In recent years there has been an increasing recognition of the research needs for the performance evaluation of air quality simulation models AQSMs (diffusion models) in United States. Accordingly, in order to meet these needs a large number of studies were carried out: American Meteorological Society AMS workshop, US EPA's model evaluation program and Electric Power Research Institute EPRI plume model validation and development PMV & D project and so on.
Since a diffusion model for a large elevated point source in rural area was considered to be completed until early 1970's in some sectors of Japan, any improvement for these models of Japan in 1980's cannot be seen. However, more comprehensive and large scale projects in U.S. point out some contradictions in these models.
This review paper shows the recent progress of the development of the rural diffusion models and performance evaluation of a diffusion model for regulatory use.

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From spring to autumn each year in large areas of the Tokyo suburbs, spinach plants (Spinacia oleracea L.) are visibly damaged by atmospheric oxidants. Symptoms of this leaf injury are flecking on the upper surface of mature and lower leaves caused by ozone, or silver ing on the lower surface of mature leaves caused by peroxyacetylnitrate, or both.
Field susceptibilities to oxidants differed markedly among the 15 cultivars of spinach. Growth and bolting were more rapid in oxidant-sensitive than in resistant cultivars.
Spinach plant sensitivity to oxidants was generally low in the early stages of growth, increased toward harvest time, then gradually decreased toward senescence. Low-temperature treatment (4°C 14 days) at the sowing stage and gibberellin treatment at the growth stage of spinach plants accelerated aging and increased sensitivity to ozone.
Spinach leaf levels of total sulfhydryl groups, protein, and chlorophyll were higher in the early than in the late stages; this finding suggests that total sulfhydryl groups in spinach leaves are involved in the mechanism of protection against ozone toxicity.

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Oxidant resistant cultivars of spinach (Spinacia oleracea L.), a major crop in the Tokyo suburbs, were selected and their morphological, physiological, and genetic characteristics were studied in order to reduce oxidant damage to this plant.
The relationship between oxidant resistance in spinach plants and the morphological characteristics, levels of several chemical substances, enzyme activities, and inheritance of these characteristics in spinach leaves was studied in 12 spinach cultivars. Cultivars with leaves that were abundantly notched, or thin, or rich in de-hydroascorbic acid were sensitive to oxidants. Cultivars with leaves that were less abundantly notched, or thick, or round, and leaves with high superoxide dismutase activity were resistant to oxidants.
A sensitive cultivar, Ujo, was reciprocally crossed with a resistant cultivar, Viroflay. The maternal influence was evident, as the oxidant resistance of the first filial generation was midway between that of the parents, and leaf levels of chlorophyll and total sulfhydryl groups also showed inheritance of maternal traits. Ozone resistance in spinach therefore appears to be linked to the chloroplasts, whose role in cytoplasmic inheritance is known.

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A simple analytical method for azaheterocyclic compounds has been developed by using capillary column gas chromatography. One hundred and two azaheterocyclic compounds were separated by two types of capillary columns, 5% PMS and Carbowax 20M columns.
A flame thermionic detector was used for sensitive and selective detection of the compounds. Detection limits for most of the compounds were in the range 1-100μg. Good reproducibilities in retention time and peak height were achieved by the automatic sample injection. The use of an internal standard (2-nitrodiphenyl) further improved the reproducibilities. That is, coefficient of variations of relative retention ratio and relative peak height were 0. 01-0.2% and 2-4%, respectively.
The proposed method was applied to the analysis of azaheterocyclic compounds in basic fraction of an airborne particulate extract. Thirteen azaheterocyclic compounds including some carcinogenic/mutagenic compounds were determined by the combination use of proposed method and GC/MS. Concentrations of the compounds were ranging from 50 pg/m³ to 2 ng/m³ in the atmospheric environment.

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Airborne particulate matter was collected at 4 types of sampling site; industrial, residential, seashore and suburban areas, and Te and Se concentrations in the samples were analyzed by graphite furnace atomic absorption spectrometry. Higher concentrations of Te and Se were observed when wind directions were from industrial and particular emission sources. At Hiyoshi, near Keihin industrial zone, rather low concentrations of Te were observed in winter season predominated by northern wind, while those of Se did not show clear variation on yearly basis. Te and Se were found about 78% and 71%, respectively, in fine particles smaller than 2μm in aerodynamic diameter in size fractionated sampling.

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The concentrations of airborne asbestos in environments at an urban commercial area were measured utilizing phase contrast microscopy (PCM) and transmission electron microscopy (TEM) equiped with EDX.
Results of the concentrations of asbestos fibers by PCM and TEM were compared. The concentrations of asbestos fibers by TEM were the average 5.15 (171) and showed a highly seasonal variance.
The relationship between the concentrations of asbestos fibers by PCM and those by TEM were not found to be correlated, but the relationship between the concentrations of asbestos fibers by PCM and those of both asbestos and nonasbestos mineral fibers with length of 5μm or more than were found to be significantly correlated.
The chrysotile fibers and tremolite fibers for the types of asbestos fibers observed were constituted each average about 50%. The results suggest that the source of tremolite fibers might be caused by concomitant mineral fi bers in talc dusts from rubber industrial plants adjacent to this area.
The aspect ratio (width to length) of asbestos fibers with length of 5μm less than and those with length of 5μm or more than was 20:1, 27:1, respectively. In frequency distribution of asbestos fibers with length of 5μm less than, 38.5% of those was smaller particles that had length of 1μm less than with width of 0.4μm less than.
The mass concentrations of asbestos fibers was a highly variable because each of asbestos fibers showed the changes in the types and the shapes.
The concentrations of all mineral fibers as asbestos and nonasbestos fibers was about 120 times greater than the concentrations of asbestos fibers and also 97% of all mineral fibers was smaller particles that had length of 5μm less than. The frequency distribution of all mineral fibers was highly in the particles that were shorter in length and finer in width.

