Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 1 5 −

Open Access Discussions Chemistry , and S. Sugiyama and Physics Atmospheric 4,2 . Single particle analysis 3 − in coarse mode, and dominantly − 3 , H. Enomoto 2 µm under strong wind conditions. The 2,3 > and NO p − D 2 4 11394 11393 in 1 2 µm. In contrast, aerosol concentrations reached , K. Fukui − 2 > p D in 1 − , S. Fujita 2 0.3 µm, and 215 L > p D in fine mode during the traverse. Most sea-salt particles in the continen- in − , F. Nakazawa 2 4 1 1 0.3 µm, and 0.5 L − > contributed markedly to sea-salt modification in inland areas during summer. Mg- p − 3 D This discussion paper is/has beenand under Physics review (ACP). for Please the refer journal to Atmospheric the Chemistry corresponding final paper in ACP if available. Department of Earth System Science, Faculty of Science, Fukuoka University, National Institute of Polar Research,Tateyama Tokyo, Caldera Japan Sabo Museum, Toyama, Japan Kitami Institute of Technology, Kitami, Japan Institute of Low Temperature Science, Hokkaido University, Sapporo, Japan ground levels, and to interpret ice core records (e.g., Savoie et al., 1992, 1993; Minikin rich sea-salt particles andmodes Mg-free from sea-salt the particles coastwith were to sea-salt present fractionation inland in on areas. coarse the These and snow surface fine sea-salt of particles continental Antarctica. might be1 associated Introduction Atmospheric aerosol constituents inthan Antarctic three decades regions to have elucidate been the measured regions’ for aerosol chemistry, more to monitor Earth back- Ca-rich sulfates, and mineralsparticles were identified were as modified minor greatly aerosol withwith constituents. SO SO Sea-salt tal region were modifiedNO with sulfate and methanesulfonate near the coast, although regions during the traverse.in The lowest aerosol number concentrations3278 L were 160 L estimated aerosol mass concentrations wereof 0.04–5.7 µgm aerosol particles collectedning during electron the microscope equipped JASE with traversejor an was energy aerosol conducted dispersive constituents X-ray using spectrometer.sea-salts, were a Ma- and scan- sulfates fractionated in sea-salts fine in mode, coarse mode. and K-rich sulfate, sulfates, sea-salts, Mg-rich modified sulfate, Measurements of aerosolconducted number on concentrations and continentalAntarctic direct Antarctica expedition aerosol during (JASE) sampling the fromconcentrations were traverse 14 in of November background 2007 Japanese–Swedish conditions until joint 24 decreased January gradually 2008. with Aerosol latitude in inland Abstract Atmos. Chem. Phys. Discuss., 14, 11393–11445,www.atmos-chem-phys-discuss.net/14/11393/2014/ 2014 doi:10.5194/acpd-14-11393-2014 © Author(s) 2014. CC Attribution 3.0 License. 1 Fukuoka, Japan 2 3 4 5 Received: 26 March 2014 – Accepted: 22Correspondence April to: 2014 K. – Hara Published: ([email protected]) 7 MayPublished 2014 by Copernicus Publications on behalf of the European Geosciences Union. Horizontal distributions of aerosol constituents and their mixing statesAntarctica in during the JASE traverse K. Hara 5 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , − 3 and SO − 3 2 4 cient in- were dis- ffi , CH − 3 − 2 4 SO 3 and CH in August at Syowa Sta- − 2 4 − 3 O) in sea ice formation and frost was mixed internally with sulfate 2 − 3 2H · SO 3 ) in summer and sea-salts in winter–spring. 4 11396 11395 SO ), and minor aerosol constituents (minerals and 2 − and Cl are strongly dominant during the summer on the Antarc- + particles) near the surface on the Antarctic coasts during − 3 4 O) and hydrohalite (NaCl SO 2 3 SO 2 10H · 4 and CH SO 2 − 2 4 during the summer, and were modified with NO − 3 , and sea-salts (e.g., Na SO − 3 3 Although useful and important knowledge related to aerosol chemical properties Sea-salts are dominant during winter–spring (e.g., Hara et al., 2004). Sea-salt par- Previous investigations (e.g., Savoie et al., 1992, 1993; Minikin et al., 1998; Hara From those earlier investigations, basic aerosol chemical properties were obtained: (e.g., concentrations, and mixinginvestigations states) using has bulk been and obtained single-particle gradually from analysis previous of aerosol particles along the 2000, 2002; Hara et al.,flowers) 2004, by 2012). depletion Sea-salt of fractionationing Na-salts on winter–spring sea-ice engenders on (including Mg-enrichment the frost AntarcticHara in coast et sea-salt (Hara al. particles et (2013) al., dur- in pointed 2010, sea-salt out 2012, particles) the 2013). occurs likelihood Furthermore, during(1) that summer. “where The sea-salt does following fractionation sea-salt questions, (Mg fractionation however, remain; and separation occur (2) on “what the Antarctic are regions the during specific summer?”, processes of sea-salt fractionation (Mg separation)?”. their mixing states incation, and near sea-salt surface–lower fractionation freetion, (Hara sea-salt troposphere et particles (2.5 al., km), were 2013).mirabilite fractionated sea-salt (Na In through modifi- addition precipitation of toflower several sea-salt appearance salts modifica- under such colder conditions as (e.g., Wagenbach et al., 1998; Rankin et al., ticles were distributed widelyStation in (Hara ultrafine–coarse et mode al., throughoutthe 2010a, summer the at 2011a) year Aboa and at Stationtal were (Kerminen Syowa analysis et distributed of al., in individual 2000; particles fine–coarse Teinilä et2013) using mode al., reported EDX, 2000). during Mouri that From et elemen- sea-salt al.CH (1999) particles and near Hara the et al. surfacetion. (2005, Furthermore, were single modified particle with analysisballoon SO of operations aerosol exhibited particles seasonal collected and using vertical tethered- features of aerosol constituents and in Antarctic troposphere during summer. Inmicroprobe addition, mass single spectrometry particle showed analysis that usingparticles CH laser (probably H summer (Wouters et al., 1990; Hara et al., 1995). thin-film method) to demonstrate that sulfuric acid was dominant in aerosol constituents tributed mainly in the sub-micrometerLegrand, range 2001; at Read the et Antarctic al., coasts 2008). (e.g., Yamato Jourdain et and al. (1987a, b) used chemical testing (Ca gle particle analysis are fewet (e.g., Parungo al., et 1992; al., Mouri 1979; et Yamato et al., al., 1999; 1987a, Hara b; et Artaxo et al., 1996, al., 2005, 2004, 2013). near 2013) surface showed were sulfates that (probably H majorActually, SO aerosol constituents intica Antarctic because of atmosphere biogenic activity2001). in Size the ocean segregated (e.g., aerosol Minikin et analysis al., showed 1998; that Legrand et SO al., (mainly ion chromatography). Suchformation techniques, about however, cannot the provide mixing su is states of necessary respective to aerosol elucidate constituents.geneous chemical That reactions) information reactions and thatanalysis origins occur takes of on longer aerosol constituents. than particles bulk For analysis. (hetero- sample Therefore, analysis, previous investigations single using particle sin- Dome F Station, Kohnen1995; Station, Hara and et Concordia al.,et (Dome 2004; al., 2008; Weller C) Udisti and Station et Wagenbach, al., (e.g., 2007; 2012). Bodhaine, Jourdain etseasonal features al., of 2008; the concentrations Eisele ofNO major aerosol constituents (SO carbonaceous species (soot and organics) atinvestigations, Antarctic aerosol coasts and constituents inland area. were In these determined using bulk analysis techniques investigations of aerosol chemistrySyowa have Station, been Neumayer Station, conducted Halley atson Station, coastal Station Dumont stations d’Urville (e.g., Station, such SavoieWeller and as et et Maw- al., al., 1992, 2011),gated aerosol 1993; recently chemistry Legrand even and et at atmospheric al., inland chemistry stations 2001; have such Hara been as et investi- Amundsen–Scott al., (South 2004; Pole) Station, et al., 1998; Legrand et al., 2001; Hara et al., 2004; Weller et al., 2011). Although most 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | C ◦ 0.3, 0.5, 0.7, 1.0, 2.0, and 5.0 µm. The OPC > 11398 11397 p D and 1013.25 hPa). Aerosol number concentrationscounter (OPC, were KR12A; measured Rionsite. The Co. using measurable Ltd.) size range during apacked was direct in portable aerosol an sampling optical insulatorcated at box on particle every was the camp set windwardhaust side at from of ca. snow the 1 m vehicles). camp25 Aerosol above s site (corresponding number the to to concentrations avoid snow 1 L local wereconcentrations surface air contamination recorded by sucking) were (mainly every during tripod, converted ex- the 23– lo- measurements. to The the ambient number concentration under standard conditions (0 size distribution, and direct aerosolthe sampling daytime were but not were made during conducted the only traverse at during camp sites. 