Perfluorooctane sulfonate (PFOS: C_8F_<17>SO_3^-) and perfluorooctanoic acid (PFOA: C_7F_<15>COO^-) are wildely used in a variety of applications, including polymer additives, lubricants, fire retardants and suppressants, pesticides and surfactants. Furthermore, these compounds are metabolically and photochemically inert, resisting both biotic and abiotic degradation. As a consequence, they have been detected in wildlife, such as fish, birds, and mammals, from urban and remote areas around the world. Recent studies have characterized trace levels of the compounds in the serum of non-occupationally exposed human. In this study, we investigated the decomposition of PFOS and PFOA in aqueous solutions by sonochemical action based on the rates, products and possible mechanisms of the sonochemical degradations. We proposed the possible mechanisms on the basis of the ions detected by ESI/MS and ion chromatography. The formation of PFOA during the PFOS degradation may be due to oxidation followed by dissociation of the SO_3^- group, and the dissociated SO_3^- group will be oxidized to SO_4^<2-> by sonication. The generated PFOA would undergo shortening of the perfluoro-carbon chain caused by the repetition of the COOH dissociation and the oxidation of the generated ions or radicals of the perfluoro-carbon. The formation of CF_3(CF_2)_6SO_3^- and CF_3(CF_2)_5SO_3^- from PFOS would be due to the reaction at the CF_3 group in PFOS. However, there are no examples for the sonochemical reaction of the trifluoromethyl group, and the detailed mechanism is not clear at this stage.
