From 1975, in cold regions where there is a tendency for snow to accumulate, it became clear that road particulates, which occured as a result of the use of studded tires, brought about a new environmental problem. In particular, the notable vorsening of pollution in urban areas in Hokkaido, Miyagi, Nagano, etc. called for a resolution to the urban pollution. Although it is a slightly old story, the difficulties and details encountered by Miyagi Prefecture up until the establishment of the Law on the Prevention of the Generation of Particulates from Studded Tires and outline the movement of the SPM Measures are introduced.

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Ozone concentration in the troposphere has more than doubled since the last century, and the surface ozone concentration superimposed with ozone-rich urban air plumes often reaches damaging levels for vegetation. Since the 1950s, when ozone was identified as the cause of damages to some crop species, many studies have been done about the effects of ozone on crop growth and yield. From 1980 through 1987, the National Crop Loss Assessment Network was conducted in the USA, and the relationship between ozone dose and crop yield response (D-R relationship) was calculated for major crop species from the results of ozone exposure in open-top field chambers. Assessments using the D-R relationship showed substantial loss of agricultural production in the USA and its economic consequences. In Europe too, D-R relationships were established for crop species such as spring wheat by the experiments with open-top chambers. In Japan, a research project was initiated in 1986 for assessing ozone impacts on production of crops with rice of major concern. D-R relationship was established for rice by the experiments with field chambers, and the ozone impact on rice production was estimated with a simple model of rice growth for the Kanto region of Japan. The results showed up to 10% yield loss due to ozone with a large variability by year and location, and the total amount of crop loss of up to 4.7% of the total production in the study area. Variation of the D-R relationships was studied using process-based models of soybean and rice. The results suggested soil water constraint and seasonal variability of ozone concentration as possible causes of the variation. Further analyses with an analytical model indicated that the variation is inherent to D-R relationship, and is generally caused by the fluctuation of the crop growth perse.

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Long term observation of O₃, SO₂, aerosol compositions and meteorological parameters was conducted at Mt. Unzen Nodake, Nagasaki prefecture. During this observation, the volcanic activity of Mt. Ase was at it's peak. The observation indicates that both Mt. Sakurajima and Mt. Ase had a strong impact on the observed concentration peak. High concentration episodes were selected when the SO₂ concentration exceeded 10μg m^-3, and the origin of the observed SO₂ plume was estimated based on the upper meteorological observation data and backward trajectory analysis. It was revealed that Mt. Sakurajima was responsible for 9 selected episodes when the Kyushu area was located at the backside of a traveling high pressure system and the SE-S wind system dominated the Kyushu area. Mt. Ase played an important role for the other 11 episodes and Ca2+ showed high concentration levels.
Conversion factors from SO₂ to SO₄^2- (Fs) ranged betwen 0.01-0.51 when the high SO₂ and SO₄^2- concentrations from the volcano plume were detected (Fs was below 0.35 for 18 out of 22 episodes).
An averaged SO₄^2-concentration level of 5.1μg m^-3 was evaluated when the SO₂ level was below 1 ppb and there was no effect from volcano emission. Trajectory analysis indicated that long-range transport from the Asian continent was responsible for these SO₄^2-levels.

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Ambient airborne asbestos concentration was increased in the wide disaster area after the Great Hanshin-Awaji Earthquake. In order to identify the asbestos emission source and its effect on airborne concentration, we surveyed asbestos emission from damaged buildings and calculated the effect of asbestos from buildings on ambient air.
First, we surveyed buildings which included sprayed-on asbestos with help by municipalities, and found that sprayed-on asbestos has been used mainly on steel structure buildings and used even after its use was prohibited. Next, we surveyed asbestos emission from three types of demolition sites: pre-removal of sprayed-on asbestos, demolition after pre-removal and demolition without pre-removal. A great deal of asbestos was emitted from demolition without pre-removal and it was shown to be the main source.
Furthermore, we estimated asbestos emission and its effect on ambient air using a plume-puff model. It has been shown that there was a weak linear correlation between estimated and observed levels of asbestos, and that such estimation can interpret the order of observed levels. Thus, we were able to provide a useful method for the estimation of ambient air level from asbestos emision sources. Finally, in order to avoid asbestos emission caused by demoliton without pre-removal, we point out the necessity for pre-removal of sprayed-on asbestos as well as better regulation.

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Volatile organic compounds in rainwater and in the atmosphere were determined in Yokohama, Japan by purge and trap or adsorption column methods and GC/MS. The average concentrations of dichloromethane, toluene, chloroform, and 1, 2-dichloromethane in rainwater were 9.8, 2.4, 2.1, and 1.5 nmol/L. The contribution of rainwater to VOCs pollution in surface water can be significant. The relative standard deviations of VOCs were very high (140-730%) in rainwater. In contrast with the ion concentration, the VOCs concentrations in rainwater were not dependent on the precipitation intensity and were not high at the beginning of the precipitation. The scavenging effect below cloud level was very small for VOCs. The concentrations of VOCs in rainwater were dependent on their concentrations in the atmosphere near the ground with some exceptions, such as benzene.

