Contributions of unknown ionizable precursors for perfluoroalkyl acids in the air over a wastewater treatment plant and a landfill

Wastewater treatment plant (WWTP) and landfill are important point sources for emission of per- and polyfluoroalkyl substance (PFAS). However, occurrence and risks of emerging and unknown PFAS in the atmosphere of these sources have not been clarified. An optimized novel cartridge-based active air sampler for both neutral and ionizable PFAS was used to collect air samples from a WWTP and a landfill in Tianjin, China. For target PFAS, the concentrations of neutral PFAS were comparable with those of ionizable PFAS in air samples from both sources. 8:2 Fluorotelomer alcohol (8:2 FTOH) was the predominant neutral PFAS in all the air samples, while ultrashort-chain perfluoroalkyl carboxylic acids (PFCAs) were dominant ionizable PFAS. The optimized total oxidizable precursor (TOP) assay indicated that unknown precursors contributed 46.4–58.4 mol%. This study further revealed the unknown PFAS profiles and their risk in the atmosphere contributed by WWTP and landfill.