OXOCARBOXYLIC AND ALPHA,OMEGA-DICARBOXYLIC ACIDS - PHOTOOXIDATION PRODUCTS OF BIOGENIC UNSATURATED FATTY-ACIDS PRESENT IN URBAN AEROSOLS

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 eastern Mediterranean Sea. They range from C6 to C26, with a maximum concentration at C-9 and C-8. The sum o f the concentrations of C-8 and C-9, omega-oxo- and alpha,omega-dicarb oxylic acids, represents an important proportion (10-36%) of the acidi c fraction of aeolian particulates extracts. The compounds C6 and C-7 are believed to be photooxidation products of anthropogenic cyclic ole fins, while those ranging from C-12 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 simult aneous presence of the corresponding 8-oxooctanoic and 9-oxononanoic a cids 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 f or the above hypothesis. A mechanism of this atmospheric photooxidatio n reaction is proposed.