Phytoremediation of Mercury Contamination: Bibliometric Analysis

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This report entitled (Phytoremediation of mercury contamination: bibliometric analysis).   employs VOS viewer and Bibliometrix software to conduct a bibliometric analysis of 457 and 697 documents from the Web of Science (WoS) and Scopus databases, respectively, published between 2000 and 2023. The study aims to identify key trends, productive countries, leading institutions, key words, top authors in the field, co authorship, and other prevalent research themes in the field of mercury phytoremediation. The findings provide valuable insights and future research directions to enhance the effectiveness of phytoremediation strategies.

 

Originality: The use of bibliometric analysis to provide insights into research trends concerning phytoremediation for mercury contamination is a novel approach, adding a fresh perspective to the field.

Clarity: The parts of the review are generally clear and well-structured, and the presence of tables, diagrams, and maps enhances the comprehensibility of the information. These visual aids effectively summarize complex data, highlight key findings, and illustrate trends, making the content more accessible and engaging for readers.

Gap in Knowledge Identified

The review covers a significant gap in the topic of mercury phytoremediation. Which lack a comprehensive synthesis of knowledge from different sources. This gap may leads to redundant studies and hinders the identification of weak points in the research. So, by binding existing knowledge from diverse regions, researchers can prevent duplication, highlight under-researched areas, and enhance global collaboration. Addressing this gap will spotlight the critical areas needing further investigation and improve the overall effectiveness of phytoremediation strategies.

No Self-Citations

The review does not include any self-citations, ensuring an unbiased and objective analysis of the research landscape.

 

Tables and figures: Figures and tables are appropriate, properly display the content but the description of colors and shapes in the figures should be inserted below each figure to facilitate interpretation.

Conclusions: is compatible and consistent with the data presented but needs to be shortened.

References

The references cited in the review are both adequate and relevant

Supplementary materials

Supplementary materials in this review represented in tables are clear and greatly enhanced the comprehensiveness and depth of the review

 

The weakness point.

While the current review presents valuable data on studies related to the phytoremediation of mercury contamination, the discussion of results needs further development. The review touches on the importance of focusing research on finding native plants but neglects to discuss the implications of concentrating phytoremediation studies in the mentioned countries. It will be more efficient if it address how this distribution relates to factors such as industrial activities and soil nature. Additionally, the review should distinguish between studies conducted in the field as case studies and those performed in laboratories or with artificial pollution.

 

 

Author Response

Comment 1:

While the current review presents valuable data on studies related to the phytoremediation of mercury contamination, the discussion of results needs further development. The review touches on the importance of focusing research on finding native plants but neglects to discuss the implications of concentrating phytoremediation studies in the mentioned countries. It will be more efficient if it address how this distribution relates to factors such as industrial activities and soil nature. Additionally, the review should distinguish between studies conducted in the field as case studies and those performed in laboratories or with artificial pollution.

 

Response:

We appreciate your valuable suggestions to improve the discussion of the results.

We proceeded to expand the discussion of our results by adding information on a deeper exploration of the geographic distribution of studies of phytoremediation of mercury contamination. In this, we relate factors such as industrial activities, in which it is highlighted that mining activity is one of the activities that emanates more mercury contamination in the environment. In the Section 3.4. Most productive countries and organizations present the information. We also mention the distinction between field and laboratory studies, highlighting the advantages and limitations. In addition, we expanded the Points of interest in the research (section 3.10), as well as the conclusions where this information is made clearer. The supplementary material, Table S8, presents some research covering phytoremediation of mercury contamination in pot experiments and field experiments.

We have revised the manuscript according to your valuable comments and believe that these changes improved the quality and clarity of the article. We thank you again for your time and consideration in reviewing our work.

Sincerely yours,

 

Lina M Mosquera

On behalf of the co-authors

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Review of review paper titled “Phytoremediation of mercury contamination: bibliometric analysis”.

The paper used a bibliometric analysis of data related to sites contaminated with mercury and the use of plants for phytoremediation purposes.

The period of work covered by this review is sufficient from the point of view of the amount of potential data. The introduction is well written and clear.

However, in the next sections of this paper the authors provide an overview of the authors, key words and countries that work the most on this topic. At the same time, the work does not contain any additional data that would upgrade knowledge in this area.

Specific gaps of knowledge were not identified in the paper itself.  In the conclusion, general conclusions are given that do not derive from the analyzed data, but are general (to move from lab experiments to field and similar)

Author Response

Comment 1: However, in the next sections of this paper the authors provide an overview of the authors, keywords and countries that work the most on this topic. At the same time, the work does not contain any additional data that would upgrade knowledge in this area.

