g., air, water, soil, organisms).
Examples include the carbon, nitrogen and
phosphorus cycles (nutrient cycles) and the
water cycle.

Some natural cycles are:
1. Carbon Cycle
2. Nitrogen cycle
3. Phosphorus cycle
4. Water cycle

1.Carbon Cycle
• The carbon cycle includes the uptake of
carbon dioxide by plants through, its ingestion
by animals and its release to the atmosphere
through respiration and decay of organic
materials. Human activities like the burning of
fossil fuels contribute to the release of carbon
dioxide in the atmosphere.

2. Nitrogen cycle
• The nitrogen cycle involves the uptake of
nitrogen form the atmosphere by a process
called fixation which is carried out by microbes
or industrial processes. Decomposition of
biological waste by microbes can return
nitrogen to the atmosphere. Nitrogen is
mainly used by humans as a fertilizer in
farmlands, but its excessive usage can lead to
serious problems (such as eutrophication).

3. Phosphorus cycle
• The phosphorus cycle involves the uptake of
phosphorus by organisms. Phosphorus in the
environment is mainly found in rocks, and
natural weathering processes can make it
available to biological systems. After
decomposition of biological waste, it can
accumulate in large amounts in soils and
sediments. Phosphorus is used by humans as a
fertilizer in farmlands and in detergents.
Overuse of phosphorus can lead to
eutrophication.

4. Water cycle
• The water cycle is the process by which water
travels in a sequence from the air
(condensation) to the earth (precipitation) and
returns to the atmosphere (evaporation). It is
also referred to as the hydrologic cycle.
• Human use of water can transform the water
cycle through irrigation or the construction of
dams, for example.

Air pollution
• Air pollution may be defined as the 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 most crucial from the public health
point of view, because every individual person
breathes approximately 22,000 times a day, inhaling
15-22kg of air daily . Polluted air causes physical ill
effects, besides undesirable aesthetic and physiological
effects.

Causes of air pollution
The causes of air pollution are summarized
below:
1. Population explosion
2. Industrialization
3. Urbanization
4. Automobiles
5. Natural phenomena : volcanic eruptions,
radioactivity, forest fires, etc.

Air pollutants
On the basis of the physical state, there are four major
groups of air pollutants:
A. Gases
Gases mix freely with air without settling down . These
gases are:
i) Oxides of sulphur (SOx)
Sulphur dioxide (SO2) and sulphur trioxide (SO3) are
important forms of primary pollutants in atmosphere . The
mixture of SO2 and SO3 is commonly represented as SOx .

Sulphur dioxide (SO2)
• It is emitted from thermal power plants, in
which sulphur containing coal and diesel are
fired. Other sources are petroleum industry ,
oil refineries, sulphuric acid plants and
sulphide ore-roasting plants.

Sulphur dioxide (SO2)
• The presence of this gas in the atmosphere
causes cardiac (heart ) diseases, respiratory
diseases , eye irritation , throat troubles , etc.
to man .
• Some effects in atmosphere on plant cells are
membrane damage, chlorophyll destruction ,
metabolism inhibition , growth-yield
reduction, etc.

Sulphur trioxide (SO3)
• It is formed by the oxidation of sulphur dioxide under the
influence of sunlight . Even 1ppm of SO3 in air causes
severe breathing discomfort and irritation to the
respiratory tract.
• Secondary pollutants such as H2SO4 produced from the
sulphur dioxide can damage the building materials.

Controls of SOx Emission
There are following four possible methods to
the removal and control of SOx emission:
• Reduction of SO2 in flue gases.
• Removal of sulphur from fuel burning.
• Use of low sulphur fuels.
• Substitution of others energy sources for fuel
combustion.

ii) Oxides of nitrogen (NOx)
• Oxides of nitrogen like NO, NO2 are produced
from the combustion of fuels (coal, petrol,
diesel, etc.) .
• Other sources are acid manufacture , explosive
industries , etc. Because of continuous increase
in the number of vehicles, power plants,
industries, etc. The pollution due to nitrogen
oxides is increasing day-by-day.

