Uptake Prediction of Eight Potentially Toxic Elements by Pistia stratiotes L. Grown in the Al-Sero Drain (South Nile Delta, Egypt): A Biomonitoring Approach
, Mohammed A. Dakhil 3, Loutfy M. Hassan 3, Shaimaa G. Salama 4 and Tarek M. Galal 3,5Round 1
Reviewer 1 Report
the term heavy metal is now deprecated, and the preferred term is potentially toxic element (PTE)
the abstract is only very barely informative: what are the 8 PTEs investigated? what was measured? great improvement is necessary
l. 42 unchanged?
the aims are quite badly stated: they should expressed in the form of testable hypotheses
on what basis were the three sites selected?
may tap water have caused the uptake of some element?
I am a bit puzzled by the level of replication: quadrats for each site were pooled, so replication was site x time: correct?
t test to compare what? root vs shoot data? or monthly data? this is important, since in the latter a paired comparison with correction for multiple testing is necessary – additionally, were the data normally distributed?
what is the source of equation (3)?
I cannot understand what is the meaning of a relationship of water vs root/water
conclusions are far too long and do not offer any real new insight: what can be concluded from this study? that Pistia can be used for water quality monitoring, this is quite old stuff; that a straight relationship has been established for the study sites? this is reasonable, but without knowing water pH what can be concluded from plants alone? I see a relatively wide pH range (7-8.9), but it is well known that many elements are mostly available at lower pH values of ca. 5.5
the English is formally correct, but there are many terms which are not part of the current scientific writing, please revise
Author Response
24 April 2021
Dr. Ludmiła Polechońska and Dr. Małgorzata Dambiec
The Guest Editors
Sustainability,
Dear Dr. Ludmiła Polechońska and Dr. Małgorzata Dambiec,
Please find attached the revised manuscript titled ‘Uptake prediction of eight potentially toxic elements by Pistia stratiotes L. grown in Al-Sero Drain (South Nile Delta, Egypt): a biomonitoring approach’; sustainability-1179515, authored by Ebrahem M. Eid, Mohammed A. Dakhil, Loutfy M. Hassan, Shaimaa G. Salama, and Tarek M. Galal.
On behalf of my co-authors, I thank you very much for giving us the opportunity to revise our manuscript. We appreciate the positive and constructive comments and suggestions provided by the reviewers on our manuscript. We have carefully studied the reviewers’ comments and have made revisions that are highlighted in yellow in the revised version of the manuscript. We have tried our best to revise our manuscript according to the reviewers’ comments. Please find attached the revised version of our manuscript, which we would like to submit for your kind consideration. Once again, we would like to express our great appreciation to you and the reviewers for the comments on our manuscript.
Please find below our detailed responses to each of the points raised.
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Response: Thanks so much Sir for your time and for your constructive comments and suggestions. We have tried our best to revise our manuscript according to your’ comments.
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The term heavy metal is now deprecated, and the preferred term is potentially toxic element (PTE)
Response: Potentially toxic element (PTE) was used instead of the term heavy metal.
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the abstract is only very barely informative: what are the 8 PTEs investigated? what was measured? great improvement is necessary
Response: The following information was added to the abstract:
This study considered the absorption of eight PTEs (Cd, Co, Cu, Fe, Mn, Ni, Pb, and Zn), and the evaluated P. stratioteswere located in three sampling locations along the Al-Sero Drain, with sampling conducted in both monospecific and homogenous P. stratiotes. Samples of both types of P. stratiotes and water were collected on a monthly basis between May 2013 and April 2014 at each location, utilising three randomly chosen 0.5 × 0.5 m quadrats.
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- 42 unchanged?
Response: “are persistent in the environment” was used instead of unchanged.
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the aims are quite badly stated: they should expressed in the form of testable hypotheses
on what basis were the three sites selected?
Response: The aims were rewritten as: Although P. stratiotes has been the subject of considerable recent phytoremediation research [28,30-37], there is a dearth of published prediction models for PTE uptake within the shoot and root systems of P. stratiotes growing in natural environments. Mathematical models describing PTE uptake by P. stratiotes grown on paper mill effluent in a lab scale phytoremediation experiment were developed by Kumar et al. [10]; however, these models cannot be used to predict PTE uptake in conditions other than those used in the experiment. Thus, the aim of the current research was to design a de novo regression model to predict PTE concentration within P. stratiotesshoot and root systems in a natural habitat (the Al-Sero Drain), considering water characteristics such as the PTE concentration and pH. Another goal was to discover how capable P. stratiotes could be as a biomonitor of eight PTE concentrations in the Al-Sero Drain, a site considered typical of the South Nile Delta drainage channels. Our hypothesis was that the PTE accumulation capabilities of P. stratiotes and its potential to serve as a biomonitor for PTE contamination could differ among populations grown under natural conditions, and those grown under experimental conditions. This work will additionally be of value for the future utilisation of this form of vegetation in Egyptian phytoremediation research.
