[1] Observations of aerosol constituents and acidic gases in the Antarctic area were carried out at Syowa (39.58°E, 69.00°S) in 1997 and1998 and Dome Fuji stations (39.62°E, 77.37°S) in 1997. Sea-salt concentrations decreased to background levels in the summer at both Syowa (Na + , 4 nmol m À3 ) and Dome Fuji (Na + , $0.44 nmol m À3 on average). During the winter, blizzard and strong wind may cause an increase of sea-salt particles at Syowa, whereas long-range transport from the boundary layer at midlatitudes and coastal Antarctic regions may contribute significantly to the increase in sea-salt particles observed at Dome Fuji. Particulate Cl À and Br À are liberated preferentially from sea-salt particles at Syowa and Dome Fuji in the summer. The molar ratio of Cl À /Na + and Br À /Na + at Syowa decreased to $0.5 and %0, respectively, in summer. At Dome Fuji more Cl À tend to be liberated from sea-salt particles thorough heterogeneous NO 3 À formation. The concentrations of gaseous chlorine species (mostly HCl) and bromine species ranged from 0.2 to 5.3 nmol m À3 and below detection limit (BDL) to 1.5 nmol m À3 , respectively, corresponding to sea-salt modification. In the present study, SO 4 2À depletion due to mirabilite formation was observed not only at Syowa but also at Dome Fuji. This evidence suggests that SO 4 2À depletion might occur through sublimation on snow surfaces in addition to seawater freezing. At Syowa, sea-salt fractionation relating to Mg 2+ , K + , and Ca 2+ was also observed mostly under strong wind conditions.

Measurements of key chemical and physical parameters made along continuous and selected long sections of polar ice cores provide reliable past snow accumulation rates and other environmental records. The prime accumulation indicators include variations found in the stable isotopes, ionic constituents, and acidity concentration levels; and physical changes in the strata and structure. Cross correlations of the time series curves resulting from multiparameter analyses of ice cores from Antarctica (NBY89, SP78, BS68) and Greenland (CR74, D3 81, D3 18C) have been made. The results permit construction of a bipolar chemical stratigraphy chronology of volcanic events that is coherent with the δ 18O and Electrical Conductivity Method data sets and consistent back‐in‐time with historically recorded volcanic activity. A bihemispheric comparison of high non‐sea‐salt SO42− peaks shows strong correlation at 1885, 1836, 1816, 1810, 1459, 1346, 1287, 1278, 1259, 1228, and 1168 A.D. at time of snow deposit. The prominent 1259 A.D. volcanic signal appears to be a significant bipolar ice core index horizon.

During our aerosol measurement program at Syowa Station, Antarctica, in 2004–2007, some low‐visibility (haze) phenomena were observed during winter–spring under conditions with low winds and without drifting snow and fog. During “Antarctic haze” phenomena, the number concentration of aerosol particles and black carbon concentration increased by 1 to 2 orders higher relative to background conditions at Syowa Station, whereas surface O3 concentration dropped simultaneously, especially after polar sunrise. Chemical analysis showed that major aerosol constituents in the haze phenomena were sea salt (e.g., Na+, Cl−). Trajectory analysis and the Navy Aerosol Analysis and Prediction System model showed that plumes from biomass burning in South America and southern Africa were transported to Syowa Station, on the Antarctic coast, because of the eastward (occasionally westward) approach of cyclones in the Southern Ocean and subsequent poleward flow. This poleward flow from midlatitudes of the plume and injection of sea‐salt particles during the transport might engender Antarctic haze phenomena at Syowa Station. Differences of O3 concentration between the background and the haze conditions tended to be larger in spring (after polar sunrise) than in winter. Enhancement of sea‐salt particles in the haze events can serve important roles in providing additional sources of reactive halogen species.

Tethered balloon-borne aerosol measurements were conducted at Syowa Station, Antarctica, during the 46th Japanese Antarctic expedition (2005–2006). Direct aerosol sampling was operated from near the surface to the lower free troposphere (approximately 2500 m) using a balloon-borne aerosol impactor. Individual aerosol particles were analyzed using a scanning electron microscope equipped with an energy dispersive X-ray spectrometer. Seasonal and vertical features of aerosol constituents and their mixing states were investigated. Results show that sulfate particles were predominant in the boundary layer and lower free troposphere in summer, whereas sea-salt particles were predominant during winter through spring. Minerals, MgSO₄, and sulfate containing K were identified as minor aerosol constituents in both boundary layer and free troposphere over Syowa Station. Although sea-salt particles were predominant during winter through spring, the relative abundance of sulfate particles increased in the boundary layer when air masses fell from the free troposphere over the Antarctic coast and continent. Sea-salt particles were modified considerably through heterogeneous reactions with SO₄²⁻ CH₃SO₃⁻ and their precursors during summer, and were modified slightly through heterogeneous reactions with NO₃⁻ and its precursors. During winter through spring, sea-salt modification was insignificant, particularly in the cases of high relative abundance of sea-salt particles and higher number concentrations. In August, NO₃⁻ and its precursors contributed greatly to sea-salt modification over Syowa Station. Because of the occurrence of sea-salt fractionation on sea ice, Mg-rich sea-salt particles were identified during the months of April through November. In contrast, Mg-free sea-salt particles and slightly Mg-rich sea-salt particles coexisted in the lower troposphere during summer. Thereby, Mg separation can proceed by sea-salt fractionation during summer in Antarctic regions

Abstract. Tethered balloon-borne aerosol measurements were conducted at Syowa Station, Antarctica during the 46th Japanese Antarctic expedition (2005)(2006). The CN concentration reached a maximum in the summer, although the number concentrations of fine particles (D p >0.3 µm) and coarse particles (D p >2.0 µm) increased during the winterspring. The CN concentration was 30-2200 cm −3 near the surface (surface -500 m) and 7-7250 cm −3 in the lower free troposphere (>1500 m). During the austral summer, higher CN concentration was often observed in the lower free troposphere, where the number concentrations in fine and coarse modes were remarkably lower. The frequent appearance of higher CN concentrations in the free troposphere relative to continuous aerosol measurements at the ground strongly suggests that new particle formation is more likely to occur in the lower free troposphere in Antarctic regions. Seasonal variations of size distribution of fine-coarse particles show that the contribution of the coarse mode was greater in the winterspring than in summer because of the dominance of sea-salt particles in the winter-spring. The number concentrations of fine and coarse particles were high in air masses from the ocean and mid-latitudes. Particularly, aerosol enhancement was observed not only in the boundary layer, but also in the lower free troposphere during and immediately after Antarctic haze events occurring in May, July and September.