The Impact of Exogenous Organic Matter on the Properties of Humus Compounds of Soils Developing on a Reclaimed Fly Ash Landfill

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Dear authors of the manuscript "Impact of exogenous organic matter on the properties of humus compounds of soils developing on a reclaimed fly ash landfill" Grażyna Żukowska, Magdalena Myszura-Dymek, Zofia Durczyńska!

With great interest i've got acquainted with the manuscript presented. It is aimed at "the evaluation of the effect of exogenous organic matter on the content and quality of organic matter in soils developing on a reclaimed fly ash landfill site" by the explanation of authors. The presented piece glaringly shows the duration of restoration processes can be extended for decades, whereas the injure to ecosystem can be a deal of several days.

The problem of soil remediation at the dumps of fly ash and other adverse industrial mining resultd is extremely relevant and requires the carefull attention of scientists, because only a scientific approach allows to create the optimal regime of territories restoration for the subsequent use in the status of ecological well-being.

The authors use many ratios and have conducted extensive research to obtain broad arrays on soil samples data. Unfortunately, relatively small number of illustrations reporting all the information received does not allow to perceive the entire volume of data accumulated and analyzed by the authors.
Also, in the Materials and methods section, the duration of restoration process (took 15 years to recreate fertile soil layer) extremely stingily mentioned. This section should be expanded with at least a schematic description of the various options for additional treatments (RV_1 (direct introduction of plants) + RV_2 (humus of the surface) + RV_3 (sewage sludge)), which were carried out during the specified 15 years. There are no time intervals for treatments and the quantities/rates of application are not indicated. There is no data on the form in which additional substances were introduced to induce the humus layer reconstruction. There is also quite a scarce information on the soil samples obtained.

The composition of plant species present at the landfill can play an important role in carbon assimilation. There is no mention of types of growing plants and the species composition in the manuscript. There is also information about how afforestation of the studied areas was carried out - were arboreal plants self-seeded or planted as seedlings.
Throughout the presentation of the data obtained, there are no indications of threshold parameters values corresponding to different soil formation regimes, the state of the soil ecosystem and/or the existing trends in the development/degradation of humus cover. The conclusion that the CPI indicates the beginning of the soil formation process (line 396) is not confirmed by any given threshold/initial values, which should be exceeded or, conversely, reduced. Moreover, the authors themselves pay attention to the fact that
"In reclaimed soils, the conditions of the soil environment are different from those in natural soils; therefore, the transformation of humus compounds may take place in a different way, and the resulting humus compounds may have a different quality." (lines 253-255).

In Figure 5 (line 373) and in the description to it, the text does not explain the choice of the 2:1 ratio for the materiality of the factors.

Unfortunately, some conclusions based on the study are trivial and loosely stated: the obvious conclusion that the characteristics used in the work are an indication of a different state and changes occurring in the soil could have been made without conducting research (line 406): "Quality indicators of organic matter may be a useful parameter for determining the differentiation of reclaimed soils.".

Further comments mainly concern the detected technical issues.
The captions are inaccurate and sometimes duplicate the contents, for example, see the caption to Figure 1 (line 212). The figures captions explained in the captions duplicate the main material of the work and contain inaccuracies (non-labile through a dash, line 273).
All figures are given within the frames, some scales on the graphs are redundant - in Figure 3 (lines 314-315) there is no data between the marks "120" and "140" for example.
In Table 1, the right column for all rows is the same (line 101) - it is unclear why this data should be included in the table.
Abbreviations are used in Table 2, some of which are re-deciphered excessively in the explanation.
Could "Explanations" after the tables better be changed into "notes"?
Line 155 contains "3. Results i discussion" which is not clear enough to understand, so are lines 352 and 353 also.
The "ubstrate" in line 229 and "carbo" in line 386 are weird.

The overall recomendation is to make a major review to the piece clarifying all the found weeknesses.

Author Response

Dear Reviewer,

We would like to thank the Reviewer for your time and constructive, inspiring comments and remarks, which were valuable and very helpful for revising and improving our paper, as well as the important guides significance to this research. We studied comments carefully and made correction which I hope meet with approval. The main corrections in the paper and the responds to the Reviewer’s comments are listed below.

Comments and Suggestions

1. The authors use many ratios and have conducted extensive research to obtain broad arrays on soil samples data. Unfortunately, relatively small number of illustrations reporting all the information received does not allow to perceive the entire volume of data accumulated and analyzed by the authors.

 

Response: The research results were presented in the form of tables (in the text and in the supplementary material) and figures. The small number of figures presenting the research results results from the fact that we did not want to duplicate the content in the figures included in the tables.

