ozone layer

1. Indira Priyadarshini Govt Degree
College (w) Nampally Hyderabad
 WORLD OZONE DAY
 PPT PRESENTATION ON THE TOPIC:
 ATMOSPHERE WITH STRESS ON OZONE LAYER.
 SUBJECT:BOTANY
 LECTURERS: Rajitha mam & Anitha mam

2. WORLD OZONE DAY

3. WORLD OZONE DAY
 World Ozone Day, also known as the International Day for the
Preservation of the Ozone Layer, is observed annually on September
16 to bring attention to the ozone layer and the dangers of ozone
depletion.
 The purpose of the day is to raise awareness about the importance of
preserving the ozone layer.
 Similarly, it shifts the focus on developing more effective methods for
the same.
 Many studies have shown that the ozone layer’s damage will persist
for another five to ten years after it has already been done.
 This has the potential to make things much more difficult for them in
the days ahead.

4. History of World Ozone Day
 In 1994, the UN General Assembly declared
September 16 to be the annual International Day
to Preserve the Ozone Layer.
 The governments of 46 countries across the globe
signed the “Montreal Protocol on Substances that
Deplete the Ozone Layer” in 1987, and this was
done to celebrate that event.
 The “Montreal Protocol” was another name for it.

5. Theme of World Ozone Day 2022
 ‘Global Cooperation to Protect Life on Earth’ .
 It has been chosen as this year’s theme in order to
encourage sustainable development.
 Montreal Protocol@35: worldwide collaboration
safeguarding life on earth is the topic for this year’s
World Ozone Day.
 The theme not only supports long-term growth but
also acknowledges the wider effects of the Montreal
Accord.

6. Significance
 Because the ozone layer absorbs most of the sun’s UV radiation,
this day is significant because it reduces the amount of radiation
that reaches people.
 The ozone layer is crucial because radiation is a known cause of
cancer, cataracts, and other health problems.
 Reports, however, imply that the ozone layer thickness in the
northern hemisphere has decreased by 4% every year.
 Man-made chlorofluorocarbons are among the most major ozone
layer killers.

7. TOPIC
Atmosphere with stress on
ozone (o3 layer) .

8. What is atmosphere?
 Atmosphere is a layer of gas or layers of gases that
envelope a planet, and is held in place by the gravity of
the planetary body.
 Atmosphere is layer of mixture of gases that surround the
earth or a planet. It is colourless, odourless, and tasteless
mixture of gases that extends up to a height of about 1600
km. Though 99% of total mass of the atmosphere is within
40 km from the earth. Atmosphere makes the earth
habitable, without it life is impossible on the earth.

9. STRUCTURE OF ATMOSPHERE
 Depending on vertical temperature, atmosphere is grouped into
five major layers as described below:
1. Troposphere
2. Stratosphere
3. Mesosphere
4. Thermosphere
5. Exosphere
 Earth’s atmosphere is composed of about 78% nitrogen, 21%
oxygen, and one percent other gases which are found in these
above mentioned five layers.

11. The five layers of the atmosphere
1. Troposphere: It is the lower layer lies above the earth up to the height of 8-
18 km. It contains 85% of the total mass of atmosphere and is the densest
part. All weather characteristics like rain, cloud, fog, dew, mist etc. Occur in
this layer. The temperature decreases with increase in altitude in this layer.
2. Stratosphere: It is just above the troposphere and lies beyond the height of
8-18 km extending up to 50 km depending on latitude. The ozone layer found
in this strata, absorbs most of the sun’s ultraviolet rays (very harmful to us)
which heat up the stratosphere. The stratosphere is a very stable layer, and
not much weather occurs in it. For this reason, most planes fly in the lower
part of the stratosphere. It contains only 15% of the atmosphere mass and all
photo chemical reactions occur here in this layer. Temperature increases with
increase in altitude up to 50 km. This is the warmest layer.

