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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.

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.

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.

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

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 (

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 (

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.

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 FROM AUTHOR]

The aerosol optical characteristics in the East Asian cities of Fukuoka and Beijing were measured from 2010 to 2014. These long-term season-crossing data were compared to understand the differences between the aerosol characteristics at a source and a downstream region. Previously, few long-term, season-crossing observations have been reported. Using a method developed by one of the present authors, the measurement data were analyzed so that the retrieved optical properties can be more accurate than those obtained in previous studies. Using these data, the aerosol characteristics and their frequency distributions were reliably obtained. In Fukuoka, the annual means of the extinction, scattering, and absorption coefficients Cext (525 nm), Csca (525 nm), and Cabs (520 nm) were 74.6, 66.1, and 8.1 Mm-1, respectively, whereas those in Beijing were 412.1, 367.2, and 42.4 Mm-1, respectively. The coefficients in Fukuoka were approximately one-fifth of those in Beijing. The single-scattering albedos ω0 (525 nm) in Fukuoka and Beijing were 0.877 and 0.868, respectively. The asymmetry factors G (525 nm) in the two cities were 0.599 and 0.656, respectively. The extinction Ångström exponents αext in the two cities were 1.555 and 0.855, respectively. The absorption Ångström exponents αabs in the two cities were 1.106 and 0.977, respectively. The fine- and coarse-mode volume fractions in Fukuoka were approximately 80 % and 20 %, and those in Beijing were both approximately 50 %, except in summer. Cext, Csca, and Cabs showed a seasonal variation in both cities. Some other properties also showed a seasonal variation. In particular, the seasonal variation in α abs was clear in both cities; it tended to be small in summer and large in winter. The frequency distributions of various parameters were also investigated. The frequency of Cext > 500 Mm-1 in Fukuoka was very low, and large Cext values were recorded more frequently in spring than in other seasons. In Beijing, Cext > 1000 Mm-1 values were recorded more frequently, and the frequency of 10 Mm-1 £ Cabs £ 60 Mm-1 was high in spring and summer. Furthermore, αabs < 1.0 values were recorded frequently, which cannot be explained by the simple external mixture of absorbing aerosols. To demonstrate the usefulness of the data obtained in this study, the relationships among αabs, αext, the volume size distribution, the imaginary part of the refractive index, and ω0 were investigated, and two characteristic cases in Beijing (winter) and Fukuoka (spring) were preliminarily analyzed. [ABSTRACT FROM AUTHOR]