# Laboratory investigations offer new insights on how salinity and suspended matter concentration jointly affect the solid-to-water partitioning of PFAS in estuaries

Davide A.L. Vignati

► To cite this version:

Davide A.L. Vignati. Laboratory investigations offer new insights on how salinity and suspended matter concentration jointly affect the solid-to-water partitioning of PFAS in estuaries. 2025, 10.24072/pci.ecotoxenvchem.100249. hal-05360635

HAL Id: hal-05360635

https://hal.univ-lorraine.fr/hal-05360635v1

Submitted on 12 Nov 2025

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Laboratory investigations offer new
insights on how salinity and suspended
matter concentration jointly affect the
solid-to-water partitioning of PFAS in
estuaries

**Davide Anselmo Luigi Vignati** (based on peer reviews by 2 anonymous reviewers)

Chan Gao, Hélène Hudzinski, Patrick Pardon, Karyn Le Menach, Pierre Labadie (2025)
Investigation of the combined influence of salinity and particle concentration on the
adsorption of anionic and zwitterionic PFAS onto estuarine sediment using the RSM
modelling approach. HAL, ver. 3, peer-reviewed and recommended by Peer Community in
Ecotoxicology and Environmental Chemistry. https://hal.science/hal-05013537

Submitted: 03 April 2025, Recommended: 29 September 2025

**Cite this recommendation as:**

Vignati, D. A. L. (2025) Laboratory investigations offer new insights on how salinity and suspended matter concentration jointly affect the solid-to-water partitioning of PFAS in estuaries. *Peer Community in Ecotoxicology and Environmental Chemistry*, 100249. https://doi.org/10.24072/pci.ecotoxenvchem.100249

Published: 29 September 2025

Copyright: This work is licensed under the Creative Commons Attribution 4.0 International License. To view a copy of this
license, visit https://creativecommons.org/licenses/by/4.0/

Estuaries are important transition zones where marked and dynamic changes in pH, salinity and concentra-
tion of suspended particulate matter (SPM) contribute to control the ultimate environmental fate of riverborne
pollutants at the land-sea interface. In particular, the complex interplay between these variables and the
intrinsic properties of chemicals will determine the solid-to-water partitioning of environmental contaminants
and, eventually, which substances will be preferentially retained in the coastal zone or transported toward the
open ocean.

These considerations become particularly important for those human-made substances, such as per- and
polyfluroalkyl substances (PFAS), combining high environmental persistence with strong bioaccumulation and
biomagnification potentials. PFAS have indeed become notorious as *forever chemicals* due to their chemical
stability and have been detected in all environmental compartments including biota and humans (Evich et
al, 2022). Furthermore, the sheer number of existing PFAS (with new ones being regularly synthetized) is
in stark contrast with the limited number of specific molecules that have been thoroughly studied for their
(eco)toxicology and environmental fate (Evich et al. 2022). While waiting for restriction or end-of-use measures to be implemented and take effect, it has become clear that PFAS should be managed as a chemical class (Kwiatkowski et al., 2020). This class-approach, if applicable, would also be beneficial to understand the environmental fate of PFAS based on detailed studies on a limited number of representative molecules.

The present work from Gao et al. (2025) addresses some of the limitations in our current understanding of the environmental fate of PFAS by modelling the solid-to-water partitioning of a mixture of 11 PFAS as a function of salinity and SPM concentrations in controlled laboratory conditions. After determining the PFAS concentration range in which the substances adsorption onto SPM showed a linear behaviour, the solid-to-water partitioning of the PFAS mixture was studied across different combinations of salinities and SPM concentrations. Results showed that PFAS adsorption onto SPM was positively related to salinity and negatively related to SPM concentrations. Most importantly, SPM and salinity acted antagonistically on PFAS adsorption onto particles, with the increase of each term reducing the effect of the other one. The study acknowledges that modelled adsorption behaviour in controlled laboratory conditions seems to underestimate PFAS adsorption onto environmental particles as measured in real field situation, most likely due to hysteresis phenomena not accounted for in laboratory settings. Despite these limitations, Gao et al. (2025) provide a solid basis for improving modelling of PFAS behaviour in estuaries, which remains critical to effectively manage these pollutants at the interface between terrestrial and marine ecosystems.