12. 3.Mesosphere: This layer is lies above stratosphere and characterized by strong
decrease in temperature with increase in altitude up to 80 km, then warms up again
in next layer i.e. Thermosphere.
4.Thermosphere: It is uppermost layer lies above mesosphere and characterized by
steadily increase in temperature with altitude. Ionosphere is just lower strata of
thermosphere and due to this layer long distance radio communication is possible.
5.The Exosphere:The region above about 500 km is called the exosphere. It contains
mainly oxygen and hydrogen atoms, but there are so few of them that they rarely
collide – they follow “ballistic” trajectories under the influence of gravity, and some
of them escape right out into space.

14. 8277486

15. What is an Ozone Layer?
 The ozone layer is mainly found in the lower portion of the earth’s
atmosphere. It has the potential to absorb around 97-99% of the harmful
ultraviolet radiations coming from the sun that can damage life on earth. If
the ozone layer was absent, millions of people would develop skin diseases
and may have weakened immune systems.
 However, scientists have discovered a hole in the ozone layer over Antarctica.
This has focussed their concern on various environmental issues and steps to
control them. The main reasons for the ozone hole are chlorofluorocarbons,
carbon tetrachloride, methyl bromide and hydrochlorofluorocarbons.
 Let us have a detailed look at the various causes and effects of ozone layer
depletion.

16. What is Ozone Layer Depletion?
 Ozone layer depletion is the thinning of the ozone layer present in the upper atmosphere.
This happens when the chlorine and bromine atoms in the atmosphere come in contact with
ozone and destroy the ozone molecules. One chlorine can destroy 100,000 molecules of
ozone. It is destroyed more quickly than it is created.
 Some compounds release chlorine and bromine on exposure to high ultraviolet light, which
then contributes to ozone layer depletion. Such compounds are known as Ozone Depleting
Substances (ODS).
 The ozone-depleting substances that contain chlorine include chlorofluorocarbon, carbon
tetrachloride, hydrochlorofluorocarbons, and methyl chloroform. Whereas, the ozone-
depleting substances that contain bromine are halons, methyl bromide, and hydro
bromofluorocarbons.
 Chlorofluorocarbons are the most abundant ozone-depleting substance. It is only when the
chlorine atom reacts with some other molecule, it does not react with ozone.
 Montreal Protocol was proposed in 1987 to stop the use, production and import of ozone-
depleting substances and minimise their concentration in the atmosphere to protect the
ozone layer of the earth.

20. Causes of Ozone Layer Depletion
 Ozone layer depletion is a major concern and is associated with a number of
factors. The main causes responsible for the depletion of the ozone layer are
listed below:
 Chlorofluorocarbons
 Chlorofluorocarbons or CFCs are the main cause of ozone layer depletion. These
are released by solvents, spray aerosols, refrigerators, air-conditioners, etc.
 The molecules of chlorofluorocarbons in the stratosphere are broken down by
ultraviolet radiations and release chlorine atoms. These atoms react with ozone
and destroy it.
 Unregulated Rocket Launches
 Researches say that the unregulated launching of rockets results in much more
depletion of the ozone layer than the CFCs do. If not controlled, this might result
in a huge loss of the ozone layer by the year 2050.
 Nitrogenous Compounds
 The nitrogenous compounds such as NO2, NO, N2O are highly responsible for the
depletion of the ozone layer.

21.  Natural Causes
 The ozone layer has been found to be
depleted by certain natural processes
such as Sun-spots and stratospheric
winds. But it does not cause more than 1-
2% of the ozone layer depletion.
 The volcanic eruptions are also
responsible for the depletion of the
ozone layer.
 Ozone Depleting Substances (ODS)
 “Ozone-depleting substances are the
substances such as chlorofluorocarbons,
halons, carbon tetrachloride,
hydrofluorocarbons, etc. That are
responsible for the depletion of the
ozone layer.”

