Atmospheric Aerosol in Amazonia and Effects of Land Abuse

33 Pages·2013·2.19 MB·English

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4 Atmospheric aerosols in Amazonia and land
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1/ use change: from natural biogenic to biomass
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n 1 burning conditions
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e
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e PauloArtaxo,*aLucianaV.Rizzo,bJoelF.Brito,aHenriqueM.J.Barbosa,a
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ur Andrea Arana,a Elisa T. Sena,a Glauber G. Cirino,c Wanderlei Bastos,d
e f Scot T. Martine and Meinrat O. Andreaef
ut
stit
n
k I
nc Received9thApril2013,Accepted21stMay2013
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Pl DOI:10.1039/c3fd00052d
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a
M
y In thewet season, a large portion of theAmazonregion constitutes one of the most
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d pristinecontinentalareas,withverylowconcentrationsofatmospherictracegasesand
e
ad aerosol particles. However, land use change modifies the biosphere–atmosphere
o
nl interactions in such a way that key processes that maintain the functioning of
w
o
D Amazonia are substantially altered.This study presents a comparison between aerosol
13. properties observed at a preserved forest site in Central Amazonia (TT34 North of
0
er 2 Manaus) and at a heavily biomass burning impacted site in south-western Amazonia
mb (PVH,closetoPortoVelho).Amazonianaerosolswerecharacterizedindetail,including
pte aerosol size distributions, aerosol light absorption and scattering, optical depth and
e
S aerosol inorganic and organic composition, among other properties. The central
4
n 2 Amazonia site (TT34) showed low aerosol concentrations (PM2.5 of 1.3 (cid:1) 0.7 mg m(cid:3)3
d o and3.4(cid:1)2.0mgm(cid:3)3inthewetanddryseasons,respectively),withamedianparticle
e
sh numberconcentrationof220cm(cid:3)3inthewetseasonand2200cm(cid:3)3inthedryseason.
bli
u At the impacted site (PVH), aerosol loadings were one order of magnitude higher
P
(PM of 10.2 (cid:1) 9.0 mg m(cid:3)3 and 33.0 (cid:1) 36.0 mg m(cid:3)3 in the wet and dry seasons,
2.5
respectively).Theaerosolnumberconcentrationattheimpactedsiterangedfrom680
cm(cid:3)3 in the wet season up to 20000 cm(cid:3)3 in the dry season. An aerosol chemical
speciation monitor (ACSM) was deployed in 2013 at both sites, and it shows that
aInstituteofPhysics,UniversityofSa~oPaulo,RuadoMata~o,TravessaR,187.CEP05508-090,Sa~oPaulo,S.P.,
Brazil.E-mail:[email protected]
bDepartmentofEarthandExactSciences,InstituteofEnvironmental,ChemicalandPharmaceuticsSciences,
FederalUniversityofSa~oPaulo,UNIFESP-CampusDiadema,RuaProf.ArturRiedel,275,CEP09972-270,
Diadema–Sa~oPaulo,Brazil
cINPA-InstitutoNacionaldePesquisasdaAmazˆonia,Av.Andr´eArau´jo,2.936–CEP69067-375,Manaus,
Brazil
dLaborat´oriodeBiogeoqu´ımicaAmbientalWolfgangC.Pfeiffer,UniversidadeFederaldeRondˆonia-UNIR,
Rondˆonia,Brazil
eSchool of Engineering and Applied Sciences and Department of Earth and Planetary Sciences, Harvard
University,29OxfordSt.,PierceHall,Cambridge,Massachusetts,02138,USA
fBiogeochemistryDepartment,MaxPlanckInstituteforChemistry,P.O.Box3060,55020Mainz,Germany
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organicaerosolaccountto81%tothenon-refractoryPM1aerosolloadingatTT34,while
biomassburningaerosolsatPVHshowsa93%contentoforganicparticles.Threeyearsof
filter-basedelementalcompositionmeasurementsshowsthatsulphateattheimpacted
0. sitedecreases,onaverage,from12%ofPM2.5massduringthewetseasonto5%inthe
5 dry season. This result corroborates the ACSM finding that the biomass burning
5:
3:0 contributedoverwhelminglytotheorganicfinemodeaerosolduringthedryseasonin
4 1 this region. Aerosol light scattering and absorption coefficients at the TT34 site were
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20 lowduringthewetseason,increasingbyafactorof5,approximately,inthedryseason
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0 duetolongrangetransportofbiomassburningaerosolsreachingtheforestsiteinthe
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n 1 dryseason.Aerosolsinglescatteringalbedo(SSA)rangedfrom0.84inthewetseason
e o up to 0.91 in the dry. At the PVH site, aerosol scattering coefficients were 3–5 times
mi
e higher in comparison to the TT34 site, an indication of strong regional background
h
C pollution, even in the wet season. Aerosol absorption coefficients at PVH were about
ur
e f 1.4timeshigherthanattheforestsite.Ground-basedSSAatPVHwasaround0.92year
