Mechanisms of dry deposition and its acidification under the natural environment were evaluated by the observing thin films exposed for a short duration to the atmosphere and by the measuring deposition amounts on four types of petri dishes. Petri dishes were dry, and contained water, aq. acid and alkaline solutions, respectively.
The former exposure tests using copper-coated glass plates and reagent-thin films were performed in the forest, where decay of the fir trees was observed. After exposures, thin films were analyzed to count qualiatively the corrosion caused by the deposition, chemical formulate and acidity of dry deposition components, using a photometer and a transmission electron microscope. The concentrations of gases and ionic components of aerosols at the mountain summit were found to be less than those at the foot of the mountain. However, observation of thin films clarified that the acidic nitric components were found to be mainly deposited at the high altitude of the forest. In contrast, the acidification by the nitric components was hardly observed on the foot of the forest. The acidic HNO₃ and NO₃^- may be deposited at high elevation of the forest, however their acidity was substantially lower at the summit than that on the foot because of NH₃ present there.
The latter exposure tests using petri dishes were performed at the plain site. The measurements of the deposition amounts of dry components onto petri dishes and the concentrations of gaseous and particulate matters in the atmosphere revealed the following points.
Gaseous HNO₃, SO₂ and NH3 were depostied much more than particulate NO₃^-, SO₄^2- and NH₄⁺ onto the wet-surfaces. In particular, SO2 was deposited on the wet-surface to acidify the surface. The deposition mechanisms of Mg²⁺, Na⁺, Ca²⁺ components of coarse particles were suggested to be almost the same even if the surfaces have different properties.
In the natural environment, once the material surfaces were washed out by rain, remaining wet, SO₂ was dissolved on the wetted-surface and made it acidic. Alkaline components such as carbonates were also deposited onto the wetted-surface, gradually dissolved in water to neutralize the acidity. Such processes are considered to be repeated, according to the weather change.

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In the present study, an industrial-scale pulse corona process to remove SO₂ and NO_x simultaneously from flue gas has been studied. The pilot plant built in the present study treated 2, 000 Nm³/hr of flue gas from a boiler. The geometry of the pulse corona reactor is similar to that of an electrostatic precipitator commonly used in industry. A thyratron switch and magnetic pulse compressors, which can generate up to 130 kV of peak pulse voltage and up to 30 kW of average pulse power, have been used to produce the pulsed corona. The removal efficiencies of SO₂ and NO_x with the present process are maximum of 95% and 85%, respectively. Electrical power consumption to produce the pulsed corona, which has been one of the major difficulties to apply this process to industry, has been evaluated in the present study. The results showed that the power consumption can be reduced significantly by simultaneous addition of hydrocarbon injection and heterogeneous phase reactions to the process.

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Dry weight growth of Japanese cedar (Cryptomeria japonica D. Don) seedlings grown in artificially acidified brown forest soils was investigated in relation to pH, concentration of water-soluble Al or (Ca+Mg+K)/Al molar ratio in the soils.
Brown forest soils originated from volcanic ash, granite or sandstone and slate were used as soil materials The H+ of 10, 30, 60 and 100 meq was added as H₂SO₄ solution to IL of soils, but not to the control soils. Two-year-old seedlings were transplanted in the control and acidified soils, and were grown in a greenhouse for 12 weeks from 13 June to 5 September, 1994.
The dry weight growth of the seedlings grown in the brown forest soils was reduced with decreasing in the soil pH (H₂O). However, the growth reduction was considered to be caused by an increace in the concentration of water-soluble Al in the soils. The growth of the seedlings grown in the soil from volcanic ash was reduced when the concentration of water-soluble Al in the soil increased above 10.5μg/g on the basis of air-dried soil, and that of the seedlings grown in the other soils was reduced when the Al concentration increased above 30μg/g. The growth of the seedlings grown in the soils from volcanic ash and granite was reduced when the (Ca + Mg +K)/Al molar ratio in the soils decreased below 5, but that of the seedlings grown in the soil from sandstone and slate was reduced when the molar ratio in the soil was 9.21 or blow, and the concentration of water-soluble Al in the soil of this plot was 37.8μg/g.
The results obtained in this study show that the dry weight growth of Japanese cedar seedlings grown in the brown forest soils acidified by adding H₂SO₄ solution is reduced regardless of the concentration of watersoluble base cation in the soils when the concentration of water-soluble Al in the soils is above 30μg/g, and that is reduced when the (Ca + Mg + K)/Al molar ratio is below 5 even though the Al concentration is below 30μg/g.

