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Cited by 55Per- and polyfluoroalkyl substances researchGroundwater flow and contamination studiesEnvironmental remediation with nanomaterials

The DOI matches its Crossref record; 54 of the 54 references it cites were found in a registry or an index; 24 of the 63 sources its claims cite were checked for support.

Contribution of Nonaqueous-Phase Liquids to the Retention and Transport of Per and Polyfluoroalkyl Substances (PFAS) in Porous Media

Open access
Van Glubt, Sarah, Brusseau, Mark L.·2021·Environmental Science & Technology
DOI 10.1021/acs.est.0c07355PMC PMC8634874
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Abstract

Per and polyfluoroalkyl substances (PFAS) cocontamination with nonaqueous-phase organic liquids (NAPLs) has been observed or suspected at various sites, particularly at fire-training areas at which aqueous film-forming foams (AFFFs) were applied. The objectives of this study are to (1) delineate the relative significance of specific PFAS-NAPL processes on PFAS retention, including partitioning into the bulk NAPL phase and adsorption to the NAPL-water interface; (2) investigate the influence of NAPL properties, saturation, and mass-transfer constraints on PFAS retention; and (3) determine whether PFAS may impact NAPL distribution through mobilization or dissolution. Perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) are used as representative PFAS, and trichloroethene (TCE) and decane are used as representative NAPLs. NAPL-water interfacial adsorption was quantified with NAPL-water interfacial-tension measurements; partitioning into NAPL was quantified with batch experiments, and retardation factors (R) in the absence and presence of residual NAPL were determined with miscible-displacement transport experiments. R values increased in the presence of residual NAPL, with adsorption to the NAPL-water interface accounting for as much as ∼77% of retention and solid-phase adsorption also significantly contributing to retention. Additionally, this study provides the first QSPR analysis focused on NAPL-water interfacial adsorption coefficients, with results consistent with those from previous air-water studies. Lastly, this initial investigation into PFAS impacts on NAPL behavior determined that PFOS/PFOA are unlikely to enhance solubilization or mobilization of NAPL under the conditions present at many AFFF legacy sites.

Overview

AI snapshot

Written from the paper’s full text.

TL;DR

This study quantified how non-aqueous phase liquids (NAPLs) increase PFAS retention in porous media, showing that NAPL-water interfacial adsorption is often the dominant additional retention process while bulk NAPL partitioning is minor. It also found that PFOS/PFOA are unlikely to enhance NAPL solubilization or mobilization except at very high PFAS concentrations.

Key findings

  • NAPL-water interfacial adsorption accounted for as much as ~77% of PFAS retention in PFOS experiments with residual NAPL; solid-phase sorption contributed 22–48%, while bulk NAPL partitioning contributed <1% to ~3% for PFOS experiments (19% for PFOA with residual TCE).
  • Retardation factors increased with residual NAPL: PFOS R was 2.5 and 3.3 for TCE at Sn = 0.28 and 0.42, and 2.6 and 4.0 for decane at Sn = 0.29 and 0.54, versus R = 1.3 with no NAPL; PFOA R was 1.5 with residual TCE at Sn = 0.31.
  • Measured NAPL-water interfacial adsorption coefficients (Ki) were 0.0050 cm (0.01 M NaCl) and 0.0056 cm (SGW) for PFOS with TCE, 0.0038 cm and 0.0070 cm for PFOS with decane, and 0.0003 cm for PFOA with TCE; PFPeA was another order of magnitude smaller.
  • PFOS increased TCE aqueous solubility by ~35% at 100 and 500 mg/L (mean ~1550 mg/L vs ~1150 mg/L for controls), but no enhanced solubilization occurred at 0.1, 1, or 10 mg/L; no free-phase TCE mobilization was observed, with NT ≈ 5.6×10−6, below the mobilization threshold of 2×10−5 to 5×10−5.

Methods

  • Interfacial tensions were measured with a Du Nouy ring tensiometer for PFOS, PFOA, and PFPeA against TCE or decane; literature interfacial-tension data were digitized to build a NAPL-water adsorption database.
  • Batch experiments measured PFAS partitioning into bulk NAPL at initial PFOS/PFOA concentrations of 2, 20, and 200 mg/L; miscible-displacement column experiments measured transport with a nonreactive tracer and PFOS/PFOA in the absence and presence of residual TCE or decane, at two NAPL saturations and two pore-water velocities.
  • PFOS/PFOA were analyzed by the methylene blue active substances assay, and tracer/TCE by UV-Vis; a QSPR analysis used molar volume as the single molecular descriptor, and retention contributions were evaluated with the comprehensive retention model equations provided in the SI.

