Conversion factor from NO₂ to NO₂^- in alkaline solution was measured. Conversion factor, [NO₂^-]/([NO₂^-] + [NO₃^-]), increased when the concentration of hydroxyl ion increased. In high pH solution, the relationship between conversion factor and hydroxyl ion concentration was
f=(1+50[OH-])/(2+50[OH-])
Sample NO₂ gas was prepared by NO₂ permeation tube and N₂ gas. Its concentration was about 1.2ppm. NO₂ was absorbed to various concentration of sodium hydroxide solution through G2 glass fritted bubbler. The solution was divided into two parts after neutralization. One was added with modified Saltzman reagent for determination of NO₂^- concentration and the other was passed through Cd-Cu reduction column in order to determine NO₃^- concentration.

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Calculations of the one-dimensional CO-CH₄ transport/chemistry model were performed to investigate the sensitivity of the OH vertical profile to various factors. The boundary conditions at the earth's surface and the tropopause are discussed. The results show that the liquid-phase or soil-phase resistance dominates the mass transfer of both CO and CH₄ between the atmosphere and the earth's surface. At the tropopause, the CO and CH₄ fluxes are set approximately equal to the value at the previous time step in the numerical calculation.
Using photolysis rate coefficients that increase with altitude modified the OH vertical profile so that the maximum value was at mid-troposphere altitudes. Increasing the CO concentration caused a decrease of the OH concentration, and the OH profile was very sensitive to the NO_x profiles. The calculated OH profiles are compared with those from other investigations and also with some available measurements. Although the available measurements of the OH profiles are limited, the calculated OH profiles agree fairly well with them.

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Eighteen airborne particulate samples, which were collected with a low-volume type of Andersen Air sampler at an appropriate time interval in the period from 1974 through 1977 in Sakai, Osaka, were analyzed for 37 elements. The analytical results were interpreted by “chemical element balance method”, considering seven main source components, namely, soil particles of local and global origins, marine aerosols, suspended particles from iron-and-steel industry, refuse incineration, fuel oil combustion and gasoline engine automobiles, and taking seven elements, Na, Al, K, Sc, V, Mn and Pb, as index elements. The contributions to the atmospheric concentrations of total suspended particulate matter (TSP) and various elements from the main componenets were calculated as in previous similar studies, and in addition to this, the analytical results were discussed in relation to the particle size distribution. The results of prediction on the size distribution and related discussions are reported in the succeeding article.
The predicted atmospheric concentrations agreed with the observed ones for major elements within a factor of 1.5, with the major exceptions of S, Cl, Ni, As, Se, Cd, Sb and W. Possible explanations for the disagree ments between the predicted and observed concentrations and some remedies for making better prediction by chemical element balance method are presented. The sum of the percent contributions to TSP from the seven main components was calculated to be about 50%. Among the other main sources, secondary aerosol formation from SO₂, NO_x and hydrocarbons and diesel engine exhaust appear to be the most important. Besides, . emissions from various small aerosol generating factories cannot be neglected.

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The effects of ozone on apparent photosynthesis, photorespiration and dark respiration were determined in poplar (Populus × euramericana cv.'I 45/51') leaves. These results were as follows:
(1) The lower order leaves (at the 35th day after unfolding) fumigated with ozone at 0.10, 0.15, 0.20 or 0.25 ppm had apparent photosynthetic rates reduced by 3, 7, 28 and 34%, respectively, after 5 hours exposure. Apparent photosynthetic rates were recovered within a few days after fumigation.On the other hand, photosynthesis of the upper order leaves (at the 20th day after unfolding) were not affected with 0.10 or 0.20 ppm ozone for 5 hours exposure.
(2) After fumigating to poplar cuttings with 0.10 ppm ozone for 5 hours a day, 5 days a week, during the Land 2-week treatment period, apparent photosynthetic rates of the lower order leaves were reduced by 33% and 59% respectively, and photorespiratory rates were reduced by 19% and 40% respectively. But, dark respiratory rates were stimulated by 15% during the 1-week treatment. On the other hand, those of the upper order leaves were not affected by ozone fumigation.
(3) Apparent photosynthetic rates of injured leaves shown as “damage degree 3 or 5” by fumigations with 0.10 ppm ozone, 5 hours a day for 5 days, were depressed 10% and 22%, respectively, by fumigating again to 0.10 ppm ozone for 3 hours.
(4) When poplar cuttings grown in non-filtered air greenhouse and filtered air greenhouse were fumigated with 0.15 ppm ozone for 3 hours, apparent photosynthetic rates of the lower leaves in non-filtered air greenhouse were reduced by 11%, but those in filtered air greenhouse were not affected. At one day after fumigation, the rates in non-filtered air greenhouse were reduced by 28%.

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An empirical model to estimate NO₂ pollution concentration in the atmosphere has already been proposed in the previous report. The structure of the model was formed by an theoretical consideration and the model was not always practically useful one. Therefore, in this study, the model was identified and improved by the use of the observed data such as NO₂, NO_x and O₃ concentrations, emission intensity and meteorological conditions.
Empirical models are classified into two kinds. One is identified to estimate annual mean NO₂ concentration, and the other is identified to estimate hourly mean NO₂ concentration.
Each model contains several parameters. Parameters in the former model were evaluated for each applying case of the model for general environment and for near roadway environment.
Parameters in the later model were evaluated for each category of terrain condition and wind direction too.
The reliability of estimation by these models was verified by statistical methods.

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