Concentrations of perfluoroalkyl substances in sediments and wastewater treatment plant-derived biosolids from Ireland

Concentrations of 39 perfluoroalkyl substances (PFAS) are reported in 120 inland and transitional sediments from Ireland. We also report concentrations in 21 samples of biosolids from seven Irish wastewater treatment plants (WWTPs; n = 3 from each). This is the first report of the presence (% detection frequency) in sediments of: perfluroroundecane sulfonate (PFUdS) (7.4 %), perflurorododecane sulfonate (PFDoS) (8.6 %), perfluorotridecane sulfonate (PFTrDS) (7.4 %), 11-chloroeicosafluoro-3-oxaundecane-1-sulfonate (11Cl-PF3OUdS or 8:2 Cl-PFESA) (7.4 %), and 9-chlorohexadecafluoro-3-oxanonane-1-sulfonate (9Cl-PF3ONS or 6:2 Cl-PFESA) (2.5 %) and of the following in biosolids: PFDoS (24 %), PFTrDS (38 %), and perfluoroethylcyclohexane sulfonate (PFECHS) (38 %). Concentrations of all target PFAS in biosolids exceed significantly (p < 0.05) those in sediments. Moreover, the relative abundance of different PFAS classes differs markedly. In sediments, perfluorocarboxylic acids (PFCAs) dominate (on average 55 % ΣPFAS), while in biosolids, PFCAs constitute on average 26 % ΣPFAS, with perfluorosulfonic acids (PFSAs) the main group (37 % ΣPFAS). This suggests PFAS in Irish sediments are a complex integral of many sources, of which WWTPs are just one. Concentrations in sediments were assessed for ecotoxicity by comparison with predicted no effect concentration (PNEC) values promulgated by the NORMAN network. In general, concentrations detected are well below PNECs. However, the PNEC for perfluorooctane sulfonic acid (PFOS) is exceeded for most sediments. While overall, novel PFAS (nPFAS) like sodium 2,2,3-trifluor-3-(1,1,2,2,3,3-hexafluoro-3-trifluormethoxypropoxy) propionate (ADONA), PFECHS, and 2,3,3,3-tetrafluoro-2-(1,1,2,2,3,3,3-heptafluoropropoxy)propanoic acid (HFPO-DA aka Gen-X) are present in low abundance in biosolids and sediments; 11Cl-PF3OUdS (90 % ΣPFAS) dominates one sediment, while two other sediments contain Gen-X at 59 and 69 % ΣPFAS respectively. This suggests unidentified local sources of these nPFAS at those sites.