Merle M. Plassmann

Per- and polyfluoroalkyl substances (PFAS), particularly perfluorooctanoic acid (PFOA), are persistent, mobile, and difficult-to-remove contaminants in water systems. This study investigates a hybrid adsorption system combining cationic cellulose nanofibers (Cat-CNF) with humic acid (HA) in solution to enhance the removal of PFOA from high-concentration contaminated water sources, such as AFFF-impacted groundwater, industrial effluents, and landfill leachates. Batch experiments spanning a wide concentration range (200–600,000 μg L^–1 PFOA), pH (4.0–11.0), and HA loading (20–100 mg L^–1) revealed that HA strongly binds to Cat-CNF, forming hydrophobic domains that promote PFOA uptake via combined electrostatic and hydrophobic interactions. PFOA adsorption remained high across the full pH range, especially at elevated HA concentrations, and was unaffected by competitive HA presence. Kinetic studies showed that over 90% of PFOA uptake occurred within the first 90 min, reaching equilibrium within 4 h. Isotherm studies showed a steep uptake curve and saturation at ∼250 mg g^–1, with strong fits to both Langmuir (R ² = 0.98) and Freundlich (R ² = 0.89) models. Regeneration experiments demonstrated stable HA retention and progressive improvement in PFOA desorption over multiple cycles, confirming the system’s reusability. These findings highlight the Cat-CNF/HA hybrid as a robust and regenerable adsorbent with rapid equilibrium attainment (within 4 h) for PFOA remediation in high-contamination scenarios, with HA contributing both to contaminant binding and adsorbent performance.

Most known per- and polyfluoroalkyl substances (PFAS) bioaccumulate by binding to proteins or partitioning to phospholipids, leading to their prevalence in liver and blood. However, the recent discovery of high concentrations of unidentified extractable organofluorine (EOF) in the blubber of a killer whale (Orcinus orca) from Greenland suggests that some fluorinated substances preferentially bioaccumulate in storage lipids. To further investigate this, the present work examined blubber from 4 killer whales (3 from Greenland, 1 from Sweden) via gas chromatography-atmospheric pressure chemical ionization-ion mobility mass spectrometry. Using collision cross sections, we prioritized features suspected to be highly fluorinated and then selected 5 for manual annotation. Custom synthesized standards confirmed 10:2 and 12:2 fluorotelomer methylsulfone, 10:2 and 12:2 fluorotelomer chloromethylsulfone, and 6:2 bisfluorotelomer sulfone in all blubber samples from Greenland at concentrations ranging from <0.4 to 72.5 ng/g, explaining 34–75% of blubber EOF, but none in the Swedish sample. None of these substances were observable in liver, suggesting preferential accumulation in storage lipids. To the best of our knowledge, this is the first report of neutral fluorotelomer sulfones in wildlife and the first identification of lipophilic, highly fluorinated PFAS.

[This corrects the article DOI: 10.1021/acs.estlett.4c00774.].

Most known per- and polyfluoroalkyl substances (PFAS) bioaccumulate by binding to proteins or partitioning to phospholipids, leading to their prevalence in liver and blood. As a result, efforts to improve PFAS exposure estimates by identifying novel bioaccumulative substances, have focused on these tissues. However, the recent discovery of high concentrations of unidentified extractable organofluorine (EOF) in the blubber of a killer whale (Orcinus orca) from Greenland suggests that some fluorinated substances bioaccumulate preferentially in storage lipids. The present work builds on this initial finding by characterizing EOF in an additional 3 killer whales (2 from Greenland, 1 from Sweden), and then subjecting extracts from all 4 whales to analysis via gas chromatography-atmospheric pressure chemical ionization-ion mobility mass spectrometry. Using collision cross sections, we prioritized features suspected to be highly fluorinated, and then selected 5 for manual annotation. Custom synthesised standards confirmed 10:2 and 12:2 fluorotelomer methylsulfone, 10:2 and 12:2 fluorotelomer chloromethylsulfone, and 6:2 bisfluorotelomer sulfone in all blubber samples from Greenland at concentrations ranging from <0.4-72.5 ng/g, explaining 34-75% of blubber EOF. None of these substances were observable in liver, suggesting preferential accumulation in storage lipids. To the best of our knowledge, this is the first report of fluorotelomer sulfones in wildlife and the first observation of lipophilic, highly fluorinated PFAS.

Nontargeted screening (NTS) utilizing liquid chromatography electrospray ionization high-resolution mass spectrometry (LC/ESI/HRMS) is increasingly used to identify environmental contaminants. Major differences in the ionization efficiency of compounds in ESI/HRMS result in widely varying responses and complicate quantitative analysis. Despite an increasing number of methods for quantification without authentic standards in NTS, the approaches are evaluated on limited and diverse data sets with varying chemical coverage collected on different instruments, complicating an unbiased comparison. In this interlaboratory comparison, organized by the NORMAN Network, we evaluated the accuracy and performance variability of five quantification approaches across 41 NTS methods from 37 laboratories. Three approaches are based on surrogate standard quantification (parent-transformation product, structurally similar or close eluting) and two on predicted ionization efficiencies (RandFor-IE and MLR-IE). Shortly, HPLC grade water, tap water, and surface water spiked with 45 compounds at 2 concentration levels were analyzed together with 41 calibrants at 6 known concentrations by the laboratories using in-house NTS workflows. The accuracy of the approaches was evaluated by comparing the estimated and spiked concentrations across quantification approaches, instrumentation, and laboratories. The RandFor-IE approach performed best with a reported mean prediction error of 15× and over 83% of compounds quantified within 10× error. Despite different instrumentation and workflows, the performance was stable across laboratories and did not depend on the complexity of water matrices.

A growing number of studies have reported that routinely monitored per- and polyfluoroalkyl substances (PFAS) are not sufficient to explain the extractable organic fluorine (EOF) measured in human blood. In this study, we address this gap by screening pooled human serum collected over 3 decades (1986-2015) in Tromsø (Norway) for >5000 PFAS and >300 fluorinated pharmaceuticals. We combined multiple analytical techniques (direct infusion Fourier transform ion cyclotron resonance mass spectrometry, liquid chromatography-Orbitrap-high-resolution mass spectrometry, and total oxidizable precursors assay) in a three-step suspect screening process which aimed at unequivocal suspect identification. This approach uncovered the presence of one PFAS and eight fluorinated pharmaceuticals (including some metabolites) in human serum. While the PFAS suspect only accounted for 2-4% of the EOF, fluorinated pharmaceuticals accounted for 0-63% of the EOF, and their contribution increased in recent years. Although fluorinated pharmaceuticals often contain only 1-3 fluorine atoms, our results indicate that they can contribute significantly to the EOF. Indeed, the contribution from fluorinated pharmaceuticals allowed us to close the organofluorine mass balance in pooled serum from 2015, indicating a good understanding of organofluorine compounds in humans. However, a portion of the EOF in human serum from 1986 and 2007 still remained unexplained.