Total Fluorine Research Articles

Quantitative assessment of poly- and perfluoroalkyl substances (PFASs) in aqueous film forming foam (AFFF)-impacted soils: a comparison of analytical protocols.

Quantitatively assessing all per- and poly fluoroalkyl substances (PFASs) in an environmental sample, particularly soils impacted by aqueous film forming foams (AFFFs), has proven to be a challenge. To make such an assessment, a comprehensive sample processing procedure and analytical tool must be used. However, doubts remain whether current analytical tools such as high-resolution mass spectrometry (HRMS) with targeted quantitation and semi-quantitative analysis of suspects (Semi-Q HRMS) or total organic fluorine (TOF) are capable of accurately quantifying all non-polymeric PFASs in a sample. Further, current comprehensive soil PFAS HRMS methods are incompatible with TOF, preventing direct comparisons of the approaches. To enable direct comparisons, a soil sample processing procedure that is comprehensive as well as compatible with multiple analytical tools is needed. In this study, we assessed the performance of a previously developed soil PFAS method, EPA Method 1633, and a hybrid solid phase extraction (SPE)-based method for characterizing AFFF-impacted soil composites while maintaining compatibility with multiple analytical tools (i.e., Semi-Q HRMS and TOF). Comparative results for AFFF-impacted soil composites indicate analysis via EPA Method 1633 (as compared to the novel hybrid method) results in maybeup to 75% of the PFAS mass being missed by only analyzing for compounds listed in EPA Method 1633. Simply expanding the EPA Method 1633 analyte list was insufficient to account for the missing mass: up to 69% of the PFAS mass was still missed because of EPA Method 1633's extraction and cleanup bias. Additionally, the novel method developed offers a more comprehensive analysis with minimal reductions to sensitivity when compared to those reported in EPA Method 1633, with limits of quantification ranging from 0.12 to 2.4 ng/g as compared to 0.16-4.0 ng/g, respectively. For these reasons, an alternative hybrid SPE-based method is proposed for comprehensive evaluation of PFASs in AFFF-impacted soils.

Perfluoroalkyl acid precursor or weakly fluorinated organic compound? A proof of concept for oxidative fractionation of PFAS and organofluorines.

Organofluorine mass balance approaches are increasingly applied to investigate the occurrence of per- and polyfluoroalkyl substances (PFAS) and other organofluorines in environmental samples more comprehensively. Usually, complex samples prevent the identification and quantification of every fluorine-containing molecule. Consequently, large unidentified fractions between fluorine sum parameters such as extractable organic fluorine (EOF) and the sum of quantified analytes are frequently reported. We propose using oxidative conversion to separate (unidentified) weakly fluorinated compounds (e.g., pesticides, pharmaceuticals) from PFAA-precursors (perfluoroalkyl chain lengths ≥ C6). We show with three organofluorine model substances (flufenamic acid, diflufenican, pantoprazole) that CF3-groups or aromatic fluorine can be quantitatively converted to inorganic fluoride and trifluoroacetic acid (TFA) by applying PhotoTOP oxidation (UV/TiO2). The principle of fluorine separation in mixtures is demonstrated by the oxidation of the three weakly fluorinated compounds together with the PFAA-precursor 6:2/6:2 fluorotelomer mercaptoalkyl phosphate diester (FTMAP). After oxidation, the products F- and TFA were separated from PFCAs (> C4) by SPE, and the fractions were analyzed individually. Closed mass balances both with and without the addition of organic matrix were achieved. Eventually, the fluorine balance was verified by total fluorine measurements with combustion ion chromatography (CIC). The proposed methods should be considered a proof of concept to potentially explain unidentified fractions of the EOF, especially if compounds with low fluorine content such as pesticides, pharmaceuticals, and their transformation products contribute largely to the EOF. Future studies are needed to show the applicability to the complexity of environmental samples.

