Suspended particulate matter SPM 10 (≤10μm) was collected at ca 20 m above the ground in the south of Saitama prefecture in April of 1997-June in 1999. SPM 2.5 (2.7±0.6 μm) was collected at the same location in January-February February in 2000. The analysis of 20 elements in the SPM was performed by the instrumental neutron activation analysis by using the TRIGA II nuclear reactor of the Rikkyo University. Most elements other than Cl and Br have a few sharp peaks in March-May and October-November, which resulted from strong winds during the change of season. The quotients of the molar ratios [Cl]/[Na] and [Br]/[Na] in the SPM divided by the ratios in seawater clearly showed cyclic behavior with the change of season, respectively. The concentration ratio [Cl]/[Na] remarkably decreased with the increase of wind speed with a gradient-19%/(ms^-1) compared to the averaged [Cl]/[Na] in winter. The plots of log [Cl]/[Na] and log [Br]/[Na], in the range 0.5-3 (ms^-1), against reverse temperature give the apparent enthalpy of adsorption H=ca 84 (kJ/mol) for Cl and ca. 66 (kJ/mol) for Br. The values are approximately consistent with the adsorption enthalpy of simple organic Cl-compounds on active charcoal, in accordance with the Landolt-Börunstein. In the desorption experiments of Cl in the SPM 2.5, the volatile species of Cl amounted to ca 60% in total chlorine and the activation energy of desorption, E_d, was estimated to be equal to ca-65 (kJ/mol). The Cl and Br results in SPM were discussed from the viewpoint of the adsorption of volatile Cl-and Br-species in SPM.

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The influence of nitrogen dioxide (NO₂) under humid condition on the determination of formaldehyde in air was examined using the 2, 4-dinitrophenylhydrazine (DNPH) method. In humid air, NO₂ reacts with DNPH, yielding 2, 4-dinitroaniline and 2, 4-dinitrophenylazide as the main reaction products. 2, 4-Dinitroaniline and formaldehyde-2, 4-dinitrophenylhydrazone behave similarly when examined by cross-linked 5% phenyl methyl siloxane capillary column gas chromatography. Chromatographic separation was performed using a cross-linked methyl silicone column and an optimum column temperature program. The reaction between DNPH and NO₂ was hindered by using magnesium perchlorate cartridges as a desiccant, mildly heating DNPH coated cartridges to decrease relative humidity and especially by using 3, 3-dimethylnaphtidine coated celite as an NO₂ scrubber.

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High concentrations of NO₂ in urban areas of Japan are still a serious environment issue. In the Tokyo metropolitan area NO₂ levels are usually highest in wintertime. However in the Osaka area peak levels are observed in both spring and winter seasons. To clarify the NO₂ formation mechanisms for these high concentrations, a series of three-dimensional (3-D) field studies, including aircraft and laser radar observations, were conducted in April 1993 covering the Osaka region. The purpose of the present study was to develop a numerical simulation model capable of reproducing the extreme air pollution conditions in springtime Osaka and validate it using a 3-D field database of Osaka in April 1993.
Results of the validation study for the chemical transport model (CTM) were as follow:(1) CTM simulated observed temporal variations in NO_x, NO₂, and O_X (0₃), SO₂ and NMHC concentrations measuredat ground surface;(2) vertical profiles of pollutant concentrations such as, NO₂, O₃, and VOC species, measured by aircraft were reproduced by CTM;(3) the model exhibited temporal variations in NO_X, NO₃ and 0₃ concentrations measured at Mt. Ikoma; and (4) though background levels were high, this model accurately reproduced sulfate concentrations.
These results show that the CTM developed in this study is useful for simulating the dynamic behaviors of various air pollutants including NO₂ and suitable for analyzing the springtime air pollution in the Osaka area.

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In order to clarify the mechanism of springtime air pollution in the Kansai region of Japan, a series of numerical simulations using a chemical transport model developed by Ohara et al. (2001) was conducted. Result of the base-case sumulation showed that NO_X emissions from vessels over Osaka Bay and local wind circulation play an important roles in the formation of high springtime concentrations of NO₂ in Kansai.
A sensitivity analysis consisting of three sets of process analyses was subsequently conducted. The purpose of the process analysis was to understand the relative roles of background ozone (BG-0₃), photochemical ozone, transported NO₂, and primary emissions NO₂ in controlling NO₂ formation in the Kansai area. According to numerical experiments, the relative ratios of the production processes of surface NO₂ over the model domain were summarized as follows:(1) primary NO₂ emission was 10%;(2) transported NO₂ through the model boundaries was 40%;(3) the chemical production of NO₂ was 50%, which consisted of 60% produced by reaction with BG-0₃ and 10% loss due to photochemical processes. The simulated results also show that the primary source is surface ozone BG-0₃ rather than photochemical ozone.
The results of emission reduction experiments revealed that the relationship between NO_X reduction ratio and NO₂ concentration was almost linear in the urban area, but reduced NMHC emission yielded in sufficient results to determine reductions in environmental concentration of NO₂. The effects of BG-0₃ to NO₂ concentrations were great. NO₂ concentrations decreased with a decline in BG-0₃, and this tendency was especially marked under conditions of lower BG-0₃ level.

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To elucidate the generation mechanism and to establish a standard measuring method for condensed particulate matter from stationary sources, the properties of condensed particulate matter in heavy oil combustion flue gas were investigated using the duct test, by which the flue gas temperature was controlled.
The main results obtained were:
1) Dust sampled from high temperature locations was black, while condensed particulate matter sampled at low temperature locations was brown, and had a pungent odor.
2) Condensed particulate matter concentrations at low temperature locations were high 2-4 times grearter than samples from high temperature locations.
3) Condensed particulate matter appeared filmy in droplet formations ranging from 1 to 10μm in diameter.
4) The component ratio of organic and elemental carbon exhibited no obvious differences between condensed particulate matter and dust; the lavel of condensed particulate matter organic carbon was high at about 90%, while one dust sample was at about 70%. On the other hand, the levels of SO₄^2- in condensed particulate matter and dust were almost equal.

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