Three-hour sample of the atmospheric aerosol over Sakai were continuously collected on two kinds of filter, made of teflon and quartz, by using the automated sampling system. Filter samples obtained during Dec. 9 to 14, 1986 were analyzed by instrumental neutron activation analysis. ion chromatography and pyrolytic carbon analysis, and more than thirty major to trace constituents of the atmospheric aerosol were quantitatively determined.
Major constituents were C, Cl, NO₃^-, SO4₂^-, NH₄⁺, Ca, Al, Fe, Na, K and so on. In addition to the constituents from primary emission sources such as motor vehicles, soil and dust, secondary-formed particles sich as particulate nitrate, sulfate and ammonium chloride, contributed much to the concentration of the atmospheric aerosol.
Concentrations of atmospheric particulate pollutants near the ground surface were closely connected with weather conditions. Diurnal variations of these concentrations were different with each other, because some of these pollutants are primary particles from different emission sources, which have different particle sizes, and others are secondary-formed products, which were formed from different precursive gaseous matters and through different reaction mechanisms with each other. The bimodal pattern of diurnal variation in concentration of the atmospheric aerosol is mainly caused by that of C, which is the most major constituent. Constituent elements of Al, Ca, Sc, La, Ce, Sm, Th and so on, highly correlated with each other, and it is considered that these originated mainly from soil and road dust, because these concentrations rapidly dropped when it rained.
The wind direction, when concentrated V, Ni, Co and Mo were observed in the atmospheric aerosol, indicated that particles bearing these elements came from the coastal industrial zone, where petroleum refining and petrochemical complex plants were located. That is to say, particles containing highly concentrated Ni, Co and Mo together with V were emitted from fuel oil combustion and petroleum refining. By a similar reason, highly concentrated W was due to particles emitted from the rail-way near the sampling site.
Minor constituent elements, such as As, Se, Br and Sb, showed violent variations in concentration, and none of these highly correlated with the other constituents. This suggests that these elements are probably adsorbed and/or condepnsed on the surface of fine particles emitted from fuel oil combustion.

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Wintertime high concentration of NO₂ was analyzed by using a two-dimensional meso-scale numerical model and an Eulerian type atmospheric diffusion model (photochemical grid model) which includes photochemistry. A typical local wintertime circulation was simulated, and together with typical emission strengths from the central Tokyo was used for the analysis of representative wintertime pollutant characteristics. The NO₂ formation nudget (ppb/min) (contributions from atmospheric diffusion and chemical reactions) was examined. The results show that all of the increase in NO₂ concentration is due to chemical reactions with the latter peaking at about 1030 JST and 1630 JST. These peaks are stronger than the decrease due to the atmospheric diffuion (meteorological terms) and results in an increase of NO₂ concentration at these times. Detailed data analysis show that the chemical contribution from the HO2+NO→NO₂ reaction is important in the morning hours, while the NO+ O₃→NO₂ reaction plays an improtant role after 1400 JST. A sensitivity analysis by changing the source emission intensities for NMHC and NOx is also included. The nonlinear relationship between NO₂, max, O₃, max and emission intensities was analyzed. It is found that the individual controls on NOx and NMHC are a strongly non-linear on NO₂, max (i. e. a 30% reduction gives only a 18% decrease in NO₂, max). The simultaneous reduction of NOx and NMHC shows a 1: 1 relationship between NO₂, max and emission strength.

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Rain water samples from initial and latter rainfalls were acidified to 0.2 M HCl, or untreated, and filtrated through a membrane filter with a pore size of 0.45μm, or centrifuged at 3000 rpm. The untreated and treated samples were subjected to fluorometric determination of dissolved aluminum (Al_d) at pH 4.5 with 8-hydroxyquinoline-5-sulfonic acid. The total aluminum (Al_t) was determined after hydrofluoric acid decomposition of the sample in order to obtain the undissolved aluminum (Al_u) from Al_t-Al_d. Al_d in the untreated sample decreased with increasing rain precipitation (P); e. g., 200nm ml^-1 in the initial rainfall (P= 0.5mm) and 5ng ml^-1in the latter rainfall (P>5mm). The acidification caused increase of Al_d by the dissolution of Al from solid particles in the samples. The filtration or centrifugation at pH 4 gave negligible decrease of Al_d, while these treatments at pH 5 gave much more decreases up to 48%. Polystyrene bottle was best suitable for the sample storage because of negligible loss of Al_d. During the storage, Al_d increased for most of the untreated samples. The filtration or centrifugation removed about 90% or more of Al_u from the samples in the ixtitial rainfalls, which could be stored for 3 days without significant change of Ald. In the latter rainfalls, the removals of Al_u were 30 to 80%, and residual particles caused increase of Al_d during the storage. The inductivelycoupled plasma atomic emission spectrometry gave higher Al_d than the fluorometry. The change in Al_d by the sample treatment and storage is discussed based on the adsorption of aluminum on the filter and particles and the dissolution of the particles. The fluorometry used is recommended for the rapid determination of Al_d down to 1ng ml^-1 without any pretreatment and storage.