nstitut rboioumnda,ssshbouwrnininggthaeerdoosmolisn.aRnecmeootfescsaetntesirninggoabesreorsvoaltipoanrsticflreosmovseixraAbEsRoOrpNtiEoTn,seitveesnafnodr
k I
c from MODIS since 1999, provide a regional and temporal overview. Aerosol Optical
n
a
Pl Depth (AOD) at 550 nm of less than 0.1 is characteristic of natural conditions over
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Ma Amazonia. At the perturbed PVH site, AOD550 values greater than 4 were frequently
y observed in the dry season. Combined analysis of MODIS and CERES showed that the
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d mean direct radiative forcing of aerosols at the top of the atmosphere (TOA) during
e
oad the biomass burning season was (cid:3)5.6 (cid:1) 1.7 W m(cid:3)2, averaged over whole Amazon
nl
w Basin.ForhighAOD(largerthan1)themaximumdailydirectaerosolradiativeforcing
Do at the TOA was as high as (cid:3)20 W m(cid:3)2 locally. This change in the radiation balance
13. caused increases in the diffuse radiation flux, with an increase of Net Ecosystem
0
er 2 Exchange (NEE) of 18–29% for high AOD. From this analysis, it is clear that land use
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m change in Amazonia shows alterations of many atmospheric properties, and these
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pt changesareaffectingthefunctioningoftheAmazonianecosysteminsignificantways.
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d o 1 Introduction
e
h
s
bli Amazonia is an excellent laboratory to study atmospheric processes that are
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P characteristic of natural conditions, as they existed prior to the impact of
industrialization on the regional and global atmosphere.1 The strong coupling
betweentheatmosphereandtheforestcanbeseenascharacteristicofconditions
beforelarge-scaledeforestationchangedlanduseinEurope,NorthAmerica,and
otherregions.Furthermore,theregionsustainedastronghydrologicalcyclethat
is maintained by large water vapour emissions from the forest as well as cloud
condensationnuclei(CCN)producedfromforestemissions,2,3andoneimportant
location of deep tropical convection. However, the vast forest–river system of
Amazonia is changing due to expansion and intensication of agriculture,
logging, and urban footprints.4 Indications that the hydrological cycle in Ama-
zoniaisbeingintensiedinthelasttwodecadesaddakeyissueinthechangesin
Amazonia.5Recentlytwostrongdroughtsin2005and2010havereceivedatten-
tion,6,7aspotentialindicators ofincreaseinclimate extremesinAmazonia that
feedsbackintotheforestcarbonprocessing.8
The Brazilian Amazonextends over about 5.5million km2, correspondingto
61%oftheareaofthecountryofBrazil.Deforestationhaschangedabout18%of
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theoriginalforestarea,mostlyinsouthernandwesternAmazonia.9Theforests
and soils of the Amazon basin also store a large amount of organic carbon
(around200PgC),whichmaypotentiallybereleasedtotheatmospherethrough
0. foresttopastureconversionorloggingorbecauseofbiomechanges.10Theriver
5:5 systemisresponsibleforabout20%oftheworld'sfreshwaterdischarge,andthis
3:0 forest–riversystemisvulnerabletoclimatechange.11Inaddition,responsesand
4 1 feedbacksofthisbiometochangesinclimateandland-usecouldaffectregional
1
20 andglobalclimate.12,13
01/ Human activities in Amazonia over the last 50 years have had a signicant
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n 1 impact on a considerable part of the region, especially along the southern
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e perimeter.14ArecentsteepdeclineinannualdeforestationratesintheBrazilian
emi Amazonfrom27800km2yr(cid:3)1in2004to4660km2yr(cid:3)1in2012isrecordedinthe
h
C time series shown in Fig. 1, as measured by the PRODES (Projeto de Monitor-
e fur amentodoDesorestamentonaAmazˆoniaLegal)programfromINPE(TheBra-
stitut zilian National Institute for Space Research) for the Brazilian Amazon. The
n reductionfrom2004to2012observedinFig.1isanimpressiveachievement,but
k I
c there are questions if these relatively recent low deforestation rates can be
n
a
Pl maintainedoverthenextdecades,12becauseofsocio-economicpressuresaswell
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a as a result of a changing global climate.13,15 The dominant factors of public
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y policies,climate,economicissues,andsoforththatsuccessfullycontributedto
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d thereductionofdeforestationratesinrecentyearshavenotbeenfullydissected.
