環(huán)境化學(xué)課件

AtmosphericStructureTheatmosphereTheatmosphereisathinblanketofgasthatenvelopstheearth.Thegasesthatmakeuptheatmosphereareheldclosetotheearthbythepullofgravity.Withincreasingdistancefromtheearth’ssurface,thetemperature,density,andcompositionoftheatmospheregraduallychangeOnthebasisofairtemperature,theatmospherecanbedividedverticallyintofourmajorlayers.AtmosphericstructureTroposphereThetroposphereisthelayerfromtheearth’ssurfacetothetropopause,whichisat10-15kmaltitudedependingonlatitudeandtimeofyear.(Mt.Everest8.85km)Asaltitudeincreases,airtemperaturedecreasesatarateofabout3.5oper1000ft.Thetropopausehasatemperatureofabout–57oC.Thelowerpartofthetroposphereinteractsdirectlywiththesurfaceoftheearth–thispartofthetroposphereisgenerallycalledair.Theatmosphereinthislayerisheatedfrombelowbyconvectionandradiationfromtheearth’ssurface.Mostofourweatheroccursinthetroposphere.StratosphereThestratosphereisthelayerabovethetroposphereandextendstoabout50km.Thetemperatureriseswithincreasingaltitude,reachingamaximumofabout–1oCatthestratopause.Theozonelayerisinthestratosphere.OzoneabsorbsUV,causingtherisingtemperaturewithaltitudeinthislayer.Thetemperaturestructurekeepstheaircalminthislayer.(That’swhyjetaircraftflyinthelowerstratosphere!)MesosphereThemesosphereextendsfromthetopofstratopauseto~80km.Inthemesosphere,thetemperaturedecreaseswithaltitude.ThermosphereThelayerofairabovemesosphereiscalledthermosphere.Inthethermosphere,temperatureriseswithaltitude,causedbyabsorptionofUVsolarradiationbyN2andO2.TheloweratmosphereThetroposphereandthestratospheretogetherarecalledtheloweratmosphere.Theloweratmosphereaccountfor99.9%oftotalatmosphericmassTheloweratmosphereisthedomainofmaininterestfromanenvironmentalperspective.Ozonedepletion(stratosphere)Airpollution(troposphere)IonosphereIonosphereisaregionwhereionsandelectronsaremostabundant.Thisregionislocatedataltitudeabove60km,thereforeliewithinthemesosphereandabove.Ionosphere

IonosphereactsasaconductinglayerintheupperatmospherethatwouldallowatransmittedelectromagneticsignaltobereflectedbacktowardtheEarth.Ionosphere:Northernlight(1)Ionosphere:Northernlight(2)EnergeticeventsontheSuncanturnthesolarwindintoanintensesolar"gale”whichinjectslargenumbersofenergeticparticlesintheEarth'smagnetosphere.Ionosphere:Northernlight(3)Thechargedparticlestravelalongthefieldlineswithsomuchenergythattheypenetratetheionosphere,wheretheyhitgasatomsandmolecules.Thesecollisionsgiveoffenergythatweseeascoloredlight.atmosphericpressure

TheatmosphericpressureistheweightexertedbytheoverheadatmosphereonaunitareaofsurfaceABhvacuumMercurybarometerMassoftheatmosphere

Ps:theglobalmeanpressureatthesurface,Ps=9.84x104Pa. R=6400km,theearthradius g=9.8m2/s,accelerationofgravityResults:ma=5.2x1018kgPressureprofileBarometriclawWhere Ma:themolecularweightofair g:accelerationofgravity R:gasconstant T:temperature z:altitudeWhatfractionoftotalatmosphericmassisinthetroposphere?

