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Photochemical smog, often referred to as "summer smog", is the chemical reaction of sunlight, nitrogen oxides and volatile organic compounds in the atmosphere, which leaves airborne particles and ground-level ozone. [21] Photochemical smog depends on primary pollutants as well as the formation of secondary pollutants.
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]
In organic chemistry, peroxyacyl nitrates (also known as Acyl peroxy nitrates, APN or PANs) are powerful respiratory and eye irritants present in photochemical smog. They are nitrates produced in the thermal equilibrium between organic peroxy radicals by the gas -phase oxidation of a variety of volatile organic compounds (VOCs), or by aldehydes ...
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 ...
When NO x and volatile organic compounds (VOCs) react in the presence of sunlight, they form photochemical smog, a significant form of air pollution.The presence of photochemical smog increases during the summer when the incident solar radiation is higher.
Modern smog is usually caused by automotive and industrial emissions, which are acted on in the atmosphere by UV light from the sun to produce secondary pollutants, which then combine with the primary emissions to generate photochemical smog.
New York City's pre-1966 air pollution was reportedly the worst of any American city. [17] Although the "persistently glaring" photochemical smog of Los Angeles was more visible, more "infamous," [18] and subject to a greater degree of public attention, [19] New York City had more total emissions and many more emissions proportional to its land ...
Photolysis occurs in the atmosphere as part of a series of reactions by which primary pollutants such as hydrocarbons and nitrogen oxides react to form secondary pollutants such as peroxyacyl nitrates. See Photochemical smog. The two most important photodissociation reactions in the troposphere are firstly: