Selenium and Heavy Metals in Soil–Plant System in a Hydrogeochemical Province with High Selenium Content in Groundwater: A Case Study of the Lower Dniester Valley
, Nadezhda Golubkina 2, Tatiana Sheshnitsan 1, Otilia Cristina Murariu 3, Alessio Vincenzo Tallarita 4 and Gianluca Caruso 4
Sotiria G. Papadimou
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsMy comments are in attachment.
Comments for author File: 
Comments.pdf
Local corrections may be topical.
Author Response
Responses to Reviewer 1
Dear Reviewer,
Thanks for your comments concerning our manuscript entitled “Selenium and Heavy Metals in Soil–Plant System in a Hydro-geochemical Province with High Selenium Content in Groundwater: A Case Study of the Lower Dniester Valley” (Manuscript ID: soilsystems-2714602). Those comments are all valuable and very helpful for revising and improving our paper. We have studied the comments carefully and tried our best to improve the manuscript. Revised portions are marked in red in the manuscript.
The responses to your comments are as follows:
This manuscript contains the results of the observation of the soils in selected part of Moldova. In this region, the ground is characterized by high Se content according to geological conditions. The relations are considered combined accumulation of Se, Mn, Zn and Cu in industrial plants and Couch grass. The conditions used for the sample preparation and statistical analysis are given in detail that opens a possibility for future testing of the results by other researchers. In my opinion, this study is interesting because the specific soil plant system was considered and the Se, Mn, Zn and Cu contents were determined for different soil types in Dniester valley. The general level of this study is high and manuscript could be considered for publication after minor revision aimed at the increase of paper quality. My several corrections proposed for the text are listed below for author consideration.
Author’s response: Thank you very much for your appreciation of our research
Page 1
Water-soluble Se (0.09 ± 0.03 mg · kg-1) in soils was higher by 27% than the total Se (0.33 ± 0.13 mg · kg-1) and increased with rising the total Se content (r = 0.845).
This sentence is unclear, (0.09 ± 0.03 mg · kg-1) can not be higher than (0.33 ± 0.13 mg · kg-1).
Author’s response: We are very sorry for our unclear writing. We made a correction of the sentence:
Water-soluble Se (0.09 ± 0.03 mg · kg–1) in soils was 32.1% of the total Se (0.33 ± 0.13 mg · kg–1) and increased with rising the total Se content (r = 0.845)
Page 1
Bioaccumulation is the gradual accumulation of certain substances such as heavy metals and selenium in plant tissues.
Bioaccumulation is the gradual accumulation of certain substances, such as heavy metals and selenium, in plant tissues.
Author’s response: Thanks for your corrections. We added them in the manuscript.
Page 1
These elements are derived from a variety of sources, including natural deposits, industrial activities and agricultural practices [1].
For generality, several other representative papers in this field could be cited additionally:
ACS Earth Space Chem. 7 (7) (2023) 1446-1458
Microorganisms 11 (2023) 11
Environment 10 (9) (2023) 150
Author’s response: Thanks for your suggestion. We added several of these citations and some another ones in the manuscript.
Page 1
It has been shown that these compounds can either affect plant growth and development or also disrupt the ecological balance of ecosystems [3,4,8,9,10].
It was shown that these compounds can either affect plant growth and development or also disrupt the ecological balance of ecosystems [3,4,8,9,10].
Author’s response: Thanks for your corrections. We added them in the manuscript.
Page 2
According to Hannigan et al. [12], Neogene (middle Sarmatian) clays contain abundant Se and are the source of Se in groundwater, whose concentrations were shown to locally exceed the maximum permitted value by 1.5-24.0 times and varied from 15.0 to 240.0 g · l-1.
According to Hannigan et al. [12], Neogene (middle Sarmatian) clays contain abundant Se and they are the source of Se in groundwater, which concentration was shown to locally exceed the maximal permitted value by 1.5-24.0 times and varied from 15.0 to 240.0 g · l-1.
Author’s response: Thanks for your corrections. We added them in the manuscript.
Page 2
Towards the north-east the terraces merge into the root slope of the Dniester valley, which is covered by a lower layer of deluvial sediments and is formed by sands and clays of the Upper Sarmatian.
Towards the north-east, the terraces merge into the root slope of the Dniester valley, which is covered by a lower layer of deluvial sediments and is formed by sands and clays of the Upper Sarmatian.
Author’s response: Thanks for your corrections. We added them in the manuscript.
Page 3
After 4-5 hours the flask was opened, the test tube was removed, rinsed with distilled water from the outside and dried with filter paper.
After 4-5 hours, the flask was opened, the test tube was removed, rinsed with distilled water from the outside and dried with filter paper.
Author’s response: Thanks for your corrections. We added them in the manuscript.
Page 4
where V is the acid volume used for titration of NaOH solution in the control experiment, ml; V1 is acid volume used for titration of excess NaOH in soil analysis, ml; C is concentration of HCl, mmol (eq) · ml 1; m is mass of the air-dry sample, g; 0.022 is molar mass of the carbon dioxide equivalent (1/2 CO2), g · mol 1 (eq); 2.273 is coefficient for conversion from CO2 to CaCO3 concentration; 1000 is coefficient for conversion to g · kg 1; K is the coefficient for conversion of analysis result to dry soil.
where V is the acid volume used for titration of NaOH solution in the control experiment, ml; V1 is the acid volume used for titration of excess NaOH in soil analysis, ml; C is the concentration of HCl, mmol (eq) · ml-1; m is the mass of the air-dry sample, g; 0.022 is the molar mass of the carbon dioxide equivalent (1/2 CO2), g · mol-1 (eq); 2.273 is the coefficient for conversion from CO2 to CaCO3 concentration; 1000 is the coefficient for conversion to g · kg-1; K is the coefficient for conversion of analysis result to dry soil.
Author’s response: Thanks for your corrections. We added all of them in the manuscript.
Page 4
The determination of total HMs (Mn, Zn, Cu) was performed by atomic absorption spectrometry with Aanalyst800 (Perkin Elmer, USA) using a flow-injection system FLAS-400 in aqua regia extracts of soil according to ISO 11047 [18].
The determination of total HMs (Mn, Zn, Cu) was performed by atomic absorption spectrometry with an Aanalyst800 (Perkin Elmer, USA) using a flow-injection system FLAS-400 in aqua regia extracts of soil according to ISO 11047 [18].
Author’s response: Thanks for your correction. We added it in the manuscript.
Page 4
The determination of exchangeable forms of metals and acid-soluble Cu in soil extracts was carried out using atomic absorption spectrophotometry with SHIMADZU AA-7000 (Shimadzu, Japan).
The determination of exchangeable forms of metals and acid-soluble Cu in soil extracts was carried out using atomic absorption spectrophotometry with the use of a SHIMADZU AA-7000 (Shimadzu, Japan).
Author’s response: Thanks for your correction. We added it in the manuscript.
Page 4
Total soil Se was determined in solutions obtained from acid digestion of perchloric and nitric acids at 120° for 1 h, 150° for 1 h and 180° for 1 h.
Please use "h" or "hour" over the whole text, but not a mixture.
Author’s response: Thanks for your advice. We made the appropriate changes to the manuscript.
Page 4
Descriptive statistics and correlation analysis among various sample groups were detected using STATISTICA 10.0 software (StatSoft Inc., 2011).