 

2. Also, in the Materials and methods section, the duration of restoration process (took 15 years to recreate fertile soil layer) extremely stingily mentioned. This section should be expanded with at least a schematic description of the various options for additional treatments (RV_1 (direct introduction of plants) + RV_2 (humus of the surface) + RV_3 (sewage sludge)), which were carried out during the specified 15 years. There are no time intervals for treatments and the quantities/rates of application are not indicated. There is no data on the form in which additional substances were introduced to induce the humus layer reconstruction. There is also quite a scarce information on the soil samples obtained.

 

Response: As for the material and methods sections, this chapter has been completely revised, expanded and supplemented with missing information.

3. The composition of plant species present at the landfill can play an important role in carbon assimilation. There is no mention of types of growing plants and the species composition in the manuscript. There is also information about how afforestation of the studied areas was carried out - were arboreal plants self-seeded or planted as seedlings.

Response: The information has been supplemented in the Material and Methods section.

4. Throughout the presentation of the data obtained, there are no indications of threshold parameters values corresponding to different soil formation regimes, the state of the soil ecosystem and/or the existing trends in the development/degradation of humus cover. The conclusion that the CPI indicates the beginning of the soil formation process (line 396) is not confirmed by any given threshold/initial values, which should be exceeded or, conversely, reduced. Moreover, the authors themselves pay attention to the fact that "In reclaimed soils, the conditions of the soil environment are different from those in natural soils; therefore, the transformation of humus compounds may take place in a different way, and the resulting humus compounds may have a different quality." (lines 253-255).

Response: The conclusion regarding CPI was made more precise in the text of the paper and it was explained that a CMI value above 100 indicates the initiation of the soil-forming process.

5. In Figure 5 (line 373) and in the description to it, the text does not explain the choice of the 2:1 ratio for the materiality of the factors.

Response: We have supplemented the text with the following information:

In the conducted principal component analysis (PCA), factor 1 explains the significant majority of the total variability of the studied parameters (77.46%), which indicates its dominant influence on the analyzed soil properties. Such a high share of the first factor suggests that it is the main carrier of information about the variability of soil properties, and therefore considering it more important in relation to factor 2 is justified. In turn, factor 2, explaining 22.54% of the variability, is also valuable, but its influence on the variability of properties is clearly smaller, therefore it was assumed that its significance in the analysis is smaller in relation to factor 1.

6. Unfortunately, some conclusions based on the study are trivial and loosely stated: the obvious conclusion that the characteristics used in the work are an indication of a different state and changes occurring in the soil could have been made without conducting research (line 406): "Quality indicators of organic matter may be a useful parameter for determining the differentiation of reclaimed soils.".

Response: The conclusions have been corrected

7. The captions are inaccurate and sometimes duplicate the contents, for example, see the caption to Figure 1 (line 212). The figures captions explained in the captions duplicate the main material of the work and contain inaccuracies (non-labile through a dash, line 273).

Response: Corrections have been made

8. All figures are given within the frames, some scales on the graphs are redundant - in Figure 3 (lines 314-315) there is no data between the marks "120" and "140" for example.

Response: Corrections have been made

9. In Table 1, the right column for all rows is the same (line 101) - it is unclear why this data should be included in the table.

Response: The table has been replaced by a detailed description of the experimental design in the Material and Methods section.

10. Abbreviations are used in Table 2, some of which are re-deciphered excessively in the explanation.

Response: Corrections have been made

11. Could "Explanations" after the tables better be changed into "notes"?

Response: „Explanations” replaced by the word „notes”

12. Line 155 contains "3. Results i discussion" which is not clear enough to understand, so are lines 352 and 353 also.

Response: Corrections have been made

13. The "ubstrate" in line 229 and "carbo" in line 386 are weird.Response: Sewage sludge was used only once.

Response: Corrections have been made

I hope that the Editor and the Reviewer will find our revised manuscript acceptable for publication in Sustainability.

Thank you very much for managing our manuscript.

  

Sincerely Yours,

Magdalena Myszura-Dymek

with co-authors

 

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

Review Comments:

The study is very useful for land reclamation of fly ash waste. However, it was very difficult to quantify the impact of the reclamation methods used without clear description of the materials used in the reclamation processes (i.e., proper quantification of the basic physical and chemical properties) and to support the study conclusion on Line 380 “The increase in TOC content and carbon stocks was significantly dependent on the amount of EOM introduced.”

Therefore, I am recommending minor revision.