Limitations

  • The paper states that batch NAPL-partitioning experiments should be considered semi-quantitative because of large uncertainty, with 95% confidence intervals for almost all Kn measurements encompassing 0.
  • The paper states that higher-NAPL-saturation column Ki values were smaller than interfacial-tension-derived values, possibly due to hydraulic inaccessibility of NAPL-water interfaces, and that further investigation is needed; predicted R values also exceeded measured values at higher NAPL saturations.
  • The paper states that mobilization experiments used two-phase systems and TCE as a single-component NAPL, whereas three-phase systems and multi-component NAPL mixtures may behave differently; the text also makes evident that the study used quartz sand, limited PFAS (PFOS, PFOA, PFPeA), and limited NAPLs (TCE, decane).

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

Integrity signals

Registry

Crossref · 10.1021/acs.est.0c07355

Cites

54 of 54 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Verification

Claims the paper makes

24 of 63 cited sources checked · 19 supported · 1 flagged · accuracy not yet measured

  • Interpretationcitation

    The comprehensive retention model developed by Brusseau and colleagues was demonstrated to provide good predictions of the measured data sets.

    “The comprehensive retention model developed by Brusseau and colleagues was demonstrated to provide good predictions of the measured data sets.”
    Quote in the paperNot a substantial claim2 of 2 sources checked
    • cites [22] source
    • cites [29] source

      Section 3 (Comprehensive Retention Model; page not provided) says the conceptual approach had been validated for individual retention processes in prior work, but had not been tested specifically for PFAS. Section 6 (Conclusion; page not provided) describes an assessment for a representative, idealized system, not a demonstration that the comprehensive model predicted measured data sets well. (LLM, conf=0.88)

      Checked by a reasoning model — may be wrong.

      Experimental — accuracy not yet measured
  • Premisecitation

    NAPL-water interfacial area increases as water saturation decreases.

    “Previous studies have established that the NAPL-water interfacial area increases as water saturation decreases.42–45”
    Quote in the paperSubstantial claim3 of 4 sources checked
    • cites [42] source
    • cites [43] source
    • cites [44] source
    • cites [45] source
  • Findingcitation

    PFOS transport exhibits greater retardation in the presence of decane NAPL compared to no NAPL.

    “Similarly, PFOS transport exhibits greater retardation in the presence of decane NAPL compared to no NAPL.22”
    Quote in the paperSubstantial claim1 of 1 sources checked
  • Interpretationreasoning

    The results from both studies are consistent with the comprehensive retention model proposed by Brusseau and colleagues.

    “Notably, the results from both studies are consistent with the comprehensive retention model proposed by Brusseau and colleagues.22,29”
    Quote in the paperSubstantial claim2 of 2 sources checked
  • Interpretationown data

    The observed retardation and transport behavior is consistent with the comprehensive retention model proposed by Brusseau and colleagues.

    “In addition, this demonstrates that the observed retardation and transport behavior is consistent with the comprehensive retention model proposed by Brusseau and colleagues.22,29”
    Quote in the paperSubstantial claim2 of 2 sources checked
  • Probably not a substantial claim. 21
  • It may state two separate claims as one. 40

  • Probably not a substantial claim. The paper’s conclusions may not depend on it.

    Premisecitation

    Soil concentrations of up to about 400 mg/kg have been reported for PFOS in a recent meta-analysis.

    “Soil concentrations of up to ~400 mg/kg, for example, were reported for PFOS in a recent meta-analysis.14”
    Quote in the paperNot a substantial claim1 of 1 sources checked

  • It may state two separate claims as one.

    Premisecitation

    Adsorption of surfactants at fluid-fluid interfaces is inherently nonlinear, which results in Ki being a function of the aqueous surfactant concentration.

    “Adsorption of surfactants at fluid-fluid interfaces is inherently nonlinear, which results in Ki being a function of the aqueous surfactant concentration.”
    Quote in the paperSubstantial claim1 of 2 sources checked
    • cites [34] source
    • cites [37] source

      Checked before — its earlier verdict is held back until a new check runs.

