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News Consultations Publications About us Jobs. Show submenu for "". Nitrogen dioxide How nitrogen dioxide gets in the air and its effects on health. Last updated: 29 September Air Pollution. Chemical formula and description. Effects on health. Groups most sensitive to nitrogen dioxide. Standards and guideline values to protect health.
Nitrogen dioxide concentration in unpolluted air is around 10 parts per billion ppb. In smog, the concentration rises twenty-fold to about ppb. Although nitrogen oxides have gained dubious distinction as pollutants, they are also used beneficially in some industrial processes. Nitric oxide is manufactured on a large scale, and is subsequently used to make nitric acid HNO 3. To create nitric oxide for industrial uses, chemists combine ammonia NH 3 with oxygen O 2 , releasing water H 2 O as a byproduct.
Nitrogen compounds derived from nitric acid are used to create chemical fertilizers, explosives, and other useful substances. Skip to main content. Basic Information about NO2. NO 2 and other NO x interact with water, oxygen and other chemicals in the atmosphere to form acid rain.
Acid rain harms sensitive ecosystems such as lakes and forests. The nitrate particles that result from NO x make the air hazy and difficult to see though. This affects the many national parks that we visit for the view. EPA identifies areas where the air quality does not meet the national NO 2 standards. In rural air, away from sources of NO, most of the nitrogen oxides in the atmosphere are in the form of NO 2. Therefore, during the day NO, NO 2 and ozone exist in a quasi-equilibrium which depends on the amount of sunlight.
Eventually, NO 2 is oxidised to nitric acid HNO 3 , vapour which is absorbed directly at the ground, is converted into nitrate-containing particles, or dissolves in cloud droplets. At night, different oxidation processes convert NO 2 to nitrates.
Although nitric acid is rapidly absorbed on contact with surfaces cloud droplets, soil or vegetation , the other nitrogen oxides are removed only rather slowly, and may travel many hundreds of km before their eventual conversion to nitric acid or nitrates. Consequently, emissions in one country will be deposited in others.
Measured NO 2 concentrations show the predominance of traffic and urban sources, with the largest concentrations in the large conurbations and adjacent to the motorway network, with annual mean concentrations in excess of 10 ppb in these areas.
It is likely that the strongest effect of emissions of nitrogen oxides across the UK is through their contribution to total nitrogen deposition.
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