Ozone Depletion Chandu

8/3/2019 Ozone Depletion Chandu

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OZONE LAYERDEPLETION1. Why the hole in the atmospheric ozonelayer above us?2. What has been done about this?3. Why should I worry ourselves about theOzone Layer Depletion?


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What is Ozone? Ozone Layer? Ozone (O3) is a highly-reactive from of oxygen. Unlike oxygen (O2), ozone has a strong scent

and is blue in color.

Ozone exists within both the tropospheric andstratospheric zones of the Earths atmosphere In the troposphere, ground level ozone is a major

air pollutant and primary constituent ofphotochemical smog

In the stratosphere, the ozone layer is anessential protector of life on earth as it absorbsharmful UV radiation before it reaches the earth.


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CFCs and ozone depletion Chlorofluorocarbons arecreated and used inrefrigerators and airconditioners. Thesechlorofluorocarbons are notharmful to humans and havebeen a benefit to us. Oncereleased into the atmosphere,

chlorofluorocarbons arebombarded and destroyed byultraviolet rays. In the processchlorine is released to destroythe ozone molecules


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Destruction of ozone by chlorine

Molecular oxygen is broken down in the stratosphere by solarradiation to yield atomic oxygen, which then combines withmolecular oxygen to produce ozone. The ozone is thendestroyed by chlorine atoms.


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Ozone destruction by UV rays UV radiation from the sunreleases the radicals Cl andClO. Ozone is a highly unstable

molecule so it readily donatesits extra oxygen molecule tofree radical species such ashydrogen, bromine, andchlorine.

These compound species actas catalysts in the breakdownof ozone molecules.


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The ozone depletion process


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Responsibility for ozone damageeach year


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Global CFC production


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Ozone hole in Southernhemisphere October 1979 & 1998

Monthly means of total ozone in the SouthernHemisphere observed with TOMS Images for October of 1979 (left) and 1998 (right).


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Ozone hole: size by month


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Ozone hole measurements over theAntarctic region 1980-98


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Ozone concentration at the centerof ozone hole


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Ozone hole over continents:comparison 1996


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Image of the ozone hole over theSouth pole: July 10 2003


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Image of the ozone hole over theNorth pole: July 10 2003


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Ozone status: full day global image, July9th 2003


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Effects of UV rays on AquaticEcosystemsOzone depletion causes increases in UVrayss effects on aquatic ecosystems by:

1.decreasing the abundance of phytoplankton affects the food stock for fishes and theabsorption of CO22. decreasing the diversity of aquatic organisms reduces food stock and also destroys severalfish and amphibians.


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Effects of UV rays on TerrestrialEcosystems Damage to plant cell DNA molecules - makes

plants more susceptible to pathogens and

pests

Reductions in photosynthetic capacity in the

plant - results in slower growth andsmaller leaves

Causes mutations in mammalian cellsand destroys membranes


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Harmful effects of UV rays onpeople Skin cancer

Premature aging (photoaging) of the

skin (different from normalchronological aging)

Cataracts and eye disorders (corneal

sunburn and blindness) Immune system damage


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Correlation between Ozonedepletion and skin diseases


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The Ultraviolet ExposureIndexINDEX VALUES EXPOSURE

0 2 = Minimal3 - 4 = Low5 - 6 = Moderate7 - 9 = High10 + = Very High


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Factors affecting UV exposure Clouds cover - partly cloudy days do

little to reduce UV exposure but rainy orsubstantially overcast days reduce UV

exposures

The time of day peak exposure time

is 12:00 noon - 1:00 p.m. UV intensityis reduced by about half at three hoursbefore and three hours after the peakexposure time.


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Factors affecting UV exposure..2 The time of year- more UV is

received in the late spring and earlysummer and much less is received in

the late fall and early winter.

Life styledetermines a personsrisk to UV exposure. Skiing,

sunbathing, or swimming can lead toextremely high exposures. Use oftanning parlors also increase risk.


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Policy responses to Ozone depletion

Mario Molina and Sherwood Rowlandshowed in 1974 that CFC gases destroy ozone

Coordinating committee on Ozone Layer(CCOL) established by UNEP in the 1970s

Vienna Convention for the protection of theozone layer held in 1985

Montreal Protocolto ban substances that

deplete the ozone layer held in 1987 Amendments to the Montreal Protocol:

London - 1990, Copenhagen - 1992 andMontreal - 1997.

Ozone Depletion Chandu

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