Secondary organic aerosol origin in an urban environment

23 Pages·2016·2.07 MB·English

by  M. C. Minguillón

Faraday Discussions
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e.
M. enc Secondary organic aerosol origin in an
54 Ad Lic urban environment: influence of biogenic
2:29:porte and fuel combustion precursors†
1n
3 U
2023.0
27/on M. C. Minguillo´n,*a N. Pe´rez,a N. Marchand,b A. Bertrand,b B. Temime-
n 2/buti Roussel,b K. Agrios,c S. Szidat,c B. van Drooge,a A. Sylvestre,b
ed oAttri A. Alastuey,a C. Reche,a A. Ripoll,a E. Marco,a J. O. Grimalta
nloadmons and X. Querola
wm
5. Doe Co Received18thNovember2015,Accepted8thDecember2015
1v
20ati DOI:10.1039/c5fd00182j
ber Cre
cemer a Sourcecontributionsoforganicaerosol(OA)arestillnotfullyunderstood,especiallyinterms
Dend ofquantitativedistinctionbetweensecondaryOAformedfromanthropogenicprecursorsvs.
08 d u thatformedfromnaturalprecursors.InordertoinvestigatetheOAorigin,afieldcampaign
n se
on wascarriedoutinBarcelonainsummer2013,includingtwoperiodscharacterizedbylow
blished e is lice adnudrinhgigthhetrasffieccocnodnpdeitrioionds,.eVsoplaetciliealloyrgaaronmicactoicmhpyoduroncda(rVbOonCs)rceolantceednttroatitoranffiscweermeishsiigohnesr,
e. Puarticl which showed a marked daily cycle peaking during traffic rush hours, similarly to black
s Articl This ccahrabnognes(BfrCo)mcothnecelonwtrattoionthse. BhiiogghetnraicffiVcOpCerio(BdV,OanCd) tchoenirceinnttrraa-tdioanysvashrioabwileitdywonalsyremlainteodr
s
e to temperature and solar radiation cycles, although a decrease was observed for
c
c
A monoterpenesduringtheday.Theorganiccarbon(OC)concentrationsincreasedfromthe
n
pe firsttothesecondperiod,andthefractionofnon-fossilOCasdeterminedby14Canalysis
O
increasedfrom43%to54%ofthetotalOC.Thecombinationof14CanalysisandAerosol
ChemicalSpeciationMonitor(ACSM)OAsourceapportionmentshowedthatthefossilOC
was mainly secondary (>70%) except for the last sample, when the fossil secondary
OConlyrepresented51%ofthetotalfossilOC.Thefractionofnon-fossilsecondaryOC
increasedfrom37%oftotalsecondaryOCforthefirstsampleto60%forthelastsample.
This enhanced formation of non-fossil secondary OA (SOA) could be attributed to the
reaction of BVOC precursors with NO emitted from road traffic (or from its nocturnal
x
derivativenitratethatenhancesnight-timesemi-volatileoxygenated OA(SV-OOA)),since
NO concentrationsincreasedfrom19to42mgm(cid:1)3fromthefirsttothelastsample.
2
aInstituteofEnvironmentalAssessmentandWaterResearch(IDAEA),CSIC,08034Barcelona,Spain.E-mail:
[email protected]
bAixMarseilleUniversit´e,CNRS,LCEUMR7376,13331Marseille,France
cDepartmentofChemistryandBiochemistry&OeschgerCentreforClimateChangeResearch,Universityof
Bern,3012Bern,Switzerland
†Electronic supplementary information (ESI) available: Sections 1 to 6, with 12 gures. See DOI:
10.1039/c5fd00182j
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1 Introduction
CarbonaceousaerosolsmakeupalargeproportionofambientPM ,PM and
10 2.5
PM (atmospheric particulate matter ner than 10, 2.5 and 1 mm, respectively).
