Antarctic new particle formation from continental biogenic precursors

54 Pages·2012·8.07 MB·English

Atmos.Chem.Phys.Discuss.,12,32741–32794,2012 Atmospheric Dis
www.atmos-chem-phys-discuss.net/12/32741/2012/ Chemistry c ACPD
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doi:10.5194/acpd-12-32741-2012 and Physics ss
©Author(s)2012.CCAttribution3.0License. Discussions io 12,32741–32794,2012
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Thisdiscussionpaperis/hasbeenunderreviewforthejournalAtmosphericChemistry e Antarctic new
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andPhysics(ACP).PleaserefertothecorrespondingfinalpaperinACPifavailable. particle formation
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Antarctic new particle formation from is biogenic precursors
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continental biogenic precursors io
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E.-M. Kyro¨1, V.-M. Kerminen1, A. Virkkula1,2, M. Dal Maso1,3, J. Parshintsev4, er TitlePage
J. Ru´ız-Jimenez4, L. Forsstro¨m5, H. E. Manninen1, M.-L. Riekkola4, P. Heinonen6, | Abstract Introduction
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and M. Kulmala
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1DepartmentofPhysics,UniversityofHelsinki,Helsinki,Finland cu
2AirQualityResearch,FinnishMeteorologicalInstitute,Helsinki,Finland ss Tables Figures
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3DepartmentofPhysics,TampereUniversityofTechnology,Tampere,Finland n
4DepartmentofChemistry,UniversityofHelsinki,Helsinki,Finland Pa J I
5DepartmentofBiologicalandEnvironmentalSciences,UniversityofHelsinki,Helsinki, pe
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Finland
6FINNARPlogistics,FinnishMeteorologicalInstitute,Helsinki,Finland |
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Received:6November2012–Accepted:5December2012–Published:19December2012 is
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Correspondenceto:E.-M.Kyro¨ (ella-maria.kyro@helsinki.fi) s
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PublishedbyCopernicusPublicationsonbehalfoftheEuropeanGeosciencesUnion. n Printer-friendlyVersion
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Abstract D
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Over Antarctica, aerosol particles originate almost entirely from marine areas, with s
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minor contribution from long-range transported dust or anthropogenic material. The ion 12,32741–32794,2012
Antarctic continent itself, unlike all other continental areas, has been thought to be P
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5 practically free of aerosol sources. Here we present evidence of local aerosol produc- er Antarctic new
tion associated with melt-water ponds in the continental Antarctica. We show that in particle formation
airmassespassingsuchponds,newaerosolparticlesareefficientlyformedandthese | from continental
particles grow up to sizes where they may act as cloud condensation nuclei (CCN). Dis biogenic precursors
The precursor vapours responsible for aerosol formation and growth originate very c
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likely from highly abundant cyanobacteria Nostoc commune (Vaucher) communities of ss E.-M.Kyro¨ etal.
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localponds.Thisisthefirsttimewhenfreshwatervegetationhasbeenidentifiedasan n
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aerosol precursor source. The influence of the new source on clouds and climate may a
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increaseinfutureAntarctica,andpossiblyelsewhereundergoingacceleratingsummer e TitlePage
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melting of semi-permanent snow cover.
| Abstract Introduction
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1 Introduction c
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Antarctica is experiencing dramatic changes especially in the Peninsula and west- io
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ern part but also in the coastal areas around the whole continent (Chen et al., 2009; Pa J I
Pritchard et al., 2009). These are also the areas with most of the continents exposed p
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ground and high mountains. Especially the spring temperatures have been increasing r J I
in these areas (Steig et al., 2009; Schneider et al., 2012) followed by increasing ice |
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massloss(Pritchardetal.,2009)andiceshelfcollapses(Rignotetal.,2004).Inspring D
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and summer, intense solar radiation melts snow and ice around the mountains as well c FullScreen/Esc
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as areas with exposed ground and blue ice into ponds and lakes. The increasing tem- ss
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perature decreases the overall surface albedo in these areas by enhancing the snow n Printer-friendlyVersion
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25 and ice melt (Hall, 2004). a
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TheAntarcticclimatesystemiscoupledtightlywithaerosolparticlesviaglobalwarm- D
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ing and associated feedback processes involving aerosol-cloud interactions. The most c ACPD
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studied aerosol type in this respect is the natural sulphate aerosol originating from s
oceanic dimethyl sulphide (DMS) emissions affected mainly by ocean biochemistry ion 12,32741–32794,2012
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5 and wind speed (Korhonen et al., 2008). Another prominent aerosol type over Antarc- ap
tica is sea salt (Shaw, 1988; Hara et al., 2011; Weller et al., 2011), the concentration e Antarctic new
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andpropertiesofwhichareinfluencedbytheseaiceextent,windspeedandprobably particle formation
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alsobytheseawatertemperature(Struthersetal.,2011).Inadditiontothesetwonat- from continental
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uralaerosoltypes,smallamountsofdustandanthropogenicpollution-derivedparticles is biogenic precursors
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areoccasionallylong-rangetransportedtoAntarctica(Shaw,1988;Fiebigetal.,2009). u
