The purpose of this work is to determine the amounts of water-soluble silicate (Si) and TOC eluted from the gel of water glass-type soil stabilizer. The amounts of silicate eluted from the sand gel are 35 and 27% by immersion method (Table 1) and by flow method (Table 2), respectively. All the organic carbon in the soil stabilizer is eluted with water immedia tely.

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Catalytic decomposition of dichlorodifluoromethane was carried out on various catalysts. Metal oxide catalysts such as CeO₂ and Nb₂O₅ exhibited high activity; however, they were deactivated rapidly due to an attack by inorganic fluorines produced during the reaction. Although sulfuric acid impregnated on supports was also active, the vaporization of sulfur in the form of sulfur oxides lead to the deactivation of this catalyst. The BPO₄ was active and retained its activity for prolonged reaction time. It was assumed that phosphate-based catalysts were the only possible system which can be applied to the decomposition of chlorofluorocarbons.

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In order to explore the possibility of catalytic reduction of CO₂ by lower alkane leading to the formation of more valuable products from lower alkane, the following reaction was examined by using a pulse reaction technique:
CO₂ + C₃H₈ → CO + C₃H₆ + H₂0.
As a result of catalyst screening, Cr₂O₃, ZnO, and Ga₂O₃ were selected as candidates of catalyst. On Cr₂O₃ and ZnO, the decomposition of C₃H₈ was significant and the formation of C3H6 from C₃H₅ was retarded by CO₂. On Ga₂O₃, CO and C₃H₆ were produced without the formation of by-products, demonstrating the possibility of catalytic reduction of CO₂ through the above-mentioned reaction.

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Catalytic decomposition of NO to N₂ and O₂ was performed over Pt/Al₂0₃ which was modified by various additives. The addition of Tb oxide enhanced the activity by a factor of 4, while K, P and Au decreased the activity. XRD and TEM observations revealed that Pt particles on Pt/Al₂0₃ and Tb-added Pt/Al₂O₃ grew into large crystallites in a similar way during the reaction. Oxygen spillover from Pt to Tb oxide probably accelerated the desorption of oxygen from the catalyst.

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Treatment of tetramethyltin (TMT) in N₂ gas with various solid adsorbents was studied. On solid acids such as silica-alumina, activated clay and acid clay, TMT was effectively decomposed, while silica gel or diatomaceous earth exerted only poor activity for TMT removal. Methane was obtained as a single gaseous product. Furthermore, the effects of salts of various transition metals supported on diatomaceous earth on TMT treatment ability were examined. Among the chlorides of Mn(II), Fe(III), Co(II), Ni(II), Cu(II) and Zn (II), only CuCl₂ exhibited a particular activity. On diatomaceous earth impregnated wit h CuCl₂, TMT was degraded to methyl chloride.

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The effects of low level air pollution on Japanese Cedar (Cryptomeria japonica) have been studied in the surrounding area of two thermoelectric power stations newly constructed in a rural area, Fukui Prefecture, on the Japan Sea side of central Honshu, Japan. The degree of visual injury in Japanese Cedar, scored with six different categories, was examined in 1974and 1977 respectively, covering the entire study area. A more complete monitoring has been conducted at eight permanent sites in Awara-cho since 1974. A dendrochronological study was also carried out to evaluate the effects of air pollution on the increment growth of Japanese Cedars. There were clear correlations between the distance from the power station and tree decline (Figs.3 and 15). Severe damage was observed, in general, within a 7 km radius from the power station. The localized injury of Japanese Cedar, along the flood plain of the two rivers, was also demonstrated (Fig.4). A rapid increase of injury was noted until through the late 1970's (Fig.5). The growth inhibition, during this period, was also revealed by tree ring analysis (Fig.14). Some recovery of tree vigor and increment growth was observed after the introduction of pollution control systems at the power station (Figs.5 and 14). Consistent relationships were demonstrated between the index of increment growth, i. e., standardized ring index, and the levels of SO₂ and NO₂ (Fig.17). Scarcely any correlation was observed between pH of rain water and the standardized ring index (Fig.16). Decreased levels of foliar tannin were observed in the Japanese Cedars growing in the polluted areas. The inhibition of the shikimate pathway, by air pollution, was suggested by biochemical studies. Increased predation damage was observed in the foliage of Japanese Cedars with low tannin levels. The predisposed effects of air pollution were discussed with special reference to the inhibition of the shikimate pathway.

