Extending the Monitoring of Perfluoroalkyl Substances in Arctic Air Reveals a High Abundance of Both Short Acids and Neutral Compounds.

Interest in per- and polyfluoroalkyl substances (PFASs) in the remote atmosphere now extends to perfluoroalkyl carboxylic acids (PFCAs) and perfluoroalkyl sulfonic acids (PFSAs) with short ( < 4), medium (3 < < 13), and long ( > 12) alkyl chains. A liquid chromatography-mass spectrometry method for the combined analysis of PFASs of variable chain length was applied to 204 high volume active air samples collected at Alert, Nunavut (82° 30' N 62° 20' W) between March 2014 and October 2023. Short-chain PFASs (scPFASs) were detected frequently (>75%) and at the highest median concentrations (trifluoroacetic acid (TFA): 20 pg/m, perfluoropropionic acid (PFPrA): 1.1 pg/m, perfluorobutanoic acid (PFBA): 3.7 pg/m), while n > 10 PFAS were sparsely detected (detection frequency [DF] < 20%). Using a suspect-screening approach, hexafluoro-2,2-propanediol (HF2OH) and hexafluoroisopropanol (HFIPA) were confirmed in Arctic air at DF exceeding 75%. We find that concentrations of TFA and HF2OH were significantly correlated with temperature and increased during snowmelt periods, suggesting local emission or precursor release followed by degradation processes. The modified OECD LRTP and Pov assessment tool supported the potential of HFIPA and HF2OH to undergo long-range atmospheric transport. Time trend analysis reveals that after a short period of stable or declining levels in the mid-2010s, concentrations of PFBA, PFOA, and PFOS in Arctic air are increasing again since 2019, which may be a useful consideration when evaluating the effectiveness of the Stockholm Convention's listing of PFOA and PFOS.