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The authors have developed newly designed semi-automatic rain droplet generator system for long-term rain exposure experiments. This system generates 2.5 mm of rainfall intensity in an hour event with droplets of about 1 mm in diameter. Its spatial variation of precipitation was significantly smaller than that of the conventional mist type rain systems.
Four exposure experiments with simulated acid rain (SAR) were conducted during the growing season from 1991 to 1993. Total of 46 young tree seedlings planted in pots were exposed to SAR containing sulfate, nitrate and chloride with the weight percentage ratio of 2: 1: 1 for 3 or 4 months. SAR stock solution was volumetrically diluted. Designated pH values were 2.0, 2.5, 3.0, and 4.0. Deionized water of pH 5.6 was used as the control and a diluent of SAR stock solution.
All seedlings exposed to SAR of pH 2.0 showed necrotic visible foliar injuries or defoliation. Since Japanese larch, which is only one deciduous conifer species in the 11 conifers examined in this report, was defoliated at pH 2.5 and lower, it was classified as the most sensitive conifer species to low pH of SAR. Other conifers except this species did not show any visible symptoms at pH 3.0 or higher.
Seven of 14 evergreen broad leaf tree seedlings and 14 of 21 deciduous broad leaf tree seedlings showed foliar injuries at pH 3.0. Among deciduous broad leaf tree species exposed to SAR of pH 2.0, 7 species were almost defoliated, and 3 species were dead at the end of the exposure experiment. However, evergreen broad leaf trees did not show such a severity of the symptoms at pH 2.0. Exposure of SAR of pH 3.0 caused premature defoliation and shot hole symptom in Prunus species, especially P. x yedoensis and P. armeniaca. Any species did not show visible injury symptoms after the exposure to SAR of pH 4.0.
The results obtained in the experiment suggested as follows. Conifer trees were relatively tolerant to acidic rain exposure than broad leaf trees. Deciduous broad leaf trees were relatively more sensitive than the evergreen broad leaf trees. Current acidic rain monitored in Japan, where the lowest acidity of ambient precipitation was around pH 4.0 with quite a few frequencies and volume, could not induce any direct and significant effect on the tree species.

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A simple apparatus for measuring the NO₂ absorption rate of trees was developed by measuring the NO₂ concentrations of the air entering and exiting a chamber.
The effects of wind velocity at the inlet and outlet of the chamber on the measured NO₂ values could be eliminated by attaching buffer-tanks. The values obtained with the NO_x sampler method agreed well with those measured by a Zaltzman NO_x analyzer (0.99±0.037).
NO₂ absorption rates of NO₂ absorbent calculated from values measured with the NO_x sampler method were compared with those from analysis of NO₂ absorbent, and the relationship between the two methods was linear (0.98±0.057).
The relationship between NO₂ absorption rates and transpiration rates of small camellia trees was linear (r=0.955).

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The emission rate of nitrous oxide (N₂O) from the night soil treatment plants with the high loading nitrification-denitrification (or high rate aerobic biological treatment) process, which become more common in these years in Japan, was measured at two Facilities. The high concentration, 1400-3300 ppm, of N₂O was observed in the aeration air in the reaction chamber, regardless nitrification or denitrification processl at one Facility, and the conversion rate of N₂O from the nitrogen content of night soil and sludge of septic tank was preliminarily estimated to be about 20% of gaseous components emitted from the chamber. At another Facility, however, the conversion into N₂O was less than 0.3%. These results indicate that the conversion into N₂O can occur at high rate in some types of night soil treatment plant. The detailed analysis of the phenomena can be expected to elucidate the N2O formation mechanisms in nitrification-denitrification process.

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[in Japanese]

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[in Japanese]

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