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Precipitation chemistry data were obtained in Phase -I Study of Acid Precipitation Surve y oJvapera n, 1986-4988 by Japan Environment Agency. Precipitation was sampled over Japan by filtrating bulk samplers as well as wet/dry samplers. Annual mean pH value at each station ranged from 4.5 to 5.2 with a mean of 4.7. Major ion concentrations averaged over all the samples were as follows; SO₄^2-: 2.64, NO₃-: 0.96, Cl^-: 3.82, NH₄⁺: 0.39, CO²⁺: O.52, Mg²⁺ : 0.26, K⁺: 0.18, and Na⁺: 1.97 μg/ml. Hydorogen-ion concentrationdid not vary significantly from site to site compared with those of the other ions. pH value of the rainwater was lower in the western Japan than in the eastern Japan, but the concentrations of the other chemical composition were higher in the eastern Japan. The equivalent concentration ratio of Cl^-/Na⁺ in the rainwater was nearly equal to that of sea water, and those of NO, -/nss-5042- and NH₄⁺/nss-Ca²⁺ were O.35 and 0.96. We interpret that the pH values gradu ally decreased with an increase in the equivalent concentration of {(NO₃^-+nss-SO₄^2-)}-{(NH₄⁺+nss-Ca²⁺)}.

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Sulfur isotopic ratios (δ³⁴S) of sulfate in atmospheric deposits (wet and dry deposits) and of the possible source materials have been measured in an attempt to investigate the source of sulfate in the atmospheric deposits in Niigata prefecture, Japan. Seasonal variations of the 3 HS values and their relation to chemical composition of the atmospheric deposits are discuss ed taking into account the δ³⁴ values of sulfur originating from seasalt, oil and coal combustion, biogenic activity and volcanic gases. The δ³⁴S values of sulfate show a remarkable seasonal variation along with seasalt contribution in the atmospheric deposits. The δ³⁴S_nss values calculated for non-seasalt sulfate in the deposits also show a seasonal variation. The δ³⁴S values of gas exhaust SO₂ from main local anthropogenic sources do not entirely ag ree with the δ³⁴S_nss values. It is inferred that sulfate in the atmospheric deposits contains sulfur not only from seasalt and local anthropogenic sources but also from some other sources which emit the isotopically heavy sulfur in larger proportions.

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Precipitation was sampled on a weekly basis in Kosugi, Toyama Prefecture fro m 1987 to 1989 with filtrating balk sampler (fb) and wet/dry sampler (w/d), both of which were equipped with heating device to melt snow sample on collection funnel. Volume-weighted mean pH for the study period was 4.6 (w/d) and 4.7 (fb). An annual mean equivalent concentration ratio of (H⁺+NH₄⁺+ non sea salt (nss-)Ca²⁺) to (nss-SO₄^2-+NO₃^-) was 1.0 4 (w/d) and 1.0 2 (fb), which strongly suggest that the balance o f these five species determined the pH at Kosugi precipitation. Concentrations for nss-SO₄^2-, NH₄⁺, and nss-Ca²⁺ increased during December to April. Annual depositions of the major ions were as follows: nss-SO₄^2-; 4.0 (w/d), 4.3 (fb), NO₃^-; 1.8 (w/d), 2.2 (fb), H⁺; 0.053 (w/d), O.44 (fb), NH₄⁺; O.67 (w/d), 0.83 (fb), nss-Ca²⁺; O.52 (w/d), O.73.(fb) g⋅m^-2⋅y^-1. The deposition w as influenced by strong winter monsoon. A multiple regression analysis of fb data demo nstrates that nss-SO₄^2-, NO₃^-, nss-Ca²⁺ and NH₄⁺ determine the pH, which was consistent with the equivalent ratio analysis. Principal component analysis showed probable sources of the ions.

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Chemical tests of individual aerosol particles and residues of fog droplets wer e performed on top of Mt. Norikura in order to examine chemical change of aerosol particles during the formation of acidic fog droplets. In this experiment, aerosol particles and residues of fog droplets were collected on electron microscope grids with a two-stage impactor after passing through the diffusion dryer. The presence of SO₄^2-, NO₃^- and NH₄⁺ in these particles was examined with an electron microscope using thin film chemical methods. It was found that chemical change of aerosol particles during the formation of acidic fog varied from fine particles to coarse particles. NO₃^- was detected only in aqueous liguid particlles and fog droplets near and in fog.

