[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.

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[1] Seasonal changes in the vertical structure of free tropospheric aerosols over east Asia, on the basis of aircraft-borne and lidar measurements, and on the pathway of the longrange transport of Asian dust particles inferred from isentropic trajectory analysis are discussed. Aircraft-borne measurements held in situ in the free troposphere over central Japan in 2000-2001 revealed a small in scale yet steady transport of dust in the lowermiddle free troposphere (2-6 km altitude) during spring including days with no evident dust outbreak. Such dust, found as background, was observed even in summer in the regions higher than 4 km under the influence of remaining westerly winds but not in the lower regions. From a series of lidar observations over Nagoya (35°N, 137°E), Japan, noticeable changes in aerosol characteristics were obtained in the free troposphere from spring to summer. Taklimakan desert is suggested as possible important source of the background dust.

Deposition of water‐insoluble dust was measured in winter snow deposited at Murododaira (2450 m) on the western flank of Mount Tateyama in central Japan. An analysis of temporal variation in atmospheric aerosol concentration, incremental snow height and concentration of dust in the snow cover suggests that wet deposition is the major process in forming thicker dust layers in the snow cover at Mount Tateyama. Dust layers in the snow cover contain Ca‐rich materials typically found in Asian dust (Kosa) particles. Volume size distributions of dust particles in the snow showed single and bi‐modal structures having volume median diameters from 6–21 μm. Dust profiles in snow cover over the last 6 yr reveal frequent sporadic high dust concentrations in spring and large year‐to‐year variations in the amount deposited. The average amount of dust deposition (7.7 g m−2) from winter to spring at the site was close to the long‐term averages of annual flux obtained from sea sediment near Japan, implying that dusty precipitation in spring contributes to annual deposition of aeolian mineral dust.

This study focuses on providing a direct insight into the process by which sulfate is formed on mineral dust surface in the actual atmosphere. Six sets of aerosol measurements were conducted in the outskirts of Beijing, China, in 2002-2003 using a tethered balloon. The mineralogy of individual dust particles, as well as its influence on the S (sulfur) loadings was investigated by SEM-EDX analysis of the directly collected particles.The mixed layer in the urban atmosphere was found to be quite low (500-600 m), often appearing as a particle dense stagnant layer above the surface. It is suggested that mineral dust is a common and important fraction of the coarse particles in Beijing (35-68%), and that it is relatively enriched with Calcite (>28%).An exceptional amount of S was detected in the mineral particles, which can be explained neither by their original composition, nor by coagulation processes between the submicron sulfates and the dust. Heterogeneous uptake of gaseous SO 2 , and its subsequent oxidation on dust was suggested as the main pathway that has actually taken place in the ambient environment. The mineral class found with the largest number of particles containing S was Calcite, followed by Dolomite, Clay, Amphibole etc., Feldspar, and Quartz. Among them, Calcite and Dolomite showed distinctly higher efficiency in collecting sulfate than the other types.A positive correlation was found with the number of S containing particles and the relative humidity. Calcite in particular, since almost all of its particles was found to contain S above 60% r.h. On the other hand, the active uptake of SO 2 by the carbonates was not suggested in the free troposphere downwind, and all the mineral classes exhibited similar S content. Relative humidity in the free troposphere was suggested as the key factor controlling the SO 2 uptake among the mineral types. In terms of sulfate loadings, the relationship was not linear, but rather increased exponentially as a function of relative humidity. The humidity-dependent uptake capacity of mineral types altogether showed an intermediate value of 0.07 gSO 2− 4 g −1 mineral at 30% r.h. and 0.40 gSO 2− 4 g −1 mineral at 80%, which is fairly consistent with laboratory experiments.