e
d
oa There is also increased uncertainty over the sensitivity of carbon storage in the
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ow tropics to climate warming, increasing atmospheric CO2 concentrations, and
D tropicaltemperatureanomalies.16
3.
1 The large carbon stock of Amazonia is sensitive to processes that alter
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2
er precipitationandradiation.Thetwolargedroughtsof2005and20106,7released
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m largeamountsofcarbontotheatmosphere,indicatingahighsensitivityofthis
e
pt system to altered conditions. High concentrations of aerosol particles in the
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4 atmosphereduetobiomassburningdecreasetheamountofphotosynthetically
n 2 radiationtovaryingcanopylevels,affectingsensibleandlatentheatuxesatthe
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Fig.1 Annualdeforestation ratesinthe Brazilian Amazoniafrom1977to2012measuredbythe
PRODES(ProjetodeMonitoramentodoDesflorestamentonaAmazoˆniaLegal)programfromINPE(The
BrazilianNationalInstituteforSpaceResearch).
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surface.17Thechangesinradiationuxduetoaerosolandcloudsandintheratio
of diffuse to direct radiation have a large impact on Net Ecosystem Exchange
(NEE), with an enhancement in carbon uptake of 18–29%18 for AOD (Aerosol
0. Optical Depth) changes from 0.1 to 1. At the Tapajos National Forest (FLONA-
5:5 Tapajos,Santarem-PA),anincreaseincarbonuptakewasmostlyattributedtothe
3:0 increaseddiffuseradiationinthesub-canopylayer.19Ontheotherhand,forvery
4 1 large aerosol loadings (AOD > 2 at 550 nm), NEE decreases signicantly, indi-
1
20 catingthelargeimpactofaerosolsonecosystemfunctioning.18Studiesofeffects
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0 of aerosol particles on changes in cloud properties and precipitation were the
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n 1 focusofseveralpreviousstudiesinAmazonia.20–25
o
e The Large-scale Biosphere-Atmosphere Experiment in Amazonia (LBA) is a
mi
e long term multinational, interdisciplinary research program, led by Brazil
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C throughitsMinistryofScienceandTechnologyandoperatedbyINPA(TheBra-
ur
e f zilian National Institute for Amazonian Research.8 The focus of LBA is to
nstitut uhnowderosnta-gnodinhgowchAamngaezsoniinafluanndctiuosnesaasndarcelgimionataeleanretitayffinectthinegEathrtehAsymstaezmonainand
ck I ecosystem.11 LBA seeks to supply a scientic basis for addressing the sustain-
n
Pla ability of development in the region through an interdisciplinary scientic
ax agenda,whichspanstheeldsofphysicalclimate,hydrology,biogeochemistry,
M
y ecology,economics,andhumandimensionsofland-usechange.Theintegrated
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d understanding of these complex issues requires understanding its underlying
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oa spatialandtemporalheterogeneity,asrelatedtoclimate,rivers,soils,vegetation,
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w andland-usedriversacrosstheBasin.TheAmazonforestisheterogeneousand
o
D complex,anditisessentialtohaveacomprehensivescienticunderstandingof
13. thefeedbacks amongclimate, atmospheric composition, land-use, re,and the
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er socio-economicdrivers.12AtmosphericstudiesovertheAmazonianBasinstarted
mb in the 1980's with the Brushre experiment,26 and the ABLE-2A (Amazon
e
pt BoundaryLayerExperiment2A)and2Bcampaigns,27–29followedbyseveralinte-
e
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4 grated experiments, such as LBA-EUSTACH,30 LBA-CLAIRE,31 AMAZE-08,32 and
2
n others. In general, these studies addressed one or both topics: (1) biomass
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ed burning emissions and effects and (2) emissions and reactivity of natural trace
h
blis gasesandbiogenicparticles.
