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Cited by 99Per- and polyfluoroalkyl substances researchEnvironmental Chemistry and AnalysisPesticide and Herbicide Environmental Studies

Modelling the sorption behaviour of perfluoroalkyl carboxylates and perfluoroalkane sulfonates in soils

Open access
Fabregat-Palau, Joel, Vidal, Miquel, Rigol, Anna·2021·Science of The Total Environment
DOI 10.1016/j.scitotenv.2021.149343
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Abstract

A simple parametric model was developed to predict the sorption of perfluoroalkyl substances (PFASs) in soils. Initially, sorption and desorption solid-liquid distribution coefficients (Kd and Kd,des respectively) of eight PFASs (five perfluoroalkyl carboxylates, PFCAs, and three perfluoroalkane sulfonates, PFSAs) in seven soils with organic carbon (OC) content ranging from 1.6 to 41% were quantified using batch experiments. The information obtained helped to fill the gaps in a literature-based database of Kd values of PFASs, which was lacking data on soils with high OC content. The overall dataset finally comprised 435 entries. Normalized sorption coefficients for the soil OC and mineral fraction contents (KOC and KMIN respectively) were deduced for each PFAS by correlating the corresponding Kd values obtained under a wide range of experimental conditions with the fraction of organic carbon (fOC) of the soils. Furthermore, the sorption mechanisms in each phase were shown to depend mainly on PFAS chain length. The dependence of KOC and KMIN values on PFAS chain length defined the basic equations to construct the model for predicting PFAS sorption, applicable to both PFCAs and PFSAs with chain lengths ranging from 3 to 11 fluorinated carbons. The validation of the proposed model confirmed its ability to predict the Kd of PFASs based only on the soil OC and silt+clay contents and PFAS chain length. Therefore, it can be used in the first stages of a risk assessment process aiming at estimating the potential mobility of PFASs in soils after a contamination event. This study develops a new parametric model to predict the sorption of perfluoroalkyl substances (PFASs) in soils.

AI snapshot

Written from the paper’s full text.

TL;DR

The paper assembles a 435-entry Kd database for perfluoroalkyl carboxylates and sulfonates in soils and derives a parametric model predicting Kd from PFAS fluorinated carbon number and soil organic carbon and silt+clay content. Sorption increases with chain length, with organic carbon dominating but mineral sites contributing substantially in low-OC soils.

Key findings

  • Short-chained PFASs generally had Kd < 7 L kg⁻¹, mid-chained PFASs ranged from 2 to 295 L kg⁻¹, and the long-chained PFDoA reached the highest values, up to 3082 L kg⁻¹ in the KOM soil.
  • The model uses Kd = KOC·fOC + KMIN·fS+C, with log KOC = 0.41 (±0.04) × number of CF2 − 0.70 (±0.30) (r² = 0.98, p < 0.001) and log KMIN = 0.32 (±0.08) × number of CF2 − 1.70 (±0.60) (r² = 0.89, p < 0.001).
  • For the overall dataset, using PFAS-specific KOC and KMIN values gave log Kd,model = 0.92 (±0.05) × log Kd,exp (r² = 0.78, p < 0.001, n = 353), RMSE = 0.37, RPD = 1.94; external validation gave log Kd,model = 0.9 (±0.1) × log Kd,exp (r² = 0.76, p < 0.001, n = 121, RMSE = 0.40, RPD = 1.88).
  • Mineral-site contribution was ≤3% of Kd for all PFASs in soils with OC > 10%, but in soils with OC < 2% it ranged from 20–95% for PFBS, 3–93% for PFOA, 3–90% for PFOS, and 12–13% for PFDoA.

Methods

  • Batch sorption and desorption experiments were performed with seven topsoils (0–10 cm) spanning OC 1.6–41%, using 0.01 mol L⁻¹ CaCl₂ with NaN₃, 24 h shaking, duplicate samples, and LC-MS/MS quantification.
  • Two Kd datasets were built: 56 entries from the authors’ experiments and 435 entries overall, including literature batch data for PFCAs and PFSAs with 3–11 fluorinated carbons.
  • KOC and KMIN were derived from Kd versus fOC relationships, correlated with CF2 number, and combined into a parametric Kd model; external validation used a Kennard–Stone split of two-thirds calibration and one-third validation data.

