The Air Pollution Control Act was revised in April, 2006, and a new emission regulation for VOC was started for the purpose of photochemical oxidant reduction. The analysis showed that the reduction of VOC emissions in Kanto influenced the generation of photochemical oxidants in the ambient air. The VOC emissions have shown a tendency to decrease since 2000, and each material group (hydrocarbons, alcohols, etc.) has equally decreased without changing its composition ratio. However, the composition ratio of the individual components in every group significantly changed from 2000 to 2010. Using the data from the sites with photochemical oxidant concentrations over 120 ppb, the excess annual integrated concentrations were calculated and the influence that a change in the annual VOC emissions had on the generation of the highly concentrated photochemical oxidants was analyzed. Additionally, we normalized them by the temperature unit (℃) and solar radiation unit (MJ/m²) , and calculated the correlation coefficients between the decrease in the normalized value and reduction in the VOC emission since 2005 to 2010 by the prefecture. As a result, the data from Tokyo, Kanagawa and Saitama indicated high correlation coefficients, and it was deduced that the reduction in the VOC emissions reduced the high concentration of the photochemical oxidants in these prefectures.

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Recent anthropogenic NOx emission trends over East Asia between the years 2000 and 2012 were analyzed based on the GEOS Chem chemical transport model (CTM), tropospheric NO₂ vertical column density (VCD) from four environment monitoring satellites and the REAS Ver 2.1 emission inventory. The GEOS Chem model was applied to the Asian domain with a 0.5˚×0.667˚ resolution, and the NO₂ lifetime parameters were modified to have a better agreement with the observations. Analysis of the satellite NO₂ VCD observations over CEC (Central East China) showed that its concentration level has been increasing at 10%/year between 2000 – 2005. The GEOS Chem simulation by the REAS emission inventory well reproduced the satellite observation trends up to the year 2008. The relationship between the NO_x emission intensity and N budget components (such as NO, NO₂, N₂O₅, HNO₃ and nitrate) were examined, and our model study confirmed the high linear regression (NO₂_VCD = 0.08 + 0.012×NO_x_emission in 10¹⁵ moleculues/cm² unit; R² = 0.995 ) averaged over the CEC region. This relationship indicates that the satellite observed NO₂ VCD is a very good measure for the NOx emission intensity change.

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The diurnal variation of photochemical oxidants (O_x) over central Japan during clear summer days was investigated to clarify how it is intimately associated with the thermally-induced local circulation using hourly O_x, NO₂, NO_x concentrations and surface meteorological variables for the period of 1992-2009. In the Kanto plain, the peak time of the O_x concentration is gradually delayed from urban areas to inland and mountain areas. A similar situation is also evident in the Nobi plain, suggesting that air pollutants emitted in coastal areas are transported into the southeastern part of the Gifu prefecture by large-scale sea breezes. The high O_x concentrations in the inland area of the Kanto plain, which are observed before the occurrence of the large-scale sea breeze, tend to occur during successive clear summer days, and the high concentration area expands along the primary route of the large-scale sea breeze. These features might result from the nighttime accumulation of NO₂ produced by the decomposition of O_x that had already been transported into the inland areas on the preceding day. In the basins of the mountain areas, the O_x concentration increases until around noon, but it remains constant or slightly decreases after that time. The second peak of the O_x concentration appears at 17JST in the Kofu basin and at 19JST in the Iida basin. Since such a decrease in the afternoon is also evident for the diurnal variation in the potential ozone (PO) concentration, it is postulated that the consumption of O₃ by NO is not a major factor in the inhibition of the O_x concentration within the basin. Other factors, such as the transport of air pollutants due to the development of local circulations over the basin, should also be considered.

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We have developed a prototype gas chromatograph with an adsorption/combustion type micro gas sensor for the simple and on-site measurement of volatile organic compounds (VOCs) in indoor air. We have also confirmed the capability of the prototype to determine the concentration of toluene in working environments. However there was still a problem about its column separation under circumstances where some VOCs coexist. There were also some inpurity overlaps with the target compounds on the chromatogram during the analysis. Therefore the compositions of the columns were examined in order to improve the separation. The columns that have fever impurity peaks in the detection area of the VOCs were selected. Toluene and butyl acetate were used as the target compounds of the experimental model to evaluate their simultaneous analysis. The experiment was then conducted in a furniture factory. As a result of the examination that was conducted around a paint spraying booth, the determined concentration values of both compounds agreed with those calculated from a gas chromatography/mass spectrometry analysis as a conventional method for the sub-ppmv level. We succeeded in the on-site and simultaneous determination of toluene and butyl acetate. The objective of this study was to determine the basic specification of the portable gas chromatograph for more VOC applications.

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