Prior to opening the Kansai International Airport (Sept. 1994), it had been assumed that the traffic pattern in the southern area of Osaka Prefecture including Izumiotsu City would change with the construction of a new access-highway to the airport. In order to evaluate the change in the two-dimensional distribution of NO₂ concentration in this city caused by the change in the traffic patterns over the last ten years, weekly average concentrations of NO₂ were measured each season of every year since 1987. The measurement was done by using diffusion samplers set at seventy two sites uniformly distributed in the city. Survey of the traffic volume on Osakarinkai Road and Route-26, which pass through the city in a north-south direction, suggested that construction of the access road caused a shift in traffic volume from inland to coastal areas. Investigation of the two-dimensional NO₂ distribution showed the following seasonal characteristics:(1) in summer, relatively low concentrations of NO₂ were usually observed at all sites;(2) in winter, although relatively low concentrations at all sites were also generally observed, high concentrations (>40 ppb) at all sites were detected occasionally. In both spring and autumn, in many instances, NO₂ concentrations were relatively higher than those in either the summer or winter.(3) In spring, the distribution of NO₂ concentration showed two peaks and the higher concentration range was over 40 ppb.(4) In autumn, high concentrations of over 30 ppb were usually observed at all sites. Concerning the change in two-dimensional patterns of NO₂ concentration in Izumiotsu City, a relatively higher concentration was observed along Rinkai-Road in the spring investigation before and after the changing traffic pattern. These results suggest that higher concentrations will appear along the trunk roads in coastal areas (where the discharge of nitrogen oxides has increased) in both winter and spring in cases when the development of a mixing layer has not been marked or the wind has fallen at peak traffic periods.

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In order to simulate atmospheric diffusion in a wind tunnel, a new oscillating wing method was developed. The objective diffusion pattern was in an area 30 km along the wind direction, and averaged in one hour. The new method employs shorter wings compared to the conventional oscillating method which employs wings as high as the wind tunnel ceiling. Since a row of short wings makes a strong swirl in the test section, a horizontal wind fluctuation of more than 20 degrees was achieved. When the angular motion of the row of wings was random, the distribution of mean wind velocity and turbulence intensity, and spectral structures were similar to the atmospheric boundary layer. A one hour averaged plume spread can be simulated in the wind tunnel with the proper selection of amplitude, random motion and roughness arrangement. However since the turblence scale was not similar to the atmosphere, plume meandering motion and concentration fluctuation which was generated by meandering could not be simulated in this study.

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Estimation of the long-term average concentration in a comparatively wide region into which substances are continuously discharged should be required in the environmental assessment of chemical substances. A model with which to estimate long-term average atmospheric concentrations of chemicals was developed. The model validation was conducted for trichloroethylene and tetrachloroethylene concentrations in atmosphere by comparing calculated values and observed values from a monitoring survey conducted over several weeks in summer and winter in the Kanto region. Good agreement with the measured values was obtained for the monthly average concentration of trichloroethylene, excluding two sites for the winter measurements where the monitored values were extremely high. For tetrachloroethylene, the calculated values greatly overstimated the monitored values at urban sites. More accurate emission date will improve model performance, because extremely high calculated values were mainly influenced by the methodology used to estimate the gridded source inventory. The model is capable of estimating the long-term (such as monthly) average distribution of concentration of chemicals in a wide flat area such as the Kanto plain.

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Risk assessments of diesel exhaust particles have been carried out by using animal experiment data. In the present study, the risk was estimated by using unit risk values from human epidemiological data. Unit risk value calculated by California EPA was applied to the diesel particle exposure level which was calculated from SPM values in every area of Japan. Following calculations of the averaged annual SPM value in each prefecture or big cities (SPMav), the regression coefficiency between SPM and elementary carbon concentration (R), the contributing rate of car exhaust particles to total atmospheric elementary carbon (C%), the contributing rate of diesel particles to total car exhaust particles (D%) and the averaged daily personal exposure rate in the environmental SPM level (P%) were obtained. All of these data regarding exposure were based on actual measurements and analytical data in literature. Unit risk×SPMav×R×C%×D%×P% was calculated by each area and summarized to estimate the risk for all Japan. To estimate annual risk, both of 70 and 75 years of age were used as a mean life span. When the unit risk and mean life span of 75 years was used, annual lung cancer death was estimated to be 5, 277 (1, 143-21, 109), which correspond to 11.5 (2.5-46.2)% of annual lung cancer death in Japan in 1995. The calculated risk value may be a future risk for the present exposure level when long latent periods in carcinogenesis are considered.

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In order to develop a concentrated collection technology for gaseous compounds, the collection of SO₂ using an artificial lung was studied. Alkaline absorption solution was streamed in an artificial lung instead of blood in this study and SO₂ was scrubbed in the absorption solution, when experimental gas containing SO₂ was streamed through the air line of the artificial lung.
Collection efficiency of SO₂ with the artificial lung was independent of SO₂ concentrations in the experimental gas, and was only dependent on the flow rate of the gas. The normalized collection amount for SO₂ was defined as tha product (α) of experimental gas flow rate and collection efficiency, which was the relative value of SO₂ collected in a unit of time. Calculating the value (α) according to the above definition when the gas flow rate was 7 L/min, the normalized collection amount was 4.4 times higher than a flow rate of 1.1 L/min. Furthermore, if the absorbtion solution is circulated, it is possible to concentrate the collection of SO₂ and other acidic gases through enhanced flow rate of the gas, even at low level environmental concentrations.

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In order to access the present atmospheric environment related to a planned 1.4 million KW coal power plant, the NO₂ concentration in the atmosphere was measured with a TEA capsule at fourteen sites in the eastern area of Kobe during a one year period from 1. Apr. 1997 to 31. Mar. 1998. The following results were determined.
Firstly the average annual NO₂ concentrations measured around the Osaka bay area were higher than those determined at sites around the foot of the Rokko mountains.
Secondly thirteen sites could be classified into four groups (Spring-type: 6, Summer: 1, Autumn: 1 and Winter: 5) from the maximum value of seasonal NO₂ concentration at the site. Variations in the monthly concentrations correlated well among sites of the same type.
Thirdly the frequency of sites where the daily NO₂ concentration exceeded more than 40 ppb totalled 20-29% of all sites was defined as 51 by year; the frequency of a total of 30-39% of all sites was defined as S2, the frequency of 40-49% of all sites was defined as S3 and the frequency of 50%-was S4, so that, S4 was 11 days and the total from 51 to S4 was 105 days. The total of S1-S4 in Mar. and Apr. was 33 days, and 70% was in the S2-S4 periods. Further, weather conditions in the S1-S4 groups in Apr. and Oct. were anticyclone during 80% of the period.

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