The Intake Fraction (iF) is the ratio of the cumulative mass inhaled by the exposed population to the cumulative emission. It has been proposed as a measure that can facilitate the establishment of measures and decision making for pollution control. Many iF studies, especially about the atmospheric environment, have been mainly carried out in the United States and Europe until now, while little is known about the iF in Japan. We examined the definition and characteristics of iF, along with introducing some case studies. The emission and intake/inhalation were mainly estimated based on the existing emissions inventory and using the atmospheric dispersion model, respectively. It is expected that iF can be used for considering the local pollution control due to automobile exhaust and for other environmental problems in Japan in the near future, even though it is necessary to consider methodological issues such as how to estimate the concentration emitted from a specific source.

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We studied Asian scale source-receptor (S-R) relationship based on the tagged CO tracer model. GEOS Chem (Version 9-1-1) was used with a high-resolution Asian domain (0.5˚ x .667˚ resolution) 1-way nested to the global domain. A ten-tagged region was set in the Asian region. The model results showed a good agreement with the surface CO measurements (Yonaguni (YON), Ryori (RYO) and Minami-Torishima (MNM)) and the MOPITT satellite CO measurement. Intermittent CO peaks were well simulated during the winter to spring seasons both at YON and RYO, and its daily averaged concentration ranged from 200 - 300 ppbv. Numerical model also showed low summertime CO concentration below 100 ppbv. The annual averaged CO concentration over the Central-East China (CEC) region reached 500 ppbv. A S-R analysis showed that more than 80 % of the CO was coming from Chinese domestic emissions in that region. The fraction of CO due to the Chinese emission was 50% over the Korea and 35 - 40 % over the Japan region. An analysis of the seasonal variation indicated that the CO originated from China mainly dominated in the winter-spring seasons, while the non-Asian source and natural VOC origin CO showed a relatively high fraction in the summer season.

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We studied Asian scale CO source-receptor (S-R) relationship from 2004-2011 based on the tagged CO tracer model. GEOS Chem (Version 9-1-1) was used with a high-resolution Asian domain (0.5˚ x 0.667˚ resolution) which was 1-way nested into the global domain. Ten tagged regions were set within the Asian region. The REAS2.0 emission inventory was used as the Asian anthropogenic emission. The model results were compared with 6 ground base station and MOPITT satellite retrieval data. The model results showed clear year-by-year variations, and showed a reasonable agreement with the observations. For the observation sites within the Asian domain, the impact from the Chinese CO emission was dominant and we successfully summarized the relationship between the CO emission from the tagged regions and corresponding CO contribution from each receptor site. It was found that the long-term CO variations were controlled both from Asian and global emission source changes, and also significantly by the year-to-year meteorological conditions (outflow efficiency from China). We also showed that the contribution from non-Asian emissions was also especially important in the springtime that was underestimated by the model simulation.

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We had carried out the sampling of PM_2.5 and PM₁ in Beijing, China from Jan. 9-23, 2013. The mass concentrations, inorganic ions, water soluble organic carbon and trace elements were measured. The highest mass concentration of PM_2.5 was 364 µg/m³ and mass concentrations of six samples were almost the same as those measured by the U.S. Embassy in Beijing. The ratios of PM₁ to PM_2.5 were more than 0.95. The total amount of water soluble components increased during Jan.11- 14 and Jan.18- 23 and their ratios to the PM_2.5 mass concentrations were greater than 0.6. The lowest ratio of nitrate to sulfate, 0.59, was observed during Jan.11- 14 when the highest concentration of PM_2.5 was measured. The concentrations of 57 trace elements were determined by an ICP/MS analysis. The As/V and Pb/Zn ratios were evaluated as indicators of anthropogenic emission sources such as coal combustion. We obtained 8.5 as As/V and 0.77 as Pb/Zn that were higher than those in previous reports. The increasing emissions from coal combustion for home heating should be one of the causes of the high PM_2.5 concentration.

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[in Japanese]

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Routine monitoring of hourly PM2.5 mass concentrations by local governments started in the 2011 fiscal year in Japan. The levels and temporal variation pattern of PM2.5 mass concentrations were summarized nationwide. Data from a total of 71 monitoring sites from 36 municipalities was investigated. The annual mean concentration ranged from 9.7-22.7 μg m^-3, and 39 sites exceeded 15 μg m^-3 (Japanese annual average air quality standard value). The daily concentrations, ranging from - 35.1-105.5 μg m^-3 tended to exceed 35 μg m^-3 (24-hour average air quality standard value) when Asian Dust and/or anthropogenic sulfate aerosols from East Asia were transported to Japan. However, high concentration events sometimes occurred on urban scale, implying the strong influence from domestic sources. Diurnal variation patterns of PM2.5 were multifarious compared to those of NO_x, which exhibited a clear bimodal pattern. A day-of-week variation increasing on weekdays and decreasing on weekends was detected, suggesting anthropogenic influence on the PM2.5 levels. The monthly maxima tended to appear in spring or autumn, while the minima generally appeared in September or in December.

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