Pu In the Amazon, res are almost exclusively caused by humans, and occur-
rencesofnaturalresarerareeventsbecauseofthehighprecipitationrateseven
inthedryseason.33,34Fireshavebeenroutinelyusedasaclearingtoolduringthe
dryseason,inpreparationforagriculturaleldsaeraforestedpatchhasbeen
slashed down, or conversion from crops to pasture for cattle grazing. As the
amountofprecipitationishigh,makingitdifficulttoburntheforest,farmerscut
down the forest in the end of the wet season (May–June) and let the wood and
slashdryuntilSeptemberinordertoclearthelandforagriculturalorpastureuse.
Everyyearfrom September toNovember, largeamounts ofsmokecan beeasily
observedusingremotesensingobservations,35mainlyintheregioncalledthe“arc
ofdeforestation”in thesouthern partofAmazonia, a regionwhere the tropical
rainforestisclosetomoredenselypopulatedareas.36Thesmokeplumeextends
over millions of km2, ultimately covering large areas of South America, with
signicant impacts extending far from the Amazonian region.37–39 In particular,
the effects of biomass-burning aerosol particles on human health, such as
increasedincidencesofmorbidity,mortality,andasthma,aresignicantinthe
regionoftheso-calleddeforestationarc.40Manystudiesinthelastfewyearshave
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analysed the role of aerosol particles in cloud development and suppression in
Amazonia,21,22,41 showing that as pristine conditions have quite low CCN
concentrations and high water vapour, any increase in CCN numbers can
0. signicantlyaffectclouddevelopmentandinvigoration.42
5:5 Aerosolmassspectrometry isapowerfultoolforcharacterizingaerosolsand
3:0 theiratmosphericprocessing.InAMAZE-08(AmazonianAerosolCharacterization
4 1 Experiment-2008), an Aerodyne high-resolution time-of-ight aerosol mass
1
20 spectrometer(HR-ToF-AMS)wasusedforthersttimeinSouthAmerica;itwas
1/
0 appliedtothecharacterizationofAmazonianorganicaerosolsatatimeresolution
5/
n 1 ofbetterthan5min.24,32,43PriortotheAMAZE-08campaign,thecontributionof
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e primarybiogenicaerosolstotheaccumulationmodewaslesswellcharacterized
mi
e than that to the coarse mode.44,45 Given that Amazonian aerosols have primary
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C and secondary contributions, marker signals were sought in the collected AMS
ur
e f data.TheresultsshowedthatprimaryaerosolsinAmazoniaconsistofcarbohy-
stitut drates,waxes,etc.frombiogenicdebris,whereassecondaryaerosolsareoxidation
n productsofisoprene,terpenes,andotherVOCs.Furthermore,themassspectral
ck I datawerealsoabletoidentifytimeperiodsinuencedbyAfricanaerosoladvec-
n
a
Pl tion.46,47 During clean periods, the mass spectra showed the submicron aerosol
x
a composition to be dominated by 90% organic matter and 10% sulphate, at
M
y averagemassconcentrationsof0.6mgm(cid:3)3.Theoxygen-to-carbon(O:C)ratiowas
b
d 0.42.WheninuencedbyAfricanemissions,theaveragecompositionchangedto
e
oad 75%organicand25%sulphate,withmassconcentrationof0.9mgm(cid:3)3andO:C
nl
w of0.49.ThestudyconcludedthatsubmicronaerosolinthewetseasonofAma-
o