Descriptive statistics and correlation analysis among various sample groups were carried out using STATISTICA 10.0 software (StatSoft Inc., 2011).
Author’s response: Thanks for your correction. We added it in the manuscript.
Page 4
Pearson's or Spearman's correlation coefficients was calculated, and regression analysis was performed to examine the tightness and type of relationship between two variables.
Pearson or Spearman correlation coefficient was calculated, and regression analysis was performed to examine the tightness and type of relationship between two variables.
Author’s response: Thanks for your corrections. We added them in the manuscript.
Page 4
The Table 1 shows the main physicochemical characteristics of the Lower Dniester soils, relevant for assessing Se and HM content and mobility.
The main physicochemical characteristics of the Lower Dniester soils, relevant for assessing Se and HM content and mobility are shown in Table 1.
Author’s response: Thanks for your suggestion. We changed structure of the sentence in the manuscript.
Page 5
The range of SOC and carbonate content was very wide, from 8.4 to 27.1 g · kg-1 and from 12.6 to 67.2 g · kg-1, respectively.
The ranges of SOC and carbonate content were very wide, from 8.4 to 27.1 g · kg-1 and from 12.6 to 67.2 g · kg-1, respectively.
Author’s response: Thanks for your correction. We added it in the manuscript.
Page 5
Total Se is the highest in alluvial soils, which are mainly found in floodplain ecosystems, with an average of 0.36 ± 0.09 mg · kg-1.
Total Se is the highest in alluvial soils, which are mainly found in floodplain ecosystems, with an average value of 0.36 ± 0.09 mg · kg-1.
Author’s response: Thanks for your correction. We added it in the manuscript.
Page 5
Mean Se concentration decreases correspondingly to 0.32 ± 0.16 mg · kg-1 and 0.33 ± 0.12 mg · kg-1 in Luvy-Calcic Chernozems and Vorony-Calcic Chernozems with a rather larger variation.
Mean Se concentration decreases to 0.32 ± 0.16 mg · kg-1 and 0.33 ± 0.12 mg · kg-1 in LuvyCalcic Chernozems and Vorony-Calcic Chernozems, respectively, with a rather larger variation.
Author’s response: Thanks for your advice. We made the appropriate changes to the manuscript.
Page 6
No significant influence of the investigated physico-chemical properties on the concentration of mobile Mn in soil was observed.
No significant influence of the investigated physico-chemical properties on the concentration of mobile Mn was observed in the soils.
Author’s response: Thanks for your corrections. We made the appropriate changes to the manuscript.
Page 7
Figure 3. Pearson's correlation matrix: correlation coefficients between soil and plant variables. Bold values are statistically significant (p < 0.05). The abbreviations are the same as in Table 1 and Table 2.
Figure 3. Pearson correlation matrix: correlation coefficients between soil and plant variables. Bold values are statistically significant (p < 0.05). The abbreviations are the same as in Tables 1 and 2.
Author’s response: Thanks for your corrections. We made the appropriate changes to the manuscript.
Page 7
Table 3 illustrates the significant variation in soil Cu concentrations.
The significant variation in soil Cu concentrations is evident in Table 3.
Author’s response: Thanks for your suggestion. We changed structure of the sentence in the manuscript.
Page 8
Table 4 illustrates the differences in Se concentrations in aboveground plant tissues and its bioaccumulation among crops (sunflower, wheat) and wild plant species (couch grass).
The differences in Se concentrations in aboveground plant tissues and its bioaccumulation among crops (sunflower, wheat) and wild plant species (couch grass) are shown in Table 4.
Author’s response: Thanks for your suggestion. We changed structure of the sentence.
Page 8
Sunflower had the highest Se accumulation capacity among the plants studied.
Sunflower had the highest Se accumulation capacity among the studied plants.
Author’s response: Thanks for your corrections. We rearranged the words at the end of the sentence.
Page 8
Conversely, no relationship was found between the water-soluble Se and its concentration in plants (Figure 3).
Oppositely, no relationship was found between the water-soluble Se and its concentration in plants (Figure 3).
Author’s response: Thanks for your suggestion. We changed the word in the manuscript.
Page 8
Figure 4. Pearson correlation of between total Se in soils and Se concentrations in plant tissues.
Figure 4. Pearson correlation between total Se in soils and Se concentrations in plant tissues.
Author’s response: We are very sorry for our technical mistake. We deleted “of” in the manuscript.
Page 8
Moreover, according to Kruskal Wallis ANOVA the BAF values were significantly higher for Fluvisols (p < 0.05) compared to Chernozem soils.
Please correct this sentence for clarity.
Author’s response: We are very sorry for our unclear writing. We made a correction of the sentence:
Moreover, statistical analysis using Kruskal–Wallis ANOVA proved that BAFs were significantly higher for plants growing on Fluvisols (p < 0.05) compared to those on Chernozem soils.
Page 11
Therefore, our results were consistent with those reported in other studies.
Therefore, our results are consistent with those reported in other studies.
Author’s response: Thanks for your correction. We made the appropriate changes to the manuscript.
Page 11
Regarding the average Se and HMs content in plants, there were no significant differences in element concentrations except for Se in sunflower and Zn in wheat, which were the highest.
Regarding the average Se and HMs content in plants, there were no significant differences in element concentrations, except for Se in sunflower and Zn in wheat, which were the highest.
Author’s response: Thanks for your correction. We made the appropriate changes to the manuscript.
We sincerely thank you for your corrections and advices that greatly help us to improve the manuscript.
With best regards,
Sheshnitsan Sergey
Corresponding author
Author Response File: Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsThe work submitted for review is very extensive. Written in correct language and well developed graphically. However, doubts are raised by the subject matter of the research, which in my opinion is neither innovative nor very extensive. Experience contains practically only one factor. The purpose of the research in question should be more emphasized. The thesis should also be written on the basis of contemporary literature and not from 20 years ago. I would like to ask you to expand the number of them.
Author Response
Responses to Reviewer 2
Dear Reviewer,
Thanks for your comments concerning our manuscript entitled “Selenium and Heavy Metals in Soil–Plant System in a Hydro-geochemical Province with High Selenium Content in Groundwater: A Case Study of the Lower Dniester Valley” (Manuscript ID: soilsystems-2714602). Those comments are all valuable and very helpful for revising and improving our paper. We have studied the comments carefully and tried our best to improve the manuscript. Revised portions are marked in red in the manuscript.
The responses to your comments are as follows:
The work submitted for review is very extensive. Written in correct language and well developed graphically. However, doubts are raised by the subject matter of the research, which in my opinion is neither innovative nor very extensive. Experience contains practically only one factor. The purpose of the research in question should be more emphasized. The thesis should also be written on the basis of contemporary literature and not from 20 years ago. I would like to ask you to expand the number of them.
Author’s response: Thank you very much for the meaningful and constructive comments. We added several recent references in the manuscript:
Golubkina, N.; Sheshnitsan, S.; Kapitalchuk, M. Ecological Importance of Insects in Selenium Biogenic Cycling. Int. J. Ecol. 2014, 2014, 1–6. https://doi.org/10.1155/2014/835636.
Golubkina, N. A.; Sheshnitsan, S. S.; Kapitalchuk, M. V.; Erdenotsogt, E. Variations of Chemical Element Composition of Bee and Beekeeping Products in Different Taxons of the Biosphere. Ecol. Indic. 2016, 66, 452–457. https://doi.org/10.1016/j.ecolind.2016.01.042.
