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TROPOSPHERICAEROSOLSPartII:secondaryaerosol销售信•Dimethylsulfide(DMS)•SO2emissionsfromvolcanoes•IndustrialSO2emissions•Nitrogenoxidesandammonia•VolatileOrganiccompounds(VOC)DMS,(CH3)2S,isthemajoroneofbiogenicgasesemittedfromsea•isproducesduringdecompositionofdimethyl-sulfonpropionate(DMSP)fromdyingphytoplankton•meanresidencetimeisabout1-2days-mostofSfromDMSisalsore-depositedintheocean•onlysmallfractionlostintotheatmosphereDimethylsulfide•RecentglobalestimatesofDMSfluxfromtheoceansrangefrom8to51TgSa-1•Thisis50%oftotalnaturalS-emissions(presentlynearlyequivalenttoanthropogenicemissions,76TgSa-1)-Differencesinthetransfervelocitiesinsea-to-aircalculations•Uncertaintiesaredueto:-DMSseawatermeasurements(paucityofdatainwintermonthsandathighlatitudes)DMSandClimate•DMSisemittedbyphytoplanktonasanaturalbiproductofmetabolism–Possiblyrelatedtoradiationprotection•Givesseawateritscharacteristicsmell•Formsmuchofthenaturalaerosol(sub-micronparticles)inoceanicair•DMSisthemajorbiogenicgasemittedfromseaandthemajorsourceofStotheatmosphere.ItcontributestothesulfurburdeninboththeMBLandFT.FigureadaptedfromCharlsonetal.(1987)“Oceanicphytoplankton,atmosphericsulphur,cloudalbedoandclimate”Nature,vol.326,pp.655-661TheCLAWHypothesis(Charlson,Lovelock,AndreaeandWarren,1987)•DMSfromtheoceanaffectscloudpropertiesandcanfeedbacktotheplanktoncommunity•Thisactstoregulateclimatebyincreasingcloudalbedowhensea-surfacetemperaturesrise.Sea-to-airtransportOceanDMSAtmosphereDMSAtmosphericchemistryAerosolCloudProperties(albedoandlifetime)CloudphysicsSurfaceTemperatureandLightImpactofcloudonatmosphericradiationPlanktonCommunityConditionsinthesurfaceoceanBiologicalandchemicalinteractionsBackdropfromtheNOAACentralLibraryPhotoCollectionDMSoxidation•TheatmosphericoxidationpathwaysthatleadfromDMStoionicspecies(essentiallysulfateandmethanesulfonicacid,MSA,CH3SO3H)arecomplexandstillpoorlyunderstood•ThefirststeptosulfateisSO2•SO2islargelydominantvsMSA,exceptathighlatitudes(reasonsunclear)•MSAisuniquefortracingmarinebiologicalactivity,sinceithasnoothersourceAboutatmosphericSO2•SO2hasseveralsources:-eithernatural:marineMSAandvolcanism-oranthropogenic:miningandfossilfuelburning•ItsoxidationwaystoSO4--arestillmattertoinvestigation,inparticularwiththeaidofS&Ostableisotopes•ThiscanoccureitherinthegaseousphasebyOHradicalsorintheliquidphasebyO3orH2O2.•Generallygaseousphaseprocessisdominant,exceptinregionsofhighseasaltconcentrations0%50%100%Percent(%)changeinconcentrations(yearlyaverage)CaseA:SO2/SO42-concentrationwithoutsea-saltchemistryCaseB:Withsea-saltchemistrySO2(decrease)SO42-(smallincrease)|100|CaseACaseBCaseAEffectofsea-saltchemistryonSO2andSO42-concentrations50%0%100%Effectofsea-saltchemistryongas-phasesulfateproductionrates|100|CaseACaseBCaseAMar/Apr/MayJun/Jul/AugSep/Oct/NovDec/Jan/FebPercent(%)decrease(seasonalaverage):AqueousversusGasPhaseOxidationBiologicalregulationoftheclimate?(Charlsonetal.,1987)DMSOHNO3SO2H2SO4OHNewparticleformationCCNH2O2LightscatteringGas-phaseO3SO2emissionsfromvolcanoes(1)•VolcanoesareamajornaturalsourceofatmosphericS-species•Injectionsaregenerallyoccurringinthefreetroposphere•MostactivevolcanoesareintheNorthernHemisphere(80%)•Thestrongestsourceregionisthetropicalbelt,inparticularIndonesia•EmissionsareintheformofSO2,H2SandSO4--SO2emissionsfromvolcanoes(2)•560volcanoesovertheworldarepotentialSO2sources,butonlyafewhavebeenmeasured•Volcanicactivityissporadic,withafewcataclysmiceruptionspercentury•Cataclysmiceruptionsinjectashparticlesandgases(mainlySO2)intothestratosphere,whereH2SO4formedformsaveil(«Jungelayer»)VolcanolocationsContinuouslyeruptingvolcanoesAtmosphericimpactofvolcanoesSO2relativelyinsoluble,resiststroposphericwashoutInjectedintothestratosphereinlargequantities(Pinatubo,1991~20Tg)Instratosphere,SO2oxidisestoproducesulfuricacidaerosols(H2SO4)ConversionofSO2toH2SO4slow(months),aerosolcloudreplenishedmonthsaftereruption•ThetotalamountofvolcanictroposphericS-emissionsispresentlyestimatedat:14+/-6Tga-1Meanvolcanicsulfuremissionsareofcomparableimportancefortheatmosphericsulfateburdenasanthropogenicsourcesbecausetheyaffectthesulfateconcentrationsinthemiddleanduppertropospherewhereasanthropogenicemissionscontrolsulfateintheboundarylayer.S-isotopemeasurementsincentralpolarregions(i.e.inthefreetroposphere)seemtosupporttheimportantroleofvolcani