Long-term trend data for PFAS in soils from German ecosystems, including TOP assay

Total and Class-Specific Determination of Fluorinated Compounds in Consumer and Food Packaging Samples Using Fluorine-19 Solid-State Nuclear Magnetic Resonance Spectroscopy

Hamburger wrapping paper, coated with water-based barrier coatings, used in the food packaging industry was studied by using the total organic fluorine (TOF) method based on combustion ion chromatography and fluorine-19 solid-state nuclear magnetic resonance (19F ss-NMR) spectroscopy. Although the TOF method is a fast and affordable method used to screen for per- and polyfluoroalkyl substances (PFAS), the amount of fluorine it measures is heavily dependent on the extraction step and, therefore could lead to inaccurate results. Fluorine-19 ss-NMR spectroscopy can differentiate between organic and inorganic fluorinated sources, eliminating the need for sample clean up. To illustrate this, the 19F ss-NMR spectra of clean coated paper samples that contained naturally occurring F- ions from the talc raw material and spiked samples containing perfluorooctanoic acid were compared. A range of experimental conditions was explored to improve sensitivity for low PFAS concentrations (in the order of 10-20 mg/kg). Despite the disadvantages of ss-NMR spectroscopy, such as the low limit of detection and resolution, the results demonstrate it can be a viable tool to directly detect PFAS moieties in consumer and food packaging. Therefore, 19F solid-state NMR spectroscopy challenges and complements current methods, which only provide indirect evidence of the presence of PFAS.

Influence of microplastic contamination on the dissipation of endocrine disrupting chemicals in soil environment

Microplastic (MP) contamination is in the spotlight today, yet knowledge of their interaction with other organic contaminants in the soil environment is limited. Concerns extend to endocrine disrupting chemicals (EDCs), known for their potential to interfere with the hormonal systems of organisms and for their persistence and widespread presence in the environment. In this study, the most frequently occurring EDCs were monitored both in alluvial soil and in soil contaminated with different MPs commonly found in soil media, polyethylene, polyamide, and polystyrene. Bisphenol A and parabens were the most rapidly dissipating compounds, followed by triclosan and triclocarban, with the latter showing poor degradation. Per- and polyfluoroalkyl substances (PFAS) showed high persistence as concentrations remained nearly constant throughout the experiment. Although they fitted well with first-order dissipation kinetics, most showed biphasic behavior. The co-occurrence of MPs in the soil influenced the kinetic behavior in most cases although the differences were not very marked. MPs could impact sorption-desorption processes, affecting contaminant mobility and bioavailability to organisms in soil. These findings strengthen evidence for the influence of MPs on the behavior of soil contaminants such as EDCs, not only as vectors or sources of contaminants but by affecting dissipation kinetics.

Fluorine mass balance analysis in wild boar organs from the Bohemian Forest National Park

Wild boars have been reported as bioindicators for per- and polyfluoroalkyl substances (PFAS) in a variety of studies. However, data about PFAS levels in wild boars from sites with limited industrial and general human activity is scarce. In this study, wild boar (Sus scrofa) organs from the Bohemian Forest National Park (Czech Republic) were used as bioindicators for PFAS pollution. In this work, 29 livers and 24 kidneys from 30 wild boars (0.5-5 years) were investigated using a fluorine mass balance approach. For this, the samples were measured using high performance liquid chromatography with electrospray ionisation tandem mass spectrometry (HPLC-ESI-MS/MS), targeting 30 PFAS, including legacy and replacement PFAS, direct total oxidisable precursor assay (dTOPA) and combustion ion chromatography (CIC). Perfluorocarboxylic acids (PFCAs) from C7 to C14 and perfluorooctanesulfonic acid (PFOS) were detected in >50 % of samples. In the livers, PFCAs dominated the profile with median concentrations of 230 μg/kg for perfluorononanoic acid (PFNA) and 75 μg/kg perfluorooctanoic acid (PFOA). PFOA and PFNA concentrations in the livers were one order of magnitude higher than in livers from wild boars caught in rural NE Germany considered as background concentration. PFOS in liver contributed only 30 % to the Σc(PFASTarget) with a median concentration of 170 μg/kg. Kidneys and livers contain an average of 2460 μg F/kg and 6800 μg F/kg extractable organic fluorine (EOF) respectively. Σc(PFASTarget) add up to a maximum of 10 % of the extractable organic fluorine. After oxidisation of the samples, PFOA, PFNA and Σc(PFASdTOPA) increased in livers, but could not explain the EOF. The elevated concentration of PFOA and PFNA may indicate differences in biomagnification for different habitats or an unidentified PFAS source in proximity to the national park.

Application of Gaussian mixture models to quantify the upper background threshold for perfluorooctane sulfonate (PFOS) in U.S. surface soil

Studies on the occurrence and environmental distribution of per- and polyfluoroalkyl substances (PFAS) have clearly demonstrated their ubiquity in surface soil as a result of historic and ongoing emissions from various manufacturing and industrial activities worldwide. Given global efforts to characterize and mitigate risk from point source-impacted sites, there is, thus, an urgent need to quantify nonpoint source threshold concentrations (i.e., background) to support site management decisions particularly for perfluorooctane sulfonate (PFOS) as a top priority. Accordingly, this study evaluated the application of Gaussian mixture models (GMMs) fitted to log-transformed PFOS concentrations using nation-wide metadata consisting of thousands of surface soil samples representative of both background and aqueous film-forming foam (AFFF) impacts with unknown proportion. Multiple GMMs were fitted for a given number of components using different methods to account for bias associated with a marginal non-detect fraction (n = 8%) including exclusion, substitution, and imputation. Careful evaluation of the rate of change among multiple goodness-of-fit measures universally justified fitting a 2-component GMM; thus, discriminating between background and AFFF-impacted samples among the metadata. Background threshold PFOS concentrations were defined as the intersection of the probability density functions and ranged between 1.9 and 13.8 µg/kg within a broader concentration range extending up to ~ 50,000 µg/kg reflecting AFFF impacts. By demonstrating an innovative statistical approach that intelligently incorporates different criteria for model selection, this research makes significant contributions to risk mitigation efforts at point source-impacted sites and lays the groundwork for future targeted regulatory actions.

Metabolic and Microbial Profiling of Soil Microbial Community under Per- and Polyfluoroalkyl Substance (PFAS) Stress

Per- and polyfluoroalkyl substances (PFAS) represent significant stress to organisms and are known to disrupt microbial community structure and function. Nevertheless, a detailed knowledge of the soil microbial community responding to PFAS stress at the metabolism level is required. Here we integrated UPLC-HRMS-based metabolomics data with 16S rRNA and ITS amplicon data across soil samples collected adjacent to a fluoropolymer production facility to directly identify the biochemical intermediates in microbial metabolic pathways and the interactions with microbial community structure under PFAS stress. A strong correlation between metabolite and microbial diversity was observed, which demonstrated significant variations in soil metabolite profiles and microbial community structures along with the sampling locations relative to the facility. Certain key metabolites were identified in the metabolite-PFAS co-occurrence network, functioning on microbial metabolisms including lipid metabolism, amino acid metabolism, and secondary metabolite biosynthesis. These results provide novel insights into the impacts of PFAS contamination on soil metabolomes and microbiomes. We suggest that soil metabolomics is an informative and useful tool that could be applied to reinforce the chemical evidence on the disruption of microbial ecological traits.