  • It may state two separate claims as one.

    Premisecitation

    Additional retention processes may occur in NAPL-contaminated source zones, including partitioning into bulk NAPL and adsorption at NAPL-water interfaces.

    “However, additional retention processes may occur in NAPL-contaminated source zones, including partitioning into bulk NAPL and adsorption at NAPL-water interfaces.22,27–29”
    Quote in the paperSubstantial claim2 of 4 sources checked
    • cites [22] source
    • cites [27] source
    • cites [28] source
    • cites [29] source

  • Probably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.

    Premisecitation

    Two proposed mechanisms for solubilization observed below the surfactant CMC are the reduction in NAPL-water interfacial tension and the formation of pre-micellar aggregates.

    “Two proposed mechanisms for solubilization observed below the surfactant CMC are the reduction in NAPL-water interfacial tension and the formation of pre-micellar aggregates (e.g., refs 51–54).”
    Quote in the paperNot a substantial claim3 of 4 sources checked
    • cites [51] source

      The introduction proposes reduced surface and interfacial tension as a mechanism for increased aqueous dispersion, and the Discussion links dispersion at low rhamnolipid concentrations to falling surface tension. It does not propose pre-micellar aggregates as the other below-CMC mechanism: it attributes that effect to interactions with surfactant monomers and places aggregate-mediated dispersion above the CMC. Page numbers are unavailable in our copy. (LLM, conf=0.88)

      Experimental — accuracy not yet measured
    • cites [52] source
    • cites [53] source

      The Conclusion and Results and discussion §4.4 attribute sub-CMC hexadecane solubilization to aggregate formation. Results and discussion §4.1 also documents reduced hexadecane–water interfacial tension as surfactant concentration rises, but the paper does not propose that reduction as a separate mechanism for the observed solubilization. (LLM, conf=0.85)

      Experimental — accuracy not yet measured
    • cites [54] source

  • Probably not a substantial claim. The paper’s conclusions may not depend on it.

    Premisecitation

    In other studies, solubilization was also observed when surfactant concentrations were below the CMC.

    “Conversely, in other studies solubilization was also observed when surfactant concentrations were below the CMC (e.g., refs 50–54).”
    Quote in the paperNot a substantial claim3 of 5 sources checked
    • cites [50] source
    • cites [51] source
    • cites [52] source
    • cites [53] source
    • cites [54] source

  • Probably not a substantial claim. The paper’s conclusions may not depend on it.

    Premisecitation

    Many studies have observed increased NAPL solubilization in the presence of surfactants.

    “Many studies have observed increased NAPL solubilization in the presence of surfactants.”
    Quote in the paperNot a substantial claim4 of 8 sources checked
    • cites [47] source
    • cites [48] source
    • cites [49] source

      The Abstract reports that surfactants solubilize hydrophobic dyes, and Section 8 discusses their solubilization of hydrophobic substances more broadly. The paper does not report that many studies observed increased solubilization of NAPLs specifically; its stated focus is dyes, not NAPLs. (LLM, conf=0.83)

      Experimental — accuracy not yet measured
    • cites [50] source
    • cites [51] source

      The Results report that rhamnolipid greatly increased the aqueous dispersion of octadecane, supporting the general surfactant effect. But the paper studied octadecane as a solid at 23°C, not a non-aqueous-phase liquid (NAPL), and its experiment does not establish that many studies observed NAPL solubilization. (LLM, conf=0.87)

      Experimental — accuracy not yet measured
    • cites [52] source
    • cites [53] source
    • cites [54] source

  • It may state two separate claims as one.

    Findingcitation

    Kn values reported by Guelfo and Higgins follow the same trends observed in the present study: Kn values for PFOS or PFOA with TCE are greater than with decane or dodecane, and Kn for PFOA with a given NAPL is greater than for PFOS.

    “The Kn values reported by Guelfo and Higgins27 follow the same trends observed in the present study, where the Kn values for PFOS or PFOA with TCE are greater than with decane or dodecane, and the Kn for PFOA with a given NAPL is greater than for PFOS.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Guelfo and Higgins27

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • It may state two separate claims as one.

    Findingreasoning

    Ki values are greater for SGW solutions compared to 0.01 M NaCl solutions although both solutions have the same ionic strength.

