Investigation of per- and polyfluoroalkyl substances (PFAS) in soils and sewage sludges by fluorine K-edge XANES spectroscopy and combustion ion chromatography

Abstract

For the first time, fluorine K-edge X-ray absorption near-edge structure (XANES) spectroscopy was applied to detect per- and polyfluoroalkyl substances (PFAS) in various soil and sewage sludge samples. The method can be used to determine the speciation of inorganic and organic fluorides, without pre-treatment of solid samples. Therefore, XANES spectra of several inorganic fluorides as well as selected fluorinated organic compounds were recorded. While inorganic fluorides partially exhibit a variety of sharp spectral features in the XANES spectrum, almost all inspected organofluorine compounds show two distinct broad features at 688.5 and 692.0 eV. Moreover, the peak intensity ratio 688.5 eV/692.0 eV in the PFAS XANES spectrum can be inversely correlated to the chain length of the perfluoro sulfonic acid group. The detection of targeted PFAS by bulk-XANES spectroscopy in combination with linear combination fitting in soils and sewage sludges was not applicable due to the low organic fluorine to total fluorine ratio of the samples (0.01–1.84%). Nonetheless, direct analysis of pure PFAS revealed that analysis of organofluorine species might be achieved in higher concentrated samples. Furthermore, quantitative measurements by combustion ion chromatography (CIC) evaluated as sum parameters extractable organically bound fluorine (EOF) and total fluorine (TF) emphasize that besides soils, sewage sludges are a significant source of organic fluorine in agriculture (154–7209 µg/kg).

Taking a look at the surface: μ-XRF mapping and fluorine K-edge μ-XANES spectroscopy of organofluorinated compounds in environmental samples and consumer products

“…10 mg kg −1 dry weight based on the fluorine amount by measuring reference samples of PFOS in sand of various concentrations. 32 For the μ-XANES spectroscopy sensitivity approach, we used four fluoride-free sand samples spiked with PFOS methanol solutions at various concentration levels (100 000, 10 000, 1000, and 100 μg kg −1 dw). Therefore, all samples were overlaid with the respective PFAS solutions and subsequently left in a fume hood to evaporate.…”

“…30,31 Previously, we introduced the application of fluorine K-edge X-ray absorption near edge structure (XANES) spectroscopy as an alternative surface analytical method of PFAS contaminated solid matrices. 32…”

“…30,31 Previously, we introduced the application of uorine K-edge Xray absorption near edge structure (XANES) spectroscopy as an alternative surface analytical method of PFAS contaminated solid matrices. 32 The combination of m-XRF mapping and m-XANES spectroscopy has been successfully demonstrated for detection of a wide range of inorganic trace elements in environmental media [33][34][35] but proves difficult for light elements as in organic contaminants. 36 In our study we applied m-XRF mapping in combination with uorine K-edge m-XANES spectroscopy to determine PFAS contamination, spatially resolved in environmental and exemplary consumer product samples.…”

Non-extractable PFAS in functional textiles – characterization by complementary methods: oxidation, hydrolysis, and fluorine sum parameters

“…Details on the limits of quantification (LOQ) and detection (LOD), instrumentation, and measurement parameters are provided in the ESI (Section S2, Tables S5–S8,† for further details see also Gehrenkemper et al 2021 and Roesch et al 2021). 33,35…”

Levels of per- and polyfluoroalkyl substances (PFAS) in various wastewater-derived fertilizers – analytical investigations from different perspectives

“…4–14 In addition to direct discharge of PFAS through effluents, sewage sludge has been observed to be an important pathway for PFAS release to agricultural soils. 15–21…”