Golubkina, N. A.; Kapitalchuk, M. V.; Sheshnitsan, S. S.; Grishina, T. L.; Kapitalchuk, I. P. Selenium Accumulation by Mushrooms of the Dniester River Valley. Trace Elem. Med. Mosc. 2014, 15 (3), 19–26.
Kapitalchuk, M. V.; Golubkina, N. A.; Kapitalchuk, I. P. Hair Concentrations of Selenium in the Moldovan Population. Ekol. Cheloveka Hum. Ecol. 2023, 30 (5), 363–373. https://doi.org/10.17816/humeco217703.
Botnaru, V.; Mirlean, N.; Quintana, G. C. R. Informative Eco-Geochemical Assessment of Soil Layer Pollution in Chisinau during the Peak Period of Industrial Activity. Bull. Inst. Geol. Seismol. 2022, No. 1, 33–40. https://doi.org/10.54326/1857-0046.21.1.04.
Zubcov, E.; Zubcov, N. The Dynamics of the Content and Migration of Trace Metals in Aquatic Ecosystems of Moldova. E3S Web Conf. 2013, 1, 32009. https://doi.org/10.1051/e3sconf/20130132009.
Zinicovscaia, I.; Hramco, C.; Duliu, O. G.; Vergel, K.; Culicov, O. A.; Frontasyeva, M. V.; Duca, G. Air Pollution Study in the Republic of Moldova Using Moss Biomonitoring Technique. Bull. Environ. Contam. Toxicol. 2017, 98 (2), 262–269. https://doi.org/10.1007/s00128-016-1989-y.
Zinicovscaia, I.; Duliu, O.; Culicov, O. A.; Frontasyeva, M.; Sturza, R. Major and Trace Elements Distribution in Moldavian Soils. Romanian Rep. Phys. 2018, 70, 1–10.
Zinicovscaia, I.; Sturza, R.; Duliu, O.; Grozdov, D.; Gundorina, S.; Ghendov-Mosanu, A.; Duca, G. Major and Trace Elements in Moldavian Orchard Soil and Fruits: Assessment of Anthropogenic Contamination. Int. J. Environ. Res. Public. Health 2020, 17 (19), 7112. https://doi.org/10.3390/ijerph17197112.
We sincerely thank you for your advices that greatly help us to improve the manuscript.
With best regards,
Sheshnitsan Sergey
Corresponding author
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsDear Authors,
reading and understanding this manuscript has been a pleasure for me. This work allows to give temporal continuity to the studies carried out on heavy metals in this valley. The writing is very careful and scientifically rigorous. The description of the material and methods used is clear and concise.
After reviewing the manuscript I have not found any relevant comments to make you. However, I would like to point out one detail. In Table 1, line 182, shown SD of two decimal places. Do you want to emphasize the accuracy of the measuring instrument? I understand that if it were for statistical calculation they would only express SD value to one decimal place.
Best regards.
Author Response
Responses to Reviewer 3
Dear Reviewer,
Thanks for your comments concerning our manuscript entitled “Selenium and Heavy Metals in Soil–Plant System in a Hydro-geochemical Province with High Selenium Content in Groundwater: A Case Study of the Lower Dniester Valley” (Manuscript ID: soilsystems-2714602). Those comments are all valuable and very helpful for revising and improving our paper. We have studied the comments carefully and tried our best to improve the manuscript.
The responses to your comments are as follows:
Dear Authors,
reading and understanding this manuscript has been a pleasure for me. This work allows to give temporal continuity to the studies carried out on heavy metals in this valley. The writing is very careful and scientifically rigorous. The description of the material and methods used is clear and concise.
Author’s response: Thank you very much for your appreciation of our research
After reviewing the manuscript I have not found any relevant comments to make you. However, I would like to point out one detail. In Table 1, line 182, shown SD of two decimal places. Do you want to emphasize the accuracy of the measuring instrument? I understand that if it were for statistical calculation they would only express SD value to one decimal place.
Best regards.
Author’s response: You are absolutely right, because the accuracy of pH measurments using pH-meter WTW pH 3110 SET 2 with a SenTix 41 pH was ±0.005. Therefore, the mean and standard deviation did not exceed the precision of the measurements in the raw data in our study according to recommendations for scientific reports [Habibzadeh F, Habibzadeh P. How much precision in reporting statistics is enough? Croat Med J. 2015 Oct;56(5):490-2. doi: 10.3325/cmj.2015.56.490].
With best regards,
Sheshnitsan Sergey
Corresponding author
Author Response File: Author Response.pdf
Reviewer 4 Report
Comments and Suggestions for AuthorsThe review of “Selenium and Heavy Metals in Soil–Plant System in a Hydrogeochemical Province with High Selenium Content in Groundwater: A Case Study of the Lower Dniester Valley” for Soil Systems MDPI.
The topic of manuscript fits within the scope of the journal Soil Systems MDPI. This article is of interest from the point of view of analyzing the bioaccumulation of selenium and heavy metals in plants, as this relates to the state of plants and human nutrition. Studying the factors influencing selenium accumulation in plants could have important implications for agricultural practices and human health in regions where soils are rich in selenium.
Nevertheless, several problems/doubts should be solved before the manuscript is suitable to be published.
Specific comments:
1. Introduction
1.1. L 57-58: What does the "n" stand for? (0.n – n·10 μg · l–1).
1.2. L 61-62: What document regulates the maximum permitted value of selenium? It may be necessary to add a reference to a literary source.
1.3. L 66-67: Please specify. Optimal content Se for plants?
2. Materials and Methods
2.1. L 111-114: I recommend adding the Latin names of plant species. What is the rationale for this choice of plants for research?
3. Results
3.1. L 218-219: Please check that the reference to the figure (Figure 3 (a)) is correct.
3.2. L 218-238: I recommend identically rounding decimal fractions when specifying the correlation coefficient. The text shows three decimal places (r = 0.845), and Figure 3 shows two decimal places (r = 0.84).
3.2. L 302-303: Table 4 shows that different plant species have different abilities to accumulate selenium. Perhaps it would be correct to additionally consider the relationship between the selenium content in the plant and the total selenium content in the soil for each plant species separately, as a reflection of the species-specific nature of the bioaccumulation of this element.
Author Response
Responses to Reviewer 4
Dear Reviewer,
Thanks for your comments concerning our manuscript entitled “Selenium and Heavy Metals in Soil–Plant System in a Hydro-geochemical Province with High Selenium Content in Groundwater: A Case Study of the Lower Dniester Valley” (Manuscript ID: soilsystems-2714602). Those comments are all valuable and very helpful for revising and improving our paper. We have studied the comments carefully and tried our best to improve the manuscript. Revised portions are marked in red in the manuscript.
The responses to your comments are as follows:
The review of “Selenium and Heavy Metals in Soil–Plant System in a Hydrogeochemical Province with High Selenium Content in Groundwater: A Case Study of the Lower Dniester Valley” for Soil Systems MDPI.
The topic of manuscript fits within the scope of the journal Soil Systems MDPI. This article is of interest from the point of view of analyzing the bioaccumulation of selenium and heavy metals in plants, as this relates to the state of plants and human nutrition. Studying the factors influencing selenium accumulation in plants could have important implications for agricultural practices and human health in regions where soils are rich in selenium.
