Kiera Jefferson
Peroxyacetyl nitrate (PAN) is a hazardous secondary pollutant and a nitrogen reservoir in the troposphere. It is a component of photochemical smog and is produced in the atmosphere when oxidized volatile organic compounds (VOCs) combine with nitrogen dioxide. PAN is formed through the reaction of nitrogen dioxide with peroxyacetyl radical, the oxidized product of VOCs. It is a powerful respiratory and eye irritant, causing eye irritation at concentrations of only a few parts per billion. PAN is more toxic than ozone and can cause extensive damage to vegetation. It is of particular concern when it remains suspended in the atmosphere for extended periods, allowing it to be transported by wind currents and spread its impact to other regions.
| Characteristics | Values |
|---|---|
| Type of pollutant | Secondary pollutant |
| Alternative names | Peroxyacetyl nitrate (PAN), Acyl peroxy nitrates (APN) |
| Chemical composition | CH3C(O)OONO2 |
| Prevalence | 75-90% of total atmospheric emissions |
| Toxicity | Higher than ozone, similar to NO2, higher than SO2 |
| Health effects | Reduced respiratory function, eye irritation, severe lung lesions, damage to the epithelium of upper parts of the respiratory tract |
| Environmental effects | Damage to vegetation, injury to plants, increased susceptibility to disease in plants, death of plants |
| Sources | Motor vehicles, tobacco smoke, burning of fossil fuels, vehicle exhaust, industrial emissions, solvent usage |
| Formation | Reaction of nitrogen dioxide (NO2) with peroxyacetyl (PA) radical, which is the oxidated product of volatile organic compounds (VOCs) |
| Decomposition products | Carbon monoxide (CO), carbon dioxide (CO2) |
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What You'll Learn
- Peroxyacetyl nitrate (PAN) is a hazardous secondary pollutant
- PAN is a component of photochemical smog
- PAN is produced by the action of sunlight on volatile organic compounds (VOCs) and nitrogen oxides
- PAN is a powerful respiratory and eye irritant
- PAN is formed from other pollutants by chemical reactions in the atmosphere
Peroxyacetyl nitrate (PAN) is a hazardous secondary pollutant
PAN is a powerful respiratory and eye irritant, causing eye irritation at concentrations of only a few parts per billion. It is more toxic and water-soluble than ozone. At higher concentrations, it causes extensive damage to vegetation. PAN is also associated with reduced lung function in humans, including emphysema and impaired breathing.
The net formation of PAN usually occurs in polluted areas, from where it can be transported by wind currents to relatively clean areas. In these new areas, PAN decomposes into PA and NO2, promoting ozone (O3) formation. The decomposition of PAN can also produce carbon monoxide and carbon dioxide.
Studies have shown that PAN levels are higher in the cold season, particularly in coastal areas. This is due to the increased presence of C7–C9 aromatics and C4–C5 alkenes, largely from vehicle exhaust and solvent usage. PAN is a concern for human health and the environment, and further research is needed to understand its spatiotemporal distribution, chemical sources, and control strategies.
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PAN is a component of photochemical smog
Peroxyacetyl nitrate (PAN) is a secondary pollutant and a component of photochemical smog. It is formed through the reaction of nitrogen dioxide (NO2) with peroxyacetyl (PA) radicals, which are oxidised volatile organic compounds (VOCs). PA radicals are only generated through the oxidation of certain OVOCs, such as acetaldehyde and methylglyoxal.
PAN is a powerful respiratory and eye irritant, causing more eye irritation from photochemical smog than ozone. It is more toxic than ozone and has been linked to severe lung lesions and damage to the epithelium of the upper respiratory tract in animals. PAN is also detrimental to plant growth, causing changes in colour and growth, increased susceptibility to disease, and even death.
PAN is produced in the atmosphere when oxidised VOCs combine with nitrogen dioxide. Sources of the pollutants required to create PANs include motor vehicles, tobacco smoke, and the burning of fossil fuels. PAN is of particular concern when it remains suspended in the atmosphere for extended periods, as it can be transported large distances by wind currents, spreading its impact to other regions.
The formation of PAN is influenced by various factors, including the presence of specific VOCs and nitrogen dioxide, sunlight, and regional transport. Studies have shown higher PAN levels in the cold season, particularly in coastal areas, and net photochemical PAN formation in the warm season. The feasibility of joint control of PAN and ozone has been confirmed through isopleth diagrams.
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PAN is produced by the action of sunlight on volatile organic compounds (VOCs) and nitrogen oxides
Peroxyacetyl nitrate (PAN) is a secondary pollutant that is formed by the action of sunlight on volatile organic compounds (VOCs) and nitrogen oxides. PAN is a powerful respiratory and eye irritant present in photochemical smog. It is a key indicator of photochemical pollution and is generated through reactions involving specific volatile organic compounds (VOCs) and nitrogen oxides. PAN is formed by the oxidation of non-methane volatile organic compounds (NMVOCs) in the presence of NOx.
The most common peroxyacyl radical, PAN can be formed from the free radical oxidation of acetaldehyde, various ketones, or the photolysis of dicarbonyl compounds. Acetaldehyde, acetone, and methylglyoxal are all directly emitted and produced in the atmosphere from the oxidation of primarily emitted NMVOCs. PAN is the principal tropospheric reservoir species for nitrogen oxide radicals (NOx = NO + NO2) and has important implications for the production of tropospheric ozone (O3) and the hydroxyl radical OH, the main atmospheric oxidant.
