PlanPlan►What is ozone? What is ozone? ►Where is it found?Where is it found?►What is its origin? What is its origin? ►ImportanceImportance

►Ozone depletion Ozone depletion ►ImpactsImpacts►Solutions: protecting the ozone Solutions: protecting the ozone layerlayer

Ozone (OOzone (O33))

► A triatomic molecule, A triatomic molecule, consisting of 3 oxygen consisting of 3 oxygen atoms atoms

► Pale blue poisonous Pale blue poisonous gasgas

► Sharp, irritating odourSharp, irritating odour

► Low T Low T forms a liquid forms a liquid (-112 (-11200C) and a solid C) and a solid (-193 (-19300C)C)

Tropospheric ozoneTropospheric ozone

► In theIn the ground layer ground layer of the of the tropospheretroposphere ► 10%10% of ozone in earth’s atmosphere of ozone in earth’s atmosphere

► The two major sources of natural ground-The two major sources of natural ground-level ozone:level ozone:

1)1) hydrocarbonshydrocarbons,, which are released by plants and which are released by plants and soilsoil

2) small amounts of 2) small amounts of stratospheric ozonestratospheric ozone,, which which occasionally occasionally migratemigrate down to the earth's surface down to the earth's surface..

No threat to the health of humans or the environment.No threat to the health of humans or the environment.

But…But…

► OOzone iszone is also also a a byproduct of certain human byproduct of certain human activitiesactivities (automobiles, fossil fuel power (automobiles, fossil fuel power plants, certain industries, photocopying...)plants, certain industries, photocopying...) become becomess a a problem problem at ground levelat ground level

► 'bad''bad' ozone ozone ► Since 1900 the amount of ozone near the Since 1900 the amount of ozone near the

earth's surface has more than earth's surface has more than doubleddoubled..

-Pollutant-Pollutant-Constituent of smog-Constituent of smog

ImpactsImpacts

►Greenhouse gas Greenhouse gas contributes to contributes to global warmingglobal warming

►Pollution in the tropospherePollution in the troposphere► IIrritating, reactive moleculerritating, reactive moleculess

damagedamage forests and crops; forests and crops; destroy nylon, rubber, and other destroy nylon, rubber, and other

materialsmaterials;; injure or destroys living tissueinjure or destroys living tissue..

Ozone layerOzone layer

► a layer in Earth's atmosphere which contains a layer in Earth's atmosphere which contains relativelyrelatively high concentrations of ozone (O high concentrations of ozone (O33))

much higher than the concentrations in the lower much higher than the concentrations in the lower atmosphere but still small compared to the main atmosphere but still small compared to the main components of the atmosphere components of the atmosphere

If the ozone layer were brought down to the Earth's If the ozone layer were brought down to the Earth's surface, air pressure and temperature conditions surface, air pressure and temperature conditions would compress the ozone into a layer 2 to 5 mm would compress the ozone into a layer 2 to 5 mm thick!thick!

► Over 90% of ozone in earth'sOver 90% of ozone in earth's atmosphereatmosphere

► Absorbs Absorbs 97-99%97-99% of of the sun's ultraviolet the sun's ultraviolet lightlight

► LLocated in ocated in the lower the lower ppartart of the of the stratospherestratosphere

► FFrom rom 15km to 35km15km to 35km above Earth's above Earth's surfacesurface

Origin of Origin of OzoneOzone

► Ozone-Oxygen Ozone-Oxygen CycleCycle

- a continuing a continuing processprocess

► Photochemical Photochemical mechanismsmechanisms

► Researched by the Researched by the British physicist British physicist

Sidney ChapmanSidney Chapman

ImportanceImportance

► Like a good pair of sunglasses, the ozone Like a good pair of sunglasses, the ozone layer acts like a layer acts like a natural filternatural filter, blocking out , blocking out most of the sun's harmful UV (ultraviolet) most of the sun's harmful UV (ultraviolet) rays. rays.

► Without the ozone layer, more people would Without the ozone layer, more people would get get sunburnssunburns, , skin cancerskin cancer and and cataractscataracts. .

► Plants and animals would also be affectedPlants and animals would also be affected

(e.g. excess UV radiation damages the plants' ability to carry (e.g. excess UV radiation damages the plants' ability to carry

out photosynthesis).out photosynthesis). ► Our planet's own protective sunscreen.Our planet's own protective sunscreen.

