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Nitrogen dioxide tropospheric column density in 2011. Nitrogen dioxide typically arises via the oxidation of nitric oxide by oxygen in air (e.g. as result of corona discharge): [15] 2 NO + O 2 → 2 NO 2. NO 2 is introduced into the environment by natural causes, including entry from the stratosphere, bacterial respiration, volcanos, and lightning.
In atmospheric chemistry, NO x is shorthand for nitric oxide (NO) and nitrogen dioxide (NO 2), the nitrogen oxides that are most relevant for air pollution. [1] [2] These gases contribute to the formation of smog and acid rain, as well as affecting tropospheric ozone.
There are many different sources of air pollution. Some air pollutants (such as nitrogen oxides) originate mainly from human activities, [15] while some (notably radon gas) come mostly from natural sources. [16] However, many air pollutants (including dust and sulfur dioxide) come from a mixture of natural and human sources. [17]
By mole fraction (i.e., by quantity of molecules), dry air contains 78.08% nitrogen, 20.95% oxygen, 0.93% argon, 0.04% carbon dioxide, and small amounts of other trace gases (see Composition below for more detail). Air also contains a variable amount of water vapor, on average around 1% at sea level, and 0.4% over the entire atmosphere.
The largest part of most combustion gas is nitrogen (N 2), water vapor (H 2 O) (except with pure-carbon fuels), and carbon dioxide (CO 2) (except for fuels without carbon); these are not toxic or noxious (although water vapor and carbon dioxide are greenhouse gases that contribute to climate change).
The nitrogen oxides are derived from the nitrogen in the ambient air, as well as from any nitrogen-containing compounds in the fossil fuel. The sulfur dioxide is derived from any sulfur-containing compounds in the fuels. The particulate matter is composed of very small particles of solid materials and very small liquid droplets which give flue ...
Trace gases are gases that are present in small amounts within an environment such as a planet's atmosphere.Trace gases in Earth's atmosphere are gases other than nitrogen (78.1%), oxygen (20.9%), and argon (0.934%) which, in combination, make up 99.934% of its atmosphere (not including water vapor).
The same reaction is carried out by lightning, providing a natural source for converting atmospheric nitrogen to soluble nitrates. [12] + The hot nitric oxide is cooled and combines with atmospheric oxygen to produce nitrogen dioxide. The time this process takes depends on the concentration of NO in the air.