Atmospheric particulate matter (PM) and its chemical components were monitored at the rooftop of a building in the central Tokyo metropolitan area from FY 1994 to FY 2004. Size-separated PM samples were collected as PM_21-7, (2.1-7μm) and PM2.1 (<2.1μm). The PM₇ (<7μm) concentration was constant at about 50μgm^-3 in the late 1990s, but showed a decreasing trend fmm 2000 onward. The ratio of PM₂₁ to PM₇ decreased simultareously with PM₂₁ concentration. Carbonaceous components that were determined by a thermal method were conected by linear regression equation of those values against results determined by a thermal/optical method. Elemental carbon (EC) was the main component of PM; 90% of it was present in PM₂₁ over the whole study period. The concentration of EC in 2004 was 56% of that in 1994. The ratio of EC₂₁ to PM₂₁ showed a decreasing trend fmm 1998 onwani that coincided with the introduction of long-term regulation of diesel vehicles. SO₄^2-, NO₃^-, and Cl^- concentrations showed seasonal variation. NO₃^- and Cl^- were negatively correlated with ambient temperature. It was difficult to evaluate the both ionic components of collected sample on the filtec because the both ionic components were lost fmm the sample by volatilization. Thus, we have re-evaluated the animal trend using the data observed during cold periods (<16°C). Yearly average Cl^- concentration in cold periods showed a decreasing trend. This trend was probably the result of a reduction in Cl^- emissions in response to the regulation of incineration furnaces as part of dioxin-control measures. We concluded that the decreasing trend in the levels of these various emissions in the Tokyo metropolitan area was the result of the enforcement of emission regulations.

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As part of the study on indoor air quality of large-scale buildings, we investigated the condition of air pollution in an art museum and a museum and the personal exposure level of employees. The chemicals studied were volatile organicompounds (VOCs), nitrogen dioxide and aldehydes. Various physical parameters were also measured. We found that indoor air quality in art museum and museum is maintained at good levels. This might be because of the Japanese strict regulations that require administrators of large-scale buildings to provide adequate ventilation and perform regular measurement of indoor air quality.

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Based on the findings of recent field studies (Matsuda et al, 2007), a parameterization of deposition velocity for sulfur and nitrogen compounds was updated. Regarding the modification of parameterization, the enhancement of uptake by wet canopies for sulfur dioxide and ammonia; the deposition to forest, which has very rough surface, for aerosol components were taken into account Since the modification brings relatively low surface resistance (R_c) therefore high dependence of deposition velocity on aerodynamic resistance (R_a), R_a parameterization was elaborated. The parameterization of friction velocity that is the most important element of Ra well reproduced the friction velocities observed by an ultrasonic anemometer in deferent atmospheric stabilities. In order to evaluate the parameterization updated, deposition velocity to forest and grass was estimated at Rishiri, Sado-seki, Yusuhara and Hedo EANET monitoring sites in the period from April 2004 to Mamh 2005. As a result, the enhancement of uptake by wet canopies was reproduced by the parameterization. Moreover aerosol deposition velocities to forest were relatively close to the measurement values of literatures, compared with the values estimated from a previous parameterization. Comparisons among sites and among seasonal variations indicated that HNO₃, SO₂, NH₃ strongly depend on R_a+R_b, both R_a+R_b and R_c, R_c, respectively.

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In order to promote strategies for reducing the fine particulate matters (PM₁₀/PM₂₅) in the atmosphere in Japan, it is essential to assess the emission characteristics of PM₁₀/PM_2.5 at various stationary souroes, and it is also necessary to develop accurate measurement methods for PM₁₀/PM₂₅ emissions, and to prepare an early standardization of these methods. In this paper, the impaction method designated for low concentration measurement according to ISO 23210, which is still in the draft stage, is described, and several issues related to the measurement of PM₁₀/PM_2.5, as well as their countermeasures are investigated experimentally using test particles.
The main conclusions obtained from a set of experiments and considerations are as follows;
(1) Though a straight nozzle is a prerequisite for the two-stage impactor in ISO 23210, it is difficult to insert the impactor with the straight nozzle into a small measuring hole, and therefore a two-stage impactor with a 90° bend nozzle was adopted in the study. In the case of a flow velocity of 11.5m/s in the test duct, and a dust concentration of about 22mg/m³_N, the amount of particulates adhered inside the 90° bend nozzle with an internal diameter of 6mm was approximately 30%. In the case these adhered particulates are neglected, the measured dust concentration decreases considerably, while it has almost no effect on the results of the particle size distribution (average diameters and the distribution curves). On the other hand, the PM₁₀/PM_2.5 measured concentrations are approximately 20-23% lower than those obtained from straight nozzle measurements.
(2) When it is necessary to correct the results for adhered particulates, the particulates may be collected after dismounting and weighed with the whole nozzle, and the measurements of the particle size distribution are corrected. Thus, it is possible to compensate the measured values for dust concentration, particle size distribution and PM₁₀/PM_2.5 due to the wall loss. In the case of such dry particles or particulates with low adhesive properties as used in this experiment particulates are easily and effectively collected using the pulse air purge onto particulates adhered inside the 90° bend nozzle.
(3) In general, an increase in the separation stages decreases re-entraining of particulates in the impaction method, as the collected particles are further divided at each stage. In this experiment, a large amount of particulates entrains from the PM_10-2.5 collector in the two-stage impactor of the ISO method. Howevei re-entraining of particulates was noticeably suppressed in the three-stage impactor, in which the PM_10-5.0 collector was added. A filter paper made of quartz fiber is most suitable for the collection plate because of its rough surface, and it could be also used for high temperature gas measurements and chemical analyses.
(4) Since the particle weight limit for the collection plate depends on physical characteristics of PM_10-2.5 (especially, size distribution width, number concentration and adhesive property) and property of the flue gas, it is difficult to establish a certain limit value as used in the ISO method. Therefore, it is required to establish strategies for suppression of particle re-entraining through an increase in the number of separation stages.

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