Oxides of nitrogen contd…
• Nitrogen oxides are among the most toxic
substances . NO is biochemically relatively inert.
However NO2 is about four times toxic than NO.
• In high NO2 areas respiratory illness among children
have been reported. It is unpleasant in odour and
leads to irritation of eyes and even lung’s congestion.
• Exposure of plants for long time to the high
concentration of NO2 cause leaf spotting, breakdown
of plant tissues ,etc.

Oxides of nitrogen contd….
• No direct effect of NOX have been noticed
among building materials . However
secondary pollutants such as HNO3 produced
from nitrogen oxide can damage the building
materials.

Control of NOX
• Fuel burn out completely at relatively low
temperatures in excess of air . The low
temperature prevents the formation of NO
and therefore control its emission.
• Use of selective catalytic converter for
catalytic reduction . For example NH3 , CO ,
etc. may reduce NOX in exhaust gas .

iii) Oxides of carbon ( CO and CO2)
Carbon monoxide (CO)
• Carbon monoxide (CO ) is released by the
partial combustion of fuel in automobiles,
industries, and oil refineries . Cigarette and
bidi smoke and domestic heat appliances are
other sources of CO.
• The basic chemical reaction yielding CO are as
follows.

Oxides of carbon contd….
• Carbon monoxide is non-irritating gas . Mostly it is referred as
silent killer as it is highly toxic . Carbon monoxide react with
red pigment haemoglobin to form carboxy-haemoglobin.
• As a result blood can not absorb oxygen and thus the
transport of oxygen to the various part of body decreases .
Thus the air containing CO may be fatal to us.

Control of CO emission
• Modification of internal combustion engines for
reducing the amount of pollutants formed
during fuel combustion.
• Development of exhaust system reactors which
will complete the combustion process and emit
CO2 , a more acceptable material into
atmosphere.
• Development of pollution free power sources to
replace the internal combustion engines.

Carbon dioxide (CO2)
• Carbon dioxide is released into the atmosphere in the
form of smoke which is produced by burning fuels such
as coal, wood , petroleum products , and gaseous fuels.
• The excess of CO2 in the atmosphere causes respiratory
disorders and suffocation.
• CO2 gas in the atmosphere perform major role of heating
up of atmosphere due to trapping of infrared rays (from
sun) . This is called green house effect.
• To control emission of CO2 consumption of fossil fuels
such as coal , petroleum , etc. should be minimized.

iv) Hydrocarbons
• Sources of HC are petroleum 55% , coal 3.3% , wood 2.2%
, refuse burning 28.3% , solvent evaporation 11.2%.
• High concentration of hydrocarbons affect lungs and
cause swelling when they enter the lungs.
• Inhalation of aromatic hydrocarbon vapours cause greater
ill effects like irritation to mucus membrane , respiratory
problems, lung cancer , affect nervous system and may
even lead to death.
• Hydrocarbons are also responsible for the photochemical
smog.

Control of hydrocarbons
• Hydrocarbons can be controlled in the
atmosphere by removal of chemical and
photochemical reactions.

B) Particulates
• Small solid particles and liquid droplets are known as
particulates. These are present in atmosphere in fairly
large numbers and sometimes cause a serious air
pollution problem.
• The sources of particulates are volcanic eruptions,
blowing of dust particles by wind , spraying of salts
and others solid particles by the seas and ocean, etc.
• The contribution from man-made activities are fly ash
from power plants , smoke from incomplete
combustion process, etc.

Particulates contd..
• Due to the very small size of particulates , they have
ability to penetrate into the deep air passage and may
remain for years in the innermost region of the lungs and
there is no effective mechanism for particle removal.
• Particulates have harmful effects on human health such
as chronic bronchitis , asthma , respiratory disorder ,
kidney damage and cancer. They have adverse effect on
climate by in-balancing radiation and heat . They have
harmful effect on materials such as damage to building,
sculpture , etc.

