Acid Rain, Ozone depletion, Green House Effect and Global Warming

1. Global Environmental Issues
Acid Rain, Ozone depletion, Green House Effect and Global Warming

2. Factors which cause this issues
 Population explosion
 Rapid industrialisation
 Urbanisation
 Modern life style

3. Global Environmental Issues
Acid Rain
Ozone depletion
Green house effects
Global warming

4. Acid Rain
 When the pH of rain water is less than 5.6 , it is called as acid rain.
 The natural rain water has pH of 5.6 at 20
0
C due to formation of carbonic acid
due to dissolution of CO2 in water.
CO2 + H2O → H2CO3
 Oxygen, nitrogen and sulphur originating from industrial operation and fossil
fuel combustion are the major causes of acid rain formation.
2SO2 + O2 → 2SO3
SO3 + H2O → H2SO4
2NO + O2 → 2NO2
4NO2 + 2H2O + O2 → 4HNO3
 Sulphuric acid and nitric acid are the major acid found in the rain water.
 The proportion of sulphuric acid ranges from 60 to 70% and that of nitric acid is
30-40%

5. Causes of Acid rain :
SO2 and NOx are mainly responsible for
forming of acid rain. Main source of this
pollutants are
 Fossil fuel based power plants
 Smelting of sulfide ore
 Automobiles exhaust
 Industrial plant using sulphuric and nitric acid

6. Effects of acid rain
 Effects on building material :
acid rain will cause damage to
common building material such
as limestone and marbles.
CaCO3 + 2H+ → Ca2+ + CO2 + H2O
Many metals get oxidised. Iron
corrodes with the presence
of acid rain to form rust. The
cost of maintenance of iron
structures is high in highly
polluted areas
Fe + 2H+ → Fe2+ + H2
It detoriates surface of points.

7.  Effects on Aquatic life :
Aquatic life especially fish are badly affected by lack acidification. Acid rain mobilizes
heavy metals such as calcium & mercury in soil , rock & sediments which are then
leached
out by rain and enter the surface water. Acidified lake have levels of cadmium , lead ,
aluminium , manganese , zinc , copper & nickel . All these can kill living organisms if
present in sufficient quantities.
It disturb the food chain of aquatic ecosystem
It result in reproductive failure

8.  Effects on fertility of soil :
Due to high solubility of acidic rain water , plant nutrients like nitrogen ,
phosphorous and potassium gets leached away , which reduces fertility of
soil.
It damages foliage and weakens trees .
It makes trees more susceptible to
stresses like cold temperature ,
drought , etc. Many insects and
fungi are more tolerant to acidic
conditions and hence they can
attack the susceptible trees and
cause diseases.
It also make atmosphere hazy.

9. Control of acid rain
 Emission of SO2 and NO2 from industries and power
plants should be reduced by using pollution control
equipments .
 Liming of lakes and soil should be done to correct the
adverse effect of acid rain.

10. Ozone Depletion
A layer of ozone (O3) is present in the stratosphere 20-25 km above
the surface of earth. This layer filters our harmful ultraviolet radiation
from the sunlight , thus protects various life from on the earth.
It acts like a natural sunscreen for earth.
Formation of ozone layer: In the stratosphere ozone is continuously created by the
following reaction O2 + hv → O + O
Ultraviolet rays decomposes oxygen in to atomic oxygen by photolytic decomposition.
The atomic oxygen thus farmed rapidly reacts with molecular oxygen to form ozone.
O + O2 + M → O3 + M
( M is a third body necessary to carry away the energy released in the reaction. )
Ozone thus formed distributes itself in the stratosphere and absorb harmful ultraviolet radiation
(200-320nm) and it continuously converted back to molecular oxygen.
O3 + hv → O2 + O
The net result of above reaction is an equilibrium concentration of ozone.

11. Ozone Layer

13. Destruction of Ozone
The destruction is mostly caused by chlorofluoro-carbon (CFC).
CCl3F + UV → CCl2F + Cl
(CFC)
2(CCl2F2) + UV → CClF2 + CClF2 + 2Cl
Cl + O3 → ClO + O2
ClO + O → Cl + O2
In above reaction Cl just acts as a catalyst and reappears. It is estimated that one Cl atom
can destroy 1,00,000 ozone molecule in one or two year

15. Ozone Hole

16. Chlorofluorocarbon (CFC)
CFC is a combination of carbon , hydrogen , fluorine and chlorine. CFC-11 and CFC-12
Are the most commonly used CFCs.
Use of CFC :
 Used as coolants in refrigerators and air conditioners.
 Propellants
 Cleaning solvents
 Stuffing of mattresses.
Ozone-depleting potential (ODP) is the ratio of the impact on ozone caused by a chemical
Compared to the impact of a similar mass of CFC-11. The ODP of CFC-11 is 1.0 .
Nitrous Oxide emitted by supersonic aircrafts , during combustion of
fossil fuel , by action of bacteria and use of nitrogen fertilizers and also breaks ozone
molecules.

