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Abstract The valence state and concentration of metallic pollutants are important factors contributing to the health effects of respirable particulate matter (PM); however, they have not been well studied. In this study, coarse and fine powder samples of atmospheric PM were collected using a cyclone system at Kanagawa (KO), Saitama (SA), and Fukuoka (FU) in Japan in 2017. Energy dispersive X-ray fluorescence spectroscopy (EDXRF) was used to measure the concentrations of nine metallic elements (Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, and Pb), and X-ray absorption fine structure (XAFS) spectroscopy was used to analyze the valence states of target elements (Cr, Mn, Fe, Cu, and Zn). The EDXRF results indicated that the average contents of Fe, Ti, and Zn were much higher than those of the other six elements in all samples. The XAFS results showed that the major valence states of the elements were Cr(III), Mn(II), Fe(III), Cu(II), and Zn(II). The percentages of Mn(IV), Fe(II), and Cu(0) were higher in KO and SA samples than in FU samples. Mn(0) and Zn(0) were detected in some samples only, and Cu(I) was not detected in any samples. Correlation analysis, principal component analysis, and cluster analysis were performed on the EDXRF and XAFS data of the target elements. The source identification results showed that the sources of metal contaminants in the samples varied considerably between sampling sites and depended on the industrial structure and geographical location of the sampling area. Our findings on the different valence states of the elements may be important for determining the toxicity of PM at different locations.

Abstract Oxidative stress is a mechanism that might raise the toxicity of mineral dust aerosols. We evaluated the oxidative potential (OP) of four reference materials (RMs) of mineral dusts using dithiothreitol assay. The OP of the water‐soluble fraction of the dust RMs accounts for 40%–70% of the OP of the total fraction. The values of total and water‐soluble OP normalized by the surface area of insoluble particles showed agreement among the different dust RMs. The surface area of insoluble dust particles was therefore inferred as an important factor affecting the OP of mineral dust. Using the relation between total OP and the surface area of insoluble particles of the dust RMs, we estimated the total OPs of fine and coarse atmospheric mineral dust aerosols assuming a typical particle size distribution of Asian dust aerosols observed in Japan. Mass‐normalized total OPs were estimated at 44 and 23 pmol min−1 μg−1 for fine and coarse atmospheric mineral dust particles. They closely approximate the values observed for urban aerosols in Japan, which suggests that mineral dust plume advection can lead to a marked increase in human exposure to redox‐active aerosols, even far downwind from mineral dust source regions.

A series of 3,6-diamino-9-naphthylcarbazole derivatives were synthesized and characterized experimentally and computationally. As the lowest unoccupied molecular orbital of the naphthyl group has lower energy than that of the phenyl group, a charge transfer from carbazole to naphthyl in the excited states occurred causing solvatofluorochromism and solvent-dependency in fluorescence quantum yields. A molecule having two carbazole substituents sandwiching the central naphthyl ring had absorption reaching 470 nm and a high reducing capability in the excited state. This molecule could successfully photosensitize the hydrodehalogenation of haloarenes under visible light irradiation.

We aim to clarify the link between mass accretion and ejection by analyzing DG Tau’s jet observations from optical and near-infrared data spanning 1984–2019, alongside photometric variations between 1983 and 2015. We classified 12 moving knot groups among 17 total knot groups based on their constant proper motions and comparable radial velocities. A strong correlation emerges between the deprojected flow velocities of the knots and the photometric magnitudes of DG Tau. From 1983 to 1995, as the deprojected ejection velocities surged from ∼273 ± 15 to ∼427 ± 16 km s ^−1 , the photometric magnitudes ( V ) concurrently brightened from 12.3 to 11.4. Notably, when DG Tau became brighter than 12.2 in the V band, its ( B − V ) color shifted bluer than its intrinsic color range of K5–M0. During this period, the launching point of the jet in the protoplanetary disk moved closer to 0.06 au from the star in 1995. Following a V magnitude drop from 11.7 to 13.4 in 1998, the star may have experienced significant extinction due to a dust wall created by the disk wind during the ejection of the high-velocity knot in 1999. Since then, the magnitude became fainter than 12.2, the ( B − V ) and ( V − R ) colors became redder, and the deprojected velocities consistently remained below 200 km s ^−1 . The launching point of the jet then moved away to ∼0.45 au by 2008. The prevailing factor influencing photometric magnitude appears to be the active mass accretion causing the variable mass ejection velocities.