    “The Ki values are greater for the SGW solutions compared to the 0.01 M NaCl solutions, although both solutions have the same ionic strength.”
    Quote in the paperNot a substantial claim

  • It may state two separate claims as one.

    Findingreasoning

    The TCE-water Ki value for PFOA is 0.0003 cm, an order of magnitude smaller than the TCE-water Ki value for PFOS.

    “The TCE-water Ki value for PFOA is 0.0003 cm, which is an order of magnitude smaller than the TCE-water Ki value for PFOS.”
    Quote in the paperNot a substantial claim

  • It may state two separate claims as one.

    Findingown data

    The PFOS TCE-water Ki values are 0.0050 cm for 0.01 M NaCl and 0.0056 cm for SGW.

    “The PFOS TCE-water Ki values for the 0.01 M NaCl and SGW solutions are 0.0050 cm and 0.0056 cm, respectively.”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Findingown data

    Mean Kn values reported by Guelfo and Higgins and McKenzie et al. are greater than those reported in the present study, but nearly all data sets have overlapping 95% confidence intervals.

    “While the mean values reported by Guelfo and Higgins27 and McKenzie et al.28 are greater than those reported in the present study, nearly all data sets have overlapping 95% confidence intervals.”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Guelfo and Higgins27

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites McKenzie et al. [28] source

  • It may state two separate claims as one.

    Findingown data

    The PFOS decane-water Ki values are 0.0038 cm for 0.01 M NaCl and 0.0070 cm for SGW.

    “The PFOS decane-water Ki values are 0.0038 cm and 0.0070 cm for 0.01 M NaCl and SGW, respectively.”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Findingown data

    BTCs for transport of the nonreactive tracer in packed columns containing no residual NAPL are ideal, with sharp arrival and elution waves and retardation factors of 1.

    “BTCs for transport of the nonreactive tracer in packed columns containing no residual NAPL are observed to be ideal, with sharp arrival and elution waves and retardation factors of 1 (see Figures 3 and S1).”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Findingreasoning

    The R value for PFOA transport in the presence of residual TCE is 1.5 for Sn = 0.31, which is smaller than the R value for PFOS with residual TCE of similar saturation.

    “The R value for PFOA transport in the presence of residual TCE is 1.5 for a Sn = 0.31, which is smaller than the R value for PFOS with residual TCE of similar saturation.”
    Quote in the paperNot a substantial claim

  • It may state two separate claims as one.

    Findingown data

    The Kn value for PFOS with TCE is 0.11, while the Kn value for PFOS with decane is 0.02, an order of magnitude lower, although the 95% confidence intervals overlap.

    “The Kn value determined from batch experiments for PFOS with TCE is 0.11, while the Kn value for PFOS with decane is 0.02, an order of magnitude lower, although the 95% confidence intervals overlap.”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Findingown data

    The R value measured for PFOS transport in the fully water-saturated system with no NAPL present is 1.3, with Kd = 0.064 cm3/g.

    “The R value measured for PFOS transport in the fully water-saturated system (no NAPL present) is 1.3 (Kd = 0.064 cm3/g).”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Findingown data

    The Ki value determined for the lower-velocity transport experiment is similar to the value determined for the higher-velocity experiments, and both are similar to the value determined from the interfacial-tension data.

    “The Ki value determined for the lower-velocity experiment is similar to the value determined for the higher-velocity experiments, and both are similar to the value determined from the interfacial-tension data (Table 1).”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Findingown data

    The R values for PFOS transport in residual decane columns are 2.6 and 4.0 for Sn = 0.29 and 0.54, respectively, greater than the R of 1.3 for transport in the decane-free column.

    “The R values for PFOS transport in the residual decane columns, 2.6 and 4.0 for Sn = 0.29 and 0.54, respectively, are greater than the R (1.3) for transport in the decane-free column.”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Findingown data

    Kn values for PFOA are greater than those for PFOS for both TCE and decane, although for a given NAPL the Kn values are of the same order of magnitude and have overlapping 95% confidence intervals.

    “The Kn values for PFOA are greater than those determined for PFOS for both TCE and decane, although for a given NAPL the Kn values are of the same order of magnitude and have overlapping 95% confidence intervals.”
    Quote in the paperNot a substantial claim

  • It may state two separate claims as one.