2.3.1 Measurements of aerosol number concentrations mately at 3 m above theair snow surface. temperature, Daily meteorological wind observations direction, (air,and pressure, wind cloud speed, type) weather, were visibility, degreeduring made aerosol of around measurements cloud 15:00 conducted LT. cover, Weather at conditions camp were sites. observed2.3 also Aerosol measurements Aerosol measurements and direct aerosoltraverse. For sampling safe were conducted operation during of the aerosol JASE measurements, measurements of the aerosol Continuous measurements of air pressure (F4711;air Yokogawa Analytical temperature Systems (KDC-A01-S001 Inc.), andand KADEC21-U4; wind Kona direction System (KADEC21-KAZE; Inc.),JASE traverse. Kona wind Meteorological sensors System speed, were fixed Inc.) on the were snow performed vehicle, located during approxi- the 2.2 Meteorological measurements during the JASE traverse southern side of theS16 ice on divide 24 for January glaciological 2008. measurements. Details The of team the approached traverse were described in Fujita et al. (2011). Syowa Station) to aSwedish meeting team point traveled on fromAerosol the measurements Wasa Antarctic and Station plateau direct to aerosol viaing sampling the Dome for the this F meeting study Japanese Station. point wereNovember team The conducted via 2007, dur- traverse. and Kohnen arrived The Station. ating Japanese the meeting traverse. traverse point After team on somethen, 27 left December joint the from 2007 outgoing scientific in S16 traverse the worksoutgoing (return on incom- traverse, at the to 14 Japanese the team S16) traveled meeting began from the on point meeting point 30 for to December Dome several F 2007. days, on During the the 2 Aerosol measurements and data analysis 2.1 JASE traverse Figure 1 depicts thethis JASE campaign, traverse the route Japanese in team Droning traveled Maud from Land, S16 East on Antarctica. the On Antarctic continent (near and direct aerosol sampling wereand conducted elucidate during the the JASE horizontalin traverse atmosphere features to near of characterize the aerosol surfacemainly constituents discuss on (1) the and the Antarctic horizontal their continenton distributions mixing during of the aerosol summer. states Antarctic constituents Herein, and we continentfractionation. mixing during states summer, (2) sea-salt modification, and (3) sea-salt ties and chemical processes takingtiotemporal place features on of the Antarctic glaciologicalMaud continent. environment Land, To elucidate and East spa- Antarctica, atmospheric scientifica quality traverse Japanese using in Swedish snow Droning Antarctic vehicles Expedition was(Fujita (JASE) conducted et in by al., the 2011). In austral this summer study, of measurements 2007/2008 of the aerosol number concentrations Antarctic coasts, a great dearth of knowledge remains for aerosol chemical proper- 5 5 20 15 10 20 25 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ff C in ◦ 2.9 − C at latitudes ◦ C. In addition, . The impactor ◦ 1 − 30 43 − − , drifting snow occurred 1 S, when diurnal features − ◦ S. Similarly, similar diurnal varia- ◦ C). ◦ C in the incoming traverse and ) and 45 044 particles in fine mode (mean: ◦ 1 − 11400 11399 7.6 − S in both incoming and outgoing traverse, although the highest ). Although we attempted to analyze as many coarse particles ◦ 1 − C on average (maximum, 16 ◦ S in this study. The lowest air temperature was ◦ Wind speed often showed diurnal feature during the traverse. In addition to diurnal Individual aerosol particles on the sample substrate were observed and analyzed 2005) and Antarctic coastswere (Sato mutually and synchronized Hirasawa, well 2007).occur. at However, According the latitudes to diurnal higher a maxima thanclear manual 74 and weather fine. check When at windduring every the speed camp traverse, was for site, greater example weather on thanber. was 28–29 ca. November, mostly 6 7 ms December, and 21–23 Decem- features of wind speed,ple the on 18–22 wind November, speed 27–30though increased November, the 7–8 because diurnal December, maximum of and of 20–23of turbulence, air wind December. for temperature speed Al- was exam- were observed lagged attions at noon of latitudes time wind lower (LT), than speed those 73 were observed on Antarctic continent (Allison, 1998; Van As et al., Figure 2 shows variations of latitude,the elevation, air JASE temperature, traverse and wind ofwith speed latitude during the in Japanese 69–73 team.temperature The near air the coast temperaturethe was outgoing decreased traverse. ca. gradually By contrast,higher the than air temperature 73 wasair around temperature showed strongapproximately diurnal 8.6 variation. The diurnal temperature range was 3.1 Meteorological conditions during the JASE3.1.1 campaign Air temperature, wind speed and weather near the surface 3 Results and discussion coarse mode (mean: 58 particlessample961 particlessample as possible, the lower aerosolof number the concentrations analyzed in aerosol coarse particles mode limit in the this number study. alytical conditions weretime. the To following: 20 avoid kVticle, analytical accelerating the bias voltage rectangular anding of or 30 an s localization square counting electron ofquality area beam aerosol were almost in described constituents covering EDX in in a analysis. Hara each particle et Details par- was al. of scanned (2005, analytical 2013). us- procedures We and analyzed data 2690 particles in number concentrations on theducted for Antarctic 28–86 continent, min (mean, directAfter 60 min) aerosol direct depending sampling, sampling on aerosol was the samplesuntil aerosol con- were number analysis kept concentration. in in air ourmorphological tight laboratory change boxes and including in chemical desiccant Japan reactions. to prevent humidificationin that this can engender studysive with X-ray a spectrometer scanning (SEM-EDX; electron Quanta microscope FEG-200F, FEI; equipped XL30; with EDAX an Inc.). energy An- disper- Aerosol particles were collected onmicrogrid (square-300 carbon-coated mesh; collodion Veco Co.) thin using filmdiameter a supported two-stage of aerosol by the impactor. Ni- The impactor cut-o was was set 2.0 at and ca. 0.2 1 µm m above at the a snow flow surface next rate the of OPC. 1 Because Lmin of the lower aerosol 2.3.2 Direct aerosol sampling and analysis 5 5 15 20 10 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | S came traveled near the coast to ◦ 1 − as “background aerosol 1 S, air masses at the camp − ◦ in this study. Therefore, we 1 − S were transported from near the ◦ 11402 11401 . The number concentrations on the Antarctic S and 73–75 1 ◦ − 75 > to 0.5 L 1 − S in the incoming traverse were transported westward along ◦ 2 µm changed, respectively, from ca. 1330 L > p D S traveled in the free troposphere over the Antarctic continent during the ◦ , and from 36 L 1 71 − > aerosol particles during the JASE traverse 0.3 µm and > For comparison of the aerosol size distribution, we estimated the “Junge-slope” in p ing that air masses oncoastal areas the during Antarctic the continent prior duringder 5 JASE the days, were release this not of increase transportedParticularly aerosol suggests the from that particles number strong and concentrations winds small in engen- 2.0 µm snow/ice coarse particles flakes increased having from remarkably diameter the byshown larger snow one–two in than surface. orders Figs. higher 4tures in and in strong 5. the wind The outgoing traverse conditions, aerosol were as number similar concentrations to those and inthis their the study. horizontal incoming The fea- traverse. aerosol size distribution in fine–coarse mode can be approximated as D ca. 160 L continent during the JASE traverse wereover lower Syowa Station than in those summer in (Hara the etincreased lower al., considerably free 2011b). under troposphere The conditions aerosol with number concentrations strong wind and drifting snow. Consider- Figures 4 and 5Junge slope, depict and features aerosol mass ofcamp concentrations site wind during during speed, direct the aerosol JASE theconcentrations traverse. sampling During aerosol decreased at the number each gradually incoming concentrations, traverse, withconcentrations the in aerosol latitude strong number and winds. elevation, Higherunder except aerosol conditions number high with concentrations number wereuse wind identified aerosol speeds concentrations at higher windconcentrations” than speeds in lower 6 this than ms 6 study. ms For instance, the background number concentrations in the Antarctic continent by Suzuki et al. (2013). 3.2 Number concentrations, mass concentrations, and size distribution of the JASE traverse showed good agreement with analysis of the air mass origins over continent (Fig. 3c). Theto transport S16 pathway during was the clearlycontinent outgoing divisible (Fig. traverse into 3d). from transport Although Domeover air from F the masses continent, coastal air at areas masses latitudesSouth and in higher Pole, transport than and over 73 were the C transported in along East ice Antarctica, ridgesmoved near respectively. through Furthermore, ground near air level Domethe (probably A masses large in and in variability boundary Dome the ofThese layer) outgoing vertical features for motions traverse of past in transport 5 the pathways days, incoming of in traverse air contrast from masses to S16 on to the Antarctic Dome continent F. during boundary layer (near surface).