Nevertheless, several problems/doubts should be solved before the manuscript is suitable to be published.
Author’s response: Thank you very much for your appreciation of our research
Specific comments:
- Introduction
1.1. L 57-58: What does the "n" stand for? (0.n – n·10 μg · l–1).
Author’s response: "n" means the common in geochemistry abbreviation of concentration level of the chemical element. "n" can be substituted at any number (1, 2, 3 and so on).
1.2. L 61-62: What document regulates the maximum permitted value of selenium? It may be necessary to add a reference to a literary source.
Author’s response: This value (10 μg · l–1) was set by World Health Organization Guidelines both for the drinking and irrigation water. Information in lines 59-62 was cited according to [Hannigan et al., 2006] data, and therefore we did not add a reference. We added the missing reference as you advised:
World Health Organization. Guidelines for Drinking-Water Quality: Fourth Edition Incorporating the First Addendum; 2017.
1.3. L 66-67: Please specify. Optimal content Se for plants?
Author’s response: What is meant here is not the optimum Se level for plants, but the optimum level of total Se content in soils according to established reference threshold values for the risk assessment of the potential Se deficiency of soils and the excess of Se in soils [Tan, J.; Zhu, W.; Wang, W.; Li, R.; Hou, S.; Wang, D.; Yang, L. Selenium in Soil and Endemic Diseases in China. Science of The Total Environment 2002, 284 (1–3), 227–235. https://doi.org/10.1016/S0048-9697(01)00889-0].
- Materials and Methods
2.1. L 111-114: I recommend adding the Latin names of plant species. What is the rationale for this choice of plants for research?
Author’s response: The authors highly appreciate your valuable advice. Latin names of plants were included in the revised version in the corresponding part. The choice of plants for research was based on the fact that wheat and sunflower are the most commonly grown crops in the study area, and couch grass is the most typical cereal plant, dominating the herbage composition at all sampling sites.
- Results
3.1. L 218-219: Please check that the reference to the figure (Figure 3 (a)) is correct.
Author’s response: The authors appreciated that you pointed out this mistake. We corrected it.
3.2. L 218-238: I recommend identically rounding decimal fractions when specifying the correlation coefficient. The text shows three decimal places (r = 0.845), and Figure 3 shows two decimal places (r = 0.84).
Author’s response: Your inspective recommendation is sincerely appreciated. We included updated figure 3 in the manuscript.
3.2. L 302-303: Table 4 shows that different plant species have different abilities to accumulate selenium. Perhaps it would be correct to additionally consider the relationship between the selenium content in the plant and the total selenium content in the soil for each plant species separately, as a reflection of the species-specific nature of the bioaccumulation of this element.
Author’s response: Your concerns about consideration the relationship between the selenium content in the plant and the total selenium content in the soil for each plant species separately are very valuable and reasonable. But we should mention that there were no substantial differences in this relationship among three plant species. Therefore, we integrated all the data into a single regression for demonstration of common trend.
We sincerely thank you for your corrections and advices that greatly help us to improve the manuscript.
With best regards,
Sheshnitsan Sergey
Corresponding author
Author Response File: Author Response.pdf
Reviewer 5 Report
Comments and Suggestions for AuthorsPlease see separate file: Soilsystems 2714602.docx
Comments for author File: Comments.pdf
Author Response
Responses to Reviewer 5
Dear Reviewer,
Thanks for your comments concerning our manuscript entitled “Selenium and Heavy Metals in Soil–Plant System in a Hydro-geochemical Province with High Selenium Content in Groundwater: A Case Study of the Lower Dniester Valley” (Manuscript ID: soilsystems-2714602). Those comments are all valuable and very helpful for revising and improving our paper. We have studied the comments carefully and tried our best to improve the manuscript. Revised portions are marked in red in the manuscript.
The responses to your comments are as follows:
- Abstract:
Water-soluble Se (0.09 ± 0.03 mg · kg-1) in 22 soils was higher by 27% than the total Se (0.33 ± 0.13 mg · kg-1) and increased with rising the total 23 Se content (r = 0.845).
Please phrase unequivocally:0.09 is not higher than 0.33
Author’s response: We are very sorry for our unclear writing. We made a correction of the sentence: “Water-soluble Se (0.09 ± 0.03 mg · kg–1) in soils was 32.1% of the total Se (0.33 ± 0.13 mg · kg–1) and increased with rising the total Se content (r = 0.845)”.
- Please mentioned "the favorable conditions for Se uptake". Must be water soluble Se only.
Author’s response: We were not able to confirm the presence of close relationship between water soluble selenium and its content in plants, as well as its accumulation: the correlation was weak and statistically insignificant (see Figure 3). At the same time, such a relationship was shown for total selenium in soils.
- Aims not achieved. “We assumed that high Se levels in groundwater may promote increased Se concentration in soils and its bioaccumulation in plants”. From the sentence per se and after reading the manuscript it remains dubious how this can occur: Normally water for soil-water interaction in the first 30 cm of top soil is supplied by rain/mainly by rain and even if the plant roots grow deeper into soil they normally do not reach groundwater levels. Are deep wells with groundwater supply used for irrigation?
Author’s response:
The aim of the study was to determine the level of Se accumulation in soils and plants as well as to identify the factors associated with Se bioaccumulation in hydrogeochemical province with high Se concentrations. Our general hypothesis for the extensive study is that high Se concentrations in groundwater may contribute to increased Se concentrations in soils and its bioaccumulation by plants. For this study, we only focused on the soil-plant system in the conditions of a hydrogeochemical province. But we've found a few facts that indirectly prove this hypothesis. Soils formed on low relief areas where the groundwater is close to the surface, such as on low terraces, in the floodplains (e.g., Luvisols) of rivers and lakes and in drainless depressions, tend to have a higher selenium content. Significant amounts of soil formation products from eluvial landscapes can also accumulate here as well as hydrogenic accumulation phenomena can occur.
- Introduction: Why should heavy metal uptake should be antagonistically if special uptake systems may be active in the same/different plants?
Author’s response: According to generally accepted data, all considered metals can be antagonists of selenium in the soil-plant system [Kabata-Pendias, 2010]. However, this effect was not observed in our study.
- Line77,78: “Firstly, Mn, Cu, and Zn are essential for plant, animal, and human nutrition in certain concentrations [14].“ This is not correct. There are medical products/ food additives on the market only for trace supply of selenium.
Author’s response: The essentiality of manganese, zinc, and copper for plants, animals, and humans has been established for a long time. There are many biologically active additives and medical products available on the market that provide not only selenium but also these micronutrients supply.
- M&M: Study area:
Line 94: What does "shallow groundwater levels mean? At what depth starts the groundwater level during the vegetation season? Please argue more discrete with numbers.
Author’s response: Shallow groundwater refers to the water that is found in the uppermost layer of the Earth's surface, typically within the first few meters below the ground. Interactions of shallow groundwater and the terrestrial land surface are widely recognized. It provides additional moisture to the root zone of soil via capillary fluxes. For more detailed information, see [Soylu, Bras, 2023; doi: 10.1016/j.dib.2023.108973.]. The depth of shallow groundwater table varies depending on the relief form, season of the year and precipitation levels and ranges from 0.3 to 2.0 m in the floodplain
- Field studies and sample preparation: Nothing is said in which season samples have been taken (I guess in fall?) and nothing is said about soil/weather conditions and groundwater levels at the sampling sites.