    Findingown data

    Interfacial activity is greatest for the longest-chain PFAS (PFOS) and weakest for the shortest-chain (PFPeA).

    “It is observed that interfacial activity is greatest for the longest-chain PFAS (PFOS) and weakest for the shortest-chain (PFPeA).”
    Quote in the paperNot a substantial claim

  • It may state two separate claims as one.

    Findingown data

    The Kn value for PFOA with TCE is 0.19, greater than the Kn value for PFOA with decane (0.07), although the 95% confidence intervals overlap.

    “A similar trend is observed for PFOA, where the Kn value for PFOA with TCE (0.19) is greater than the Kn value for PFOA with decane (0.07), although the 95% confidence intervals also overlap.”
    Quote in the paperNot a substantial claim

  • It may state two separate claims as one.

    Findingreasoning

    The calculated R value for a representative lower concentration of 100 μg/L using the TCE-water system (Sn = 0.28) is 10.5, which is larger than the R values measured for the experiments (C0 = 10 mg/L).

    “The calculated R is 10.5, which is larger than the R values measured for the experiments (for which C0 was 10 mg/L).”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Findingown data

    For all experiments, partitioning into the bulk NAPL has the lowest contribution to retention, with contributions ranging from <1% to ~3% for PFOS experiments.

    “For all experiments, partitioning into the bulk NAPL has the lowest contribution to retention, with contributions ranging from <1% to ~3% for PFOS experiments.”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Findingcitation

    Solid-phase sorption has the highest (85%) percent contribution to retention for the McKenzie et al. PFOS data, versus 15% for adsorption to the NAPL-water interface.

    “Solid-phase sorption has the highest (85%) percent contribution to retention for the McKenzie et al.28 PFOS data, versus 15% for adsorption to the NAPL-water interface.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [28] source

  • It may state two separate claims as one.

    Findingreasoning

    The contribution from NAPL-water interfacial adsorption is almost 20% greater for the lower concentration, while the contributions from the other two terms are smaller.

    “The contribution from NAPL-water interfacial adsorption is almost 20% greater for the lower concentration, while the contributions from the other two terms are smaller.”
    Quote in the paperNot a substantial claim

  • It may state two separate claims as one.

    Interpretationcitation

    Molar volume serves as a good descriptor for both air-water surface activity and NAPL-water interfacial activity.

    “Notably, molar volume serves as a good descriptor for both air-water surface activity and NAPL-water interfacial activity.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim. It may be too vague to check against evidence.

    Interpretationown data

    The batch NAPL-partitioning experiments should be considered to provide semi-quantitative measures of partitioning.

    “Thus, the batch NAPL-partitioning experiments should be considered to provide semi-quantitative measures of partitioning.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim.

    Study design and conductreasoning

    High aqueous concentrations were used in the batch experiments to reduce the impact of interfacial adsorption on measurements, given the nonlinearity of the NAPL-water interfacial adsorption coefficient in this concentration range.

    “High aqueous concentrations were used to reduce the impact of interfacial adsorption on measurements, given the nonlinearity of the NAPL-water interfacial adsorption coefficient in this concentration range.”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Premisecitation

    Soils and vadose zones at AFFF sites typically contain large quantities of PFAS and are likely to serve as long-term sources.

    “Furthermore, recent research has demonstrated that soils and vadose zones at these types of sites typically contain large quantities of PFAS and therefore are likely to serve as long-term sources.13,14”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [13] source
    • cites [14] source

  • Probably not a substantial claim. The paper’s conclusions may not depend on it.

    Study design and conductnone given

    Experiments were first conducted with the nonreactive tracer to determine the hydrodynamic properties of the packed columns and ensure that they were well packed.

    “Experiments were first conducted with the NRT to determine the hydrodynamic properties of the packed columns and ensure that they were well packed.”
    Quote in the paperNot a substantial claim

  • It may state two separate claims as one.

    Interpretationreasoning

    As NAPL saturation increases and water saturation decreases, more NAPL-water interfacial area is available for adsorption, resulting in increased retention.

    “Thus, as NAPL saturation increases, and water saturation decreases, more NAPL-water interfacial area is available for adsorption, resulting in increased retention.”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Interpretationcitation

    The greater Ki for SGW compared to NaCl is attributable to the presence of both monovalent and divalent cations in SGW versus only monovalent cations in NaCl; divalent cations produce a greater reduction in electrostatic repulsion within the interface, enhancing interfacial adsorption of PFAS.