1
WorldwidetroposphericsubmicronPMmaybefrom20to90%organicaerosol
e. (OA).1OA,alsonamedorganicmatter(OM),mayaccountfor15–26%ofbothPM
54 AM. d Licenc sainteds.P2MF2o.5riEnuEruorpoepaen,wreigthiotnhaelhbiagchkegsrtoluonaddssbiteeisngOrMeco+rdEeCda(etluemrbeanntaalndcatrrbaoffin1c0)
12:29:nporte 3ratnog7edmgfrmom(cid:1)32a7n%dt3oto437%mgofmP(cid:1)M32i.n5.3POMMcfoonrcreenmtroattei-ornurraaln,ugerbdafnrobmac2kgtoro4umngd,ma(cid:1)n3d,
3 U 2.5
2023.0 traffic and industrial hotspots in Spain, respectively (approx. 25–30%, 20–40%
7/n and30–40%ofPM ).4
2o 2.5
n 2/buti InspiteoftheserelativelyhighproportionsinambientPM,sourcecontribu-
ed oAttri tions of OA are still not fully understood5–7 due to the mixed source origins
nloadmons (faonrmthartoiponogoefnOicA.oMr boiroegoevneri,cOOAAm) aanydbethperimatamryos(PpOheAr)i,cempriottceedssaessstohliadt/lciaquuside PthMe
wm
5. Doe Co fartommosbpohthereantfhrormopovgoelnaitcileorobrigoagneinciccsoomurpcoeus,nodrsse(VcoOnCdsa),ryw(ShOicAh),fcoarnmehdavinetahne
1v
20ati anthropogenicorbiogenicorigin(AVOCsorBVOCs).7,8Furthermore,inurbanor
ber Cre industrial areas, the high concentrations of specic anthropogenic pollutants
ma
eceder (e.g.NOx,SO2andO3)mayenhancetheformationofsecondaryorganicaerosols
08 Dd un from biogenic precursors (BSOA), giving rise to the so-called enhanced BSOA
n se (eBSOA),7which,despiteitsbiogenicorigin,wouldbeanthropogenicallydriven.
on
blished e is lice sTehveerinaltesrtaucdtiieosnhbaevtewreeepnotrhteedBhViOgChse–rOyi3e–lNdOsxo–fSeOBASOsyAstfeomrmsaistivoenryfrcoommpisloexp.r9eTnheuisn,
e. Puarticl tthioenpbreecseonmceesolforweelartfioverlvyehryighhigchonNcOentcraotniocennstoraftNioOnxs,.7a,1l0thFoourgthhethhiisgShOlyArefoarcmtivae-
s Articl This spersoqbuaibtleyrpdeuneestoththeeinlotewravcotliaotniliwtyitohfNtxhOexsseeseqmusitearlpsoenteoninitcrraetaesse.7tChoenSvOerAseyliye,ldfosr,
s
e
Acc monoterpenes increasing NOx/VOC ratios have shown to reduce the BSOA
n formationfromozonolysisofa-pinene,andhighlyvolatileN-containingorganic
e
Op species are preferentially formed under these conditions.11 Other atmospheric
species different to NO , OH radical and O may have a large impact on BSOA
x 3
formation. Thus, a higher BSOA yield from isoprene can occur under acidic
conditionscausedbytheoccurrenceofsulphuricacid.12VOCsplayaveryrelevant
roleinsulphuricacidrelatednucleationeventsandinthegrowthofnewlyformed
particles.13 In any case, one of the major BSOA formation pathways, especially
under high NO and O concentrations, seems to be related to the nocturnal
x 3
oxidationofVOCsbythenitrateradical(aproductoftheNO +O interaction)
2 3
reaction.7 Thus, both organo-sulphates and organo-nitrates may constitute an
important fraction of the SOA due to the prevalence of the above formation
pathways.14Hence,itisexpectedthatOAconcentrationsinurbanenvironments
will increase compared with those from rural areas due to (a) the enlarged
anthropogenicPOAandVOCemissionsleadingtoanthropogenicSOA,butalsoto
(b)eBSOAformationduetotheinteractionofBVOCswithotheranthropogenic
components.
ThecityofBarcelona,NESpain,hasoneofthehighestcardensitiesinEurope,
withdieselvehiclesmakinguparound47%oftheeet.15Inspiteofthisadverse
338 | FaradayDiscuss.,2016,189,337–359 Thisjournalis©TheRoyalSocietyofChemistry2016
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fact, PM concentrations have decreased in the last decade,16 going down from
x
about40mgm(cid:1)3to22–30mgm(cid:1)3PM .