Abstract We evaluated the effects of ambient particulate matter (PM) on the corneal epithelium using a reconstructed human corneal epithelium (HCE) model. We collected two PM size fractions [aerodynamic diameter smaller than 2.4 µm: PM0.3–2.4 and larger than 2.4 µm: PM>2.4] and exposed these tissues to PM concentrations of 1, 10, and 100 µg/mL for 24 h. After exposure, cell viability and interleukin (IL) IL-6 and IL-8 levels were determined, and haematoxylin and eosin and immunofluorescence staining of the zonula occludens-1 (ZO-1) were performed on tissue sections. In addition, the effects of a certified reference material of urban aerosols (UA; 100 µg/mL) were also examined as a reference. The viability of cells exposed to 100 μg/mL UA and PM>2.4 decreased to 76.2% ± 7.4 and 75.4% ± 16.1, respectively, whereas PM0.3–2.4 exposure had a limited effect on cell viability. These particles did not increase IL-6 and IL-8 levels significantly even though cell viability was decreased in 100 μg/mL UA and PM>2.4. ZO-1 expression was reduced in a dose-dependent manner in all groups. Reconstructed HCE could be used as an in vitro model to study the effects of environmental PM exposure on ocular surface cell viability and inflammation.

A novel aerosol observation and sampling system has been developed by combining a rubber balloon and an unmanned aerial vehicle (UAV). The system takes advantage of the feature of an observation method using a rubber balloon, which is handy, inexpensive, and higher reachable observation altitude than those of other observation methods, and the feature of a UAV which can fly back to the released point autonomously. In this system, an optical particle counter, an aerosol sampler, and a GPS sonde are mounted on a motor-glider UAV. The UAV, which is suspended from a rubber balloon, is released from the ground. After finishing observation and sampling during its ascent, the UAV is recovered by separating from the balloon and gliding back to the released point autonomously. Five observation flights were performed successfully at Syowa Station in the summer activity of the 54th Japanese Antarctic Research Expedition, and the maximum observation and separation altitude reached 10 km. Number concentrations obtained by insitu measurements and morphology of recovered aerosols using the UAV show the possibility that the enhancement of sulfate aerosols in the free troposphere and bottom of the stratosphere were caused by the volcanic eruption in the mid-latitude in January 2013.

Abstract Oxidative potential is an important property of particulate matter (PM) that has been regarded as a more health‐relevant metric than PM mass. We investigated the oxidative potential of size‐segregated PM and effects of Asian dust events in Fukuoka, western Japan. Aerosol particles with diameters smaller and larger than 2.5 μm (fine and coarse particles, respectively) were collected continually from 16 March through 26 May 2016. The oxidative potential was analyzed using dithiothreitol (DTT) assay; chemical components of PM were also found. Air‐volume normalized oxidative potential quantified by DTT assay (DTTv) was significantly higher during Asian dust events than during nondust‐event days. The mean DTTv of fine and coarse particles during Asian dust events were, respectively, 1.5 and 2.7 times higher than that during nonevent days. DTTv of fine particles was highly correlated with elements dominated by anthropogenic combustion sources and with the elements emitted from multiple sources including mineral dust and combustion sources. DTTv of coarse particles strongly correlated with the mineral dust derived elements, suggesting concentration of mineral dust particles as an important controlling factor especially for the oxidative potential of the coarse particles. We estimated the contributions of water‐soluble transition metals to the oxidative potential of PM. Water‐soluble transition metals (mainly Cu and Mn) can explain only approximately 37% and 60% of the measured oxidative potential of fine and coarse particles, respectively, suggesting substantial contributions of aerosol components other than water‐soluble transition metals such as quinones and insoluble minerals.

