Current Global
Environmental Issues
Syllabus
• Current Environmental Global Issues:
Global Warming & Green Houses Effects,
Acid Rain , Depletion of Ozone Layer
Important Questions
• Explain Green House Effect. What are various sources of green house
gases.
• How depletion of Ozone layer does takes place in the atmosphere? Explain
the ill effect of Ozone Depletion.
• Define Acid Rain. How does it form and what are its ill effects?
• Enlist Global Environmental Pollution Problems. Describe one in detail
and suggest remedial measures to reduce them.
• What is Ozone? How is it formed? Describe the main causes of depletion
of Ozone layer and briefly comment over control measures taken to prevent
further ozone depletion at international level.
• Explain the Green House Effect with the help of schematic diagram and
compare the effect of different green house gases in global warming.
• Write short notes on (i) Acid Rain (ii) Environmental Degradation
• Enlist global environmental problems and discuss any one.
• Write explanatory notes
• Ozone layer Depletion
• Acid Rains
Green House Effect
• The Increase in CO2 content of the
environment has been responsible for gradual
heating up the globe, by a process called as
green house effect. The progressive warming
up of the earth’s surface due to blanketing
effect of manmade CO2 in the atmosphere is
known as green house effect.
Green House Effect
• From sun 3 types of radiations are emitted,
ultraviolet rays(< 400 nm), Visible rays ( 400 –
700 nm) and Infrared rays (700 – 1000 nm), of
this the visible rays are having maximum
intensity i.e. (400 nm to 700nm wavelength).
Approx 47 % of the solar radiation is absorbed by
water and land surfaces and the remaining rays
are radiated back to the atmosphere in the form of
Infrared rays (700 nm – 1000 nm). Water vapor
and CO2 molecules in atmosphere near earth’s
surface absorb the infrared radiations (heat rays)
emitted by earth. Thus the net effect causes
warming of atmosphere. This effect is called a
green house effect.
Principle of Green House Effect
• The transparent walls and roofs of the green house are such that
they allow visible sunlight to enter but prevents the entry of long
wavelength Infrared radiations to go out.
• Thus the sunlight is absorbed by soil and structure of the green
house. It is then re-emitted as heat rays which cannot pass
through the glass. The amount of energy in the green house thus
increases the warmth of the atmosphere. In similar ways the
earth’s atmosphere bottles up the energy of the sun like green
house. Here CO2 and water vapor acts like glass windows.
• CO2 and water vapor in the atmosphere transmits short
wavelength solar radiations but reflect longer wavelength heat
radiations from warm surfaces of the earth. CO2 molecules are
transparent to sunlight but not to heat radiations, so they trap and
re-enforce the solar heat like a green house
Green House
Green House Gases
•
•
•
•
•
Carbon dioxide ( CO2)
Methane ( CH4)
Nitrous oxide ( N2O)
Chlorofluorocarbon (CFC)
Ozone
Sources of Green House Gasses
• 1) Burning of Coal, Oil, Natural Gas in the
factories.
• 2) Burning of fossil fuels at power stations
• 3) Use of Petrol and Diesel from automobiles,
railways, aircrafts etc.
• 4) Burning of firewood and deforestation
• 5) Tree and plants release carbon as CO2.
• 6)Fire in the forests contribute to the release of
CO2
Effects of Warming up of Air
• Increase in temperature on earth’s surface will
cause more evaporation of surface water.
• Melting of Glaciers (ice mountains)
• Rise in Sea Level will wash away entire
countries from Bombay to Boston.
• Shifting of climate zones will occur.
CO2, CH4, N2O, CFC’s, O3, H2O
Vapor
Control
• Reduce the consumption of fossil fuels
• Use anti pollution devices
• Non conventional energy sources should be
developed as a alternate to fossil fuel.
• Prevent deforestation
• Planting more trees.
Acid Rain
• Acid
Rain
is
a
environmental
Problem
caused due to rapid
industrialization. Acid rain
has become invisible threat
to rivers, lakes and forests.
• Acid rain means presence
of acids in rainwater. The
basic component of acid
rain are nitric acid, and
sulphuric acid.
Causes of Acid Rain
• Acid Rain is because of human activities.
Sulphuric acid is formed when (SO2) is
discharged from combustion process converts
to sulphurtrioxide (SO3) which reacts with the
water vapor present in the atmosphere to form
sulphuric acid (H2SO4).
– The oxides of sulphur and nitrogen are produced
by combination of fossil fuels, smelters, power
plant, automobile exhausts, domestic fire.
Acid Rain Formation
Effects of Acid Rain
• The acid rain damages the leaves of plants and trees
and retard the growth of forest.
• Wash out the nutrients from the soil.
• Significant reduction of fish population and decease in
aquatic micro organisms.
• Damage to Buildings and structural materials.
• Corrosion of houses, monuments, statues and bridges.
• The human nervous system, respiratory system and
digestive system may get affected
• Acid rain reduces the rate of photosynthesis and hence
growth of plants.
Control
• Liming of Lakes
• Tough laws to reduce acid forming pollutants,
being released in atmosphere.
Ozone Layer Depletion
• Ozone layer depletion is mainly
due to Chloro-floro carbons
(CFC). Ozone layer prevents the
harmful ultraviolet rays from
entering in the atmosphere but
(CFC) is one of the main ozone
eaters and it allows the
penetration of harmful ultraviolet
rays.
Chloro-floro
carbon
remains in the atmosphere for
decades and reacts with the
atmospheric
chlorine
to
accelerate the long chain
reaction. This chain reaction
slowly eats away the oxygen
atom which could be used in the
formation of ozone.
© NOAA
• Thus it leads to decrease in Ozone
concentration which results in reaching of
ultraviolet rays to earth surface due to which
heat increases to uncomfortable levels and the
temperature of earth increases.
Main Ozone Layer Depletors
• CFC (Chloro Floro Carbon) The Chlorofloro
carbon are less costly, non toxic, and safe to
handle material is used in propellants, cleaning
solvents, plastic foams, in dry cleaning
industries, for sterilizing surgical instruments.
Because of wide use of CFC the CFC in the
atmosphere is increased and which has caused
irreparable damage to our environment.
• Oxides of Nitrogen:- Burning of Fossil fuels
and increase in use of nitrogen as a fertilizer
are also contributing in destruction of ozone
layer.
• Thus in addition to CFC, the oxides of
nitrogen also plays an important role in
depletion of Ozone.
Mechanism of Ozone Depletion
• The chlorofloro carbons are highly stable and
hence they slowly diffuse in the atmosphere.
The ultraviolet rays decompose the CFCs and
thus free chlorine and fluorine radicals are
released In the atmosphere. This chlorine
radical released in the atmosphere converts O3
into O2
• Similarly oxides of Nitrogen also depletes the
ozone
• CFCl3
UV rays
• Cl + O3
UV rays
• ClO + O
UV rays
CFCL2 + Cl
ClO + O2
Cl + O2
• Similarly UV rays
• NOx + O3
NO2 + O2
Oxygen in the
+
O2
Atmosphere
UV
radiation
O
+
O
O
+
O2
O3 (ozone)
+
O3
(ozone)
+O3
(ozone)
UV
O
O
+
O2
O
+
O2
O2
O3
+
O2
+
(ozone)
heat
Cl- “Free Radicals”…
Cl-
+
O3
(ozone)
“free radical”
+
ClO
O
+
ClO
O2
+
Cl“free radical”
O2
Effects of Ozone Depletion
• The damage to ozone layer will result in
damage to plants and animals
• For every 2.5 cm increase in the size of ozone
hole, there will be 5 – 6 % increase in skin
cancer and cataracts.
• Ultraviolet
rays
may
interfere
with
photosynthesis leading to lower crop yield
• Ultraviolet rays causes genetic changes in
DNA, leading to lower crop yield.
Control.
• Discourage use of CFCs and NOx
• Better alternative for CFC should
developed.
• Reforestation and forest prevention.
be
28.0 million km2 on 25 September 2006
© NASA
Maximum ozone hole area for 2009
was 24 million km2 on 17 September.
The Dobson unit (DU) is a unit of measurement of atmospheric ozone columnar density,
specifically ozone in the stratospheric ozone layer. One Dobson unit refers to a layer of
ozone that would be 10 µm (micrometre)
March 2012
Activity
• Enlist and Explain the significance of various
treaties and conference held around the world to
curb
the
hazardous
effects
of
various
Environmental Issues.
Assignment
• Explain the phenomenon of Heat Island Effect.
• Thanks