We developed an atmospheric emissions inventory of whole Japan; aimed to provide fundamental data for atmospheric transport modeling research. Target years of the inventory are 1995 and 1998, and target pollutants are NO_x, SO₂, CO, NMVOC, PM₁₀, NH₃ and CO₂. Emissions data are spatially divided to 10 km grid scale and timely divided to daytime and nighttime of each month. Total anthropogenic emissions of each pollutants in 1998 are 2.2 Tg NO_x, 1.0 Tg SO₂, 1.9 Tg NMVOC, 3.8 Tg CO, 0.18 Tg PM₁₀, 0.5 Tg NH₃, 1.1 Pg CO₂. Furthermore, biogenic NMVOC emissions were estimated as 1.8 Tg. The spatial distributionof each pollutant commonly shows high emissions in the urban areas; characteristic distributions from agricultural sources in case of NH₃ and from forest sources in case of NMVOC are also shown. Furthermore, NH₃ and NMVOC emissions have a significant peak in summer season.

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Nitrogen isotope ratios (δ¹⁵N) in gaseous ammonia (NH₃) and ammonium ion (NH₄⁺) in aerosols as well as atmospheric concentrations of these species were measured. Samples were collected at Maki National Acid Deposition Monitoring Station that locates west of the Niigata Plane and near the shoreline of the Sea of Japan in Niigata Prefecture. The atmospheric concentrations of NH₃ and NH₄⁺ ranged, from 47.4 to 164 with a mean of 96.9 nmol m^-3 and from 4.6 to 61.6 with a mean of 21.3 nmol m^-3, respectively. The atmospheric concentration of NH₃ at Maki Station is almost average value in Japan, while NH₄⁺ concentration is lower than NH₃. The δ¹⁵N in NH₃ and in NH₄⁺ ranged, from-14.5 to -1.0 with a mean-/8.3% and from 12.2 to 39.6 with a mean 22.1%, respectively. Thus, there was a large difference in δ¹⁵N in NH₃ and in NH₄⁺. Considering the changes of δ¹⁵N in NH₄⁺ in the experiment on dry deposition of NH₃ to a H₂SO4-impregnated filter by Heaton (1997), there may be sufficient equilibrium reactions between NH₃ and NH₄⁺ aerosol in the atmosphere when atmospheric concentration of NH₃ exceeds that of NH₄⁺, and the isotopic composition of NH₄⁺ became enriched in ¹⁵N, giving rise to the value of δ¹⁵N by the equilibrium isotopic fractionation effect between gas and aerosol.

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The motor vehicle emissions should be estimated precisely and in detail. This paper improved the estimation of the Environmental Agency reported in 1996 and developed the estimation system of motor vehicle emissions. This estimation used the traffic volume rates of 24 hours against daytime which depends on vehicle types. Traffic volumes were calculated in each travel speed bands, while reflecting road types and roadside condition types. Emisson factors for heavy duty vehicles, light duty vehicles, special purpose vehicles and buses were reconsidered with the average vehicle kilometers and the equal inertia weights which were calculated for each gross vehicle weight category, while reflecting load efficiency and vehicle use categories (business or private). Annual emissions of NO_x of Japan in fiscal year 1997 was 661kt and that of SPM was 66.4 kt. Calculated by this method, the annual CO₂ emission was 192Mt. It was equivalent to 81% of the CO₂ emission of 243 Mt calculated by fuel consumption statistics and emission factors. According to the estimation of 1994 by the Environmental Agency, the traffic-volume-base CO₂ emisson was equivalent to 70% of the fuel-consumption-base estimation. Though the estimated years of these estimations are different, it can be said that approximately 9 point improvement was accomplished by this estimation system.
Estimation of freight vehicles was improved especially by reflecting the actual vehicle kilometers of super heavy vehicles for business use. On the other hand, it was shown that passenger cars require improvement on emission factors so as to reflect actual usage conditions.

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The motor vehicle emission system was extended to show the spatial distribution of motor vehicle emissions for the whole Japan. By this system, emissions can be estimated in the road sections and in the third mesh (the grid of about 1km×1km) which was defined in the national mesh code. As a case study of spatial analysis using the emission data, population who exposed to the additional SPM from motor vehicles in the road sections was calculated. This spatial distribution system is distinguished by the following points; it covers the whole Japan, it has a high resolution of 1km×1km grid, and it is based on actual traffic data of the road traffic census. Emissions in each road sections of the road traffic census were calculated by both 24 hours traffic volumes reflecting detailed vehicle types and emission factors reflecting travel speed of each road sections. Spatial database was developed for the grid estimation by following procedures; linking section code to each road section item, cutting these items by grid, and attaching the third mesh code to each fraction. The emission distribution map made it easy to understand which area had larger emission than others. The third mesh unit emission data is suitable for analysis with other published mesh data and input data of various models. This system would be applied to a regional assessment tool of environmental policies. It is possible to calculate emissions per hour, if the origin destination data of the road traffic census were available.

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