10
UrbanbackgroundOAaccountedfor20%ofthePM and>30%ofthePM
10 2.5
and PM in 2003–2007.17 The SOA contribution to OA, calculated with the EC
1
tracermethod,18was36–40%.Hence,OA,includingSOA,isamajorcomponentof
M. ence. PinMExuinrotphee.cityofBarcelonaand,ingeneral,inregionalandurbanenvironments
54 Ad Lic Prior studies carried out at an urban background site during the DAURE
12:29:nporte OcaCmpanaidgnEiCnMreaprocrhte2d00a9upsroinpgoraticoonmbofinnatoino-nfoosfsHilRO-TCoFo-fAM60S%anodf14tCheantoaltyaslisOoCf
3 U
2023.0 measuredinPM1,while57%oftheSOAwasnon-fossil.19,20Thisnon-fossilSOA
7/n could be BSOA or eBSOA. Relatively strong correlations were found between
2o
n 2/buti dicarboxylicacidsandotheroxidationproductsfromBVOCs,andtheoxygenated
nloaded omons Attri scOeeAirlnl(eiOn,2Og3Aatn)hdleoBahdiirigmnhginnignohntah-mfeo,su2s4rilabmaOnoAnbgcaoconktgthrreiobruulnotidcoanotifowBneasrr.eceolobntaai.n21edSiminilaZrurriecshu,l2t2sMcoanr--
wm
5. Doe Co detIenrmorindienrgtothienrveelsattiigvaetceotnhteriobruitgiionnosffrOomAiPnOBAaarcnedloSnOaA,,wainthdtshpeecainatlhirnotpeoregsetniinc
1v
20ati and the biogenic fractions, a measurement campaign was devised in summer
ber Cre 2013,includingthelastweeksofAugustandthebeginningofSeptember,coin-
ma
ceer cidingwithaperiodofhighinsolationandhighBVOCemissions.Animportant
Dend proportionofBarcelona'spopulationtakesholidaysinAugust,thustrafficowis
n 08 sed u substantially reduced compared with the rest of the year. Hence, the campaign
e. Published oarticle is licen ucd14oseCmutearpalmnriasionleywadst.iiasTonhloo,rfwoouOnrgoClhia,ndetohtfflVeraOicffinCoemcmPpbMeeinarisaoiutndirooeanrmngoadefnncitscosenv(aetunirnsadiulneagodnrPgawaTlyhnRteii-ccTnaocltFhht-oeeMmotSlrsi)ac,,ffiasolucncclriohenmseaupsmooorsegfflidatiinonitinecs
s Articl This aspereocsiaotliocnonmceonntirtaotrio(AnCaSnMd))t,yopnelsi/nsoeubrlcaecskdcaertebromni(nBaCti)omne(aussuinregmaeenrotss,oalncdheomnliicnael
s
cce NO, NO2, O3, CO, SO2, PM10, PM2.5 and PM1 concentration measurements, we
n A investigatedwhyandhowroadtrafficemissionsinuencetheconcentrationsand
e
p originofOAinthecity.
O
2 Experimental
An intensive monitoring campaign at the urban background of Barcelona was
carriedoutfrom16Augustto6September2013.Twoperiodsaredistinguished:
asummerholidayperiodwithlowtrafficintensity(16–25August)namedthelow
traffic (LT) period, and a typical urban traffic emissions period (28 August–6
September), named the high traffic (HT) period, both characterized by similar
environmentalconditionsandhighinsolation.
MeasurementswerecarriedoutattheurbanbackgroundsitePalauReial(PR;
41(cid:3)2301400N,02(cid:3)0605600E,78ma.s.l.,Fig.S1†),located200mfromoneofthemain
trafficavenuesofthecity(trafficdensityof90000vehiclesperworkingday).The
main source of atmospheric PM is road traffic, although contributions from
x
industry,regionalsecondaryatmosphericpollutants,construction,andshipping
arealsorelevant.17,25Atmosphericdynamicsaredrivenbythebreezeregime,with
aNWwindcomponentduringthenightandthedevelopmentofbreezesduring
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thedayturningprogressivelyfromSEtoSWdirection,withgraduallyincreasing
windspeedsreachingmaximumlevelsaroundnoon.26
2.1 OnlinemeasurementsofVOCsandothergaseouspollutants
MeasurementsofVOCswereperformedwithaProton-TransferReactionTimeof
e.
