Technical note: Effects of iron(II) on fluorescence properties  of dissolved organic matter at circumneutral pH

Jia, Kun; Manning, Cara C. M.; Jollymore, Ashlee; Beckie, Roger D.

doi:https://doi.org/10.5194/hess-25-4983-2021

Articles | Volume 25, issue 9

https://doi.org/10.5194/hess-25-4983-2021

© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/hess-25-4983-2021

© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 25, issue 9

Technical note

|

15 Sep 2021

Technical note |

| 15 Sep 2021

Technical note: Effects of iron(II) on fluorescence properties of dissolved organic matter at circumneutral pH

Kun Jia, Cara C. M. Manning, Ashlee Jollymore, and Roger D. Beckie

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Final revised paper (published on 15 Sep 2021)
Preprint (discussion started on 11 May 2020)

Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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- Supplement

RC1: 'Technical note: Effects of iron(II) on fluorescence properties of dissolved organic matter at circumneutral pH', Anonymous Referee #1, 09 Jun 2020
- AC1: 'Initial response to Reviewer 1', Cara Manning, 10 Jun 2020
- AC2: 'Final response to Reviewer 1', Cara Manning, 06 Oct 2020
RC2: 'Anonymous Review', Anonymous Referee #2, 24 Jun 2020
- AC3: 'Final response to Reviewer 2', Cara Manning, 06 Oct 2020

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

ED: Publish subject to minor revisions (further review by editor) (12 Oct 2020) by Marnik Vanclooster

ED: Reconsider after major revisions (further review by editor and referees) (12 Oct 2020) by Marnik Vanclooster

AR by Cara Manning on behalf of the Authors (23 Nov 2020) Author's response Manuscript

ED: Referee Nomination & Report Request started (14 Dec 2020) by Marnik Vanclooster

RR by Anonymous Referee #3 (23 May 2021)

Suggestions for revision or reasons for rejection

Overall, the revisions performed by the authors are acknowledged. However, some issues still require further clarification:
1. The effect of the added SO4 ions is still not accounted for. Could SO4 ions in the added concentration affect the obtained fluorescence spectra and indices? Is the spiked solution comparable to the naturally-occurring high-Fe(II) concentration water in the deltaic aquifer? This needs to be addressed (either by referencing previous research or experimentally).
2. Since the water sample used in this work was artificially spiked with an Fe(II) salt, a comparison between the highest concentration sample and the naturally-occurring high-Fe(II) concentration water in the deltaic aquifer would significantly strengthen the paper.
3. In the description of the FI (lines 239-243) the authors clearly state that the value of the index indicates the source of the organic matter. The following paragraph describes a change in FI caused by the increase in Fe(II) concentrations. However, the addition of Fe(II) clearly did not change the source of the organic matter in the system. This can be confusing to the reader and thus should be clarified and properly explained.
4. The last section of the introduction (lines 79-92) is very long and contains a description that is more suitable for the ‘Methodology’ section. I recommend shortening this section significantly.
5. In line 281 the authors state that the residuals of the PARAFAC model are plotted in the supporting information. However, I wasn’t able to find a supporting information file in your submission which makes the evaluation of this part difficult (I did find the online datasets, but these contain only .txt files and no plotted data).
6. The description of the main experiment and the aquifer location in line 48 appears again in the context of the objective (lines 71-76). This is an unnecessary repetition. I recommend omitting lines 48-50. The text in lines 46-48 can be joint to the following paragraph.
7. The ‘Conclusions’ section currently fits the description of a summary.
8. I find the separation between the results and the discussion unnecessary. However, I leave that to the authors’ consideration.

Technical comments:
1. Line 37: consider omitting the word ‘Additionally’.
2. Section 3.3: this section described data analysis rather than sample analysis. I recommend moving the first two lines (148-149) to the previous paragraph that describes the specifics of the Fe(II) addition experiment and changing the title to ‘Data analysis’.
3. Line 137: ‘An Fe spiking…’ instead of ‘A Fe spiking…’ (same as you correctly wrote in line 49).
4. Line 154: ‘collected at a bandpass of 5 nm’ instead of ‘collected at a bandpass at 5 nm’.
5. Line 165: omit ‘then’.
6. Line 174: change ‘=’ to ‘of’.
7. Section 4.1: the title of the section is awkwardly phrased. I recommend changing it to either ‘The effect of Fe-quenching on EEM fluorescence or at least ‘Fe-quenching effect on EEM fluorescence’ (same comment stands for section 4.2).
8. Line 218: add references.
9. Line 226: ‘Although a linear relationship…’ instead of ‘Although the linear relationship…’.
10. Line 251 ‘they’ instead of ‘he’ (the cited paper has multiple authors).
11. Line 269: ‘Similarly’ instead of ‘Similar’.
12. Line 278: omit the word ‘yet’.

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ED: Publish subject to revisions (further review by editor and referees) (24 May 2021) by Marnik Vanclooster

AR by Cara Manning on behalf of the Authors (01 Jul 2021) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (02 Jul 2021) by Marnik Vanclooster

RR by Anonymous Referee #3 (12 Jul 2021)

ED: Publish subject to minor revisions (review by editor) (04 Aug 2021) by Marnik Vanclooster

AR by Cara Manning on behalf of the Authors (09 Aug 2021) Author's response Author's tracked changes Manuscript

ED: Publish as is (10 Aug 2021) by Marnik Vanclooster

AR by Cara Manning on behalf of the Authors (10 Aug 2021)

Short summary

The effect of soluble reduced iron, Fe(II), on fluorescence data (excitation–emission matrix spectra parsed using parallel factor analysis) is difficult to quantitatively assign. We added varying quantities of Fe(II) into groundwater from an anaerobic aquifer. We showed that the overall fluorescence intensity decreased nonlinearly as Fe(II) increased from 1 to 306 mg L^-1 but that the parallel factor analysis component distribution was relatively insensitive to Fe(II) concentration.