Characteristics of the trans-boundary pollutant transport (outflow) during the springtime W-PASS 2008 field campaign at Cape Hedo, Okinawa, were analyzed based on the regional meteorological model WRF and chemical transport model CMAQ. We found 8 large-scale intermittent transboundary outflows occurred during the observation period, and the numerical model results successfully reproduced the time and vertical variations in the major pollutants. We also showed that the typical height of the outflow of pollutants occurred below 2 km, and these features are well simulated and showed a good agreement with the NIES lidar observations at Cape Hedo. Meteorological patterns during the pollutant outflow were classified into two patterns, i.e., the 6 cases of typical behind cold front outflow (BCF) and 2 cases of transport in the northern side of the travelling high pressure system (HPN). The model simulation showed that the outflow of BCF includes the fresh air mass, while the outflow of HPN are well aged compared to the BCF cases. Sensitivity analysis with the zero-out Chinese pollutant emission was used to evaluate the correlation of SO₄ ^2-- O₃ - CO that originated from China, and confirmed that the contribution of Chinese emissions plays a dominate role when the high concentration of pollutants are observed at Cape Hedo. A comparison of NMVOC suggests the need to update the NMVOC emission inventory in order to have a good agreement with the observed level.

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Evaluation of the accurate source-receptor relationships is important to understand the air quality over East Asia under the rapid changes in anthropogenic emissions resulting from economic shifts. When examining the sensitivity of variations of the model's input parameters to chemical concentrations, the brute force method (BFM) was the most commonly used, where input parameters are varied one-at-a-time. In this study, we applied the Higher-order Decoupled Direct Method (HDDM) to the case study of a trans-boundary air pollution episode occurred in springtime on 2007. HDDM provides an efficient and accurate approach for proving sensitivities, and could be applied to photochemical ozone (O₃) involving complex nonlinear chemical formation processes. Based on the results of HDDM, we analyzed the ozone control regimes, and found that NO_X sensitive region was dominate during the episode. The rapid increasing of NO_X emissions in East Asia would be a possible reason for increment of O₃ concentration during this episode in Japan. Applications of HDDM are to provide location- and time-dependent ozone isopleths via a parametric scaling method, and to assess the source contributions via a zero-out contribution (ZOC). During the episode, the contribution from anthropogenic emissions of China was approximately 30 %, and central eastern China (CEC) accounts for more than 50 % contribution. The usefulness of HDDM for the air quality studies over East Asia was demonstrated by this study.

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Forest decline has been found in the Tanzawa Mountains and O₃ is thought to be one of its causes. However, a three-dimensional analysis using numerical models has not been carried out in the Tanzawa Mountains. In this study, we carried out a study to understand the behavior of the O₃ concentration in the Tanzawa Mountains using numerical models (the meteorological and air quality models). The surface O₃ concentration in the mountains and its surrounding area did not depend on the model grid size of 15km and 5km. The diurnal variation in the surface O₃ concentration in the Tanzawa Mountains is low, because the O₃ chemical production is lower and the dry deposition is not lower than that around the air quality monitoring station in the daytime, and the sea breeze with fresh air does not reach the Tanzawa Mountains in the evening. The vertical O₃ concentration increases with the elevation or is constant with the elevation in the ABL (Atmospheric Boundary Layer). The O₃ concentration above the ABL immediately decreases with the elevation and reaches a background concentration (50ppb). The numerical models are effective tools for the simulation of the O₃ concentration in the Tanzawa Mountains, because numerical models can possibility complement the lack of O₃ monitoring in the Tanzawa Mountains.

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The loss of volatile organic compounds (VOCs) occurs during the refueling of passenger cars. This study was undertaken to estimate the hydrocarbon emissions caused by these refueling losses by vapor loss measurements using a sealed housing for the evaporative determination. The refueling loss in Tokyo in FY2009 was estimated to be approximately 10,000 tons, which represents a slight increase in comparison to that in FY2005. The ratio of refueling loss to the total VOC emission also increased. The cost of damage due to refueling loss was estimated to be approximately 1,900 million yen in Tokyo and approximately 16,200 million yen in Japan overall. Evaporative components that were not included in the standard gases used for the VOC were measured. Because these components contain a large amount of alkenes which tend to have higher MIR values, the contribution ratio of the refueling-loss in photochemical ozone generation were estimated to be higher by considering such trace components.

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