OZONE LAYERIT’S DEPLETION AND IT’S EFFECT

BY: GROUP 4 (Roll. No.- 31 to 40)

The envelope of air or different types of gases surrounding the earth is known as atmosphere .There are five distinct layers of atmosphere , they are as follows:-

1) TROPOSPHERE:-This is the lowest atmospheric layer and is about 7miles(11km)thick ,the

troposphere is thinner at the poles and thicker at the equator . Thetemperature decreases with altitude.

2) STRATOSPHERE:-Above the troposphere is the stratosphere which extends to about 30-35 miles

about the Earth’s surface. The temperature rises within the stratosphere butstill remains well below freezing.

3) MESOSPHERE:-The Mesosphere is above the stratosphere , here the temperature is very

rarefield , that is , thin , and the temperature is decreasing with altitude , about -130 Fahrenheit at the top.

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4) THERMOSPHERE:-The thermosphere rises several hundred miles above the earth’s surface. The

temperature is quite hot and can rise to as high as 3,600 degree Fahreneit.

5) EXOSPHERE:-Extending from the top of the thermosphere to 6200 miles (10000 km) above the

earth is the exosphere . This layer has very low atmospheric molecules which canescape into space.

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OZONE LAYER The ozone layer or ozone shield refers to

a region of Earth's stratosphere that absorbs most of the Sun's ultraviolet (UV) radiation.

The ozone layer was discovered in 1913by the French physicists Charles Fabryand Henri Buisson.

It contains high concentrations of ozone (O3) relative to other parts of the atmosphere, although still very small relative to other gases in the stratosphere.

The ozone layer contains less than 10 parts per million of ozone, while the average ozone concentration in Earth's atmosphere as a whole is only about 0.3 parts per million.

The ozone layer is mainly found in the lower portion of the stratosphere, from approximately 20 to 30 kilometres (12 to 19 mi) above Earth, though the thickness varies seasonally and geographically.

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The majority of tropospheric ozone formation occurs when nitrogen oxides (NOx), carbon monoxide (CO) and volatile organic compounds (VOCs), react in the atmosphere in the presence of sunlight. NOx, CO, and VOCs are called ozone precursors.

In the stratosphere, ozone is produced by a two-step chemical process.

*"ULTRA VIOLET" means "beyond violet". Violet being the colour of

the highest frequencies of visible light. Uv radiation was discovered

in 1801 when the German physicist " JOHANN WILHELM RITTER "

observed that invisible rays just beyond the violet end of the visible

spectrum darkened silver chloride.

*Ultraviolet (UV) light is an electro magnetic radiation with a wavelength from 400nm to 100nm, shorter than that of visible light but longer than X-rays. Uvradiation is present in sunlight,and is produced by electric arcs. ultraviolet radiations can cause chemical reactions and causes many substances to glow or flouresce consequently. Suntan, freckling and sunburn are familiar effects of over exposure along with higher risk of skin cancerabout 10% of sunlight is

UV and only about one- third of this penetrates the atmosphere to

reach the ground.Of this the solar UV energy that reaches the equator,

95% is UVA and 5% is UVB. No measurable UVC from solar radiation

reaches the earths surface, because ozone, molecular oxygen and water

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Destruction of the upper atmospheric layer of ozone gas, caused by substances

formed from breakdown of ozone depleting substances is called ozone depletion.

Ozone is a triatomic form of oxygen (O3), found in the Earth's atmosphere. A

combination of low temperatures, elevated chlorine and bromine concentrations in the

upper stratosphere are responsible for the destruction of ozone. The production and

emission of chlorofluorocarbons (CFCs), is the leading cause of ozone layer depletion.

CFC's accounts for almost 80% of the total depletion of ozone.

Other ozone-depleting substances (ODS), include hydrochlorofluorocarbons (HCFCs),

and volatile organic compounds (VOCs). These are often found in vehicle emissions,

byproducts of industrial processes, refrigerants, and aerosols. ODS are relatively

stable in the lower atmosphere of the Earth, but in the stratosphere, they are exposed

to ultraviolet radiation and thus, they break down to release a free chlorine atom.

This free chlorine atom reacts with an ozone molecule (O3), and forms chlorine

monoxide (ClO), and a molecule of oxygen. Now, ClO reacts with an ozone molecule to

form a chlorine atom, and two molecules of oxygen. The free chlorine molecule again

reacts with ozone to form chlorine monoxide. The process continues, and this results

in the depletion of the ozone layer.

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Ozonaction Programme

UNEP OzonAction assists developing countries countries with economies in transition to achieve and sustain their compliance with the Montreal Protocol on Substances that Deplete the Ozone Layer and make informed decisions on alternative technologies and ozone friendly policies.

UNEP OzonAction has implemented over 1000 projects and services that have benefitted to more than 100 developing countries. The main objective is to the Montreal Protocol whose annual per capita consumption and production of ozone depleting substance is less than 0.3 kg to comply with the control measures of the protocol.

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• OzonAction is a branch of the United Nations Programme (UNEP) which has its main office in Paris and is part of UNEP Division of Technology, Industry and Economics created in 1991.

The ozone-oxygen cycle is the process by which ozone is continually regenerated in the Earth's stratosphere, all the while converting ultraviolet radiation (UV) into heat. In 1930 Sydney Chapman resolved the chemistry involved. The process is

commonly called the Chapman cycle by

atmospheric scientists.

Most of the ozone production occurs in the tropical upper stratosphere and mesosphere. The total mass of ozone produced per day over the globe is about 400 million metric tons. The global mass of ozone is relatively constant at about 3 billion metric tons, meaning the Sun produces about 12% of the ozone layer each day

OZONE CYCLE 40

Ozone Cycle40

5 Ways to Protect Depletion of OZONE

Limit private vehicle driving: by reducing the driving of vehicular emission

Use eco-friendly houseold cleaning products: by using eco-friendly and natural products which does not harm the environment.

Avoid using pesticides: the best solution for this would be to try using natural remidies,rather than heading out for pesticides.

Developing stringent regulations for rocket launches: now –a-days no. of rocket launches are pretty hgh which results in ozone depletion.Thus no. of launches should be reduced or safe gases should be used for combustion.

Banning the use of dangerous ‘nitrous oxide: nations around the globe came together and formed ‘Montreal Protocol’ in the year 1989 with the strong aim of stop usage of CFCs.

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