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Behavior of airborne acidic and oxidative components in autumn and early spring in the mountainous area of Japan was investigated during cooperative field observations of meteorology and chemistry in October 1991, November 1992, and March 1994. Measurements of gaseous and particulate compounds were made every 1 or 6 h at Happo at an altitude of 1, 850m in the central mountainous region, the air at which is considered to be representative of air quality in the lower free atmosphere in far-eastern Asia.
During the field observations in October 1991 and November 1992, concentrations of pollutants fluctuated significantly. The maximum concentrations of ozone, dust, and PAN in the highest concentration episode were 50 ppb, 50 μg/m³, and 1 ppb, respectively. At that time the concentrations of SO₄^2-, T-NO₃ (total nitrates), and NH₄⁺ also increased relative to average concentrations. In particular, the SO₄^2- concentration reached 20 μg/m3. Total equivalent concentration of anions (SO₄^2-, NO₃^-, and Cl^-) was much higher than that of cations (NH₄⁺, Na⁺, K⁺, Mg²⁺, and Ca²⁺), which suggests that a portion of the SO₄^2- existed in the form of acidic aerosols such as H₂SO₄ and NH₄HSO₄. In high concentration episodes of SO₄^2- and T-NO, the sulfate conversion ratio, i. e., SO₄^2--[S]/(SO₂-[S] +SO₄^2--[S]), was as highas 0.8. These findings suggest that air pollutants transported to the observation site resulted from intensive chemical reactions.
During the field observations in March 1994, ozone concentrations ranged between 40 and 55 ppb higher than those in autumn, reflecting the increase of background ozone in spring. Concentrations of SO₂, SO₄^2-, and T-NO, increased frequently to the levels of the highest autumn concentrations. At that time the concentrations of Ca²⁺ also increased. These findings suggest that air pollutants and Kosa aerosol (yellow sand) were transported from continental Asia.
Backward trajectory analysis suggests that SO₄^2- and T-NO₃ were present in quantity in the air mass that passed over urban and industrial areas and were neutralized with alkali components such as NH⁴⁺ and Ca²⁺. On the other hand, when air masses containing volcanic gas were transported concentrations of SO₂ and SO₄^2- increased and that of T-NO₃ was at a low level. Thus, the existing acidic aerosols had not been neutralized with alkali components.

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Although sea and land breezes have been calculated by many numerical models, most of these model use an orthogonal coordinate system with the constant grid space horizontally and z coordinate system following the terrain vertically. However, it is hard to show irregular shaped coastline in orthogonal coordinate systems. The grid lines don't strictly fit with the coastline, and calculation error may occur. In this study, we developed a three dimensional atmospheric boundary-layer model with a boundary-fitted curvilinear coordinate system (BFC), in which it is possible to fit grid line to the coastline and contour lines, and examined the validity of BFC from the calculated results of sea and land breezes over Osaka bay with FMG (orthogonal coordinate system of 80×80 meshes of fine mesh grid horizontally), CMG (orthogonal coordinate system of 20×20 meshes of coarse mesh grids horizontally), and BFC (boundary-fitted curvilinear coordinate of 20×20 meshes). Assuming that the calculated results with FMG were true, we could estimate the accuracy by whether the calculated results with CMG of BFC were in agrement with the calculated results with FMG.
First, sea and land breeze simulations using the atmospheric boundary-layer model including the turbulence closure model and the surface energy budget model were carried out on the condition that the surface altitude was assumed to be 0. The calculated results with both BFC and FMG agreed reasonably but the calculated results with CMG were somewhat different. It was found from these results that the model with BFC was more accurate than the model usin the orthogonal coordinate system. Second, we made calculations using real surface altitude. It was confirmed that the flow fields with the grid lines fitting both the coastline and the contour line around Mt. Rokko are better than those with grid lines fitted with only the coastline.
We believe that the atmospheric boundary layer model with BFC is useful to simulate the local circulation that is induced by the thermal contrast between land and sea.

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Atmospheric aerosols were collected on the roof of a building 59 meters high in the center of Tokyo metropolitan area every seven days from March 1995 to February 1996. Using X-ray fluorescence spectrometry (XRF) and ion chromatographic analysis (IC), we analyzed their composition. The quantitative analysis by XRF was given special attention in preparing the standards and matrix absorption corrections.
As a result of the analysis, about 40% of the aerosols were analyzed though the period. The components that increased in the warm season were NH₄⁺, Na⁺, Mg²⁺ and SO₄^2- and in the cold season NH₄⁺, NO₃^-, Cl^-, P, K and Zn incrased.
Using the factor analysis method, three factors were successfully isolated. Factor 1 was the strongest factor in urban atmosphere and was mainly composed of anthropogenic derived elements such as K and Zn. Cl^- was affiliated with Factor 1 only in the cold season when the concentration was high. Factor 2 was mainly composed of soil components such as Al and Si. Their seasonal variations were not clear except for their decreases during the rainy season, June to early July. Factor 3 was the weakest factor among the three factors and was mainly composed of the elements, Na⁺ and Mg²⁺. It is indicated that the south wind facilitates sea salt particles entering the atmosphere over Tokyo.

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