    “This is consistent with the findings of Brusseau and Van Glubt31 and can be attributed to the presence of both monovalent and divalent cations in the SGW versus only monovalent cations in the NaCl solution. Divalent cations produce a greater reduction in electrostatic repulsion within the interface, thereby enhancing interfacial adsorption of the PFAS.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Brusseau and Van Glubt31

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • It may state two separate claims as one.

    Interpretationreasoning

    The presence of NAPL increases PFOS and PFOA retention and produces larger retardation factors.

    “The preceding results indicate that the presence of NAPL increases PFOS and PFOA retention and produces resultantly larger retardation factors.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.

    Premisecitation

    PFAS partitioning into bulk NAPL and adsorption at the NAPL-water interface were discussed as possible reasons for enhanced retardation, but their specific contributions were not delineated or quantified.

    “PFAS partitioning into bulk NAPL and adsorption at the NAPL-water interface were discussed as possible reasons for the observed enhanced retardation, but their specific contributions were not delineated or quantified.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites McKenzie et al. [28] source

  • It may state two separate claims as one.

    Premisecitation

    PFAS surface/interfacial activity and Ki values are influenced by surfactant properties including carbon chain length and headgroup properties, and by solution properties including electrolyte composition and ionic strength.

    “The preceding results are consistent with prior research showing that PFAS surface/interfacial activity and Ki values are influenced by surfactant properties, including carbon chain length and headgroup properties, and solution properties, including electrolyte composition and ionic strength (e.g., refs 29, 31–34).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites refs 29, 31–34

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • It may state two separate claims as one.

    Interpretationown data

    Both NAPL-water interfacial adsorption and solid-phase sorption contribute significantly to retention in the systems employed herein.

    “The above results indicate that both NAPL-water interfacial adsorption and solid-phase sorption contribute significantly to retention in the systems employed herein.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim. It may be too vague to check against evidence. The paper’s conclusions may not depend on it. The paper may give no reason why it holds.

    Interpretationreasoning

    These applications may induce changes to NAPL behavior.

    “In these cases, accounting for initial high PFAS concentrations is important, and, as discussed above, these applications may induce changes to NAPL behavior.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim. The paper’s conclusions may not depend on it.

    Interpretationreasoning

    The disparity between column-measured and interfacial-tension Ki values at higher Sn may be due to changes in hydraulic accessibility of the NAPL.

    “This disparity may be due to changes in hydraulic accessibility of the NAPL at higher Sn.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim. The paper’s conclusions may not depend on it.

    Premisecitation

    In some cases, NAPL solubilization occurred only when surfactant concentrations were greater than the critical micelle concentration (CMC).

    “In some cases, NAPL solubilization occurred only when surfactant concentrations were greater than the critical micelle concentration (CMC) (e.g., refs 47–49).”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites [47] source
    • cites [48] source
    • cites [49] source

      Checked before — its earlier verdict is held back until a new check runs.

  • Probably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.

    Interpretationreasoning

    Given that the McKenzie et al. soil contains fractions of silt and clay, it is likely that the interfacial area for the soil is somewhat larger than for the sand and thus the predicted R may be somewhat greater than 15.

    “Given that their soil contains fractions of silt and clay, it is likely that the interfacial area for the soil is somewhat larger than for the sand and thus the predicted R may be somewhat greater than 15.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [28] source

  • Probably not a substantial claim. The paper’s conclusions may not depend on it.

    Study design and conductnone given

    This study is focused on TCE as a single-component NAPL.

    “In addition, this study is focused on TCE as a single-component NAPL.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim. The paper’s conclusions may not depend on it.

    Interpretationnone given

    Mobilization impacts in particular may be of greater concern for three-phase systems such as in the vicinity of the capillary fringe.

    “Mobilization impacts in particular may be of greater concern for three-phase systems such as in the vicinity of the capillary fringe.”
    Quote in the paperNot a substantial claim

  • It may state two separate claims as one.

    Interpretationreasoning

    The NAPL may obstruct access of the solution to some pore domains, thereby reducing the overall magnitude of solid-phase sorption and resulting in reduced measured retardation.