ThetropospherecontainsalloftheatmosphericmassexceptforthefractionP(tropopause)/P(surface)thatlieabovethetropopause.P(tropopause)=100hPaP(surface)=1000hPaResult:Ftrop=0.90UnitsforpressureInternationalSystemofUnits:Pascal(N/m2)Hectopascal(hPa)mmHgorTorrMillibar(mbar)psi(lb/in2)1atm=1.01325x105Pascal(Pa)=1.01325x103hPa1atm=760mmHg=760Torr1atm=1013.25mbar1atm=14.7psiAtmosphericCompositionCompositionoftheatmosphereGas%byvolumeN278.08O220.95Ar0.93CO20.03Allothergases(Ne,He,Kr,H,etc)0.01WaterVariableDryairWatervaporintheairThe%volumeofWatervaporisvariable,dependingontemperature,precipitation,rateofevaporationandotherfactorsataparticularlocation.Thepercentageofwatervaporrangesfrom0.1-5%.Generallyitis1-3%(the3rdmostabundantconstituentsintheair).ExpressingtheamountofsubstancesintheatmosphereConcentrationtheamount(mass,moles,molecules,etc)ofasubstanceinagivenvolumedividedbythatvolume.Theexampleconcentrationunitsaremg/m3,mol/m3,molecules/cc,andetc.Mixingratiotheratiooftheamountofthesubstanceinagivenvolumetothetotalamountofallconstituentsinthatvolume.

MixingRationiisthemolarconcentrationofiandntotalisthetotalmolarconcentrationofair.partspermillion(ppm) 10-6

mmolmol-1partsperbillion(ppb) 10-9 nmolmol-1partspertrillion(ppt) 10-12 pmolmol-1Conversionbetweenppmandmg/m3ni:mol/m3mi:mg/m3Mi:g/molPressureunitandRConstant:P=1.01325x10^5pascalR=8.314J/k.molforPinPaandvolumeinm3Conversionbetweenppmandmg/m3Example:

TheHongKongAirQualityObjectiveforozoneis240mg/m3.TheU.S.NationalAmbientAirQualityStandardforozoneis120ppb.Whichstandardisstricteratthesametemperature(25oC)andthepressure(1atm)?Typicalmixingratiosforsomecompoundsofenvironmentalimportanceppminsolutionvs.ppmasmixingratioforairbornesubstancesppm:PartspermillionsolutionairRelativeHumidityDefinition:ratioofthepartialpressureofwatertoitssaturationvaporpressureatthesametemperature.y:molefractionofwatervaporattemperatureTys:molefractionofsaturationwatervaporatTemperatureTRelativeHumidityCalculationofH2OmixingratioinppmfromRH

=pexp[13.3185a-1.976a2-0.6445a3-0.1299a4]wherep=1atmanda=1-(373.15/T).HongKongAirQualityObjectives(HKAQO)μg/m3AirPollution–InorganicGaseousPollutantsMajorinorganicgaseouspollutantsCarbonmonoxide(CO)Sulfurdioxide(SO2)NitrogenOxide(NO,NO2)NOx=NO+NO2Ozone(O3)HK1-hourAirQualityObjectivesforvariousairpollutantsAirPollutantsAQObjectives(mg/m3)AQObjectives(ppm)USAQStandards(ppm)Carbonmonoxide3000026.235Sulfurdioxide26.20.3060.50aNitrogendioxide350.1590.05bOzone8000.1220.12a:3-hrstandard,b:annualarithmeticmeanCarbonmonoxide:Healtheffect

COentersthebloodstreamandbindspreferentiallytohemoglobin,therebyreplacingoxygen.FeO2COFeFeC-OO-O320timesstrongerthanhemoglobin-O2bindingCarbonmonoxide:sourcesandsinksSourcesIncompletecombustion(internalengine)BiomassburningMethaneoxidationOxidationofnon-methanehydrocarbonDecayofplantmatterSinkReactionwithOHradical .OH+COCO2+H. H.+O2+MHO2.+MRemovalbysoilmicroorganismSuchasautomobilesCOformationfrommethaneoxidationCOemissionsourcesinHongKongCarbonmonoxide:AtmosphericchemistryCO+OH+O2