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may tap water have caused the uptake of some element?
Response: The PTEs potentially adsorbed to tissue surface were eliminated as described in Lines 129-132 by washing with deionized water through a sieve. The washing with deionized water is used in almost all studies carried out in plants in order to eliminate metals deposited in the external surface by contamination that could be adsorbed but have not been absorbed yet. Then, in this study only those PTEs that have been absorbed and are inside the plant have been determined. In any case, your comment noted us that we did not explain this properly and then, the sentence has been modified as “The samples were divided into shoot and root systems and washed with tap water, and then cleaned with deionized water over a 4 mm mesh sieve to eliminate PTEs adsorbed on the tissue surface, and to minimize material loss. In this way, only PTEs absorbed by the plant were determined, and then the bioaccumulation was assessed”.
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I am a bit puzzled by the level of replication: quadrats for each site were pooled, so replication was site x time: correct?
Response: The following details were added: One composite sample from each quadrat from each P. stratiotes shoot and root systems at each of the three sampling sites per month was then utilised to assay cadmium (Cd), cobalt (Co), copper (Cu), iron (Fe), manganese (Mn), nickel (Ni), lead (Pb), and zinc (Zn) levels. In total, 108 plant samples per each P. stratiotes shoot and root system (3 quadrats × 3 sampling locations × 12 sampling times (months)) were used to determine the uptake of the eight PTEs.
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t test to compare what? root vs shoot data? or monthly data? this is important, since in the latter a paired comparison with correction for multiple testing is necessary – additionally, were the data normally distributed?
Response: Student’s t-tests were used to analyse any variations in the PTE data between the shoot and root samples.
Prior to conducting a one-way analysis of variance (ANOVA-1), the BCF and TF data were evaluated by using the Shapiro-Wilk W and Levene tests for the presence of a normal distribution and variance homogeneity. The data were then transformed into logs if necessary.
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what is the source of equation (3)?
Response: The source was given: 10. Kumar, V.; Singh, J.; Kumar, P. Heavy metal uptake by water lettuce (Pistia stratiotes L.) from paper mill effluent (PME): Experimental and prediction modelling studies. Environ. Sci. Pollut. Res.2019, 26, 14400-14413.
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I cannot understand what is the meaning of a relationship of water vs root/water
Response: We investigate the correlation between the PTE levels in the water and the BCF of the PTEs in the P. stratiotesroot system which was measured using non-linear regression. In the present study, an exponential drop in BCF values for all the PTEs with rising water concentrations of these elements.
Similar finding was noted by Eid et al. [55] for E. crassipes grown in irrigation canals in the North Nile Delta in Egypt.
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conclusions are far too long and do not offer any real new insight: what can be concluded from this study? that Pistia can be used for water quality monitoring, this is quite old stuff; that a straight relationship has been established for the study sites? this is reasonable, but without knowing water pH what can be concluded from plants alone? I see a relatively wide pH range (7-8.9), but it is well known that many elements are mostly available at lower pH values of ca. 5.5
Response: Thanks Sir for this comment. The conclusions were rewritten to offer real new insight. Please see Page 13 Lines 449-470.
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the English is formally correct, but there are many terms which are not part of the current scientific writing, please revise
Response: To meet the standards of the journal, an English Language Editing Service provided by MDPI English Editing Services (Project no. english-29242) was used. Please see the attached certificate of language editing.
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I hope the explanation given above adequately addresses all the reviewers’ comments. I would appreciate if the revised version of our manuscript would be considered for publication in a special issue of Sustainability on ‘Aquatic Plants as Bioindicators of Trace Metal Pollution’
Yours
Ebrahem M. Eid
[Kafrelsheikh University]
[Botany Department, Faculty of Science, Kafrelsheikh University, Kafr El-Sheikh 33516, Egypt]
[Phone number: 002010 22648840]
[Email address: [email protected]]
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The manuscript entitled: "Uptake prediction of eight heavy metals by Pistia stratiotes L. grown in Al-Sero Drain (South Nile Delta, Egypt): a biomonitoring approach" is to describe the results in evaluation of accumulation of HMs in the Pistia stratiotes L. and water collected from Al-Sero Drain (South Nile Delta, Egypt). This is done by collecting samples from 3 research sites. The study was well organized and described. An interesting element of the manuscript is the regression model. The obtained results can be useful for the people in these particular areas and applied in biomonitoring. However, there are some weaknesses in the manuscript:
- The samples were collected between May 2013 and April 2014. Were there any differences in the content of heavy metals depending on the sampling date? Have any statistical analyses been carried out for this factor? This information should be included in the manuscript, because it may be relevant for the proposed regression model.