Author’s response: Thank you for your comment. The study was conducted in the second half of the vegetation season during July and August. We have incorporated this information into the text of the manuscript. General features of soil cover and climate were given in subsection 2.1
- Why using 1 m steel augers if only 30 cm top soil are used?
Author’s response: A soil auger was used to collect quickly 7-10 individual soil samples at each sampling site, which were then mixed to form a combined soil sample. Unfortunately, the design of the soil auger does not allow it to be shorter than 1 m.
- It would be necessary to inform the reader about soil moisture contents, the soluble heavy metal ion content in the soil and the soil moisture (at the oxidation/reduction state of the location, oxygen concentration/supply for plants in soil, etc. This would be essential since especially selenite and selenate are highly redox sensitive (e.g. by microbial activity) and have different solubility in aquous environment.)
Author’s response: Thank you very much for your highly valuable comment. Certainly, these are extremely important physicochemical parameters for the assessment of selenium mobility in soils. In this study we did not consider specific forms of selenium in soils. This aspect will be studied in the future.
- The 16 soil samples apparently represent 4 soil types and it is not clear which samples represent which soil type or number of sample and which vegetation was grown on them (which of the three plants is grown on which soil type (number of soil sample).
Author’s response: Total combined soil samples in this study was 42. The most expressive patterns of bioaccumulation depending on soil types were revealed on the example of couch grass (see Figure 5), as it, unlike crops, was observed at all sampling sites. For the other plants, only general levels of selenium and metal content and accumulation were assessed.
- Twenty seven to 32 % of the selenium can be transferred into soil water (line 383) but it is not mentioned under which conditions (just by washing soil with water or acid or alkaline treatment, lowering pH, heat treatment?). How was solubility tested/achieved?
Author’s response: This information was provided in subsection “2.3. Chemical Analysis and Extraction”. Water-soluble (WS) Se, a form of exchangeable Se in soil, was extracted using deionized water with a soil to water ratio of 1 : 5 in a hot-water bath for 1 hour [according to Gupta, Hettiarachchi, 2007].
- It would be of interest how much was soluble in soil with low or high SOC and whether these soils were mainly dry or wet during the year. Bacterial activity in these soils?
Author’s response: Thank you very much for your highly valuable comment. We will take your expert advice into account in our upcoming research and try to provide answers to the questions raised.
- Geological/chemical or biological oxidation/reduction conditions, etc. Unfortunately it was not tested whether water solubility was different on soils with high or low SOC and selenium absorption capacity. Also, the grain structure of the soils may be important but was not determined.
Author’s response: Thank you very much for your constructive advice. Certainly, these are extremely important physicochemical parameters for the assessment of selenium mobility in soils as mentioned above.
- What was the main "selenium source" in soil: Solid minerals or selenium salts that were ab./adsorbed to minerals or SOC?
Author’s response: Thank you very much again for your highly valuable comment. Further research is needed to definitively answer this question and detailed study of selenium speciation in soils.
- If high selenium concentrations in groundwater promotes selenium concentrations in soil, then almost all Se of the soils should be water extractable, not only 32 %. Or was it precipitated by oxidation to insoluble selenates?
Author’s response: Soil processes are quite complex and significantly influence the immobilisation not only of selenium but also of other elements. Mobility is highly dependent on CEC, SOC content, CaCO3 content, pH, Eh and many other local physico-chemical properties of soils, so it is obvious that not all selenium enters the soil solution. To answer the question of the reasons for the decrease in selenium mobility in soils, it is necessary to study its forms in soils.
- Did the test plants accumulate SE to a different concentration and at which vegetation state?
Author’s response: Plants were sampled at the mature stage in their natural growing conditions with local levels of selenium content in soils. Unfortunately, we did not test plants at different concentrations under controlled experimental conditions.
- Lines 429-434 in the conclusion may be right, but none of the mentioned arguments was investigated in this paper. They can only be drawn from literature reports by others.
Author’s response: Thank you very much for comment. In conclusion, the main generalizations and conclusions that we were able to find out during this study are presented. The need for further research is particularly emphasized to answer questions regarding the reasons for the high mobility of Se and significant content of its water-soluble forms in soils
- Lines 112,113: Cultivated annual (sunflowers, wheat) and uncultivated annual weed plant material (couch grass, fresh or also from the fore-year?) were apparently combined.
Author’s response: Definitely not, the different plant species were not combined into one sample and analyzed separately from each other. Note the data in Table 4. Only abovefround plant organs from the current year were sampled. Dead parts from previous years were not included in the sample.
- Is heavy metal ion uptake (and accumulation) in the three test plants the same?
Author’s response: According to statistical calculations, the content of metals may vary between species (e.g. Zn), while differences in bioaccumulation between species could not be confirmed by statistical analysis.
- Line173:" ..were calculated..."
Author’s response: Thank you for pointing out the mistake. The authors corrected it in the manuscript.
- In the conclusions no word is lost as to the toxicity level of Se in the 4 investigated plants: Legal boundary levels, actual levels in the 4 plants and health risks when using this water for plant irrigation (if necessary in the region) and for drinking water (prepared from surface water or groudwater).
Overall the manuscript is not satisfying and leaves many questions open. What is the heavy metal burden by local geochemical soil composition/ by accumulation with rainwater transfer from upstream regions/ by human general activity/ by heavy metal polluting industry/ etc.?
Author’s response: Our study highlights for the first time the issue of selenium mobility in soils of the Lower Dniester Valley, and certainly many questions remain to be answered.
The authors sincerely thank you for your corrections and advices that greatly help us to improve the manuscript.
Author Response File: Author Response.pdf
Reviewer 6 Report
Comments and Suggestions for AuthorsThe submitted manuscript entitled: «Selenium and Heavy Metals in Soil–Plant System in a Hydrogeochemical Province with High Selenium Content in Groundwater: A Case Study of the Lower Dniester Valley» is scientifically interesting.
It is well written with a proper structure, coherent experiments, and interesting conclusions. However, there are some points that need to be modified and improved.
1) Abstract needs to be more informative and to point out innovation potential more clearly.
2) Line 20: Authors should refer to the chemical elements either by their position in the Periodic Table of the Elements or alphabetically.
3) Lines 22-24: This sentence is wrongly worded. It should be rewritten. It contradicts the sentence in the Discussion section on lines 377-378.
4) The keywords should not repeat the words in the title. Any common words should be removed.
5) Line 46: Authors should replace the bibliographic references [3,4,8,9,10] with [3-4, 8-10]. They should follow this format in the rest of the manuscript.
6) Lines 48-54: If authors use the word "Firstly" they should continue in the next sentence with the word "Secondly", in order to make a clear meaning to the reader.
7) Lines 79-83: «Secondly, they serve …. within ecosystems [15]». The sentence is quite vague. Please rewrite it in a more understandable way.
8) Line 191: Authors should be a little more careful when interpreting the results of the table. In Table 1 (line 182) it is mentioned that the soil type Vorony-Calcic Chernozems has the lowest content of exchangeable Cations Ca2++Mg2+ [18.2 mg (eq) - 100 g-1] and not the soil type Luvy-Calcic Chernozems mentioned in the manuscript.