10 The Antarctic continent has been thought to be a weak source of primary aerosol par- ssio E.-M.Kyro¨ etal.
ticles, mainly dust as well as pollen and bacteria (Gonza´les-Toril et al., 2009), and n
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a negligible source of precursors for secondary aerosol particles. a
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Here, we investigate secondary aerosol formation observed during the FINNARP r
2009 expedition at the Finnish Antarctic Research Station Aboa. Previous studies
15 | Abstract Introduction
have shown that secondary Antarctic aerosols originate from oceanic DMS emissions
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(O’Dowd et al., 1997; Davis et al., 1998; Asmi et al., 2010; Yu and Luo, 2010), long- is Conclusions References
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range transport (Ito, 1993; Fiebig et al., 2009; Hara et al., 2011), or from intrusion of u
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upper tropospheric air into the boundary layer (Virkkula et al., 2009). Also local an- io
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20 thropogenicsourceshavebeenlinkedwithnewparticleformation(NPF)incontinental Pa J I
Antarctica (Park et al., 2004). At Aboa, the particle formation takes mostly place in p
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airmasses coming along the coastline (Koponen et al., 2003) or intruding from higher r J I
altitude(Virkkulaetal.,2009).Observationsofgrowthofthesmallestclusterionssug- |
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gestthatthenucleationcanoccurevenintheboundarylayer(Asmietal.,2010).Ithas D
alsobeensuggestedthatsecondaryorganicmatter,havingasignificantcontributionin is
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theAitkenandaccumulationmodes,couldcontributetothegrowthofaerosolparticles s
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(Virkkula et al., 2006, 2009). However, observations of nanometer-sized secondary io
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organic aerosols have not been made over Antarctica. P
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Ourprincipalgoalinthispaperistofindouttheoriginofsecondaryaerosolparticles D
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and their precursors in the summer continental Antarctic atmosphere. In addition to c ACPD
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this, we aim to explore which vapours make the newly-formed particles to grow in s
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size,andwhetherAntarcticsecondaryaerosolformationiscapableofproducingcloud n
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condensing nuclei. a
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2 Materials and methods |
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2.1 Description of the site and measurements is biogenic precursors
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The aerosol and atmospheric composition measurements discussed here were car- io
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ried out between 5 December 2009 and 23 January 2010 at the Finnish Antarctic Re- P
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search Station, Aboa (location is shown in Asmi et al., 2010), in Queen Maud Land, p
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during the FINNARP 2009 expedition. The station is built on a nunatak Basen, ap- r
proximately 500m a.s.l. and some 130km away from the open ocean in summer. Dur- | Abstract Introduction
ing the summer, snow and ice on top of Basen melts into biologically active, shallow D
ponds. The most abundant macroscopic organism in these ponds is cyanobacteria isc Conclusions References
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15 Nostoc commune (Vaucher). The majority of the ponds during FINNARP 2009 expe- ss Tables Figures
dition were approximately 2km from the measurement site. The measurement site is io
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located 200m upwind from the main building. Since winds blow most of the time from Pa J I
the north-east, contamination by the station and vehicles that are used at the main pe
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station is minimal. We measured aerosols continuously at about 3m a.g.l. The total
particlenumbersizedistributioninthediameterrange10–500nmwasmeasuredusing |
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aDifferentialMobilityParticleSizer(DMPS),andthesizedistributionsofpositivelyand D
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negativelychargedparticlesinthediameterrange0.8–42nmweremeasuredusingan c FullScreen/Esc
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Air Ion Spectrometer (AIS). In order to get information on the aerosol chemical com- s
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position, particles were collected on quartz filters and the filters were changed three n Printer-friendlyVersion
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25 times a week. Methanolic extracts obtained from the filter samples after ultrasound- a
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assisted extraction were analyzed later in Finland using a comprehensive two dimen- e
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sional gas chromatography–time-of–flight mass spectrometer (GCxGC-TOF-MS). In D
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addition, samples from the cyanobacterial mats and water were taken and analysed. c ACPD
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2.2 Measurement set-up and equipment ion 12,32741–32794,2012
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Themeasurementsofneutralandchargedparticlesizedistributions,ozoneconcentra- p
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tionandchemicalfiltersampleswerecarriedoutduringtheFinnishAntarcticResearch
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Program (FINNARP) 2009 expedition. All the devices were kept inside a small con- |
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tainer,about200mupwindfromthemainstation,asdescribedbyVirkkulaetal.(2007) D
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and Asmi et al. (2010). The inlets were approximately 3m above the ground. For the c
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DMPS and the filter sampling, a 25-mm inlet with flow splitter with no sector-control ss E.-M.Kyro¨ etal.