Per- and polyfluoroalkyl substances (PFAS) in Ski waxes and snow from cross-country skiing in Germany - Comparative study of sum parameter and target analysis

Per- and polyfluoroalkyl substances (PFAS) are often environmentally exposed via discharge through human consumer products, such as ski waxes. In our study we analyzed various ski waxes from the 1980s and 2020s, to determine both the sum parameter values total fluorine (TF), extractable organically bound fluorine (EOF), hydrolysable organically bound fluorine (HOF) as well as targeted PFAS analysis. This showed that modern high-performance waxes contain up to 6 % TF, but also PFAS-free labelled ski waxes contain traces of PFAS with EOF/HOF values in the low mg kg-1 range. With the ban of all fluorine-based waxes with the start of the 2023/2024 winter season this will probably change soon. Moreover, we applied our analysis methods to snow samples from a frequently used cross country ski trail (Kammloipe) in the Ore Mountain region in Germany, assessing the potential PFAS entry/discharge through ski waxes. Melted snow samples from different spots were analyzed by the adsorbable organically bound fluorine (AOF) sum parameter and PFAS target analysis and confirmed the abrasion of the ski waxes into the snow. Moreover, on a PFAS hotspot also soil samples were analyzed, which indicate that PFAS from the ski waxes adsorb after snow melting into the soil.

Removal and recovery of phosphorus and fluorine in process water from water based direct physical lithium-ion battery recycling

In the present work, the recovery of phosphorus and fluorine from process water generated in a water based direct physical recycling process of Li-ion batteries has been studied. The recycling process considered in this work produces significant amounts of process water, which is generated during the opening of the batteries by means of electro-hydraulic fragmentation and the subsequent sorting of the components in aqueous solution. This process produces between 21.6 L and 30.3 L of process water per kg of batteries with a total phosphorus and a total fluorine concentration of 60–85 mg/L and 120–470 mg/L, respectively. Currently, the process water has to be disposed of as hazardous waste. The goal is to discharge the wastewater into the sewer system. For this the total phosphorus and total fluorine concentration must be reduced. The process water is mainly contaminated by the released electrolyte consisting of organic carbonates and conducting salts. 31-P and 19-F NMR shows conclusively that no hydrolysis takes place in this process water. The phosphorus is present exclusively in the form of the complex anion PF6- and fluorine as F-, namely as FSI- from the conducting salt LiFSI and PF6- from the conducting salt LiPF6. In order to meet the regulatory requirements for discharge into the sewage system, 70.4% of the phosphorus and 89.3% of the fluorine must be removed. The conducting salts are hydrolyzed by adding acid and thereby phosphate and fluoride are precipitated. After critical and valuable materials are recovered the process water can be discharged into the sewer system.

Understanding the impact of pre-digestion thermal hydrolysis process on PFAS in anaerobically digested biosolids

Per- and poly-fluoroalkyl substances (PFAS) present in biosolids are influenced by their source, treatment processes, and the dynamics of water resource recovery facilities (WRRF). Understanding these effects is vital for informed decisions in treatment process selection, however, comprehensive studies are sparse. This study examined the impact of anaerobic digestion (AD) and the addition of a thermal hydrolysis process (THP) before AD on PFAS in the solids stream at a WRRF. Targeted analysis of 58 PFAS (linear and branched) and suspect screening of the solid stream before and after AD as well as THP, with the total PFAS (ΣPFAS) concentrations ranging between 244 and 566 μg/kgdw. Precursor and intermediate PFAS, mainly di-substituted polyfluoroalkyl phosphate esters (diPAPs) followed by fluorotelomer carboxylic acids (FTCAs), were the dominant contributors (62–96 mol % ΣPFAS) in all 5 sample types. AD impacts were observed both before and after deploying THP altering the relative contribution of different PFAS classes through biotransformation, with an increase in PFCAs and a decrease in diPAPs. However, we observed that THP reduced the % of precursor conversion as well as conversion of the FTCA intermediates in the AD process as evidenced by a substantial increase in FTCAs post-THP + AD and lower PFCA generation compared to AD only. Total PFAS organofluorine (∑FPFAS) decreased by 28% pre- and post-AD, which on total fluorine (TF) showed a larger reduction to 43%. Fluoride was <3% of the TF in all cases, thus, the greater reduction in TF vs ∑FPFAS could be volatile losses of PFAS and other non-PFAS F-containing molecules. After THP installation, a 32% decrease in (∑FPFAS) was observed in the combined THP-AD system whereas adjusted total organofluorine increased by ∼43%. Overall, achieving higher solids handling capacity and energy neutrality with the THP addition did not lead to a significant difference in quantifiable PFAS concentrations compared to AD-only.