Local fronts, such as sea-breeze and land-breeze fronts, play an important role not only from a meteorological aspect but also for pollutant transport and mixing, in urban areas in particular. Due to the difficulty of measuring three-dimensional (3-D) wind fields, there are few studies focusing on short-term fine-scale spatial and temporal variations in aerosol and gas compositions associated with local front passage. At the end of November 2016, a 3-D coherent Doppler lidar was installed in Fukuoka city (33.55°N, 130.37°E), an urban area in Japan, and 3D-wind fields have been continuously measured since then. Two local fronts with typical density current structure were observed on 3 May and 29 June 2017. On 3 May 2017, there was a stepwise increase in concentrations of aerosol (particularly smaller size aerosol), black carbon (BC) and carbon monoxide (CO), supposedly of surface origin, at the passage of the local front. However, O3 content, which can be higher at higher altitudes, decreased. In another case on 29 June 2017, there was light rain in the early morning and all gas and aerosol contents were low before the passage of the front. At the front passage, there was a stepwise increase in aerosol, BC and CO contents as on 3 May, although O3 content gradually increased after sunrise and no clear change was observed in O3. Vertical aerosol observations by the Doppler lidar indicate that the depth of the front system on 29 June was much thinner (up to 300–400 m) than that on 3 May (up to ∼700 m), and the temperature decrease was larger than on 3 May. These facts suggest that the mixing of air masses within the system with those above or ahead of the system on 29 June was no stronger than on 3 May, and thus the aerosol and gas contents at the ground may be strongly affected by the vertical mixing/dilution of the system as well as by local emission.

Transboundary air pollution (TAP) and local air pollution (LAP) influence the air quality of urban areas. Fukuoka, located on the west side of Japan and affected by TAP from the Asian continent, is a unique example for understanding the contribution of LAP and TAP. Gaseous species and particulate matter (PM) were measured for approximately three weeks in Fukuoka in the winter of 2018. We classified two distinctive periods, LAP and TAP, based on wind speed. The classification was supported by variations in the concentration of gaseous species and by backward trajectories. Most air pollutants, including NOx and PM, were high in the LAP period and low in the TAP period. However, ozone was the exception. Therefore, our findings suggest that reducing local emissions is necessary. Ozone was higher in the TAP period, and the variation in ozone concentration was relatively small, indicating that ozone was produced outside of the city and transported to Fukuoka. Thus, air pollutants must also be reduced at a regional scale, including in China.

Tethered balloon-borne aerosol measurements were carried out at Syowa Station, Antarctica during the 46th Japanese Antarctic Research Expedition. CN concentration had a maximum in the summer, whereas the number concentrations of fine particles (D_p>0.3 μm) and coarse particles (D_p>2.0 μm) increased during the winter-spring. The range of CN concentration was 30-2200 cm^ near the surface (surface-500 m) and 7-7250 cm^ in the lower free troposphere (>1500 m). During the austral summer, higher CN concentration was often observed in the lower free troposphere. Frequent appearance of higher CN concentration in the free troposphere relative to the surface measurements strongly suggests that new particle formation in the Antarctic regions occurs in the lower free troposphere. Single particle analysis indicated that most of the aerosol particles during the winter were composed of Mg-enriched sea-salt particles originated from sea-salt fractionation on the sea-ice and their modified particles by NO_3^ and SO_4^. This suggests that sea-salt fractionation on sea-ice and modification of sea-salt particles were affected greatly by aerosol hygroscopicity during the winter. Antarctic haze layer was observed not only in the boundary layer but also in the lower free troposphere.

