Content of Heavy Metals in the Lichens of Winter Reindeer Pastures of the Timan and Bolshezemelskaya Tundras

Round 1

Reviewer 1 Report

Dear Authors,

 

Greetings!

 

The article “The content of heavy metals in lichens of winter reindeer pastures of the Timan and Bolshezemelskaya tundra” was dedicated to studying the content of heavy metals (zinc, cadmium, copper and lead) in lichen present in Timan and Bolshezemelskaya tundra.

 

References need to be updated. The manuscript presents 37 references, but only 10 of them are studies published from 2017 to 2022.

 

Regarding introduction, it only contains four references and it is too short. There are important topics that need to receive attention in this section: recent data on heavy metal’s pollution especially in that type of ecosystem, the harmful potential of these metals to living beings and the importance on using lichens in this type of study. Studies such as https://www.mdpi.com/2076-3417/12/14/6988, https://aer.pensoft.net/article/27594/ and https://www.e3s-conferences.org/articles/e3sconf/abs/2019/24/e3sconf_wri-162018_02010/e3sconf_wri-162018_02010.html for example, can be cited as same as other ones related to the manuscript’s theme. When it comes to the information “Artic ecosystems are most vulnerable”, a reference must be added in line 30.   

 

Regarding materials and methods’ section it must also be improved. Research design needs to be adjusted; it must not be used 1-2g of initial material to quantify heavy metals. In order to generate data that can be compared it is necessary to present precision in quantity and to use the same amount of material for each collected sample in each one of the 11 spots. Otherwise, it will be discussed that some area presents more pollutants and maybe it is only consequence of a larger amount of material analyzed. It is also necessary to present data used in comparisons mentioned in lines 70 and 71 as same as the statistic analysis applied to compare the results. In line 58, it is said that material was collected in 2019; in line 111 it is said that it happened in 2018 (please verify this information and adjust the text). Line 60 lacks a dot between the words University and Lichens. Samples were dried at 1050ºC and then heated to 950ºC? Please, verify this information; these temperatures are too high. It is also necessary to provide the manufacturer of chemicals used (nitric acid and hydrogen peroxide) and to adequate ml to International System using “L” as a capital letter.

 

When it comes to Results, the article lacks statistics on them To perform comparisons it is necessary to analyze data to verify if significance from a statistic point of view is present. Sections 3.1 and 3.2 are not results as they are not related to the materials and methods’ section. The “background” should be adapted to be presented in introduction section and not in results. Table 1 should be kept this section (results).

 

The absence of statics does not allow that data presented support the results. 

 

In Discussion it is mentioned in lines 208 and 209 that “The high concentration of metals in lichen thalli does not influence its external structure: there are not necrotic areas; the size, morphology of the thallus, and pigmentation are typical for this species.” However, these results are not presented to the readers. Please, present the data before discussing it.

 

Please, dedicate some attention to Figure 1. Caption should start with capital letter. According to what is written, the image has the intention to explore Pechora’s geology. The difference in colors indicate something? If yes, it should be present in the image what each color represents.

 

When it comes to English, language and style are fine and only minor spell check is required.

Author Response

Good afternoon. We bring our sincere words of gratitude for such a detailed analysis of our article. I hope our corrections and comments will be clear and convincing

Author Response File: Author Response.docx

Reviewer 2 Report

A good biomonitoring study using lichen, however;

1) many typo errros found such as 1050C (should be 105 degree C),  many more, please check every single word carefully!

2) There is no data validation using CRM for lichen (or plants) of Cd, Pb, Cu and Zn. I am not confident of the metal data presented in this paper.

3) I am lost when I read your paper. The overall flow and readability must be improved.

4) Abstract: The mechanism discovered by the authors (of the present study?) may also take place under similar conditions in other regions of the Arctic in the world. [COmment: How sure are you saying so?.. comparable to the world region as well?)

Author Response

Good afternoon. We bring our sincere words of gratitude for such a detailed analysis of our article. I hope our corrections and comments will be clear and convincing

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The required alterations were successfully performed by authors

Author Response

Dear reviewer! My colleagues and I sincerely thank you for your attention to our article!

Reviewer 2 Report

CRM is certified reference materials. I wonder why you do not know what is CRM. Many scientific papers are easily rejected without data validation with CRM with good recovery percentages.

This is a very common data validation in metal analysis. If you used lichen, we usually we use CRM for plant to validate our data. It is always easy to analyse our samples for metals but it is not easy to get accurate data. I hope you can understand my point well. 

Author Response

Dear reviewer, thank you for the explanations!

In our daily analytical work, as well as in the analysis of lichens given in this article, we certainly use as standard state samples, but it was really the first time we encountered such an abbreviation and decided that we were talking about some special kind of elemental analysis. During the analysis, we used state standard samples of metal solutions of the following grades: Zn – SSS 7256-96 (Ural plant of chemical products, Russia); Cd – ГСО 6690-93,  Cu – ГСО 7998-93, Pb – ГСО 7012-93 (Samples and High-purity Substances, Russia). The use of these SSS is an integral part of the methodology of work on an atomic emission spectrometer, so we initially decided that it was unnecessary to specify such details. When working out the methodology at the beginning of the study, we used the industry standard sample 10-238-2019, but subsequently had to abandon it, since it was made for the analysis of plant material, and lichen layers can bind metal ions with a different strength, since they contain chitin. Therefore, subsequently, to control the quality of the device and the completeness of the salting, we used a working sample of yagel with a known additive of detectable components made on the basis of the state standard samples mentioned above. My colleagues and I are of the opinion that the use of certified samples, about which you write, is only one of the options for conducting in-laboratory quality control and is not a mandatory stage of laboratory chemical analysis. We are also of the opinion that a more effective method of improving the quality of laboratory measurement data is to increase the number of biological repetitions. It is in this regard that we have increased the number of canopies from one sample to ten.

Round 3

Reviewer 2 Report

Good response. I agree with you.

Please write a short note explanation in your 'Control Quality of metal analysis', part of your methodology.

I worked in the laboratory!

Author Response

Dear reviewer, please accept our sincere gratitude for your detailed comments and interest in our article. Your review is very important for our entire team, I even included a fragment dedicated to your comments in the content of lectures on biological research methods.
I have included information on the production of a control sample based on a working one in the text of the article, this fragment is highlighted in red and underlined. Thank you again for your attention to our article, it is very valuable for us!