Chemical characterization and source apportionment

Atmos.Chem.Phys.,13,7053–7074,2013:10.5194/acp-13-7053-2013©Author(s)2013.CCAttribution3.0License.EGUJournalLogos(RGB)AdvancesinGeosciencesOpenAccessNaturalHazardsandEarthSystemSciencesOpenAccessAnnalesGeophysicaeOpenAccessNonlinearProcessesinGeophysicsOpenAccessAtmosphericChemistryandPhysicsOpenAccessAtmosphericChemistryandPhysicsOpenAccessDiscussionsAtmosphericMeasurementTechniquesOpenAccessAtmosphericMeasurementTechniquesOpenAccessDiscussionsBiogeosciencesOpenAccessOpenAccessBiogeosciencesDiscussionsClimateofthePastOpenAccessOpenAccessClimateofthePastDiscussionsEarthSystemDynamicsOpenAccessOpenAccessEarthSystemDynamicsDiscussionsGeoscientificInstrumentationMethodsandDataSystemsOpenAccessGeoscientificInstrumentationMethodsandDataSystemsOpenAccessDiscussionsGeoscientificModelDevelopmentOpenAccessOpenAccessGeoscientificModelDevelopmentDiscussionsHydrologyandEarthSystemSciencesOpenAccessHydrologyandEarthSystemSciencesOpenAccessDiscussionsOceanScienceOpenAccessOpenAccessOceanScienceDiscussionsSolidEarthOpenAccessOpenAccessSolidEarthDiscussionsTheCryosphereOpenAccessOpenAccessTheCryosphereDiscussionsNaturalHazardsandEarthSystemSciencesOpenAccessDiscussionsChemicalcharacterizationandsourceapportionmentofPM2.5inBeijing:seasonalperspectiveR.Zhang1,*,J.Jing1,2,*,J.Tao3,*,S.-C.Hsu4,*,G.Wang5,J.Cao5,C.S.L.Lee6,L.Zhu3,Z.Chen7,Y.Zhao7,andZ.Shen81KeyLaboratoryofRegionalClimate-EnvironmentResearchforTemperateEastAsia,InstituteofAtmosphericPhysics,ChineseAcademyofSciences,Beijing,China2MeteorologicalObservationCenterofCMA,Beijing,China3SouthChinaInstituteofEnvironmentalSciences,MinistryofEnvironmentalProtection,Guangzhou,China4ResearchCenterforEnvironmentalChanges,AcademiaSinica,Taipei,Taiwan5KLAST,SKLLQG,InstituteofEarthEnvironment,ChineseAcademyofSciences,Xi’an,China6InstituteofEarthSciences,AcademiaSinica,Taipei,Taiwan7ESPC,CollegeofEnvironmentalSciencesandEngineering,PekingUniversity,Beijing,China8DepartmentofEnvironmentalScienceandEngineering,Xi’anJiaotongUniversity,Xi’an,China*Theseauthorscontributedequallytothiswork.Correspondenceto:S.-C.Hsu([e-mail])Received:9March2013–PublishedinAtmos.Chem.Phys.Discuss.:16April2013Revised:19June2013–Accepted:25June2013–Published:25July2013Abstract.Inthisstudy,121dailyPM2.5(aerosolparticlewithaerodynamicdiameterlessthan2.5μm)sampleswerecollectedfromanurbansiteinBeijinginfourmonthsbe-tweenApril2009andJanuary2010representingthefourseasons.Thesamplesweredeterminedforvariouscom-positions,includingelements,ions,andorganic/elementalcarbon.Variousapproaches,suchaschemicalmassbal-ance,positivematrixfactorization(PMF),trajectorycluster-ing,andpotentialsourcecontributionfunction(PSCF),wereemployedforcharacterizingaerosolspeciation,identifyinglikelysources,andapportioningcontributionsfromeachlikelysource.Ourresultshaveshowndistinctiveseasonal-ityforvariousaerosolspeciationsassociatedwithPM2.5inBeijing.Soildustwaxesinthespringandwanesinthesum-mer.Regardingthesecondaryaerosolcomponents,inorganicandorganicspeciesmaybehaveindifferentmanners.Theformerpreferentiallyformsinthehotandhumidsummerviaphotochemicalreactions,althoughtheirprecursorgases,suchasSO2andNOx,areemittedmuchmoreinwinter.Thelatterseemstofavorablyforminthecoldanddrywinter.Synopticmeteorologicalandclimateconditionscanover-whelmtheemissionpatternintheformationofsecondaryaerosols.ThePMFmodelidentifiedsixmainsources:soildust,coalcombustion,biomassburning,trafficandwastein-cinerationemission,industrialpollution,andsecondaryin-organicaerosol.Eachofthesesourceshasanannualmeancontributionof16,14,13,3,28,and26%,respectively,toPM2.5.However,therelativecontributionsoftheseidenti-fiedsourcessignificantlyvarywithchangingseasons.TheresultsoftrajectoryclusteringandthePSCFmethoddemon-stratedthatregionalsourcescouldbecrucialcontributorstoPMpollutioninBeijing.Inconclusion,wehaveunraveledsomecomplexaspectsofthepollutionsourcesandforma-tionprocessesofPM2.5inBeijing.Toourknowledge,thisisthefirstsystematicstudythatcomprehensivelyexploresthechemicalcharacterizationsandsourceapportionmentsofPM2.5aerosolspeciationinBeijingbyapplyingmultipleap-proachesbasedonacompletelyseasonalperspective.1IntroductionParticulatematter(PM)iscomposedofvariouschemicalcomponents(Seinfeld,1989).PMprofoundlyaffectsourliv-ingenvironmentsintermsofairquality(incloserelationtopublichealth),visibility,directandindirectradiativeforcing,PublishedbyCopernicusPublicationsonbehalfoftheEuropeanGeosciencesUnion.7054R.Zhangetal.:ChemicalcharacterizationandsourceapportionmentofPM2.5inBeijingclimateeffectsandecosystems(Watson,2003;Streetsetal.,2006;AndreaeandRosenfeld,2008;Mahowald,2011).Numerousepidemiologicalstudieshavedemonstratedthatlong-termexposuretopronouncedPM2.5increasesmorbid-ityandmortality(DockeryandPope,1994;Popeetal.,1995;Schwartzetal.,1996).Givenitstinysize,fine-modePM(i.e.,PM2.5,PMwithaerodynamicdiameterlessthan2.5μm)canreadilypenetratethehumanbronchiandlungs(Popeetal.,1995;Oberd¨orster,2001).Throughabsorptionandscatter-ingof