Response: We appreciate your feedback. We have revised the analysis section of authors, keywords, and countries, and have incorporated a more in-depth analysis that highlights the sources of funding, as well as the impact of this subject in different geographic regions, emphasizing the countries with the highest scientific production. In addition, we have incorporated more prolific institutions in this field. In the item “3.5 Keywords with the Strongest Citation Bursts”, we divide the word classes of each database into groups, to emphasize the relationships between them, which allows us to identify knowledge gaps. (Lines 538 – 593)

Comment 2: Specific gaps of knowledge were not identified in the paper itself.

Response: We have revised and strengthened the discussion of the article to identify knowledge gaps more explicitly. In section 3.5 “Points of interest in the research”, we identified areas that have not been sufficiently explored in the literature, such as mercury phytoremediation plants, where it is evident that studies under field conditions in different ecosystems are needed. Likewise, genetic engineering studies, and assisted phytoremediation studies for the improvement of this remediation strategy, such as the use of chelating agents and phytoremediation assisted by microorganisms, are included. Finally, the topic of mercury detoxification mechanisms in plants was discussed.

This information can be corroborated in item 3.10, lines 587 - 740.

Comment 3: In the conclusion, general conclusions are given that do not derive from the analyzed data, but are general (to move from lab experiments to field and similar).

Response: We have reworded the conclusions section to ensure that the conclusions are based on the results obtained through our bibliometric analysis. Now, the conclusions directly reflect the observed data and trends, referring to major keywords, cross-country collaborations, and specific gaps in current research. In addition, we have eliminated generalizations that were not directly supported by the data and have provided more precise conclusions based on the results obtained, as well as limitations obtained in our study.

 

 

We have revised the manuscript according to your valuable comments and believe that these changes improved the quality and clarity of the article. We thank you again for your time and consideration in reviewing our work.

 

 

 

Sincerely yours,

 

Lina M Mosquera

On behalf of the co-authors

Reviewer 3 Report

Comments and Suggestions for Authors

Dear Authors,

You have done a great job of collecting, analyzing, structuring of publications, of author composition, co-operation between authors and countries, and keywords relevant to the review topic. However, please consider recommendations that may improve your review.

 1. Please, consider possibility to include paragraph with explanation of definition “Phytoremediation” in section of  “Introduction”. The appropriate place for this is between lines 72-74. Please clarify, are Phytoremediation and phytorhizoremediation the same thing, or different remediation technologies?  Also, please, explain difference between “Phytoremediation” and "Bioremediation". Since these terms are similar and important concepts for remediation of contaminated areas - devote a separate paragraph in the “Introduction” to this topic. It is important for readers because between these definitions are confusion.

 2. Please, explain, why did you use such a narrow range of query sets in your literature search (the section of “Materials and Methods”)? On this reason, important literature on phytoremediation, included in Wos and Scopus databases, was left out of the search.

 As a trivial example, an article referenced in Wikipedia as a source for the definition of phytoremediation was not included in your review: Das, P. (2018). Phytoremediation and Nanoremediation: Emerging Techniques for Treatment of Acid Mine Drainage Water. Defence Life Science Journal, 3(2), 190-196. https://doi.org/10.14429/dlsj.3.11346.  (Wos, Q4). Also, many other articles directly related to the topic of analysis were not included in the review. For example:

González-Reguero, D., Robas-Mora, M., Probanza Lobo, A. et al. Bioremediation of environments contaminated with mercury. Present and perspectives. World J Microbiol Biotechnol 39, 249 (2023). https://doi.org/10.1007/s11274-023-03686-1 (WoS, Q2);

Raklami A-M, Abdelilah AU, Oufdou Khalid AU, Baslam Marouane TI (2022) Plants—Microorganisms-Based bioremediation for heavy metal cleanup: recent developments, phytoremediation techniques, regulation mechanisms, and molecular responses. Int J Mol Sci 23. https://doi.org/10.3390/ijms23095031,  (WoS, Q1)

Sitarska M, Traczewska T, Filarowska W et al (2023) Phytoremediation of mercury from water by monocultures and mixed cultures pleustophytes. J Water Process Eng 52:103529. https://doi. org/10.1016/j.jwpe.2023.103529 (WoS, Q1)

Rojas-Solis D, Larsen J, Lindig-Cisneros R (2023) Arsenic and mercury tolerant rhizobacteria that can improve phytoremediation of heavy metal contaminated soils. Peer J 11:e14697. https://doi. org/10.7717/peerj.14697 (WoS, Q1)

Tiodar, E.D.; Văcar, C.L.; Podar, D. Phytoremediation and Microorganisms-Assisted Phytoremediation of Mercury-Contaminated Soils: Challenges and Perspectives. Int. J. Environ. Res. Public Health 2021, 18, 2435. https://doi.org/10.3390/ijerph18052435  (WoS, Q2)

And others.