(transport Compared from to the free weather troposphere)corresponded at to and fine camp second days, sites, and typetively. the conditions Backward (transport with first trajectories strong type in winds in and the theF drifting boundary outgoing indicate snow, respec- traverse layer) transport from in the the meeting point boundary to layer–lower Dome free troposphere over the Antarctic sites located in 69–71 with Antarctic coastal linetrajectories imply during that the these prior airtroposphere. masses In 5 traveled contrast days. in to Vertical the thesites upper features transport in boundary of pathway and in the lower 69–71 prior backward free 5 days. Air massesthe in Antarctic the plateau traverse during from themasses Dome prior were F 5 classified to days into the (Fig. (1) meeting 3b). transport The point from vertical flowed the free motions over troposphere in and these (2) air travel in the To elucidate the history and originsward of air trajectory masses was observed computed in using thisthis study, the the study NCEP 5 day (Draxler reanalysis back- and dataset200 and Rolph, ma.g.l. kinetic 2013). mode over Figure in each 3 depicts camp the site. backward As trajectories depicted from in Fig. 3a, air masses from the camp 3.1.2 Air mass history during the JASE traverse 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | (near 3 ). Major − 3 − to estimate 3 − 0.3 µm) under strong wind > p ) and NaCl (2.2 gcm D 3 − . Higher mass concentrations were 3 ) or drifting snow. The Junge-slope (near coasts) to 0.04 µgm − 1 3 − − 6 ms > erence derived from the reduction of aerosol 11404 11403 ff under conditions with drifting snow and strong winds. The highest ) was estimated as 0.3–5.0 µm in diameter. The Junge-slope was 3 β respectively represent a constant and the Junge-slope. In this study, − erence of the Junge-slopes might result from horizontal features of ff β β − p ciently from the atmosphere through dry deposition during transport, iso- and ffi αD erences between the incoming traverse and outgoing traverse might reflect α = ff ) in the incoming traverse. In contrast, the Junge-slope decreased to less than p 1 D − N d Figure 3 shows that air masses on the Antarctic continent were transported over Here, we attempt to estimate the mass concentrations using aerosol number con- dlog from coastal regions intoconcentrations increased the markedly Antarctic in plateau all during size ranges summer. ( The aerosol number observed in high numberfrom concentrations in snow coarse surface mode. by Therefore,to erosion aerosol high under aerosol particles strong mass winds concentrations. might make significant contribution the Antarctic plateau during theremoved prior e 5 days. Consideringlation that from coarse coastal particles regions can mightcentrations be account in for coarse gradient mode. features In of other aerosol number words, con- coarse particles are supplied only slightly at Kohnen Station (Wellerconcentrations and water Wagenbach, soluble 2007), aerosol andUdisti constituents slightly et at higher al., Dome than 2010). C The thethan (Preunkert aerosol several mass et µgm mass concentrations al., increased 2008; mass considerably concentrations to were approximately larger 5.7 µgm concentrations can be underestimated slightly.tions In addition, were aerosol observed number usingwere concentra- measured OPC under above ambient snowin conditions surface. (not an Thus, dry insulator conditions), number box.of although concentrations water Therefore, OPC in the packed aerosol estimatedunder particles mass conditions in concentrations this with included study.tions drifting In masses exception gradually snow of and decreased higherDome strong from mass F winds, concentrations ca. Station). the 0.16traverse The µgm aerosol were mass similar mass to concentrations concentra- the on mass the concentrations of Antarctic water continent soluble aerosol during constituents JASE corresponded to the densityaerosol of constituents sulfates (ca. were 1.8 sulfatein gcm later particles Sects. during 3.4 JASEthe and mass traverse 3.5). concentration (details Therefore, in we aresmaller this used than shown study. 0.3 the µm The were density number not of included concentrations in 1.8 of gcm the estimation. aerosol Therefore, particles the estimated mass the following equation (Junge, 1963). Indeed, the number concentrations intors coarse – mode one in order JASE lower traverse than were those several fac- over Syowa Station. centrations, assuming spherical shape and density of aerosol particles. The density Antarctic continent during earlypared summer to (or Junge-slope end-spring) over2011b), the through Syowa Junge-slope mid-summer. Station was slightly Com- (range, highertraverse. 2.2–3.2; on The the median, di Antarctic continent 2.5, duringthe Hara the number JASE et concentrations, al., particularly in coarse mode, from coasts to inland areas. tributions depended closely on release ofblowing. In aerosol particles addition, the from Junge-slopes snow in surfacesthose by the in wind outgoing the traverse were incoming slightlyrelease traverse. larger (especially than This in di coarsetions mode) during from the thestable outgoing in snow traverse. December–January surface Considering on under thethese that Antarctic calm di weather region wind (e.g., conditions condi- Satoseasonal are and features Hirasawa, usually of 2007), aerosol number concentrations and the size distribution on the 6 ms 2.5 under conditions within strong the outgoing winds traverse ( wasconditions. 2.73–3.37 Similar (mean, to 3.03; median, thecreased 2.92) Junge in under slope strong background winds in during the the incoming outgoing traverse, traverse. the Consequently, aerosol Junge size slope dis- de- Therein, the Junge-slope ( 2.22–3.03 (mean, 2.70; median, 2.75) in background conditions (wind speed lower than 5 5 25 15 20 10 20 25 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 4 − 2 4 : 0.2– p 2 µm) in D particles. > 4 p D 11406 11405 in the Antarctic troposphere during summer. Fig- is well-known as a major mineral constituent (gyp- 4 4 SO 2 . Mg-rich sulfate particles in the lower troposphere over H, which are derived mainly from oceanic bio-activity. 4 3 SO 3 and CH particles in the Antarctic atmosphere remain unclear. 4 4 . Hereinafter, we designate these aerosol particles as “sulfate particles”. SO − 3 2 SO 3 particles were identified in the lower troposphere on the Antarctic region (Hara 4 Aerosol particles containing Ca and S were also observed in this study (Fig. 7d). Be- Peaks of Mg and S were obtained from aerosol particles as portrayed in Fig. 7c. In fact, S and K were detected from aerosol particles as shown in Fig. 7b. Aerosol origins of CaSO ification. Details of Mg-rich sulfateSect. particles 3.7. and sea-salt fractionation are discussed in cause of the atomic ratiosCaSO of Ca and S, particleset of al., this 2010, type 2013). might Actually, be CaSO sum). CaSO Moreover, Marion and Farren (1999)(gypsum) and formation Gelifus et by al. sea-salt (2013) fractionation pointed on out CaSO sea-ice in polar regions. However, the Atomic ratios of Mg andpatible S with of the the ratios aerosol of particles MgSO Syowa containing Station only were Mg identified and dominantly Scontinent in were (Hara com- air et al., masses 2013). transported Harathe from et Antarctic al. the atmosphere (2013) Antarctic were reported associated that with Mg-rich sea-salt sulfate fractionation particles and in sea-salt mod- sphere in Antarcticbe region formed (Hara through etoceanic gas-to-particle al., bioactivity. 