To investigate spatial and temporal variation of number-size distribution of atmospheric aerosol particles in the Antarctic Ocean, atmospheric observations were conducted on research vessels: Hakuho-maru, Tangaroa, and Umitaka-maru. Concentrations of ionic constituents in aerosols and precursor gases (SO_2 and NH_3) were also measured during the cruises. Concentrations of nucleation mode particles (

Number-size distributions (D_p>0.3 μm) of atmospheric aerosol particles were measured at Syowa Station, Antarctica, from February 2004 to January 2006. Volume concentrations of coarse particles (D_p 1.0-5.0 μm) were low in December to January and high in the rest of the year. To identify factors controlling the seasonal variation of coarse particle concentrations at Syowa Station, seasonal variations of wind speed distribution over the Southern Ocean, sea ice extent, wind speed at the edge of sea ice and at Syowa Station, and seasonal patterns of backward air trajectories were compared with the volume concentrations of coarse particles. Patterns of backward air trajectories and changes in size distributions of coarse particles associated with sea ice extent suggest changes in major source areas of sea salt particles observed at Syowa Station: coastal areas near Syowa in February and March, but far north of the sea ice edge, around 60゜ south, in October.

The Size distribution and volatility of ultrafine aerosol particles were measured at Syowa Station during the 46-47 Japanese Antarctic Research Expeditions. During the summer, most of the ultrafine particles were volatile particles, which were composed of H_2SO_4, CH_3SO_3H and sulfates bi-sulfates. The abundance of non-volatile particles was ～ 20% during the summer, increasing to>90% in winter-spring. Non-volatile particles in winter were dominantly sea-salt particles. Some ultrafine sea-salt particles might be released from sea-ice. When air mass was transported from the free troposphere over the Antarctic continent, the abundance of non-volatile particles dropped to

Simultaneous observations of the aerosol size distribution for diameters of 0.003-5.0 μm were performed at Syowa Station (69゜00′S, 39゜35′E, 15 m a.s.l.) and Dome Fuji Station (77゜19′S, 39゜42′E, 3810 m a.s.l.) in Antarctica from February 1997 to January 1998. Size distributions show composites of a small-Aitken mode (less than 0.05 μm in diameter), a large-Aitken mode (0.05-0.3 μm in diameter), and a large giant particle mode (larger than 0.3 μm in diameter). Concentrations of small and large Aitken modes were high in summer and low in winter. On the other hand, concentrations of large giant particle mode were low in summer and high in winter. The high and or low concentration events for one or a few days in whole size range were observed especially in winter. High concentration events in small Aitken mode with the low concentrations in diameter of 0.07-5.0 μm were also observed at Dome Fuji Station in spring. Meteorological conditions during the events at Dome Fuji Station were different from those at at Syowa station.

Balloon borne aerosol sonde observation and lidar observations were preformed at Ny-Alesund, Norway in the winters of 2002 03 and 2007 08. In the winter of 2002 03, the aerosol layers with the increment of depolarization ratio were observed at the lower stratosphere below 15 km height by lidar. The effective radius of stratospheric aerosol estimated from aerosol sonde observations showed high values of 0.17-0.24 μm in radius in the height range. The temperature in the height range was remarkably higher than the formation temperature of polar stratospheric cloud (PSC). The depolarized aerosol layer might be volcanic aerosol by the eruption of Mt. El Reventador. The average value of effective radius of stratospheric aerosol in the height range of 10-25 km was estimated to be 0.12 μm. In the winter of 2007 08, PSC events were frequently detected. Both solid and liquid PSC detected by lidar on January 9, 2008 showed that they experienced almost the same temperature history. They might be affected by meso-scale temperature perturbations such as gravity waves.

