[in Japanese]

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Rare earth elements (REEs) are essential and widely used in of high-technology industries all over the world. However, almost of them produced in the world are mined in China. The concentrations of the REEs (La-Lu) in the PM_2.5 are rarely reported in China and Japan. We conducted simultaneous observations of PM_2.5 at Beijing, Shanghai, Shinjuku and Kazo in August 2013, and evaluated all the data including those published in Beijing in January 2013. As the results, when compared with metalic elements between Beijing and Shanghai, the relative concentrations of the elements originatting from shipping, oil combustion and the steel industry were dominant in Shanghai. Those of coal combustion were dominant in Beijing. The enrichment factor of the REEs in PM_2.5 at Beijing calculated based on the REEs in PM₁₀ at Bayan obo, the largest mine in China, showed that neodymium (Nd) and dysprosium (Dy) were significantly higher than the others. Those of erbium (Er) and ytterbium (Yb) were also high. The combination of enriched REEs in the PM_2.5 provides information about the products and industries of high-technology.

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The Kyushu area was covered by a long lasting (～7 days) yellow sand and high concentration of air pollution from late May to early June 2014. This episode originated by the two dust events that occurred in the inland desert area of China, then the long-range transported dust and air pollutants are trapped under the blocked high pressure system. Intensive field observations based on the advanced aerosol measurement instruments placed at Kyushu University (Chikushi Campus) successfully observed the physical and chemical changes of this long-lasting episode and simulated by the GEOS Chem chemical transport model (CTM). The CTM reproduced the time variation of the SO₄^2- and NH₄⁺quite well, however, the modeled NO₃^- variation showed an unrealistic diurnal variation that is related to the gas-aerosol equilibrium module and meteorological parameters. The model sensitivity experiment and observational data analysis showed that 88% of the SO₄^2- was transported from outside of Japan. We confirmed that the coarse-mode NO₃^- had an elevated concentration during the first stage of the yellow-sand transport period, and 70–80% of this elevated tNO₃ was transported from outside Japan.

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Using a quartz fiber filter for the PM_2.5 carbonaceous measurement causes the adsorption of gaseous organic carbon (OC_G) and overestimation of particulate OC (positive artifact). In this study, the filter sampling with and without an activated carbon denuder was simultaneously carried out in Kazo, Saitama Prefecture and the magnitude of the OC_G adsorption and its seasonal variation were investigated. The seasonal averages of OC_G ranged from 0.26 μg/m³ (autumn) to 0.42 μg/m³ (winter), and the differences between the seasons were small. About 70 to 90% of the OC_G exist in the OC1 and OC2. The ratio of OC_G in the OC without a denuder was higher when the OC was below 2 μg/m³, and thus the positive artifact became higher in the low OC concentration. Regarding the ratio of OC_G in the OC for each fraction, OC1 was higher than the other fractions, but OC2 was also higher. As a trial, in order to estimate the influence of the OC_G on the measured OC without a denuder, the formula that calculate the ratio of OC_G in the OC from the OC was developed based on the results of this study.

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To investigate the aerosol chemistry in Yamanashi Prefecture, observations of the aerosols and their precursor gases were conducted over a three-year period at a residential site close to central Kofu. When compared with the results from other residential areas around Yamanashi Prefecture, ionic species, especially NO₃^- and NH₄⁺, showed lower concentrations, but the carbonaceous species were relatively enriched in the PM₂ at Kofu. Organic matters, soil/mineral components, and nss-SO₄^2- were the main components of the PM₁₀. The mass ratio of PM₂/PM₁₀ was 63.6% on average. The most important contributor to the PM₂ mass was organic matters with high concentrations in winter. They would be mainly derived from vehicle exhausts and biomass burning, but photochemical productions would also be important in summer. Secondly, nss-SO₄^2- had a large contribution to the PM₂ mass with high concentrations in summer due to photochemical productions. Soil/mineral components were the most important for the PM_10–2 mass and increased in spring due to Kosa events. The second most important component of the PM_10–2 was organic matters from biomass burning and plant debris. Except for nss-Ca²⁺and NO₃^-, no effect of long-range transports from the Asian continent on the concentrations was found in the chemical components of the aerosols at Kofu.

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