Oxocarboxylic and alpha-omega-Dicarboxylic acids: photooxidation products of biogenic unsaturated fatty acids present in urban aerosols <B>Oxocarboxylic and alpha-omega-Dicarboxylic acids: photooxidation products of biogenic unsaturated fatty acids present in urban aerosols</B><P> Stephanou E.G. and Stratigakis N.<I><P> Department of Chemistry, Division of Environmental Chemistry, University of Crete, 71409 Heraklion, Greece, and Institute of Marine Biology of Crete, 71003 Heraklion, Greece</I><B><P> Abstract</B><I></I><P> omega-Oxocarboxylic and alpha-omega-dicarboxylic acids in the free and salt form have been determined in airborne and near-ground particles in an urban coastal area in the eatsern Mediterranean Sea. They range from C(6) to C(26), with a maximum concentration at C(9) and C(8). The sum of the concentrations of C(8) and C(9), omega-oxo- and alpha-omega-dicarboxylic acids, represents an important proportion (10-36 %) of the acidic fraction of aeolian particulates extracts. The compounds C(6) and C(7) are believed to be photooxidation products of anthropogenic cyclic olefins, while those ranging from C(12) to C(26) 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 simultaneaous 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.<I><P> Environ. Sci. Technol.</I> 1993, 27, 1403-1407<P>