**References:**

Evich MG, Davis MJB, McCord JP, Acrey B, Awkerman JA, Knappe DRU, et al. Per- and polyfluoroalkyl substances in the environment. Science. 2022;375(6580).

https://doi.org/10.1126/science.abg9065

Chan Gao, Hélène Budzinski, Patrick Pardon, Karyn Le Menach, Pierre Labadie (2025) Investigation of the combined influence of salinity and particle concentration on the adsorption of anionic and zwitterionic PFAS onto estuarine sediment using the RSM modelling approach. HAL, ver.3 peer-reviewed and recommended by PCI Ecotoxicology and Environmental Chemistry

https://hal.science/hal-05013537

Kwiatkowski, C. F., Andrews, D. Q., Birnbaum, L. S., Bruton, T. A., DeWitt, J. C., Knappe, D. R. U., Maffini, M. V., Miller, M. F., Pelch, K. E., Reade, A., Soehl, A., Trier, X., Venier, M., Wagner, C. C., Wang, Z., & Blum, A. (2020). Scientific Basis for Managing PFAS as a Chemical Class. Environmental Science & Technology Letters, 7(8), 532-543. https://doi.org/10.1021/acs.estlett.0c00255

# Reviews

## Evaluation round #2

DOI or URL of the preprint: https://hal.science/hal-05013537

Version of the preprint: 2

## Authors' reply, 23 September 2025

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Dear Dr. Labadie,

Thank you very much for the revised version of contribution PCI249.

I appreciate the attention you paid to the reviewers' comments and the improvements with respect to the original version.

Before making my final decision, I would be grateful if you could consider the following remarks. They concern minor issues arising from the revision of the original submission. These issues do not question the quality of the contribution, but I think it's better to address them at this stage.

Thank you again for submitting this research to PCI.

Looking forward to receiving your reply.

Best regards,

Davide Vignati

**Recommender observations in relation to remarks of Reviewer 1 (line numbers are those in the revised version)**

Response to lines 282-284. From my understanding of their paper, Yan et al. (2022) worked at a fixed SPM concentration of 2.5 g of sediments with variable salinities (section 2.3 of their work). If I am not mistaken, the revised text of the present contribution should therefore refer only to salinity. For example: "...changes in salinity may shift the equilibrium sorption amount, but not the time required to reach equilibrium". Please verify if changes to revision 1 are needed.

Response to line 397. I think that the authors want to refer to Table S11. Table S10 contains the regression coefficients for the Anova results. Table S11 contains the regression model equations showing the dependence of Kd on salinity (positive) and SPM (negative). Please check.

**Recommender observations in relation to remarks of Reviewer 2 (line numbers are those in the revised version)**

Line 500: I agree that overlooking hysteresis may lead to an underestimation of PFAS retention. Indeed, the actual Kd in the field are higher than the values determined in laboratory. Higher Kd values mean more retention in sediments. On the other hand, I do not see how overlooking hysteresis would lead to an underestimation of mobility. Shouldn't it be an overestimation of mobility? If laboratory experiments give Kd values lower than those in field situations (Table 2), laboratory-based Kd will predict soluble PFAS concentrations higher than those actually occurring in the field. Otherwise stated, laboratory-based Kd would predict PFAS to be more mobile than they actually are. Please verify if this reasoning is correct and correct text if necessary.

Figures 1, 2, 3 and 4. Thank you for increasing the size of the characters in the graphs.

However, it is still difficult to read some of them at a 125% zoom, which is the typical enlargement used when reading pdf texts on computer screens. Considering that you have the same axis titles for all panels (except for y-axes in figure 1), I would suggest not to include axis titles in all panels but to simply add them to the right and at the bottom of each figure. This would allow for larger fonts to be used (and for better resolution in figure 1). This option may also help in harmonizing the size of different panels in figure 4.

Additional specific notes:

In figure 1, you can have two y-axis titles.

In the caption Figure 4. 'Contour plots...' use plural as there are 11 plots.

Line 458. This was not noticed by reviewers. Countour plots for PFUnDA have the same shape as those for 8:2 FTAB as opposed to the other compounds. Does it mean that PFUnDA is also an exception to the general
trend described at lines 455–457? I trust your judgement on this.