Specific comments are given below:

Line 60: should read “Exogenous Organic Matter (EOM)” introduced…..

Line 89; section 2.2: A figure showing the layering of the materials (part of the fly ash waste, topsoil layer, and the sludge layer) and the sampling points is required.

Line 101: Three figures describing the experimental schemes (RV_1, RV_2, and RV_3) and the sampling points are required. Also, detailed description of the reclamation processes as well as the physico-chemical characterization of the added reclaimed materials must be given.

Line 155: Should read Results and Discussion

Lines 156-179 have no relevance and must be deleted.

Comments on the Quality of English Language

The English needs improvements. 

Author Response

Dear Reviewer,

We would like to thank the Reviewer for your time and constructive, inspiring comments and remarks, which were valuable and very helpful for revising and improving our paper, as well as the important guides significance to this research. We studied comments carefully and made correction which I hope meet with approval. As suggested, we have made English language corrections using MDPI service. The main corrections in the paper and the responds to the Reviewer’s comments are listed below.

Comments and Suggestions

1. Line 60: should read “Exogenous Organic Matter (EOM)” introduced…..

 

Response: Corrections have been made

2. Line 89; section 2.2: A figure showing the layering of the materials (part of the fly ash waste, topsoil layer, and the sludge layer) and the sampling points is required.

Response: The figure has been added

3. Line 101: Three figures describing the experimental schemes (RV_1, RV_2, and RV_3) and the sampling points are required. Also, detailed description of the reclamation processes as well as the physico-chemical characterization of the added reclaimed materials must be given.

 

Response: Figures have been added. Other information has been supplemented in the Material and Methods section.

 

4. Line 155: Should read Results and Discussion

Response: The chapter title has been corrected

5. Lines 156-179 have no relevance and must be deleted.

Response: Thank you for your attention, part of the text has been removed, and the introductory literature information for the discussion and results has been retained.

I hope that the Editor and the Reviewer will find our revised manuscript acceptable for publication in Sustainability.

Thank you very much for managing our manuscript.

  

Sincerely Yours,

Magdalena Myszura-Dymek

with co-authors

 

 

Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

Title and text:
The term 'exogenous organic matter' is difficult for me as a reader. I rather would
expect 'amendment of organic matter'.

The abstract takes the reader by surprise. It is not clearly stated
- what are we doing
- why are we doing it
- what did we find.

Introduction
I wonder whether the first sentence is correct. A ref is needed. Moreover, is this a
statement for the globe, for Europe, a country??

Apart from the numerous questions it is difficult to assess the niche of information
of the presented text. It is not clear which case the authors want to make.

Table 1. Experiment Scheme: it is difficult to understand the table as a stand-alone.
this applies for all tables.

l. 122: it is not clear what an undisturbed area could be, how strong the data
support for the respective sample of undisturbed area is.

The Carbon Management Index is unclear.

The authors may want to change the language. e.g. 'Results i discussion': what is
'i'?

pls separate Results and Discussion in different sections.

Author Response

Dear Reviewer,

We would like to thank the Reviewer for your time and constructive, inspiring comments and remarks, which were valuable and very helpful for revising and improving our paper, as well as the important guides significance to this research. We studied comments carefully and made correction which I hope meet with approval. The main corrections in the paper and the responds to the Reviewer’s comments are listed below.

Comments and Suggestions

1. The term 'exogenous organic matter' is difficult for me as a reader. I rather would expect 'amendment of organic matter'.

Response: Thank you for this suggestion. We want to stay with the term 'Exogenous Organic Matter' (EOM) because it is commonly used in the literature on the subject. Here are some examples of the use of the term 'exogenous organic matter':

Lashermes, Gwenaëlle, et al. "Typology of exogenous organic matters based on chemical and biochemical composition to predict potential nitrogen mineralization." Bioresource Technology 101.1 (2010): 157-164.

Bruni, Elisa, et al. "Defining quantitative targets for topsoil organic carbon stock increase in European croplands: Case studies with exogenous organic matter inputs." Frontiers in Environmental Science 10 (2022): 824724.

Usowicz, Bogusław, and Jerzy Lipiec. "The effect of exogenous organic matter on the thermal properties of tilled soils in Poland and the Czech Republic." Journal of Soils and Sediments 20 (2020): 365-379.

Siebielec, Sylwia, et al. "Microbial Community Response to Various Types of Exogenous Organic Matter Applied to Soil." International Journal of Molecular Sciences 24.19 (2023): 14559.

2. The abstract takes the reader by surprise. It is not clearly stated

- what are we doing

- why are we doing it

- what did we find.