M. enc FlightMassSpectrometer(PTR-ToF-MS,IoniconPTRTOF8000,IoniconAnalytik,
2:29:54 Aported Lic awInnintdhsbdarruirecaktc,utibAoeunsttecrhmiaap)m.e27rb,2ae8truTprhereeastisnu3sr2te3ruKmxeecdonrtartews2ap.s0o5nodmpienbrgaartte,oddraiinnestluteabcnetrdivacorldtaecgldoensadttriet5in0og0ntsVh,
3 1Un appliedtothedritube(E)tobuffergasdensity(N)ratioof125Td(1Td¼10(cid:1)17
2023.0 V cm2). Mass spectra were recorded up to m/z 500 with a time resolution of
7/n
ed on 2/2Attributio w1saommoilpnlhueetea.toeIwndstahtrtruo3mu5g0ehn(cid:3)tCaa)lc.abVtaaOclkyCtgircmocuioxninndvgesrirgtaentriaotlhswaaatrseeffimecxeipaesrneutsrlseyedrdermeingouvpleaasrrltVysObpCyespra(bpsilslaliintoignnuthbmey
nloadmons volume(ppbv):29
wm
5. Doe Co [VOCH+]¼[H3O+]0[VOC]kt
1v
mber 20a Creati wprhimeraery[Hi3oOn+]0Ha3Ond+ [aVnOdCoHf+t]haereprthoteontraatnedsmvisoslaiotinlecoorrrgeacnteicd cdoemnspiotiuensdofiothnes
ceer respectively, in cps, k is the reaction rate constant between the VOC and H O+
ed 3
08 Dd un (cm3s(cid:1)1)andtistheresidencetimeoftheionsinthedritube(t¼100ms).A
n se calibrationgasstandard (TO-14AAromatic Mix,Restek Corporation, Bellefonte,
on
blished e is lice UtrSaAn)sm(1i0s0si(cid:4)on1e0ffipcpibenicny.nTithroegeesnti)mwaatsedusaecdcutroacayssiess3s0t%he.Areslpaeticviecmparsostodneptreanndsafnert
ss Article. Pu This articl airnacotlcweeut.crlaoTintneeenstmwtaanaatisstv3sce0odwaneasntsseeirgucmntseemidndeatfnotoitoranotghfeoenifoeqtnruhasaelntsfotariamVgcOpmalCtieinonwgntaiinosoflnepesteatrachfnhordrocmuoogmenhdptahoosunepnkltdihntteo(eTwrbaniabnslfeicrsao2gou)m.fnTtteehhnree--
e
cc tationpatterns.IonassignmentwassupportedbyofflineGC-MSanalysis.
A
n Real-time concentrations of NO and NO (Chemiluminescence, SIR S-5012),
e 2
p
O CO (Ecotech, GFC, EC 9830), O (UV absorption, SIR S-5014), and SO (Pulsed
3 2
Fluorescence,ThermoScienticModel43C)weremeasuredandsuppliedbythe
DepartmentofEnvironmentoftheAutonomousGovernmentofCatalonia.
2.2 Onlineaerosolmeasurements
Ultraneparticlenumbersizedistributionswithintherange15–660nm(N15–660,
5 min time resolution) were measured with a Scanning Mobility Particle Sizer
(SMPS), composed by a Differential Mobility Analyser (DMA, TSI 3081) coupled
with a condensation particle counter (CPC, TSI 3772). Equivalent BC mass
concentrations31weremeasuredbyamulti-angleabsorptionphotometer(MAAP,
model 5012, Thermo ESM Andersen Instruments, 1 min time resolution) with
aPM inlet.Semi-hourlyPM ,PM ,andPM concentrationsweremeasuredby
10 10 2.5 1
anopticalparticlecounter(GRIMM180)andcorrectedwithsimultaneous24hour
gravimetricsamples.
An Aerosol Chemical Speciation Monitor (Aerodyne Research Inc., ACSM)32
wasusedtomeasurenon-refractorysubmicronaerosolspecies(organicaerosol,
nitrate,sulphate,ammoniumandchloride)withatimeresolutionof15minutes.
340 | FaradayDiscuss.,2016,189,337–359Thisjournalis©TheRoyalSocietyofChemistry2016
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Mass calibration of the ACSM was based on determining the instrument
response factor (RF) using ammonium nitrate calibration aerosol.32 Relative
Ionization Efficiency (RIE) for ammonium was directly determined from the
ammoniumnitratecalibration(5.61).SulphateRIEwasdeterminedbydoingthe
aforementioned calibration exercise with ammonium sulphate monodisperse
e. aerosol,andresultedinavalueof1.38.ThedefaultRIEfororganicaerosol(1.4)33
M. enc has been used. The data were acquired using Aerodyne Research soware
54 Ad Lic ACSM_DAQ_v1438andprocessedwiththeACSMdataanalysissowareversion
