What is Nitrogen Dioxide ?
Nitrogen oxides are formed during high temperature combustion processes from the oxidation of nitrogen in the air or fuel. The principal source of nitrogen oxides (NOx) is road traffic, which is responsible for approximately half the emissions in Europe. Nitric oxide (NO) and nitrogen dioxide (NO2) concentrations are therefore greatest in urban areas where traffic is heaviest. Different vehicles give off different amounts of nitrogen oxides. Larger and older vehicles, particularly diesel, produce more nitrogen oxides than new vehicles. New vehicles are ‘cleaner’ because of new technology, such as catalytic converters Nitrogen oxides are released into the atmosphere mainly in the form of nitric oxide, which is then readily oxidised to nitrogen dioxide by reaction with ozone (O3). Elevated levels of nitrogen oxides occur in urban environments under stable meteorological conditions, where the air mass is unable to disperse. Nitrogen Dioxide is measured in microgrammes per cubic metre (m g