Response: The abstract has been edited and supplemented with missing information.

3. Introduction. I wonder whether the first sentence is correct. A ref is needed. Moreover, is this a statement for the globe, for Europe, a country??

Response: We agree with the comment that the first sentence is not worded correctly and has been deleted.

4. Apart from the numerous questions it is difficult to assess the niche of information of the presented text. It is not clear which case the authors want to make.

Response: The introduction chapter includes additional information on what information niche we are assessing and why.

5. Table 1. Experiment Scheme: it is difficult to understand the table as a stand-alone. this applies for all tables.

Response: Table 1 has been replaced with a detailed description containing the characteristics of the conducted reclamation procedures. The remaining tables present the results of the research, which have been divided into thematic sections. Some of the tables have been placed in the supplementary materials.

6. l. 122: it is not clear what an undisturbed area could be, how strong the data support for the respective sample of undisturbed area is.

Response: The explanation is given in the Material and Methods section.

7. The Carbon Management Index is unclear.

Response: As reported in the Manuscript, the Carbon Management Index (CMI) was developed by Blair et al. [48] and is widely used in the literature. The mathematical equations used to calculate the CMI are given and explained in the Material and Methods section. As reported by Blair et al. [48], the CMI value itself is not important, but the difference may indicate the impact of different land uses on the system. There is no clear standard for the CMI because it is based on the local land use in a given area. However, Blair [48] reported that higher CMI values ​​indicate carbon recovery, while lower CMI values ​​indicate that soil C is degraded. We have added additional description to the methodology and the results and discussion section.

8. The authors may want to change the language. e.g. 'Results i discussion': what is 'i'?

Response: Corrections have been made

9. pls separate Results and Discussion in different sections.

Response: Thank you for your suggestion. During the preparation of this manuscript, we have reviewed the guidelines for authors, and these guidelines allow for combining the chapters of research results and discussion. Therefore, when developing the concept of the manuscript, we decided that the research results will be discussed and simultaneously discussed with other scientific reports on similar topics in a common chapter ‘research results and discussion’.

I hope that the Editor and the Reviewer will find our revised manuscript acceptable for publication in Sustainability.

Thank you very much for managing our manuscript.

  

Sincerely Yours,

Magdalena Myszura-Dymek

with co-authors

 

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Dear authors of the manuscript "Impact of exogenous organic matter on the properties of humus compounds of soils developing on a reclaimed fly ash landfill" Grażyna Żukowska, Magdalena Myszura-Dymek, Zofia Durczyńska!


With great interest i've got again acquainted with new version of the manuscript presented. The second version is much wider then the first one. More information become clearer, the presented study gained significance with the changes made.
New data added to the manuscript also requires refinement. Table 1 (line 105) comprises actually two table - one with macro- and mezo- elements contents and the other with physical properties of the matter. Figure 1 (line 110) should be comprehensively described in text and new caption should be provided, as in current state it is unclear why different colors are used (in part b especially). Is it sampling technique that causes depths of layers to be 0-15 and 15-40 cm? Or it is dictated by content analysis? Satellite image of the experimental area looks all over afforested (beyond the marked rectangle experimental site too). Was the site chosen 15 years ago, or the area was picked out directly before sampling?
CMI in figure 5 (line 371-373) painterly shows that only one (from variety of two) measure/treatment resulted in soil-formation process on the 15-years horizon. Very doubtly this effect can be the base to recommend this single method for vast use. Some phrases have to be made  more accurately formulated (see for example lines 6 and 7, 32, 132).

These remarks are only reflecting a point of view. Authors have made great effort to improve their manuscript and have succeeded in some points.

Author Response

Dear Reviewer,

We would like to thank the Reviewer once again for his time and constructive, inspiring comments and remarks, which were valuable and very helpful in revising and improving our article, and also for appreciating our previous corrections. We have carefully studied the comments and made a correction that we hope will be approved. The main corrections in the article and the responses to the Reviewer's comments are listed below.

Comments and Suggestions

1. Table 1 (line 105) comprises actually two table - one with macro- and mezo- elements contents and the other with physical properties of the matter.

Response: Thank you for your comment. Table 1 has now been divided into 2 tables: 1. Chemical composition of fly ash deposited in a reclaimed landfill, 2. Basic physical and physicochemical properties of fly ash deposited in a reclaimed landfill.

2. Figure 1 (line 110) should be comprehensively described in text and new caption should be provided, as in current state it is unclear why different colors are used (in part b especially).