Ozone layer DepletionOzone layer Depletion

► In recent years the thickness of this layer In recent years the thickness of this layer has been decreasing, leading in extreme has been decreasing, leading in extreme cases to holes in the layer, especially over cases to holes in the layer, especially over the polesthe poles

► The first ‘surprise’ – The first ‘surprise’ – 19851985 when researches when researches discovered that discovered that 50%50% of the ozone over of the ozone over Antarctica Antarctica was being destroyed in spring-was being destroyed in spring-summer when there was much sunlightsummer when there was much sunlight

Causes of Ozone depletionCauses of Ozone depletion► ““Although natural phenomena can cause temporary Although natural phenomena can cause temporary

ozone loss, chlorine and bromine released from ozone loss, chlorine and bromine released from man-made compounds such as man-made compounds such as CFCsCFCs are now are now accepted as the main cause of this depletion”accepted as the main cause of this depletion”

Drs. M. Molina and S. Rowland in 1974 Drs. M. Molina and S. Rowland in 1974

CFCs discovered in 1930s CFCs discovered in 1930s Cheap to makeCheap to make became popular as became popular as

coolants in coolants in air conditionersair conditionersCoolants in Coolants in refrigerators refrigerators Propellants in aerosolPropellants in aerosol spray cans spray cans

Impacts of Ozone depletionImpacts of Ozone depletion

►Ecological effectsEcological effects► Impact on the oceans Impact on the oceans ►Plankton- phytoplankton as well as = Plankton- phytoplankton as well as =

production of oxygenproduction of oxygen►Zooplankton are highly sensitive to UV Zooplankton are highly sensitive to UV

Original food source for all other Original food source for all other living organisms in the oceans.living organisms in the oceans.

Causes different types of Causes different types of skin cancerskin cancer

Impact on land Impact on land plants plants

Increased effects of air pollution Increased effects of air pollution

Damage to materials Damage to materials

SolutionsSolutions►International actionInternational action

The Vienna ConventionThe Vienna Convention, 1985, 20 , 1985, 20 nations nations

► Intentions to reduce the use of CFCs. Intentions to reduce the use of CFCs. ►Before clear evidenceBefore clear evidence

►1985 – the discovery of the Antarctic 1985 – the discovery of the Antarctic hole, enhanced scientific research hole, enhanced scientific research

The Montreal Protocol on Substances that The Montreal Protocol on Substances that Deplete the Ozone LayerDeplete the Ozone Layer – 1987 – 1987

Since 1987 over 180 nations have ratified Since 1987 over 180 nations have ratified a landmark environmental treaty.a landmark environmental treaty.

The Protocol’s chief aim is The Protocol’s chief aim is to reduce and to reduce and eventually eliminate the production and eventually eliminate the production and use of man-made ozone depleting use of man-made ozone depleting substances, or ODSsubstances, or ODS..

By agreeing to the terms of the Montreal By agreeing to the terms of the Montreal Protocol, the nations committed to take Protocol, the nations committed to take actions to protect the ozone layer, hoping actions to protect the ozone layer, hoping in the long-term to reverse the damage in the long-term to reverse the damage that had been done by the use of ozone that had been done by the use of ozone depleting substances.depleting substances.

Summary of Montreal Protocol Control Measures

Ozone Depleting Ozone Depleting SubstancesSubstances Developed CountriesDeveloped Countries Developing Developing

CountriesCountries

Chlorofluorocarbons (CFCs)Chlorofluorocarbons (CFCs) Phased out end of 1995Phased out end of 1995 aa Total phase out by Total phase out by 20102010

HalonsHalons Phased out end of 1993Phased out end of 1993 Total phase out by Total phase out by 20102010

Carbon tetrachlorideCarbon tetrachloride Phased out end of 1995Phased out end of 1995 aa Total phase out by Total phase out by 20102010

Methyl chloroformMethyl chloroform Phased out end of 1995Phased out end of 1995 aa Total phase out by Total phase out by 20152015

Hydrochlorofluorocarbons Hydrochlorofluorocarbons (HCFCs)(HCFCs)

Freeze from beginning of Freeze from beginning of 19961996 bb   

   35% reduction by 200435% reduction by 2004   

   65% reduction by 201065% reduction by 2010 Freeze in 2016Freeze in 2016

   90% reduction by 201590% reduction by 2015 at 2015 base levelat 2015 base level

  Total phase out by 2020Total phase out by 2020 cc Total phase out by Total phase out by

20402040

Hydrobromofluorocarbons Hydrobromofluorocarbons (HBFCs)(HBFCs)

Phased out end of 1995Phased out end of 1995 Phased out end of Phased out end of 19951995

Methyl bromideMethyl bromide Freeze in 1995 at 1991 base Freeze in 1995 at 1991 base levellevel dd

Freeze in 2002 at Freeze in 2002 at averageaverage

   25% reduction by 199925% reduction by 1999 1995-1998 base level1995-1998 base level

  50% reduction by 200150% reduction by 2001 20% reduction by 20% reduction by

20052005 ee

  70% reduction by 200070% reduction by 2000 Total phase out by Total phase out by

20152015

   Total phase out by 2005Total phase out by 2005   

►Use Use non-ozone depleting alternative non-ozone depleting alternative refrigerantsrefrigerants The major substitutesThe major substitutes

HydroHydrochlorochlorofluorocarbonsfluorocarbons (H (HCCFCs) FCs)

HydrofluorocarbonsHydrofluorocarbons (HFCs) (HFCs) ►RecyclRecycle refrigerantse refrigerants

►Raise awareness Raise awareness

►Even given immediate action, it will Even given immediate action, it will take take 50-100 years 50-100 years for the ozone layer for the ozone layer to return to to return to 1985 levels1985 levels. .

► It will take another It will take another 100-200 years100-200 years for for full recovery to full recovery to pre-1950 levels.pre-1950 levels.