Control of particulates
The techniques of remedies of particulates are
as follows :
• Cyclone collectors
• Electrostatic precipitators
• Wet scrubbers
• Settling chambers

C) Deforestation
• Green plants use CO2 for the manufacture of
food by photosynthesis and give out O2 ,
Thereby purifying the atmospheric air .
• Plants also control hydrogen sulphide , nitric
acid and chlorine . Thus plants help in
controlling the air pollution .
• Excessive cutting of trees , consequently,
causes indirectly air pollution.

D) Internal combustion engines
• One of the major man-made air pollutant is
the internal combustion engine for running
motorcars, buses, planes, trucks, scooters, etc.
When fuel like kerosene , diesel , petrol is
burnt , a lot of smoke is released into the
atmosphere.
• Following ways can reduce the air pollution
due to the internal combustion engines :

Internal combustion engine contd…
• By using engine with better design .
• By using suitable catalyst in the fuel.
• By mixing the exhaust gases with more air.
• By improving the quality of gasoline by adding
tetraethyl lead (TEL) .
• By using catalytic converter in automobile
engine.

Control of air pollution
The best way to control air pollution is to reduce or to prevent
the formation of pollutant at the source itself . Various air
pollution control methods are :
• The air pollution due to oxides of nitrogen , oxides of sulphur
and oxides of carbon can be controlled by …....…( see above)
• The air pollution due to hydrocarbons can be controlled by
…....…(see above)
• The air pollution due to particulates can be controlled by
…....…(see above )
• The air pollution due to internal combustion engines can be
controlled by …....…(see above)

Control of air pollution contd…
• Effluents from industries must be treated before
discharging into the atmosphere.
• The use of tall stacks or chimneys reduce the
concentration of air pollutants at the ground
level. The gases discharged through the stacks get
diluted and are dispersed into the atmosphere.
• Alternate source of energy such as solar energy ,
electricity , bio-gas can be used .
• Regular maintenance of vehicles is necessary.

Control of air pollution contd…
• Intensive afforestation is necessary to control air
pollution. Public awareness about air pollution and it’s
effect is one effective means to reduce air pollution.
• The amount of smoke produced by households can
be reduced by use of smokeless chulhas , solar
cookers and biogas.
• It is desirable to have a suitable “buffer zone”
between industrial units and houses in order to
facilitate dilution of air pollutants to such a degree
that it is harmless to children also.

Q. What are particulates? Classify particulates,
and discuss in brief its effects on human .
Particulates or particulate matter is the sum of all solid and
liquid particles suspended in air . This complex mixture
includes both organic and inorganic particles.
Particulates are classified as follows:
1. Dust –Main sources of dust are mines and quarries, power
houses, vehicular traffics , house cleaning dust , natural
winds, etc.
2. Smoke – The major sources of smoke emission are rails ,
open fires , industrial power plants, diesel engines,
automobiles , furnaces, hearths, etc.

Classification of particulates contd…
3. Smog – It is a mixture of smoke (from coal
combustion ) and fog in suspended droplet from.
4. Fly ash – It is the fine ash from pulverized fuel (coal)
burned in power stations.
5. Asbestos (the fibrous silicate mineral) – Widely
used in industry for its mechanical strength and
resistance to heat especially as thermal insulation
materials and in high temperature applications, where
the high chemical stability of the silicate serves well.

6. Lead – It is known to be toxic to human
metabolism but, still it is widely used in our
society .Lead content in human blood
exceeding a 40 ppm is considered dangerous.
One symptom of lead poisoning is anaemia . It
enters the body either as inorganic lead ( Pb2+
)
ion or as tetraethyl lead.

