In situ occurrence and mobility of per and polyfluoroalkyl substances in soils amended with organic waste products

Abstract

We evaluated the in situ occurrence and soil-water distribution of 75 anionic, zwitterionic, and cationic per- and polyfluoroalkyl substances (PFAS) in soils from five field experimental sites distributed in different climatic regions in France. Four sites received agronomical doses of organic waste products (OWPs, ∼5–10 t/ha per application) with repeated inputs between 1974 and 1996 (2 historical sites) and 1998–2018 (2 on-going sites), while one site received about two-fold larger amounts. Control soils without OWP application had detectable yet low PFAS levels, the Σ75PFAS remaining in most cases below 1 μg/kg. Soils amended with municipal sludge or urban composts exhibited the largest Σ75PFAS increase relative to controls (∼2–20 μg/kg), with soils receiving biowaste composts displaying the lowest Σ75PFAS (∼2 μg/kg). In most cases, Σ75PFAS increased significantly with time. While perfluorooctane sulfonate (PFOS) typically dominated the PFAS profiles in municipal sludge-amended soils, the other prevalent PFAS classes varied with sites and years: soils from older sites also had anionic and cationic electrochemical fluorination-derived precursors (e.g., EtFOSAA and PFOSAmS), while on-going sites had increased prevalence of short-chain perfluoroalkyl carboxylates (PFCAs) (3 sites) and perfluoroalkyl phosphinates (1 site). Interestingly, 6:2 fluorotelomer sulfonamidopropyl betaine (6:2 FTAB), a major zwitterionic precursor found in French municipal sludge, was only detected at low levels in soils, indicating its transformation to degradation products. Leaching waters at a depth of 45 cm in the experimental plots had high levels of short-chain PFCAs (Mean C3-C5: 120–160 ng/L; Max C3-C5: 900–1600 ng/L), suggesting that land applied OWP containing PFCA precursors are important contributors to long-term groundwater contamination.