Number-size distributions (5-168 nm in diameter) of atmospheric aerosol particles were measured at Syowa Station, Antarctica from February 2004 to January 2005. Size distributions in winter consisted of 1 to 2 modes larger than 50 nm in diameter, whereas 2 to 3 modes contributed to the size distributions in October to March with mode diameters between 20 and 80 nm. Size distribution with a valley at around 50 nm was often observed in summer to fall when the open ocean was located near Syowa Station. From September to March, concentration of ultra fine particles (

Measurement of atmospheric black carbon (BC) was carried out at Syowa Station Antarctica (69゜00′S, 39゜35′E) from February 2004 until January 2007. The BC concentration at Syowa Station ranged from below detection to 176 ng m^. Higher BC concentrations were observed frequently from April until October. Increase of BC concentration may be associated with poleward flow due to the approach of a cyclone and or blocking event during winter-spring. The BC-rich air masses traveled through the lower troposphere from the Atlantic and Indian Oceans to Syowa (Antarctic coast). During the summer (November-February), the BC concentration showed a diurnal variation together with surface wind speed and increased in the presence of katabatic wind from the Antarctic continent. Considering the low BC source strength over the Antarctic continent, the higher BC concentration in the continental air (katabatic wind) might be caused by long range transport of BC via the free troposphere from mid- and low- latitudes. The seasonal variation of BC at Syowa Station had a maximum in July-September, while at the other coastal stations (Halley, Neumayer, and Ferraz) and a continental station (Amundsen-Scott), the maximum occurred in October. This difference may result from different transport pathways, significant contribution of source regions and scavenging of BC by precipitation during the transport from the source regions. During the austral summer, long-range transport of BC via the free troposphere is likely to make an important contribution to the ambient BC concentration along the Antarctic coasts.

Observations of aerosol constituents and acidic gases were carried out at Syowa Station (1997-1998 and 2003-2006; JARE-38～ 39, and JARE-44～ 47) and Dome Fuji Station (1997, JARE-38). Seasonal variations and size distribution of sea-salt particles were compared between coastal and inland stations. Seasonal variations of the concentrations of sea-salt particles showed a minimum in the austral summer and higher during the winter at both stations due to strong winds and long-range transport. Sea-salt particles were mostly distributed in fine (D_p: 0.2-2.0 μm) and ultra-fine (D_p and below the detection limit (BDL)-1.5 nmol m^, respectively. Sea-salt fractionation (SO_4^ depletion) due to Mirabilite formation was identified not only at Syowa Station but also at Dome Fuji Station. Seasonal variation of molar ratio of Mg^ Na^+ showed higher ratios at lower temperature. The range and temperature dependence of Mg^ Na^+ strongly suggested that other sea-salt fractionation (e.g., formation of gypsum and hydrohalite) occurred in the Antarctic coasts in addition to Mirabilite formation. Because of different seasonal variation and range of Mg^ Na^+ between Dome Fuji and Syowa Stations, sea-salt fractionation may proceed even in the inland area.

Surface ozone concentration decreased dramatically from 28 to 29 August 1997 at Syowa Station, Antarctica. Aerosol concentrations with diameters of 0.01-5.0 μm increased to several times as much as background concentrations, accompanied with the surface ozone depletion. Air mass above Syowa Station in SOD events had high humidity and low ozone concentration. The SOD also accompanied change of wind direction, and the results of backward trajectory analysis suggested that this air mass was transported from the westerly sea ice area of a cold front within several days. These results suggested that the SOD on 28 29 August 1997 at Syowa Station occurred by transport of the air mass.