The formation of PAN is closely linked to that of O3, as both are initiated by the reaction of hydrocarbons with the hydroxyl radical (OH) in the presence of nitrogen oxides. However, PAN is formed specifically from VOCs that are precursors to the acetyl radical (CH3CO), while O3 can be produced from the oxidation of any VOCs. PAN is a good marker for the source of VOCs as either biogenic or anthropogenic, which is useful in the study of global and local pollution effects.
The production of PAN is influenced by various factors, including the presence of haze, with stronger photochemical production occurring under hazy conditions. Additionally, the daily variation pattern of O3 is similar to that of PAN, with peaks occurring at different times depending on the level of haze. PAN has been observed at unexpectedly high concentrations during the summertime, with average daily values showing a strong correlation with black carbon (BC) and O3, further highlighting the connection between summertime haze and photochemical pollution.
Furthermore, PAN is synthesized in the gas phase via photolysis of acetone and NO2 using a mercury lamp, resulting in the creation of methyl nitrate (CH3ONO2) as a byproduct. Overall, PAN plays a significant role in atmospheric chemistry and has important implications for global atmospheric oxidant distributions and nitrogen deposition.
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PAN is a powerful respiratory and eye irritant
Peroxyacetyl nitrate (PAN) is a powerful respiratory and eye irritant. It is a secondary pollutant, formed through the reaction of nitrogen dioxide (NO2) with peroxyacetyl (PA) radical, the oxidated product of volatile organic compounds (VOCs). Sources of the pollutants required to create PANs include motor vehicles, tobacco smoke, and the burning of fossil fuels.
PAN is a component of photochemical smog, which is produced in the atmosphere when oxidized VOCs combine with nitrogen dioxide. It is a good marker for the source of VOCs as either biogenic or anthropogenic, which is useful in studying the global and local effects of pollutants. PAN can be produced in a lipophilic solvent from peroxyacetic acid. For the synthesis, concentrated sulfuric acid is added to degassed n-tridecane and peroxyacetic acid in an ice bath.
PAN is toxic and irritating as it dissolves more readily in water than ozone. It is a lachrymator, causing eye irritation at concentrations of only a few parts per billion. PAN has been shown to have similar effects to VOCs, and long-term contact with it can result in oxidative damage or peroxidation of biomolecules. The acute toxicity of PAN is less than that of ozone but higher than SO2. Following acute exposure, severe lung lesions and, at higher levels, damage to the epithelium of the upper parts of the respiratory tract were found in animals.
The net formation of PAN usually occurs in polluted areas, from where it can be transported by wind currents to relatively clean areas. PAN that remains suspended in the air for extended periods can contribute to air pollution in distant places. Decomposition of PAN produces a variety of chemicals, including carbon monoxide and carbon dioxide.
In summary, PAN is a powerful respiratory and eye irritant that is formed from other pollutants through chemical reactions in the atmosphere. It has toxic effects on both human health and plant growth.
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PAN is formed from other pollutants by chemical reactions in the atmosphere
Peroxyacetyl nitrate (PAN) is a highly reactive compound that is a major component of photochemical smog. It is formed from other pollutants by chemical reactions in the atmosphere. PAN is not directly emitted into the atmosphere but is instead a secondary pollutant.
PAN is formed by the reaction of hydrocarbons and nitrogen oxides under the presence of light. This reaction is catalysed by ultraviolet light from the sun, which oxidises unburned non-methane hydrocarbons to aldehydes, ketones, and dicarbonyls. The most common peroxyacyl radical is peroxyacetyl, which can be formed from the free radical oxidation of acetaldehyde, various ketones, or the photolysis of dicarbonyl compounds. PAN can also be formed in the gas phase via photolysis of acetone and NO2 with a mercury lamp.
The composition of PANs in a particular region depends on which hydrocarbons are present in the atmosphere. However, peroxyacetyl nitrate is an exception, as it can be produced from a range of precursors. PANs are toxic and irritating, as they dissolve more readily in water than ozone. They are lachrymators, causing eye irritation at very low concentrations. At higher concentrations, they can cause extensive damage to vegetation and crops, leading to reduced yields and damage to the ecosystem.
PANs are good markers for the source of VOCs as either biogenic or anthropogenic, which is useful in the study of global and local pollution effects. They are produced in the thermal equilibrium between organic peroxy radicals by the gas-phase oxidation of volatile organic compounds (VOCs), or by aldehydes and other oxygenated VOCs oxidising in the presence of NO2. One of the significant sources of VOCs and NOx that contribute to the formation of PAN is automobile exhaust. Industrial processes, such as oil and gas production, chemical manufacturing, and printing, also emit large amounts of VOCs and NOx.
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Frequently asked questions
Peroxyacetal nitrates, also known as peroxyacyl nitrates, Acyl peroxy nitrates, or PANs, are a component of photochemical smog. They are formed through the reaction of nitrogen dioxide (NO2) with peroxyacetyl (PA) radical, the oxidated product of volatile organic compounds (VOCs).
Yes, peroxyacetal nitrates are a secondary pollutant. They are not directly emitted as exhaust from power plants or internal combustion engines, but they are formed from other pollutants by chemical reactions in the atmosphere.
Peroxyacetal nitrates are toxic and irritating to humans and plants. They are powerful respiratory and eye irritants, and can cause reduced respiratory function and eye irritation. They can also cause extensive damage to vegetation.
