The document discusses the ozone layer, its formation and location in the stratosphere. It protects life on Earth by absorbing UV radiation. Ozone is formed through chemical reactions involving oxygen and UV radiation. Depletion of the ozone layer is caused by catalytic cycles involving halogen gases like chlorine and bromine, which destroy ozone molecules. This increased UV radiation reaching the Earth's surface and can harm humans, animals, and ecosystems. Global warming is caused by increased greenhouse gases trapping heat, but is a separate issue from ozone depletion.
4. Introduction to ozone layer
What is Ozone?
• Unstable, poisonous, allotrope of oxygen.
• Forms layer.
• Process of Photolysis
Ozone layer:-
– Upper atmosphere.
– Works as a protective shield.
– High level ozone.
6. CONT..
Properties of ozone layer:-
– Pale blue gas.
– Absorbs UV rays.
– O3.
– Mol.weight: 48.
– Diamagnetic.
– Oxidizing agent.
– Insoluble in water and soluble in inert polar solvents.
7. CONT..
Location of ozone layer:-
– Stratosphere the upper region.
– Troposphere the lower region.
Abundance of ozone layer:-
– Oxygen(O2) and Nitrogen(N2).
– Stratosphere: 1 billion molecules = 1 million
molecules.
– Troposphere: 100 molecules =1 million
molecules.
9. Distribution of ozone layer over globe:
• Sum of al the ozone layer in the atmosphere
• Varies with location on timescale ranging from
daily to seasonal.
10. Units used for ozone measurement:
• Dobson unit
• Ozone pioneer G.M.B dobson (1920s to 1970s)
• 1mm thickness = 1DU
11. Ultraviolet radiations:
• That portion of the electromagnetic spectrum
between x-rays and visible light.
• Source of vitamin D
• Not seen or felt
• Health effects of too much UV radiations.
16. Stratosphere
It protect life on earth
In 1920 it was first observed
It is formed naturally by chemical reaction
It involve;
i. Oxygen
ii. UV radiation
17. stratosphere
oxygen molecules makes up 21% of the atmosphere
Two oxygen molecules are involve in formation of
stratospheric ozone
The stratospheric ozone is formed in two steps
18. Step 1
Oxygen molecule breaks into two molecules of o2
UV radiations are involve in this breaking
o2
oo
19. Step 2
Each of these
highly reactive atoms combines with an oxygen
molecules
These reaction occurs continually
o o2 o3
20. CONT..
As a result largest ozone production occurs
Its is balanced by destruction in chemical reaction
In each reaction an ozone molecule is lost
Its is considered as “good ozone”
21.
22. troposphere
Near to earth surface
Ozone is produced by chemical reaction
Primarily involve hydrocarbons and nitrogen
oxides
All reactions are completed in the presence of
sunlight
it is considered as “bad ozone”
It is destroyed by naturally occurs reaction and
by human produce chemical reaction
23. UV radiations
Portion of the electromagnetic spectrum between X-
rays and visible lights
Scientists classify UV radiation into three types
i. UVA
ii. UVB
iii. UVC
24. Ozone depletion
Destruction of upper atmospheric layers of ozone
Which protect earth form UV radiation
and thinning of ozone
26. Effects on human and animal health
Increased penetration of UV-B radiation
have adverse
effects
Cause many diseases like
Eye diseases
Skin cancer
Infection diseases
Experiments on animal prove UV radiation
effects immune system
27. Effects on terrestrial plants
• Physiological and developmental process of plants
• Thought of scientist
• UV-B cause mutation in plants
• Affects plant community
28. Effects on aquatic ecosystem
• Phytoplankton forms food web
• Phytoplankton have the limited productivity in
euphotic zone
• Many phytoplankton are capable of active
movement that enhance their productivity and
survival
• UV-b radiation effects motility and survival rate of
phytoplankton
29. Effects on air quality
• Reduction in stratospheric ozone
• Cause destruction of ozone and related oxidants such
as hydrogen peroxide
• Air quality required for normal environment is
destroyed
30. Effects on bio-geo-chemical cycle
• Affect terrestrial and aquatic bio geo chemical
cycle
I. Changes the production and decomposition of
plant matter
II. Reduction of primary production changes in
the uptake and release of atmospheric gases
III. Reduction of bacterioplankton growth in the
upper ocean etc.
• Nitrogen cycle is also affected by UV radiation
31. Effects on ultraviolet radiation
• Depletion of ozone layer leads the uv radiation to
reach on earth
• Largest decrease in ozone have been observed over
Antarctica
32. CATALYTIC DISTRUCTION OF STRATOSPHERIC
OZONE
Destroyed by reactions
Halogen gases
Most reactive gases
Three reaction cycles
33. Cycle 1
Made up of two basic reactions
1. Cl +o3
2. Clo +o2
Result
Chlorine act as a catalyst
Break the catalytic cycle
34. Cycle 2 and 3
Polar
Clo increase
Cycle 2,3 become dominant
Reactions of cycle 2
Clo +clo (clo2)2
(clo2)2+sunlight cloo+cl
Cloo cl+o2
Result
36. Global warming and ozone depletion
Ozone hole
Not mechanism of global warming
Global warming
Chlorofluorocarbon
Down the capacity
37. Catalytic destruction of stratospheric
ozone
The most reactive gases are
chlorine(clo),bromine(bro)
Three principal reaction cycles that
destroy ozone
Cycle one
Cl+o3 and clo+o2
Convert one ozone and one oxygen atom
into two oxygen molecules
38. Polar cycle 2 and 3
Cycle 2,3 become dominant reaction
mechanism for polar ozone less because
of the high abundance of clo and low
abundance of o2
cycle 2 begins with the reaction of clo and
3 with reaction of clo with bro
Destroy two ozone molecules and create
three oxygen molecules
These reactions occur naturally in
stratosphere
39. Global warming and ozone depletion
A gradual increase in the overall
temperature of the earth’s atmosphere
generally attributed to the green house
effect caused by increased level of co2 and
other pollutants
These gases spread around the planet like
blanket ,capturing the solar heat that
would otherwise be radiated out into
space