9) Authors should be more precise when referring to figures in the manuscript. Line 219 refers to Figure 3 (a) which is not in the manuscript, but Figure 2 is. It should be replaced.
10) Line 326: The word "coach" should be replaced with the word "couch".
11) Figure 5, line 328: In this figure, the letters a, b and c should be entered for the statistically significant or not differences, as indicated in the tables in the manuscript.
12) Lines 400-403: The units of measurement mg kg-1 are missing the «soil» definition. It should be replaced by «mg kg-1 soil».
Author Response
Responses to Reviewer 6
Dear Reviewer,
Thanks for your comments concerning our manuscript entitled “Selenium and Heavy Metals in Soil–Plant System in a Hydro-geochemical Province with High Selenium Content in Groundwater: A Case Study of the Lower Dniester Valley” (Manuscript ID: soilsystems-2714602). Those comments are all valuable and very helpful for revising and improving our paper. We have studied the comments carefully and tried our best to improve the manuscript. Revised portions are marked in red in the manuscript.
The responses to your comments are as follows:
The submitted manuscript entitled: «Selenium and Heavy Metals in Soil–Plant System in a Hydrogeochemical Province with High Selenium Content in Groundwater: A Case Study of the Lower Dniester Valley» is scientifically interesting.
It is well written with a proper structure, coherent experiments, and interesting conclusions. However, there are some points that need to be modified and improved.
Author’s response: Thank you very much for your appreciation of our research
1) Abstract needs to be more informative and to point out innovation potential more clearly.
Author’s response: Thanks for your advice. We made the appropriate changes to the manuscript.
2) Line 20: Authors should refer to the chemical elements either by their position in the Periodic Table of the Elements or alphabetically.
Author’s response: Thanks for your advice. We made the appropriate changes to the manuscript.
3) Lines 22-24: This sentence is wrongly worded. It should be rewritten. It contradicts the sentence in the Discussion section on lines 377-378.
Author’s response: We are very sorry for our unclear writing. We made a correction of the sentence:
Water-soluble Se (0.09 ± 0.03 mg · kg–1) in soils was 32.1% of the total Se (0.33 ± 0.13 mg · kg–1) and increased with rising the total Se content (r = 0.845)
4) The keywords should not repeat the words in the title. Any common words should be removed.
Author’s response: Thanks for your advice. We made the appropriate changes to the manuscript.
5) Line 46: Authors should replace the bibliographic references [3,4,8,9,10] with [3-4, 8-10]. They should follow this format in the rest of the manuscript.
Author’s response: Thanks for your advice. We corrected this format in the manuscript.
6) Lines 48-54: If authors use the word "Firstly" they should continue in the next sentence with the word "Secondly", in order to make a clear meaning to the reader.
Author’s response: Thanks for your advice. We made the appropriate changes to the manuscript.
7) Lines 79-83: «Secondly, they serve …. within ecosystems [15]». The sentence is quite vague. Please rewrite it in a more understandable way.
Author’s response: Thanks for your advice. We made the appropriate changes to the sentence:
“Secondly, these elements have a higher affinity to accumulate in living organisms in the geochemical landscapes of the Lower Dniester Valley than their water migration ability.”
8) Line 191: Authors should be a little more careful when interpreting the results of the table. In Table 1 (line 182) it is mentioned that the soil type Vorony-Calcic Chernozems has the lowest content of exchangeable Cations Ca2++Mg2+ [18.2 mg (eq) - 100 g-1] and not the soil type Luvy-Calcic Chernozems mentioned in the manuscript.
Author’s response: We are very sorry for our incorrect writing. We made a correction of the sentence.
9) Authors should be more precise when referring to figures in the manuscript. Line 219 refers to Figure 3 (a) which is not in the manuscript, but Figure 2 is. It should be replaced.
Author’s response: We are very sorry for our technical mistake. We made the appropriate change to the manuscript.
10) Line 326: The word "coach" should be replaced with the word "couch".
Author’s response: We are very sorry for our technical mistake. We made the appropriate change to the manuscript.
11) Figure 5, line 328: In this figure, the letters a, b and c should be entered for the statistically significant or not differences, as indicated in the tables in the manuscript.
Author’s response: Thanks for your advice. We made the appropriate changes to the figure 5
12) Lines 400-403: The units of measurement mg kg-1 are missing the «soil» definition. It should be replaced by «mg kg-1 soil».
Author’s response: Thanks for your advice. We made the appropriate changes to the manuscript.
We sincerely thank you for your corrections and advices that greatly help us to improve the manuscript.
With best regards,
Sheshnitsan Sergey
Corresponding author
Author Response File: Author Response.pdf
Round 2
Reviewer 5 Report
Comments and Suggestions for AuthorsAll essential comments were not answered (mostly like will be done in future research.
Comments on the Quality of English LanguageEnglish seems to be o.k.
Author Response
Dear Reviewer,
Thanks for your comments concerning our manuscript entitled “Selenium and Heavy Metals in Soil–Plant System in a Hydro-geochemical Province with High Selenium Content in Groundwater: A Case Study of the Lower Dniester Valley” (Manuscript ID: soilsystems-2714602). We have tried our best to improve the manuscript according your comments. Revised portions are marked in red in the manuscript.
The responses to your comments are as follows:
- Abstract:
Water-soluble Se (0.09 ± 0.03 mg · kg-1) in 22 soils was higher by 27% than the total Se (0.33 ± 0.13 mg · kg-1) and increased with rising the total 23 Se content (r = 0.845).
Please phrase unequivocally:0.09 is not higher than 0.33
Author’s response: We are very sorry for our unclear writing. We made a correction of the sentence: “Water-soluble Se (0.09 ± 0.03 mg · kg–1) in soils was 32.1% of the total Se (0.33 ± 0.13 mg · kg–1) and increased with rising the total Se content (r = 0.845)”.
- Please mentioned "the favorable conditions for Se uptake". Must be water soluble Se only.
Author’s response: The correlation between water soluble selenium and its content in plants, as well as its accumulation, was weak and statistically insignificant (see Figure 3). However, the mentioned relationship was shown for total selenium in soils.
- Aims not achieved. “We assumed that high Se levels in groundwater may promote increased Se concentration in soils and its bioaccumulation in plants”. From the sentence per se and after reading the manuscript it remains dubious how this can occur: Normally water for soil-water interaction in the first 30 cm of top soil is supplied by rain/mainly by rain and even if the plant roots grow deeper into soil they normally do not reach groundwater levels. Are deep wells with groundwater supply used for irrigation?
Author’s response:
The aim of the study was to determine the level of Se accumulation in soils and plants as well as to identify the factors associated with Se bioaccumulation in hydrogeochemical province with high Se concentrations. Our general hypothesis for the extensive study is that high Se concentrations in groundwater may contribute to increased Se concentrations in soils and its bioaccumulation by plants. For this study, we only focused on the soil-plant system in the conditions of a hydrogeochemical province, and we found a few facts that indirectly prove this hypothesis. Soils formed on low relief areas where the groundwater is close to the surface, such as on low terraces, in the floodplains (e.g., Luvisols) of rivers and lakes and in drainless depressions, tend to have a higher selenium content compared to ... Significant amounts of soil formation products from eluvial landscapes can also accumulate here as well as hydrogenic accumulation phenomena can occur.