Limitations

  • Stated: the model is not intended to derive very accurate Kd values; scattering occurs for low-sorption scenarios; it is unclear how it performs for PFAS species other than PFCAs/PFSAs with 3–11 fluorinated carbons; adding more soil properties would increase complexity without enhancing its range of applications; literature data carry intrinsic variability; desorption data were scarce, so subsequent analyses focused only on sorption.
  • Evident from the text: the authors’ experimental dataset is limited to seven soils and eight PFASs, and the overall literature dataset has limited entries for some PFASs such as PFDS, PFPeA, and PFHpA, with only 10 literature samples having OC > 10%.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

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Crossref · 10.1016/j.scitotenv.2021.149343

Cites

39 of 40 references verified0 citation errors · 1 not checkable

Statistics

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Claims the paper makes

0 of 41 cited sources checked · 0 supported · 0 flagged

  • Findingown data

    The contribution of organic and mineral phases to PFAS sorption was quantified.

    “The contribution of organic and mineral phases to PFAS sorption was quantified.”
    Quote in the paperSubstantial claim
  • Findingreasoning

    PFOS had higher Kd values than PFNA despite having the same number of CF2.

    “Despite having the same CF 2 , PFOS had higher K d values than PFNA”
    Quote in the paperSubstantial claim
  • Findingcitation

    Short-chained PFASs (PFBA, PFBS, PFHxA) generally had Kd values below 7 L/kg, regardless of soil characteristics or PFAS functional group.

    “Short-chained PFASs (PFBA, PFBS and PFHxA) generally had K d values below 7 L kg -1 , regardless of the soil characteristics or the PFAS functional group”
    Quote in the paperSubstantial claim
  • Findingown data

    Mid-chained PFASs (PFHxS, PFOA, PFOS, PFNA) had Kd values ranging from 2 to 295 L/kg depending on PFAS and soil characteristics.

    “mid-chained PFASs (PFHxS, PFOA, PFOS and PFNA) had higher K d values ranging from 2 to 295 L kg -1 depending on the PFAS and the soil characteristics”
    Quote in the paperSubstantial claim
  • Findingnone given

    A parametric sorption model was designed to predict the Kd of PFASs in soils.

    “A parametric sorption model was designed to predict the K d of PFASs in soils.”
    Quote in the paperSubstantial claim
  • May combine two claims. 26
  • Classified as probably not a substantial claim. 24

  • May combine two claims.

    Findingown data

    Kd,des values were higher than corresponding Kd values for sorption, and the hysteresis coefficient (Kd,des/Kd) was larger than one in all cases.

    “The K d,des values obtained are reported in Table S5 and were higher than the corresponding K d values for sorption.The hysteresis coefficient, calculated as the ratio between K d,des and K d , was therefore larger than one in all cases.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Of the 222 samples obtained from literature references, 167 were soils, 171 had OC <2%, and only 10 had OC >10%.

    “Of the 222 samples obtained from these references, 167 were soils, 171 had an OC content less than 2%, and only 10 had an OC content greater than 10%.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    PFOS and PFOA were the two PFASs with the highest number of entries in the literature dataset, while limited data were available for other PFASs including PFDS, PFPeA and PFHpA.

    “PFOS and PFOA were the two PFASs with the highest number of entries, whereas limited data were available in the literature for other PFASs, including PFDS, PFPeA and PFHpA.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Findingnone given

    KOC and KMIN normalized sorption coefficients of PFASs were calculated.

    “K OC and K MIN normalized sorption coefficients of PFASs were calculated.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Findingown data

    The overall dataset comprised 435 entries, while the experimental dataset consisted of 56 entries.

    “Our experimental dataset consisted of 56 entries, while the overall dataset (which also included our experimental data) comprised 435 entries.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingcitation

    Sorption Kd values for mid-chained PFHxS, PFOA and PFOS in this study were comparable to previously reported values and were higher than corresponding short-chain PFASs.

