In order to establish methodologies for dry deposition monitoring in East Asia, studies on dry deposition direct measurement and parametarization of depositionsion velocity were carried out. As preliminary analyses, sulfur dry deposition in Japan and East Asia were estimated by using the parametarizations developed in North Amerika and Europe. Direct measurement studies were done in a red pine forest (Nagano, Japan) and a teak forest (Lampang, Thailand) to evaluate aplicability of the parametarizations. In the Nagano field, the Bowen ratio method was used to measure SO₂ dry deposition. Measured deposition velocity was 0.9 cm/s during the time, from 12:00 to 14:00, in autumn. In the Thai field, the aerodynamic gradient method was used to measure O₃ and SO₂ dry deposition. Higher deposition velocities of O₃ and SO₂ in the wet season were mainly caused by non-stomatal uptake of wet canopy due to a lot of wet days, especially in the case of SO₂. Much higher daytime deposition velocities in the wet season were additionally caused by stomatal uptake of leafy trees. In dry season, the O₃ surface resistance was found to be affected by aerodynamic process rather than stomatal process. Finally recent field studies on dry deposition in East Asia (from 2002 to 2007) were reviewed and then a parameterization of deposition velocity was updated based on the findings of the review.

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Ozone is the photochemical oxidant that causes serious leaf injury. Ethylene and salicylic acid are known to act as signaling molecules that enhance and induce cell death in ozone-exposed plants. However, a few studies also report about the protective effects of ethylene and salicylic acid against ozone-induced injury. In this study, we investigated the protective effects using Arabidopsis mutants lacking either ethylene signaling (ein2) or salicylic acid biosynthesis (sid2). However, ozone-induced leaf in ein2 and sid2 mutants was unclear and unstable, we generated double mutants by crossing ozone-sensitive ascorbate deficient mutant (vtc1) and ein2 or sid2 mutant. Expression of ethylene and salicylic acid biosynthesis or inducible genes was highly induced with ozone in vtc1 as compared to that in wild type. The vtc1 mutant also showed high levels of ethylene evolution and salicylic acid accumulation by ozone, suggesting that the vtc1 mutant is suitable as a parental line to generate double mutants. Although vtc1 mutant was more sensitive to ozone than wild type, double mutants lacking ascorbate biosynthesis and phytohormone signaling showed higher level of leaf injury than vtc1. Thus far, our results indicate that these plant hormones have a role in protection of plants from ozone-induced leaf injury.

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Air quality has been traditionally evaluated using chemical and physical methodologies. Bioassay, which detects biohazardous property of environmental contaminants on site, is still being an unexplored field of air quality monitoring. Authors aimed to develop a simple testing system of toxicity of the airborne particulate matter by using bioluminescent bacterium Vibrio fischeri. Atmospheric aerosol samples were collected on a quartz fiber filter at a flow rate of 23.5L/min by low volume air sampler for 7-day duration, at the terrace of school building of Tokai University, Japan. Classified aerosol samples were also collected by Andersen sampler for 1-month duration. Collected materials were then extracted with deionized distilled water by mild shaking. After filtration with 0.45 micro-meter pore size filter, the extracts were subsequently mixed with a bacterium solution in a well of 24-well plate and the time course of bioluminescence intensity were measured by a luminometer. In this study, the Rapid On-site Toxicity Audit System (Leachable), supplied by Hitachi Chemicals, was applied to this bioassay system. As a result, the bioluminescence intensity was influenced by the water extracts of atmospheric aerosol components. Linear relationship was found between inhibition (%) per sampling volume and atmospheric aerosol concentration, when the bioluminescence was significantly reduced. This means atmospheric aerosol contains biohazardous materials which contribute to the aerosol concentrations. Meanwhile, the relatively higher inhibition was found in the fine particles (<2.1 μm). This suggests possible application of this bioassay system to biomonitoring of PM2.5. The extracts seemed a colloidal solution with slight black particles. Then, the extracts were re-filtered by a centrifugation filter unit and the residual particles were observed by TEM. The TEM image showed the residue was aggregated soot carbon, which might be a possible cause of reducing the bioluminescence of marine bacterium. On the other hand, even when TSP concentration were high, there were some cases the inhibition was not found. Typical cases were found in period of low traffic density and yellow sand storm. This suggests aerosols which contains rich minerals may become nutrient to the marine bacterium.