12:29:nporte 1O.s5w.3e.g0o(,AOeRro,dUySnAe).RAesceoarrrecchtiIonnc.f)orwtrhiteteinnsitnruImgoenrtPpreorf(oWrmavaenMceetlriimcsi,taIntico.n,sLwakaes
3 U
7/202n 3.0 tarpaptiloiendsbwaesreedthoenntchoerrienclteetdpfroersspuarreticalnedcoNl2lescitgionnale.ffiThcieenaceyro(sCoEl)mfoalsloswcionngctehne-
2o
n 2/buti Middlebrookapproach.34Comparisonwithco-locatedmeasurements(real-time
nloaded omons Attri PtthiMecn1a,tcaioonrndreopcftaterhdtricealececposeirrzdieoinddgsistwtoriittbhhuedtsiioeffneinrdeteenrtteccromomrirpneaelarditsibooynnsas.nlopSeMs.PTS)healAloCwSeMddthateaiwdeenre-
wm
5. Doe Co
201ativ 2.3 Offlineaerosolanalyses
cember er a Cre 1P6M:020.5hsa–m0:p00leshwUeTrCe)coolnleqctueadrtizn8lhtetrismuesipnegrihoidgsh(0v:o0l0umh–e8:s0a0mhp,l8e:r0s0(3h0–1m6:300h(cid:1)h1a).nd
Dend A complete chemical characterization was performed.35 Briey, an acid
n 08 sed u digestionofhalflterwascarriedoutforeachsampletoyieldsolutionsforthe
s Article. Published o This article is licen csElbeeuolymaenbccmiscthsereesaoqniatodutenrnesesa.ntOofitSorfCpaonanemascatnhtblrdyaeyosrEsimIsqcCoouonacpalfo-yrComntpheca(rtreIijoCncoomarPtfrl-aaaActnttEaohidorgSebnr)toarsapnawlchnteaeeydrnreeaalewndlMymedesatreeeseNrnrsmH(tuSsS4isu+nbpenyedecsdcoIetnnttfro,rdocoEeummdnUceettSrit1tvArae.ye5trAilmoRyc(mn_iICnCs22oePbup-ypMrlstooleaeStlrodu)s.scbeeAollcWltee)toc.iam3oti6itonveinecsr
s
ce Molecular organic species were determined in the same lter samples aer
c
A
n extractionbyamixtureofmethanolanddichloromethane(1:1v/v),derivationof
pe esters to TMS-esters and subsequently detection and quantication in a gas-
O
chromatograph coupled to a mass-spectrometer (GC-MS) in full-scan mode.21
Hence,severalorganicspeciesinawiderangeofpolaritywereanalyzed,including
levoglucosan, hopanes, and formation products of VOC oxidation, such as
dicarboxylicacid,polyacids,andpolyols.
Additional24hPM sampleswerecollectedusinghighvolumesamplersand
2.5
usedfor14CanalysisontheOCfraction.TheseparationoftheOCandcollection
asCO wascarriedoutaccordingtotheSwiss_4Smethod.37The14Cisotopicratio
2
(fraction of modern carbon, fM) of each sample was determined using an
Accelerator Mass Spectrometer MICADAS (MIni CArbon Dating System) at the
LaboratoryfortheAnalysisofRadiocarbonwithAMS(LARA)38andcorrectedfor
theOCeldblank.
2.4 Supportingmeasurements
Meteorological variables (atmospheric pressure, wind components, solar radia-
tion, temperature and relative humidity) were recorded at a meteorological
station located 300 m from our sampling site and provided by the Faculty of
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Physics from the Universitat de Barcelona. Road traffic intensity data from the
DiagonalAvenueweresuppliedbytheCouncilofBarcelona(ServeideMobilitat).
2.5 Sourceapportionmenttotheorganicaerosol
e. The source apportionment to the organic aerosol was investigated by applying
54 AM. d Licenc APoCsSiMtiveorMgaantriicxmFaacstsosripzeacttiroan,(uPsMinFg)3t9huestinoogltkhiteSMouFilt(iSlionueracreEFnignidneer)(MveEr-s2i)o4n0t4o.8th.4e1
2:29:porte Thedatasetusedcomprisedfrom25Julyto19September2013.TheME-2allows
1n the user to introduce a priori information about sources e.g. using the a-value
3 U
2023.0 approach.Thustheusermay‘constrain’afactorbyintroducingitssourceprole
7/n anddetermining the extent to which the output prole can differ from the one
2o
n 2/buti inputtothemodel(thea-value).Onlym/z#120wereusedgiventhatthose>120
ed oAttri havelowersignaltonoiseandtheyaccountforaminorfractionofthetotalsignal.
