62984281 case study on ozone layer

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ANTRACTICA OZONELAYER

GUDIED BY:-Mrs.Reena singh

Presented by:-Group-III(E.C.E.)


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COMPILED BY:-

VIKASH KUMAR(419/08)

ANKUR GOYAL(420/08)

SUMAN SANYA(421/08)

ABHISHEK SINGH(422/08) MOKSH KUMAR SINGH(423/08)

PRAKASH PRATIK(424/08)

ANSHU AYUSHYA(425/08) ALOK KUMAR(426/08)

RAVI KUMAR JYOTI(427/08)


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INDEX

1.WHAT IS OZONE?

2.WHERE IS THE OZONE?

3.ISNT OZONE BAD NEWS?

4.WHY IS A OZONE HOLE A PROBLEM?


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5.HOW DOES A OZONE HOLE FORM

OVER ANTRACTICA?

6.WHAT CAUSES THE OZONE

DEPLITION?

7.IS THE OZONE HOLE GOING TO

STAY OVER ANTRACTICA?

8.CAN THE OZONE HOLE RECOVER?


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What is ozone?

Ozone is a gas* made of oxygenatoms.

Usually oxygen atoms hang around

in pairs - this is the sort of oxygenthat we breathe and that helpsthings to burn.

Oxygen sometimes however willform a molecule with three oxygenatoms, this is what we call ozone:


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O2 - two oxygen atoms - ordinary commonor garden oxygen

O3 - three oxygen atoms

Ozone

Ozone has a the particularly usefulcharacteristic that it can absorb largequantities of ultra-violet (uv) light - moreof that soon.


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Where is the ozone?

Most of the ozone on earth isn't on earthat all, but in the layer of the earth'satmosphere called the stratosphere.

This is the upper layer of the atmosphereand starts between 12.9 to 19.3 km (8 to12 miles) above our heads and goesupwards to almost 50 km (30 miles).

The stratosphere has virtually no cloudsor other form of weather, it's thinnest atthe equator and thickest at the poles.


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Ozone is formed in the stratosphereby the action of sunlight on oxygen

molecules. In particular it is the high energy ultra-violet light

in sunlight that is effective, it causes an oxygenmolecule to split into two oxygen atoms:

O2 ---------> O + O


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One of these then joins with anotheroxygen molecule to form a molecule ofozone:

O + O2 ---------> O3 Ozone may also be destroyed by joining

with a lone oxygen atom to get back tooxygen again.

Ultra-violet light is required for ozone

to form in the stratosphere, but thenthe ozone absorbs the ultra-violetlight so stopping it reaching deeperinto the earth's atmosphere.


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The result is that levels of ozoneare greatest at around 20km up.

This is good news for us as it stopslots of ultra-violet light gettingthrough to us and also keeps theozone high up in the atmosphere out

of the way.


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Isnt ozone bad news?

Ironically, at ground level ozoneis very bad news. It is a majorcomponent of photochemical

smog. It is caused by the effect of ultra-

violet light on nitrogen oxide fromvehicle exhausts and so particularlyaffects built up areas in regions ofhigh sunshine.


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Ozone affects lung function, it canaggravate asthma and other chronicrespiratory tract and lung diseases andcan reduce lung function in the short termor even permanently on repeatedexposure.

Ozone has an effect like sunburn on thelining of the respiratory tract damagingthe cells


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Ozone in the stratosphere is nicelyout of the way and has the wonderfulbenefit to life on earth that it

specifically absorbs the harmful ultra-violet light from the sun while letting

other light wavelengths through.


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If there is a hole in the ozone layer then this means thatmore harmful ultra-violet rays get through than are goodfor us or many other life forms, plant or animal. Too muchultra-violet light can result in:

Skin cancer Eye damage such as cataracts Immune system damage Reduction in phytoplankton in the oceans that forms the

basis of all marine foodchains including those in Antarctica. Damage to the DNA in various life-forms So far this has

been as observed in Antarctic ice-fish that lack pigments to

shield them from the ultra-violet light (they've neverneeded them before)


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Why does a ozone hole form over

antractica?

The ozone hole is caused by the effectof pollutants in the atmospheredestroying stratospheric ozone.

During the Antarctic winter somethingspecial happens to the Antarctic weather:-

1. strong winds blowing around thecontinent form, this is known as the

"polar vortex" - this isolates the air overAntarctica from the rest of the world.


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2.Secondly, special clouds formcalled Polar StratosphericClouds. Clouds don't normally form

in the stratosphere and these turnout to have the effect ofconcentrating the pollutants that

break down the ozone, so speedingthe process up


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By the time spring arrives and the sun comesback after the long polar night, the ozone levelsare severely depleted around the Antarcticcontinent causing the "ozone hole".

Unfortunately, there then follows a particularlylong period of high sunshine and long days, justto make the effect of the ozone hole worse.