- The description of the number of samples taken of plants (biomass) is not sufficient. What specific amount of biomass was collected from the research sites each time?
- Figure 1 - the locations of the three sampling sites are unreadable.
- The conducted research showed a different tendency for the accumulation of Fe and Cu in the roots. The mechanism was explained in the discussion. However, there is no information about similar trends in previous studies.
- There is no discussion of the obtained results for the content of heavy metals in Pistia stratiotes L. This would allow readers to assess the possibility of applying the regression model in other conditions.
- A weakness of the manuscript is the validation of the regression model. From a methodological point of view, it is carried out correctly. However, the data used for validation raise some doubts. The research was carried out in 2013 and 2014. It was therefore possible to take samples in subsequent years to verify the model for other heavy metal concentrations. The presented model is good, but only for these specific conditions.
Author Response
24 April 2021
Dr. Ludmiła Polechońska and Dr. Małgorzata Dambiec
The Guest Editors
Sustainability,
Dear Dr. Ludmiła Polechońska and Dr. Małgorzata Dambiec,
Please find attached the revised manuscript titled ‘Uptake prediction of eight potentially toxic elements by Pistia stratiotes L. grown in Al-Sero Drain (South Nile Delta, Egypt): a biomonitoring approach’; sustainability-1179515, authored by Ebrahem M. Eid, Mohammed A. Dakhil, Loutfy M. Hassan, Shaimaa G. Salama and Tarek M. Galal.
On behalf of my co-authors, I thank you very much for giving us the opportunity to revise our manuscript. We appreciate the positive and constructive comments and suggestions provided by the reviewers on our manuscript. We have carefully studied the reviewers’ comments and have made revisions that are highlighted in yellow in the revised version of the manuscript. We have tried our best to revise our manuscript according to the reviewers’ comments. Please find attached the revised version of our manuscript, which we would like to submit for your kind consideration. Once again, we would like to express our great appreciation to you and the reviewers for the comments on our manuscript.
Please find below our detailed responses to each of the points raised.
---------------------------------------------------------------------------------------------------------------------
The manuscript entitled: "Uptake prediction of eight heavy metals by Pistia stratiotes L. grown in Al-Sero Drain (South Nile Delta, Egypt): a biomonitoring approach" is to describe the results in evaluation of accumulation of HMs in the Pistia stratiotes L. and water collected from Al-Sero Drain (South Nile Delta, Egypt). This is done by collecting samples from 3 research sites. The study was well organized and described. An interesting element of the manuscript is the regression model. The obtained results can be useful for the people in these particular areas and applied in biomonitoring. However, there are some weaknesses in the manuscript:
- The samples were collected between May 2013 and April 2014. Were there any differences in the content of heavy metals depending on the sampling date? Have any statistical analyses been carried out for this factor? This information should be included in the manuscript, because it may be relevant for the proposed regression model.
Response: Thanks so much Sir for your time and for your constructive comments and suggestions. The following information was added to the text: Although the water PTE concentrations have not varied significantly in recent years [41], throughout this study, monthly samples were taken over a period of twelve months (May 2013–April 2014), which should have captured the variations in concentration in different months.
- Dakhil, M.; Galal, T.; Hassan, L. Population Dynamics and Nutrient Cycling of Pistia stratiotes L. LAP LAMBERT Academic Publishing: Saarbrücken, Germany, 2016.
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- The description of the number of samples taken of plants (biomass) is not sufficient. What specific amount of biomass was collected from the research sites each time?
Response: The following information was added: The total biomass ranged between 29.9 g DM/m2 in May and 341.6 g DM/m2 in August. Detailed data on the biomass were presented in our previous paper [40].
- Galal, T.M.; Dakhil, M.A.; Hassan, L.M.; Eid, E.M. Population dynamics of Pistia stratiotes L. Rend. Fis. Acc. Lincei 2019, 30, 367-378.
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- Figure 1 - the locations of the three sampling sites are unreadable.
Response: The font size was increased to be readable.
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- The conducted research showed a different tendency for the accumulation of Fe and Cu in the roots. The mechanism was explained in the discussion. However, there is no information about similar trends in previous studies.