- Introduction: Why should heavy metal uptake should be antagonistically if special uptake systems may be active in the same/different plants?
Author’s response: According to previous literature reports, all the metals analyzed in our work are potential antagonists of selenium in the soil-plant system [Kabata-Pendias, 2010]. However, this effect was not observed in our study.
- Line77,78: “Firstly, Mn, Cu, and Zn are essential for plant, animal, and human nutrition in certain concentrations [14].“ This is not correct. There are medical products/ food additives on the market only for trace supply of selenium.
Author’s response: The essentiality of manganese, zinc, and copper for plants, animals, and humans has been established for a long time. There are many biologically active additives and medical products available on the market that provide not only selenium but also these micronutrients.
- M&M: Study area:
Line 94: What does "shallow groundwater levels mean? At what depth starts the groundwater level during the vegetation season? Please argue more discrete with numbers.
Author’s response: Shallow groundwater refers to the water that is found in the uppermost layer of the Earth's surface, typically within the first few meters below the ground. Interactions of shallow groundwater and the terrestrial land surface are widely recognized. Shallow groundwater provides additional moisture to the soil root zone via capillary fluxes. For more detailed information, please see [Soylu, Bras, 2023; doi: 10.1016/j.dib.2023.108973.]. The depth of shallow groundwater table varies depending on the relief form, season of the year and precipitation levels, and ranges from 0.3 to 2.0 m in the floodplain.
Additional text was added in the subsection 2.1: “The depth of the groundwater table in the Pleistocene terraces of the Dniester River varies significantly, usually ranging from 10 to 15 meters. In the Dniester floodplains, the groundwater level is typically set between 0.5 and 8 meters, depending on the fluctuations of the Dniester River, and is susceptible to flooding’’
- Field studies and sample preparation: Nothing is said in which season samples have been taken (I guess in fall?) and nothing is said about soil/weather conditions and groundwater levels at the sampling sites.
Author’s response: Thank you for your comment. The study was conducted in the second half of the vegetation season in July and August. We have incorporated this information into the text of the manuscript. General features of soil cover and climate were given in subsection 2.2.
- Why using 1 m steel augers if only 30 cm top soil are used?
Author’s response: A soil auger was used to collect quickly 7-10 individual soil samples at each sampling site, which were then mixed to form a combined soil sample. Unfortunately, the shape of the soil auger does not allow it to be shorter than 1 m.
- It would be necessary to inform the reader about soil moisture contents, the soluble heavy metal ion content in the soil and the soil moisture (at the oxidation/reduction state of the location, oxygen concentration/supply for plants in soil, etc. This would be essential since especially selenite and selenate are highly redox sensitive (e.g. by microbial activity) and have different solubility in aquous environment.)
Author’s response: Thank you very much for your highly valuable comment. Certainly, these are extremely important physicochemical parameters for the assessment of selenium mobility in soils. In this study we did not examine specific forms of selenium in soils. According to previous literature reports, we added the following text in the manuscript: “Considering the slightly alkaline nature of soil solutions, the relatively low SOC content and the significant cation exchange capacity of soils, selenates, selenites and ligand-exchangeable organoselenium compounds are expected to be readily available for plant uptake.”
- The 16 soil samples apparently represent 4 soil types and it is not clear which samples represent which soil type or number of sample and which vegetation was grown on them (which of the three plants is grown on which soil type (number of soil sample).
Author’s response: The total combined soil samples in this study was 42. The most expressive patterns of bioaccumulation depending on soil types were revealed on the example of couch grass (see Figure 5), as the latter, unlike crops, was observed at all sampling sites. For the other plants, only general levels of selenium and metal content and accumulation were assessed. We also indicated the number of samples in Table 4 and Figure 5 of the manuscript.
- Twenty seven to 32 % of the selenium can be transferred into soil water (line 383) but it is not mentioned under which conditions (just by washing soil with water or acid or alkaline treatment, lowering pH, heat treatment?). How was solubility tested/achieved?
Author’s response: This information was provided in subsection “2.3. Chemical Analysis and Extraction”. Water-soluble (WS) Se, a form of exchangeable Se in soil, was extracted using deionized water with a soil to water ratio of 1:5 in a hot-water bath for 1 hour [according to Gupta, Hettiarachchi, 2007].
- It would be of interest how much was soluble in soil with low or high SOC and whether these soils were mainly dry or wet during the year. Bacterial activity in these soils?
Author’s response: Thank you very much for your highly valuable comment. We will take your expert advice into account in our upcoming research, to examine the mentioned further aspects of the broad topic studied.
- Geological/chemical or biological oxidation/reduction conditions, etc. Unfortunately it was not tested whether water solubility was different on soils with high or low SOC and selenium absorption capacity. Also, the grain structure of the soils may be important but was not determined.
Author’s response: Thank you very much for your constructive advice. Certainly, these are extremely important physicochemical parameters for the assessment of selenium mobility in soils as mentioned above. We analyzed soil texture only qualitatively (see Table 1).
- What was the main "selenium source" in soil: Solid minerals or selenium salts that were ab./adsorbed to minerals or SOC?
Author’s response: The primary source of selenium in soils is parent rocks containing selenium compounds. However, considering that only surface soil horizons were studied, soil organic matter (SOM) also plays an important role as a source of exchangeable forms of selenium. This confirms the positive correlation of total selenium with SOC and mobile Se.
- If high selenium concentrations in groundwater promotes selenium concentrations in soil, then almost all Se of the soils should be water extractable, not only 32 %. Or was it precipitated by oxidation to insoluble selenates?
Author’s response: Soil processes are quite complex and significantly influence the immobilization not only of selenium but also of other elements. Mobility is highly dependent on CEC, SOC content, CaCO3 content, pH, Eh and many other local physico-chemical properties of soils, so that not all selenium enters the soil solution. It was also found in previous study [Bogdevich et al., 2006; https://doi.org/10.1306/eg.02090504049] that the fraction of soluble and ligand-exchangeable organic and inorganic Se species was up to 24.5% of the total soil Se near Carpineni township, which is similar to the data obtained in the present study.
- Did the test plants accumulate SE to a different concentration and at which vegetation state?
Author’s response: Plants were sampled at the mature stage in their natural growing conditions with local levels of selenium content in soils, but we did not test plants at different concentrations under controlled experimental conditions.
- Lines 429-434 in the conclusion may be right, but none of the mentioned arguments was investigated in this paper. They can only be drawn from literature reports by others.
Author’s response: Thank you very much for comment. We have presented the main generalizations and conclusions that we found out during this study.
- Lines 112,113: Cultivated annual (sunflowers, wheat) and uncultivated annual weed plant material (couch grass, fresh or also from the fore-year?) were apparently combined.
Author’s response: The different plant species were not combined into one sample but analyzed separately from each other (the related data have been reported in Table 4. Only aboveground plant parts grown in the current year were sampled. Dead parts from previous years were not included in the sample.
- Is heavy metal ion uptake (and accumulation) in the three test plants the same?
Author’s response: According to statistical processing, the content of metals may vary between species (e.g., Zn), while differences in bioaccumulation between species were not confirmed by statistical analysis.
- Line173:" ..were calculated..."
Author’s response: Thank you for pointing out the mistake which we corrected it in the manuscript.