CO2+HO2.HO2.+NO

NO2+OHNO2+hv

NO+OO+O2+M

O3+MNet:CO+2O2+hv

CO2+O3ThenetreactioncanbeviewedasacatalyticoxidationofCOtoCO2.NetformationofO3occurs.Carbonmonoxide:controlstrategiesontheautomobilesourceEmployaleanerair/fuelmixture(higherair/fuelratio)EmploycatalyticexhaustreactorsExcessairispumpedintotheexhaustpipe.Air-exhaustmixturepassthroughacatalyticconvertertooxidizeCOtoCO2.AdditionofoxygenatestogasolineExamplesofoxygenates:methanol,ethanol,MTBESulfurdioxide:HealtheffectProduceirritationandincreasingresistanceintherespiratorytract.MucussecretionInsensitiveindividuals,thelungfunctionchangesmaybeaccompaniedbyperceptiblesymptomssuchaswheezing,shortnessofbreath,andcoughing.mayalsoleadtoincreasedmortality,especiallyifelevatedlevelsofsuspendedparticlesarealsopresent.Sulfurdioxide:SourcesandsinksSourcesCombustionofS-containingfuelinelectricpowerplants,vehicles.S(organicS+FeS2pyrite)+O2-->SO2OxidationofH2S:2H2S+3O2-->2SO2+2H2OH2SisproducedasanendproductoftheanaerobicdecompositionofS-containingcompoundsbymicroorganisms.OxidationofDMSSinkConvertedintosulphuricacidineithergasorliquidphaseSO2emissionsourcesinHongKongFormationofsulfuricacidandsulfatefromSO2Ingas-phaseSO2+.OH+MHOSO2.+MHOSO2.+O2HO2.+SO3SO3+H2O+MH2SO4+M

Inaqueousphase,dissolvedSO2isoxidizedtosulfatebyO3 (dominantpathwaywhenpH>5)H2O2 (dominantpathwaywhenpH<5)organicperoxidesO2catalyzedbyironandmanganeseSulfateformation:2NH3+H2SO4(NH4)2SO4Sulfurdioxide:ControlstrategiesRemovalofSbeforeDURINGburning.

Fludizedbedcombustion:Coalisburnedwithlimestone(CaCO3)(finelypulverized)ordolomite(Ca-Mgcarbonate)orboth. CaCO3-->CaO+CO2, CaO+SO2-->CaSO3. CaSO3isremovedfromthestackbyanelectrostaticprecipitator.removalofSfromsmokestacksbeforeenteringtheatmosphere.

Flue-gasdesulfurization:SO2iswashedfromthechimney(flue)gasesbyabsorptioninanalkalinesolution.

Sulfurdioxide:Controlstrategies(Continued)3.Dilution InstallationoftallstacksreducesSO2levelsintheimmediateneighborhoodbydispersingthemmorewidely

Nitrogenoxides:HealthEffectsNOCellularinflammationatveryhighconcentrations.Maybeincorporatedintohemoglobininthebloodtointerferewiththetransportofoxygenaroundthebody.NO2irritatethelungslowerresistancetorespiratoryinfectionsuchasinfluenza.Nitrogenoxides:SourcesandsinksSourcesFuelcombustioninpowerplantsandautomobiles.N2+O2-->NO2NO+O2-->2NO2Naturalsources:electricalstorms;bacterialdecompositionofnitrogen-containingorganicmatter

NOxemissionsourcesinHongKongNitrogenoxides:AtmosphericchemistryInterconversionofNOandNO2NO2+hv

NO+O (1)O+O2+M

O3+M (2)NO+O3

NO2+O2 (3)NO2+hv

NO+O (1)O+O2+M

O3+M (2)HO2.+NO

NO2+OH (4)RO2.+NO

NO2+RO. (5)NonetO3formationO3isformedNitrogenoxides:AtmosphericchemistryFormationofnitricacidGas-phasereactionNO2+OH

HNO3

daytime(dominatepathway)HeterogeneousreactionNO2+O3

NO3+O2NO3+NO2?N2O5 N2O5+H2O(aq)

2HNO3(aq)

MinorpathwayOnlyoperativeduringnighttimeNitrogenoxides:AtmosphericchemistryFormationofnitrateHNO3+NH3NH4NO3HNO3+NaCl(s)NaNO3+HClNitrogenoxides:Controlstrategies1.Lowerthecombustiontemperatureofthefurnaceinelectricpowerplants2.Installcatalyticconverters:catalyticconvertersinautomobilescanremove76%