The concentration of ozone in theatmosphere is measured in "Dobson Units",

the average concentration of ozone in theatmosphere is about 300 Dobson Units. Theozone hole is considered to be wherever theconcentration drops below 220 Dobson Units.


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The following pictures areprovided courtesy of NASA.

They show the extent of ozone

thinning. Dark blue and purple colors

correspond to the thinnest ozone,

while light blue, green, and yellowpixels indicate progressively thickerozone.


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October 1999 (average)Historically, the Antarctic ozone hole

was largest during October. In recentyears however, September has beenthe peak month.


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September 7th 2000

The ozone hole grew quicker than usual and exceptionally large.By the first week in September the hole was the largest ever atthat time. For the first time it reached towards South America andto regions of high population.


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September 2006 averageFrom September 21 to 30, 2006, the average

area of the ozone hole was the largest everobserved, at 10.6 million square miles. A littleover a week later, instruments recorded thelowest concentrations of ozone ever observed

over Antarctica, making the ozone hole the


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What causes the ozone depletion?

Ozone is mainly broken down by chemicalscalled ChloroFluoroCarbons CFC's and alsoby nitrogen oxides.

CFC's ironically were first used in large

quantities because they were thought tobe safe and inert (unreactive) chemicals.

They are a group of chemically similargases used in refrigeration systems, air

conditioners, aerosols, solvents and in theproduction of some types of packaging. Nitrogen oxides are a by-product of fuel

burning, e.g. aircraft exhausts.


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CFSS donot occur naturally, they are man-made chemicals. They are very useful when they are where they are

supposed to be, and doing what they are supposed to bedoing.

But once released into the atmosphere they are a seriouspollutant.

The problem is it took us many years to realise this duringwhich we thought they were perfectly harmless, but in factwere building up to levels that will take decades for them todisappear again even if we stop producing them altogether.

The actual reactions that destroy ozone are verycomplicated.

They take place on the surface of the ice particles of thePolar Stratospheric Clouds and it takes only a smallamount of CFC to destroy an awful lot of ozone.


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Is the ozone hole going to stay over

Antractica? Since the annual thinning of the ozone

layer over Antarctica was first discovered,measurements have been carried out in allregions.

Ozone depletion has been measuredeverywhere in the world except in thetropics.

Depletion is usually worse the further from

the equator and recently an Ozone hole(as defined by a distinct area of very lowozone levels) has been detected above theNorth Pole in the arctic.


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There is a lot to learn about thebreakdown of ozone in the atmosphere.Warmer region, non polar depletion ofozone in particular is not properlyunderstood.

So for the time being the "ozone hole"seems to be an Antarctic phenomena, buta less severe thinning of the ozone layer ispretty much a world-wide thing.

How acute and important it will be in thefuture is not known.


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Can the ozone hole recover?

The way to stop the formation, growth andspread of ozone thinning is to reduce theproduction of those chemicals that causethe destruction of ozone, namely CFC's andnitrogen oxides.

In 1987, the Montreal Protocol was signed bymany nations whereby those nations that signedagreed to reduce their emissions of CFC's to ahalf (of the 1987 levels) by 2000.

Potential problems come from nations that do not

see the reduction of CFC's to be a priority, andalso from the huge quantity of refrigeration andair conditioning systems in the world that stillcontain CFC's.


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If they are not disposed of correctly, thenthe CFC's will escape into the atmosphereand continue to destroy ozone.

The problem is far from settled and isunder investigation by research teams allover the world. The latest estimates arethat as long as production and release of

CFC's is regulated properly, global ozonelevels should recover by 2050.


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Latest ozone news:-

17th September 2005

"The 2005 hole is larger and deeper than the holes thatformed when the discovery was made but the situationwould be much worse if the Montreal Protocol had not comeinto force. This agreement shows us that global action bygovernments to stop the release of ozone depleting

chemicals really can help society to successfully mitigate aglobal environmental problem. We are still experiencinglarge losses of Antarctic ozone each spring because CFCsand other chemicals live for a long time in our atmosphere.However, the ban ensures that we will see an improvementin the future. We now need to take similar actions tocontrol greenhouse gasses, otherwise we will bequeathfuture generations a significantly different climate from thatof today."-Jonathan Shanklin

( one of the original discoverers of the ozone hole)


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Covering an area of around 22 millionsquare kilometres this year's hole is a littlesmaller than the record-breaking event inAugust 2003.

Measurements made during August andSeptember at BAS Halley and RotheraResearch Stations reveal a 50% reductionon normal ozone levels over the base ofthe Antarctic Peninsula and the WeddellSea, and a 20% reduction over the tip ofSouth America and the Falkland Islands.

.


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The increased ultra violet lightreaching the surface poses a medicalhazard to people living under the

?hole' and without suitable protectionpeople face the prospect of rapidsunburn and potentially more serious

skin damage


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62984281 case study on ozone layer

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