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10 was used. A separate, 35-mm copper inlet was used for the AIS and for the ozone n
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monitor, a 6-mm-wide teflon tube was used as an inlet. a
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2.2.1 Air-ion spectrometer
| Abstract Introduction
Measuring the ion concentration and charge distribution of aerosol particles offers an D
effective method to study particle formation mechanisms. In this campaign the ion isc Conclusions References
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15 spectrometer was the only instrument able to measure directly the early stages of ss Tables Figures
atmospheric nucleation and subsequent growth. New particle formation event analy- io
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sis, including event classification and formation- and growth rate calculations for ion Pa J I
spectrometerdatahasalreadywell-definedguidelines(Hirsikkoetal.,2005;Manninen pe
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et al., 2010; Kulmala et al., 2012). The Air Ion Spectrometer (AIS) (Mirme et al., 2007)
measures the mobility distributions of both negative and positive air ions simultane- |
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ously in the range between 3.2 and 0.0013cm2V−1s−1, which corresponds to a mo- D
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bility diameter range of 0.8–42nm. The mobility diameter, i.e. the Millikan diameter, is c FullScreen/Esc
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applied when converting the measured mobility to the particle diameter (Ma¨kela¨ et al., ss
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2006). The AIS consist of two parallel cylindrical DMAs, one for classifying negative n Printer-friendlyVersion
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25 ions and the other for positive ions. The ions are simultaneously classified according a
totheirelectricalmobilitywithdifferentialradialelectricfieldandcollectedto21electri- pe InteractiveDiscussion
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cally isolated sections. Each section has its own electrometer to measure the currents D
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carried by the ions. The total flow into the AIS is 60Lmin−1, whereas the sample and c ACPD
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the sheath flows of the DMAs are 30 and 60Lmin , respectively. s
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2.2.2 Differential Mobility Particle Sizer P
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The Differential Mobility Particle Sizer (DMPS) (Aalto et al., 2001) setup measures at- r
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mospheric aerosol particle number size distribution between 10 and 700nm in diame- |
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ter. The DMPS consists of Hauke-type DMA (28.0cm long), CPC (TSI 3772) as a par- D
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ticle detector, closed loop sheath flow arrangement and radioactive Carbon-14 beta c
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neutralizer. The sample flow rate is 1Lmin−1 and the sheath flow rate is 10Lmin−1; ss E.-M.Kyro¨ etal.
10 both were checked regularly with a bubble flowmeter. The complete size distribution ion
is obtained in a 6-min time resolution by changing the classifying voltage of the DMA. P
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The total aerosol number concentration is calculated from the measured number size e TitlePage
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distribution.
