In situ occurrence and mobility of per and polyfluoroalkyl substances in soils amended by biosolids, composts and other organic waste products
Résumé
Per- and polyfluoroalkyl substances (PFAS) can be found at significant levels in municipal biosolids and other organic waste products (OWPs) used as agriculture fertilizers. However, limited information is available regarding their fate in soil-water systems from long-term applications. In this study, we evaluated the in situ occurrence and soil-water distribution of 75 anionic, zwitterionic, and cationic PFAS in soils from five experimental field sites distributed in different climatic regions in France. At each site, soil plots received agronomical doses of OWPs (~5-15 t/ha per application), with repeated inputs between 1974-1996 (2 historical sites) and 1998-2018 (3 on-going sites). 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, with soils receiving biowaste composts displaying the lowest Σ75PFAS. Σ75PFAS also increased significantly with time. While PFOS typically dominated the PFAS profiles in municipal biosolid-amended soils, the other prevalent PFAS classes varied with site typology and years. Interestingly, 6:2 fluorotelomer sulfonamidopropyl betaine (6:2 FTAB), a major zwitterionic precursor found in French municipal biosolids, was only detected at low levels in soils, indicating its transformation to degradation products. Drainage waters leaching from the experimental plots had relatively high levels of short-chain PFCAs, with increased mobility at higher water pH.