Uranium in Lake Sediments of Humid Zone: A Case Study in the Southeast Fennoscandia (Karelia, Russia)

Round 1

Reviewer 1 Report

The topic of the manuscript is interesting and worth publishing in an international journal. It falls within the aim and scope of Water. The Introduction section needs a short paragraph at the beginning to discuss elements distribution issues in sediments worldwide. More papers related to this paragraph will be beneficial for the paper.  I suggest a major revision for this manuscript. Additional comments are included in the attached .pdf file.

Comments for author File: Comments.pdf

Author Response

Reply to reviewer 01

Dear Reviewer,

I thank you for reviewing my publication. I have changed the manuscript according part of your comments and edits. The corrected text with green highlights has already been sent to the editorial office. You can see some my answers to your the most important comments below.

(The comments and suggestions are in bold. Authors' replies were shown in italics)

The Introduction section needs a short paragraph at the beginning to discuss elements distribution issues in lake and stream sediments worldwide. More papers related to this paragraph will be beneficial for the paper.

I have expanded the Introduction section by adding new references and important details from the publications. I didn't use the work you suggested. They are of great interest, but they talk about river sediments, and I have focused on lake sediments in my work.

The authors have to decide if they prefer to use the symbol of an element or its full name.

I corrected uranium to U throughout the publication, except for the abstract section and places where the word 'Uranium' comes at the beginning of a sentence.

Please use the term "Earths' crust".

Of course. I have removed the woerd 'Clarke' by exchanging it on 'Earths' crust'

This section seems mostly the presentation of results. The author should shorten this section and revise accordingly. Only the most important findings of this study should be included which may be of interest of a larger audience.

I have reduced the conclusion section to a description of the most basic results.

In the corrected text I also took into account the comments and suggestions of other reviewer.

With regards, author

Reviewer 2 Report

The article "Uranium in lake sediments of the humid zone: a case study in the Southeast Fennoscandia (Karelia, Russia)" written by author Zakhar Slukovskii, representing scientific institutions: Institute of the North Industrial Ecology Problems of Kola Science Center of RAS, Institute of Geology of Karelian Research Center of RAS, Russia, is a case study.

 The aim of the work presented in the article was to assess the level of uranium accumulation in the contemporary lake sediments of the Republic of Karelia (Fennoscandia), considering regional geological and geochemical features. The data were obtained within the framework of different scientific projects. About 91 30 small lakes of the northern and southern parts of the Republic of Karelia, as well as 92 Vygozero Reservoir. Freshwater sediments were sampled from both ice of the water bodies and open water using an inflatable boat. To collect the sediments a Limnos sampler and a manual ‘Russian’ drill were used. Laboratory tests were conducted at the Analytical Center of the Institute of Geology at the Karelian Research Center, Russian Academy of Sciences (Petrozavodsk, Karelia), and at the Institute of Chemistry and Technology of Rare Elements and Minerals at the Kola Research Center, Russian Academy of Sciences (Apatity). The content of the main elements in the lake sediments was assessed using an ARL ADVANT’X X-ray fluorescence spectrometer (ThermoFisher Scientific). The concentrations of trace elements, including U, in the sediment samples, were determined using an XSeries-2 ICP-MS mass spectrometer (Thermo Fisher Scientific). The sequential extraction method was applied to separate various fractions of chemical elements in the lake sediment samples. The results were statistically processed using Microsoft Excel 2010. Inkscape 0.48 software was used to illustrate the results graphically.

 The highest U accumulation level was found in the lake sediments, which is under the influence of the North Onega ore-geochemical region, where V deposits and ore occurrences with a high content of U, Fe, Mo, and Cu are widespread. In the sediments of some studied lakes, Th anomalies were found, which often accompany U in ore geological formations. The analysis of uranium fractions in the sediments of some lakes in Karelia revealed the key role of the mineral (insoluble) phase in the accumulation of U, with a small share of the organic fraction in the accumulation of U in the studied lake sediments.

Research results, discussion, using advanced research techniques, and conclusions are logical, at a good scientific level. Among the critical remarks / for discussion, the following should be mentioned: limited characteristics of the geological structure, hydrological conditions, lack of a description of the mechanism of uranium transport to the lake environment, limited characteristics of the impact of anthropopressure on the enrichment of the environment in uranium and the health risk from bioavailable forms of U.

