Atmospheric PFAS Partitioning and Source Attribution Using a Trajectory-Informed Non-Targeted Approach: Insights from Seoul

Abstract

Poly- and perfluoroalkyl substances (PFASs) are synthetic chemicals widely used in industrial and consumer products. Their persistence, resistance to degradation, and potential toxicity raise concerns regarding their environmental fate and transport. This study investigates atmospheric PFAS concentrations in Seoul, Korea, focusing on their gas/particle partitioning behavior. A total of 21 atmospheric samples were collected from February 10 to June 20, 2024, using a High-Volume Air Sampler. Particulate matter was captured on Quartz Fiber Filters (QFF), while gas-phase compounds were collected using polyurethane foam (PUF)/activated carbon felt (ACF) /PUF blocks. The samples were analyzed by HPLC-MS/MS. Total PFAS concentrations ranged from 8.891 to 168.0 pg/m³ (mean: 51.68 pg/m³, median: 30.13 pg/m³). Among PFCAs, PFBA (24.62 ± 21.31 pg/m³, median: 13.50 pg/m³) was the most prevalent, followed by PFOA (1.494 ± 1.022 pg/m³, median: 1.330 pg/m³). In PFSAs, PFBS (19.37 ± 28.60 pg/m³, median: 2.767 pg/m³) dominated, whereas PFOS (0.3888 ± 0.26 pg/m³, median: 0.3880 pg/m³) was the second most abundant. Overall, short-chain PFASs (C≤7) exhibited higher concentrations than long-chain PFASs (C≥8). For example, the concentrations of PFPeA (0.9160 pg/m³) and PFHxA (0.3095 pg/m³) were higher compared to PFDA (0.0767 pg/m³) and PFUnDA (0.0650 pg/m³). Phase-distribution analysis showed that PFBA (74%) and PFBS (99%) were predominantly in the gas phase, whereas PFOA (53%) and PFOS (80%) were more commonly found in the particle phase. The gas/particle partitioning indicated that short-chain PFASs are more volatile and likely to undergo long-range transport, whereas long-chain PFASs exhibit a stronger tendency to adhere to particulate matter and deposit locally. In addition to target analysis, non-target screening (NTS) was conducted using high-resolution mass spectrometry to explore unknown PFASs in the atmosphere. Orbitrap-MS data were processed through the FluoroMatch Modular workflow, and 43 features with confidence level C or higher were identified. These features include many compounds that are not reported in existing databases, suggesting the presence of novel or transformation-derived PFASs. Multivariate analysis using Partial Least Squares Discriminant Analysis (PLS-DA) enabled differentiation of chemical profiles by air mass origin and revealed source-specific PFAS candidates. This integrated approach combining targeted quantification and NTS-based discovery highlights the complexity of airborne PFAS mixtures and underscores the necessity for comprehensive monitoring strategies.