2010, conversion Therefore, from 2013). K-richparticles. aerosol K-rich sulfate As discussed precursors particles sulfate by Okada particles might derived etfate be from al. cannot particles (2001, non-biogenic 2008) and and aerosol nss-K Niemisuch in et as al. aerosol (2005), biomass particles K-rich burning. sul- are Becauseing released of on from the combustion the negligible processes sourceAntarctica Antarctic strength via regions, of the biomass the free burn- troposphere. particles might be transported from outside of the Because EDX can providefrom CH only elemental information, we cannotparticles distinguish containing SO S andidentified K in had no aerosol satellite samples structure. taken Similar in aerosol particles the were lower free troposphere–upper free tropo- Yamato et al. (1987) andmainly Hara of et H al. (2013) showed that these particles might consist 3.4 Aerosol constituents and mixing statesFigure during 7 the presents JASE traverse examplesthe of JASE EDX traverse. Although spectra strong of peaksthese of each peaks C, aerosol were O, derived and particle Ni from collectedcluded were the detected during sample from in substrate. all Therefore, discussion samples, C,observed in O, and from this Ni aerosol were study. particles ex- Asemental with compositions, shown morphology a in (satellite satellite structure), Fig. structure. and Comparison 7a, previous among investigations strong by the peaks el- of S were shape and crystal-like shape. Inoften addition, in coarse staining mode, around as the depictedcles solid in with Fig. core irregular 6b. was solid Some identified coarse coresin particles (not coarse were shown). and satellite Presence fine parti- of modes theatmosphere. suggests stain strongly and that satellite these structure particles had liquid phase in the Figure 6 depicts examplesJASE traverse. of Figure 6a SEM shows that imageslite most structure. of of The aerosol satellite aerosol particles particles in particles were2 fine dominant µm). mode collected in The had all during satellite a samples satel- in particles the this fine were study. mode Yamato ( often et observed al. (1987) alsosatellite used particles in chemical consisted coarse tests of mode (Ca H ( ure thin 6b film shows method) that to aerosol showcoarse mode. that particles Most without non-satellite particles a in satellite coarse structure mode had were a also solid observed core with in irregular portant role in maintainingto-particle the conversion. “aerosol system” over the continent in3.3 addition to gas- Morphology of aerosol particles collected during the JASE traverse conditions. Therefore, the wind-blowing release of aerosol particles might play an im- 5 5 25 15 20 10 20 25 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | and − 2 4 S during the incoming tra- ◦ might contribute significantly − 3 in Antarctic troposphere during − 3 SO 3 SO 3 S on the way from Dome F Station to ◦ and CH . In addition, internal mixtures of minerals and − and CH 4 2 4 11408 11407 − 2 4 SO 2 S and less than 2.8 % at latitudes higher than 72 . Additionally, the height of Mg relative to Na was higher than that of sea-salt ◦ − 3 SO 3 In fact, Si, Al, and S were detected from solid particles as shown in Fig. 7i. Al and Si Peaks of Na, Mg, S, and Cl were obtained aerosol particles as shown in Fig. 7e. than 72 verse. In addition, the relative abundance of sea-salt particles increased markedly at sea-salt particles in coarsethe mode high decreased abundance gradually at in samplingthe inland sites meeting areas in point in 77–76 in exceptionabundance of the of incoming sea-salt traverse. particles, With thecles relative the increased abundance gradually gradual up of decrease to thesea-salt of 40 modified particles % the sea-salt on were relative parti- dominant the in Antarcticpredominance fine plateau. of mode By sulfate in contrast, particles the the in incoming modified ticles fine traverse. and Because mode, of the the the relative modified abundance sea-salt of particles sea-salt were par- less than 6.8 % even at latitudes lower 3.5.1 Sea-salts In coarse mode, major aerosolticles particles and were sulfate particles. sea-salt The particles, relativewas modified abundance larger sea-salt of sea-salt par- than particles 40 in % coarse near mode the coast in the incoming traverse. Relative abundance of 3.5 Horizontal distributions of aerosol constituentsTo during compare the quantitatively JASE horizontal traverse distributionsing of each states, aerosol constituent we andaerosol estimated mix- constituent. the Figures relativedance 8 abundance of and aerosol (number mixing 9 fraction) states(14 show in November–27 of coarse December horizontal 2007) and each and distributions fine typeJanuary the modes of 2008). outgoing during of traverse relative the (27 incoming December abun- traverse 2007–24 solid core in some mineralcles particles. (irregular solid Considering particles) that satellite S structure,particle these was coated particles detected acidic were sulfates in likely and mineral to H sea-salt be parti- mineral particles were often identified in this study (Fig. 7j). particles. Furthermore, stain and satellite structures were observed around irregular were major constituents. Therefore, particles of this type might be identified as mineral Modification of sea-salt particles issalt discussed constituent, in Sect. Mg 3.6. was Although notas Mg detected portrayed is from in a aerosol major Fig. sea- particles 7h.clearly A containing from particularly Na, the K, strong particle and KTherefore, in Cl, peak particles relative Fig. of to 7h. this Na type NaThe peak were sea-salt-like is was identified particles a identified as were dominant observed “sea-salt-likeF only constituent particles” to at in in the sampling meeting this sea-salt sites point study. on particles. inparticles the the way were incoming from collected traverse Dome on under 21–23 conditions December with 2007 drifting when aerosol snow. 7e and f. Acidicto species Cl other depletion than fromas SO sea-salt a particles. wholly Also, Cl-depleted the sea-saltparticles particle. particle as Hereinafter, in we “modified Fig. designate sea-salt 7g whollytially particles”. Cl-depleted might Cl-depleted Less be sea-salt Cl-depleted identified particles sea-salt particles were divided and par- into “sea-salt particles” in this study. in Fig. 7f. Clwith in acidic sulfur sea-salt species particlessummer such can (e.g., as Mouri SO be et liberatedFig. al., through 7f 1999; might heterogeneous Hara be reactions et sea-saltCH particle al., modified 2005, with 2013). acidic Therefore, sulfurparticles the species in particles such Fig. as in 7d. SO sea-salt The particle particle in with Fig.from slight 7f aerosol Mg-enrichment. might particle Although be in identified Fig. Na, as 7g, Mg, the a and peak wholly height S Cl-depleted of were S detected was lower than particles in Figs. These elements are majoranalyzed seawater using constituents. SEM-EDX, When artificial theConsequently, NaCl peak the particle particles height in were of Fig.particles. Cl 7e Also, was Na, might Mg, slightly be and higher identified Sto were than as aerosol detected partly that particle from Cl-depleted in aerosol of particle sea-salt Fig. Na. in 7e, Fig. the 7f. peak Compared height of S relative to Na was higher in particle 5 5 20 25 15 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | S. As de- ◦ S and at 77–76 ◦ S during the incoming traverse, whereas air ) respectively showed a maximum and min- ◦ + 11410 11409 S) were transported over the continent during the ◦ particles. Because horizontal distributions of the mod- 4 72 > S on the way from Dome F to the meeting point. As described erence of the relative abundance between in the incoming tra- ◦ ff and sea-salts (Na − 2 4 particles, and (5) CaSO 4 ) in aerosol particles show a minimum at Syowa and Dome F stations during sum- + Figures 8 and 9 show that sulfate particles were dominant in both coarse and fine Relative abundance of sea-salt particles and the modified sea-salt particles in coarse et al., 1998; HaraUdisti et et al., al., 2004; 2012). The Weller relative and abundance Wagenbach, of 2007; sulfate particles Preunkert in et fine al., mode 2008; was 82.9– analyzed particles in each sampleupper in limit fine of mode relative (mean, abundancebe 958 of particles/one less aerosol particles sample), than the other 0.1relative than % abundance sulfate in particles of these might sulfate(1) samples particles increase (100 in % of the the abundance number outgoingmation of concentrations traverse and of sulfate is particle sulfate particles). likely particles growth,particles to Higher and through and new result (2) the particle decrease from modified for- of sea-salttrations particles the during of number the concentration nss-SO summer. of Indeed,imum mass sea-salt concen- in the summer (January–February) in Antarctic coast and inland (e.g., Minikin modes. Particularly, the mean relative98.5 abundance % of sulfate in particles the inples incoming fine taken mode traverse on was and themode 99.5 Antarctic % reached plateau, in 100 the % the relative in abundance outgoing incoming of traverse. and sulfate In outgoing particles some traverses. in Because sam- fine of the number of 3.5.2 Sulfates The following aerosolsulfate particles particles, containing (2) sulfates modifiedMgSO sea-salt were particles, identified (3) in sulfateified sea-salt this particles particles containing study: were K, described (1) this (4) in section. Sect. 3.5.1, their description is excluded from mer (Hara et al., 2004). Inmodified addition, sea-salt the relative particles abundance of2013). decreased sea-salt Therefore, considerably particles the and di over the Syowaverse Station and (Hara in the etparticles outgoing al., from traverse the might end correspond of to spring toward seasonal summer features on of the sea-salt Antarctic continent. (Na mode during the incomingmodified traverse, relative sea-salt abundances particles of were sea-salt remarkably particles lower. and