Distribution of Thallium in Sediments of the Fiora River Catchment, Central Italy: Implications for Its Sources

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This study investigated the total content of thallium in sediment of a river catchment in central Italy, other geogenic sources such as the high-K volcanic rocks might contribute to the slight higher Tl (up to 2 mg/kg) in some site. The study is conducive to understand the environmental source of Tl in this region and its environmental impacts.

1. how about the national average of Tl content in soil in Italy.

2. The reviewer suggests conducting a comparative analysis to compare the results of this study with the thallium content in river sediments or soils that affected by mining or smelting activities related to mercury, antimony, lead and zinc, other non-ferrous metals or iron sulfide;

   3. Have other indicators or elements (such as potassium, mercury, antimony, etc.) been tested in the sediment in this study? If so, it is recommended to conduct a comprehensive analysis to determine the source of thallium in the sediment.

Author Response

Please see the attachment for the response.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The Reviewer’s Comments

to the article by

Alessia Nannoni, Pierfranco Lattanzi, Guia Morelli, Cesare Fagotti, Rossella Friani, Valentina Rimondi, Pilario Costagliola

A mainly geogenic origin of thallium in the Fiora River catchment, Monte Amiata mining district, central Italy

The manuscript presents data on Tl content in the bottom sediments in Fiora River. I find it strange that the journal Minerals was chosen to publish these data, since there is no mineralogical analysis in this study. Although mineralogical research of bottom sediments, as well as determination of the trace element composition of sulfide minerals (as sources of Thallium) could significantly raise the level of the research conducted.

The abstract requires rewriting. It is necessary to add relevance to the research and its aim. In its current form, there is no semantic connection between the first and subsequent statements. This needs to be corrected.

It's not at all clear how to conclude «It is therefore concluded that most Tl in the catchment is of geogenic origin.» was formulated from «Thallium contents are comparatively low (0.1-0.4 mg/kg) in sediments of creeks directly draining the mining areas, whereas they increase up to 2 mg/kg in the catchment section that drains the Vulsini high-K volcanic province, where no known mineral deposits occur. It is therefore concluded that most Tl in the catchment is of geogenic origin.» I hope to find a justification further in the text of the article, but it is obvious that this needs to be corrected in the abstract.

«The estimated Tl mass load discharge into the Mediterranean Sea 21 from the Fiora River is at least 0.1 t/y.» - This statement reads as if the Tl in its pure form enters the Mediterranean Sea. Apparently, it is about the removal of Tl-containing bottom sediments into the Mediterranean Sea.

And finally, the last sentence from the abstract is not clear how it is connected with the previous text.

The image in Figure 2 cannot be called a geological map. Please choose a suitable caption.

A sampling map is missing to understand the scope of the study. However, I do not insist on adding such a map.

The information from Table 2 is duplicated in Figure 4. Moreover, the graphic representation is better perceived. Perhaps, for maximum clarity, the size of the point can be made variable depending on the content of Tl

A significant weakness of the study is the description of the sources of Thallium based solely on published articles by other researchers. The fact that sulfides are a common source of Tl is known and generally does not require justification. However, not all sulfides, like pyrites in particular, are the same and contain the same amount of trace elements. The correct determination of the trace element composition of sulfide minerals is carried out using the LA-ICP-MS, and not the ICP-MS as described in [31], which you refer to when constructing the discussion.

My main remark is that the conclusion about geogenic origin is not justified. The high concentrations of Tl in sediments cannot be explained by the spatial location of the mines. It is necessary to discuss the mechanisms of Tl entry into river sediments. There are a few questions worth answering:

What are the pathways of Tl entry into bottom sediments? Was it physical removal or formation of secondary mineral phases? Do you consider the mechanism of Tl sorption on clays? Manganese hydroxide? What form is Tl found in bottom sediments?

It is obvious that the highest contents of Tl should be found in locations where Tl is included in the minerals of bottom sediments. However, in this study the discussion is very superficial and most likely contains erroneous reasoning.

In general, research contains interesting data on the content of Tl in bottom sediments of Fiora River in Monte Amiata mining district. However, the discussion requires deep reworking.

Comments for author File: Comments.pdf

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

Reviewer comments

The manuscript "A mainly geogenic origin of thallium in the Fiora River catchment, Monte Amiata mining district, central Italy" offers valuable insights into where thallium (Tl) comes from and how it varies in stream sediments from a region impacted by mining in the past. The manuscript has been critically reviewed and a few corrections and questions raised by reviewer, such as

1. Line 2: of further 23 studies…… changed to for further 23 studies
2. Line 162: Why were samples only collected in 2022? Could the authors address how seasonal variations might affect Tl concentrations and flux?
3. Despite Tl’s known toxicity, there is no discussion of bioavailability or potential biological impacts.
4. if thallium is most toxic than Pb, Cd and Zn, I suggested to author to calculate Igeo values, pollution load, ecological index, etc.
5. Does the amount of organic matter or the size of the sediment grains be affect the levels of Tl?
6. I suggested the authors conclude the present results with a comparison to other volcanic regions in Italy or globally.

 

Comments for author File: Comments.pdf

Comments on the Quality of English Language

Reviewer comments

The manuscript "A mainly geogenic origin of thallium in the Fiora River catchment, Monte Amiata mining district, central Italy" provides helpful information regarding where thallium (Tl) comes from and how it varies in stream sediments from a region impacted by mining in the past. The manuscript has been critically reviewed and a few corrections and questions raised by reviewer, such as

1. Line 2: of further 23 studies…… changed to for further 23 studies
2. Line 162: Why were samples only collected in 2022? Could the authors address how seasonal variations might affect Tl concentrations and flux?
3. Despite Tl’s known toxicity, there is no discussion of bioavailability or potential biological impacts.
4. if thallium is most toxic than Pb, Cd and Zn, I suggested to author to calculate Igeo values, pollution load, ecological index, etc.
5. Does the amount of organic matter or the size of the sediment grains be affect the levels of Tl?
6. I suggested the authors conclude the present results with a comparison to other volcanic regions in Italy or globally.

 

Author Response

Please see the attachment for the response.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

The Reviewer’s Comments 2

to the article by

Alessia Nannoni, Pierfranco Lattanzi, Guia Morelli, Cesare Fagotti, Rossella Friani, Valentina Rimondi, Pilario Costagliola

A mainly geogenic origin of thallium in the Fiora River catchment, Monte Amiata mining district, central Italy

I thank the authors for their detailed answers to my questions. In my opinion, the current version of the manuscript is much more thoughtful. I highly appreciated the revised version of Figure 3. This data presentation visualized the results of the study very well.

Regarding my comment on the suitability of the manuscript for publication in Minerals, I understand that the editor is assembling a special issue.

In any case, I consider the manuscript suitable for publication.

I wish the authors productive scientific research!

Comments for author File: Comments.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

Dear Editor, 

The authors addressed all the comments made by the reviewers. Therefore, I recommend that the editor accept the manuscript as it is currently written. There is no need for additional corrections.