Ozone layer Depletion

TheAtmosphere•  Thisisourprotectiveblanketofgasses.

– 78%Nitrogen(N2)– 21%Oxygen(O2)– Proportionallysmallamountsofcarbondioxide,watervaporandothertracesubstances

AtmosphericGases

TheAtmosphere-Layers•  Troposphere–  Layerinwhichwelive– Mostweatheroccurshere

•  Cloudsformherecontributingtothealbedoeffect

–  90%ofthegassesarehere–  78%nitrogen,21%oxygen–  Temperaturedecreaseswithaltitudeuntilthenextlayerisreached

•  Stratosphere–  6-31milesinaltitude–  Calm–  Airtrafficduetolackofweather

–  Temperatureincreaseswithaltitude

–  Ozonelayer(oxygenisconvertedtoO3bylightningand/orsunlight)

–  99%ofultravioletradiation(especiallyUV-B)isabsorbedbythestratosphere

TheAtmosphere-Layers

OzoneLayer•  Presentinthestratosphere•  AbsorbsUVradiation(99%)•  Comprisedofahighconcentrationof03molecules.– Oxygenexistsin3formsintheatmosphere:O3,O2,andO.

– OzoneisbeingcontinuouslyformedanddecomposedduetotheenergyfromUVrays.O3+UVàO2+OàO3

Ozone•  OzoneisO3•  Naturallyoccurringinthestratosphere.•  TheabsorptionofenergyfromUVrayscausestheformationanddeformationofO3.

•  Withoutanthropogenicinputsthesystemisinequilibrium

O3O2+O

OzoneStratosphericOzone•  Naturallyoccurring.•  BeneficialtolifeonEarth

•  Createsaprotectivelayerthatabsorbs99%ofUVradiationinsunlight

TroposphericOzone•  Alsocalledground-levelozone

•  Anthropogenic•  DoesNOTmigratetotheatmosphere

•  SecondaryAirpollutant•  Respiratoryirritant,eyeirritant,damagesplants

DestructionofAtmosphericOzone

•  ThegroupofmoleculesthatareinthiscategoryareoftenreferredtoasODS(OzoneDepletingSubstances)

•  Anthropogenicsources:– CFCs– Halocarbons/Halons

•  Usedinfireretardants•  Foam-blowinginsulation

•  1chlorinecandestroy100,000ozonemolecules

CFCs•  Chlorofluorocarbon•  TrademarknameisFreon•  CFCshavestablestructureswhichallowthemtomigratethroughthetroposphere

•  TheyarebrokendownwhenexposedtostrongUVradiation

•  Usedin–  Refridgerants–  Propellants/aerosols– Gasblownplastics(Styrofoam)–  Pesticides–  Flameretardants

CCl3F+UVàCl+CCl2F

Cl+O3àClO+O2

ClO+0àCl+O2

Repeatedmanytimes

SummaryofCFCReactions

VideoofOzoneDepletion

•  https://www.youtube.com/watch?v=V7eDjqJ7vsY

Thinningozone

EffectsofThinningOzoneLayer

EnvironmentalEffects•  GreaterUVradiation

damagesphotosyntheticorganisms(especiallyphytoplankton)decreasingprimaryproductivity

•  Sunburnsanimals•  Cataracts/blindnessin

animals

HumanHealthEffects•  Sunburn/skincancer•  Cataracts(eyedamage)•  Wrinkles•  Decreasedimmune

response

PollutionManagement

•  Recyclingrefrigerants•  Findingalternativestogas-blownplastics,halogenatedpesticides,propellantsandaerosols

•  Developingnon-propellantalternatives

MontrealProtocol•  Internationaltreatytoprotecttheozonelayerbyphasingoutmaterialsbelievedtocausethedepletionofstratosphericozone

•  HasbeenVERYsuccessful.Ozonelayerisshowingsignsofrecovery

•  BansCFCsandhalons•  Includesseveralgroupsofsubstances,allofthemincludingchlorineorbromine.