Line 315–318 in revised version. Is Yin et al. (2022) an appropriate reference for this statement? They do not seem to mention decrease in sorption area linked to SPM aggregation/coagulation in agreement with the work using only one SPM concentration. Please verify.

**Proofreading remarks from the recommender**

- Please select and harmonize throughout the text: Kd or Kd (with a subscript)

- Harmonize use of hyphen '-' or n-dash '-' in intervals of numbers. The n-dash would be more appropriate.

- Table 2. Mention the sources for field and laboratory values in the table caption or as a foot note. This information is mentioned in the text, but it would be beneficial to add the same information also here for readers screening figures and tables before reading the text.

- Line 76 and 416: Revise in-text reference to (Zhang et al., 2019).

- Line 90: Revise in-text reference to (Zhang et al., 2023).

- Line 450: therefore is repeated two times. Please correct.

- Line 491: Is it a full stop after '...Munoz et al. (2017)? Or is it really a comma?

- Line 492: '...in estuarine sediments...' instead of '...in estuarine in sediments...'?

- Line 496: use n-dash or commas, not a mix of the two.

>>>>>>End of Recommender reply to Revision 1~~~~~~~~~<

**Evaluation round #1**

DOI or URL of the preprint: https://hal.science/hal-05013537

Version of the preprint: 1

**Authors' reply, 27 August 2025**

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**Decision by Davide Anselmo Luigi Vignati**, posted 19 May 2025, validated 27 May 2025

Dear Dr. Labadie,

thank you very much for submitting the contribution *Investigation of the combined influence of salinity and particle concentration on the adsorption of anionic and zwitterionic PFAS onto estuarine sediment using the RSM modelling approach* to PCI Ecotoxicology and Environmental Chemistry.

The reviewers recognize the scientific quality of the submitted work, but request some changes to the original submission before it can be considered for publication.

You will find their comments included in the present message. Please let us know whether you will consider submitting a revised version of this contribution.

Thank you very much for your consideration and please accept my apologies for the slightly long review time.

Truly yours,

Davide Vignati (recommender, PCI Ecotoxicology and Environmental Chemistry).
Reviewed by anonymous reviewer 1, 10 May 2025

The manuscript presents a laboratory-controlled study on the adsorption kinetics and isotherms of 11 anionic and one zwitterionic PFAS under varying salinity and suspended particulate matter (SPM) conditions.

Overall, the manuscript largely consists of a collection of results that confirm existing knowledge in the literature—as the authors themselves correctly acknowledge. The only potentially novel finding is the observed interaction between salinity and SPM, although this interaction is somewhat expected and not particularly surprising.

Nonetheless, I believe the manuscript is suitable for publication. It is well written, the results are clearly presented, and the experimental procedures are described with sufficient detail. I recommend improving the clarity of the manuscript by adding explicit references to the data, and/or corresponding figures and tables when discussing experimental results (e.g., lines 283, 376, etc.).

Specific comments:

L55–56: The statement appears inaccurate. PFAS sorption onto suspended sediments does not affect sediment-water interactions per se, as these processes occur independently of the presence of PFAS. Please revise this sentence to clarify the intended meaning.

L271–274: The text states that sorption equilibrium was achieved after 24 hours in the kinetic experiments, and that subsequent adsorption tests were conducted using this equilibration time. However, no supporting data or discussion is provided to demonstrate that equilibrium is also reached within 24 hours under varying salinity or SPM conditions. Please provide justification or additional discussion on this point.

Reviewed by anonymous reviewer 2, 13 May 2025

Title and abstract

Does the title clearly reflect the content of the article? Yes

Does the abstract present the main findings of the study? Yes

Introduction

Are the research questions/hypotheses/predictions clearly presented? Yes, but research gap needs improvement.

Does the introduction build on relevant research in the field? Yes

Materials and methods

Are the methods and analyses sufficiently detailed to allow replication by other researchers? Yes, but SI is needed as well (which is fine)

Are the methods and statistical analyses appropriate and well described? Yes

Results

In the case of negative results, is there a statistical power analysis (or an adequate Bayesian analysis or equivalence testing)? Not Applicable

Are the results described and interpreted correctly? Yes

Discussion

Have the authors appropriately emphasized the strengths and limitations of their study/theory/methods/argument? Yes, but can be improved.

Are the conclusions adequately supported by the results (without overstating the implications of the findings)?

Yes

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