Contributions of unknown ionizable precursors for perfluoroalkyl acids in the air over a wastewater treatment plant and a landfill
摘要
Wastewater treatment plants (WWTPs) and landfill represent critical point sources for per- and polyfluoroalkyl substance (PFAS) emission to the atmosphere. This study aimed to (1) quantitatively characterize both neutral and ionizable PFAS in air samples from these sources, and (2) estimate the potential emission contributions of unknown PFAS precursors. Using an optimized cartridge-based active air sampler, we collected atmospheric samples from a WWTP and landfill in Tianjin, China. Quantitative analysis revealed comparable concentration ranges for neutral (Σn-PFAS: 2,816–564,343 pg/m3) were higher than ionizable PFAS (Σi-PFAS: 4,275–13,360 pg/m3), with 8:2 fluorotelomer alcohol (8:2 FTOH; 2,273–13,360 pg/m3) dominating neutral species and trifluoroacetic acid (TFA; 2,490–10,575 pg/m3) prevailing among ionizable compounds. The total oxidizable precursor assay demonstrated that unknown precursors accounted 46.4–58.4 mol% of total PFAS. These findings provide the quantitative evidence of airborne PFAS speciation and associated unknown precursor-derived emission contributions in the WWTP and landfill.