7. Mercury – The toxicity of mercury depends very much
on its state. Pure mercury is not particularly poisonous ;
in fact ingestion of small amount of mercury (e.g. from
the dental amalgam ) produces no noticeable ill effects,
since the metal apparently passes through the body
without undergoing chemical change . On the other
hand, mercury vapour is dangerous.
8. Cadmium – Cadmium produced from the industrial
processes is very toxic to the living organism, even in
low concentration of less than 1 mg/L .

Effects of particulates on human
1. Due to very small size of particulates, they may
penetrate into the deep air passage and may
remain for years in the innermost regions of the
lungs, which have no effective mechanism for
particle removal.
2. On man, atmospheric dust causes allergic and
respiratory disease , silicosis, if dust contains silica.
3. The incidence of cancer is being increasingly
related with smoke.

Effects of particulates on human contd…
4. Photochemical smog causes:
- Irritation of eyes and lungs.
- May damage plants.
- Irritation to nose and throat.
- Increased chances of asthmatic attack and
mortality.

Effect of particulates on human contd…
5. It is known that lead ions inhibit at least two
enzymes that catalyze the reactions for
biosynthesis of haemoglobin . Consequently,
one symptom of lead poisoning is anaemia .
6. Mercury vapour causes irritation and
destruction of lung tissues. Mercury in vapour
form adversely affect the neurological behavior
of humans.

Water Pollution
• Water found in the environment is used directly by man
for providing food and drink , personal and domestic
hygiene , recreation, agriculture, transport and industry.
• The word polluted water is defined as water that does
not meet even the minimum standards for any function
and purposes for which it would be suitable in its
natural state.
• The concept of water pollution may alternatively be
defined as “any alternation in the physical (e.g.
temperature), chemical and biological properties of
water as well as contamination with any foreign
substance, which would constitute a health hazard or
otherwise decreases the utility of water. ”

Sources of water pollution
1. Domestic sewage: The release of huge quantities of
domestic wastes by drains into the canals and rivers cause
the pollution of rivers. The sewage contains human feces,
urine , kitchen wastes , street wastes and organic
substances that provide nutrition for bacteria and fungi.
2. Industrial wastes : Water gets polluted by acids, alkalis,
detergents, soaps, phenols , cyanides, copper, zinc , lead,
mercury , pesticides, insecticides and fungicides, etc.
which are released from chemical industries . Pollution is
also caused by the wastes of industries like leather
tanneries, sugar, paper, breweries , slaughter houses ,
textiles, steel mills , soap, distilleries , oil refineries ,
pharmaceuticals, etc. Water containing toxic substances
damage the biological activity and kills useful organisms.

Sources of water pollution contd…
3. Run-off from land and fields : Residual
pesticides, fungicides , insecticides etc. are washed
down into rivers , lakes etc. and pollute them.
4. Suspended particles : The surface water ,
sometime contains a high concentration of
suspended solids (organic as well as inorganic ),
bacteria , viruses , protozoa , algae, etc. This makes
water unfit for industrial as well domestic
purposes.
5. Oil from oil spills or leakage from tankers
carrying petroleum and washing of automobiles
also pollute our rivers.

Sources of water pollution
6. Atomic explosion and processing of radioactive
materials near the sources of water cause water
pollution.
7. Waste from fertilizer plants containing nitrates,
phosphates, ammonia, etc. are released in water
and they all cause water pollution.
8. Clay , ores, fine particles of soil on which water
travels are also added to water sources and they all
cause water pollution.
9. Agricultural discharge such as pesticides ,
insecticides , plants nutrients, fertilizers ,
herbicides, farm wastes, etc. cause water pollution.

Sources of water pollution contd…
10. By bacteria, viruses , algae and diatoms ( like
protozoa): These cause bacterial pollution , which is
due to the presence of mammals like dead bodies of
man , wild and domestic animals, birds, etc. in water
bodies . They degrade the quality of water.
11. By run-off from urban areas : Effluents from
urban areas containing substance like oils, grease
detergents, nutrients, heavy metals , etc . Cause
water pollution.
12. Natural rocks and soil from which arsenic leaks
into water .

