Studies from Germany on the measurement of PM_2.5 in urban air demonstrated that approximately 10% of fine particles are PM_0.1. Experimental studies on hamsters reveled that inhaled ultrafine particles of metal fumes can penetrate Type I alvaolar epithelia and are deposited in the interstitium and lymphatic system or blood vessele of the lung. Quantitative animal studies show that ultrafine particles are more easily incorporated in the lung interstitium and hilar lymph nodes than fine particles. Ultrafine particles deposited in human lungs have been shown to contain several kinds of metals by analytical eletron microscopy, and SPMs from various souces can produce oxidants resulting in harmful effects to the lungs, depending on the metal species. Other reports, however, indicate toxic effects of ultrafine particles contained in Teflon fumes, a synthetic resin, which is ordinarily inert with human tissue. When ultrafine particles aggregate and become large conglomerates, toxic effects promptly disappear indicating that an important toxicity charac. teristic exists in ultrafine size particles, but not in the chemical composition, as in the case of Teflon particles. If PM_2.5 is related to deaths from cardiopulmonary diseases as shown by epidemiological studies, ultrafine particles readily absorbed by the blood may explain one of the mechanisms of PM_2.5 toxicity.

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In this study, dry-type reduction of mercury (II) chloride experiments were conducted using a packed bed with granular tin metal. The purpose of this study was to identify factors effecting the dry-type reduction process and to elucidate the reaction mechanism. In the reduction of mercury (II) chloride, the ratio of chlorinated surface area on tin was a vital factor. Precoating the surface of granular tin metal with 1N hydrochloric acid was effective in maintaining the reducibility. Marcury (II) chloride was reduced to mercury (0) vapor by the following two reactions on the chlorinated surface of tin metal.
SnCl₂ (s) + HgCl₂ (g)→SnCl₄ (g) + Hg (g)
SnCl₂ (s) + HgCl₂ (g) + 2H₂0 (g)→SnO₂ (s) + Hg (g) + 4HCl (g)
Also, it is presumed that decreased reducibility was the result of the following oxidative reactions with tin (II) chloride.
SnCl₂ (s) + H₂O (g)→SnO (s) + 2HCl (g)
SnCl₂ (s) + H₂O (g) + 1/2O₂ (g)→SnO (s) + 2HCl (g)

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We conducted a tunnel study to obtain the current relative composition of vehicle-emitted compounds, mainly volatile organic compounds (VOCs), in Japan, to compare it with those reported in other tunnel and roadside studies or chassis-dynamometer studies, and to estimate emission factors.
The analytes were total non-methane hydrocarbons (NMHC), formaldehyde, 1, 3-butadiene, benzene, toluene, styrene, ethylbenzene, m-/p-xylene, o-xylene, 1, 3, 5-trimethylbenzene, 1, 2, 4-trimethylbenzene, carbon monoxide and nitrogen oxides (NO_x). These were measured in 2-hour periods over 24 hours in and outside an urban road tunnel. The traffic composition was observed to vary little over the 24-hour period. Gasoline-fueled vehicles were considered to be the majority.
We estimated the relative error for excess concentrations of compounds in the tunnel (T_ex: the difference between tunnel-air and background-air concentrations). To yield relatively reliable Tex compositions, the 5 measurement periods with the smallest relative errors were selected for further discussion.
Based on volumetric carbon concentrations, among the measured VOCs, toluene contributed most (16%) to the NMHC. The 9 measured VOCs (other than formaldehyde) comprised 40% of the NMHC. The average composition of benzene-mormalized volumetric concentrations generally agreed with those obtained in overseas tunnel and roadside studies. The composition of NO_x-normalized mass concentrations was compared with the results from a chassis-dynamometer study conducted in Japan. The composition was closer to that of a gasoline-fueled vehicle than that of a diesel-engine vehicle, which was consistent with the traffic composition. In addition, we attempted to estimate emission factors for the tunnel traffic as a whole based on reported emission factors.

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Industries and high population densities develop in costal areas, SLB (sea and land breezes), which act as a kind of local circulation. As a result, air pollution is a serious problem in coast areas. In order to understand overall flow fields of SLB accompanying sea breeze fronts, the flow in a water tank apparatus was visualized with styrofoam particles as tracers, and video images were taken. We calculated wind velocity vectors from the movement of tracer patterns between the visualized image, and were able to detect overall flow fields of SLB. We also carried out numerical calculations using a non-hydrostatic model, in which a two-dimensional laminar layer and Boussinesq approximation was assumed. The followipg phenomena were observed in the water tank experiment:(1) the vertical mixingflow was shown to be Benard type convection, and sea breezes crossed on to land from the coastline when the land temperature rose;(2) weak land breezes blew when land temperatures decreased. These characteristics observed in the water tank experiment were reproduced by numerical calculation. Using the universal function for SLB proposed by Ueda, a maximum wind speed of 1mm/s obtained in the water tank experiment was equivalent to 4.8m/s in field observations, and a mixing layer height of 10mm obtained in the water tank experiment was equivalent to 560m in field observations. From these results, we postulate that the water tank experiment can simulate actual SLB.
Next, we investigated the influence on mass diffusion of the flow fields using both non-hydrostatic and hydrostatic models. The non-hydrostatic model was able to reproduce Benard type convection, sea breeze front, and the strong perturbation of vertical flow that were observed in the water tank experiment. Temperature fall occurring at the time of the sea breeze front passage was also reproduced. But the hydrostatic model was not able to reproduce these characteristics of SLB. However there was no significant difference between the maximum mass concentration calculated by the mass diffusion simulation using either flow field. But the time to maximum concentration was delayed as the point was kept away from the point source, when the hydrostatic flow field model was used.

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As a countermeasure for air pollution due to hazardous chemical compounds, the monitoring scheme to estimate annual average concentrations was ruled as sampling daily average values once in every month. Accuracy of annual average from such kind of scheme has surely been analyzed repeatedly, but has not necessarily been reported for open discussion.
Here, the characteristics of annual average estimated from periodic intermittent sampling are analyzed with using selected NO₂ (and NO_x) data from Tokyo and Aichi Prefectures, Japan. From full one-year data, thirty different annual averages can be obtained from intermittent sampling with 30 days period. Their standard deviation is at most 12% of complete annual average in case of NO₂ in Tokyo, although the magnitude of deviation systematically depends on locations and areas. Such a diversity appears to correspond to the difference in occurrence frequency distribution of concentration at each point. Similarly, it is suggested that the difference in the frequency distribution among pollutants results in different accuracy of annual average from intermittent sampling.

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Introduction of Microsoft Excel macros for environmental data analysis that one (SH) of the present authors has uploaded to a web site (http://www.jomon.ne.jp/hayakari/). AndersenAnalyzer is an add-in for the Excel that enables us to make graphs of measurement data of Andersen-sampler by utilizing a spline function. It can display cumulative concentrations up to PM-10, PM-2. 5 and PM-1.0 as well as the ratios to a total suspended matter concentration. It also makes it possible to print a set of many graphs in a matrix fashion, up to 4 columns and 8 rows, into an A4 paper.

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