Long range transport of air pollutants and acidification of rain water have drawn much global attention in recent years. In this review were summarized the informations so far obtained for the changes of chemical properties of rain by atmospheric nitrogen oxides (NO_x).
Acid rain is caused by the emission of SO_x and NO into the atmosphere during fossil-fuel combustion, however much more attention being focussed on the role of NO_x (HNO₃: hydrolysis and oxidation product from NO_x), recently. It seems that NO₃^- and NO₂^- in rain water are an useful index for the estimation of air quality.

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Photocatalytic effects of TiO₂, one of metal elements in atmospheric particles, on trans-2-C₄H₈-0₂ and trans-2-C₄H₈-N0₂-air photochemical reactions have been investigated using a flow-type reactor.
Trans-2-C₄H₈ was rapidly oxidized to CO₂ by O₂ in the presence of TiO₂ only under photoirradiation. From the O₂ partial pressure dependence of CO₂ formation rate, O₂-species adsorbed on TiO₂ surface generated under photoirradiation may contribute to the complete oxidation of trans-2-C₄H₈. Addition of NO₂ to the reaction system remarkably reduced the CO₂ yield, indicating that NO₂ depressed the photocatalytic oxidation activity of TiO₂. On the other hand, from the comparison of the results with those obtained for a gas-phase homogeneous photochemical reaction (trans-2-C₄H₈-NO₂-air) (the order in the yield of the products: CH₃CHO>MEK EPB>CH₃ONO₂-CO>CO₂), due to the presence of Ti0₂, MEK+EPB yield remarkably decreased but CH₃ONO₂ formation was enhanced and HCN appeared. It is inferred that active species arising from NO₂ (or NO) adsorbed on TiO₂ may have lower activity in complete oxidation than O₂-, but may retain some activity in further oxidation of the partially oxidized compounds and in formation of CH₃ONO₂ and HCN. This reasoning was not in conflict with the experimental results obtained for a heterogeneous photochemical reaction between TiO₂ and a reactant which has passed through a gas-phase photochemical reaction beforehand.
The results presented here may suggest the importance of the heterogeneous chemical reactions in the atmosphere to understanding the transformation of hydrocarbons (especially, decomposition rate of hydrocarbons to CO₂) and the cycle of nitrogen on a global scale.

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The gas chromatographic determination of odorants (sulfur compounds, lower aliphatic amines, carbonyl compounds, hydrocarbons, lower aliphatic mono alcohols and phenols) in ambient air near of an ALC factory was investigated by using two preconcentration methods, namely cold trapping with liquified argon and room temperature adsorption trapping with porous polymer beads, such as Tenax-GC. However, the odorants responsible for characteristic musty, heavy and dusty odor quality from the ALC odor source factory were undetected by the gas chromatographic (GC) methods.
Whereas, by sniffing the ALC characteristic odor and the odor producing from 40% sodium hydroxide aq. soln. for Kjeldahl alkaline digestion of ammonium and amine salts, the resemblance of these odor were recognisable by trained odor panellists in preliminary test in this study. However, the results of GC determination of the odorants from the ALC factory and their generated from the 40% sodium hydroxide aq.soln was different.

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The technique of dust sampling in flue gas emitted from stationary sources is widely used for purposes of controlling air pollution and evaluating the performance of dust collectors. In the dust sampling, the gas sample must be aspirated into the nozzle of the sampler at the same velocity as that of the stack gas to avoid inertial segregation.
For the purpose of confirming the effects of anisokinetic sampling of dust concentration and examining the equations estimating the effects, a lot of anisokinetic dust sampling were carried out over a wide range of sampling ratio. For the oil-fired flue gas 36 samples by anisokinetic sampling and 11 samples by isokinetic sampling, and for the test dust-laden gas 48 samples of coal fly ash, 24 samples of calsium carbonate and 24 samples of titanium dioxide were obtained. For larger particles in the test dust-laden gases the effects of anisokinetic sampling are considerably large, while for fine particles of approximately 0.2 pm the effects are negligible, which proves that isokinetic sampling is not necessary for oil-fired flue gases.
These results were compared with the well-known estimating equations proposed by S. Badzioch ('60), H. H. Watson ('54), C. N. Davies ('54), G. S. Mirrell ('75) and Yoshida et al.('76). It has been confirmed that the results agree fairly well with the inclination calculated from the Davies' equation and the theoretical resolution by Yoshida et al. The Dav ies' equa tion may be recommended for estimating the errors of anisokinetic sampling because it can be easily made use of.