| Abstract Introduction
2.2.3 Filter sampling D
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15 ThefiltersamplingwastakenfromthesamesamplinglineasfortheDMPS.Thefilters ss Tables Figures
that were used were quartz, 47mm in diameter (Whatman International, Kent, UK). io
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The flow rate was first 50Lmin but later (7 January 2010 onwards) it was changed P
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into25Lmin−1.Nocut-offwasusedintheinlet.Filterswerestoredinpetrislidesunder p
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a laminar flow hood inside the measurement container in room temperature. r J I
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2.2.4 Ozone analyzer Back Close
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A continuous ozone analyzer O342M by Environnement S.A was used to monitor the u
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ozone concentrations. The analyzer was calibrated before the campaign at an accred- io
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itedcalibrationlaboratoryattheFinnishMeteorologicalInstitute(FMI).Theozonecon- P
centration is detected by the difference in ultraviolet absorption between ambient air ap InteractiveDiscussion
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and ozone-cleaned sample. One measurement cycle takes approximately 10s. r
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2.2.5 Cyanobacterial mat and water samples D
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Samples from the ponds and cyanobacterial mats were takenon 3 January 2010. Two s
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50mL bottles were cleaned thoroughly with ethanol. One bottle was filled with water ion 12,32741–32794,2012
taken from the pond and another one with the water-Nostoc commune mixture. The P
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5 samplesweretakenfromthesamepondonthetopofBasen.Thesizeofthepondwas er Antarctic new
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approximately 40m and it was 10–20cm deep. Many similar ponds were found from particle formation
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the nunatak, the largest one being more than 100m in area. The bottles were stored from continental
in a freezer and transported to Finland in frozen container. Dis biogenic precursors
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2.3 Analysis of aerosol size distribution measurement ss E.-M.Kyro¨ etal.
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NPF events can be visually classified based on the shape of the particle size distribu- P
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tion into different types (Dal Maso et al., 2005; Yli-Juuti et al., 2009; Manninen et al., p
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2010; Kulmala et al., 2012). The different types of events are signatures of NPF hap- r
pening on different spatial and temporal scales and their shape is caused by the Eule- | Abstract Introduction
rianwayofmeasuringtheairmass.Traditional“banana”-eventsaretypicallyobserved D
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when NPF happens over geographically large area, whereas other types (e.g. “apple”, c
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“bump” and “wind-induced” all of which were observed at Aboa during FINNARP 2009 ss Tables Figures
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expedition) represent more local NPF. n
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The rate at which the newly-formed aerosol population grows (i.e. particle growth a J I
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rate, GR) can be determined from the measured number size distributions by follow- e
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ing the geometric mean size of the nucleation mode particles (Dal Maso et al., 2005;
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Yli-Juuti et al., 2011; Kulmala et al., 2012). The GR can be reliably determined only
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for “banana”-type events. Size-distribution – dependent particle losses can be charac-
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terizedbycondensationandcoagulationsinks(CSandCoagS,respectively)(Kulmala cu FullScreen/Esc
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et al., 2001, 2012; Dal Maso et al., 2002). The CS is a value of how rapidly vapour s
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molecules will condense onto pre-existing aerosol whereas CoagS determines how n Printer-friendlyVersion
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rapidly aerosol particles are removed trough coagulation scavenging. a
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Theformationrateofparticlesofcertainsize(J)iscalculatedbytakingintoaccount D
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the time evolution of the particle number concentration and the losses due to coagula- c ACPD
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tionscavengingtothelargerpre-existingparticlesaswellasthegrowthoutofthesize s
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range (Manninen et al., 2010; Kulmala et al., 2012). For charged particles, the losses n
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due to ion-ion recombination and sources due to charging of the particles needs to be a
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2.4 Chemical analysis from continental
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2.4.1 Filter samples: elucidication of the aerosol particle components c
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A comprehensive two dimensional gas chromatograph-time-of-flight mass spectrom- io
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eter (GCxGC-TOF-MS) from LECO (LECO Instrument Ltd., Stockport, Chesire, Eng- P
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land) was used for the elucidation of volatile and semivolatile organic compounds in p
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aerosol particles. The methodology used for the extraction, derivatisation, individual
isolationandidentificationofthecompoundswassimilartothatreportedearlier(Ruiz- | Abstract Introduction
Jimenez et al., 2011a, b). Briefly, the compounds were extracted from the filters by D
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sonication assisted extraction. Samples with and without derivatisation were analysed c
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in triplicate. The derivatisation step was necessary to increase the volatility of the ss Tables Figures
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semivolatile and low-volatile compounds. 50ng of 2,4-dichlorobenzoic acid, used as n
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internal standard (IS) for the derivatisation step, was added to the sample before the a J I
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derivatisation. Sample solvent was then evaporated with a gentle stream of nitrogen. e