Closing PFAS analytical gaps: Inter-method evaluation of total organofluorine techniques for AFFF-impacted water

Multiple poly- and perfluoroalkyl substances (PFASs) are present in aqueous film-forming foams (AFFF) used for firefighting activities. Currently, no single analytical technique provides a complete accounting of total PFASs or total organofluorine content in AFFF-contaminated samples. To provide insight into the performance of existing methods, we compared ten previously described PFAS measurement techniques. In AFFF-amended tap water, US EPA Methods 533 and 1633, adsorbable organic fluorine with particle induced gamma emission spectroscopy (AOF-PIGE) and fluorine-19 nuclear magnetic resonance (19F NMR) provided similar estimates of total fluorine. The total oxidizable precursor (TOP) assay, suspect screening, and adsorbable organic fluorine with combustion ion chromatography (AOF-CIC) yielded estimates of total organic fluorine that were about two to three times higher than the other techniques. Proximate to AFFF sources, suspect screening and modified EPA Method 1633 yielded higher results, while the TOP assay results were between the other two sets of analyses. Further from sources, suspect screening, modified EPA Method 1633, and the TOP assay yielded similar results that were 4-fold higher than results from targeted quantification methods, such as EPA Method 1633. These results are consistent with expectations about PFAS behavior and inform the selection of analytical techniques used for PFAS contamination characterization efforts.

Comparing the obesogenic effect and regulatory mechanisms of long-term exposure to per/polyfluoroalkyl substances with different terminal groups in Caenorhabditis elegans

Per/polyfluoroalkyl substances (PFASs) are ubiquitous, bioaccumulative, and recalcitrant contaminants, posing global exposure and health risks. The effects of chemical structures on toxicities and the mechanisms of their obesogenic effects were largely unclear. This study used the model organism Caenorhabditis elegans to assess the impact of long-term exposure to different PFASs (PFNA, PFOSA, PFBS, PFHxS, 6:2 FTS, 4:2 FTS, PFOA, and PFOS) on growth and lipid metabolism and discussed the obesogenic mechanisms of selected PFASs. The growth assays indicated longer carbon-fluorine (-CF) chains and total fluorine atoms increased developmental toxicity of PFASs, while at 8 –CF chain-length, PFNA (-COOH terminal), PFOS (-SO3 terminal), and PFOSA (-SO2NH2 terminal) exhibited differential growth inhibition. With the toxicity ranking of PFNA > PFOS > PFOSA, all PFASs significantly induced total lipid accumulation and perturbed the lipid composition in C. elegans. All three PFASs significantly induced lipogenesis gene expression and partially suppressed lipolysis genes. The results suggested that the disruption of lipid metabolism of PFOSA depends on sbp-1, while PFNA and PFOS depend on nhr-49. In conclusion, long-term exposure to PFNA, PFOSA, and PFOS triggers obesogenic effects in organisms by distinct molecular mechanisms.

Per- and polyfluoroalkyl substances behavior: Insights from autothermal thermophilic aerobic digestion - Storage nitrification-denitrification reactors

Per- and polyfluoroalkyl substances (PFAS) have emerged as significant environmental contaminants due to their persistence, bioaccumulative properties, and potential adverse impacts on health and ecosystems. Water Resource Recovery Facilities (WRRFs) play a crucial role in the management of PFAS, given their widespread presence in consumer products and subsequent reintroduction into the environment. This study investigated the dynamics of PFAS within the solids stream treatment processing that utilized autothermal thermophilic aerobic digestion (ATAD) followed by a storage nitrification-denitrification reactor (SNDR). PFAS analysis included 60 PFAS analyzed via liquid chromatography-triple quadrupole time-of-flight mass spectrometry of pre-ATAD, post-ATAD, and post-SNDR samples. Complexities such as volatile solids loss during the treatment processes were considered in assessing the effect of ATAD and SNDR on PFAS concentrations. Significant changes were observed in the relative contributions of various PFAS classes throughout the treatment processes due to biotransformation; similar changes were reflected in both 2019 and 2021. The relative contribution of perfluoroalkyl alkyl acids (PFAAs) increased while phosphorus-containing PFAS (e.g., di-substituted polyfluoroalkyl phosphate esters) and fluorotelomer carboxylic acids decreased. Shorter-chain PFAAs were enriched during ATAD, whereas most PFAS increased during SNDR except diPAPs and FTCAs, reflecting treatment conditions' impact. Overall, minor decreases in total PFAS concentrations during ATAD as well as SNDR were observed and hypothesized to be due to enhanced biotransformation to ultra-short PFAS that were not quantified. Even with up to 60 PFAS quantified in the samples, PFAS accounted for <1% of the total fluorine with <2% of that total fluorine being fluoride prompting interest in additional exploration.