    “Additionally, the NAPL may obstruct access of the solution to some pore domains, thereby reducing the overall magnitude of solid-phase sorption. This would also result in reduced measured retardation.”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Interpretationown data

    Partitioning into NAPL provides a minor contribution to overall retention and retardation, with the one exception of PFOA and residual TCE (19%).

    “Thus, partitioning into NAPL is observed to provide a minor contribution to overall retention and retardation, with the one exception of PFOA and residual TCE (19%).”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Interpretationcitation

    This NT value is lower than that determined to cause mobilization, between 2x10−5 to 5x10−5, and is consistent with the observation of no mobilization for the experiment.

    “This value is lower than that determined to cause mobilization, between 2x10−5 to 5x10−5 (e.g., ref 55), and is consistent with the observation of no mobilization for the experiment.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [55] source

  • Probably not a substantial claim. It may be too vague to check against evidence. The paper’s conclusions may not depend on it. It may state two separate claims as one.

    Interpretationreasoning

    This consistency illustrates the robustness of the retention model and the data-analysis methods employed herein.

    “This consistency illustrates the robustness of the retention model and the data-analysis methods employed herein.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim. It may state two separate claims as one.

    Interpretationreasoning

    Such high concentrations are relevant for new AFFF releases as well as for historical-release scenarios.

    “However, such high concentrations are relevant for new AFFF releases as well as for historical-release scenarios.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim.

    Premisecitation

    McKenzie et al. observed that the presence of TCE NAPL generally resulted in increased retardation of the PFAS.

    “They observed that the presence of TCE NAPL generally resulted in increased retardation of the PFAS.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [28] source

  • Probably not a substantial claim. The paper may give no reason why it holds.

    Premisenone given

    NAPLs are often comprised of multiple compounds with different properties.

    “However, NAPLs are often comprised of multiple compounds with different properties.”
    Quote in the paperNot a substantial claim

  • It may state two separate claims as one.

    Interpretationown data

    At higher Sn, some portion of the NAPL-water interfaces in the columns may be hydraulically inaccessible to the PFOS solution, which would result in reduced retention and thus smaller than expected Ki values.

    “At higher Sn, some portion of the NAPL-water interfaces in the columns may be hydraulically inaccessible to the PFOS solution, which would result in reduced retention and thus smaller than expected Ki values.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.

    Premisecitation

    These PFOS R values were determined to be statistically different, whereas R values for PFOA were not.

    “These values were determined to be statistically different, whereas Rs for PFOA were not.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [28] source

  • It may state two separate claims as one.

    Interpretationreasoning

    For a soil with greater sorption capacity, the relative contribution of solid-phase sorption would be expected to be greater, and that of NAPL-water interfacial adsorption correspondingly lesser, than for the sand used in the present study, assuming similar magnitudes of NAPL-water interfacial area.

    “For a soil with greater sorption capacity, the relative contribution of solid-phase sorption would be expected to be greater, and that of NAPL-water interfacial adsorption correspondingly lesser, than for the sand used in the present study (assuming similar magnitudes of NAPL-water interfacial area).”
    Quote in the paperNot a substantial claim
    • The authors state this as an assumption: Similar magnitudes of NAPL-water interfacial area apply when comparing a soil with greater sorption capacity to the sand used in the present study.

  • Probably not a substantial claim.

    Study design and conductnone given

    The mobilization experiments conducted herein comprised two-phase systems.

    “It is important to note that the mobilization experiments conducted herein comprised two-phase systems.”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Interpretationreasoning

    NAPL solubilization and mobilization may be of greater significance for sites with new AFFF releases and for reconstruction analysis of historical AFFF releases wherein high initial PFAS concentrations are relevant.

    “However, NAPL solubilization and mobilization may be of greater significance for sites with new AFFF releases and for reconstruction analysis of historical AFFF releases wherein high initial PFAS concentrations are relevant and considering that the presence of some of the other AFFF constituents such as hydrocarbon surfactants and cosolvents can influence solubilization and mobilization.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim.

    Interpretationreasoning

    The disparity between predicted and measured R values at higher NAPL saturations may be due to hydraulic inaccessibility of NAPL-water interfaces.

    “One reason for the disparity may be due to hydraulic inaccessibility of NAPL-water interfaces as discussed above.”
    Quote in the paperSubstantial claim
55 of 55

  • The paper relies on this without support.

    PFOS and PFOA are recalcitrant.