Mass the concentrations of sea-salts relative abundance of sea-saltmode particles was and similar the to modifiedunder that strong sea-salt in wind particles the conditions, incoming in thegoing modified traverse coarse traverse. sea-salt except However, particles the the were relative high dominant abundancesea-salt relative in of particles abundance the sea-salt out- in particles fine andoutgoing the mode traverse. modified was In mostly some lessand samples than the taken 0.5 on modified % the sea-salt inhorizontal Antarctic particles inland distributions plateau, were areas of sea-salt not during sea-salt particles detected the particles in and fine the mode. modified Compared sea-salt to particles the in fine sea-salt particles and thesummer modified sea-salt might particles be on associatedsurface the via with Antarctic wind-blowing. continent the during transport pathway and releasemode from ranged the mostly in snow lower than 60 % during the outgoing traverse. Although the total tions of sea-salt particles and modifiedpathway, however, sea-salt cannot particles account in for the the continent.and high The the relative transport abundance modified of sea-salt sea-saltpicted particles, particles in Fig. for 4, example the at aerosolin number 72–73 coarse concentrations mode, increased under considerably, particularly strongpoint. wind Consequently, high conditions aerosol in number thedance concentrations incoming and might traverse their result to high the fromfrom relative meeting abun- redistribution the snow of surface. aerosol Therefore, particles the such horizontal as distribution of sea-salt relative particles abundance of above, sea-salt-like particles (Na–K–Cl) werethese observed sites. dominantly According in to the coarsefrom 5 mode the day at coasts backward trajectory was as foundmasses depicted only in in at Fig. 69–71 the 3,prior inland transport 5 area days. Therefore, ( isolation from the coastal regions might cause gradual distribu- sampling sites in 77–76 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | S). ◦ 72 erence 8.7 % in 2.0 % in ff < − − 0.1 % in out- ) examined in − 4 ) was n.d. 4 0.5 % in fine mode. During the − gas) under conditions with the low 4 SO 2 11412 11411 S, although those were observed in some aerosol samples 0.9 % in fine mode in this study. Although K-rich sulfate par- 0.2 % in fine mode in incoming traverse. However, the relative ◦ − − 1.8 % in coarse mode and n.d. − Relative abundance of Ca-rich sulfate particles (probably CaSO The relative abundance of Mg-rich sulfate particles (probably MgSO The relative abundance of K-rich sulfate particles was not detected (n.d.) coarse mode and n.d. abundance of Ca-rich sulfate particlesgoing was n.d. traverse. in Although coarse Ca-rich modein and sulfate both n.d. particles traverses, Ca-rich were sulfate not particlesAlthough detected Ca-rich were sulfates identified in (e.g. mainly most gypsum) near are samples were coasts mineral not components, ( most mixed Ca-rich with sulfates Alquently, horizontal and distributions Si, and which external are mixingimportant states major contribution of elements of Ca-rich of non-mineral sulfates mineralas origins imply particles. the suggested such by Conse- as Geilfus sea-salt et fractionation al. on (2013). sea-ice quently, the presence ofon Mg-rich sulfate the particles Antarctic inoccurs continent the on in atmosphere the near this Antarctic thediscussed study continent in surface during strongly Sect. summer. 3.7. suggests Details and that of by Hara sea-salt sea-salt et fractionation fractionation al. are (2014). collected at plateau sites. However,the Mg-rich Antarctic sulfate plateau particles during weresulfate the identified particles mainly outgoing was on traverse. lower The inMg-rich relative the sulfate abundance particles outgoing of were traverse Mg-rich distributed than mostlyet that in al., fine in mode 2013). the over incoming Previous Syowaparticles Station traverse. investigation (Hara were (Hara associated et with(Cl al., sea-salt loss fractionation 2013) by (Mg indicated heterogeneous separation) that reactions).surface and Mg-rich snow, High modification and Mg-enrichment sulfate drifting was snow observed at in Dome aerosols, F during summer (Hara et al., 2014). Conse- concentrations at the South Pole in the summer (Bodhaine, 1995). this study was n.d. incoming traverse, Mg-rich sulfate particlespling were found sites frequently in in fine 69.2–72.5 mode at sam- origin aerosol particles (e.g., sulfate particles containing K) was supported by high BC via free troposphere during summer for the prior 5 days. The presence of combustion- implies seasonal features of K-rich sulfate– particles summer. in K-rich the sulfate inland particles areatroposphere during were over late-spring distributed Syowa also Station in (HaraHara boundary et et al., layer al. – 2010, (2013), upper 2013). K-rich free Asand sulfate discussed fossil particles above fuel and might by have combustion.rect originated Figure from transport 3 biomass from shows burning outsides thatMoreover, of source the the strength backward of Antarctic combustion trajectory Circle ofregions. was exhibited fossil Particularly, not fuel di- biomass is found burning extremely for does lowfore, the not on sulfate prior particles the occur containing Antarctic 5 on K the days. are Antarctic likely regions. to be There- transported to the Antarctic continent coarse mode and n.d. ticles were obtained inoften a in few fine samples mode in in coarsein this mode, the study. these incoming Moreover, K-rich particles traverse. sulfate Inin were particles addition, observed the were the incoming often relative traverse observed abundance was of higher K-rich than sulfate that particles in the outgoing traverse. This di ing the JASE traverse. Suchnot a observed high in relative the abundance boundaryStation of layer coarse (Hara but sulfate et often particles al., in was thecoarse 2013). lower Figure and free 5 fine troposphere shows modes oversequently, that Syowa were sulfate the lower aerosol particles near number the cancondensation concentrations surface of in be on condensable grown vapors the (e.g.,number to Antarctic concentrations H continent. coarse of Con- pre-existing mode particles on through the coagulation Antarctic continent. and lower free troposphere overJanuary Syowa (Hara Station, et Antarctica al., duringin 2013). mid-November fine Consequently, through mode the near relative the abundancefree surface of troposphere on the sulfate over Antarctic particles the continentsulfate Antarctic was particles coast similar to in (Syowa that Station). coarse in The mode the relative often lower abundance exceeded of 40 % on the Antarctic continent dur- 98.2 % (mean, 93.1 %) in the boundary layer and 96.2–99.7 % (mean, 98.1 %) in the 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | . − 2 4 but also − 2 4 0.1 % (mean, − by heterogeneous − , 2003; Weller et al., 2 4 ff on the Antarctic conti- − 2 4 erence of mixing states of min- ff 11414 11413 14.6 % (mean, 3.8 %) in coarse mode and n.d. − formation on sea-salt particles might make an important cient deposition of minerals onto the snow surface on the − 3 ffi 5.7 % (mean, 1.8 %) in coarse mode and n.d. − . In contrast to sea-salt modification in coarse mode, most of the modified sea-salt − 2 4 Most sea-salt particles in coarse mode had Cl ratios lower than the seawater ratio 0.4 % (mean, 0.1 %) in fine mode during the incoming traverse, although the relative Antarctic continent might be modified preferentially with acidic sulfur species such as troposphere (e.g., Jourdain and Legrand,2011), 2002; heterogeneous Rankin NO and Wol contribution to sea-salt modificationcoarse in sea-salt inland particles areasHara was during et wholly summer. al. depleted Moreover, (2005,modified in Cl slightly 2013) most in over reported Syowa samples station thatSO taken in most the in sea-salt summer. the Some particlesparticles of inland. in them in were coarse fine modified mode moderatio with were relative were to distributed the in modified the sea-salt Cl particles. Therefore, ratio fine of sea-salt ca. particles 0 on % the and higher S atomic in this study. Although Sparticles, ratios increased the gradually S with decreased ratiosline, Cl in which ratios sea-salt suggests in sea-salt that particles sea-salt wereacidic particles less species were than modified other those not thannent of only acidic during the with summer. sulfur SO stoichiometric Considering species plausible acidic such species as of SO aerosols on the Antarctic sea-salt modification, the internal mixing particlesexcluded between from sea-salts the and ternary minerals were plots andatomic discussion. ratios Red of and bulk blue seawater stars ratiosThe respectively and denote black wholly Cl line depleted represents sea-saltseawater the particles ratio by stoichiometric SO (red line star) fromWhen to Cl the in the sea sea-salt Cl-depleted salt particlesreactions, sea particles is each sea replaced