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1、SECTION7ChemistryofaerosolDefinitionandsortofaerosol(1)DefinitionAdispersionofmicroscopicsolidorliquidparticlesingaseousmediumiscalledaerosol.Particulatematterintheatmospherecanbenaturalorman-made.Forexample,sulfateaerosolisfromvolcanoeruption,fuelcombustiona
2、ndmicrobialactivities.Seasaltaerosolisfromseasprayandbubblebursting.Sootisfromfuelcombustion.Secondaryorganicaerosolisfromvolatileorganiccompounds.(2)SortofaerosolAccordingtocauseofformationofaerosol,aerosolisdividedintodecentralizationaerosolandagglomeration
3、aerosol.Accordingtodiameterofaerosol,aerosolisdividedintototalsuspendedparticulates(TSP),precipitatedparticles,floatingparticles,andinhalableparticles.Dynamicsdiameterofparticleisabout0.001～100μm.Largeparticlescansettleoutoftheatmospherebysedimentationintheea
4、rth’sgravitationalfield.Theparticle,morethan10μm,iscalledprecipitatedparticles.Thesmallersolidparticleshaveamaximumconcentrationabout18kmabovetheearth’ssurface.Theparticle,lessthan10μm,iscalledfloatingparticles.Table1Conformationandmaincharacteristicofaerosol
5、2.SourceandcollectionofaerosolTable2EmissionsandsourceofaerosolintheglobeTheparticlesintheatmosphereareknowncollectivelyastheatmosphericaerosol.Theirsizedistributionisverywide,butasseeninFigure3,theaerosolisdominatedbythesmallestparticles.Dustandseasprayarebl
6、ownaboutbythewindingreatquantity,buttheseparticlesarelargeandsettleoutrapidly.3.SizedistributionofaerosolFigure1sizedistributionofaerosolThesubmicrometerparticlesareformedmainlybyoxidationofsulfur-,nitrogen-,andcarbon-containinggasesintheatmosphere.Theseparti
7、clesstayaloftmuchlonger,withlifetimesofdaysorweeks.Gradually,theygrowtolargeronesviacollisionsandaggregation,andsettleout.Nolong-termaccumulationintheloweratmosphereortroposphereisthuspossible.Figure2DistributionofconcentrationofnumbersurfaceareavolumeFigure3
8、SizedistributionofaerosolWhitbymodel:aitkennucleusmodel(0.001～0.05μm),accumulationmode(0.05～2μm),andcoarseparticlemode(>2μm).Nucleusformationprocessisasfollow.(1)Granuleisformedanddispers
