As a research work in Japan Clean Air Program (JCAP), a micro-scale air quality simulation model, aiming to analyze the effect of automotive emission on roadside air quality, was developed. The model consists of (1) simulation of micro-scale traffic on target roads, (2) estimation of emission gas distribution along the roads, and (3) simulation of air flow and advection/diffusion of emission gas around the roads.
Validity of the simulation model was verified by comparison with (1) flow around simple shapes in a wind tunnel experiment, (2) flow in a miniature urban model in the wind tunnel, (3) tracer gas concentration in a diffusion field experiment in a real urban area, and (4) measurement values at continuous air monitoring stations. In every comparison, the model showed good agreement. In the prediction of daily average concentration at the monitoring stations, calculation yields were 20-30% different from the measurements, which showed applicability of the model to prediction of real urban roadside air quality.

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A case study to investigate the effect of traffic volume reduction and idle stop on NO_x emission and concentration distribution along main roads was conducted using the Roadside Air Quality Simulation Model reported in the first paper.
Vehicle speed profile and NO_x emission distribution, averaged over all vehicles passing through the road links, were calculated by the traffic simulation model and the transient emission estimation model. In the Base Case, average speed shows a “V” shape whose bottom is locates at the stop line of the crossroads, and the emission rate increased toward the stop line along the road at the upstream side of the crossroads. NO_x concentration, show high values at spots where stationary vortexes occur behind buildings or near corner of the crossroads. In the case of Traffic Volume Reduction, NO_x emission was reduced at most locations of the road links due to reduction of vehicle number and resulting increase of travel speed. In the case of Idle Stop, NO_x emission decreased largely at the upstream side of the crossroads where vehicles stop due to traffic signal. Also, quantitative estimation of concentration profile against wind direction and 1-day averaged concentration at a vehicular emission monitoring station was conducted.
Through this case study, applicability of the Roadside Air Quality Simulation Model on the quantitative study of air quality was verified.

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From June 1996 to August 2002, some ion concentrations in one-storm precipitation were measured at USP (the University of SHIGA Prefecture) which is adjacent to Lake BIWA. Using these concentrations the effect of the lake on ion concentrations in precipitation was estimated.
In conventional methods, effects of sea-salt have been estimated by using Na⁺ concentration and ratios of pollutant concentration to Na⁺ concentration. However, in the adjacent area to Lake BIWA it has been observed that the ratio of Cl-to Na⁺ in precipitation is lower than the sea-salt. So, it is suggested that chlorine-losses may have been observed and that Na⁺ is not only from sea-salt but also from lake-salt. Then the author attempted to estimate the sea-salt effect and lake-salt effect on ion concentrations by using Mg²⁺ and Na⁺ in precipitation. In this situation it was assumed that Mg²⁺ and Na⁺ are only from sea-salt or lake-salt and not from soils or human activities.
It was shown that miscellaneous SO₄^2- (other than from sea-salt or lake-salt) was 10 to 20% less than conventional non-sea-salt (nss) SO₄^2-.

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Emission of volatile organic compounds (VOC) of and its spatial distribution have been estimated for painting and printing, which are major sources among the stationary sources of VOC by evaporation in Japan. Quantities of paint production, solvent in paint, thinner for dilution and washing, and chemical composition of the solvents were estimated by category of application and by type of paint. VOC emissions by chemical species were calculated based on these values and efficiencies of emission reduction, which were set by category of application. Similarly, emissions from printing were determined based on quantities of ink production, solvent in ink, thinner for dilution and machine, chemical composition of the solvents, and emission reduction efficiencies. Spatial distributions of VOC emission have been estimated in 1km×1km grid resolution by allocation of the national total step by step to increase accuracy, namely, from the nation to prefectures, then from the prefecture to cities, and finally from the city to the grids. The total VOC emission from painting was estimated as 8.3×10² Gg/y. Among application categories, building application was the largest source of emitting 2.0×10² Gg/y of VOC. As for printing, the total emission was calculated as 1.8×10² Gg/y, percentages of toluene, alcohols and ketones were 24.4%, 17.2% and 15.6%, respectively. Significant regional differences in chemical composition of VOC emission were found by the spatial distribution study. In the case of VOC emission from painting, high emission areas were observed in industrial districts around big cities. As for printing, since the print business is an urban industry, most emissions were concentrated around the downtown area.

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We investigated a influences of volcanic emissions on fogwater at the top of Mt. Akagi located in Gunma Prefecture. After September 2000 when volcanic emissions from Miyake-jima increased rapidly, SO₄^2- concentration in the fogwater became higher, and pH and the value of NO₃^-/non-sea-salt SO₄^2- (N/S) became lower than those before. Very low NO₃^-/non-sea-salt Cl-ratio (<1) was observed seven times. These cases have not occurred since 1993 when fogwater monitoring was started. It was considered that the fogwater was greatly affected by sulfur dioxide and hydrogen chloride discharged from Miyake-jima volcano. Especially on September 14, 2000, specific fogwater (pH 2.99) mostly consisting of sulfuric acid and hydrochloric acid was observed, and the N/S was extremely low (0.07). When the specific fogwater mentioned was observed at the mountain, it was considered that a large amount of sulfur dioxide was transported to Gunma Prefecture. This transportation was recognized by other research such as sulfur dioxide monitoring at the earth's surface and real-time simulation on long-range atomospheric dispersions of volcanic gases. These results suggest that such fogwater with high SO₄^2- concentration and low pH and N/S was caused by the volcanic gas from Miyake-jima.

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[in Japanese]

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[in Japanese]

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