    “As PFOS and PFOA are recalcitrant, variability in the mass recovery can be attributed to analytical uncertainty.”

  • The paper relies on this without support.

    The experimental conditions represent the conditions present at many AFFF legacy sites.

    “under the conditions present at many AFFF legacy sites”

  • The paper relies on this without support.

    The dielectric constant is approximately 3.4 for TCE and approximately 2 for decane.

    “For example, the dialectric constant, related to polarity, is approximately 3.4 for TCE compared to approximately 2 for decane.”

  • The paper relies on this without support.

    PFOS and PFOA are representative PFAS for the studied AFFF source-zone scenarios.

    “PFOS (CAS# 1763-23-1, Sigma-Aldrich, 98% purity) and PFOA (CAS# 335-67-1, Alfa Aesar, 95%) were used as representative PFAS in the experiments.”

  • The paper relies on this without support.

    TCE and decane are representative dense and light NAPLs for the studied systems.

    “Trichloroethene (CAS# 79-01-6, Sigma-Aldrich, >99.5% purity) and decane (CAS # 124-15-5, Sigma-Aldrich, 99% purity) were used as representative dense (DNAPL) and light (LNAPL) NAPLs, respectively.”

  • The authors state this as an assumption.

    Similar magnitudes of NAPL-water interfacial area apply when comparing a soil with greater sorption capacity to the sand used in the present study.

    “(assuming similar magnitudes of NAPL-water interfacial area)”

  • The paper relies on this without support.

    Solid-phase sorption of PFAS is often nonlinear.

    “In addition, solid-phase sorption of PFAS is also often nonlinear.”

  • The paper relies on this without support.

    High PFAS concentrations (100s of mg/L) are rarely observed at legacy AFFF source-zone sites.

    “Such high concentrations are rarely observed at legacy AFFF source-zone sites.”
8 of 8

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • Conflicting retardation factors for the same decane experiment

    Minor

    The PFOS experiment with residual decane at Sn = 0.29 is reported to have an R value of 2.6, but the later comparison gives 2.5 for the experiment at the same saturation and input concentration.

1 of 1

Citations

Cites

Flagged first, then by citations

Research works printed but not linked: 1

  1. Aly Y. H., 2018, J. Environ. Eng., 144, 040180

Cited by

Sorted by citations

Related

Metadata

Authors
Van Glubt, S., & Brusseau, M. L.
Affiliations
  • Environmental Science Department, University of Arizona, Tucson, Arizona 85721, United States
  • University of Arizona (US)
Corresponding author
Brusseau, Mark L.
ORCID
Venue
Environmental Science & Technology
Publisher
American Chemical Society (ACS)
Published
2021-03-05
Volume
55
Issue
6
Pages
3706-3715
ISSN
  • 0013-936X (ISSN-L)
  • 1520-5851
DOI
10.1021/acs.est.0c07355
PMC
PMC8634874
OpenAlex
W3133812873
Cited by
55
References
54
Citations by year
2026: 9 · 2025: 6 · 2024: 13 · 2023: 11 · 2022: 9 · 2021: 7
FWCI
3.40
Type
journal article
Language
en
Open access
Licence
Locations
  • Environmental Science & Technology (publishedVersion)
  • PubMed (publishedVersion)
  • PubMed Central (acceptedVersion)
Funders
National Institute of Environmental Health Sciences (P42 ES 4940)
Topics
  • Physical Sciences › Environmental Science › Environmental Chemistry › Per- and polyfluoroalkyl substances research
  • Physical Sciences › Environmental Science › Environmental Engineering › Groundwater flow and contamination studies
  • Physical Sciences › Environmental Science › Environmental Engineering › Environmental remediation with nanomaterials
Keywords
per- and polyfluoroalkyl substances, non-aqueous phase liquids, aqueous film-forming foam, PFOS, perfluorooctanoic acid, trichloroethylene, n-decane, retention factor, QSPR, transport in porous media
MeSH terms
Adsorption, Fluorocarbons, Surface Tension, Water, Water Pollutants, Chemical, Porosity

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.

A language model drew the claims from the paper on 2026-11-09, under version 3 of the claim definition (model deepseek-v4.1-flash, prompt extract-v3).

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Cited sources are checked with a language model’s help (gpt-6-sol).

Statistics and arithmetic are recomputed, not judged.

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