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The photochemical reactivities of non-methane hydrocarbons in vehicle exhaust were evaluated by linear summation method and ultra violet irradiation test. As the linear summation method, Altshuller's reactivity scale, R_s, and OH radical reaction rate constant, K_OH, were used with the analytical results of non-methane hydrocarbons.
The bellows type smog chamber of 6.64 m³ was used for irradiation test. The test conditions were as follows: ultra violet intensity 7 mw/cm²(k₁=0.41 min^-1), temperature 30°C, relative humidity 50%, initial concentration HC 10 ppmC, NO 1 ppm, irradiation time 4 hr. The NMHC complexes for evaluation, having approximately the exhaust compositions of the running condition, were prepared by standard gas and reagents. The vehicle for the test was the typical passenger car which was equipped with 3 way catalyzer and exhaust gas ecirculation system and was drived on a chassis dynamometer.
The results of the linear summation method showed good correlativity with the irradiation test results, especially the correlativity between K_oH method and the irradiation test was fairly good and the correlation coefficients were about over 0.9. As the result, it was clarified that the linear summation method by K_oH was very effective for the evaluation of photochemical reactivities of NMHC in vehicle exhaust gas. Actually, as the result of the evaluation of some vehicle exhaust gases, which were drived under the various running conditians, it was found that the photochemical reactivities of NMHC in exhaust gas varied with the running conditions.

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The photochemical reactivities of 11 kinds of commercial paint solvents were investigated by smog chamber irradiation test and linear summation method. For linear summation methid, the mole fraction, Altshuller's reactivity scale, OH radical reaction rate constant and reactivity indices of each hydrocarbon were used. Altshuller's reactivity scales and OH radical reaction rate constants of oxygen contained hydrocarbons were estimated by use of the regression formula of nitrogen oxide depletion rate with the scale and the constant of hydrocarbons, which were already reported.
The photochemical reactivities of 11 kinds of commercial paint solvents were in the range of 2-4 by 5 graduation method, which were proposed by Suyama et al. The correlation of reactivity between irradiation test and linear summation method showed high correlativity. Especially in the case of OH radical reaction rate constant, the highest correlation was obtained. The coefficient of correlation was 0.970-0.918. As the result, it was found that linear summation method was very useful for the evaluation of photochemical reactivity of paint solvents, especially in the case of OH radical reaction rate constant.

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An area covering a radius of 50 km centered on Mt. Sakurajima was divided into 10 regional groups by concentric circles and the mortality figures for all causes and for selected respiratory diseases covering the 15-year period 1968 to 1982 were compared among these regional groups. Moreover, patterns for the annual variation of the corrected mortality rates for all causes and for the respiratory disease combined for bronchitis, bronchial asthma and emphysema were examined in relation to the volcanic activities of Mt. Sakurajima. Results are as follows:
(1) In the regional groups within about 30 km from Mt. Sakurajima, the number of deaths from bronchitis, emphysema or influenza exceeded significantly the expected mortality for the standard population. Moreover, a consistent declining gradient in the standardized mortality ratio for each of these categories of disease was observed with increasing distance from Mt. Sakurajima among these regional groups, suggesting that the volcanic activities could be associated with the increased mortality from these categories of disease.
(2) The number of deaths from all causes, bronchial asthma, acute bronchitis, lung and bronchial cancer or pulmonary tuberculosis also exceeded significantly the expected mortality in the area as a whole, while the number of deaths from pneumonia was below the expected one not only in the area as a whole but also in each of the regional groups. However, no consistent declining gradient in the standardized mortality ratio for each of these categories of disease was observed with increasing distance from Mt. Sakurajima among the regional groups, suggesting that the volcanic activity was without effect on the mortality for these categories of diseases.
(3) In the regional groups near Mt. Sakurajima, a distinct rise in corrected mortality rate of the respiratory disease combined for bronchitis, bronchial asthma and emphysema occurred in the year (1974) accompanied by the peak in the number of volcanic eruptions, suggested a causal relationship of volcanic air pollution to the mortality for the selected respiratory diseases in the area near Mt. Sakurajima.

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The volcanic ashes erupted from Mt. Sakurajima were collected together with rain water monthly from April 1981 to March 1984 at 14 locations in Kagoshima city and at 7 locations in Sakurajima.
After the sample was filtered, the residue was dried and weighed, and the filtrate was analyzed for SO₄^2-, Cl^- and water-soluble matter.
The amounts of sulfur oxides absorbed on PbO²-candle were measured at the same 19 locations as with ashfall measurement.
The experimental results showed that the average amounts of volcanic ashes which fell at 7 locations (in Sakurajima) in the last three years was 2040 ton/km². month, which was larger than the average in the previous three years (1978-1981) of 1490 ton/km². month.
On the same token, the average at 14 locations (in Kagoshima city) in the last three years was 112 ton/km². month. It was nearly equal to that obtained in the previous three years at the same locations.
The highest amount of volcanic ashfall recorded at a location in the last three years was 19, 400 ton/km².month, which was recorded at Kurokami Middle School in October, 1983. This is also the highest amount which was recorded during the last six years.
The highest amount of sulfur oxides absorbed on PbO2-candles in the last three years was 2.43 mg/100 cm² day, which was observed at Arimura-haisuichi in November, 1981. Acid.fication of rain was observed at all locations, and the highest acidity of the rain was in terms of pH 2.8 which was recorded at Sakurajima Middle School in November, 1983.

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