Water-to-air transfer of perfluorinated carboxylates and sulfonates in a sea spray simulator

Abstract

Environmental contextPerfluorinated alkyl acids are found in the remotest parts of the world, but it is still not known how they get there. By using a laboratory sea spray simulator, it is shown that these compounds are efficiently transferred from water to air. This indicates that perfluorinated alkyl acids could be transported long distances as a result of breaking waves ejecting them into the atmosphere. AbstractOne hypothesis for the origin of perfluorinated alkyl acids, their salts and conjugate bases (here collectively termed PFAAs) in the atmosphere is transfer from the surface ocean by sea spray, the mechanistic explanation being that the surface active properties of PFAAs result in their enrichment on the surface of bursting bubbles. The water-to-air transfer of C6–C14 perfluorocarboxylates (PFCAs) and C6, C8 and C10 perfluorosulfonates (PFSAs) was studied in a laboratory scale sea spray simulator containing tap water spiked with PFCAs and PFSAs. The sequestration of the PFAAs out of bulk water and to the air–water surface was shown to increase exponentially with the length of the perfluorinated alkyl chain. Volatilisation of the PFAAs from an aqueous solution in the absence of spray resulted in less than 1 % transfer to the atmosphere during the experiment. In the presence of spray the transfer rate from water to air increased by up to 1360 times. The enhancement was dependent on the PFAA chain length, with the C6 carboxylate showing an enhancement of a factor of 37, the C7 carboxylate an enhancement of 320, whereas for all remaining PFAAs the enhancement exceeded 450 with the exception of the C14 carboxylate (106).