Biochar from paddy field - A solution to reduce PFAS pollution in the environment

Generally, activated carbons demonstrated a notable ability to capture long-chain PFAS, but exhibited relatively lower effectiveness for short-chain PFAS. Thirteen commercially available activated carbons in Japan underwent testing for their adsorption capacity of PFAS in water. The activated carbon derived from rice husk, Triporous™-PFAS, exhibited the highest adsorption capacity (over 95%) for PFAS from ultrashort-chain (perfluorocarbon chain: C1 for perfluorocarboxylic acid (PFCA) and C2 for perfluoroalkane sulfonic acid (PFSA)) to long-chain PFAS (C13 for PFCA and C10 for PFSA). An earlier lysimeter study highlighted Andosol, representative soil in Japan, as a potential medium for removing PFAS from irrigation water. Considering cultivating rice on Andosol fields and producing biochar from rice husks and rice straw, a new rice cultivation system is proposed. This system aims to facilitate continuous removal of PFAS from the environment in Asia. Japanese rice cultivation system produces not only rice but also biochar to remove PFAS from water circulation system. The total fluorine content in the tested activated carbon materials ranged from 0.18 to 38 μg g−1 F. Based on the results from background F blank and adsorption capacity, TriporousTM-PFAS-F was shown to be an option to lower the method detection limit for a proposed international standard method for measuring total PFAS.

Comprehensive review of combustion ion chromatography for the analysis of total, adsorbable, and extractable organic fluorine.

Poly- and perfluoroalkyl substances (PFAS) are a class of persistent organic pollutants whose high stability and appreciable water solubility have led to near-global contamination. PFAS are bioaccumulative toxins that have been linked to a myriad of disorders and have been detected nearly universally in human blood. Liquid chromatography-tandem mass spectrometry is the most frequent method used for quantitation, though this typically only measures a few dozen of the >14000 known PFAS and has been shown to account for a small portion of the total organic fluorine present. Sum parameter methods such as total, extractable, and adsorbable organic fluorine have emerged as alternative measurements for PFAS determination. Combustion ion chromatography has become the preferred method for organofluorine measurement where the sorbent or extract containing PFAS is combusted and the emitted hydrofluoric acid (HF) is a measure of the cumulative organofluorine present. Herein we critically review the types of organofluorine measurement, their separation from the sample matrix, and key parameters of the analytical instrument that affect sensitivity, reproducibility, and recovery with regards to PFAS analysis.

The Total Mass of Per- and Polyfluoroalkyl Substances (PFASs) in California Cosmetics.

Cosmetics make up one of the consumer product categories most widely known to contain perfluoroalkyl and polyfluoroalkyl substances (PFASs), including precursors to perfluorooctanoic acid (PFOA) and other perfluoroalkyl acids (PFAAs). Because of the way cosmetics are used, most of the PFASs present in these products are likely to reach wastewater treatment plants (WWTPs), which suggests that cosmetics may contribute significantly to the load of PFOA and other PFASs at WWTPs. However, the majority of PFASs present as intentional ingredients in cosmetics cannot be quantified with the available analytical methods. To address this issue, we developed a methodology to estimate the total PFAS mass in cosmetics as well as the corresponding mass of total organic fluorine and of fluorinated side chains associated with PFAA precursors, using various ingredient databases and ingredient concentrations reported by manufacturers. Our results indicate that the cosmetics sold in California during a one-year period cumulatively contain 650-56 000 kg of total PFASs, 370-37 000 kg of organic fluorine, and 330-20 000 kg of fluorinated side chains associated with PFAA precursors. Among the 16 product subcategories considered, >90% of the PFAS mass came from shaving creams and gels, hair care products, facial cleansers, sun care products, and lotions and moisturizers, while the sum of all nine makeup subcategories accounted for <3%. Comparing our estimates to available WWTP influent data from the San Francisco Bay Area suggests that cosmetics may account for at least 4% of the precursor-derived PFAAs measured in wastewater. As the first study ever to estimate the total mass of PFASs contained in cosmetics sold in California, our results shed light on the significance of certain cosmetics as a source of PFASs to WWTPs and can inform effective source reduction efforts.

Forever Pesticides: A Growing Source of PFAS Contamination in the Environment.