Effects of water pollution
1. Water is the carrier of pathogenic microorganisms and
can cause immense harm to public health. The water
borne diseases are typhoid , dysentery , cholera ,
infectious hepatitis, etc.
2. Domestic wastes and untreated sewage create foul
smell in water as well as in air.
3. Air pollutants like oxides of nitrogen and sulphur cause
acid rain that changes the PH
of water.
4. Oil spill and leakage covers the water surface and
prevents atmospheric oxygen from mixing with water . It
adversely affects the fish fauna and aquatic organism .

Effects of water pollution contd….
5. Excessive addition of fertilizers (nitrates and
phosphates) from agricultural waste water into
aquatic system causes eutrophication , which leads
to the depletion of oxygen in water due to excessive
growth of algae, thereby BOD of water is increased.
This leads to death of fish and other aquatic life.
6. Heated water discharged into water bodies
results in an increase in the temperature of water
which depletes the dissolved oxygen. It is injurious
to aquatic flora and fauna.

Effects of water pollution contd….
7. Heavy metal like mercury causes numbness of limbs,
lips, and tongue. It also produces blurred vision ,
deafness, mental disorders. Mercury poisoning was first
discovered in Japan and was called minamata disease. In
lethal dose (0.5-1.0 gm), it damages kidney.
8. Compounds of lead , arsenic and cadmium are slow
poisons which cause skin disease, anaemia , headache,
vomiting , liver and kidney damage , gastrointestinal
damage and nerve disorders, etc.
9. Water polluted with radioactive substances and toxic
materials may cause poisoning , reproductive disorder ,
birth defect , genetic defect and cancer in human beings
and animals .

Effects of water pollution contd…
10.Nuclear weapons testing in air , leakage from
underground nuclear detonations, etc. give to
radioactive fallout. The latter shows far reaching
effects on the environment and mankind. 90
Sr , a
long lived component of radioactive fallout is
chemically similar to Ca and accompanies Ca in soil.
Plants and animals and finally in bones and teeth.
The presence of 90
Sr in bones leads to disorders in
blood cell formation and causes anaemia or more
serious disorders.

Water pollution control methods
The problem of water pollution can be reduced by
using following techniques :
1.Stabilization of ecosystem by reduction of wastes ,
trapping of nutrients , fish management , aeration, etc.
2.Recycling of the waste water by suitable treatment,
before its discharge into water bodies. Methods like
aeration and use of trickling filter can be employed for
treating sewage waste.
3.Waste-water reclamation : for example sewage water
can be directly used for irrigation and fish-farm raising
purposes, since it contains all essential nutrients such as
N, P and K to make it a good manure.

Water pollution control methods contd…
4.Use of chemicals : Effective filtration, followed by
chlorination of waste water can provide safe water for
drinking and domestic use.
5. Dilution of waste water before their discharge into
water bodies : Dissolved oxygen of the diluting water
causes petrification of waste water due to
biodegradation of organic compounds (aerobic) by
bacteria (present in waste water), thereby effective
concentration of organic matter in the diluted waste
water decreases considerably. Evidently, the greater
the pollution load in waste water , greater is the
dilution required.

Water pollution control methods contd…
6.Removal of pollutants like phosphorus
compounds , mercury, ammonia, sodium salts ,
phenolic compounds , etc. using special
techniques such as adsorption , ion-exchangers,
electrodialysis , reverse osmosis, etc.
7. Different types of settlement techniques like
formation of precipitates can be applied.
8. Industrial and household waste water should
not be discharged directly into water bodies.