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Measurements of total OH reactivity employed by the laser-induced pump and probe technique and the concentrations of trace of species in atmosphere were carried out to diagnose the air quality in urban area of Tokyo in summer season. Difference between the measured OH reactivity and the calculated one confirmed the existence of unknown species reacted with OH radicals. As for the difference between the measured OH reactivity and the calculated one, there is no apparent correlation of the difference and any concentration of trace of species in atmosphere. Oxidant potentials, the index of the efficiency of the oxidant production, were calculated for the urban area and compared to that for the suburban area.

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A monitoring network of atmospheric ²²²Rn concentration as a tracer for long-range transport in East Asia was established. Atmospheric ²²²Rn concentration at Beijing, which is located on China Continent was 10- 20Bq m^-3, at Nagoya, which is located on edge of terrestrial area was 3- 10 Bq m^-3 and at Hachijo-jima and Hateruma-jima, which are solitary islands in Pacific Ocean was 0.5- 3 Bq m^-3, respectively. The atmospheric ²²²Rn concentration variations were different from sites. The ²²²Rn concentration was the lowest in the summer and the highest in the winter except Nagoya where the highest was observed in the autumn and the lowest in the spring. Diurnal variations were measured at Beijing and Nagoya. In contrast, diurnal variations were not measured but several-day-cycle variations were measured at Hachijo-jima and Hateruma-jima.
It was pointed out by this study that the several-day-cycle variations at Hachijo-jima were dependent on synoptic-scale atmospheric disturbance. ²²²Rn concentration increased rapidly after a cold front passed through Hachijo-jima. Backward trajectory analysis of the relationship between atmospheric ²²²Rn concentrations at Hachijo-jima and transport pathway of air mass indicates that air mass transported from China and Siberia has high concentration ²²²Rn and air mass transported from Pacific Ocean has low concentration ²²²Rn. In winter, atmospheric ²²²Rn concentrations at Hachijo-jima is dependent on vertical transport pathway rather than horizontal transport pathway.

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We have carried out continuous measurements of PM_2.5 semi-volatile compounds, which have been measured individually in the past time, in order to analyze seasonal factors affecting mass concentrations of them in a central Tokyo. PM_2.5, nitrate, sulfate, EC and OC were also measured. Concentrations of PM_2.5 volatile compounds during winter showed the highest of those during four seasons. Daily variation of the volatile concentrations was common to four seasons. There was an obvious peak at around noon and around 2:00 a.m. as well as nitrate, sulfate, OC and EC. After studying effects of composition, meteorological factors and traffic volume by multivariate analyses, it implies a single factor did not strongly influence on PM_2.5 volatile compounds but multi-factors did comprehensively with multi-regression analyses. The most contributed variable was nitrate in all seasons. The next contributed variables were different according to the season, and it was revealed that they were absolute humidity during winter, temperature during autumn and summer, and time during spring and summer.

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To understand the recent increase in the concentrations of photochemical oxidant (O_x), we analyzed the concentrations of O_x and its precursor substances measured at Tajima monitoring station (MS) near seaside industrial area in Kawasaki city, from 1985 to 2005. In results, it was found that the annual mean concentrations of O_x were increasing and those of nitric oxide (NO) were decreasing, and in August the relation between monthly mean concentrations of O_x and those of NO was characteristic of trade-off. Also, it was found that daily maximum concentrations of O_x were high in the day of low concentrations of NO at 5:00 before dawn and in the day of high concentrations of non-methane hydrocarbon (NMHC), in August, 1985, 1995 and 2005. These results showed that, at Tajima MS in August, daily maximum concentrations of O_x were under the influence of both NO's effect of restraining O_x concentrations and NMHC's effect of increasing O_x concentrations, and also inferred that the decrease of NO concentrations was one of the possible factors causing the increase of O_x concentrations at Tajima MS in August.

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