 Detailed comments are provided below.

1/ In three places in the article, the author compares the research results with the results of research on small lakes in the Southern Urals. Is the geological structure of the comparative region similar to Karelia?

2/ In the chapter "Conclusions," it is necessary to describe in detail what are the sources of pollution causing the "technical" migration of U in the environment.

3/ I suggest that the article to briefly describe the mechanism of uranium migration to the hydrological environment (lakes) because there is information about the geological structure and uranium content in lake sediments, i.e., the beginning and end, without discussing uranium transport.

4/ In the article, I found information about the health risk of bioavailable U forms in two places. This information should be extended.

5/ Figure 2, Figure 7 - the description in the titles of the figures, "... the main statistical parameters," is not sufficient. Provide appropriate explanations in the drawings.

6/ Figure 8, Figure 10 - instead of "I - exchangeable forms", write "II - exchangeable forms." In both figures, it is not clear from their description what distinguishes the left figure from the right figure

7/ I suggest to include a figure with the geological structure of the research area and with
a representative profile(s) of sediments from the studied lakes

8/ References. All items listed in the References are cited in the text.

The article is on a good scientific level. It needs to be supplemented in terms of nature and the environment. It represents the research results for a specific natural, geological, and hydrological environment and climatic conditions. The article should find a wide range of readers dealing with environmental, geochemical and mineralogical studies of uranium deposits and other radioactive elements, using modern research methods and tools - including sequential extraction methods, spectrometric studies, statistical analyses.

Author Response

Reply to reviewer 02

Dear Reviewer,

I thank you for reviewing my publication. I have changed the manuscript according part of your comments. The corrected text with green highlights has already been sent to the editorial office. You can see my answers to your comments and suggestions below.

(The comments and suggestions are in bold. Authors' replies were shown in italics)

In three places in the article, the author compares the research results with the results of research on small lakes in the Southern Urals. Is the geological structure of the comparative region similar to Karelia?

The geology of Karelia and the Southern Urals are not similar. The comparison was made because there was a similar extensive study of lakes in this region using the mass spectrometry method that I did. I think to compare different region is admissible even they have different geological conditions.

In the chapter "Conclusions," it is necessary to describe in detail what are the sources of pollution causing the "technical" migration of U in the environment.

I think all you suggested is in section References. New tables or figures will increase the article that is large without it.

I suggest that the article to briefly describe the mechanism of uranium migration to the hydrological environment (lakes) because there is information about the geological structure and uranium content in lake sediments, i.e., the beginning and end, without discussing uranium transport.

I have added to the conclusion section information about the factors of man-caused impact on the accumulation of U in the urban environment.

In the article, I found information about the health risk of bioavailable U forms in two places. This information should be extended.

I have extended information about influence of U to the human health.

Figure 2, Figure 7 - the description in the titles of the figures, "... the main statistical parameters," is not sufficient. Provide appropriate explanations in the drawings.

I have added explanations to the captions of figures 2 and 7.

Figure 8, Figure 10 - instead of "I - exchangeable forms", write "II - exchangeable forms." In both figures, it is not clear from their description what distinguishes the left figure from the right figure.

I have corrected the caption for the figures.

I suggest to include a figure with the geological structure of the research area and with

a representative profile(s) of sediments from the studied.

I thought about your suggestion and decided that the use of a geological map in this article is not critical. Point descriptions of the geology are given in the text, and the areas of uronic deposits are shown in Figure 4. I believe that this is sufficient to understand the migration routes of uranium from sources to the studied lakes.

As for the sediment cores, I have prepared a supplementary figure with photographs of field work on some of the lakes.

References. All items listed in the References are cited in the text.

I have expanded the introduction and results sections by adding new data on the study of U in water and lake sediments. Therefore, new references have been added to the bibliography.

In the corrected text I also took into account the comments and suggestions of other reviewer.

With regards, author

Round 2

Reviewer 1 Report

The author has to carefully check all my initial comments to enhance further the quality of the manuscript.

Author Response

Dear Reviewer,

I have corrected the manuscript according to almost all of your initial comments. Please check the file that I sent to the journal after the first round of examination. I posted the responses to the main remarks in the journal earlier. And all the corrections are highlighted in green.

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Best wishes, author