R5 AM Perflourochemical Biodegradation, Fate, and Transport
Thursday, 17 November 2005: 8:00 AM - 11:40 AM in 321-323

(HIG-1117-751419) Sorption of Perfluorinated Surfactants onto Sediments.

Higgins, C¹, Luthy, R¹, ¹ Department of Civil & Environmental Engineering, Stanford University, Stanford, CA, USA

ABSTRACT- While perfluorochemicals (PFCs) have been detected in many different environmental media such as air, water, sediment, and biota, data on the partitioning of PFCs between these compartments are scarce. In particular, sorption of PFC surfactants onto sediments has been suspected and measured for a few PFCs such as perfluoroctanesulfonate (PFOS), but it remains unclear whether the organic-carbon partitioning paradigm for hydrophobic organic contaminants is applicable to these chemicals. PFC surfactant sorption may be influenced by other sediment geochemical parameters such as iron and aluminum oxide content, as has been shown for linear alkylbenzene sulfonate (LAS) surfactants. In addition, given the varying chain lengths of PFC surfactants used in the past and currently in use, an understanding of how sorption varies with perfluorocarbon chain length is warranted. To this end, batch sorption isotherm experiments were conducted using -irradiated sediments of varying geochemical compositions and anionic PFC surfactants of varying chain length. Three classes of PFC surfactants were evaluated for sorptive potential: perfluorocarboxylates (PFCAs), perfluoroalkyl sulfonates, and perfluorooctyl sulfonamide acetic acids. Perfluorocarbon chain length was the dominant structural feature influencing sorption, with significant sorption only occurring for PFCs with chain lengths of eight or greater (i.e., PFOS and perfluorononanoate, PFNA). Increasing partition coefficients with increasing chain length were evident for both perfluoroalkyl sulfonates and perfluorocarboxylates, with each CF₂ moiety contributing approximately 0.5 log units to the measured partition coefficients. In addition, the perfluorooctyl sulfonamide acetic acids demonstrated substantially stronger sorption than PFOS. This stronger sorption may be at least partially responsible for the differences in relative abundances of PFOS and PFOS precursors observed between sediments and aqueous systems.

Key words: PFCs, PFOS, sediment, sorption