    “The sorption K d values for the mid-chained PFHxS, PFOA and PFOS in this study were comparable to previously reported values (Higgins and Luthy, 2006;Oliver et al., 2020) and were higher than the corresponding short-chain PFASs”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites Higgins and Luthy, 2006 source

      Not checked in the free run.

    • cites Oliver et al., 2020 source

      Not checked in the free run.

  • May combine two claims.

    Findingown data

    The long-chained PFAS PFDoA had the highest Kd values among the PFASs tested, with a high Kd even for the low OC ALM soil.

    “The long-chained PFAS, PFDoA, had the highest K d values among the PFASs tested, with a high K d even for the low OC ALM soil”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingnone given

    Sorption in low OC soils (exemplified by ALM soil) was lower than in the rest of soils, and in general Kd increased with OC content.

    “Sorption in low OC soils, as exemplified by the ALM soil, was lower than in the rest of soils, and in general, K d increased with OC content.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The seven field soil samples had OC content ranging from 1.6 to 41%, with four samples above 25%.

    “The OC content of the soil samples ranged from 1.6 to 41%; four samples having an OC content above 25%.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    The correlations between KOC/KMIN and number of CF2 were significant, and both slope and y-intercept were comparable between datasets.

    “The correlations were significant, and both the slope and the yintercept were comparable between datasets.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    For PFOS and PFOA, the KMIN values derived from the overall dataset were 9.4 and 3.3, respectively.

    “For the mid-chained PFOS and PFOA, two of the most frequently studied PFAS, the K MIN values that we derived from the overall dataset were 9.4 and 3.3 respectively.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The predictive accuracy for the model was quite satisfactory both for our experimental data and for the overall dataset.

    “The predictive accuracy for the model was quite satisfactory both for our experimental data and for the overall dataset (see Fig. 2a and b).”
    Quote in the paperSubstantial claim
    • The authors state this as an assumption: PFAS sorption in soils can be modelled as the sum of independent contributions from organic carbon and mineral (silt+clay) phases.
    • The authors state this as an assumption: The sorption affinity of PFCAs and PFSAs can be described by the number of CF2 groups.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Findingreasoning

    Scattering of data is observed for scenarios with low sorption.

    “In Fig. 2b some scattering of the data is observed for scenarios with low sorption”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    Only data for PFCAs and PFSAs containing 3 to 11 fluorinated carbons were included.

    “In addition, we only included data for PFCAs and PFSAs that contained from 3 to 11 fluorinated carbons.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductown data

    The pH of supernatants from sorption and desorption experiments did not differ by more than ±0.2 from the soil pH.

    “The pH of the resulting supernatants from sorption and desorption experiments did not differ (±0.2) from the soil pH reported in Table 1.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Study design and conductown data

    All sorption and desorption batch experiments were performed in duplicate, with relative standard deviation between replicates approximately 20% in the worst scenarios.

    “All sorption and desorption batch experiments were performed in duplicate.The relative standard deviation between replicates was approximately 20% in the worst scenarios.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    The mineral phase may have a positive influence on PFAS sorption in low OC soils (<5%).

    “studies exploring the sorption of PFASs on low OC soils (< 5%) have suggested that the mineral phase may have a positive influence on the sorption process (Knight et al., 2019;Martz et al., 2019).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Knight et al., 2019

      Not checked in the free run.

    • cites Martz et al., 2019

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Knight et al. (2019) developed a model based on OC and soil silt and clay content that predicts PFOA sorption in soils with OC 0.1-3.5%, excluding organic soils.

    “Knight et al. (2019) developed a model based on OC and soil silt and clay content, able to predict the sorption of PFOA under selected experimental conditions in soils with OC content ranging from 0.1-3.5%,thus excluding organic soils.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Knight et al. (2019)

      Not checked in the free run.

  • May combine two claims.

    Interpretationown data

    Mid-chained PFASs have higher sorption affinity in the examined soils and therefore lower potential mobility.

    “indicating higher sorption affinity in the soils examined and therefore lower potential mobility.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim.

    Study design and conductnone given

    Only studies where a Kd value could be confidently derived (linear isotherms, or non-linear with Kd in linear range, or from low initial concentration assuming no sorption saturation) were considered.

