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Nitrogen oxide can refer to a binary compound of oxygen and nitrogen, or a mixture of such compounds:

In atmospheric chemistry, air pollution, and related fields, nitrogen oxides refers specifically to NOx (NO and NO2).[1][2]

Only the first three of these compounds can be isolated at room temperature. N2O3, N2O4, and N2O5 all decompose rapidly at room temperature. NO3, N4O, and N(NO2)3 are very reactive.

N2O is stable and rather unreactive at room temperature, while NO and NO2 are quite reactive but nevertheless quite stable when isolated.


Main article: NOx

NOx (often written NOx) refers to NO and NO2. They are produced during combustion, especially at high temperature. These two chemicals are important trace species in Earth's atmosphere. In the troposphere, during daylight, NO reacts with partly oxidised organic species (or the peroxy radical) to form NO2, which is then photolysed by sunlight to reform NO:

NO + CH3O2 → NO2 + CH3O
NO2 + sunlight → NO + O

The oxygen atom formed in the second reaction then goes on to form ozone; this series of reactions is the main source of tropospheric ozone. CH3O2 is just one example of many partly oxidised organic molecules that can react with NO to form NO2.

These reactions are rather fast so NO and NO2 cycle, but the sum of their concentration ([NO] + [NO2]) tends to remain fairly constant. Because of this cycling, it is convenient to think of the two chemicals as a group; hence the term NOx.

In addition to acting as a main precursor for tropospheric ozone, NOx is also harmful to human health in its own right.

NOx may react with water to make nitric acid, which may end up in the soil, where it makes nitrate, which is of use to growing plants.


Oxidized (cationic) and reduced (anionic) derivatives of many of these oxides exist: nitrite (NO
), nitrate (NO
), nitronium (NO+
), and nitrosonium (NO+
). NO2 is intermediate between nitrite and nitronium:

+ e → NO2
NO2 + eNO

See also[edit]


  1. ^ United States Clean Air Act, 42 U.S.C. § 7602
  2. ^ Seinfeld, John H.; Pandis, Spyros N. (1997), Atmospheric Chemistry and Physics: From Air Pollution to Climate Change, Wiley-Interscience, ISBN 0-471-17816-0 

Original courtesy of Wikipedia: http://en.wikipedia.org/wiki/Nitrogen_oxide — Please support Wikipedia.
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397 news items

Tue, 02 Sep 2014 03:18:45 -0700

The US Environmental Protection Agency and US Coast Guard will enforce the regulations in US waters. The aim is to improve air quality and public health through stricter controls on emissions of sulfur oxide, nitrogen oxide and particulate matter ...
Bloomberg BNA
Tue, 02 Sep 2014 09:07:30 -0700

The complaint, which says the project's state-issued minor source permit allows nitrogen oxide emissions equivalent to every Illinois resident driving a 2013 Jeep Patriot 12,000 miles annually, seeks to require the project to obtain a prevention of ...
Albuquerque Journal
Mon, 01 Sep 2014 23:00:00 -0700

Consumers may soon face higher electric rates as Public Service Company of New Mexico seeks to recover costs for investment in power plants and other infrastructure, and to make up for a drop in power consumption brought about by a combination of a ...
Your Houston News (blog)
Sun, 31 Aug 2014 22:03:45 -0700

The U.S. Energy Information Administration estimates that natural gas emits only half as much carbon dioxide and one-third the amount of nitrogen oxide as coal. Vehicles powered by natural gas produce 30 percent less greenhouse gas emissions than those ...
PR Newswire (press release)
Tue, 02 Sep 2014 05:00:00 -0700

Duke Energy since 2005 has reduced company-wide carbon dioxide emissions by 20 percent, sulfur dioxide emissions by 84 percent and nitrogen oxide emissions by 63 percent by building natural gas-fired power plants, closing coal-fired power plants and ...

The San Luis Obispo Tribune

The San Luis Obispo Tribune
Tue, 19 Aug 2014 20:05:31 -0700

The land equipment used instead has emitted more nitrogen oxide, said Katie Huff, spokesman for the U.S. Army Corps of Engineers. The corps is working with the U.S. Department of the Interior and the Bureau of Reclamation on the project. Nitrogen oxide ...
Climate Central
Sun, 31 Aug 2014 05:33:45 -0700

Carbon reduction policies like cap and trade reduce all those other forms of pollution, too (including particulate matter, sulfur dioxide, and nitrogen oxide, which leads to lung-burning ground-level ozone). In other words, clean air is a positive side ...
Oil & Gas Journal (subscription)
Mon, 01 Sep 2014 02:33:45 -0700

The programs urge vessel operators to slow down to 12 knots or less within a certain range of the ports to reduce emissions of carbon dioxide (CO2), nitrogen oxide (NOx), and sulfur oxide (SOx) in coastal areas to conserve coastal environment, and ...

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