22.  Effects of ozone layer depletion:
 The depletion of the ozone layer has harmful effects on the
environment. Let us see the major effects of ozone layer depletion
on man and environment.
 Effects on Human Health
 Humans will be directly exposed to the harmful ultraviolet radiation
of the sun due to the depletion of the ozone layer. This might result
in serious health issues among humans, such as skin diseases, cancer,
sunburns, cataract, quick ageing and weak immune system.
 Effects on Animals
 Direct exposure to ultraviolet radiations leads to skin and eye cancer
in animals.
 Effects on the Environment
 Strong ultraviolet rays may lead to minimal growth, flowering and
photosynthesis in plants. The forests also have to bear the harmful
effects of the ultraviolet rays.
 Effects on Marine Life
 Planktons are greatly affected by the exposure to harmful ultraviolet
rays. These are higher in the aquatic food chain. If the planktons are
destroyed, the organisms present in the food chain are also affected.

24.  Solutions to Ozone Layer Depletion
 The depletion of the ozone layer is a serious issue and various programmes have been launched by
the government of various countries to prevent it. However, steps should be taken at the individual
level as well to prevent the depletion of the ozone layer.
 Following are some points that would help in preventing this problem at a global level:
 Avoid Using ODS
 Reduce the use of ozone depleting substances. E.g. Avoid the use of CFCs in refrigerators and air
conditioners, replacing the halon based fire extinguishers, etc.
 Minimise the Use of Vehicles
 The vehicles emit a large amount of greenhouse gases that lead to global warming as well as ozone
depletion. Therefore, the use of vehicles should be minimised as much as possible.
 Use Eco-friendly Cleaning Products
 Most of the cleaning products have chlorine and bromine releasing chemicals that find a way into
the atmosphere and affect the ozone layer. These should be substituted with natural products to
protect the environment.
 Use of Nitrous Oxide should be Prohibited
 The government should take actions and prohibit the use of harmful nitrous oxide that is adversely
affecting the ozone layer. People should be made aware of the harmful effects of nitrous oxide and
the products emitting the gas so that its use is minimised at the individual level as well.

26.  Ozone is a molecule composed of three oxygen atoms and it is present in a
gaseous form in the atmosphere, specifically located in and extended
throughout the stratosphere.
 Did you know that the ozone layer is essential for life to exist?
 Its molecules act as a shield protecting us from solar radiation. When the
radiation reaches the ozone layer, it passes through the ozone molecules and
these are responsible for returning part of radiation back to space, in this way
the radiation that reaches us is minimized.
 What is the hole in the ozone layer?
 It is a hole that allows the entry of large amounts of ultraviolent light and it is
located at the poles, on the Antarctic continent and the Arctic Ocean, being
especially large during the spring of both hemispheres and resulting in longer
summer seasons.

27.  Why is the hole in the ozone layer harmful?
 Although this hole is due to the natural fluctuations of ozone in the atmosphere, it also caused
by human activities which emit gases that end up in the stratosphere and degrade the ozone
molecules, increasing the size and effect of this hole in the ozone layer. This is an
environmental and health problem, since the excess of solar radiation is a threat to any form
of life.
 How can we protect the ozone layer?
 Avoid the consumption of gases dangerous to the ozone layer, due to their content or
manufacturing process. Some of the most dangerous gases are CFCs (chlorofluorocarbons),
halogenated hydrocarbon, methyl bromide and nitrous oxide.
 Minimize the use of cars. The best transport option is urban, bicycle, or walking. If you use a
car to a destination, try to carpool with others to decrease the use of cars in order to pollute
less and save.
 Do not use cleaning products that are harmful to the environment and to us. Many cleaning
products contain solvents and substances corrosive, but you can replace these dangerous
substances with non-toxic products such as vinegar or bicarbonate.
 Buy local products. In this way, you not only get fresh products but you avoid consuming food
that has traveled long distances. As the more distance traveled, the more nitrous oxide is
produced due to the medium used to transport that product.
 Maintain air conditioners, as their malfunctions cause CFC to escape into the atmosphere.

29. Thank you
 Made by: T. Ramyasri
V. Yamuna
L. Meenakshi
M. Ramyasri
 Bse life science students 2nd year 2022-23
 Botany subject.