Oxocarboxylic and .alpha.,.omega.-dicarboxylic acids: photooxidation products of biogenic unsaturated fatty acids present in urban aerosols

Abstract

Oxocarboxylic and , -dicarboxylic acids in the free and salt form have been determined in airborne and nearground particles in an urban coastal area in the eastern Mediterranean Sea. They range from Ce to C26, with a maximum concentration at C9 and Ce. The sum of the concentrations of Ce and C9, --and , -dicarboxylic acids, represents an important proportion (10-36%) of the acidic fraction of aeolian particulates extracts. The compounds Ce and C•? are believed to be photooxidation products of anthropogenic cyclic olefins, while those ranging from C12 to C26 are considered likely to be of biogenic origin. The 1,8-octanedioic and 1,9-nonanedioic acids are proposed to be oxidation products unsaturated fatty acids. The simultaneous presence of the corresponding 8-oxooctanoic and 9-oxononanoic acids as well as of the 9,10-epoxyoctadecanoic acid of 1-nonanal and of nonanoic acid, when correlated to the very low concentration (or even absence) of unsaturated fatty acids, represents additional evidence for the above hypothesis. A mechanism of this atmospheric photooxidation reaction is proposed.

Hydroxyl radical-induced photochemical formation of dicarboxylic acids from unsaturated fatty acid (oleic acid) in aqueous solution

“…In addition to DCAs (C 2di -C 9di ), many other intermediates and photochemically stable compounds are likely produced from the OH-induced degradation of oleic acid in aqueous solution. For atmospheric aerosols, some authors reported the photoproduction of C 9 , ωC 9 , C 9di and C 9ald , as well as nitrated carboxylic acids from the reaction of oleic acid with OH, O 3 or NO 3 [12,13,14,15,16]. In this study, C 9 and C 9ald could not be determined using our GC/FID technique.…”

“…The reaction of oleic acid (cis-9-octadecenoic, 9C 18 ) with O 3 , OH and NO 3 has recently emerged as a model system to better understand the photooxidation processes affecting unsaturated fatty acids in atmospheric aerosols [11,12]. Oleic acid is degraded through an oxidative cleavage of its double bond to produce C 9 compounds, i.e., nonanoic (C 9 ), 9-oxononanoic (ωC 9 ) azelaic (C 9di ) acids and 1-nonanal (C 9ald ) [13,14,15,16] as well as nitrated carboxylic acids [12]. Secondary photooxidation reactions could initiate the production of lower molecular weight DCAs such as C 2di -C 8di [9,17,18].…”

Diurnal and temporal variations of water-soluble dicarboxylic acids and related compounds in aerosols from the northern vicinity of Beijing: Implication for photochemical aging during atmospheric transport

“…We also found greater levels of azelaic (C 9 ) acid (28 ng m -3 ) at night than mid-day (24 ng m -3 ). C 9 is a specific oxidation product of unsaturated fatty acids (Kawamura and Gagosian, 1987;Stephanou and Stratigakis, 1993;Yokouchi and Ambe, 1986).…”

“…C 6 diacid is formed by the ozone oxidation of cyclohexene (Grosjean et al, 1978;Hatakeyama et al, 1987). On the other hand, C 9 is produced by the oxidation of biogenic unsaturated fatty acids (Kawamura and Gagosian, 1987;Stephanou and Stratigakis, 1993). Thus C 6 /C 9 ratio has been utilized as a tracer to estimate the anthropogenic v.s.…”

Dicarboxylic acids, ketocarboxylic acids and dicarbonyls in the urban roadside area of Hong Kong

“…Other than primary vehicular emissions and secondary sources, biogenic contributions of dicarboxylic acids are common, especially in rural areas. As azelaic acid (C 9 ) has been proposed as one of the reaction products by ozonolysis of biogenic unsaturated fatty acids (Kawamura and Kaplan, 1983;Yokouchi and Ambe, 1986;Kawamura and Gagosian, 1987;Stephanou and Stratigakis, 1993) and adipic acid (C 6 ) has been proposed as one of the products by oxidation of anthropogenic cyclohexene (Grosjean et al, 1978;Hatakeyama et al, 1987;Kawamura and Ikushima, 1993), the C 6 /C 9 ratio can be used as a potential indicator to show the strength of biogenic sources.…”