D zonia was largely dominated by secondary organic aerosol related to gaseous
13. BVOC emissions from the forest ora. Furthermore, P¨ohlker et al.,48 added the
0
er 2 nding that potassium is present in more than 90% of particles larger than
b
m 20 nm, again showing the importance of biogenic forest emissions on SOA
e
pt formation in the Amazonian atmosphere, and the strong coupling between the
e
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4 biologyoftheforestandatmosphericcomposition.24
2
n InpristineregionsofAmazonia,thebiologyoftheforesthascloselinkswith
o
ed atmospheric aerosol and trace gases.24,32,44,48,49 Ground based microorganisms
h
blis could play a role in cloud process in Amazonia,50 since strong convection can
Pu transportbiogenicparticlestothealtitudesofcloudformation.Fungiandother
primary biological particles also play a role in aerosol organic components in
Amazonia.45 Biomass burning and land use change interfere with the natural
cycles and feedbacks. To better understand the effects of these changes, it is
important to physically and chemically characterize the aerosol population in
Amazonia, aiming to identify trends over time and landscape. Forest VOCs
emissions51–53 through atmospheric photo-oxidation chemistry produce most of
thesecondaryorganicaerosol(SOA)inthenemodeoverAmazonia.54–56Primary
biogenic aerosols dominate the coarse mode particles showing the very close
relationshipbetweenemissionsfromthevegetationandaerosolconcentrations
andcompositioninAmazonia.49,57–59
Thispaperpresentsaperspectiveandanalysisoftheeffectsoflandusechange
onatmosphericpropertiesinAmazoniaonalong-termbasis.Samplingoftrace
gases and aerosols was performed for 3 years continuously in two locations: a
preservedforestsiteincentralAmazonia(TT34)andabiomassburningimpacted
siteinSouthwesternAmazonia(PVH),wherelandusechangehasbeenastrong
processsincethe1980s.Tracegasesandaerosolpropertieswereanalysedatthese
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1 Fig.2 MapofAmazoniashowingthelocationsofthetwoatmosphericsamplingsitesatPortoVelho
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er 2 (PVH),andCentralAmazonia(TT34)(yellowmarkers).
b
m
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ept twositesfrom2008to2012.Largeinterannualvariabilityinclimaticconditions
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4 in Amazonia makes long term studies necessary. Also, the effects of changing
2
on aerosol loading in the atmosphere were analysed in two aspects: changes in
ed radiativeforcingaswellaschangesincarbonuptakeduetoincreasesindiffuse
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bli radiationassociatedwithincreasedaerosolloading.
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2 Experimental
2.1 Samplingsites
Amazonia is a continental scale region, with most of the land use change
occurring in the southern part of the Basin (Fig. 2). The in situ trace gas and
aerosolmeasurementsreportedhereweretakenattwosites:oneatapreserved
forestarea incentral Amazonia (namedTT34 sitehereaer), and the otherat a
biomass burning impacted area in south western Amazonia (named PVH
hereaer).