salt with salt stoichiometrically particles bulk particle to by is SO distributed sulfates along (blue the star). stoichiometric line. 3.6.1 Sea-salt modification in coarse andFigure fine 10 modes portrays examplesmodified of sea-salt ternary particles plots (Na–S–Cl) during of the sea-salt JASE particles traverse. and To the avoid misunderstanding of 3.6 Sea-salt modification during the JASE traverse reactions during their transport toing inland state areas. of As mineral described particlesstates above, can of a lead change mineral to of particleaerosol particles. mix- particles, size Because greater internal of than mixing theport among the external might minerals, higher mixing sulfate, enhance dry and theAntarctic sea-salts deposition e continent. during velocity trans- of coarse 1988; Delmonte et al., 2004,cles 2007). were In often contrast, present external in mixinglocated the states boundary at of layer the mineral and parti- coast free troposphereeral (Hara over et particles Syowa Station al., suggests 2006,internal that 2013). mixtures The mixing through di coagulation states in of cloud processes, mineral and particles through heterogeneous changed gradually to − abundance was n.d. 0.01 %) in fine modenally mixed during with the sea-salts outgoing orobserved sulfates traverse. mainly in Most this in mineral study. coarse particles Althoughsolid mode, the were cores mineral SEM inter- containing particles observation were Alirregular showed and that solid Si cores the was ranged sizecles coincident of in (mainly with irregular sub-micrometer mineral the particles) in size in this distribution ice study. of cores The taken water-insoluble size in parti- of Antarctica (e.g., Ram and Gayley, In spite of a smallerparticles source area containing of Al mineral and particlesparticles on Si containing the were Si Antarctic identified and continent, Al during aerosol weredance the classified of JASE into “mineral traverse. mineral particles”. Here, particles The aerosol relative was abun- n.d. 3.5.3 Minerals 5 5 25 15 20 10 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , 4 to − 3 Na − 3 / SO cient 2 Na of Na ra- ffi / SO / 3 Na ratios in Na ratios in can be con- / / ered between x ff and CH Na and S / − 2 4 ) released from the 3 concentration in the sur- − 3 Na ratios in coarse mode / production near the surface, concentration during summer 3 contributed dominantly to sea- x S in the incoming traverse. High − 3 ◦ et al., 2008). Actually, NO cient HNO Na ratio increased slightly. Similarly, me- Na ratios in sea-salt particles are 0.5. As ff / ffi / S in the incoming traverse from Dome F to ◦ during transport over the Antarctic continent. 11416 11415 ,S in the continental atmosphere. − − 3 3 2 4 might be formed on sea-salt particles through het- − 3 production in the atmosphere might occur on the Antarctic 3 . Previous investigations (Mouri et al., 1999; Hara et al., 2005, 2013) Na ratios were observed as shown in Figs. 11 and 12. High S − 3 to sea-salt modification. Furthermore, the 5 day backward trajectory / in the atmosphere. Therefore, high NO − 3 3 SO 3 S in the incoming traverse, the S ◦ . Na ratios of sea-salt particles and the modified sea-salt particles in coarse 2 / and CH − Na ratios in coarse mode was observed in 69–71 2 4 In contrast to sea-salt modification in coarse mode, S was enriched considerably in Field measurements of the surface snow in polar regions (e.g., Davis et al., 2001, As described above, the acids contributing to sea-salt modification di / surface, they can beHowever, modified high by S NO face snow around Queen Maud Land,2005), especially considerable around HNO Dome F Stationplateau. (Bertler Therefore, particulate et al., NO erogeneous reactions with reactivesnow nitrogen surface. oxides (mainly HNO the modified sea-salt particlesfine in sea-salt fine particles mode are in transported Antarctic to continent the in inland this area study. When and released from the snow NO concentrations (orders of severaltion hundred during pptv) were summer observed (Davis atverted et South to Pole al., HNO Sta- 2001;on Ne the Antarctic plateauas might suggested by engender Dibb e et al. (2004). Considering the high NO tios on the Antarcticdrifting plateau snow. As often discussed corresponded in toticles Sect. on 3.2 conditions and the with 3.5.1, Antarctic strong therefore, plateauAntarctic most winds were coarse continents. and likely sea-salt Then, to par- sea-salt havereactive originated particles nitrogen from oxides in surface such coarse snow as on HNO mode the might be modified2004; with Frey et al.,nisms 2009; of Jones snow-nitrate et near al., the surface 2011) of implied polar photochemical-recycling regions mecha- during summer. Indeed, high as depicted in Fig.not 3 been shows transported that directly continental fromdry air coasts deposition during masses of the on coarse priortic the aerosol 5 coasts Antarctic particles, days. might plateau coarse Because be had of particlesAntarctic transported e plateau) suspended only for at slightly longer to the than the Antarc- 5 Antarctic days. continent Figures (particularly 11 the and 12 show that high Cl tribution of NO during summer. The airand its mass precursors history on and the Antarctic origins continent of must be coarse discussed sea-salt to elucidate particles, high NO con- suggested in ternary plotssalt in modification Fig. in coarse 10. mode Therefore,fine on sea-salt NO the particles Antarctic exceeded continent. mostly By 0.5each contrast, during sea-salt S the particle traverse. in The fine highparticles S mode through imply heterogeneous that reactions sulfates with wereand gaseous formed sulfur SO species on such the as fine H sea-salt those in coarse sea-salt particles on the Antarctic coasts and those on the continent the meeting point. Inin spite 69–71 of thedian latitudinal S gradient of Cl mode were distributed approximatelyparticles in are 0.2 during modified the solely JASE with traverse. SO When sea-salt 3.6.2 Horizontal features of sea-salt modificationFigures on 11 the and Antarctic 12 continent showsea-salt horizontal particles features and of the thethe atomic modified ratios sea-salt incoming of particles and Cl intween outgoing coarse sea-salts and traverses, and fine respectively. minerals modes The wereCl during excluded internal from the mixing box particles plots.Cl Latitudinal depletion be- gradient was of identified inexcept most some aerosol samples samples obtained taken for at the Antarctic 76.5–76 plateau, SO revealed the high contributionsea-salt of modification acidic in sulfur fine speciesduring mode such summer. in as the SO atmosphere on the Antarctic coastal regions 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Na / ). Here, we particles. In 4 4 0, even in coarse 0 and around the ≈ ≈ 0.11 in bulk seawater ≈ O) (Hara et al., 2012), Mg in 2 2H · Na ratio 0) in coarse mode were identified / ≈ Na ratios varied greatly because of pres- / 0 as “Mg-free sea-salt particles”. In addition Na ratios in coarse mode during the JASE ). When sea-salt fractionation and sea-salt 2 Na ratio / ≈ 11418 11417 / Na ratios in fine mode were added to “Supple- / particles were often observed in this study, as shown in 4 O) and hydrohalite (NaCl 2 Na ratio might be supplied by transport from coastal regions to 10H · / 4 ). 4 SO 2 Na ratios in coarse mode were approximately 0.32 in the incoming traverse / Because sea-salt particles were modified dominantly during JARE (as shown in Figs. addition, Mg-free sea-salt particlesoften (Mg on the Antarctic continent, particularly on the Antarctic plateau. For example, ures 14 depict horizontaltraverse. features Horizontal of features Mg ofment”. Internal Mg mixtures ofdian sea Mg salts and mineralsand were 0.31 removed in from the(e.g., the Wilson, outgoing plots. 