ofNOxfromtailpipes.Two-stagecombustiontoreducebothNOxandVOCsFirststage:combustioncondition—richinfuelSecondstage:combustioncondition—richinairThree-waycatalyticconverterforautomobileexhaust(RemoveCO,NOandHC)HC+H2O=H2+CO2NO+2H2=N2+2H2O2CO+O2=2CO2HC+2O2=CO2+2H2OCatalyst:RhodiumCatalyst:RhodiumCatalyst:Platium/palladiumNOxcontrolinpowerplantsAmmoniumreductionofNO4NH3+6NO=5N2+6H2OUreareductionofNO2CO(NH2)2+6NO=5N2+2CO2+4H2OAirPollution-TroposphericOzoneGoodOzoneandBadOzoneStratosphericozoneprotectlivesonEarthfromharmfuleffectsofUVradiation.Troposphericozone:CausingrespiratorydistressandeyeirritationDestroyingplantsProducingcracksinrubberOzoneisastrongoxidant,reactswithmoleculescontainingC=Cdoublebonds,formingepoxides.Twotypesofairpollutants:primaryvs.secondaryPrimarypollutants:releaseddirectlyfromsourcesExamples:CO,SO2,NOxSecondarypollutants:formedthroughchemicalreactionsoftheprimarypollutantsandtheconstituentsoftheunpollutedatmosphereintheair.Example:O3FormationofozoneNO2+hv

NO+O (1)O+O2+M

O3+M (2)NO+O3

NO2+O2 (3)NO2+hv

NO+O (1)O+O2+M

O3+M (2)HO2.+NO

NO2+OH (4)RO2.+NO

NO2+RO. (5)NonetO3formationO3isformedNetof(1)+(2)+(4):RO2.+O2O3+RO.

NO2iscapableofabsorbingvisiblelight(<400nm)toproduceO.SourcesofRO2.:OxidationofhydrocarbonsRH+OHR.+H2OR.+O2RO2.AsingleorganicradicalcanproducemanyperoxyradicalsbysuccessiveroundsofO2combinationandfragmentation.Example:OxidationofcarbonmonoxideCO+.OH+O2

CO2+HO2.HO2.+NO

NO2+.OHNO2+hv

NO+OO+O2+M

O3+MNet:CO+2O2+hv

CO2+O3ThenetreactioncanbeviewedasacatalyticoxidationofCOtoCO2.NetformationofO3occurs.Example:OxidationofmethaneCH4+.OH+O2

CH3OO.+H2OCH3OO.+NO

CH3O.+NO2CH3O.+O2

HCHO+HO2.HO2.+NO

.OH+NO2NO2+hn

NO+O(2x)O+O2+M

O3+M(2x)Net:CH4+4O2

HCHO+H2O+2O3Thenetreactionisthatforeachmoleofmethaneoxidized,2molesofO3isproduced.NecessaryingredientsforozoneformationSunlightNOx(NO,NO2)Hydrocarbons(VOCs:volatileorganiccarbon)VOCs+NOx+hn

O3+otherpollutantsProductionofOatomProductionofRO2,whichreactswithNOsothatO3couldaccumulate.NecessaryingredientsforozoneformationCH4+.OH+O2

CH3OO.+H2OCH3OO.+NO

CH3O.+NO2CH3O.+O2

HCHO+HO2.HO2.+NO

.OH+NO2NO2+hn

NO+O(2x)O+O2+M

O3+M(2x)Net:CH4+4O2

HCHO+H2O+2O3VOCSunlightFormationofoxidantsotherthanO3Formationofaldehydes(e.g.formaldehyde)FormationofPAN(peroxyacetylnitrate)anditsanalogsROO.+NO2ROONO2(peroxyalkylnitrate)PANPhotochemicalsmogSmogderivesfromacombinationofthewordssmokeandfog.LondonsmogandLosAngelessmogLondonsmogischaracterizedbyhighSO2andparticleconcentrationinthepresenceoffog.AlsoreferredassulfuroussmogLosAngelessmogischaracterizedbyhighoxidants(mainlyO3).ItwasfirstrecognizedintheLosAngelesarea.Thetermsmogismisleadinginthiscase,assmokeandfogarenotkeycomponents.Theappropriatetermisphotochemicalairpollution.PhotochemicalairpollutionHO2.Radical:Interconversionof.OHandHO2.

OHandHO2areinterconvertedthroughaseriesofreactionsinvolvinghydrocarbonsandoxidesofnitrogen.

HO2.+NO

.OH+NO2.OH+RCH3

H2O+RCH2.RCH2.+O2

RCH2OO.RCH2OO.+NO

NO2+RCH2O.RCH2O.+O2

RCHO+HO2.SourcesofOHareineffectsourcesofHO2.undermosttroposphericconditions.Sourcesfor.OHradicals:PhotolysisofO3

PhotolysisofO3formsO1D,followedbyitsreactionwithwater.O3+hn

O1D+O2

l<320nmO1D+H2O

2.OH

Sourcesfor.OHradicals:PhotolysisofHONOHONO+hn

.OH+NOl<400nm

PossiblesourcesforHONOincludeNO2+H2OOH+NONO+NO2+H2OHO2+NO2reaction(possiblyacontributionfromaminorchannelofthisreaction)directemissions,forexample,fromautomobiles.