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A mixture of 20µl of BSTFA containing TMCS (1%) and 20µl of pyridine was used
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as a derivatisation reagent. The reaction was accelerated by the application of ultra-
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sound for 30min at 35 C. Before GCxGC-TOF-MS analysis, 5ng of 1-1 -binaphthyl,
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used as IS for the injection, was added. In a third step, the most compounds present cu FullScreen/Esc
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in the extract were individually isolated and detected using the GCxGC-TOF-MS. The s
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identification was based on the comparison of the spectral information obtained from n Printer-friendlyVersion
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the detector and the retention indexes calculated using authentic standards with the a
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information provided by National Institute of Standards and Technology and the Golm er
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databases. Identified compounds were classified into seven groups according to their D
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chemical composition: hydrocarbons, halogenated compounds, nitrogen compounds, c ACPD
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sulphur compounds, carboxyl, carbonyl and hydroxyl compounds. s
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ThehighnumberofidentifiedcompoundsinGCxGC-TOF-MSmadethequantitation n
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a challenging task. The semiquantitation of the identified compounds was achieved in a
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this research using the normalized response factor (NRF), calculated as follows: e Antarctic new
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NRF=XNRF =XACi, (1) | from continental
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IS is biogenic precursors
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where AC is the peak area of the different analytes and A is the peak area obtained u
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10 for 1-1 -binaphthyl, used as the internal standard for the injection. io
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An average of 261 compounds per sample was identified using the proposed
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methodology.Theclassificationofthesecompoundsintothedifferentchemicalgroups ap
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(Fig.1)revealedthathydrocarbons,carboxylandhydroxylcompoundsarethefamilies r
which contain most of the compounds. In comparison with the results provided in the | Abstract Introduction
literature for aerosol particles collected at the SMEAR II station (Ruiz-Jimenez et al.,
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2011b), the total number of identified compounds in the Aboa samples was smaller, is Conclusions References
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but the relative composition of the particles in terms of number of compounds was the ss Tables Figures
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2.4.2 Samples from water and Nostoc commune p
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Samples 1 (only water) and 2 (water with small piece of cyanobacteria) were taken
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from the freezer 20min before the extraction. 5mL of sample was subjected two times Back Close
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to liquid-liquid extraction (LLE) with 5mL dichloromethane as such (a) or after pH ad- is
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justment (100µL of 1M HCl) (b). Zero samples were made from distilled water (same u
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treatment as real samples). Sample 3 (piece of cyanobacteria, 142.7mg fresh weight) io
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25 was extracted by static ultrasound assisted extraction with 10mL of acetone (30min) P
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as a solvent (Kallio et al., 2006) and filtered through 0.45µ m syringe filter. Volume of p InteractiveDiscussion
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allsampleswasreducedto5mLbyevaporationwithgentlestreamofnitrogenwithout r
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heating. Two aliquots of 1.5mL were taken from each sample for the further analysis. D
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ThesamplepreparationbeforetheinjectiontoGCxGC-TOF-MSwasidenticalwiththat c ACPD
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usedinthecaseofthefiltersamples.Intotal,135and227compoundswereidentified s
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from water (sample 1 and 2) and algae (sample 3) samples, respectively. n
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3 Results and discussion
5 particle formation
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Duringthecampaign,threenewparticleformation(NPF)eventperiodswereobserved D
(Fig.2,upperpanel).Infirsteventperiod,9to11December2009,theintensityofNPF is biogenic precursors
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was however very low, and occurred during an intrusion of air from higher altitudes. ss E.-M.Kyro¨ etal.
This could be seen as an increase in the ozone concentration at the measurement io
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site, but also in the HYSPLIT back-trajectories. The next two NPF periods were much P
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more intense compared to the first event period. In the following discussion we will p
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focus on these two periods.
The total particle concentration (contamination not taken into account) during the | Abstract Introduction
campaign was on average few hundreds of particles per cm3, while during the event D
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periods it increased to several thousands of particles per cm (Fig. 2, second panel). c
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Thehighestconcentrationswereobservedduringthesecondeventperiod(1to3Jan- ss Tables Figures
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uary 2010). n
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From Fig. 2 one can see that the normalized response factor (NRF) of Group 2 a J I
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(organic compounds that were enhanced during all event periods) compounds was e
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increased during all NPF periods, whereas Group 1 (organic compounds that were
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present only during the second event period) compounds were observed only during
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the NPF period 1 to 3 January 2010. Also the relative fraction of Group 2 compounds
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