During our aerosol measurement program at Syowa Station, Antarctica in 2004-2007, some low visibility (haze) phenomena were observed under conditions with weak wind and without drifting snow and fog in winter-spring. In the "Antarctic haze" phenomenon, the number concentration of aerosol particles and black carbon concentration increased by one-two orders higher relative to background conditions at Syowa Station, while surface O_3 concentration simultaneously dropped especially after polar sunrise. Major aerosol constituents in the haze phenomenon were sea-salts (e.g., Na^+ and Cl^-). From the trajectory analysis and NAAPS model, the plumes from biomass burning in South America and southern Africa were transported to Syowa Station, Antarctic coast, during eastward (occasionally westward) approach of cyclones in the Southern Ocean. Thus, poleward flow of the plume from mid-latitudes and injection of sea-salt particles during the transport may lead to the Antarctic haze phenomenon at Syowa Station. The difference of O_3 concentration between the background and the haze conditions tended to be larger in spring (polar sunrise) relative to that in winter. Because enhancement of sea-salt particles can play an important role as an additional source of reactive halogen species, the haze episodes might make a significant contribution to surface O_3 depletion during the polar sunrise on the Antarctic coast.

Concentrations of condensation nuclei (>0.01 μm in diameter) and of aerosol particles larger than 0.3 μm in diameter were monitored at Syowa Station from February, 1996. Number concentrations of condensation nucleus were high in summer and low in winter. Concentrations increased at the rate of several partcles cm^3 per year. On the other hand, the concentrations of fine particles (>0.3 μm) and coarse particles (>1.0 μm) were low in summer and high in winter. Concentrations of fine particles 0.3 μm and larger after July were double those before July.

This report summarizes observations of tropospheric and stratospheric aerosols by a balloon-borne optical particle counter (Aerosol sonde) performed at Syowa Station from April 1997 to January 2008. Typical seasonal changes in the stratospheric aerosol layer were characterized by sedimentations of the stratospheric aerosol layer in autumn, PSCs activity in winter, and sudden increase in aerosol concentration at the end of spring. The annual change shows that the perturbations of stratospheric aerosol caused by the eruption of Mt. Pinatubo in 1991 remained until 1999. Additionally, seasonal variation of tropospheric aerosol shows clear differences between concentrations from January to June and those from July to December.

Aerosol size and number concentration were observed in the atmospheric boundary layer over Beijing (from near the ground to 1,200 m) on March 15 (a clear day) and 16 (a dusty day), 2005. The results were further compared with lidar measurements in order to understand the dependency of extinction on the particle size distribution and their vertical changes. The boundary layer atmosphere was composed of several sub-layers, and a dry air layer appeared between 400 and 1,000 m under the influence of dust event. In this dry air layer, the concentration of the fine-mode particles (diameter smaller than 1.0 μm) was slightly lower than the value on the clear day, while the concentration of coarse-mode particles (diameter larger than 1.0 μm) was remarkably higher than that on the clear day. This situation was attributed to the inflow of an air mass containing large amounts of Asian dust particles and a smaller amount of fine-mode particles. The results strongly suggest that the fine-mode particles affect light extinction even in the dusty atmosphere. However, quantitatively the relation between extinction and particle concentration is not satisfied under the dusty atmospheric conditions since laser beam attenuates in the atmosphere with high concentration of particles. Laser beam attenuation effect becomes larger in the relation between extinction and coarse particle content comparing the relation between extinction and fine particle content. To clarify this problem technically, future in situ measurements such as balloon-borne lidar are suggested. Here extinction was measured at 532 nm wavelength. Measurements of extinction at other wavelengths are desired in the future.

A variety of heteroaromatic compounds, such as substituted pyridines, pyrazoles, indoles, 2-substituted imidazoles, 2-substituted imidazoles, 2-arylbenzazoles and pyrimidin-2(1H)-ones are synthesized by oxidative aromatization using the activated carbon and molecular oxygen system. Mechanistic study focused on the role of activated carbon in the synthesis of 2-arylbenzazoles is also discussed. In the final section, we will disclose the efficient synthesis of substituted 9,10-anthracenes via oxidative aromatization.