Environmental contamination by fluorinated chemicals, in particular chemicals from the per- and polyfluoroalkyl substances (PFAS) class, has raised concerns around the globe because of documented adverse impacts on human health, wildlife, and ecosystem quality. Recent studies have indicated that pesticide products may contain a variety of chemicals that meet the PFAS definition, including the active pesticide ingredients themselves. Given that pesticides are some of the most widely distributed pollutants across the world, the legacy impacts of PFAS addition into pesticide products could be widespread and have wide-ranging implications on agriculture and food and water contamination, as well as the presence of PFAS in rural environments. The purpose of this commentary is to explore different ways that PFAS can be introduced into pesticide products, the extent of PFAS contamination of pesticide products, and the implications this could have for human and environmental health. We submitted multiple public records requests to state and federal agencies in the United States and Canada and extracted relevant data from those records. We also compiled data from publicly accessible databases for our analyses. We found that the biggest contributor to PFAS in pesticide products was active ingredients and their degradates. Nearly a quarter of all US conventional pesticide active ingredients were organofluorines and 14% were PFAS, and for active ingredients approved in the last 10 y, this had increased to 61% organofluorines and 30% PFAS. Another major contributing source was through PFAS leaching from fluorinated containers into pesticide products. Fluorination of adjuvant products and "inert" ingredients appeared to be limited, although this represents a major knowledge gap. We explored aspects of immunotoxicity, persistence, water contamination, and total fluorine load in the environment and conclude that the recent trend of using fluorinated active ingredients in pesticides may be having effects on chemical toxicity and persistence that are not given adequate oversight in the United States. We recommend a more stringent risk assessment approach for fluorinated pesticides, transparent disclosure of "inert" ingredients on pesticide labels, a complete phase-out of post-mold fluorination of plastic containers, and greater monitoring in the United States. https://doi.org/10.1289/EHP13954.

Identification and quantification of per- and polyfluorinated alkyl substances (PFAS) migrating from food contact materials (FCM)

Per- and polyfluorinated alkyl substances (PFAS) can be added to food contact materials (FCM) to increase their water and/or grease repellent properties. Some well-known PFAS are perfluoroalkyl carboxylic acids (PFCA), perfluoroalkyl sulfonic acids (PFSA), and polyfluorinated telomer alcohols (FTOH). Due to the strength of the carbon-fluorine bond, PFAS are chemically very stable and highly resistant to biological degradation, posing a risk to human health and the environment.To examine the presence of PFAS in paper-based FCM, various samples were collected, including popcorn bags, muffin cups, and pizza boxes with high total organic fluorine (TOF) content from the Danish and Spanish markets. The FCM composition was characterised by FTIR. Quantification of some well-known PFAS such as PFCA, PFSA, and FTOH was performed in food simulants using LC-MS/MS, and in addition a non-targeted screening approach was performed by LC-Orbitrap-HRMS.Among analysed samples, the highest concentrations of PFAS were found in a muffin cup made of cellulose (PFCA ∼ 1.41 μg kg−1 food, FTOH ∼ 11.5 μg kg−1 food), and the results were used to estimate dietary exposures to PFAS migrated from this FCM. Compared to measured TOF value in this sample, the fluorine from all quantified PFAS accounted for only 0.6%. Thus, a more powerful analytical approach was used to further investigate PFAS occurrence in this sample. Using non-targeted screening, an additional twenty compounds were identified, among them five with confidence level 1 and ten with confidence level 2. Many of them were either fluorotelomer carboxylic acids or sulfonic acids or ether-containing compounds.

Are Geotextiles Silent Contributors of Ultrashort Chain PFASs to the Environment?

We investigated the presence of per- and poly fluoroalkyl substances (PFASs) in woven and nonwoven polypropylene geotextiles and four nonwoven polyester geotextiles commonly used in modern geosynthetic composite lining systems for waste containment facilities such as landfills. Targeted analysis for 23 environmentally significant PFAS molecules and methods for examining "PFAS total" concentrations were utilized to assess their occurrence in geotextiles. This analysis showed that most geotextile specimens evaluated in the current investigation contained the ultrashort chain PFAS compound pentafluoropropionic acid (PFPrA). While the concentrations ranged from nondetectable to 10.84 μg/g, the average measured concentrations of PFPrA were higher in polypropylene than in polyester geotextiles. "PFAS total" parameters comprising total fluorine (TF) and total oxidizable precursors (TOPs) indicate that no significant precursor mass nor untargeted intermediates were present in geotextiles. Therefore, this study identified geotextiles as a possible source of ultrashort PFASs in engineered lined waste containment facilities, which may contribute to the overall PFAS total concentrations in leachates or liquors they are in contact with. The findings reported for the first time herein may lead to further implications on the fate and migration of PFASs in geosynthetic composite liners, as previously unidentified concentrations, particularly of ultrashort-chain PFASs, may impact the extent of PFAS migration through and attenuation by constituents of geosynthetic composite liner systems. Given the widespread use of geotextiles in various engineering activities, these findings may have other unknown impacts. The significance of these findings needs to be further elucidated by more extensive studies with larger geotextile sample sizes to allow broader, generalized conclusions to be drawn.