Response: The following sentence was added: Similar findings were noted by Kumar et al. [10] for current species grown on paper mill effluent in a lab scale phytoremediation experiment, and by Eid et al. [55] for E. crassipes grown in irrigation canals in the North Nile Delta in Egypt.
- Kumar, V.; Singh, J.; Kumar, P. Heavy metal uptake by water lettuce (Pistia stratiotes L.) from paper mill effluent (PME): Experimental and prediction modelling studies. Environ. Sci. Pollut. Res. 2019, 26, 14400-14413.
- Eid, E.M.; Shaltout, K.H.; Almuqrin, A.H.; Aloraini, D.A.; Khedher, K.M.; Taher, M.A.; Alfarhan, A.H.; Picó, Y.; Barcelo, D. Uptake prediction of nine heavy metals by Eichhornia crassipes grown in irrigation canals: A biomonitoring approach. Sci. Total Environ. 2021, 782: 146887.
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- There is no discussion of the obtained results for the content of heavy metals in Pistia stratiotes L. This would allow readers to assess the possibility of applying the regression model in other conditions.
Response: The obtained results for the content of heavy metals in P. stratiotes was discussed. Please see Page 10 Line 329-335.
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- A weakness of the manuscript is the validation of the regression model. From a methodological point of view, it is carried out correctly. However, the data used for validation raise some doubts. The research was carried out in 2013 and 2014. It was therefore possible to take samples in subsequent years to verify the model for other heavy metal concentrations. The presented model is good, but only for these specific conditions.
Response: We appreciate the criticism of the reviewer about our manuscript because it has helped us very much to go through the manuscript and to try to improve these aspects. Although the water PTE concentrations have not varied significantly in recent years [41], throughout this study, monthly samples were taken over a period of twelve months (May 2013–April 2014), which should have captured the variations in concentration in different months. Therefore, no need to take samples in subsequent years to verify the model. We hope that our comments have capture the idea of the reviewer on the needs of the manuscript. Otherwise, we are open to do any further modification or to extend the discussion regarding this point.
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I hope the explanation given above adequately addresses all the reviewers’ comments. I would appreciate if the revised version of our manuscript would be considered for publication in a special issue of Sustainability on ‘Aquatic Plants as Bioindicators of Trace Metal Pollution’
Yours
Ebrahem M. Eid
[Kafrelsheikh University]
[Botany Department, Faculty of Science, Kafrelsheikh University, Kafr El-Sheikh 33516, Egypt]
[Phone number: 002010 22648840]
[Email address: [email protected]]
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
the paper has been improved according to my suggestions; however I am still unhappy with the response to one issue:
"I cannot understand what is the meaning of a relationship of water vs root/water
Response: We investigate the correlation between the PTE levels in the water and the BCF of the PTEs in the P. stratiotesroot system which was measured using non-linear regression. In the present study, an exponential drop in BCF values for all the PTEs with rising water concentrations of these elements.
Similar finding was noted by Eid et al. [55] for E. crassipes grown in irrigation canals in the North Nile Delta in Egypt."
Please explain in detail what is the ecological meaning of a (root/water)/water relationship; a self-citation is not nice in this context. A detailed explanation and critical discussion is required here
Author Response
28 April 2021
Dr. Ludmiła Polechońska and Dr. Małgorzata Dambiec
The Guest Editors
Sustainability,
Dear Dr. Ludmiła Polechońska and Dr. Małgorzata Dambiec,
Please find attached the revised manuscript titled ‘Uptake prediction of eight potentially toxic elements by Pistia stratiotes L. grown in the Al-Sero Drain (South Nile Delta, Egypt): a biomonitoring approach’; sustainability-1179515, authored by Ebrahem M. Eid, Mohammed A. Dakhil, Loutfy M. Hassan, Shaimaa G. Salama, and Tarek M. Galal.
On behalf of my co-authors, I thank you very much for giving us the opportunity to revise our manuscript. We appreciate the positive and constructive comments and suggestions provided by the reviewers on our manuscript. We have carefully studied the reviewers’ comments and have made revisions that are highlighted in yellow in the revised version of the manuscript. We have tried our best to revise our manuscript according to the reviewers’ comments. Please find attached the revised version of our manuscript, which we would like to submit for your kind consideration. Once again, we would like to express our great appreciation to you and the reviewers for the comments on our manuscript.
Please find below our detailed responses to each of the points raised.
