Theimportantrolesofsurfacetensionandgrowthrateinthecontributionofnewparticleformation(NPF)tocloudcondensationnuclei(CCN)numberconcentration:evidencefromfieldmeasurementsinsouthernChina
Abstract
Thecontributionofnewparticleformation(NPF)tocloudcondensationnuclei(CCN)numberconcentration(NCCN)varieslargelyunderdifferentenvironmentsanddependsonseveralkeyfactorssuchasformationrate(J),growthrate(GR),distributionofpreexistingparticles,andpropertiesofnewparticlesduringNPFevents.ThisstudyinvestigatesthecontributionofNPFtotheNCCNanditscontrollingfactorsbasedonmeasurementsconductedattheHeshansupersite,inthePearlRiverDelta(PRD)regionofChinaduringfall.Thesize-resolvedcloudcondensationnucleiactivityandsize-resolvedparticlehygroscopicityweremeasuredbyacloudcondensationnucleicounter(CCNc)andahygroscopictandemdifferentialmobilityanalyzer(HTDMA),respectively,alongwithascanningmobilityparticlesizer(SMPS)andadiethyleneglycolscanningmobilityparticlesizer(DEG-SMPS)forparticlenumbersizedistribution(PNSD).AtypicalNPFeventon29OctoberwaschosentoinvestigatethecontributionoftheNPFtoNCCNunderseveralsupersaturation(SS)ratios.Twoparticleproperties(hygroscopicityandsurfacetension)affectCCNactivationwiththelatterbeingmoreimportantintermsoftheCCNconcentration(NCCN).Alowervalueofsurfacetension(i.e.,0.06?N?m?1)thanthepure-waterassumption(0.?N?m?1)couldincreasetheNCCNatSS??=??1.0?%byabout20?%duringthenoneventperiodandbyabout40?%duringtheevent.Inaddition,anearlierpeaktimecorrespondingtoalowercriticaldiameter(D50)wasalsoobserved.Theresultsshowthathighformationrate,growthrate,andlowbackgroundparticleconcentrationleadtohighnumberconcentrationsofnewlyformedparticles.ThehighgrowthratewasfoundtohavethemostsignificantimpactontheNCCN,whichcanbeattributedtothefactthatahighergrowthratecangrowparticlestotheCCNsizeinashortertimebeforetheyarescavengedbypreexistingparticles.TwootherNPFevents(aneventon18Octoberinthiscampaignandaneventon12DecemberinPanyu)werechosentoperformsensitivitytestsunderdifferentscenarios(growthrate,formationrate,andbackgroundparticleconcentration).ThecalculatedNCCNatSS?=?1.0?%on12Decemberwassignificantlylowerthanthatfromtheothertwoevents.Theeventon12Decemberwasre-simulatedusingthegrowthratetakenfromtheeventon18OctoberwhichresultedinsimilarCCNconcentrationsbetweenthetwoevents(12Decemberand18October),implyingthatthegrowthrateisthemajorimpactfactorforCCNactivation.OurresultshighlighttheimportanceofgrowthrateandsurfacetensionwhenevaluatingthecontributionofNPFtotheNCCN.
Reference
Cai,M.,Liang,B.,Sun,Q.,Liu,L.,Yuan,B.,Shao,M.,Huang,S.,Peng,Y.,Wang,Z.,Tan,H.,Li,F.,Xu,H.,Chen,D.,andZhao,J.:Theimportantrolesofsurfacetensionandgrowthrateinthecontributionofnewparticleformation(NPF)tocloudcondensationnuclei(CCN)numberconcentration:evidencefromfieldmeasurementsinsouthernChina,AtmospericChemistryandPhysics,21,–,
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