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|In the transport sector as well as in power generation, combustion systems are used nowadays primarily to convert chemical energy locked up in fuels into the useful energy wanted. Since the burning of fossil fuels is one of the major causes of nitrogen oxides, steps to reduce the formation of nitrogen oxides have meanwhile become a permanently established element in the technical development of combustion systems. Investigations into the chemical mechanisms by which they are formed as well as into technical means to achieve their reduction are carried out as current focal points of research.|
A brief introduction to the damaging effects of nitric oxides (also: nitrogen oxides) can be viewed at the German Federal Environment agency, Berlin.
OriginNitrogen oxides include the closely related chemical compounds nitric oxide (NO) and nitrogen dioxide (NO2). NO and NO2 are produced during high-temperature combustion processes from the nitrogen in fuel and atmospheric oxygen. In the process more than 90% is formed as nitric oxide, which is very rapidly oxidised to nitrogen dioxide by atmospheric oxygen. The greatest cause of nitrous gases is motor vehicle traffic. Industrial combustion processes and domestic heating systems further contribute to pollution through nitrous oxides.
Nitrogen dioxide (NO2) is a strong oxidising agent and forms nitric acid (HNO3) when it comes into contact with water.
EffectsNO2 penetrates deep into the respiratory passages when breathed in. Prolonged exposure to NO2 can lead to chronic bronchitis and increased sensitivity to bronchial infections. Increased incidence of respiratory diseases in children is well-documented.
Exposure to nitrogen dioxide can cause damage to plant leaves or needles. By forming nitric acid, NO2 contributes to the acidification of water courses. In habitats with nutrient-poor soils and correspondingly specialised vegetation, the import of nitrogen and accompanying overfertilisation leads to serious alteration in the biological system. Besides this, nitrogen dioxide is one of the basic components for the formation of ozone.
The most effective way of reducing NO and NO2 in the atmosphere is to reduce motor vehicle emissions, for example, by engines with low fuel consumption, using public transport or simply avoiding unnecessary journeys.