nloadmons DetTahilessoonutrhceeadpiffpeorretinotnsmoleunttioonfsOaCrewgaisveanlsionatshseesrseesdulbtsasseedctoionnt.he14Cisotopic
wm
5. Doe Co troattaiolsO(CfMis).dTohneedknetoewrminigntahtieoinrfoMf.tThheecfoMntfroibrufotisosnilfsrooumrcdesiffiserzeenrot.sTouhrecfeMstooftOhCe
1v
20ati fromnon-fossilsources(fMOCnf)dependsonthecontributionfromthedifferent
ber Cre non-fossilsources,mainlybiomassburningandbiogenicsources,andithastobe
ma
ceer dened in advance,22 although subsequent iterations could beapplied if neces-
ed
08 Dd un sary.19Forthepresentstudy,thefMOCnfwascalculatedassuminga10/90share
n se betweenbiomassburningandbiogenicsource,inagreementwithotherstudies42
on
blished e is lice aemndisbsiaosnedsiosn1t.0h6e3A,CcoSrMrersepsounltdsinfrgomtotehmisissstiuodnys.fTrohmefMthOeCbufornribnigomofa2s5s-byeuarrn-oinldg
e. Puarticl btrieoegsehnaicrvseosutrecdesinis210.10123a,scdoertreersmpoinneddinwgitthotahtereyee-agrr2o0w1t3h.4m4Tohdeelr,e43suanltdintghfeMfMOCfnorf
s Articl This iOsC1f.0w2a7s.aOttCriwbuatsedthteonPsOepAaarnatdedSOinAtofrofomssfiolsOsiClf(uOeClfc)oamnbdunstoinon-f.oOssCilnOfCma(OyChnavf)e.
s
cce different origins, such as biogenic SOA (bio), biomass burning (bb), cooking,
A
n biofuelcombustion,brakeliningdust,naturalrubberintiredust,andothers.45
e
p
O
3 Results and discussion
3.1 Generalconditions
Similar meteorological patterns were recorded during the LT period (means of
25(cid:3)C,64%RH,andinsolationof239Wm(cid:1)2)andtheHTperiod(23(cid:3)C,59%RH,
230Wm(cid:1)2),whichwereseparatedbycoincidencebyarainyinter-period(26to27
August,MondayandTuesday),characterizedbyacleanatmosphere,lowinsola-
tion and temperature and high humidity (Fig. S2†). However, in the HT period
lowerwindspeedandhigherpressurewererecorded(1.7vs.2.1ms(cid:1)1,and1019
vs.1016hPa)asaconsequenceofananticyclonicepisodeleadingtoatmospheric
stagnation.
TheHYSPLITback-trajectoryanalysisevidencedthatbothperiodswerechar-
acterized by regional recirculation of air masses, with relatively short air mass
transport distances, although in the LT period a North-western direction pre-
vailed, whereas in the HT period this short transport had a European origin
(Fig.S3andS4†).
342 | FaradayDiscuss.,2016,189,337–359 Thisjournalis©TheRoyalSocietyofChemistry2016
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Paper FaradayDiscussions
MeantrafficowattheDiagonalAvenueincreased+37%fromtheLTtotheHT
period.TherushtraffichoursweremoreclearlyidentiedduringtheHTperiodat
6and16–18UTC,aswellasthemaximumtrafficintensity/windspeedratioat6
UTCand19UTC(Fig.S5†).
The separation of the LT and HT periods was done based on these results.
e. Hence, in the subsequent sections the inuence of traffic emissions on PM
M. enc composition and source contribution, with a special emphasis on OC, will be
54 Ad Lic investigated.
2:29:porte
3 1Un 3.2 PMx,Nandgasesconcentrations
2023.0 PM ,PM andPM concentrationsincreasedintheHTvs.theLTperiod+18,
7/n 10 2.5 1
nloaded on 2/2mons Attributio be+inp2ec4fisroeaoranedsdete,h+red3eu8ma%rciahn,xigrinmegstruptamehfficetpcimvrereaulsyxssi(uhmTraeuhb.moluerP1sM).aTxnhodinstiThnuecerdesdaevsaeeylio3spdSmuepeentteotmtohbfeetrmh(eoFrihgei.pg1hr)o,npoorneuesnscdueardey
wm Particlenumberconcentrationsincreased+22%fromtheLTtotheHTperiod
5. Doe Co for the N15–20 (the nucleation mode), and +41% and +49% for the N20–100 and
201ativ N100–500 (Table 1). N15–20 in the LT period showed intensive midday maxima,
ber Cre attributedtonucleationburstbypriorstudiesinBarcelona,17,46–48whereasthese
ma middaynucleationburstmaximawerelowerintheHTperiod(Fig.1).