Therstsite(TT34)isrepresentativeofnear-pristineconditionsduringthewet
season.Inthisarea,fromthepointofviewofaerosolproperties,thewetseason
corresponds to the period Jan–Jun, whereas the dry season corresponds to Jul–
Dec.60 This forest site is located 60 km northwest to Manaus urban area, a fast
developing city with a population of about 2 million people. Observations were
taken at the TT34 tower located at the ZF2 Ecological Station (2.59(cid:4)S, 60.21(cid:4)W,
110 m asl), where aerosols and trace gases were measured almost continuously
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fromFebruary2008toJune2011.ThissiteiswithintheINPA(BrazilianNational
Institute for Amazonian Research) Cuieiras forest reserve. No biomass burning
occursinthereservationorclosetothesite.Mostofthetime,theprevailingtrade
5:50. wmienadssurbelmowentovtoewrevra.sHtoewxpevaenrs,eassowfillinbteacfturttrhoepricdailscfuosrseesdt,bthefeosrieterweaacshainffgectthede
3:0 by regional transport of pollutants, most of it from long-range transported
1
4 biomassburningemissions.Allmeasurementsweretakenunderdryconditions
1
20 (RH 30–40%) by use of an automatic diffusion dryer in the sampling line.61 An
01/ inletwith50%aerodynamiccut-offof7mmwasusedforsampling.Inletlinesran
5/
n 1 fromthemeasurementlevel(39magl,about10mabovethecanopyheight)toan
o
e air-conditioned container at ground level. Housing for the researchers and a
mi
e dieselgeneratorthatprovidedthepowersupplywerelocatedrespectively0.33km
h
C and0.72kmtothewestofthesamplingsite(downwind).Adetaileddescriptionof
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e f the ZF2 TT34 tower measurement site and surrounding area can be found in
stitut Martinetal.32
n Thesecondsite(PVH)islocatednearPortoVelhocity,thecapitalofthestateof
ck I Rondˆonia. The sampling site was located in an area of mixed forest and open
n
a
Pl vegetation in an ecological reservation about 5 km NE (upwind) from the city
ax (8.69(cid:4)S,63.87(cid:4)W).ThewholeregionofRondˆoniahasbeenundertheeffectofland
M
y use change since the 1980s. Most of the measurements were taken under rela-
b
d tivelydryconditions(RH<50%)byuseofdiffusiondryers.Aninlethavinga50%
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oad aerodynamic cut-off of 10 mm was used for sampling. Inlet lines ran from the
nl
w measurement level (5 m agl) to an air-conditioned house. This site represents
o
D largelandusechangesandassociatedregionalbiomassburningascharacteristic
3.
1 ofAmazoniaincontactwithhumaninterferences.AtthePVHsite,thedryseason
0
2
er isfromJunetoDecember,andthewetseasonfromJanuarytoMay.
b
m Addingtothegroundbasedinsitumeasurements,remotesensedatafromthe
e
pt NASA/AERONET sunphotometers network and from the MODIS satellite sensor
e
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4 werealsoanalysed.ReportedAODobservationsfromAERONETarelevel2.0,and
2
n data were taken from two sites in southern Amazonia (same region as the PVH
o
ed site):AbracosHill(10S;62W)andJi-Parana-SE(10S;61W),andfromtwositesin
h
blis central Amazonia (same forest reservation as the TT34 site): Balbina (1S; 59W),
Pu andManaus-EMBRAPA(2S;59W).AODobservationsfromMODISwereintegrated
foranareawith40kmradiusaroundtheAERONETmeasurementsites.MODIS
andAERONETdatabetween1999and2012areanalysedinthispaper.
2.2 Instrumentation
Measurements of aerosol particle number size distribution, number concentra-
tion, mass and elemental composition were made. Two ne mode mobility
particle size spectrometers (10–500 nm) were used interchangeably: a TSI-3080
SMPS (Scanning Mobility Particle Sizer) and a custom-made SMPS designed at
Lund University according to EUSAAR (European Supersites for Atmospheric
Aerosol Research) standards.62 Particle number concentrations were measured
usingcondensationparticlecounters(TSICPCmodels3010,3785,3772).Stacked
FilterUnits(SFU)ttedwithPM inletswereusedtocollectnemode(D <2.0
10 p
mm) and coarse mode (2.0 < D < 10.0 mm) aerosols, with integrating periods
p
rangingfrom2to5daysdependingontheaerosolloading.Fineandcoarsemode
Nucleporelterswereanalysedforparticulatemass,followingthemeasurement
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ck I Fig.3 Timeseriesoffine(PM2.5)andcoarsemodeaerosolmassconcentrationsatthecentralAmazonia
n
a TT34forestsitefrom2008to2012.