Soil pollution
• Soil is the thin layer of organic and inorganic
materials that covers the earth’s rocky surface.
• Soil pollution is the addition of some chemical
substances in an indefinite proportion to the
soil system , whereby the fertility of soil
changes.
• Any substance capable of changing the
productive capacity of the soil is termed as soil
pollutant.
• The polluted soil produces inferior quality of
crop.

Sources of soil pollution
• Improperly disposed human and animal excreta , solid
and liquid waste .
• Domestic refuge and industrial wastes dumped on land
.
• Dumping of wastes from mineral and coal mining and
metal smelting on land.
• Chemicals like fertilizers, pesticides , insecticides, etc.
applied to plants and soil.
• Radioactive wastes discharged from industrial and
research centers and hospitals.

Sources of soil pollution contd…
• Soil gets polluted by the removal of upper
fertile layer.
• Soil erosion due to deforestation, over-
grazing, unplanned irrigation and defective
agricultural practice.
• Pollutants present in air and fall out from
smoke stacks of chemical works.

Sources of soil pollution contd…
• Environment consists of gases like SO2 , NO2 , etc. SO2 present in air undergoes
oxidation to form SO3 and may further react with rain water or moisture to form
H2SO4.
Similarly , NO2 reacts with rain water or moisture in the presence of O2 and produces
HNO3.
So formed H2SO4 and HNO3 come down the earth as acid rain through the atmosphere.

Effects of soil pollution
a) Effect on environment
• Agrochemicals when sprayed on plants ,
affects all organisms directly or indirectly
through food chain , thus have adverse effect
on soil and water ecosystems including birds,
fishes , etc.
• Metallic contaminants ( Hg, Pb , Zn , As , Cr ,etc.
) destroy the beneficial microorganisms in soil.

Effects of soil pollution
• Industrial wastes containing various chemicals
are extremely toxic to living beings.
• Solid wastes dumped in soil decreases the
quality of soil. Hence it affects its fertility
reducing plant productivity.
• Overgrazing and deforestation leads to partial
or complete loss of soil fertility.

Effects of soil pollution contd….
b) Effect on human health
• Agrochemicals especially organic pesticides
that enter human body by biomagnifications
cause cirrhosis of liver , nervous disorder , and
sexually defects.
• Excessive use of fertilizers contaminate water ,
when consumed such water affects digestive
system and also reduces oxygen carrying
capacity of haemoglobin.

Soil pollution control methods
1) Using sanitary landfills i.e. where untreated waste is
buried in layers and covered with earth.
2) Soil pollution from agricultural waste can be reduced
by
• Controlling the use of chemical pesticides and fertilizers
and giving priority to bio-pesticides and bio-fertilizers.
• Utilizing the agricultural wastes in various ways such as
production of biogas from animal refuge , compost from
discarded vegetables and fruits .
• Applying proper drainage system while irrigating the
crop fields so that water logging can be prevented.

Soil pollution control methods contd….
3) Industrial garbage should be treated before
dumping .
4) Soil pollution from domestic garbage can be
controlled by
• Establishment of dumping site far from urban
areas .
• Recycling of garbage like paper, glass , tin , iron ,
etc.
• Producing compost from biodegradable wastes .

Soil pollution control methods contd….
5) An important aspect is to create public awareness
about pollution hazards.
6) Afforestation should be encouraged . Forestation
also helps to check the spread of desert.
7) Chemicals which have relatively high immediate
as well as persistent toxicity ( aldrin , dieldrin ,
arsenic compounds , etc. ) may be used in special
situations only and not for general use.

Soil pollution control methods contd…
8) High concentration of lead and cadmium can
be controlled by growing a special type of grass .
9 ) Crop rotation should be adapted to revive
the depleted nutrients in the soil .

ACID RAIN
• Various industries , automobiles, etc. release
acidic oxides such as Sulphur dioxide , nitrogen
dioxide etc. Natural HCl emissions and other
man-made activities also release HCl in the
atmosphere.
• These oxides and HCl dissolve in moisture
present in atmosphere to form corresponding
acids , which slowly fall on earth as acid rain.
• Acid rain is a process of deposition of acid
gases (SO2 , NO2 , HCl) from the atmosphere on

• More acid rains are likely to occur in the
following areas:
• Thickly populated cities.
• Areas having large number of industries.