eceder CO,NO andNOaverageconcentrationsincreasedfrom333mgm(cid:1)3,16mgm(cid:1)3
Dn 2
08 d u and3mgm(cid:1)3,respectively,fortheLTperiodto495mgm(cid:1)3,29mgm(cid:1)3and5mgm(cid:1)3
n se
on
blished e is lice Table1 AverageofdifferentparametersduringtheLTandtheHTperiodsanddifference
e. Puarticl in%
s Articl This LT HT Difference(%)
ces Meteorogicalconditionsandtraffic
Ac T ((cid:3)C) 25 23 (cid:1)6
en RH (%) 64 59 (cid:1)8
Op SR (Wm(cid:1)2) 239 230 (cid:1)4
WS (ms(cid:1)1) 2.1 1.7 (cid:1)20
P (hPa) 1016 1019 <1
Traffic (Vehiclesperh) 1663 2271 37
Gases
SO (mgm(cid:1)3) 2.8 3 7
2
NO (mgm(cid:1)3) 3 5 79
NO (mgm(cid:1)3) 16 29 81
2
O (mgm(cid:1)3) 80 85 6
3
CO (mgm(cid:1)3) 333 495 48
Aerosol
PM (mgm(cid:1)3) 20 24 18
10
PM (mgm(cid:1)3) 13 16 24
2.5
PM (mgm(cid:1)3) 10 14 38
1
N (#cm(cid:1)3) 7741 9822 27
15
N15–20 (#cm(cid:1)3) 1227 1493 22
N20–100 (#cm(cid:1)3) 4610 6511 41
N100–500 (#cm(cid:1)3) 1180 1756 49
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December nder a Cre wvfoaerrrieatht8ieo0nHmsTgbmeptew(cid:1)r3ieoe(dnLT(L+)T4a8an,nd+d88H51Tmagnpdemri+(cid:1)o7d39s(%H(a,Tvr)e.ersSapOgee2catcirovoneulcyne,dnTt3arabmtlgieomn1s)(cid:1).3dO)i,d3atcntorointbcusehtneotdwrattocilotehnaesr
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blished e is lice rinesteunltsiintyg. in a midday maximum coinciding with the maximum sea breeze
e. Puarticl
s Articl This 3W.3ithVthoelaetixlceeoprtgioanniocfcfoomrmpiocuancdids,isoprene,methylvinylketone(MVK)+MACR,
s
ce and monoterpenes, all VOCs presented higher mixing ratios during the HT
c
n A period. Aromatic hydrocarbons related to traffic emissions showed the highest
pe differences between the LT and HT periods, increasing from +78% to +85%
O
(C2,C3andC4-alkylbenzenes),+63%(benzene),and+52%(toluene).VOCswere
dominated by methanol (2.7 ppbv and 3.1 ppbv as averages for the LT and HT
periods,respectively),acetone(2.2ppbvand2.7ppbv),andaceticacid(0.9ppbv
and1.1ppbv).Isopreneaveragemixingratioswere0.16ppbvand0.12ppbvfor
the LT and HT periods, respectively, in the range measured during the winter
DAUREcampaigninBarcelona,49althoughmixingratiosofbenzeneandtoluene
wereslightlylowerthanthoseregisteredinDAURE;andhigherforacetone,acetic
acid,orMVK(Table2).
The traffic-related VOCs showed a marked daily cycle during the HT period,
peaking during traffic rush hours and following the same daily pattern as BC
(Fig.2).
Daily variability of the biogenic VOCs is related to temperature and solar
radiationcycles(Fig.2).Monoterpenesshowedamarkeddecreaseduringtheday
(Fig.2),attributedtodegradationbyO .50
3
OtherVOCs,suchasmethanoloracetoneincreasedbetween+14%to+21%in
theHTperiod(Table2).Thesecompoundsdidnotshowacleardiurnalpattern,
althoughhighermixingratioswererecordedduringthedaytime(Fig.S6†).The
344 | FaradayDiscuss.,2016,189,337–359 Thisjournalis©TheRoyalSocietyofChemistry2016
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Paper FaradayDiscussions
Table2 AverageofdifferentVOC mixingratiosduringtheLT andtheHTperiods and
differencein%.kratesaccordingtoCappellinetal.30
Chemicalformula Most krates LT HT Difference
m/z (protonatedions) probableVOCs (10(cid:1)9cm3s(cid:1)1) (ppbv) (ppbv) (%)
M. ence. 3437..003132 ((CCHH42OO)2H)H++ MFoertmhaicnoaclid 21..2929 20..73 30..11 (cid:1)1446
7/2023 12:29:54 An 3.0 Unported Lic 577667913199......000000446265995894 ((((((CCCCCC325446HHHHHH648686OO)OO)HH)))2HHH++)H++++ AAIMMBscceoVEeenpKKttzoirecen+nnaeeMeciAdCR 113233......99323262598 002000......1029006336 002100......1071002538 (cid:1)(cid:1)621321319420
nloaded on 2/2mons Attributio 9111130233.71570....60111980135172 (((((CCCCC78911HHH00HH81102)11H46))HH))HH+++++ TCCCMo234ol---unAAAeolllkkkntyyyeelllrbbbpeeeennnnzzzeeeesnnneee 22222.....244307578 00000.....000017201372 00000.....100023401044 (cid:1)8785184526
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mber a Cre highermixingratiosmeasuredduringtheHTperiodareprobablyrelatedtothe
eceder higheroxidationofBVOCsandAVOCs.