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In mountainous sites, acid fog is formed very frequently and lasts long. We collected fog samples at the midslope of Mt. Ohyama in the southwest of the Kanto area using a stringtype collector. The pH, conductivity, and the concentrations of major ions (Cl^-, NO₃^-, SO₄^2-, K⁺, Na⁺, Ca²⁺, Mg²⁺, and NH₄⁺) were measured. Rain water and aerosol were also sampled in Mt. Ohyama and Yokohama city, analyzed, and compared with the fog data. The fog samples in this work ranged in the pH value from 2.61 to 7.00 and the me an value was 3.95. The high salt concentration as well as the high acidity in fogwater will cause serious environmental problems. The pH of fogwater is lower than that of rainwater and the equivalent concentration ratio of nitrate to sulfate is about unity in both fogwater and rainwater samples, while the ratio was much less than unity in the aerosol samples. The concentration ratio of chloride ion to sodium ion in fogwater was almost equal to the ratio in sea salt but sometimes it was much higher than unity because of absorbing gaseous hydrogen chloride. The ion concentrations in fogwater were high at the beginning Of a fog event, decreased with time, and increased again at the end of the event. It was ascertained that the air pollutants (acid gas, ammonia, and aerosol) absorbed in fogwater were scavenged rapidly because the ionic loadings in air decreased rapidly at the beginning of a fog event. The pollutants scavenged from air were loaded on the leaf and the earth surface as the droplets with high solute concentrations although their loading amounts were small.

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Since 1985, the 40% to 50% of rain water was acid rain whose pH value showed lower than 5.00, in the data obtained at north district in Nagoya where our insititute is located. The concentration of nitrate and sulfate anions in the rain water and eluted water taken from underground at 15 cm have been measured continuously. The relationship of these anions between rain water and eluted water was discussed on the data taken from June 1989to June 1990. An average pH value of rain water was 5.18 for 69 rain falls. The rain water samples whose pH was lower than 5.00 were obtained on 34 rain falls and those whose pH was higher than 5.00 were obtained on 34 rain falls. The sample soil tested was taken from the garden of our institute as city garden soil, and forest soil, sea coast sand, and river bed soil were also tested in comparison with city garden soil. It was observed that most hydrogen ion put into the soil by rain fall was neutralized with the soil buffer action, and the concentration of hydrogen ion in the eluted water seemed to be regularized by the chemical equilibria between eluted water and each soil. On the other hand, the nitrate and sulfate anions showed dynamic seasonal change in the eluted water from city garden soil. The concentration of these anions in the eluted water decreased in spring and summer, and increased in autumn and winter. It depends on the growth of trees and grasses in the tested soil box. Such seasonal change of nitrate and sulfate anions in the eluted water must be considered as one of the factors, when a protecting technique is performed against acid rain damage to the plants.

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The rain waters in Tokushima city from June 1988 to May 1989 were analyzed concerning pH value, electric conductivity (EC), and concentrations of some ions. There was a V-shaped relationship between pH and EC that had minimum value at pH 5.6-6.0. Namely, EC increased with the decrease of pH under the value, whereas it increased with the increase of pH value at pH more than 5.0. There were similar relationships between pH value and sulfate, nitrate, calcium, or ammonium ion concentrations. Moreover, there was a good relationship between sulfate and nitrate ion concentration. The rain waters in typhoon contained high concentrations of chloride, sodium, and calcium ions.

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Ion components in dustfall samples collected with deposit gauge in Kitakyushu City in the period from October 1987 to September 1989 were analyzed to discuss the deposition and seasonal variation of SO₄^2- and Ca²⁺. High deposition of excess-Ca²⁺(ex-Ca²⁺) were observed in the inductrial area, and the amount decreased with increasing distance from the area. Depositions of ex-SO₄^2- showed a similar tendency. Deposition of ex-SO₄^2- increased during spring and summer, and decreased in winter months. Deposition of ex-Ca²⁺ increased in the early spring (Fig.2). The positive relationship between the precipitation amount and deposition of ex-SO₄^2- was found (Fig.3). On the other hand, deposition of ex-Ca²⁺ increased with increasing precipitation amount of up to 100-150 mm, but the deposition gradually decreased with precipitation amount over those values (Fig.3).

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