    “Only studies in which a K d value could be confidently derived (i.e., linear isotherms with constant K d ; non-linear isotherms, but with the reported K d falling within the linear range of the isotherm; or K d values calculated from a low initial concentration, assuming that sorption saturation was not reached) were considered.”
    Quote in the paperSubstantial claim
    • The authors state this as an assumption: For Kd values calculated from a low initial concentration, sorption saturation was not reached.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    A mechanistic model was developed to predict sorption of PFCAs, PFSAs, and linear alkylbenzenes in sediments with OC 0.6-9.7% via electrostatic and hydrophobic interactions with organic matter.

    “a mechanistic model was developed to predict the sorption of PFCAs, PFSAs, and linear alkylbenzenes in sediments with OC ranging from 0.6 to 9.7% via both electrostatic and hydrophobic interactions with the organic matter (Higgins and Luthy, 2007).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Higgins and Luthy, 2007

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Soil organic carbon content is the main parameter affecting the sorption behaviour of PFASs in sediments, with most sorption occurring via hydrophobic interactions.

    “Higgins and Luthy (2006) found that soil OC content was the main parameter affecting the sorption behaviour of PFASs in sediments, suggesting that most sorption occurred via hydrophobic interactions”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Higgins and Luthy (2006) source

      Not checked in the free run.

  • May combine two claims.

    Study design and conductown data

    Aqueous control samples showed negligible losses for all PFASs except PFDoA, for which only 40% was recovered and results were corrected accordingly.

    “Regarding aqueous control samples, negligible losses for all the PFASs were observed, except for PFDoA (see Section S1).”
    • Also stated in: § 2.4. Quality control · plain
      “However, for the long-chained PFDoA only 40% was recovered, and the results were corrected accordingly.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim. May combine two claims.

    Premisecitation

    OC alone cannot satisfactorily account for PFAS sorption, and other parameters such as soil pH and clay content should also be considered.

    “A literature review evaluating the role of soil and sediment properties in the sorption of PFASs concluded that OC alone could not satisfactorily account for the sorption of PFASs and suggested that other parameters, such as soil pH and clay content, should also be considered (Li et al., 2018).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Li et al., 2018

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S2 (checkable). May combine two claims.

    Premisecitation

    New experimental data are required to improve current sorption models, making them less site-specific and covering a wide variety of PFASs including short-chained species.

    “Therefore, new experimental data to derive PFAS sorption parameters in a diversity of soil types are required to improve current sorption models, making them less site-specific and covering a wide variety of PFASs, including the least commonly regulated species (especially shortchained PFASs) (Sima and Jaffé, 2021).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Sima and Jaffé, 2021 source

      Not checked in the free run.

  • May combine two claims.

    Study design and conductcitation

    Equilibrium was reached after 24 h of shaking, in accordance with previous kinetic studies.

    “After being spiked with a PFAS, tubes were shaken again at 60 rpm for 24 h to ensure that the equilibrium was reached in accordance with previous kinetic studies (Li et al., 2019;Mejia-Avendaño et al., 2020;Miao et al., 2017;Wei et al., 2017;Xiang et al., 2018;Zhi and Liu, 2018).”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites Li et al., 2019

      Not checked in the free run.

    • cites Mejia-Avendaño et al., 2020

      Not checked in the free run.

    • cites Miao et al., 2017

      Not checked in the free run.

  • May combine two claims.

    Interpretationcitation

    Short-chained PFASs have low sorption affinity in soils and potentially high mobility.

    “indicating their low sorption affinity in soils and their potentially high mobility (Gellrich et al., 2012).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Gellrich et al., 2012 source

      Not checked in the free run.

  • May combine two claims.

    Study design and conductcitation

    Kd values from the literature were included only if they originated from batch experiments, because in situ Kd values are significantly higher due to non-equilibrium nature of natural systems.

    “K d values from the literature were only included in the data if they originated from batch experiments, given that K d values obtained from in situ experiments have been shown to be significantly higher due to the non-equilibrium nature of natural systems (Li et al., 2018).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Li et al., 2018

      Not checked in the free run.

