Equilibria between the nitrogen oxides and dilute aqueous solution are closely related with atmospheric chemistry and uptake process of these substances by living body. Chemical thermodynamics of the reactions of nitrogen oxides and aqueous solutions are studied in this report. The results are graphically illustrated to give the equilibrium concentrations of each species at 25°C. The reactions examined are as follows. H⁺+NO₂^-=HNO₂, 2NO₂+H₂O= NO₂^-+ NO₃^-+ 2H⁺ or 2NO₂+ H₂O= HNO₂+ NO₃^-+ H⁺, NO+NO₂+H₂O= 2NO₂^-+2H⁺ or NO+ NO₂+ H₂O= 2HNO₂, 3NO₂+ H₂O= 2NO₃^-+ NO+2H⁺, 3NO₂^-+ 2H⁺= NO₃^-+ 2NO+ H₂O or 3HNO₂= NO₃^-+ 2NO+ H⁺+ H₂O, NO₂+ NO₂^-= NO₃^-+NO or NO₂+ HNO₂= NO₃^-+ H+⁺ NO, 2NO+O₂= 2NO₂, 2NO₂^-+O₂= 2NO₃^- or 2HNO₂+O₂=2NO₃^-+2H⁺, 4NO+O₂+2H₂O=4NO₂^-+4H⁺ or 4NO+O₂+ 2H₂O= 4HNO₂, 4NO+ 30₂+ 2H₂O= 4NO₃^-+ 4H⁺, 4NO₂+ O₂+ 2H₂O= 4NO₃^-+4H⁺, 4NO₂^-+ 4H⁺+ O₂=4NO₂+ 2H₂O or 4HNO₂+ O₂= 4NO₂+ 2H₂O.Relative stability of NO₂^- and NO₃^- in aqueous solution are also discussed. NO₃^- is more stable than NO₂^-in solution where O₂ is not involved if the ratio of gaseous concentrations of NO/NO₂ is lower than ca. 10⁶. NO₃^-predominates over. NO₂^- in aqueous solution in equilibrium with O₂ at 0.2 atm.

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Measurements of concentration and size distribution of total aerosols, chloride, nitrate, and sulfate were made from 1979 to 1982 in Yokohama. The seasonal variation of concentration and size distribution of aerosols has been investigated. Aerosols were collected and size-fractionated by Andersen sampler. Size classified samples were extracted with distilled water and analyzed for chloride, nitrate and sulfate by ion chromatography.
As the results of 25 measurements, the averages of concentration and MMAD (mass median aerodynamic diameter) were 85.1 μg/m³ and 1.7 μm for total aerosols, 4.16 μg/m³ and 2.3 μm for chloride, 5.71 μg/m³ and 1.4 μm for nitrate, 6.69 μg/m³ and 0.65 μm for sulfate.
The seasonal variation of concentration and size distribution was observed for chloride and nitrate. In summer, both of their concentration peaks appeared in coarse particles about 4 μm dia. On the other hand, in winter, their concentrations increased not in coarse particle but in fine particles and their size distributions were fi ne mode. Sea salt particles were transported to urban air by the seasonal wind, so that the concentration of chloride in coarse particles increased in summer. Also, the reaction between transported sea salt particles and HNO₃ would occur in urban air. Therefore, the concentration peak of nitrate was observed in coarse particles in summer. As for sulfate, its concentration and size distribution did not change during all season, and most sulfate existed in sub-micron particles.

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Some novel devices have been developed based on the principle of cascade impaction for measuring particle size distribution of mist entrained in flue gas from wet scrubbers such as flue gas desulfurization plants. One of these is a cascade impactor equipped with cassettes combining the impaction plate, the inner wall and the jet nozzle, which is an in-stack type sampler. Conventional impactors can not measure the particle size distribution of mist because liquid particles impacted onto an impaction plate overflow around the edge of the plate. On the other hand, the cassette type cascade impactor can determine the mist size distribution because the cassettes retain mist drain in themselves even if the impactor is set either horizontally or vertically in a duct. In each cassette the inner wall can be easily divided from other parts, and therefore the cascade impactor enables one to estimate the wall loss in the impactor for solid dust sampling which has been in the vague and furthermore to carry out the simultaneous measurements for the particle size distribution and concentration of mist or dust in flue gas.

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In order to clear the photochemical reactivity of hydrocarbon vapour of commercial volatile petroleum products, the ultraviolet irradiation test of motor gasoline, jet fuel and petroleum naphtha vapour were carried out.
For the test, the laboratory smog chamber (6.64 m³) was controlled in light intensity 7 mw/cm² (k₁=0.41min^-1), temperature 30°C, relative humidity 50%, initial concentration HC 10 ppmC, and NO 1 ppm. Iradiation time was 4 hours.
The olefin contents in the gasoline vapour were distributed in the range of 0.30-35.78%, and the photochemical reactivity had a great difference among the kinds of gasoline corresponding the olefin contents. The reactivity of jet fuel and straight naphtha were very low, because of no olefin contents.
As the results, the photochemical reactivity index shows a good correlation with the olefin contents of vapour themselves.
For a representative gasoline vapour, initial HC/NO condition was varried in the range of 3-18 ppmC/ppm.The reactivity index like O_3max, NO_DR and NO_2FR increased as the HC/NO ratio increased.

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It is important to determine the representativeness of regional air monitoring stations and also develop a system which can provide the optimal siting for air quality management. In this study, the representativeness and optimal allocation of monitoring stations have been analysed under the assumption that the concentration distribution calculated by diffusion model is the true value. For determination of the optimal site, the following two principles are applied
(1) Location of the stations which enables to obtain the data more accurately in the highly polluted area.
(2) Location of the stations which covers wider area by smaller number of stations.
Existing monitoring network and optimal stations are evaluated by four criteria; population dosage factor and so on. As shown in case study for a typical area, the method proposed here is effective for determination of the representativeness and optimal allocation of monitoring stations.

