Studies on three-dimensional observation and model analysis for urban and wide aerial air pollution in the present three decades are reviewed mainly focusing on author's studies.
Mechanisms of photochemical air pollution formation were clarified from a series of field study in Kanto area. That is, under the condition of weak atmospheric pressure gradient polluted air masses are transported inland due to sea breeze. In nighttime this moves to off shore due to land breeze. In day time vertical convection predominates and pollutants are mixed well. On the other hand in nighttime previous days pollutants remains aloft and this aged secondary pollutants are entrained to the mixing layer of the next day. The existence of large-scale circulation of air pollution between inland mountainous area and Pacific Ocean was also found.
From the studies in northern Kyushu area, it was found that the effects of stratospheric ozone intrusion, transported air pollution from the continent, locally emitted air pollution and pollutants from volcanic eruption are mixed.
From the aircraft observation and model studies in Kansai area for spring time increase in nitrogen dioxides, it was found that transported ozone to this area plays an important role to the oxidation process of nitric oxide which are mainly emitted in Osaka bay area.
From the air pollution trend analysis and model assessment wide spreading and homogenization of air pollution was observed; that is in recent year daily maximum concentration of oxidant are frequently observed in inland both in Kanto and Kansai areas.

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Forest decline is one of the serious environmental problems worldwide. Although the causes and/or mechanisms of these phenomena are different among the sites, acid rain, acid fog and/or soil acidification due to acid deposition are considered to be environmental stresses relating to these phenomena in North America and Europe. Therefore, there are many experimental studies on the effects of acid deposition on growth, physiological functions and nutrient status of tree species native to Europe and North America. Over the past 10 years, on the other hand, several research institutes and universities in Japan have been conducting experimental studies on the effects of simulated acid rain and soil acidification on Japanese forest tree species.
Exposure to simulated acid rain or fog with a p H of 4.0 or above for several months cannot induce any adverse effects on dry matter production and physiological functions of forest tree species. However, when the pH of simulated rain or fog is lowered below 4.0, negative effects appear on dry matter production and physiological functions in several sensitive forest tree species such as Japanese fir and Nikko fir. Based on limited information, it may be concluded that (1) Al dissolved into soil solution is the most important limiting factor for dry matter production, physiological functions and nutrient status of forest tree species grown in acidic soil, (2) the (Ca+Mg+K)/Al molar ratio in soil solution is a useful indicator to evaluate and predict the effects of soil acidification due to acid deposition on whole-plant dry matter production of forest tree species at the present time and in the future, and (3) Japanese coniferous tree species such as Japanese cedar and red pine are relatively sensitive to a reduction in (Ca+Mg+K)/Al molar ratio in soil solution compared with Norway spruce.
To evaluate critical load of acid deposition for protecting Japanese forest ecosystems, further experimental studies are needed on the effects of acid deposition on growth physiological functions and nutrient status of Japanese forest tree species.

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Photochemical oxidant (O_x) is one of the most remarkable pollutants in Japan. O_x concentration more than twice as high as the environment standard is often observed in the big cities. In this study, a two-layer box model which divided into the upper-and lower-layer on the basis of the upper surface of mixing layer, combining with Carbon Bond Mechanism IV was developed to investigate the relationship between O_x generation and emission intensity of primary pollutants, such as nitrogen oxide (NO_x) and hydrocarbon (HC). In the box, the composure to ventilation, surface deposition process and air pollution emissions are taken into consideration. The pollutant concentration of a typical summer day with active photochemical reactions for three areas (A: 44 km×44 km, B: 27 km×27 km, C: 26 km×33 km) set up in Hyogo and Osaka regions was calculated. The calculated concentration with emission sources reasonably agreed with spatial average of observed data. The simulation analysis suggested that ozone (O₃) concentration decreased with reduction of HC emission. For example, O₃ concentration decreased 40 ppb with 50% reduction of HC emission in C-BOX. Among HC, xylene was the most effective one for decrease in O₃ generation. However, with increase in reduction of NO_x emission, it was suggested that 0₃ concentration increased above the uncontrolled value before it decreased.

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It is very important for taking measures to estimate the emission amount of harmful chemical substances in Tokyo. However, the investigation period was very long and the investigation expenditure was very huge in the conventional method.
Therefore, we developed a new method to estimate the chemicals emission by using environmental data. It became clear that the amount of chemicals emission per year (x) and a balance betweem the environmental average concentration in Tokyo and the background level (y) were very highly correlative with each other in the regression line as follows,
log (y) =0.94 log (x)-2.49
A coefficient of correlation was 0.994.
It is possible to estimate the amount of the chemicals emission from the balance between the environmental data and the background data by using above mentioned equation. We estimated the amount of emitted CFC in Tokyo from this relationship. In addition, the total emission amount of hazardous air pollution substances as benzene, trichloroethylene and aldehide in Tokyo were estimated by this way.
Moreover, it became clear that the ventilation frequency of air in Tokyo was presumed to be about 0.7 time a day from these data.

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High concentration of suspended particulate matters (SPM) occurs frequently from late autumn to early winter in the urban areas of central Japan. In this paper photochemical formation of particulate organic matter in late autumn was investigated for inland mid-size and small-size cities far from large emission areas. Field observations were made in November to December 1989 at Okaya and November 1990 at Nagano. Organic matters in the form of airborne aerosols were collected on a quartz fiber filter using a high-volume air sampler in the daytime (1200-1700 JST) and at night (1700-1200 JST). After the filter was extracted with dichloromethane and subsequently with methanol, the extracted organic matters were analyzed by GC/FID equipped with a capillary column.
At first organic carbon (OC) and elementary carbon (EC) in the airborne aerosols were determined and then pinonaldehyde, C₁₇-C₃₃ n-alkanes, C₁₂-C₂₃ fatty acids, dicarboxylic acids, benzoic acid, lower molecular unresolved complex mixture (LUCM) and higher molecular unresolved complex mixture (HUCM) were detected. Then, concentrations of these organic matters in total attained to 1.4μg/m³ at Okaya and 3.4μg/m³ at Nagano, and they were about 20% of OC at both sites. Concentrations of pinonaldehyde, dicarboxylic acids, benzoic acid and LUCM increased in the daytime, and fractions of these matters formed by photochemical reactions in the daytime were estimated to be more than 50%. These results suggested that a significant amount of particulate organic matters is produced photochemically in the daytime even in the late autumn.

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[in Japanese]

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[in Japanese]

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