Nitrogen dioxide areas

Reactions 8 and 9 are important steps for the Hquid-phase nitration of paraffins. The nitric oxide which is produced is oxidized with nitric acid to reform nitrogen dioxide, which continues the reaction. The process is compHcated by the presence of two Hquid phases consequentiy, the nitrogen oxides must transfer from one phase to another. A large interfacial area is needed between the two phases. 

Nitrogen Dioxide (NO2) Is a major pollutant originating from natural and man-made sources. It has been estimated that a total of about 150 million tons of NOx are emitted to the atmosphere each year, of which about 50% results from man-made sources (21). In urban areas, man-made emissions dominate, producing elevated ambient levels. Worldwide, fossil-fuel combustion accounts for about 75% of man-made NOx emissions, which Is divided equally between stationary sources, such as power plants, and mobile sources. These high temperature combustion processes emit the primary pollutant nitric oxide (NO), which Is subsequently transformed to the secondary pollutant NO2 through photochemical oxidation. 

Based solely on this relationship, it has been predicted that the ozone concentration should be about 2 pphm at solar noon in the United States. Indeed [7], in unpolluted environments, ozone concentrations are usually in the range of 2-5 pphm. However, in polluted urban areas, ozone concentrations can be as high as 50 pphm. Peroxy radicals formed from hydrocarbon emissions cause this enhanced ozone concentration. These radicals oxidize nitric oxide to nitrogen dioxide, thereby shifting the above steady-state relationship to higher ozone levels. 

As mentioned in the introduction, the concentration of NO in Japan has remained almost constant for the last 10 years and often exceeds the air quality standard set for nitrogen dioxide (N02), particularly along heavy traffic roads in densely populated areas. To counter this situation, the development of a new technology for removing NO at sub-ppm level from air cf traffic roads, tunnels or other environmental emission sources is essential. 

In spite of the new vehicle emission EUROx regulations, 20% of Europe s urban population is also living in areas where the atmospheric concentrations of nitrogen dioxide (N02) exceed established air quality standards [18]. This is due to several factors related to the diesel-powered cars [19] (1) their increasing market penetration across Europe [20] (2) the NO emission factors of diesel cars exceed the emission levels as established during the type approval of these vehicles in the laboratory [19, 21-25] and (3) the fraction of N02 in the NO emissions of diesel... 

Another area in which free radical reactions may contribute to carcinogenicity is the reactions of nitrogen dioxide (a reactive free radical) with PAH. The striking observation has been made that even PAH that are not themselves carcinogenic may form strongly mutagenic compounds when they react with nitrogen dioxide (35.-3S) ... 

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