Current models for estimating the amount of NO_x emissions use a variable of the average speed of a vehicle for a specific length of time or have variables of a vehicle's speed and acceleration at just times. The former does not describe the difference in the amount of emissions between open road driving, congested driving, or stop and go driving. On the other hand, the latter makes it difficult to aggregate the amount of emissions for a specific length of road.
This research shows that it is possible to create a model to solve these existing issues with current emission models by proposing models with more intermediate details. In this model, the trip segment is defined as the period between a vehicle's starts points: from when it begins moving for the first time to when it begins moving for the second time and it is used to estimate the amount of NO_x emissions. In the estimation, nine variables, travel time of the four trip modes (acceleration, cruising, deceleration, idling), average acceleration in acceleration mode, and average speed of the four trip modes are used to make the estimates. The accuracy of this method is high (the coefficient of determination is over 0.85).

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The CMAQ (Community Multi-scale Air Quality) model based on the RAMS (Regional Atmospheric Modeling System) for the Asian Domain was developed and the detailed descriptions of the model system and the available options are described. Emission inventory based on Streets et al., (2003a, b) and the volcanic gas emissions from Miyakejima-Oyama is used in this system. The developed RAMS/CMAQ system was used in the Asian scale gas/aerosol transport simulation during March and April 2001 with an 80 km horizontal resolution. RAMS precipitation intensity and distribution, and the CMAQ output (SO₂, O₃, SO₄, EC and OC) are compared with observation data from the Japan Meteorological Agency, EANET and VMAP (Matsumoto et al., 2003), and we confirmed that both the precipitation and concentration fields represent the majorobserved distribution well. Sensitivity analysis of the effects of volcanic gas emissions from Miyakejima-Oyama revealed that its effects are important for air quality over the central and northern Japan areas.

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A monitoring tape for hydrogen cyanide gas in air has been developed by using Cu (II) and N, N-diethyl-pphenylenediamine (DPD) sulfate. It is based on color change of the tape when reacting with hydrogen cyanide. The tape, which contains silicagel as an absorbent and is impregnated with a processing solution that includes copper (II) acetate, DPD sulfate and glycerin, was found to be a highly sensitive means of detecting hydrogen cyanide gas. When an air sample including hydrogen cyanide gas was passed through the tape, hydrogen cyanide was absorbed on the surface of the tape. The cyanide ion reacted with the copper (I) ion producing Cu CN, then the DPD was oxidized by the copper (II) ion to form a stain. The intensity of the stain was proportional to the concentration of hydrogen cyanide at a constant sampling time (70s) and the flow rate (400ml/min). The intensity of the stain could be recorded by measuring the intensity of reflecting light (555nm). The detection limit was 0.20ppm for HCN. No response was observed from various other gases, with an exception of oxidizing gases (ex Cl₂). However, the influence of oxidizing gases in the sample gas was completely eliminated by passing the sample gas through an elimination column packed with DPD.

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In recent years, some thermal power plants have adopted plans to limit the height of stacks for scenic considerations, cost reduction and compliance with aviation regulations. In these cases, it is important to consider the high concentration of air pollutants caused by downdrafts due to mountains located windward of stacks in the environmental impact assessment. Recently, the method of evaluating the topographical effect by means of an air flow model and a dispersion model (TOPADS) has been proposed by the authors. The validity of this method has been confirmed experimentally using wind tunnel and field tracer experiments for large-capacity elevated sources; however, the applicability of the method for evaluating atmospheric dispersion during downdraft conditions has not yet been tested. Furthermore, there has been no study on a numerical model for atmospheric dispersion, which considers downdrafts.
In this study, we examined the applicability of the atmospheric dispersion estimation method for downdrafts on the basis of meteorological observations and field tracer experiments. Turbulence and dispersion characteristics during a downdraft were studied at the base of Mt. Akagi. The TOPADS method tends to slightly overestimate the effect of topography and it is difficult to set inflow boundary conditions for turbulence statistics at a mountain area located windward of a source in the air flow model. A method of calculating dispersion, in which turbulence statistics are parameterized using the results obtained by meteorological observations (DownDraft Model: DDM), was proposed. The DDM enabled the reduction of the overestimation tendency found in certain simulation cases utilizing the TOPADS and provided reasonable estimates of atmospheric dispersion for downdraft periods. The DDM requires neither the setting of inflow boundary conditions for turbulence statistics nor calculation using an air flow model. The DDM is therefore easier to use than the TOPADS method.

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[in Japanese]

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