---------------------------------------------------------------------------------------------------------------------
the paper has been improved according to my suggestions; however I am still unhappy with the response to one issue:
"I cannot understand what is the meaning of a relationship of water vs root/water
Response: We investigate the correlation between the PTE levels in the water and the BCF of the PTEs in the P. stratiotesroot system which was measured using non-linear regression. In the present study, an exponential drop in BCF values for all the PTEs with rising water concentrations of these elements.
Similar finding was noted by Eid et al. [55] for E. crassipes grown in irrigation canals in the North Nile Delta in Egypt."
Please explain in detail what is the ecological meaning of a (root/water)/water relationship; a self-citation is not nice in this context. A detailed explanation and critical discussion is required here.
Response: Thanks so much Sir for your time and for your patience. The following explanation and discussion was added to the text:
In the present study, non-linear regression was used to relate PTEs in P. stratiotes root system to the PTEs concentration in the water. The data demonstrated an exponential drop in BCF values for all the PTEs with rising water concentrations of these elements. In other word, the bioaccumulation of PTEs in root system decreased with an increase in PTEs concentration in the water. Similar finding was noted by Prasad and Maiti [72] for E. crassipes growing in ponds from mining and nonmining areas in India, and Eid et al. [55] for E. crassipes grown in irrigation canals in the North Nile Delta in Egypt. A similar inverse relationship has been recorded in other investigation in terrestrial environment by Wang et al. [73] in four common vegetables (Chinese cabbage, spinach, celery, cole) grown on PTE-contaminated soils under the field conditions in China. A potential mechanism to explain this is that the plants have a crucial ability to self-regulate PTE uptake into their root systems [74,75]. Additionally, the macrophytes tend to thrive less well in polluted water. This is particularly the case where the water is heavily contaminated; plants undergo blasting and may fail to survive, owing to the poisonous consequences of the water toxins [72]. In this situation, the poor quality of the habitat ameliorates the ability of the macrophytes to absorb PTEs, and so the concentration of these PTEs within the root system is diminished [73]. The results therefore point to the fact that the concentration of the PTE are important for the availability of PTEs in water.
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I hope the explanation given above adequately addresses all the reviewer’ comments. I would appreciate if the revised version of our manuscript would be considered for publication in a special issue of Sustainability on ‘Aquatic Plants as Bioindicators of Trace Metal Pollution’
Yours
Ebrahem M. Eid
[Kafrelsheikh University]
[Botany Department, Faculty of Science, Kafrelsheikh University, Kafr El-Sheikh 33516, Egypt]
[Phone number: 002010 22648840]
[Email address: [email protected]]
Author Response File: Author Response.pdf
Reviewer 2 Report
I appreciate your efforts for preparing your manuscript according to reviewer's suggestion. The paper is fine now.
Author Response
28 April 2021
Dr. Ludmiła Polechońska and Dr. Małgorzata Dambiec
The Guest Editors
Sustainability,
Dear Dr. Ludmiła Polechońska and Dr. Małgorzata Dambiec,
Please find attached the revised manuscript titled ‘Uptake prediction of eight potentially toxic elements by Pistia stratiotes L. grown in the Al-Sero Drain (South Nile Delta, Egypt): a biomonitoring approach’; sustainability-1179515, authored by Ebrahem M. Eid, Mohammed A. Dakhil, Loutfy M. Hassan, Shaimaa G. Salama and Tarek M. Galal.
On behalf of my co-authors, I thank you very much for giving us the opportunity to revise our manuscript. We appreciate the positive and constructive comments and suggestions provided by the reviewers on our manuscript. We have carefully studied the reviewers’ comments and have made revisions that are highlighted in yellow in the revised version of the manuscript. We have tried our best to revise our manuscript according to the reviewers’ comments. Please find attached the revised version of our manuscript, which we would like to submit for your kind consideration. Once again, we would like to express our great appreciation to you and the reviewers for the comments on our manuscript.
Please find below our detailed responses to each of the points raised.
---------------------------------------------------------------------------------------------------------------------
Comments and Suggestions for Authors
I appreciate your efforts for preparing your manuscript according to reviewer's suggestion. The paper is fine now.
Response: Thanks so much Sir for your time and for your positive comment.
---------------------------------------------------------------------------------------------------------------------
I would appreciate if the revised version of our manuscript would be considered for publication in a special issue of Sustainability on ‘Aquatic Plants as Bioindicators of Trace Metal Pollution’
Yours
Ebrahem M. Eid
[Kafrelsheikh University]
[Botany Department, Faculty of Science, Kafrelsheikh University, Kafr El-Sheikh 33516, Egypt]
[Phone number: 002010 22648840]
[Email address: [email protected]]
Author Response File: Author Response.pdf