  • May combine two claims.

    Premisenone given

    Sorption patterns in prior work were deduced mainly from PFOS and PFOA, with limited sorption data for other shorter or longer-chained PFASs in soils and sediments.

    “In addition, the sorption pattern was deduced from the widely-evaluated PFASs perfluorosulfonic acid (PFOS) and perfluorooctanoic acid (PFOA), while only limited sorption data are available for other shorter or longer-chained PFASs in soils and sediments.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationown data

    Both sorption of PFASs in the mineral and organic phases of the soil become more favourable as the PFAS chain length increases.

    “Overall, these results suggest that both sorption of the PFASs in the mineral and organic phases of the soil become more favourable as the PFAS chain length increases.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    The scattering for low sorption scenarios is likely attributable to weak interaction between PFAS and the solid phase and intrinsic variability due to literature-assembled data.

    “likely attributable to the weak interaction between PFAS and the solid phase, in addition to the intrinsic variability due to the use of literature-assembled data.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Interpretationown data

    The model should not be used for attempting to derive very accurate K_d values of PFASs in soils.

    “Nevertheless, according to the RPD values derived from the predictions of the overall dataset, we warn against the use of the model for attempting to derive very accurate K d values of PFASs in soils.”
    Quote in the paperSubstantial claim
    • The authors state this as an assumption: PFAS sorption in soils can be modelled as the sum of independent contributions from organic carbon and mineral (silt+clay) phases.
    • The authors state this as an assumption: The sorption affinity of PFCAs and PFSAs can be described by the number of CF2 groups.

  • May combine two claims.

    Premisecitation

    Experiments testing sorption of PFASs on humic acids extracted from soils have shown that hydrophilic contributions are not predominant, confirming that hydrophobic interactions are the main sorption mechanism.

    “However, experiments testing the sorption of PFASs on humic acids extracted from soils have shown that these hydrophilic contributions are not predominant, thus confirming that hydrophobic interactions are the main sorption mechanism (Xiang et al., 2018;Zhao et al., 2014).”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites Xiang et al., 2018

      Not checked in the free run.

    • cites Zhao et al., 2014

      Not checked in the free run.

  • Classified as probably not a substantial claim. May combine two claims.

    Premisecitation

    Soil OC, clay content, and pH all have a significant effect on the K_d of PFASs.

    “Based on a multiple regression analysis, Li et al. concluded that soil OC, clay content, and pH all have a significant effect on the K d of PFASs (Li et al., 2018).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Li et al., 2018

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Adsorption enthalpy is stabilized in the presence of cations.

    “Moreover, recent computational studies have identified the hydrophobic patches of montmorillonite clay as the primary adsorption domains and the stabilization of adsorption enthalpy in the presence of cations (Willemsen and Bourg, 2021).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Willemsen and Bourg, 2021

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Wang and co-workers derived silt+clay normalized sorption coefficients using a three-compartment distribution model to account for the contribution of the mineral fraction to the overall K_d.

    “Indeed, Wang and co-workers derived silt+clay normalized sorption coefficients using a three-compartment distribution model to account for the contribution of the mineral fraction to the overall K d (Wang et al., 2021).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Wang et al., 2021 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Hydrophobic patches of montmorillonite clay are the primary adsorption domains.

    “Moreover, recent computational studies have identified the hydrophobic patches of montmorillonite clay as the primary adsorption domains and the stabilization of adsorption enthalpy in the presence of cations (Willemsen and Bourg, 2021).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Willemsen and Bourg, 2021

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    OC and the mineral silt and clay fractions contributed significantly to the sorption of PFOA in a large number of mineral soils.

    “Similarly, Knight et al. found that OC and the mineral silt and clay fractions contributed significantly to the sorption of PFOA in a large number of mineral soils (Knight et al., 2019).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Knight et al., 2019

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    The presence of calcium has positive effects on the K_d of PFASs.

    “which may explain the positive effects of the presence of calcium on the K d of PFASs (Higgins and Luthy, 2006)”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Higgins and Luthy, 2006 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Silt and clay fractions have a positive effect on the K_d of PFOS, PFOA and PFHxS in sediments.