Limiting the review to an academic database leaves out publications that may provide very valuable information on the potential of local flora to accumulate mercury compounds. This is especially true for Latin American and Asian countries, which often publish results in non-academic journals. For example, the article of (Ratnawati, R., & Faizah, F. (2020). Phytoremediation of Mercury Contaminated Soil with the Addition of Compost. Journal of Engineering and Technological Sciences, 52(1), 66-80. https://doi.org/10.5614/j.eng.technol.sci.2020.52.1.5) contains information on very promising plants Sansevieria trifasciata, Celosia plumose, effective in remediation of mercury-contaminated soil. However, Tiodar et al (2021) (Wos) had not mentioned these plants in the review, which provides a list of promising species for soil remediation of mercury contamination.

 3. Therefore, please, to improve your review, consider expanding your literature search by including additional query sets (Bioremediation, Biosorption of Hg, Phytoextraction of Hg etc). Also, it would be very useful to include the countries most associated with mercury contamination in the search dataset.

 4. In addition, please, expand your search range by enabling CrossRef scientific resources. VOSviewer soft works with data from most of the leading scientific metadata databases and can even automatically download information from open APIs, including CrossRef. Not all-important publications are included in Wos and Scopus databases, so CrossRef will help to identify such publications.

 5. In the “Results and Discussion section”, please improve the quality of Figures 3,4,5,6,7 - the captions should be clearly visible and readable.

6. In Table 2, please include the country for each prolific institutions in phytoremediation of mercury contamination. It would also be useful to expand the list of prolific institutions and countries developing phytoremediation of mercury contamination according to your ranking list. Please, find a way to provide more information about prolific institutions and countries where they are located.

7. A comparison of the way information is presented in your review and in the review you cited (Valdiviezo Gonzales et al, 2023) reveals a high degree of similarity. Please, emphasize the difference and advantages of your way of presenting the data and your review compared to the review of Valdiviezo Gonzales et al, (2023).

 8. You have found that most productive countries and organizations are China, India, and Spain with the highest production in WoS; India, China, and the United States have the highest production of documents in In Scopus. Please discuss the subjective circumstances that influence the publication activity of researchers in certain countries. These circumstances may include the funding of science and the ability for authors to publish in journals that are highly ranked and high cost for publication, the income level of the population, the requirements of scientific institutions for publication activity and publications in certain journals.  Such a discussion is very relevant and of great interest to research readers.

9. Please, check the reference list as it contains double references:

 (6 - 45). Liu, Z.; Chen, B.; Wang, L. AO.; Urbanovich, O.; Nagorskaya, L.; Li, X.; Tang, L. A review on phytoremediation of 719 mercury-contaminated soils. J. Hazard. Mater. 2020, 400, 123138. https://doi.org/10.1016/j.jhazmat.2020.123138 720

(29-77). Liu, Z.; Wang, L.; Ding, S.; Xiao, H. Enhancer assisted-phytoremediation of mercury-contaminated soils by Oxalis 802 corniculata L., and rhizosphere microorganism distribution of Oxalis corniculata L. J. Ecotoxicol Environ Saf. 2018, 160, 171–803 177. https://doi.org/10.1016/j.ecoenv.2018.05.041. 804

 

(32-50). Mao, G.; Shi, T.; Zhang, S.; Crittenden, J.; Guo, S.; Du, H. Bibliometric analysis of insights into soil remediation. J. Soils 689 Sediments. 2018, 18, 7, 2520–2534. https://doi.org/10.1007/s11368-018-1932-4 690

(68-80). Sharma, P.; Chaturvedi, P.; Chandra, R.; Kumar, S. Identification of heavy metals tolerant Brevundimonas sp. from 779 rhizospheric zone of Saccharum munja L. and their efficacy in in-situ phytoremediation. J. Chemosphere. 2022, 295, 133823. 780 https://doi.org/10.1016/j.chemosphere.2022.133823. 781

(52-76). Wang, J.; Xia, J.; Feng, X. Screening of chelating ligands to enhance mercury accumulation from historically mercury-736 contaminated soils for phytoextraction. J Environ Manage. 2017, 186, 233–239. 737 https://doi.org/10.1016/j.jenvman.2016.05.031. 738

 Thank you for your effort for preparing of manuscript and hope that recommendations would be useful for improve of your manuscript.