Response: Thank you for your comment. The caption of Figure 1 has been corrected to: Vertical cross-section of Technosol at the fly ash landfill: 1a) assessed reclamation variants - before the introduction of plants, 1b) 15-year Technosol development on assessed fly ash landfill rec-lamation variants, including sampling depth.

Referring to the different colors of the Technosol vertical cross-sections in Figure 1b, the initial formation of soil horizons was observed after the excavations were made. Hence, the observed horizons are marked in different colors (Fig. 1b). This is described in the text in lines 172-174.

3. Is it sampling technique that causes depths of layers to be 0-15 and 15-40 cm? Or it is dictated by content analysis?

Response: Thank you for your comment. The explanation in the text is in the lines 174-177.

4. Satellite image of the experimental area looks all over afforested (beyond the marked rectangle experimental site too). Was the site chosen 15 years ago, or the area was picked out directly before sampling?

Response: Thank you for your comment. The location and satellite image were selected immediately before soil sampling. In the years when the experiment was established we had no possibility to obtain a satellite image.

5. CMI in figure 5 (line 371-373) painterly shows that only one (from variety of two) measure/treatment resulted in soil-formation process on the 15-years horizon. Very doubtly this effect can be the base to recommend this single method for vast use.

Response: Thank you for your comment. We have corrected this statement in the abstract and conclusions.

6. Some phrases have to be made more accurately formulated (see for example lines 6 and 7, 32, 132).

Response: Thank you for your comment. We have improved the suggested fragments in lines 6-7, currently lines 6-9: „Fly ash does not contain organic matter necessary to initiate soil-forming processes and proper development of plant cover. Therefore, in the recultivation of fly ash landfills, an integrated approach is required, including the introduction of exogenous organic matter into the top layer of ash”,

Lines 32, currently lines 34-37: „Coal is mined in 12 EU countries [1], including Poland [2]. In Poland, coal-fired pow-er plants provide over 80% of energy [3]. They also produce products of coal combustion that can be both a resource and a disposal problem. Of the combustion by-products, over 75% are fly ash [2]”,

Lines 132, currently lines 137-140: „Various sources of exogenous organic matter (EOM), respectively, humus soil and municipal sewage sludge, were used for the reclamation of the fly ash landfill in variants RV_2 and RV_3. The types of EMO used in reclamation and their properties are presented in Table 3”.

 

 

I hope that the Editor and the Reviewer will find our revised manuscript acceptable for publication in Sustainability.

Thank you very much for managing our manuscript.

  

Sincerely Yours,

Magdalena Myszura-Dymek

with co-authors

 

Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

I acknowledge that the authors have dealt with reviewer suggestions in a constructive way.

Author Response

Dear Reviewer,

We would like to thank the Reviewer once again for his time and constructive, inspiring comments and remarks, which were valuable and very helpful in revising and improving our article, and also for appreciating our corrections.

I hope that the Editor and the Reviewer will find our revised manuscript acceptable for publication in Sustainability.

Thank you very much for managing our manuscript.

  

Sincerely Yours,

Magdalena Myszura-Dymek

with co-authors

 

Author Response File: Author Response.docx

Round 3

Reviewer 1 Report

Comments and Suggestions for Authors

Dear authors of the manuscript "Impact of exogenous organic matter on the properties of humus compounds of soils developing on a reclaimed fly ash landfill" Grażyna Żukowska, Magdalena Myszura-Dymek, Zofia Durczyńska!

With great interest i've read  the new version of the manuscript. The third version is a bit better then the previous, but have little flaws (as EOM have turned to EMO in line 32, etc.). Information become more accurate, the presented study gained significance.

Author Response

Dear Reviewer,

We would like to thank the Reviewer once again for his time and all valuable comments, which were very helpful in revising and improving our article, and also for appreciating our previous corrections. We have made every effort, both before and now, to thoroughly improve our manuscript.

We have carefully studied the comments and made a correction, which we hope will be approved. The main corrections in the article and the responses to the Reviewer's comments are listed below. In the text, the corrections are marked in green.

 

Comments and Suggestions

1. The third version is a bit better then the previous, but have little flaws (as EOM have turned to EMO in line 32, etc.)

Response: Thank you for your comment. The abbreviation EMO has been corrected to EOM throughout the article. This is highlighted in green. It is our oversight.

I hope that the Editor and the Reviewer will find our revised manuscript acceptable for publication in Sustainability.

Thank you very much for managing our manuscript.

  

Sincerely Yours,

Magdalena Myszura-Dymek

with co-authors

 

Author Response File: Author Response.pdf