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By using a smog chamber with a long-path infrared spectrometer, a photochemical reaction for C₃H₆-NO-SO₂-dry air system was investigated by varying the concentration of each reactant. When NO₂ formation rate was plotted as a function of initial C³H₆/NO ratio ([C₃H₆] ₀/[NO] ₀), two straight lines were obtained. In the range of [C₃H₆] ₀/[NO] ₀>6, the slope, indicating the photochemical reactivity of C₃H₆, greatly decreased due to the presence of SO₂, while the decrease in the slope was relatively small in the range of [C₃H₆] ₀/[NO] ₀<6. O₃ maximum concentrations observed were not much affected by SO₂ and were not related to [C₃H₆] ₀/[NO] ₀ in the same manner as to the NO₂ formation rate.
SO₂ depletion (oxidation) rate was found to be first order in SO₂ initial concentration. The rates increased linearly with the increase in [C₃H₆]/[NO] 0 in the range of smaller than 5 and became less dependent on the ratio. It was also confirmed that the rate was related to the NO₂ formation rate all over the [C₃H₆] ₀/[NO] ₀ range studied (2-20). OH radical concentrations were calculated from observed C₃H₆ depletion rate and O₃ concentration and the change of the OH concentration with [C₃H₆] ₀/[NO]₀ was relatively small.It was found that the SO₂ depletion rates calculated from the OH concentrations did not exceed 20% of the SO₂ depletion rates observed all over the [C₃H₆] ₀/[NO] ₀. It was clear the oxidation of SO₂ with Criegee intermediates was predominant under the present experimental conditions.

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In recent years methods for the assessment of environmental impacts of air contaminants released and dispersed in a region of complex terrain have been focused on. For a variety of economic and geographic reasons, industrial emmisions have been released at low heights with respect to the terrain features. The question, therefore, of how well air pollutants will disperse when transport processes are constrained by terrain features has been issued. In this respect, we have been searching for a practical model to predict pollutant dispersion in complex terrain together with experiments persued in such region.
This paper presents major part of a prediction system for air pollution-one of the serious matters exerting an adverse effect on the living environment as a result of, for instance, construction of incineration facilities-taking the effect of complex terrain into consideration.
In this system, the field of wind flow in the area concerned is determined by the improved potential flow model. In connection with the system the gaseous tracer experiments were conducted to gather the dispersion characteristics data in the region of complex terrain. These data were also used to confirm the result of the system by comparisons of calculated values with measured ones. As a result of the estimation of wind field, the proposed model is found to be applicable to the real problem.

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An instrument for determining the particle size distribution of suspended dust in environmental air has been developed by coupling the particle impaction method and the piezoelectric sensing technique. Two kinds of Test impactor are constructed by modifying the Andersen sampler which is widely utilized for air pollution research.
The size of Test impactor I is similar to that of the Andersen sampler which deals with the flow rate of 28. 3l/min, and the size of Test impactor II is fairly smaller than the former, which is operated properly at the flow rate of 1l/min. They are, however, designed so that the gas velocity through each stage may get higher as the sample gas goes down the lower stage by making the number of the jet nozzle in each stage less instead of making the nozzle diameter in each stage smaller.
The frequency properties of the piezolectric sensors in each stage have been investigated using uranine particles which enable the quantitative analysis by utilizing the fluorescence photometry. It has been. confirmed that the instrument can measure the particle size in a very short period by using the mass sensitivities in each stage, though they are different from each other.

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On the second report, in order to improve and to increase the separation efficiency and in order to devise the plan of a new type of cyclone dust collectors, as a fundamental research material it is very important to consider the concentration distributions of the fine solid particles which are related to the size distributions of the feed dust. Then the author described the concentration distributions of the solid particles for the three kinds of the cyclones as follows; the first, the returned flow type of the axial inlet cyclone (D₁=254mm) which had the guide vanes and designed by _??_ (1971); the second, the returned flow type of the tangential inlet cylindrical cyclone (D₁=290mm) by Ogawa, A., J. College of Eng., Nihon Univ.(1980); the third, the returned flow type of the tangential inlet cyclone (D₁=190 mm) by Mothes, H., Sievert, J., Löffler, F., J. Aerosol Science (1982). The test dusts were coal dust (X_R50=8 and 27μm), flyash (X_R50=18μm) and lime-stone (X_R50=1.4μm), respectively.
Then in order to elucidate the more detailed descriptians of the behaviours of the solid particles in the turbulent rotational flow in the confined vortex chamber, the author briefly described the important mechanical similarity rules of the solid-fluid mixture turbulent flow by an extract of a paper of _??_ (1982). And also in connection with the motion of the fine solid particles in the turbulent rotational flow in the vortex chamber of radius R1, the Prandtl mixing length l and the Kolmogorov micro scale η were empirically estimated by Ogawa, A.(Pacific Meeting of Fine Particle Society, Honolulu, 1982) as follows; l/R₁= 6×10^-6·Rec·(γ/R₁), η/R₁= (7/Rec)·(γ/R₁), where cyclone Reynolds number was defined as Rec=Qo/Hi.·ν.
In addition to this, the characteristics of the collection efficiencies for the three types of the retuned flow types of the cyclones (axial inlet type with guide vanes, 360° spiral inlet type, 180° spiral inlet type) by the experiments of _??_, et al.(1971) were described. And still more the empiricalequations of the fractional collection fficiencies fbr the three types of the cyclones by _??_ (1967) were described.

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