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.

Determination of organic fluorinated compounds content in complex samples through combustion ion chromatography methods: a way to define a “Total Per- and Polyfluoroalkyl Substances (PFAS)” parameter?

Emerging contaminants are a growing concern for scientists and public authorities. The group of per-polyfluoroalkyl substances (PFAS), known as ‘forever chemicals', in complex environmental liquid and solid matrices was analysed in this study. The development of global analytical methods based on combustion ion chromatography (CIC) is expected to provide accurate picture of the overall PFAS contamination level via the determination of extractable organic fluorine (EOF) and adsorbable organic fluorine (AOF). The obtained results may be put into perspective with other methods such as targeted analyses (LC-MS/MS). The impact of pH, the presence of dissolved organic carbon and suspended particles on AOF measurements were explored. The effectiveness of the washing step to remove adsorbed inorganic fluorine (IF) has been proven for samples containing up to 8 mgF.L−1. CIC-based methods showed good repeatability and reproducibility for the complex matrices studied. Environmental applications of these methods have been tested. AOF and EOF analyses could explain between 1 % and 23 % and 0.1 % to 2 % of total organic fluorine (TOF), respectively. The sum of PFAS compounds expressed as fluorine could explain from 0.2 % to 11 % and from 0.003 % to 5 % for AOF and EOF, respectively. These results also suggest that some fluorinated compounds are not adsorbed or extractable and/or lost by volatilisation during the application of AOF and EOF analytical procedure. These findings highlight that AOF and EOF are not entirely efficient as proxy to assess “total PFAS” for assessing environmental contamination by PFAS. However, these methods could still be applied to gain a better understanding of the sources and fate of PFAS in the environment.

Fluorine contamination, mobility, and risks in soils at a phosphate-gypsum waste landfill: a new analytical method and comparison with previous methods.

This study used a new X-ray fluorescence (XRF)-based analytical method with better precision and sensitivity to evaluate the fluorine concentrations in soil. It was hypothesized that the XRF method with a pellet-synthesizing procedure may effectively analyze the fluorine concentrations in soil with ease and reliability. The total fluorine concentrations determined using XRF were compared with those determined using three different types of analytical protocols-incineration/distillation, alkaline fusion, and aqua regia extraction procedures. Among the three procedures, the incineration/distillation procedure did not show reliable precision and reproducibility. In contrast, the total fluorine concentrations determined using the XRF analysis were linearly correlated with those determined using the alkaline fusion and aqua regia extraction procedures. Based on the results of the Korean waste leaching procedure and toxicity characteristics leaching procedure, the leachability of fluorine from soil and waste was not directly related to total fluorine concentrations in soil. Risk assessment also revealed that the fluorine-rich soils did not show non-carcinogenic toxic effects, despite exceeding the regulation level (800mg/kg) in South Korea for total fluorine concentrations in soil. Our results suggest that XRF analysis in combination with the newly developed pretreatment method may be a promising alternative procedure for easily and rapidly determining the total fluorine concentration in soil. However, further efforts are needed to evaluate fluorine leachability and its associated risks in fluorine-contaminated soils.