    “The silt and clay fractions have also been reported to have a positive effect on the K d of PFOS, PFOA and PFHxS in sediments (Oliver et al., 2020)”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Oliver et al., 2020 source

      Not checked in the free run.

  • Classified as probably not a substantial claim. May combine two claims.

    Premisecitation

    Iron, aluminium and titanium oxides can interact with PFASs and participate in PFAS sorption.

    “iron, aluminium and titanium oxides have all been reported to be able to interact with PFASs and to participate in PFAS sorption (Lu et al., 2016).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Lu et al., 2016

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Humic substances often possess hydrophilic moieties that can interact with PFASs through mechanisms such as hydrogen bonding or divalent cation bridging.

    “Humic substances, which are the main organic compounds present in the soil organic phase, often possess hydrophilic moieties that can also interact with PFASs through mechanisms such as hydrogen bonding or divalent cation bridging (Du et al., 2014).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Du et al., 2014

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing).

    Interpretationreasoning

    This information may be relevant for an early evaluation of contamination events.

    “This information may be relevant for an early evaluation of contamination events.”
    Quote in the paperNot a substantial claim
43 of 43

  • The authors state this as an assumption.

    For Kd values calculated from a low initial concentration, sorption saturation was not reached.

    “or K d values calculated from a low initial concentration, assuming that sorption saturation was not reached”

  • The authors state this as an assumption.

    PFAS sorption in soils can be modelled as the sum of independent contributions from organic carbon and mineral (silt+clay) phases.

    “Therefore, the K d of PFASs was further modelled from a separate contribution of the organic and mineral phases (K d,ORG and K d,MIN respectively), regardless of the f OC value: K d ¼ K OC f OC þ K MIN f MINð11Þ”

  • The authors state this as an assumption.

    The sorption affinity of PFCAs and PFSAs can be described by the number of CF2 groups.

    “To develop a parametric model to predict the sorption of PFCAs and PFSAs in soils based only on the number of CF 2 of PFASs and on a few physicochemical properties of the soil, we used the correlations presented in Eqs. ( 9) and ( 10) as descriptors of the sorption on the OC and mineral pool sites respectively.”
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Authors
Fabregat-Palau, J., Vidal, M., & Rigol, A.
Affiliations
Universitat de Barcelona (ES)
Corresponding author
Rigol, Anna
ORCID
Venue
Science of The Total Environment
Publisher
Elsevier BV
Published
2021-12
Volume
801
Pages
149343
ISSN
0048-9697 (ISSN-L)
DOI
10.1016/j.scitotenv.2021.149343
OpenAlex
W3188954002
Cited by
99
References
39
Citations by year
2026: 31 · 2025: 22 · 2024: 16 · 2023: 15 · 2022: 14 · 2021: 1
FWCI
4.34
Type
journal article
Language
en
Open access
Licence
Locations
  • The Science of The Total Environment (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • Dipòsit Digital de la Universitat de Barcelona (Universitat de Barcelona) (submittedVersion, cc-by-nc-nd)
Funders
Gobierno de España Ministerio de Ciencia e Innovación
Topics
  • Physical Sciences › Environmental Science › Environmental Chemistry › Per- and polyfluoroalkyl substances research
  • Physical Sciences › Environmental Science › Environmental Chemistry › Environmental Chemistry and Analysis
  • Physical Sciences › Environmental Science › Pollution › Pesticide and Herbicide Environmental Studies
Keywords
perfluoroalkyl carboxylates, PFAS sorption, distribution coefficient, organic carbon content, mineral fraction, chain length dependence, desorption, risk assessment
MeSH terms
Alkanesulfonates, Carboxylic Acids, Fluorocarbons, Soil, Soil Pollutants

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

Claims read by deepseek-v4.1-flash under definition version 3 (extract-v3) on 2026-10-06.

Classified by jev-1.13-20260917 (gold-guideline-v0.2) on 2026-10-06.

Statistics and arithmetic are recomputed, not judged.

Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.

What counts as a claim ›How we measure confidence ›How we check this ›

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