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Temperature distribution around a building standing alone and cyclically standing is calculated with Large-Eddy simulation. The dfference of temperature distribution due to positions of the anthropogenic heat sources is investigated. The intensity of the heat is obtained from GIS data and energy consumption data near Shinjuku, Tokyo. Dependency of the temperature field on the width of the roads is also investigated. When a building stands alone, temperature fields does not so much depend on the positions of the heat sources. However when the buildings form the urban canopy, temperature field depends on the position of heat sources. In case for the heat sources are located at high floors of the building, heat is easily transported above the canopy, and slightly stable layer is generated in the canopy. In case for the heat sources are located low floors, the temperature in whole canopy rises up. When the road width is wider than the width of the buildings, the twin vortices are generated at the rear side of the buildings and air flows in from the side road to the back of the buildings, then go up to above the canopy. As a ersult, heat is easily transported to outside of the canopy. When the road width is narrower than the width of the buildings, the twin vortices are not geneated. The air goes down along the front wall of the buildings and moves to upstream through the side of buildings at upstream side, then goes up again along the side wall of the buildings. The exchange of heat is much reduced.

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A long-range transport model including a detailed chemical reactions was applied to characterize the transboundary pollutant transport during the Baiu season, and model results were compared with the aerosol high concentration observed in Tsushima, Chikugo-Ogori and Seoul in June 1991. Long-range transport model results and backward trajectory analysis indicate that the Baiu rainfront located between the southern part of China and the south of Japan island plays an important role for trapping the air pollutant emitted from China and Korean peninsula and for its transport/transformation to the northern Kyushu area. It was revealed that the north-south movement of Baiu rainfront is significantly important for the aerosol high concentration over the Kyushu and western part of Japan area.

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The properties of initial (until 2 mm) and succeeding rainfall at Ikoma-shi in Nara prefecture, where located in the middle of Osaka-shi and Nara-shi, were investigated over 1993 to 1995. The appearance percentages of initial and succeeding rainfall below pH 5.6 were approximately 93% and 75%, respectively. The contents of Cu²⁺ (μg/L) in the rain water increased as pH becomes lower. Although the relationship between pH and the electric conductivity showed some scatter, the electric conductivity increased exponentially as pH becomes lower. As a results of the determination of main ion species containing in the rain water of 1995, the contents (mol/L) in the initial rainfall were 2 to 3 times compared with these in the succeeding rainfall for Na⁺, K⁺, NH₄⁺, C1^-, NO₃^- and also were 4.5 to 5.0 times for Mg²⁺, Ca²⁺, SO₄^2-. The linear relationship was recognized between pAi (=-log ((NO₃^-) + (SO₄^2-))) which shows the hydrogen ion concentration corresponding to the molar concentration of NO₃^- and SO₄^2- and the logarithm of the electric conductivity (logλ), but was not recognized between pA_i and pH. The occurrence source of Na⁺ and Clin the rain water suggested to be due to the sea salt.

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In order to clarify the involvement of air pollution in each of the risks of atopy, atopic asthma and non-atopic asthma, the data on the prevalence of child asthma and atopy, which had been reported in the last forty years in Japan, were reexamined, indicating the following results.
1. Air pollution showed the involvements in decreasing the risk of atopy and increasing the risks of atopic and non-atopic asthma.
2. The main factor that increases the prevalence of asthma today was not associated with air pollution. This factor showed the involvement in increasing the risks of atopy and atopic asthma.
3. Air pollution was little attributable to the recent increase of child asthma and the population attributable risk percent (PARP) was about 4%.

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