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x
a
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by protocol of the US Environmental Protection Agency for weighing lters, in a
ded controlled atmosphere at 35% RH and 20 (cid:4)C. Equivalent black carbon concen-
a
nlo tration(BCe)wasmeasuredintheneandcoarsemodefromNucleporelters,
ow using an optical reectance method calibrated with Monarch black carbon
D
3. standards. About 25 trace elements were measured using X-ray uorescence
1
0 analysis with a Pan Analytical Epsilon 5 X-ray spectrometer. Precision for
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er elementalcompositionwas10%formostofthemeasuredelements,increasingto
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e 20% for elements close to the detection limits. Ozone mixing ratios were
pt
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Fig.4 TimeseriesofequivalentblackcarboninfineandcoarsemodeaerosolsattheTT34forestsite
from2008to2012.TheincreaseinfinemodeBCconcentrationsinthedryseasonisduetolong-range
transportofbiomassburningaerosol.
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measured with Thermo Environment 49i ozone monitors, while CO was
measuredwithaPicarroanalysermodelG2301.Thezeropointoftheinstruments
wascheckedonaweeklybasis.
0. An Aerodyne Research Aerosol Chemical Speciation Monitor (ACSM)63 was
5:5 deployedattheTT34(centralAmazonia)andPVH(PortoVelho)sites.TheACSM
3:0 isacompactversionoftheAerodyne'sAerosolMassSpectrometer,64designedto
1
4 characterizeandmonitor,underroutinestableoperation,themassandchemical
1
20 composition of non-refractory submicron particulate matter. Under ambient
1/
0 conditions, mass concentrations of particulate organics, sulphate, nitrate,
n 15/ ammonium,andchloridewereobtainedwithadetectionlimit<0.2mgm(cid:3)3for
o
e 30minofsignalaveraging.Duetothehighconcentrationoforganicsrelativeto
mi
e sulphate, nitrate, chloride and ammonium, especially when sampling strongly
h
C biomass burning impacted air masses, corrections to the instrument chemical
ur
e f assignmentwereperformed.65,66
nstitut inteAgerraotsinolgpnaertpichleeloscmaettteerrisng(TcSoIe-3ffi5c6i3enatnsdweErceomteechasuAruerdoruasi3n0g0t0h)r.6e7e-Twhaeveilnenstgrtuh-
nck I mentswerecalibratedperiodicallyusinglteredairandCO2.Datawerecorrected
a
Pl
x
a
M
y Table1 Averageaerosolelementalconcentrations(2008–2012)attheTT34forestsitefordryandwet
b
aded eseleamsoennst.sT.hTehetacbolneciennclturadteiosnasvearraegnegsfmo(cid:3)r3p.aTrhtiecuulnatceermtaainttteyri(sPtMhe),setqanudivaarldendtebvliaactkiocnaarbnodnN(BisCteh)eanndumtrabceer
o
nl ofsamplesthattheelementwasmeasuredabovedetectionlimits.Finemodereferstoaerosolaero-
ow dynamicdiametersupto2.0mmandcoarsemodefrom2.0mmto10mm
D
3.
1 DrySeason WetSeason
0
2
ber FineMode N CoarseMode N FineMode N CoarseMode N
m
e
ept PM 3400(cid:1)2000 94 4425(cid:1)2429 94 1300(cid:1)700 104 5000(cid:1)2000 104
4 S BCe 235(cid:1)156 94 41(cid:1)22 94 98(cid:1)83 104 47(cid:1)20 104
n 2 Na 20(cid:1)18 64 28.(cid:1)25 66 10.0(cid:1)8.3 65 26(cid:1)24 79