1975), traverse. Me- Mg Because mightAs of be shown enriched Mg in in the mostence ternary sea-salt of plots Mg-rich particles (Fig. sea-salt in 13), particles, coarse Mg Mg-free mode. sea-salt particles, and MgSO be possible to assess the possibility of sea-salt fractionation on3.7.2 the Antarctic continent. Horizontal features of sea-salt fractionationTo on elucidate the sea-salt Antarctic fractionation continent oncompare the horizontal Antarctic features continent during of summer, sea-salt we constituents must on the Antarctic continent. Fig- ratios cannot beregions changed during by winter sea-salt throughcan modification. spring promote Sea-salt (e.g., Mg fractionation precipitation enrichmentConsequently, in sea-salt of in fractionation mirabilite sea-ice in sea-salt sea-ice and regions particles,of hydrohalite) cannot as account Mg-Free sea-salt for reported the particles presence during byover spring–summer. Hara Syowa Because Station Mg-rich et were sulfate al. identified particles inet (2012). the al., air 2013), masses from discussion thesea-salt must Antarctic address particles continent horizontal (Hara and features Mg-free of sea-salt Mg-rich particles sulfates, Mg-rich on the Antarctic regions. Then it will stoichiometric line between the reddesignate star sea-salt particles (seawater) with and Mg green ratio to star Mg-free (MgSO sea-salts, MgSO Figs. 7–9 andmodified 13. sea-salt Similar particles distributions collected were over observed Syowa in Station (Hara sea-salt et particles al., and 2013). the Mg mode. The Mg ratios in fine mode were distributed at Mg ratio were greater than the stoichiometricand line blue of star). sea-salt Some of modification the (between modified the sea-salt red particles star had Mg ratio salt particles are distributedseawater around ratio) the and stoichiometric line themodification between cyan by the star sulfate red occur (MgCl starare stoichiometrically distributed (bulk and around the simultaneously, stoichiometric sea-saltgreen line particles star between (MgSO the red star (seawater ratio) and 10–12), most sea-salt particles and thedistributed modified in sea-salt particles 60–90 % in coarse of mode the were Na atomic ratio. The Mg ratios in coarse mode, however, stoichiometric line between thesea-salt ratio red with star sulfate). (seawater Withas sea-salt ratio) mirabilite fractionation (Na and by the precipitationsea-salt of blue particles Na-salts star such can (modified be(replacement enriched between gradually. Na For and cases Mg) occurs in without which sea-salt modification sea-salt by fractionation sulfate, sea- 3.7 Sea-salt fractionations on the Antarctic3.7.1 continent during summer Sea-salt fractionations in coarse andFigure fine 13 mode shows examplessulfates of in ternary coarse plots and ofremoved sea-salts fine from (Na, modes. the Mg, Internal ternarywater and mixtures plots. ratio S) In are of and distributed the sea Mg-rich around ternaryparticles salts the are plots, red and modified star sea-salt minerals (bulk by particles were seawater sulfate with ratio). and When bulk not the sea- fractionated, sea-salt they are distributed around the free troposphere over Syowathe Station longer during residence summer time (Harafine of et mode with al., fine high 2013). aerosol S the Because particles, continent. of the modified sea-salt particles in ratios in the modified sea-salt particles were also obtained in boundary layer and lower 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Na ra- / cient dry deposi- ffi Na ratios during the / O) as discussed by Marion and Far- 2 orescence (e.g., Ge et al., 1998; Wise C even during summer, as presented in ffl ◦ 12H · 30 2 − 11420 11419 S) in the traverse from Dome F to the meeting ◦ particles were present also in fine mode on the Antarc- 4 C for KCl and MgCl ◦ 36 − particles) might be originated from surface snow on the Antarctic conti- 4 C and particles on the snow surface of the Antarctic continent, it is necessary to ◦ 4 34 − Figure 2 show that the air temperature near the surface had diurnal change also in To explain the presence of Mg-rich sea-salt particles, Mg-free sea-salt particles and studies (e.g., Ge et al., 1998; Wise et al., 2009; Woods et al., 2010) revealed that (e.g., Kameda et al., 1997;air temperature, Motoyama the et relative al., humidity 2005). mightface exhibit With on a strong the diurnal diurnal Antarctic change change near continent100 % the of during during snow the summer. sur- the Actually, relative localStation humidity night during reached time summer ca. and (Van reachedmidity As a can et minimum engender al., in (1) 2005). the phaseon afternoon The transformation surface at by diurnal snow, deliquescence Kohnen variation (2) ofsurface of condensation available hoar) the sea-salts and relative during re-freezing hu- local ofsuper-cold night water liquid time, vapor on and (e.g., the (3) formation surface enhancement of snow. of Laboratory quasi-liquid experiments layer conducted and for earlier tinent and coastal regionswas (Hara controlled not et only al., by 2013). lower air This temperature result but implies alsocontinental by that areas. other Mg Furthermore, factors. separation strongradiation diurnal engender change water of sublimation air on temperatures the and snow solar surface of the Antarctic continent perature might constitute anca. important condition for someren sea-salt (1999). precipitation Unlike (e.g., sea-saltscontent in were seawater, however, supplied sea-salts solelyported in by from snow deposition coastal on regions. of the Whenture, sea-salt Antarctic Mg Mg-free particles sea-salt separation particles, is that Mg-rich controlled had sea-saltcan only particles, be been by and present lower trans- Mg-rich tempera- on sulfate the particles observed over Antarctic Syowa regions. Station However, during Mg-free winter sea-salt in particles the air were masses not transported from the con- phase transformation by deliquescence andet e al., 2009; Woodson et the al., temperature 2010). (Marion Sea-salt andon fractionation Farren, the in 1999; Antarctic seawater Hara plateau freezing was etFig. depends often al., 2 below 2012). and The previous air investigations temperature (King et al., 2006; Hirasawa et al., 2013). Air tem- through (1) seawater freezing (Marion and Farren, 1999; Hara et al., 2012), and (2) discuss Mg separation processes. Redistribution of chemical constituents can occur blowing under strong conditions,and as Mg-free described NaCl above. werefractionated Furthermore, present sea-salt in Mg-rich particles surface sulfates and (Mg-rich snow MgSO sea-salt (Iizuka et particles, al.,nent. Mg-free 2012). Considering sea-salt Therefore, that particles, the wind Mg-free conditions sea-salt (especially on particles 21–23sary December), were strong for often wind the blowing release observed might of be under Mg-free neces- sea-salt strong particles. MgSO sea-salt particles in coarseparticles mode and over other fractionated Syowa sea-salt Stationsea-salts particles suggests had such not that as originated Mg-rich Mg-free sulfates fromtion sea-salt and coastal of Mg-rich regions, aerosol considering particles the inpecially e coarse in mode. coarse Aerosol mode, particles were on supplied the to Antarctic a plateau, marked es- degree from snow surface by wind tic continent, although the low relativesea-salt abundance of particles sea-salt prevented particles us andtios the from modified on elucidating the the horizontalJASE Antarctic features traverse plateau. of imply These Mg stronglywidely horizontal that throughout features the the of fractionated Antarcticwere Mg sea-salt continent identified particles during mainly were distributed summer.(Hara in et Mg-free fine al., sea-salt mode 2013). particles Figurelated and from 3 coastal rarely shows regions that in for air the coarse prior masses 5 on mode days. the The over lower Antarctic relative Syowa plateau abundance Station were of Mg-free iso- 21–23 December 2007point, (76.6–76.0 as shown in Fig.corresponded 14. often The to presence occurrence oftrations Mg-free of in sea-salt drifting particles coarse snow in mode andsea-salt coarse in particles, high mode the and aerosol MgSO incoming number traverse. concen- Mg-rich sea-salt particles, Mg-free Mg-free sea-salt particles in coarse mode were dominant in three samples taken on 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Na and / − 2 4 . When O, 33 % 3 2 − 6H · 2 , 84 % (Tang and 4 in fine mode in this SO − 2 2 4 89 %) was often higher ∼ ) might have originated from x , and NO 3 11422 11421 . (e.g., HNO − 3 , 42 % (Wang et al., 2008); and KCl, 84 % (Tang, 4 in surface snow and then oxidation in the atmosphere. − 3 Na in sea-salt particles and modified sea-salt particles in / , 75 % (Tang and Munkelwitz, 1994); MgCl 3 in coarse mode, and dominantly with SO The JASE traverse was organized by several organizations both in Swe- − 3 orescence might not be key processes for Mg separation. With diur- 89 %) on the Antarctic continent. Therefore, phase transformation by ffl ∼ and NO contributed to sea-salt fractionation in coarse and fine modes over Syowa Sta- − 2 4 − 3 SO 3 Single-particle analysis using SEM-EDX revealed that major aerosol particles were under conditions with strongparticles winds were and likely drifting to have snow. beenand Therefore, released fractionated assessed from the sea-salt the snow surface. hypothesisoccurs This that in study proposed surface sea-salt snow fractionation on the (Mg Antarctic separation continent. in sea-salts) coarse and fine modes werefree often sea-salt higher particles than the were bulkratio identified seawater cannot on ratio. be In changed the addition, by Antarctic sea-salt Mg- ticles, continent. modification, Mg-free the Because sea-salt presence particles, the of and Mg Mg-rich Mg-richsea-salt sea-salt sulfate fractionation. particles par- Mg-free might be sea-salt associated particles with in coarse mode were often identified during the JASE traverse.minerals The were minor K-rich aerosol sulfates, constituents in Mg-rich coarseCH sulfates, and fine Ca-rich modes. Although sulfates, SO and tion during summer (Harawith et al., SO 2005, 2013), sea-saltstudy. Precursors particles of