Yoshiaki Akutsu

A two-dimensional air quality model in an urban street canyon: evaluation and sensitivity analysis

In order to predict the air quality impact by vehicle emissions within an urban street canyon, a two-dimensional air quality numerical model was developed based on atmospheric convection diffusion equations and a k–e turbulent model. The numerical model has been evaluated using the database from a set of street canyon air tracer experiments carried out near the crossing of Aoyama ichome, Minato-ku, Tokyo in December 1980, by the Japan Environmental Management Association of Industry (JEMAI). Twenty-four cases have been studied for the sensitivity analysis, including more practical cases when the inflow wind has an inclination with the horizontal road and the two buildings have different heights. As a result, it has been shown that the concentration distributions of pollutants emitted from the street are governed by both the inflow wind and the street canyon geometry. A stable vortex was formed within the street canyon, which agrees with other researchers. Pollutant concentrations were predicted to have higher values on the leeward side compared to the windward side. It was concluded that the released pollutants from street canyon become more diluted in the following cases: a lower height of the street canyon, a faster wind speed, a higher height of the leeward building than the windward building and an inflow wind direction towards the street. It is also suggested that the numerical model is useful for predicting the air quality within a typical urban street canyon.

Calculations of heats of formation for nitramines and alkyl nitrates with PM3 and Mm2

Abstract We have calculated heats of formation (Δ Hf°) for nitramines and alkyl nitrates with the semi-empirical molecular orbital theory, PM3 and the molecular mechanics, MM2. Both methods can estimate Δ Hf° accurately. By combining heats of vaporization and sublimation obtained by the additivity rule with Δ Hf° in the gas phase obtained by PM3 and MM2, Δ Hf° in condensed phases can be estimated accurately enough for energy hazards prediction.

EFFECT OF EXHAUST FROM ALCOHOL FUEL ON OZONE FORMATION IN THE ATMOSPHERE

Abstract Alcohols-aldehydes-NO x -air system smog chamber experiments were undertaken and the reaction model was developed based on the experimental results. Ozone formation behaviors of alcohols and aldehydes were investigated with the computer simulation by changing the ratio of reactants. The effect of alcohol fuel on O 3 formation was estimated. Aldehydes have high reactivity in the atmospheric photochemical reaction. Alcohols can promote O 3 formation substantially under reactive conditions. The efficient control of aldehydes emissions is especially important.

Oxidation of cysteamine induced by gas-phase radicals from combustion smoke of poly (methyl methacrylate)

In order to obtain fundamental knowledge on biological damage caused by the smoke from combustion of poly(methyl-methacrylate) (PMMA), we investigated the oxidation of cysteamine induced by PMMA smoke. We suggest that the long-lived and oxygen-centered radicals involved in PMMA smoke should play an important role in the oxidation of cysteamine. The mechanism for the oxidation of cysteamine by combustion smoke of PMMA was postulated as radical initiated chain reactions, taking into account the effect of pH, oxygen and radical concentrations.

Radical Formation from the Reaction of Combustion Smoke with Diphenylamine

We have attempted to examine the effects of radical scavengers, such as amines and phenols, to trap gas-phase radicals produced from the combustion of Poly (methyl methacrylate)(PMMA), which might cause damage to a living body, using an electron spin resonance (ESR) spin-trapping technique. As a result, diphenylamine did not decrease the amount of radicals but rather increased it. It indicates that under the conditions of this study, gas-phase radicals were hardly trapped by radical scavengers and that the precursors to produce other kinds of radicals can exist. It was suggested that from the experiments using several peroxides, the precursors should be diacylperoxides produced from the combustion of PMMA.

Reaction of gas-phase radicals from combustion with radical scavengers

The reaction of apparently long-lived, oxygen-centered gas-phase free radicals, which may cause damage to a living body, from combustion smoke of poly(methyl methacrylate) with typical radical scavengers, diphenylamine and 2,6-di-t-butyl-4-methylphenol has been studied. ESR spectra of the spin adducts of gas-phase radicals were observed in the presence of both radical scavengers. Results show that gas-phase radicals in combustion smoke do not react with these radical scavengers directly, but undergo complicated reactions like induced decomposition. In the case of diphenylamine, it was observed that radical concentrations increased with exposure. It is suggested that this increase may be caused by the reaction of organic peroxides or hydroperoxides in the combustion smoke with diphenylamine.

Influence of cetane improvers on the air quality in an urban street canyon.

The concentration distributions of NOx, PM, HC and CO in an urban street canyon have been estimated using a two-dimensional air quality numerical model based on the k-epsilon turbulent model and the atmospheric convection diffusion equation when various cetane improvers were used in diesel fuels. A wind vortex can be found within the street canyon, and the pollutants emitted from the bottom of the street canyon tend to follow the course of the wind field, moving circularly. The addition of cetane improvers can improve the air quality in a street canyon, all of the pollutants were found to decrease with increasing centane number.

Consensus building in safety and security: a case study of Fukushima evacuees returning home

This study examines consensus building in environmental and energy policies by analyzing the minutes of the safety and security committee of the Nuclear Regulation Authority (NRA) of the Japanese government, in the context of the discussion of the safe return of Fukushima evacuees after the 2011 Great East Japan Earthquake and Tsunami and the subsequent Fukushima nuclear disaster. One important issue associated with evacuation policies was the high number of evacuees, if not all, who were not willing to return to their old homes. Although the contents of governmental committee meetings are freely accessible through the internet, they have been rarely analyzed for these purposes. In this study, we used text-mining techniques to analyze NRA committee minutes quantitatively and qualitatively. We have three primary findings. First, the committee attempted to take evacuees’ feelings into account and pragmatically discuss what was needed to restore their lives and livelihoods, as well as to make its meetings transparent and open to the public by, for example, streaming them live on the internet. Second, in earlier committee meetings, government representatives insisted on specific policies made by themselves to control the return of evacuees. However, outside experts at the meetings convinced representatives that decisions regarding issues surrounding the safe return of evacuees should consider the opinions of the evacuees themselves. Third, the NRA reported the outcome of the meetings at a Cabinet meeting to accelerate policies requiring urgent implementation as well as those related to the alleviation of people’s anxieties regarding exposure to radioactivity or those related to equal treatment among those who wanted to voluntarily move away from the affected areas versus those who want to return to their homes. Finally, this analysis further identified a number of issues concerning citizen participation and governance associated with environment and energy policies, all of which need to be overcome in order to establish consensus among concerned stakeholders.