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An application of ion chromatography (IC method) to the determination of concentration of ammonia (NH₃) and ammonium salts (NH₄⁺) in the atmosphere using filter and Sep-pak C18 cartridge impregnated with mixed solution of 5% phosphoric acid (H₃PO₄) and 5% glycerin was examined.
It was found that the collection efficiency of NH₃ in the atmosphere was good by the use of impregnated cartridge at flow rate of 1-10l/min. And concerning to the aspect of determination of concentration of ammonium ion with IC method, this method was superior in respect of simplicity, rapidity and detection limit to the conventional method such as indophenol method. However, there are a few defect as follows: the calibration curve was non-lineality when the concentration of ammonium ion in the solution was over 1 pg/ml. Also the concentration of H3PO4 of sample solution should be treated to below 0.1%, as the H₃PO₄ used to collect NH₃ interfered with the determination of ammonium ion.
The method established in this study was applied to the analysis of NH₃ and NH₄⁺ collected in Nara City in a period from May, 1987 to Apr., 1988. The annual mean concentration of NH₃ and NH₄⁺turned out to be as follow: 11.17 ppb for NH₃ and 2.03μg/m³ for NH₄⁺. The concentration of NH3 was high in summer season and low in w inter season, while the concentration of NH4+ was a little variation through a year. And the concentration of NH3 exhibited about 1.5 to 8 times to the concentration of NH₄⁺ and the NH₃/NH₄⁺ ratios were recognized dependency on the temperature.

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International comparison of carcinogenic/mutagenic compounds in air will provide useful information for the study on the effect of air pollution to health such as lung cancer. The present authors have carried out comparative study on air pollution by polycyclic aromatic hydrocarbons (PAH) among Bangkok, Chiang Mai and Tokyo.
Airborne particulate samples were collected at the following sampling places: 1) 7 air pollution monitoring stations in Bangkok (from Nov., 1985 to Jan., 1986), 2) 8 places in Chiang Mai (from Feb., to Sep., 1986), 3) National Institute of Public Health in Tokyo (from Nov., 1985 to Sep., 1986). Each sampling was done for 24 hrs/sampling-day by using high-volume air samplers. PAHs in particulate samples were extracted by benzene: ethanol=-3: 1 (v/v) with ultrasonic agitation. Extracted solutions were cleaned up by liq.-liq. partition with 5% NaOH aqueous solution and PAH in them were determined by a reversed-phase HPLC/fluorometry.
The geometric average of total aerosol concentrations in Bangkok was 1. 5 times higher than that in Tokyo. However, the average concentrations of pyrene and chrysene in the air were 5. 2 and 9. 4 times higher in Tokyo, respectively. Average concentrations of BaP, BkF and BeP were slightly (1. 2-1. 3 times) higher in Tokyo. In case of BghiP, average concentration in Bangkok was 1. 4 times higher than that in Tokyo. Similar phenomena were observed in the comparison of average data between Chiang Mai and Tokyo. Average concentrations of pyrene and chrysene were 2, 3 times higher in Tokyo, while those of BkF and BeP were only 1. 1-4. 2 times higher in Tokyo. In case BaP and BghiP, average concentrations were 1.2 times higher in Chiang Mai. These phenomena may mainly due to the difference in atmospheric temperature and UV irradiation. Monthly average temperature in Bangkok and Chiang Mai were ranging 25.5-26.7 (ay. 26.1°C) and 23.1-29.0°C (av. 26.7°C), respectively (from 1951 to 1960), which were well higher than that in Tokyo (4.7-26.5°C, ay. 15.3°C from 1951 to 1980). It was also suggested that PAHs tend to be higher during the dry season in Thailand.

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A highly sensitive ultramicro forward-mutation assay using Salmonella typhimurium TM677 was achieved by the introduction of micro-vessel in the preincubation step. This assay was about 10 times higher in sensitivity than the micro forward-mutation assay and was able to measure mutagenicity of extracts from airborne particulates obtained by only 3m³ air sampling. Repeatability of this assay was nearly same with that of the micro forward-mutation assay, that is, the coefficient of variation of the mutation frequency for airborne particulate extracts was 12.3% in the test condition without S9 mix and 13.7% with S9 mix. This assay was applied to the measurement of hourly variation mutagenic activity of airborne particulates indoors and outdoors, and revealed that mutagenic activity of indoor air was generally higher than that of outdoor air and that the mutagenic activity indoors in the absence of S9 mix was well correlated with human activity.
It was also found by this assay and PAH analysis that indoor pollution by carcinogens and mutagens was largely affected by cigarette smoking and an air cleaner was useful for the reduction of indoor pollution by mutagens and PAHs.

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