Since the beginning of the 1970s when urgent countermeasures against heavy environmental pollution were required, investigation of the lower atmosphere with local air pollution has made a great progress. On the first stage of this period, the photochemical air pollution became the main subject in environmental issues, which had a mesoscale structure unable to understand as pollutant diffusion/ transport from individual pollutant sources, and the role of local meteorological phenomena was focused on. During the same period, mesoscale meteorological models evolved to give realistic simulations of air pollution structure, especially when used with photochemical reaction models. On this background, detailed structures and mechanisms of important meteorological phenomena and coupled air pollutions have been clarified. An outline of the research is described here, with a greater weight on observational aspect. Main topics are land and sea breezes, extended local wind system, urban heat island effect related with locally formed high concentrations of ozone, and cold air lakes and local fronts typically formed on the Kanto plain related with high concentrations of particulate matter.
An attention should be paid to the fact that currently climate change, although it is not always definite whether global or local, is superposed on and interacts with year-to-year changes in local meteorology and air pollution.

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We measured the concentration of CO₂ emitted from the floor of a cool-temperate forest in Higashiyoshino, Nara, Japan, and in the laboratory at various temperatures using field-collected soil. Water, nitrogen, and carbon contents of the soil were determined in the laboratory using field-collected soil. The rate of soil CO₂ efflux in the field was high in summer and low in winter, and the soil CO₂, efflux clearly increased at higher soil temperatures. Using soil collected separately from the A0, A, and B layers, laboratory measurements showed that soil CO₂ efflux was significantly correlated with soil temperature and soil water content. Moreover, the soil CO₂ efflux from the A layer was significantly correlated with soil carbon and nitrogen contents. Based on our analyses, we conclude that air and/or soil temperature is the most influential factor controlling the soil CO₂ efflux in this cool-temperate area.

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In order to obtain information on the dry deposition of ozone in a forest, field experiments were conducted at Kita-Saku in a mountainous area of Nagano prefecture. The vertical distribution and the seasonal variation of ozone concentration in the deciduous forest were measured by coupling Ogawa passive samplers and an UV photometric monitor.
Annual average ozone concentration in the forest was about 39 ppb with maximum in spring and minimum in winter. Diurnal variation was relatively large in the summer and small in the winter. The concentration gradient of ozone in and under the canopy was related with wind velocity and the leaf area index in the forest. The vertical distribution of ozone concentration in the forest showed an “S” shape in the figure: the concentration decreased in the canopy, increased under the canopy, decreased again in the vegetation, and decreased rapidly at the ground surface. As well as the canopy the vegetation and soil surface were effective sinks to remove atmospheric ozone. The balance of the decomposition rate and the supply rate of ozone was considered to be essential to construct the temporal and spatial distribution in the forest.
Observational results by passive samplers would be useful in parameterizing the non-stomatal resistances of certain reactive gasses such as ozone and sulfur dioxide.

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We analyzed meteorological and air-pollution data from two monitoring stations near a busy crossroad in Ikegami-Shinmachi, Kawasaki-shi, Kanagawa, to understand air pollution in the vicinity of the crossroad. We then conducted wind-tunnel experiments using a 1/300-scale model of the area and estimated the annual mean NOx concentration distribution for the area.
Our main findings were:
1) NOx concentrations at Ikegami monitoring station varied greatly in response to both traffic volume and wind direction.
2) NOx concentrations varied with wind speed, but not in a simple inverse relationship.
3) Although observed NOx concentrations were much higher than estimated concentrations, there was a significant correlation between both daily and annual observed and estimated values. We concluded that the distributions of observed and estimated mean NOx concentrations were similar and that the observed concentrations were 3.2 times higher than the estimated concentrations.
4) We adjusted the estimated concentrations to the observed values (by multiplying them by 3.2) and summarized the daily and annual change of NOx concentration distribution in the vicinity of the crossroad.