Harmful effects of acid rain
• Increased extent of acid-rains ,during the past years ,has
progressively increased the acidity of rain water.
• Causes damage to fresh water-life.
• In mist form ,it causes direct damage to plant leaves.
• Lowering of PH
of rain-water due to acid rain changes the
rate of metabolism of organisms.
• Causes irritation to eyes and mucus membrane.
• Accelerate the rate of corrosion of metals.
• Causes damage to building, rocks, etc., thereby causing
faster weathering of these.
• Dissolves salts in the soil( e.g. CaCO3) and metals (like
aluminium) which pass into ponds, lakes , river, etc., where
they cause toxic effects to aquatic life.

Methods to control acid rain
• One of the most fundamental acid rain solutions is to utilize
fuels that burn more cleanly, or to burn coal more efficiently.
This will greatly reduce the possibilities of acid rain developing
in the atmosphere.
• ii. As fast as industrial power plants are concerned, the best
solution is to attach devices known as ‘scrubbers’ in the
chimneys of these plants. These scrubbers reduce the amount
of sulfur produced in the smoke by 90 – 95% .
• iii. Vehicles and cars must be mandatory required to comply
with very tight and efficient emission standards. Fitting
catalytic converters into the exhaust pipes of vehicles also
reduces the amount of sulfur dioxide produced by the
vehicles.

Methods to control acid rain
• For industrial power plants, there are many more acid rain
solutions that must be enforced, as they are clearly the
biggest contributors to the formation of acidified water
droplets in the atmosphere. Industries must regularly
inspect and clean all their emission equipment and
chimneys and pipes.
• All these acid rain solutions will be pointless unless people
are informed and educated about the ill-effects and harms
of acid rain. A widespread and nationwide effort must be
made to make people aware. Only after that is done ,all
the acid rain solutions actually make a difference.

ALKALINITY OF WATER
• Alkalinity is the name given to the quantitative capacity
of an aqueous solution to neutralize an acid . Alkalinity
roughly refers to the amount of bases in a solution that
can be converted to uncharged species by a strong acid.
• The alkalinity of water is due to presence of
i) soluble hydroxides only
ii) soluble carbonates only
iii) soluble bicarbonates only
iv) mixture of soluble hydroxides and carbonates
v) mixture of soluble carbonates and bicarbonates of
alkali and alkaline earth metals.

Alkalinity of water contd ….
• The possibility of hydroxides and bicarbonates existing together is
ruled out owing to the fact that they combine with each other
forming the respective carbonates.
OH-
+ HCO3
-
CO3
- -
+ H2O
• The type and extent of alkalinity present in water sample is
conveniently determined by titrating an aliquot of the sample
with acid using phenolphthalein to detect end point, (P) and then
continuing the titration with methyl orange to another end point
(M) . The reaction taking place may be represented by the
following equations:

Alkalinity of water contd….
The volume of acid run down up to phenolphthalein end
point,(P) corresponds to the completion of reactions (1) and
(2) given above while the volume of acid runs down after (P)
corresponds to the completion of reaction ( 3).
The total amount of acid used from the beginning of
experiment to the methyl orange end point (M) corresponds
to the total alkalinity and represents the completion of
reactions shown by (1), (2) and (3).

The results may be summarized in the following table , from
which the amount of hydroxides , carbonates and bicarbonates
present in the water sample may be computed.
Alkalinity is expressed as parts per million (ppm) in
terms of CaCO3 or on degrees Clark.

