Sorption, Aerobic Biodegradation, and Oxidation Potential of PFOS Alternatives Chlorinated Polyfluoroalkyl Ether Sulfonic Acids

Global phase out of perfluorooctanesulfonic acid (PFOS) has led to increasing production of alternatives such as the chlorinated polyfluoroalkyl ether sulfonic acids (Cl-PFESAs) for which little is known on their environmental fate. In this study, sorption by soils, aerobic soil biodegradation, and oxidation potential of 6:2 Cl-PFESA (9-chlorohexadecafluoro-3-oxanonane1-sulfonate) and 8:2 Cl-PFESA (9-chlorooctadecafluoro-3-oxanonane-1-sulfonate) were evaluated. 6:2 Cl-PFESA sorption was quantified for aqueous and acetone/water solutions, whereas 8:2 PFESA could only be accurately measured in acetone/water solutions. The log-linear cosolvency model was applied and validated to estimate sorption of 8:2 Cl-PFESA. Only soil organic carbon (OC, 0.76-4.30%) was highly and positively correlated to sorption of the Cl-PFESAs (R-2 > 0.96). The resulting log K-oc values (OC-normalized sorption coefficients) are 4.01 +/- 0.09 (n = 6) and 5.54 +/- 0.05 (n = 4) L kg(-1) for 6:2 Cl-PFESA and 8:2 Cl-PFESA, respectively. Aerobic biodegradation in a loam soil at 24 +/- 0.5 degrees C showed negligible degradation of both CI-PFESAs. Cl-PFESAs also remained unchanged in an unbuffered heat (50 degrees C)-activated 42 mM persulfate oxidation treatment. Therefore, Cl-PFESAs are equally recalcitrant as PFOS in addition to being more sorptive, thus with a higher bioaccumulation potential for a similar alkyl chain length.