Identifying PFAS hotspots in surface waters of South Carolina using a new optimized total organic fluorine method and target LC-MS/MS

Per- and polyfluoroalkyl substances (PFAS) are environmental contaminants of concern due to their long persistence in the environment, toxicity, and widespread presence in humans and wildlife. Knowledge regarding the extent of PFAS contamination in the environment is limited due to the need for analytical methods that can reliably quantify all PFAS, since traditional target methods using liquid chromatography (LC)-mass spectrometry (MS) fail to capture many. For a more comprehensive analysis, a total organic fluorine (TOF) method can be used as a screening tool. We combined TOF analysis with target LC-MS/MS analysis to create a statewide PFAS hotspot map for surface waters throughout South Carolina. Thirty-eight of 40 locations sampled contained detectable concentrations of organic fluorine (above 100 ng/L). Of the 33 target PFAS analyzed using LC-MS/MS, the most prevalent were perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA), perfluoroheptanoic acid (PFHpA), and perfluorohexanesulfonate (PFHxS). On average, LC-MS/MS only accounted for 2 % of the TOF measured. Locations with high TOF did not necessarily correlate to high total quantified PFAS concentrations and vice-versa, demonstrating the limitations of target PFAS analysis and indicating that LC-MS may miss highly contaminated sites. Results suggest that future surveys should utilize TOF to more comprehensively capture PFAS in water bodies.

Analysis of per- and polyfluoroalkyl substances (PFAS) in raw materials intended for the production of paper-based food contact materials – evaluating LC-MS/MS versus total fluorine and extractable organic fluorine

Per- and polyfluoroalkyl substances (PFAS) analysis has become crucial due to their presence in the environment, their persistence and potential health risks. These compounds are commonly used in food contact materials (FCM) as a coating to provide water and grease-repellent properties. One of the pathways for PFAS to enter the human body is either through direct consumption of contaminated food or indirectly through migration from FCM into food. The purpose of this study was to investigate where the initial contamination of paper FCM occurs. We analysed paper material consisting of fresh fibre and secondary materials, intended to produce food packaging for the presence of PFAS. The samples were extracted and analysed for 23 different PFAS substances using the targeted approach with LC tandem mass spectrometry (LC-MS/MS). This analytical technique detects specific, easily ionisable PFAS with high sensitivity. However, one drawback of this approach is that it allows the identification of less than 1% of the PFAS known today. For this reason, we used combustion ion chromatography (CIC) to determine the content of extractable organic fluorine compounds (EOF) and compare it to the total fluorine content. The targeted analysis using LC-MS/MS measured an average sum concentration of PFAS of 0.17 ng g−1 sample. Our research shows that the primary PFAS contamination happens during the recycling process since all of the samples in which the targeted PFAS were measured belonged to the secondary material. The most frequently detected analytes were PFOA and PFOS, detected in 90% and 62% of the samples, respectively, followed by PFBS (in 29% of the samples). CIC showed that measured PFAS via LC-MS/MS amount to an average of 2.7 × 10−4% of total fluorine content, whereas the EOF was under the LOD in all of the measured samples. This result highlights the complexity of the accurate determination of PFAS compounds, displaying what kind of information the chosen methods provide.

Fluoride and acid enrichment in coal fire sponges in the Wuda coalfield, Inner Mongolia, Northern China

Coal fire sponges (CFSs) are a type of sponge-like contaminated soil bulge common in coal fire areas. However, the impacts of CFSs on the local environment are not yet understood. Thus, this study investigated soil samples from CFSs in the Wuda coalfield, Inner Mongolia, China, focusing on the acidity, sulfate, and fluorine content. The results showed that the CFSs were highly acidic, with an average pH of 0.76, and contained high levels of SO42− (257.29 × 103 μg/g), total fluorine (TF, 2011.6 μg/g), and water-soluble fluorine (WF, 118.94 μg/g), significantly exceeding those in the regional background soil and indicating that CFSs are a point source of heavy pollution. Soils in the 8000 m2 reclamation zone showed elevated acidity and high SO42− (129.6 × 103 μg/g), TF (1237.8 μg/g), and WF (43.05 μg/g) levels, which was likely the result of the weathering and dissemination of CFS. The CFS samples were rich in hydrogen fluoride, releasing 202.05 ppb of it when heated to 40 °C. Correlation analysis indicated that the acid sulfate soils in CFSs are likely caused by HSO4−/SO42−. Time-of-flight secondary ion mass spectrometry detected four characteristic ions (F−, H3O+, H2SO4+, and HSO4−) in all micro-domains of each sample, indicating that ionic fluorine compounds and sulfuric acid hydrate were found in the CFS samples. Sulfate minerals detected in CFSs included CaSO4, Fe2(SO4)3, CdSO4, NH4HSO4, and Na2SO4. Thus, the results identified CFSs as a transmission channel for contamination, with erosional surface soils as the carrier, for the first time. CFSs pose a serious threat of contamination, albeit over limited areas.