With the research work conducted in order to clarify the effect of acid fog to vegetation and tree, acid fog affected directly to vegetation and tree. In the early 1980's, an extensive survey on acid fog had been carried out in the west coast of California in the U. S. Low pH fog (pH 2. 2) was observed. In the course of these researches, string type active fogwater collectors became to be a major sampling method. The simulation of acidification of fog droplet in the atmosphere was extensively conducted. Just after fog development, the intake of aerosol and the oxidation by hygrogen peroxide contribute to the acidification, and in the later stage oxidation by molecular oxygen through catalytic action of iron and manganese contributed significantly. Later, the surveys of acid fog have been carried out at the mountainous areas of northeastern and eastern parts of U. S., and acid fog were also observed. In that area, it is focused that to estimate the deposition amount of ionic species by fog. In Japan, already in the 1960's, field survees on acid fog were conducted, in 1984 acid fog survey started on Mt. Akagi under a viewpoint of ecological impact. Low pH fog (pH 3 to 4) continued more than 10hr. It was pointed out that there are forest damage by acid fog in several locations, especially the tree mortality mechanism by acid fog in Tomakomai was clarified.

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Chlorofluorocarbons have been used extensively as refrigerants, detergents and foaming agents for their excellent physical and chemical prope rties. However, because of their stability, they are rapidly being accumulated in the gloval environment; causing the destruction of the stratospheric ozone layer. For this reason, the emission of specified CFCs to the environment has becom e regulated by the Montreal Protocol. But there is no agreed method for decomposing CFCs. Thus, the establishment of the decomposition method of CFCs has become a worldwide urgent problem.
Benzene was used as a decomposing agent in this study. It was combusted at the reaction temperature of 900°C. A catalyst was heated by the heat of combustion of it and decomposed CFC 113. The electric power was turned off when the decomposition of CFC 113 started. The reaction temperature, however, increased to 1100°C, and was maintained. The decomposition of CFC 113 was continued at that time. It was found that the highest decomposition efficiency was 80% at the more ratio of benzene/ CFC 113 of 20/ 1 in this experiment.

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In order to observe lung tumorigenesis induced by airborne particles (AP) and tumorigenic enhancement by nitrogen dioxide (NO₂) and sulfur dioxide (SO₂), lungs in SPF Fischer 344 rats of 7 weeks old, into which the mixture cf extracts from AP (17 mg in total) collected at the three places in Tokyo and carbon washed by dichloromethane were intratracheally instilled 4 times (once a week), and which were exposed to 6 ppm NO₂ and 4 ppm SO₂ for 16 hours a day for 11 months, were morphopatholcgically examined after 18 months.
In the group, for which instillation of AP extracts and exposure to NO₂ and SO₂ were applied, lung tumors were seen in ₂ of 10 rats. The both tumors were benign adenoma. There was no lung tumor in any other groups.
In the group, into which AP extracts was instilled, marked hyperplasia of alveolar type II cell was seen. In the group, into which carbon was instilled, slight hyperplasia of alveolar type II cell and ectopical proliferation of bronchiolar epithelial cell were seen.
In the group, which was exposed to SO₂, slight squamatization of epithelium and loss of cilia in bronchus were seen.
In the group, which was exposed to NO₂, slight squamatization of epithelium in bronchus and bronchiolus and slight hypertrophy of alveolar epithelium in alveolar ducts were seen.
These results suggested that the extracts from AP (17 mg) did not induce lung tumor in rats, but the tumori genesis by AP extracts was enhanced by the exposure to NO₂ and SO₂.

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Inflammation, increase in vascular permeability and mucous hypersecretion are the important pathological findings in chronic obstructive lung diseases such as asthma and chronic bronchitis. In the present experiment, vascular perm eability and bronchial inflammation were found to be mediated by superoxide (O₂^-) produced by diesel exhaust particles (DEP), because the pretreatment of mice with intratracheal injection of PEG-SOD (polyethylene glycol conjugated SOD) caused a decrease of endothelial damage, lung edema and mortality by pulmonary edema, and inflammation of the bronchial wall was also reduced by the pretreatment with PEG-SOD. The mucous hypersecretion was demonstrated as an increased content of bound-form sialic acid in bronchoalveolar lavage fluids and a proliferation of goblet cells on the bronchioles, which contain a large amount of mucous in the cytoplasm, and were stained in magenta by PAS-staining. Furthermore, infiltrations of eosinophils, neutrophils, lymphocytes and mast cells were observed under the submucosal layer by repeated instillations of DEP.
These findings suggest that O₂^- may play an important role in inducing of increase in vascular permeability, bronchiolar inflammation and mucous hypersecretion, and that DEP may be involved in the pathogenesis of lung diseases, including asthma and chronic bronchitis.

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Cold air gravity currents flowing down over plateau-slope-plain topography have been analyzed numerically using non-hydrostatic flow model with boundary-fitted curvilinear coordinate system. Effects of the slope angle and the plateau height on dynamical nature of the gravity current have been discussed in terms of an advancing speed of the gravity current head (V_h) and energy balance of the head. Results are as follows:
First, temporal change of V_h, and final V_h values over the plain showed only minor var iations for change of the slope angle (φ=10°, 20°, 30°, 45°, 60°, 90° with H_p=500m). However, total kinetic energy of the gravity current head (K_t), which should have close relations with V_h, and can be estimated more precisely than V_h, responded clearly to the change of the slope angle, showing that when Φ=30°-60°, the initial potential energy of the cold air layer over the plateau can be most effectively transformed into the kinetic energy of the gravity current head over the plain. This can be explained by the examination of rate terms in the energy balance equationsuch as those of pressure-gradient force and buoyancy force.
Secondly, effects of the change of plateau height (H_p=500, 1000 m with Φ=45°) on both final V_h and K_t values over the plain can almost be evaluated by the difference of initial potential energy of the cold air layer over the plateaus; the final V_h value can be predicted by a semi-empirical formula V_h=k√g'H with k=0.84, where H stands for hypothetical depth of the cold air layer, consisting of plateau height and depth of the real cold air layer, and g' stands for the modified gravitational acceleration, which equals to (Δθ/θ) g with θ, the potential temperature of ambient air, and 40, the difference between those of the ambient air and the cold air.

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In order to characterize the high NO₂ concentration appeared along trunk roads in the Hanshin area, the data obtained at the monitoring stations in 1987 and 1988 were analyzed.
High NO₂ concentration appeared frequently in spring near the trunk roads, while high NO pollution appeared in winter. The NO₂ concentration was highly correlative with the O_x concentration measured at neighbouring ambient air monitoring stations, and NO₂/ NO_x ratio and the frequency of high NO₂ concentration appearance increased with rising O_x concentration.
This suggests that an oxidation reaction of NO + O₃→NO₂ + O₂ plays an significant role for the high NO₂ pollution in spring along the trunk roads in the Hanshin area.

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[in Japanese]

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