Good luck!

Comments for author File: Comments.pdf

Author Response

Comment 1:

Please, consider possibility to include paragraph with explanation of definition “Phytoremediation” in section of “Introduction”. The appropriate place for this is between lines 72-74. Please clarify, are Phytoremediation and phytorhizoremediation the same thing, or different remediation technologies? Also, please, explain difference between “Phytoremediation” and "Bioremediation". Since these terms are similar and important concepts for remediation of contaminated areas - devote a separate paragraph in the “Introduction” to this topic. It is important for readers because between these definitions are confusion.

Response:

We have added a paragraph in the Introduction section where we explain in detail the terms “phytoremediation and bioremediation” (paragraph 3, lines 62 - 77). This allows us to clarify the relationship between the differences between these concepts to avoid confusion among readers.

On the other hand, we present the differences between the terms phytoremediation and phytoremediation:

Phytoremediation: strategy used for the in-situ elimination of many contaminants through a series of processes carried out by different plant species. In contrast, rhizoremediation: is based on the capacity of soil microorganisms to absorb, transform, and degrade contaminants (Vernai et al., 2017).

 

Phytorhizoremediation: It is a specific type of phytoremediation that involves both plants and their associated rhizosphere microbes, and has been described as an effective strategy for the removal and/or degradation of organic and inorganic pollutants from soils (Vernai et al., 2017, Kuiper et al., 2004)

 

References:

 

Kuiper, I., Lagendijk, E. L., Bloemberg, G. V., & Lugtenberg, B. J. (2004). Rhizoremediation: a beneficial plant-microbe interaction. Molecular plant-microbe interactions, 17(1), 6-15.

 

Vergani, L., Mapelli, F., Zanardini, E., Terzaghi, E., Di Guardo, A., Morosini, C., ... & Borin, S. (2017). Phyto-rhizoremediation of polychlorinated biphenyl contaminated soils: An outlook on plant-microbe beneficial interactions. Science of the Total Environment, 575, 1395-1406.

 

Comment 2:

 

 Please, explain, why did you use such a narrow range of query sets in your literature search (the section of “Materials and Methods”)? On this reason, important literature on phytoremediation, included in WoS and Scopus databases, was left out of the search.

 

Response:

 

 It is important to note that the selection of this period was made due to the low volume of publications (less than 20) before 2000 (Lines 154 -155).

 

It should be mentioned that the document was written in mid-July 2023, therefore, our range of searches was limited up to June 2023. Now, the first documents related to this topic, according to the search equation used in the databases, show that before 2000, the number of publications was relatively small (less than 20 publications). As shown in Figure 2, more than half of the articles were published between 2017 and 2023. The fluctuating trend in the annual number of publications indicates that this field has gained more attention in recent years.

 

• The following document was not included because it was not outside our search range (January 2000 to June 2023):

“González-Reguero, D., Robas-Mora, M., Probanza Lobo, A., & Jiménez Gómez, P. A. (2023). Bioremediation of environments contaminated with mercury. Present and perspectives. World Journal of Microbiology and Biotechnology, 39(9), 249. https://doi.org/10.1007/s11274-023-03686-1  (WoS, Q2)”.

 

• Regarding the paper: Raklami, A., Meddich, A., Oufdou, K., & Baslam, M. (2022). Plants-Microorganisms-based bioremediation for heavy metal cleanup: Recent developments, phytoremediation techniques, regulation mechanisms, and molecular responses. International Journal of Molecular Sciences, 23(9), 5031. https://doi.org/10.3390/ijms23095031 (WoS, Q1). It should be emphasized that although the search equation (“phytoremediation“) AND (”mercury“ OR “Hg”) AND (”plant*“ OR “Phyto*” OR ‘vegetation’ OR ‘biomass’ OR ‘hyperaccumulator’ OR *accumula*)” was used, it is possible that not all possible results were returned. In addition to the above, initially, the title and abstract were reviewed, verifying that keywords such as phytoremediation and mercury were included. This was the first review that was performed, then the articles that were not included in this first filter were reviewed again, and at least the term heavy metals was included, to completely review the document and verify that mercury was included in the set of heavy metals. Perhaps, because of these limitations in our search, articles like this one were excluded. But we have already proceeded to add it to the search.

