简介：Chemicalcomposition,hourlycounts,andsizesofatmosphericcarbonaceousparticlesweremeasuredtoinvestigatetheirmixingstateonclearandhazydays.623,122carbonaceousparticleswithsizes0.2-2.0μmwasanalyzedusingasingle-particleaerosolmassspectrometerfrom1stto17thJanuary2013.Particletypesincludedbiomass/biofuelburningparticles(biomass),elementcarbon(EC-dominant)particlesthatwerealsomixedwithbiomass/biofuelburningspecies(EC-biomass)orsecondaryspecies(EC-secondary),organiccarbon(OC),internallymixedOCandEC(OCEC),ammonium-containing(ammonium)andsodium-containing(sodium)particles.Oncleardaysthetoprankedcarbonaceousparticletypeswerebiomass(48.2%),EC-biomass(15.7%),OCEC(11.1%),andsodium(9.6%),whileonhazydaystheywerebiomass(37.3%),EC-biomass(17.6%),EC-secondary(16.6%),andsodium(12.7%).ThefractionsofEC-secondary,ammonium(10%),andsodiumparticletypeswereelevatedonhazydays.NumbersofEC-secondaryparticlesweremorethanfourtimesthoseoncleardays(4.1%).Thus,carbonaceousparticlesmixedwithammonium,nitrateandsulfateduringagingandtransport,enhancingtheirlightextinctioneffectsandhygroscopicgrowthunderhighrelativehumidityonhazydays,furtherreducingvisibility.Ourreal-timesingle-particledatashowedthatchangestomixingstatehadasignificantimpactonlightextinctionduringhazeeventsinNanjing.