A dry Petri dish and Petri dishes filled with water, acidic water and alkaline water, were used for representative surfaces to measure deposition of dry components in environment air. These representative surfaces were established at each center of wide coarse surfaces, to successively carry out an observation on their one-day exposure to environment at a rainproof condition for forty days. Simultaneously, by using collecting filters and low-volume Anderson samplers, ionic component concentration and particle size distribution in gaseous and particulate matters in air were measured. Acidic gases are apt to deposit onto alkaline water, and alkaline ones easily deposit onto acidic one. Namely, by approaching residual resistance of these gaseous materials at the solution surface on their deposition to zero, here were investigated a method to classify suspended particulate matters with gaseous ones. By these tests and from a relationship between difference of deposition flux collected onto every alternative surface and concentration of gaseous and particular materials in air, deposition mechanism and rate of the gaseous and particular materials were individually evaluated.
Deposition velocities in daily measurements of SO₂, NH₃ and NO_x were 0.76, 0.70, and 0.04 cm/sec, respectively. It was thought that it was based on low solubility of NO_x to water and larger residual resistance at the water surface than those of other gaseous materials. The deposition velocities in daily measurements of nss-SO₄^2- and NH₄⁺ of fine particles were 0.24 and 0.33cm/sec, respectively, and NO₃^- presenting both particles of fine and coarse size modes were 0.28cm/sec. The deposition velocities on Na⁺, K⁺, and Mg²⁺ of coarse particles were 1.39, 1.18 and 1.32cm/sec, respectively, and the deposition velocity of Ca²⁺ with larger size among the coarse particles was 2.01 cm/sec. As a result, it could be understood that Ca²⁺ particles had a stronger effect of gravitational sedimentation.
It was rare that after depositing on a dry surface, the particulate matters were re-diffused by wind from the dry surface. NO₃^-, NH₄⁺, and Cl^- were observed to evaporate more than 50%, 40%, and 20% after depositing onto the dry surface, respectively. About 80% of SO₄^2- deposited onto water surface was assumed to be affected by deposition of SO₂. And, deposition of SO₂ onto the dry surface was scarcely found.

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In order to investigate the increasing photochemical oxidants(O_x) in Japan, the occurrence of high O_x events were analyzed, with a focus on its relation with the local climate in the Kanto Plain for the summer months in 1989-1991 and 1999-2001.
During this ten year period, the occurrence frequency of higher ranks of daily maximum O_x concentrations significantly increased, whereas similar frequency shifts were also found in daytime and nighttime averages.
As a result of general grouping of daily weather patterns for the two examined periods, recent increase of days during which the Kanto region experienced high pressure systems was recognized. High pressure systems are associated with clear skies and development of sea breezes, and an increase of the latter was also confirmed by screening simple criteria. An increase in clear sky days could be connected with a rise in air temperature as well as increased ultraviolet radiation, and could be one factor causing increase in high O_x events.
Two groups of days, STL and LTL, were extracted, in which the sea breeze from Tokyo Bay penetrated into a suburban site through the urban areas of Tokyo with a few hours or more, respectively. Recently STL occurred more frequently. On STL days, O_x levels only slightly changed in the urban and suburban areas of Tokyo during the ten years, while they obviously increased in far inland areas. On LTL days, afternoon O_x peaks enhanced sharply in most parts of the examined region.

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We examine the source-receptor relationships for sulfur in East Asia in July and December, 1995, using by a regional chemical transport model (HYPACT) coupled with a Regional Atmospheric Modeling System (RAMS) in order to clarify the fraction contribution of sulfur deposition sources in Japan and their seasonal and spatial variations. The simulation model used in this study is different from the model used in the previous source-receptor analysis in that it uses the high-resolving meteorological/hydrological dataset calculated by the regional meteorological model in the calculation of the vertical diffusion and dry/wet depositions processes in the chemical transport model. We added the simple chemical transformation and wet and dry depositions modules to simulate SO₄^2- and SO₂. The HYPACT can reproduce the day-to-day variations of SO₄^2- concentration and the monthly amount of SO₄^2- wet deposition. Monthly sourcereceptor relationships are estimated for forty-nine regions and volcanoes in East Asia. The model shows that, of the monthly sulfur deposition in Japan in July, 36% comes from volcanoes, 28% from Japan, 18% from China and 12% from North and South Korea. On the other hand, in December, of Japan's deposition, 58% comes from China, 17% from North and South Korea, 13% from Japan, and 8% from volcanoes. This means that in July the contribution of domestic sources including volcanoes is very large and reaches at 64%, while in December, the total contribution of domestic sources including volcanoes decreases to 21% and the contribution of transboundary pollution increases to almost 75%. Thus, the fraction contribution of sulfur deposition sources in Japan exhibits strong seasonal variation and this is caused by the seasonal fluctuations in synoptic wind system.
The sources of Japan's seasonal deposition vary significantly as a function of location within Japan. The deposition along the Pacific coast is 3 times higher for July than for December. In contrast, along the Japan Sea coast, the deposition is only 10% higher for December than for July. Consequently, in the overall Japan, the deposition is almost 20% higher for July, when the domestic sources including volcanoes predominate, than for December, when transboundary pollution predominates. Thus, when viewing the seasonal variations in Japan's deposition, the seasonal variation of influence from domestic sources including volcanoes is more important than that from transboundary pollution.

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Research for utilization of a middle volume dust sampling system was carried out in conformity with International Standards (ISO) regulating suction flow rate in the range from 100 to 200 L/min. Diverse properties were tested and the results are as follows:
1) Although it exceeds the range of measurement of the suction flow rate in the present trial system, the collection efficiency of the QR-100 quartz fiber filter for 0.3μm DOP particles complies with both JIS and ISO standards,
2) Pressure drop for the QR-100 quartz fiber filter used in the present work was approximately 4/5 of the pressure drop of the PTFE coating glass fiber filter (TX). It was confirmed that differences in structure and morphology of the filter material cause this reduction.
3) Using a thimble filter that makes it possible to increase the available filtration area, it was possible to markedly reduce the pressure drop in comparison with a circular filter paper. The prototype sampler is effective for a large suction flow rate of around 150 L/min.
4) Comparison between the middle volume method and the low volume method for an actual chimney indicates that even when there is some deviation in the values, the relationship agrees well with the equation y=1.05x (r²=0.98).
5) Results indicate that suction flow rate of high temperature exhaust gases in an actual chimney is approximately 100 L/min for circular filter paper, whereas it is approximately 170L/min for a thimble filter. The initial objective of a suction flow rate in the range from 100 to 200L/min was achieved.
The above-described results of these tests confirm the practicability of the middle volume dust sampling system prototype.

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[in Japanese]

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