- In the conclusions no word is lost as to the toxicity level of Se in the 4 investigated plants: Legal boundary levels, actual levels in the 4 plants and health risks when using this water for plant irrigation (if necessary in the region) and for drinking water (prepared from surface water or groudwater).
Overall the manuscript is not satisfying and leaves many questions open. What is the heavy metal burden by local geochemical soil composition/ by accumulation with rainwater transfer from upstream regions/ by human general activity/ by heavy metal polluting industry/ etc.?
Author’s response: Our study focused on soil-plant system and highlights for the first time the issue of selenium mobility in soils of the Lower Dniester Valley. The hydrogeochemical aspects and health risks associated with the use of groundwater have been substantially observed in the cited references (e.g., Moraru C., 2014; https://doi.org/10.1007/978-3-319-02708-1_9; Hannigan, R. E.; Bogdevich, O. P.; Izmailova, D. N. 2006 https://doi.org/10.1306/eg.02090504049). Groundwater is not typically used for irrigation in the study region. Instead, farmers use water directly from the river.
To show the heavy metal burden by local geochemical soil composition we added table 5 in Discussions.
The authors sincerely thank you again for your corrections and advices that help us to improve the manuscript.
Author Response File: Author Response.pdf
Reviewer 6 Report
Comments and Suggestions for AuthorsThe authors of the manuscript have made minor corrections. They state in their report that the corrections have been made, while some are not in the manuscript. They do not indicate in their answers on which lines the corrections were made. Please re-check the previous comments and resend the manuscript, corrected.
Comments on the Quality of English LanguageThe authors of the manuscript have made minor corrections. They state in their report that the corrections have been made, while some are not in the manuscript. They do not indicate in their answers on which lines the corrections were made. Please re-check the previous comments and resend the manuscript, corrected.
Author Response
Dear Reviewer,
Thanks again for your comments concerning our manuscript entitled “Selenium and Heavy Metals in Soil–Plant System in a Hydro-geochemical Province with High Selenium Content in Groundwater: A Case Study of the Lower Dniester Valley” (Manuscript ID: soilsystems-2714602). We apologize for not being clear enough about the corrections made to the manuscript.
Those comments are all valuable and very helpful for revising and improving our paper. We have studied the comments carefully and tried our best to improve the manuscript. Revised portions are marked in yellow in the manuscript.
The responses to your comments are as follows:
The submitted manuscript entitled: «Selenium and Heavy Metals in Soil–Plant System in a Hydrogeochemical Province with High Selenium Content in Groundwater: A Case Study of the Lower Dniester Valley» is scientifically interesting.
It is well written with a proper structure, coherent experiments, and interesting conclusions. However, there are some points that need to be modified and improved.
Author’s response: Dear Reviewer, thank you very much for your appreciation of our research.
1) Abstract needs to be more informative and to point out innovation potential more clearly.
Author’s response: Thanks for your recommendation, we made the appropriate changes to the manuscript.
2) Line 20: Authors should refer to the chemical elements either by their position in the Periodic Table of the Elements or alphabetically.
Author’s response: Thanks for your advice, we addressed your comments in the manuscript.
3) Lines 22-24: This sentence is wrongly worded. It should be rewritten. It contradicts the sentence in the Discussion section on lines 377-378.
Author’s response: We are very sorry for our unclear writing. We made the following correction of the sentence:
Water-soluble Se (0.09 ± 0.03 mg · kg–1) in soils was 32.1% of the total Se (0.33 ± 0.13 mg · kg–1) and increased with rising the total Se content (r = 0.845).
4) The keywords should not repeat the words in the title. Any common words should be removed.
Author’s response: Thanks for your advice, we made the appropriate changes to the manuscript.
5) Line 46: Authors should replace the bibliographic references [3,4,8,9,10] with [3-4, 8-10]. They should follow this format in the rest of the manuscript.
Author’s response: Thanks for your advice, we corrected this format in the manuscript.
6) Lines 48-54: If authors use the word "Firstly" they should continue in the next sentence with the word "Secondly", in order to make a clear meaning to the reader.
Author’s response: Thanks for your recommendation, we made the appropriate changes to the manuscript.
7) Lines 79-83: «Secondly, they serve …. within ecosystems [15]». The sentence is quite vague. Please rewrite it in a more understandable way.
Author’s response: Thanks for your comment, we made the appropriate changes to the sentence:
“Secondly, these elements have a higher affinity to accumulate in living organisms in the geochemical landscapes of the Lower Dniester Valley than their water migration ability.”
8) Line 191: Authors should be a little more careful when interpreting the results of the table. In Table 1 (line 182) it is mentioned that the soil type Vorony-Calcic Chernozems has the lowest content of exchangeable Cations Ca2++Mg2+ [18.2 mg (eq) - 100 g-1] and not the soil type Luvy-Calcic Chernozems mentioned in the manuscript.
Author’s response: We are sorry for our incorrect writing and made a correction of the sentence.
9) Authors should be more precise when referring to figures in the manuscript. Line 219 refers to Figure 3 (a) which is not in the manuscript, but Figure 2 is. It should be replaced.
Author’s response: We are sorry for our technical mistake; we made the appropriate change to the manuscript.
10) Line 326: The word "coach" should be replaced with the word "couch".
Author’s response: We apologize for our technical mistake and corrected the word in the manuscript.
11) Figure 5, line 328: In this figure, the letters a, b and c should be entered for the statistically significant or not differences, as indicated in the tables in the manuscript.
Author’s response: Thanks for your advice, we made the appropriate changes to the figure 5.
12) Lines 400-403: The units of measurement mg kg-1 are missing the «soil» definition. It should be replaced by «mg kg-1 soil».
Author’s response: Thanks for your recommendation, we made the related correction in the manuscript.
We sincerely thank you again for your corrections and recommendations that greatly helped us to improve the manuscript.
With best regards,
Sheshnitsan Sergey
Corresponding author
Author Response File: Author Response.pdf
Round 3
Reviewer 5 Report
Comments and Suggestions for Authorssatisfied with revision
Author Response
Dear Reviewer,
Thank you very much for appreciating the work we put into revising the manuscript entitled “Selenium and Heavy Metals in Soil–Plant System in a Hydro-geochemical Province with High Selenium Content in Groundwater: A Case Study of the Lower Dniester Valley” (Manuscript ID: soilsystems-2714602).
Best regards,
Corresponding author,
Sergey Sheshnitsan
Reviewer 6 Report
Comments and Suggestions for AuthorsThe manuscript entitled "Selenium and Heavy Metals in Soil-Plant System in a Hydrogeochemical Province with High Selenium Content in Groundwater: a Case Study of the Lower Dniester Valley" has been significantly improved from the previous revision. The authors have taken into account the comments of the reviewers.
A final comment:
Τhe words "selenium" and "heavy metals" should be removed from the keywords, as they are already in the title of the manuscript.
Author Response
Dear Reviewer,
Thank you very much for appreciating the work we put into revising the manuscript entitled “Selenium and Heavy Metals in Soil–Plant System in a Hydro-geochemical Province with High Selenium Content in Groundwater: A Case Study of the Lower Dniester Valley” (Manuscript ID: soilsystems-2714602).
Following your final comment, we have made corrections to the keywords. They are now as follows:
"Keywords: bioaccumulation; soil properties; mobility; pollution; Fluvisols."
Best regards,
Corresponding author,
Sergey Sheshnitsan
Author Response File: Author Response.pdf