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e. Published article is lice (sTFuhilgep.hP3Ma)t.e1Itr(e2wl0aa%tsivd)e,oacmomminmpaotoensdiiutibmoynO(w9A%as(¼vaOenrMdys)1i(0m5%9il%)a,rnadinutdrrai5tne7g%(b4,o%rtheastpnhedectL5iT%vea)lyna)d,nfHdolTEloCpwee(r8ido%db)ys.
s Articl This LTTabalend3sHhTowpserthioedasv,earsagweeclolnacsetnhteradtiioffneroefntcheebdeifftweereenntbPoMthcopmerpioodnse.nTtsofobretttheer
s
ce assess the variation in the concentrations of the different PM components,
c
n A anormalizedconcentration(relativetoOA)wasused,andthedifferenceinthese
e
p normalizedconcentrationsisalsoshowninTable3.
O
AverageBCconcentrationsincreasedfrom1.0mgm(cid:1)3intheLTperiodto1.6
mgm(cid:1)3intheHTperiod.BCconcentrationsweremoredrivenbythetrafficcycles
thanbytheanticyclonedevelopmentduringtheHTperiod(Fig.2and3).Thus,
maximumBClevelsduringtrafficrushhoursreached4mgm(cid:1)3onmostdaysof
theHTperiod(andupto10mgm(cid:1)3),whereasduringtheLTperiodtheserarely
exceeded1mgm(cid:1)3,andthedailypatternwaslessmarkedorevenmissing(Fig.2
and3).
OAconcentrationsincreased+58%fromtheLTtotheHTperiod.Nitrateand
ammonium concentrations increased +99% and +72%, respectively, compa-
rabletotheBCconcentrations(+62%).Intermsofrelativeconcentrations(with
respecttoOA),theincreasewas+26%and+9%.Partofthisincreasemaybethe
result of the higher NO (+80%) and NH exhaust traffic emissions in the HT
x 3
period, resulting in the formation of ammonium nitrate. Nevertheless, and
giventhattheincreasefornitrateishigherthanthatforammonium,partofthe
nitratecouldpotentiallybeattributedtothepresenceoforganonitratesinthe
HT period. The sulphate concentrations increased +60%, similarly to the
referenceOAconcentration.Thehighersulphateconcentrationcouldberelated
Thisjournalis©TheRoyalSocietyofChemistry2016 FaradayDiscuss.,2016,189,337–359 | 345
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e. Published article is lice pcrmeoglolarmtrtteee(cid:1)sdd3p.VodIOnnivdCiedasteo;cdchtbhaoyenfd1rt0ihdgea:hrbtpeialooaxgltissseo.,ntTiphchleoeVtfOttueimCldlsl.ei)nSdioesuslUarcirnTorgCarrd.tehiaseptiLooTnnad(nStRdo)HtinhTeWpleemrfito(cid:1)ad2xsdi.siBvaiCnddecdothnbecyed1n0ot0trta0etdiiosnlainslseions
s Articl This
s
e
c
c
n A to an increase in the sulphate formation at a regional scale (note that SO2
e
p concentrations only increased +7% in Barcelona, Table 1) or to the accumula-
O
tion of pollutants over the Barcelona area. The intra-day variation of the
differentcomponentsvariedfromdaytoday,resultinginaveragedailypatterns
that were relatively at for sulphate and ammonium (Fig. 4). Nitrate and OA
concentrations partially followed the daily pattern observed for BC (Fig. 4),
especiallyduringtheHTperiod.
Somemineraldusttracerconcentrations,suchasAlandFe,increasedinthe
HTperiod+60%and+18%,whereasCadecreasedby(cid:1)27%,yieldingamineral
dustincreaseofonly+12%duringtheHT.
Sb and Sn concentrations, tracers of non-exhaust traffic emissions (mainly
frombrakepads),51increasedintheHTperiod+78%and+79%(Fig.5),similarly
to BC concentrations, hence conrming their road traffic origin. Conversely
concentrationsofseasalttracerssuchasNadecreasedby(cid:1)13%.
Also, Pb and Cd concentrations, industrial tracers, increased between +49%
and+151%duringtheHTperiod(Fig.5),probablyduetoanincreaseinindustrial
activity.
346 | FaradayDiscuss.,2016,189,337–359 Thisjournalis©TheRoyalSocietyofChemistry2016