Procedure
• 100ml water sample is taken out into a conical flask, 1 to 2
drops of phenolphthalein indicator is added and titrated against
standard HCl until pink color just disappears . The titer volume
is noted which corresponds to phenolphthalein end point,(P).
• Then 2 to 3 drops of methyl orange indicator is added to the
same solution and titration is continued until sharp color change
from yellow to red takes place. The total titer volume from the
beginning of experiment is noted as methyl orange end point,
(M).
• The experiments are repeated till the concurrent readings are
obtained.

OZONE LAYER
• Ozone is a pale blue gas mainly present in the
stratosphere in the form of layer known as
ozonosphere.
• It is an allotropic form of oxygen. Under
suitable conditions , these oxygen atoms
combine to triatomic molecules called ozone.
• Ozone is formed in the upper atmosphere by
the absorption of UV light.

Formation of Ozone
• O2 Splits into atoms as they absorb UV
radiation from the sun. The oxygen atom then
combines with O2 Molecule to give ozone
molecule.
O2 UV O + O
O2 + O O3

Importance of ozone layer
• The ozone layer acts as a protective shield for the existence
of life on earth. It absorbs most of the harmful ultraviolet
radiations coming from sun and thereby protects life from
several radiation damage.
• In the absence of ozone layer, these ultraviolet radiations
would cause
a) Diseases like skin cancer in men and animals, swelling of
skin, burning sensation, skin aging , leukemia , breast cancer,
haemorrhage , lungs injury , premature aging , inhibition and
alternation of DNA replication and formation of DNA adduct
and may even lead to death.
b) DNA mutation
c) Damage of plants
d) Faster deterioration of paints, fabrics, plastics, etc.

Causes of depletion of ozone layer
• Substances responsible for ozone layer depletion are
CFCs , CO , NO , NO2 , CH4, etc. The main culprits for
ozone layer depletion are chlorofluorocarbons(CFCs)
• Chlorofluorocarbons are extremely stable , non
corrosive and inert compounds containing
chlorine ,fluorine and carbon . They are also known as
Freon.
• The CFCs are CFCl3 (Freon-11), CCl2F2 (Freon-12) etc.
Chlorofluorocarbons are the exhausts of supersonic air
craft and jumbo jets flying in the upper atmosphere .
CFCs were also used as coolants in refrigerators , air
conditioners , etc

Causes of depletion contd……
• Once chlorofluorocarbons come in
atmosphere , they remain in environment for
along time and eventually migrate into the
stratosphere . Here, it destroys ozone
molecules.
• It is estimated that one molecule of CFC can
destroy 100,000 molecules of ozone . The
mechanism of destruction of ozone is as
follows.

Causes of depletion contd….
• Chlorine atom is consumed in reaction 2, but it is
generated in reaction 3. Thus, once chlorine atom
is produced from the decomposition of CFC ,
hundreds of thousands of molecules of ozone are
destroyed through the chain reaction . This creates
a depletion of ozone layer or ozone hole in
stratosphere.
• Another chemical reaction leading to the
decomposition of ozone layer is,

Control of ozone layer depletion
• Due to hazardous and ozone depleting nature of CFCs,
the need for their alternatives is quite necessary and
CFCs units be phased out as early as possible .
• These days Hydrochlorofluorocarbons (HCFCs) and
Hydrofluorocarbons (HFCs) are considered as ozone
friendly substitutes for CFCs in the air conditioning and
refrigeration on the basis of some toxicity tests and
environmental impacts . They have smaller atmosphere
life times and zero depletion to CFC’s potential as
compared . But they also possesses some toxicity ,so
these are only short term alternatives according to
Montreal protocol.

Control of ozone layer depletion
Other methods to control the depletion of
ozone layer are as follows:
1) Minimize high altitude aircraft flights.
2) Encourage growth of plants that produce
oxygen and discourage deforestation.
3) Decrease the releases of high temperature
steam to the atmosphere.
4) Eliminate production and release of known
ozone depleting chemicals as far as possible.

Presentation Topic On: Air Pollution by computer 6th sem

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