were particulate modified NO greatly photochemical recycle of NO Median atomic ratios of Mg coasts during theparticles) prior might 5 be released days. from Therefore, the coarse snow surface aerosol by particles blowingsea-salt particles, winds. (mainly modified sea-salt sea-salt particles, andthat sulfate the particles in sulfate coarse particles mode, and and modified sea-salt particles were dominant in fine mode drastically, especially in coarse mode. Air masses were isolated from the Antarctic mass concentrations instrong size winds range and larger drifting than snow 0.3 µm occurred, were aerosol 0.04–5.7 µgm number concentrations increased 4 Concluding remarks Measurements of aerosol sizethe distribution Queen and Maud direct Land, aerosoluntil Antarctica sampling 24 during were January the made 2008. JASEtions in OPC traverse decreased measurements from gradually revealed 14 that November withsnow aerosol 2007 or latitude strong number under winds) concentra- on background the Antarctic conditions continent (without during summer. drifting The estimated aerosol water vapors and super-coldprocesses water on such surfacefreezing. as snow Therefore, hoar might we propose formation. cause thatity Particularly, sea-salt the and re-freezing repetition fractionation water of sublimation as a undersurface diurnal well colder snow cycle on conditions as of the can relative seawater Antarctic engender humid- continent Mg during separation summer. on the Munkelwitz, 1994); NaNO (Kelly and Wexler, 2005);1980). MgSO Most plausible sea-saltsative can humidity be ( wholly deliquescentdeliquescence/e even under minimum rel- nal features of airon temperature the and snow relative surfacecold humidity, during re-condensation water the of local in water night nanometer-to-micrometer vapor time scales, might quasi-liquid induce enhancement layer, of and super- re-freezing of ized in the outerdeliquescence. layer Although (surface) relative humidity around was a minimaltion solid in (Van the core afternoon As through at et phase Kohnenthan Sta- the transformation al., deliquescence by 2005), relative humidity theare (DRH) minimum of the plausible following: relative sea-salts. NaCl, Some humidity 75 examples % ( (Tang and Munkelwitz, 1993); Na chemical constituents with lower deliquescence relative humidity (DRH) can be local- Acknowledgements. den and Japan. The National Institute of Polar Research (NIPR), Tokyo and the Swedish Polar acpd-14-11393-2014-supplement.pdf Supplementary material related to thishttp://www.atmos-chem-phys-discuss.net/14/11393/2014/ article is available online at 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , , 10.5194/acp-14-1587- http://ready.arl.noaa.gov/ 10.1007/s00382-004-0450-9 , E., and Zhongqin, L.: Snow , W., Huey, G., Tanner, D., ff ff 10.1016/j.atmosenv.2003.01.001 chemistry: an assessment of factors controlling x 11424 11423 , 2008. ort of NIPR, Stockholm University, the Royal Institute of Technology in Stock- (last access: 7 May 2014), NOAA Air Resources Laboratory, Silver Spring, MD, ff , 2014. 10.1016/j.atmosenv.2007.04.013 nitrate stable isotope signal in snow and atmosphere of East Antarctica and implications for during isCAT 2000, Atmos. 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S., Abbatt, J. P. D., Artaxo, P., Rabello, M. L. C., Maenhaut, W., and van Grieken, R.: Trace elements and individual of the JASE traverse.H. Special Kaneko, thanks T. Karlberg, are P. Ljusberg extendedN. and to Shiga, K. the for Taniguchi and their logistics the verythe members, medical Swedish generous S. Research doctors, support Gunnarsson, Council S. during (VR) Eriksson and thefrom and by traverse. the a This Grant-in-Aid Japan for research Society Scientific was for Research the supported (A) 20241007 Promotion by of Science (JSPS). References Allison, I.: Surface climate of the interior of the Lambert Glacier basin, Antarctica, from auto- a collaborative e holm and individuals from several universitiesresearch and project institutes undertaken in Japan. by Thetems the JASE for Japanese traverse climate is Antarctic one change Research andtechnologies”. 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Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |

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Altitude, m Altitude, 30˚W m Altitude, 30˚W Continued. Continued. Fig. 3c. Fig. 3b. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 11436 11435 Horizontal features of air temperature, elevation, wind speed, aerosol number concen- Horizontal features of air temperature, elevation, wind speed, aerosol number concen- Fig. 5. trations and Junge slopeindicate during conditions outgoing with drifting traverse snow. from the meeting point to S16. Red boxes Fig. 4. trations and Junge slopeindicate during conditions incoming with traverse drifting from snow. S16 to the meeting point. Red boxes Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Fig. 7 Fig. * * * * (i) (j) (f) (g) (h) * * * * * * 6 Fe

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Counts Counts Counts Counts Counts EDX spectra of aerosol particles collected during the JASE traverse. Asterisks show SEM images of aerosol particles in background peaks derived from the sample substrate. Fig. 7. Fig. 6. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | coarse coarse Fig. 9 Fig. Fig. 8 Fig. (a–b) (a–b) 4 Sea-salt particles Cl with sea-saltModified particles Cl without sea-salts + Minerals + sulfatesMinerals CaSO Sulfates containingK Soot (External) Sulfates(External) Sulfates containingMg Sea-salt particles Cl with sea-saltModified particles Cl without + sea-salts Minerals + sulfatesMinerals CaSO4 Sulfates cotainingK Soot (External) Sulfates (External) Sulfates containingMg 75 75 S S (d) (b) o o 76 76 77 77 (RT root) Latitude, Latitude, (d) (b) 78 78 DF - Meeting point DF - Dome F - Meeting point Dome F - 11440 11439 S S o o S16 - DF S16 S16 - Dome F - Dome S16 JASE traverse Latitude, Latitude, JASE traverse (a) (a) (c) (c) 68 69 70 71 72 73 74 75 76 77 78 68 70 72 74 76 78 0 5 0 0 5 0 80 60 40 20 95 10 80 60 40 20 95 10

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80 80 1.0 0.8 0.6 0.4 0.2 0.0 2.0 1.5 1.0 0.5 0.0 1.0 0.8 0.6 0.4 0.2 0.0 3.0 2.5 2.0 1.5 1.0 0.5 0.0

0 20406080100 0 20406080100

Cl/Na S/Na S/Na 100 Cl/Na 100 Ternary plots (Na–S–Cl) of sea-salt particles in coarse and fine modes during the Cl, At-% Cl, Horizontal features of atomic ratio of Cl the incoming traverse. In boxline, plots, and the bottom top bar respectively bar,The denote top red values box line of line, shows 90 black %, mean middle 75 values. %, box 50 line, % bottom (median), box 25 %, and 10 %. Fig. 11. Fig. 10. JASE traverse. Red, and blue(2) stars wholly respectively Cl denote depleted atomic sea-salt ratiosamong particles of constituents. with (1) sulfates. bulk Black seawater, lines and represent stoichiometric lines Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Fig.12 . 4 Fig.13 76 S o 0 Mg, At-% 20 40 60 77 80 , and (4) MgSO 100 2 0 Coarse Fine Latitude, Na, At-% 78 20 40 Outgoing traverse DF - Meeting point Meeting DF - 60 0 20 40 60 80 100 80 0 0 100 20 20 S, At-% 40 40 60 60 80 80 100 100 Fine mode Fine Fine mode Fine Coarse mode 0 0 Na in coarse and fine modes during Coarse mode RT240 / MD146 2008-0102 20 20 2007-1123 40 40 60 60 80 80 0 20406080100 0 20406080100 100 100 Na and S 0 0 / 20 20 S o 40 40 11444 11443 60 60 80 80 100 100 S16 - DF S16 0 0 Latitude, DK244 MD228 2007-1221 20 20 2007-1125 Outgoing traverse 40 40 60 60 80 80 0 20406080100 0 20406080100 100 100 0 0 20 20 Mg, At-% 40 40 70 72 74 76 78 60 60 80 80 100 100 H9 0 0 MD508 Na, At-% Na, 2007-1204 20 20 2007-1114 40 40

60 60 1.0 0.8 0.6 0.4 0.2 0.0 3.0 2.5 2.0 1.5 1.0 0.5 0.0 1.0 0.8 0.6 0.4 0.2 0.0 2.0 1.5 1.0 0.5 0.0

80 80 S/Na S/Na Cl/Na Cl/Na 0 20406080100 0 20406080100 Ternary plots (Na–Mg–S) of sea-salt particles in coarse and fine modes during the 100 100 S, At-% Horizontal features of atomic ratio of Cl Fig. 13. JASE traverse. Red, blue,seawater, cyan, (2) and green wholly stars ClBlue, respectively pink depleted denote and sea-salt atomic red particles lines ratios represent of with stoichiometric (1) sulfates, lines bulk among (3) constituents. MgCl the outgoing traverse. In boxline, plots, and bottom the bar top respectively bar,The denote top red values box line of line, shows 90 %, black mean 75 middle values. %, box 50 % line, (median), bottom 25 box %, and 10 %. Fig. 12. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | fig. 14 fig. 76 S o 77 Latitude, Latitude, 78 Coarse mode Coarse mode Coarse Na in coarse mode during the incoming / S o 11445 Latitude, 70 72 74 76 78 Outgoing traverse Incoming traverse

1.0 0.8 0.6 0.4 0.2 0.0 1.2 1.0 0.8 0.6 0.4 0.2 0.0

Mg/Na Mg/Na Horizontal features of atomic ratio of Mg Fig. 14. traverse. In box plots,bottom bar the respectively top denote values bar,line of shows top 90 mean %, box values. 75 line, %, 50 black % middle (median), 25 box %, and line, 10 bottom %. The box red line, and