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To clarify the effects of ambient ozone concentrations on the physiological functions and the growth of beech (Fagus crenata) seedlings, an open-top chamber study was carried out for three growing seasons of 2002-2004 in the Tanzawa Mountains. Two-year-old beech seedlings were exposed to non-filtered air (NF) or charcoal-filtered air (CF) in open-top chambers. The mean concentrations of ozone in the NF and CF treatments were 0.046 and 0.011 ppm, respectively. Chlorophyll content (SPAD value), dark adapted photosystem II quantum yield (Fv/ Fm), growth parameters (height, stem diameter, total dry weight), defoliation and the number of buds were measured. Ozone significantly reduced SPAD value in autumn 2003 and during the growing season of 2004. The Fv/ Fm significantly reduced at the end of the growing season of 2004. Height and stem diameter significantly reduced in 2004, and the total dry weight reduced by 61.3% in the NF treatment compared to that in the CF treatment at the end of the experiment. Early defoliation was observed in the NF treatment. The reduction in the number of buds in the winter of 2004 suggested that the growth of beech seedlings will be reduced greatly in the next year. These results obtained in the present study shows the negative effects of ozone on beech under field conditions in the Tanzawa Mountains.

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To understand the size distribution of ultrafine particles (UFPs) in the vicinity of urban roads, the number concentration distribution of ultrafine particles in the air was observed in different traffic environments. For the observation sites, thirteen sites of the 356 traffic census sites in the Tokyo metropolitan area were selected in terms of “average traffic volume (ATV)”, “average vehicle speed (AVS)” and “heavy duty vehicle mixing ratio (HDR)”. The number concentrations of UFPs involving nanoparticles (NPs) under 50nm diameter increase with the increment in ATV proportionately and especially at high HDR urban roads. A decreasing tendency of the UFPs number concentrations is found in the vicinity of high AVS urban roads because of the diffusion of exhaust emissions from automobiles caused by wind generated by vehicles running. On the other hand, an increasing tendency of UFPs number concentrations is found in the vicinity of high HDR urban roads where exhaust emissions from automobiles is increased under high-speed driving conditions. NPs of 18nm in peak diameter was observed in the vicinity of high HDR urban roads, and the relationship of the 18nm NPs with soot particles around 60-100nm in peak diameter was examined. Various types of the particle size distributions obtained are able to be approximated well by using four Gaussian functions: 18. 2, 34. 1, 65.6 and 132nm in particle center diameter. Also, a high correlation is found between 18.2nm particles and 65. 6nm particles. Alteration processes of UFPs in the air, coagulation, vaporization, condensation and diffusion, are also discussed.

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Mass concentrations and chemical compositions of PM_2.5 were measured continuously for over five years from the year 2000 at Kisai in the North Saitama region. Kisai is located in the outer suburbs of the Tokyo metropolitan area. PM_2.5 was collected weekly a PM_2.5 sampler (R & P, Partisol Plus 2025).
PM_2.5 mass concentrations did not decrease clearly for the five yearperiod. Water soluble inorganic ions and carbons, which are major chemical compositions of suspended fine particles, involved in PM_2.5 were analyzed. The total concentrations of chloride (C1^-), nitrate (NO₃^-), sulfate (SO₄^2-) and ammonium (NH₄⁺) accounted for over 90 percent of all the water soluble inorganic ions. Concentrations of Cl^-, NO₃^- and SO₄^2- changed seasonally. Concentrations of Cl^- and total carbon (TC), especially elemental carbon (Cel), decreased clearly, and those of NO3-decreased gradually. On the other hand, SO₄^2- did not decrease but increased from the year 2003 through the year 2005, except in winter.
TEOM was operating for the same period and mass concentrations were compared with filter collections from the PM_2.5 sampler. Annual mean conentrations of TEOM were the same as those of the filter collections from the PM_2.5 sampler; however, there were discrepancies in the seasonal average concentrations. The measured weight differences of Semi-volatile compositions between TEOM and the collection filter in the+PM_2.5 sampler indicated distinctive trends.

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[in Japanese]

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