17. Effects of Ozone Depletion
 UV radiation reaching the earth especially UV-B. It affect DNA
and photosynthetic chemicals. Any changes in mutation and
cancer. Cases of skin cancer which do not cause death but cause
disfigurement.
 Easy absorption of UV rays by the lens and cornea of eye will
result in increase in incidents of cataract.
 Melanin producing cells of the Epidermis (important for human
immune system) will be destroyed by UV-rays resulting in
immune-suppression.
 Phytoplanktons are sensitive to UV exposure. It’s result in
decrease in their population thereby affecting the population of
zooplankton , fish , marine animals , in fact the whole aquatic
food chain.
 Yield of vital crops like corn , rice , soyabean , cotton , bean , pea ,
sorghum and wheat will decrease.
 Degradation of paints , plastics and other polymer material will
result in economic loss due to effects of UV radiation.

18. Protection of Ozone layer
 Even after stopping the production of ozone layer
depletion chemicals , the model indicate that we still will
have to wait 50-100 years for the ozone layer to return to
1985 levels , and another 100-200 years for recovery . So
best method to reduce ozone depletion is substitution of
CFC with chemicals which have low ozone depleting
potential like HCFC , hydrocarbons , ammonia etc.

19. Green house effects
 A house of glass is used for raising delicate plants and in cold countries. This house is
called Green House
 A green house has higher temperature inside than outside which is due to
 Glass walls
 High carbon dioxide content and
 High water vapour content of the air in the green house.
 The natural green house effect is called as enhanced green house effect. While the
green house resulting from pollution is called enhanced green house effect.

21. Green house gases
1) Carbon Dioxide (CO2) : CO2 contribute about 55-60% to global warming from
green house gases produced by human activity.
2) Chlorofluoro carbon (CFC) : CFC contribute about 14-20% to global warming
from green house gases production by human activity.
3) Methane (CH4) : It contribute about 18-20% to global warming from green house
gases produced by human activity.
4) Nitrous oxide (N2O) : It is responsible for 6% of the human input of green house
gases.

22. Impacts of Global warming
 Global temperature increase : It is estimated that average temperature of
earth may increase by 1.40C to 5.80C .
 Rise in sea level :With increasing global temperature polar ice caps and glaciers
will melt. It will also cause terminal expansion of sea water resulting in further rise in
sea level
 Effect on human health: affecting the distribution of vector – Bone diseases
like malaria , filariasis , elephantiasis etc.
 Effect on food production : Global warming will reduce crop production due
to increased incidence of plant diseases and pests , explosive growths of weeds.
 Other climatic effects: Include unequal distribution of rain which may result in
flooding in some areas and drought in some areas. In temperate region , the summers
will be longer and hotter whereas the winter will be shorter and warmer.

24. Approaches to control Global Warming
1) Reduction in green house gas emission by reducing the use of fossil fuels and by
developing alternative renewable sources of energy like solar energy , wind energy etc.
2) Reduction in N2O emission by minimising the use of nitrogen fertilizers in agriculture.
3) Increase of the vegetation cover , particularity forest as it is sink for CO2 absorption.
4) Phasing out cholofluoro carbon and developing its substitution.
5) Traping and use of methane as fuel.
6) Stabilize population growth.
7) Using energy resources judiciously.

25. International steps for Mitigating
Global Change
a) Montreal Protocol: To limit the production and use of ozone depleting
substances . The participating countries agreed to freeze production of CFC at 1986
level and to reduce production by 50% by 1999 . In 1992 the phase out date for CFCs
and halon entirely was moved up to 1996. Helping the developing countries to
implement use of alternatives to CFCs.
b) Kyoto Protocol: An international conference held in Kyoto , Japan in December ,
1997 , has specified the commitments of different countries to mitigate climate change.
c) Earth summit: The United Nation conference on Environment and Development
(UNCED) , the Earth-summit , held at Rio de Janerio , Brazil in 1992 , established the
principles for reducing greenhouse gas emission.

26. Created By
Name
Jinesh Kamdar
Jasmin Makvana
Sagar Pandya
Kushal Gohel
Ishan Shah
En. No.
160210107024
160210107030
160210107036
160210107015
160210107046

27. Thank You
Government Engineering college , Bhavnagar