An observatory (19m^2 inside area) was built for monitoring clean air constituents, such as aerosol particles and ozone, near the core block of Syowa Station. The observatory is located about 300m windward of the main buildings of Syowa Station to reduce atmospheric contamination from an electric power plant and other station activities. Continuous observations of aerosols and surface ozone started on February 10, 2004. The observatory uses electric heaters and outside cool air to control room temperature at about 20°C ±3°C to avoid self contamination by heating fuel combustion. The observatory has a 6-m height tower for an air inlet system that connects to an aerosol sub-sampling line under constant laminar air flow condition. Comparison of aerosol data between the Kansokutou (Atmospheric Observatory in the main station area) and this new observatory from February 2004 to January 2005 suggests that the effectiveness for monitoring clean air was improved about 10%.

Observation of the ambient aerosol surface area concentrations is important to understand the aerosol toxicity because an increased surface area may be able to act as an enhanced reaction interface for certain reactions between aerosol particles and biological cells, as well as an extended surface for adsorbing and carrying co-pollutants that are originally in gas phase. In this study, the concentration of aerosol surface area was measured from April 2015 to March 2016 in Fukuoka, Japan. We investigated the monthly and diurnal variations in the correlations between the aerosol surface area and black carbon (BC) and sulfate concentrations. Throughout the year, aerosol surface area concentration was strongly correlated with the concentrations of BC, which has a relatively large surface area since BC particles are usually submicron agglomerates consisting of much smaller (tens of nanometers) sized primary soot particles. The slopes of the regression between the aerosol surface area and BC concentrations was highest in August and September 2015. We presented evidence that this was caused by an increase in the proportion of airmasses that originated on the main islands of Japan. This may enhance the introduction of the BC to Fukuoka from the main islands of Japan which we hypothesize to be relatively fresh or “uncoated”, thereby maintaining its larger surface area.

With a newly developed automatic measurement system, the partial pressure of CO_2 in the surface sea water and lower troposphere were continuously monitored on board the icebreaker SHIRASE between Japan and Antarctica from November 1987 to March 1992 as a part of the Japanese Antarctic Research Expedition (JARE). The atmospheric CO_2 concentration was high in the midnorthern hemisphere, decreased rapidly southward to a minimum in the midsouthern hemisphere, and increased slightly in the Antarctic region. Water mass differences in the western North Pacific and eastern Indian Ocean can be seen in diagrams which consists of CO_2 partial pressure in surface sea water (pCO_2) and sea surface temperature (SST). These water masses are bordered at the boundaries of major oceanic currents : the southern border of the Kuroshio Countercurrent (28°N), the southern border of the Subtropical Countercurrent (20°N), the southern border of the North Equatorial Current (6°N), the southern border of the Celebes Sea, and the Lombok Strait. The relations between pCO_2 variations and hydrographic conditions such as the effect of coastal water and upwelling are subject to discussion in this report. Meridional distributions of pCO_2 and SST south of 35°S obtained in the southward cruise on 110°E in December, the northward cruise on 150°E in March, and the cruise between Syowa Station (69°00′S, 39°35′E) and Cape Town in January 1989 clearly show steep changes at the Subtropical Convergence, Subantarctic Front, and Polar Front. Even if pCO_2 within each water mass distributed between the fronts varies to some extent, each water mass can be distinguished from the other masses by the differences of average pCO_2 and SST. Longitudinal distributions of pCO_2 and SST measured in the westward track from 110°E to 20°E along 59°S to 61°S and the eastward track from 40°E to 150°E along 61°S to 65°S are scattered between 320μatm and 360μatm. However it is clearly evident that the pCO_2 dips by 50μatm between 80°E and 110°E. Anticyclonic eddies which are already found in the region could drive coastal water, which has less pCO_2 because of high productivity, northward. The partial pressure difference between air and surface sea water (△pCO_2) and CO_2 flux across the air-sea boundary was calculated to estimate the CO_2 source/sink strength of the ocean along the track. The region between the Subantarctic Front and the Polar Front, and the region south of the Polar Front, which are regarded as a data void region, are very weak CO_2 sources as well as very weak CO_2 sinks and weak CO_2 sinks by 0 to -5mol・m^・yr^, respectively.