Polyfluorinated alkyl substances (PFAS) are a group of organic chemicals, many of which combine bioaccumulative potential, toxic effects and extreme persistence. Furthermore, certain PFAS are volatile and thus prone to long-range atmospheric transport (LRAT). Therefore, they are considered as 'candidates' for the Stockholm Convention list of persistent organic pollutants (POPs) and are
regarded as a new and emerging class of environmental contaminants. Their widespread use for surface treatment in carpets and textiles, in polymer (e.g. polytetrafluoroethylene, PTFE) production, in fire-fighting foams and insecticides underlines the relevance of PFAS as a group of environmental pollutants.
The two most studied C 8 -PFAS (perfluorooctane sulfonate, PFOS and perfluorooctanoate, PFOA) are distributed ubiquitously despite their non-volatility and only moderate water-solubility. The
hypothesis that neutral, volatile precursor compounds of PFOS and PFOA could undergo LRAT and be degraded to the persistent, ionic PFAS in remote regions like the Canadian and European Arctic was the main motivation for this thesis. It was designed to improve our understanding of the occurrence, distribution pattern and transport mechanisms of neutral, volatile PFAS between source
regions and remote, marine locations.
This PhD thesis can be subdivided into three basic sections. First of all, the development, optimisation and validation of a trace-analytical method for the sampling and determination of neutral, volatile PFAS in environmental air samples was indispensible (see publication I). The analytical protocol
included the following substances: four fluorotelomer alcohols (FTOHs), 4:2 FTOH, 6:2 FTOH, 8:2 FTOH and 10:2 FTOH, as well as two N-alkyl fluorooctane sulfonamides (NMeFOSA/ NEtFOSA) and N-alkyl fluorooctane sulfonamidoethanols (NMeFOSE/NEtFOSE) each.
Secondly, the analytical method was tested at a location with presumed relatively high environmental air concentrations of the investigated compounds (metropolitan Hamburg). In comparison, it was also applied to air samples from a rural location in Northern Germany (Waldhof, background moni-
toring station of the German Federal Environmental Agency, UBA and European Monitoring and
Evaluation Program, EMEP, see publication II).
Thirdly, in order to investigate the concentration gradient of neutral, volatile PFAS between locations with relatively high production and emission and less industrialised areas, air samples were taken on board of the German research vessel Polarstern (see publication III ). Expedition ANTXXIII-1 between Bremerhaven, Germany, and Capetown, Republic of South Africa, was used to determine the latitudinal gradient of the investigated compounds in coastal regions of both hemispheres.
Further sampling was done in the European Arctic on Polarstern expeditions ARKXX-1/2. Additionally, in order to investigate European background levels of neutral, volatile PFAS for comparison with the ship-based data, a sampling campaign was performed at Mace Head, West coast of Ireland.
Finally, a new sampling method for airborne PFAS using commercially available solid-phase extraction (SPE) cartridges was developed and applied to indoor as well as outdoor air samples.
Prior to the PhD thesis at hand, no information on the occurrence and distribution of neutral, volatile PFAS outside North America was available. This work generated first concentration data of this group of compounds from Europe and the Southern Hemisphere. Finally, the data sets from Germany
and the latitudinal transect help in the scientific discussion to estimate fluxes of airborne PFAS to remote, polar regions and to elucidate their worldwide occurrence.