They are good markers for the source of VOCs as either biogenic or anthropogenic, which is useful in the study of global and local effects of pollutants.[4][5]
PANs are secondary pollutants, which means they are not directly emitted as exhaust frompower plants orinternal combustion engines, but they are formed from other pollutants by chemical reactions in the atmosphere.Free radical reactions catalyzed byultraviolet light from the sun oxidize unburned non-methane[6]hydrocarbons toaldehydes,ketones, anddicarbonyls, whose secondary reactions create peroxyacyl radicals. The most common peroxyacyl radical is peroxyacetyl, which can be formed from the free radical oxidation ofacetaldehyde, various ketones, or thephotolysis of dicarbonyl compounds such asmethylglyoxal ordiacetyl.
The stability of PANs in the atmosphere is dependent on temperature. The lower temperatures in the troposphere increase the stability and therefore lifetime of PANs.[7] Since they dissociate quite slowly in the atmosphere intoradicals and NO2, PANs are able to transport these unstable compounds far away from their urban and industrial origins. This causes a decrease in photochemical ozone production near sources ofNOx as PANs are aNOx reservoir, reducing the amount ofNOx photolyzed.[8] This allows PANs to transport NOx to regions where it can more efficiently producetropospheric ozone.
Peroxyacetyl nitrate is the first member of PANs identified by scientists in the 1950s and the most prevalent peroxyacyl nitrate (75–90% of total atmospheric emissions),[6][9] followed by peroxypropionyl nitrate (PPN),[10] the second member of PANs discovered from synthetic mixtures.[9] The third member of the PANs class is peroxybutyryl nitrate (PBN), which is only been known to be synthetically made.[9] Peroxybenzoyl nitrate (PBzN)[10] andmethacryloyl peroxynitrate (MPAN)[4] have also been observed. The composition of PANs in a particular region depends heavily on which hydrocarbons are present in the atmosphere, with the exception of peroxyacetyl nitrate, which is able to be produced from a range of precursors.[4]: 7624
PANs are both toxic and irritating, as they dissolve more readily in water thanozone. They arelachrymators, causing eye irritation at concentrations of only a few parts per billion. At higher concentrations they cause extensive damage to vegetation.[11]
^Jickells, T.; Baker, A.R.; Cape, J.N.; Cornell, S.E.; Nemitz, E. (2013). "The cycling of organic nitrogen through the atmosphere".Philosophical Transactions of the Royal Society B: Biological Sciences.368 (1621).doi:10.1098/rstb.2013.0115.
^Jenkin, Michael E.; Clemitshaw, Kevin C. (2000). "Ozone and other secondary photochemical pollutants: chemical processes governing their formation in the planetary boundary layer".Atmospheric Environment.34 (16):2499–2527.Bibcode:2000AtmEn..34.2499J.doi:10.1016/S1352-2310(99)00478-1.
^abcStephens, E.R.; Burleson, F.R.; Cardiff, E.A. (1965). "The Production of Pure Peroxyacyl Nitrates".Journal of the Air Pollution Control Association.15 (3):87–89.doi:10.1080/00022470.1965.10468346.PMID14257516.
^abKleindienst, Tadeusz E.; Shepson, Paul B.; Smith, David F.; Hudgens, Edward E.; Nero, Chris M.; Cupitt, Larry T.; Bufalini, Joseph J.; Claxton, Larry D.; Nestman, F.R. (January 1990). "Comparison of mutagenic activities of several peroxyacyl nitrates".Environmental and Molecular Mutagenesis.16 (2):70–80.Bibcode:1990EnvMM..16...70K.doi:10.1002/em.2850160204.PMID2209566.
^Mudd, J.B.; Kozlowski, T.T. (1975).Responses of Plants to Air Pollution. 111 Fifth Avenue, New York, New York 10003: Academic Press, INC. pp. 97–116.ISBN0-12-509450-7.{{cite book}}: CS1 maint: location (link)