Sourcesfor.OHradicals:PhotolysisofH2O2H2O2+hn

2.OHl￡360nmH2O2isformedfromthereaction: HO2.+HO2.

H2O2+O2

SourcesforHO2.Radicals:formaldehyde

FormaldehydephotolysisisamajorsourceofHO2.duringthedaylighthours.HCHO+hn

H.+HCO.

l<370nmH.+O2+M

HO2.+MHCO.+O2

HO2.+CONote:AnyprocessthatproducesHCO.orH.isasourceofHO2.inthetroposphere.

Nighttimesourcesfor.OH/HO2.OzoneoxidationofalkenespeciesEthene+O30.12OHIsoprene+O30.27OHThermaldecompositionofPeroxyactylnitrate(PAN)anditsanalogsofhighercarbon.CH3C(O)OONO2?CH3C(O)OO.+NO2CH3C(O)OO.+NO

CH3C(O)O.+NO2CH3C(O)O.

CH3.+CO2CH3.+O2

CH3OO.CH3OO.+NO

CH3O.+NO2CH3O.+O2

HCHO+HO2.Nighttimesourcesfor.OH/HO2.(Continued)NO3reactionwithhydrocarbonsNO3+RH

HNO3+R.R.+O2

ROO.ROO.+NO

RO.+NO2RO.+O2HO2.+R’CHO

Varioussourcesof.OH/HO2.asafunctionofthetimeofdayControlstrategiesforozoneO3isasecondarypollutantcontrolofO3requirescontrolofitsprecursors.ControlofVOCsGeneraltooabundanttobebroughtlowenoughtobethelimitingfactor.Incertainareas,VOCsfrombiologicalsourcescouldbesignificant.ControlofNOxDifficulttocontrolasefficientenergyconversionrequireshighcombustiontemperature.AirPollution-ParticlesintheAirAirqualityandparticlesEpidemiological(流行病學(xué))evidenceassociatesatmosphericparticleswithdiseasesandmortality.Particlespenetratethelungs,blockingandirritatingairpassages.Particlesthemselvescouldexerttoxiceffects.(toxicsubstancespresentintheparticles)[PolycyclicAromaticHydrocarbonsareexamplesoftoxicsubstancesinaerosols.]Particledepositionasafunctionofparticlediametersinvariousregionsofthelung.Thelargeraparticleis,themorelikelyitisdepositedintotheupperpartoftherespiratorysystem.Thesmalleraparticleis,thedeeperitcangetintotherespiratorysystem.TermsTSP:TotalsuspendedparticulatematterRSP:RespirablesuspendedparticulatematterPM10:Particulatematteroflessthan10um;equivalenttoRSP.PM2.5:Particulatematteroflessthan2.5umAirqualitystandardsforparticlesUS15ug/m3(annualaverage)forPM2.5um65ug/m3(dailyaverage)forPM2.5umHongKongRSP:55ug/m3(annual),180ug/m3(daily)TSP:80ug/m3(annual),260ug/m3(daily)VisibilityandAerosolsInaclearskywithoutanyparticles,onecanseeasfaras100-300km.PhysicsofvisibilityVisibilitydependsonthetransmissionoflightthroughtheatmosphereandtheabilityoftheeyetodistinguishanobjectbecauseitcontrastswiththebackground.Achangeincontrastwithviewingdistanceoccursforbothdark,lightandbrightobjects.Withdarkobjects,theatmosphereintroduceslight,called"airlight",tothesightpath,andthedarkobjectappearslighteratincreasingdistanceuntilitbleedsintothebackgroundatthehorizon.Withlightobjects,lightislostfromthesightpathwithincreasingviewingdistance.Inbothcases,theresultisthesame—Thecontrastbetweentheobjectandthebackgroundapproacheszerowhenthelightcomingalongthelineofsightfromtheobjectapproachestheintensityofthelightfromthebackgroundatthehorizon.Whentheeyecannolongerdistinguishthedifference,thecontrast,betweentheobjectandthebackground,theobjectcannotbeseen,anditissaidtobebeyondthelimitofvisibility.Themathematicexpressionfortheextinctionofcontrast:

I=Ioexp[-bx]b:scatteringcoefficientorabsorptioncoefficient,x:distanceI:lightintensityorcontrast.b=bsg+bsp+bag+bapbsgandbspareextinctioncoeff.causedbylightscatteringduetogasandparticlesrespectively.bsp=bsdp+bswarebrokenintocontributionsduetodryparticlesandwaterassociatedwithparticles.bagandbapareextinctioncoeff.causedbylightabsorptionduetogasandparticlesrespectively.Visibilityreductionduetoparticlesissize-dependent

ParticleScatteringandabsorptioncross-sectionperunitvolumeParticlesof0.1-1.0umsizeareefficientlight-scatteringcenters.Fineaerosolparticlesareamajorcontributortovisibilityimpairment

(BlueRidgeMountainareaintheU.S.)

Category%bextScatteringduetogases5.0Scatteringduetodryparticles49.1Scatteringduetoparticleboundwater43.1Absorptionduetogases0.3Absorptionduetoparticles2.5MeasurementofvisibilityHumanobservationsOpticalmeasurementsMeasuredbyaintegratingnephelometerVisualrangeStudyquestionsHowdoparticlescauseadverseeffectonhumanhealth?Howdoparticlesaffectvisibility?ParticlesandCloudsCloudalbedoforcing:CoolingTheshortwaveraysfromtheSunarescatteredinacloud;manyoftheraysreturntospace.Theresulting"cloudalbedoforcing”,takenbyitself,tendstocauseacoolingoftheEarth.CloudGreenhouseForcing:WarmingLongwaveradiationWhenacloudabsorbslongwaveradiationemittedbytheEarth'ssurface,thecloudre-emitsaportionoftheenergytospaceandaportionbacktowardthesurface.Thisprocessiscalled"cloudgreenhouseforcing"and,takenbyitself,tendstocauseaheatingor"positiveforcing"oftheEarth'sclimate.OveralleffectofallcloudsCloudalbedoforcingcoolingCloudgreenhouseforcingwarmingTheoveralleffectofallcloudstogetheristhattheEarth'ssurfaceiscoolerthanitwouldbeiftheatmospherehadnocloudsThedominatefactorintheglobalalbedoisclouds.Aerosol:DefinitionAerosolisasuspensionofsolidorliquidparticlesinagas.Atmosphericaerosolsconsistofsmallparticlesofliquidandsolidmaterialsuspendedintheair.Bioaerosol:Anaerosolofbiologicalorigin.(Examples:viruses,bacteria,fungi,spores,andpollens.)Aerosolsizesareusuallymeasuredintheunitofmicrometer(mm)1mm=10–6m1mm=104angstrom(?)TypicalParticleDiameters(mm)Photochemicalaerosols0.01-1Tobaccosmoke0.25Coalflyash1-50Flourdust15-20Pollens15-70Humanhair:~25-100mmExampleimagesofatmosphericparticlesSource:http://www.mpch-mainz.mpg.de/~kosmo/AerosolsourcesAerosolsourcesWindblowndustfromDesertSulfateaerosolfromvolcanoeruption,fuelcombustionandmicrobialactivities.SeasaltaerosolfromseasprayandbubbleburstingSootfromfuelcombustionSecondaryorganicaerosolfromvolatileorganiccompoundsAerosolRadiativeForcing:directeffectTheeffectofaerosolontheenergyfluxoftheatmospheredependsonparticlesizeandcomposition.Darkparticles(soot–containing)tendtoabsorblight,thuswarmingEarth’satmosphere.Smallparticlestendtoscatterlight,thusincreasingthealbedooftheatmosphere.Aerosolandcloudcondensationnuclei(CCN)CloudCondensationNuclei(CCN)areparticlesthatcanbecomeactivatedtogrowtofogorclouddropletsinthepresenceofasupersaturationofwatervapor.IftheEarth’satmosphereweretotallydevoidofparticles,cloudscouldnotform.Aerosolradiativeforcing:indirecteffectAnincreaseinthenumberofatmosphericparticleswouldincreasethenumberofcloudcondensationnuclei,thereforemorecloudcoverandhigheralbedoShiptrackingphenomenonVolcanoesandclimatechangeLargevolcanoeruptionsprovidedramaticevidenceoftheabilityofaerosolstoaffectglobalclimate.Mt.Pinatuboeruptionmade1992thecoolestyearsince1986Redline:modeledtemperaturechangesBlueline:temperaturechangesobservedfrommeteorologicalgroundstationsVolcanicCoolingLargevolcaniceruptionscancooltheEarthbyincreasingthealbedo.Calculatetheexpectedtemperaturechangeifthealbedoincreasesfrom30to30.5percent.ComparethisestimatewiththetemperaturerecordaftertheMt.Pinatuboeruption.(Textbook,pp150).1816-theyearwithoutasummerIn1815,TamborainIndonesiaexplodedandthevolcanodustblanketedtheNorthernHemisphere.Thefollowingyear,1816,dailyminimumtemperatureswereabnormallylowinthenorthernhemispherefromlatespringtoearlyautumn.Faminewaswidespreadbecauseofcropfailures.Anestimated82,000werekilledindirectlybytheeruptionbystarvation,disease,andhunger.SulfateaerosolformationfromvolcanoeruptionsLargeamountofSO2isinjectedintotheatmospherefromtheforceofthevolcanoeruption.SO2canbeconvertedtosulfateingasandaqueousphase.Ingas-phaseSO2+.OH+MHOSO2.+MHOSO2.+O2HO2.+SO3SO3+H2O+MH2SO4+M

Sulfateaerosolformationfromvolcanoeruptions(Continued)Inaqueousphase,dissolvedSO2isoxidizedtosulfatebyO3 (dominantpathwaywhenpH>5)H2O2 (dominantpathwaywhenpH<5)organicperoxidesO2catalyzedbyironandmanganeseTheoxidationofSO2(aq)byH2O2proceedsasfollows:HSO3-+H2O2SO2OOH-+H2OSO2OOH-+H+H2SO4SulfateformationfrombiogenicgasesDimethylsulfide(DMS):CH3SCH3MarineoriginProducedinplanktonbytheenzymaticcleavageofdimethylsulfonopropionate,acompoundthathelpplanktonachieveosmoticbalanceinthesaltyoceanwater.OxidationofDMSSO2sulfateH2STerrestrialoriginProducedbysulfate-reducingbacteria.Example:KuwaitOilFires

Airtemperaturesbelowtheplumeswerereportedtobeabout7oClowerthaninadjacentareaswithoutsmoke.ColdestMayin35years.Averagetemperatureswereabout4oClowerthannormal.AerosolEffectsonClimateDirectEffectsAerosolsscatterandabsorbvisibleandinfraredradiationOveralleffect:coolingLightscatteringdependsonsizedistributionandindexofrefractionoftheparticlesIndirectEffectsServeasCloudcondensationnucleiMoreCCNleadstomorecloudcoverPossibleeffectsincludechangesinEarth'salbedoandchangesinhydrologicalcycleClimate-GreenhouseEffectGreenhouseGlass,thematerialthatgreenhouseismadeof,1)transmitshort-wavelengthvisiblelight,2)absorbsandredirectsthelongerwavelengthsofenergy.Thesetwoaspectsmakethegreenhousewarmerthanoutsideairtemperature.GreenhouseeffectoftheatmosphereLightfromthesunincludestheentirevisibleregionandsmallerportionsoftheadjacentUVandinfraredregions.Sunlightpenetratestheatmosphereandwarmstheearth’ssurface.Longerwavelengthinfraredradiationisradiatedfromtheearth’ssurface.AconsiderableamountoftheoutgoingIRradiationisabsorbedbygasesintheatmosphereandreradiatedbacktoearth.Thegasesintheatmospherethatactlikeglassinagreenhousearecalledgreenhousegases.NaturalGreenhouseeffectThenaturalgreenhouseeffectcausesthemeantemperatureoftheEarth'ssurfacetobeabout33oCwarmerthanitwouldbeifnaturalgreenhousegaseswerenotpresent.EnhancedgreenhouseeffectWhenconcentrationsofgreenhousegasesincrease,moreinfraredradiationisreturnedtowardtheearthandthesurfacetemperaturerises.Whatmakesagasgreenhousegas?AbletoabsorbinfraredlightMusthavemolecularvibration(s)Thisexcludesmonoatomicgasesasgreenhousegases.(Thatiswhyargon,thethirdmostabundantatmosphericconstituentsistransparenttoinfraredirradiation)Themolecularvibrationsm