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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.
Nitrogen oxide may refer to a binary compound of oxygen and nitrogen, or a mixture of such compounds: Charge-neutral. Nitric oxide (NO), nitrogen(II) oxide, or ...
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]
Nitric oxide (nitrogen oxide or nitrogen monoxide [1]) is a colorless gas with the formula NO. It is one of the principal oxides of nitrogen . Nitric oxide is a free radical : it has an unpaired electron , which is sometimes denoted by a dot in its chemical formula ( • N=O or • NO).
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.
Photochemical smog depends on primary pollutants as well as the formation of secondary pollutants. These primary pollutants include nitrogen oxides, particularly nitric oxide (NO) and nitrogen dioxide (NO 2), and volatile organic compounds. The relevant secondary pollutants include peroxylacyl nitrates (PAN), tropospheric ozone, and aldehydes.
Ground-level ozone is both naturally occurring and anthropogenically formed. It is the primary constituent of urban smog, forming naturally as a secondary pollutant through photochemical reactions involving nitrogen oxides and volatile organic compounds in the presence of bright sunshine with high temperatures. [35]
It is a secondary pollutant present in photochemical smog. [1] It is thermally unstable and decomposes into peroxyethanoyl radicals and nitrogen dioxide gas. [2] It is a lachrymatory substance, meaning that it irritates the lungs and eyes. [3] Peroxyacetyl nitrate, or PAN, is an oxidant that is more stable than ozone. Hence, it is more capable ...