d o Mg 4.6(cid:1)6.2 84 8.1(cid:1)8.8 92 10(cid:1)13 87 13(cid:1)14 94
he Al 18(cid:1)20 96 25(cid:1)25 97 42(cid:1)64 106 44(cid:1)63 100
s
bli Si 27(cid:1)34 95 37(cid:1)37 97 77(cid:1)116 107 85(cid:1)122 103
Pu P 4.8(cid:1)3.3 97 17(cid:1)12 96 3.0(cid:1)1.9 110 23.0(cid:1)8.0 110
S 175(cid:1)114 97 38(cid:1)24 97 74(cid:1)45 110 35(cid:1)16 110
Cl 2.0(cid:1)1.9 46 20(cid:1)25 96 1.7(cid:1)1.7 70 46(cid:1)57 110
K 74(cid:1)66 97 54(cid:1)30 97 26(cid:1)21 110 68(cid:1)22 110
Ca 4.9(cid:1)7.0 97 13(cid:1)22 97 6.1(cid:1)7.6 110 14(cid:1)14 110
Ti 1.5(cid:1)1.4 82 2.7(cid:1)2.5 93 2.8(cid:1)4.1 100 3.4(cid:1)4.5 100
V 0.2(cid:1)0.3 73 0.2(cid:1)0.3 63 0.2(cid:1)0.4 73 0.1(cid:1)0.1 67
Cr 0.3(cid:1)0.4 52 0.3(cid:1)0.2 76 0.2(cid:1)0.2 67 0.2(cid:1)0.2 94
Mn 0.3(cid:1)0.3 83 0.4(cid:1)0.4 84 0.4(cid:1)0.5 92 0.6(cid:1)0.6 97
Fe 12(cid:1)12 97 21(cid:1)18 97 20(cid:1)27 105 23(cid:1)31 110
Ni 0.2(cid:1)0.2 74 0.1(cid:1)0.1 69 0.2(cid:1)0.3 88 0.1(cid:1)0.1 68
Cu 1.3(cid:1)4.5 75 0.3(cid:1)0.9 86 0.2(cid:1)0.5 89 0.2(cid:1)0.2 96
Zn 1.6(cid:1)3.6 97 1.0(cid:1)1.9 92 0.4(cid:1)0.4 103 0.6(cid:1)0.5 110
Br 0.7(cid:1)0.5 83 0.3(cid:1)0.3 75 0.3(cid:1)0.4 81 0.3(cid:1)0.4 84
Rb 0.2(cid:1)0.3 25 0.2(cid:1)0.2 26 0.2(cid:1)0.2 39 0.2(cid:1)0.1 52
Sr 1.3(cid:1)1.1 15 0.6(cid:1)0.8 7 1.1(cid:1)1.2 14 0.5(cid:1)0.5 14
Sb 1.5(cid:1)1.2 9 1.1(cid:1)1.1 13 1.4(cid:1)0.9 15 1.0(cid:1)0.9 14
Pb 0.4(cid:1)0.5 78 0.3(cid:1)0.5 63 0.4(cid:1)0.5 83 0.4(cid:1)0.6 75
BC/PM(%) 6.9(cid:1)7.8 94 0.9(cid:1)0.9 94 7.5(cid:1)11.8 104 0.9(cid:1)1.0 104
e
SO4/PM(%) 15.4(cid:1)17.1 94 2.6(cid:1)2.9 94 17.1(cid:1)19.3 104 2.1(cid:1)2.4 104
ThisjournalisªTheRoyalSocietyofChemistry2013 FaradayDiscuss.,2013,165,203–235 | 211
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FaradayDiscussions Paper
0.
5
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0
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2
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nc Fig.5 TimeseriesoffineandcoarsemodeaerosolmassconcentrationsatthePVHanthropogenic
a
Pl impactedsite,from2009to2012.
x
a
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y
b
d
e
d
a
o
nl
w
o
D
3.
1
0
2
er
b
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4
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bli
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Fig.6 AverageaerosolequivalentblackcarbonBCeconcentrationsforfineandcoarsemodeatthe
PVHimpactedsitefrom2009to2012.
for truncation errors.68 Aerosol particle absorption was measured using MAAP
absorption photometers (MultiAngle Absorption Photometry – Thermo Inc.,
Model5012).69TheMAAPreportsequivalentblackcarbon(BC )concentrationsat
e
637 nm, which were converted to absorption coefficients assuming a mass
absorptioncoefficientof6.6m2g(cid:3)1.A5%correctionwasappliedtothedatato
account for an adjustment of wavelength. Pressure and temperature measured
inside the nephelometer were used for adjusting scattering and absorption
coefficientsto1013mbarand0(cid:4)C.
212 | FaradayDiscuss.,2013,165,203–235 ThisjournalisªTheRoyalSocietyofChemistry2013