 

The following papers are among the papers found in WoS (458) and Scopus (698):

 

• Sitarska, M., Traczewska, T., Filarowska, W., Hołtra, A., Zamorska-Wojdyła, D., & Hanus-Lorenz, B. (2023). Phytoremediation of mercury from water by monocultures and mixed cultures pleustophytes. Journal of Water Process Engineering, 52, 103529.

https://doi.org/10.1016/j.jwpe.2023.103529 (WoS, Q1).

 

• Rojas-Solis, D., Larsen, J., & Lindig-Cisneros, R. (2023). Arsenic and mercury tolerant rhizobacteria that can improve phytoremediation of heavy metal contaminated soils. PeerJ, 11, e14697. https://doi.org/10.7717/peerj.14697 (WoS, Q1).

 

• Tiodar, E. D., Văcar, C. L., & Podar, D. (2021). Phytoremediation and microorganisms-assisted phytoremediation of mercury-contaminated soils: challenges and perspectives. International Journal of Environmental Research and Public Health, 18(5), 2435. https://doi.org/10.3390/ijerph18052435 (WoS, Q2)

 

 

Comment 3: Therefore, please, to improve your review, consider expanding your literature search by including additional query sets (Bioremediation, Biosorption of Hg, Phytoextraction of Hg etc). Also, it would be very useful to include the countries most associated with mercury contamination in the search dataset.

 

 

Response:

 

We appreciate your comments and suggestions regarding the expansion of the literature search, particularly about including additional terms, however, the scope of our bibliometric analysis was to delve deeper into the terminology of phytoremediation, within our search equation the term “phyto*” was included, therefore, the term phytoextraction is also covered. The documents returned by the search equation were filtered to specifically select those that contributed most directly to our bibliometric article.

 

Regarding the inclusion of the most affected countries, we appreciate this suggestion. Although our study did not focus on an exhaustive geographical analysis, we believe that the general trends in mercury contamination are well represented in the bibliometric results obtained.

 

Comment 4:

 

 In addition, please, expand your search range by enabling CrossRef scientific resources. VOSviewer soft works with data from most of the leading scientific metadata databases and can even automatically download information from open APIs, including CrossRef. Not all-important publications are included in Wos and Scopus databases, so CrossRef will help to identify such publications.

 

Response:

 

We appreciate your comment about enabling CrossRef resources to broaden the search range in our bibliometric analysis, and we understand the relevance of using these resources to identify publications that are not included in the WoS and Scopus databases. However, we consider that our study is focused on identifying trends in phytoremediation of mercury contamination, we consider that the databases used (WoS and Scopus), offer a relevant representation of the scientific literature in this area, as they are considered the most complete databases in terms of metadata quality. In addition, these databases include the most influential publications with a high number of citations, which are the core of our paper. It is worth mentioning that broadening the search to include publications that were not present in WoS or Scopus may have diluted the findings somewhat by including sources of lower quality or academic impact.

 

Comment 5:

 

In the “Results and Discussion section”, please improve the quality of Figures 3,4,5,6,7 - the captions should be clearly visible and readable.

 

Response:

 

We have revised all tables and graphs, improving their legibility and clarity, both in the article document and in the supplementary material. Similarly, figures and tables are loaded independently as zip files in the Figures, Graphics, Images section.

 

• Figure 3 (See page 10).
• Figure 4 (See page 13).
• Figure 5 (See page 15).
• Figure 6 (See page 19).
• Figure 7 (See page 23).

 

Comment 6:

 

 In Table 2, please include the country for each prolific institutions in phytoremediation of mercury contamination. It would also be useful to expand the list of prolific institutions and countries developing phytoremediation of mercury contamination according to your ranking list. Please, find a way to provide more information about prolific institutions and countries where they are located.

 

Response:

 

Thank you for your suggestion to include the countries in Table 2. We include the country information for each prolific institution involved in the phytoremediation of mercury contamination. We have added the 15 most prolific institutions (see pages 11 and 12).

 

Comment 7:

 

A comparison of the way information is presented in your review and in the review you cited (Valdiviezo Gonzales et al, 2023) reveals a high degree of similarity. Please, emphasize the difference and advantages of your way of presenting the data and your review compared to the review of Valdiviezo Gonzales et al, (2023).

 

Response:

 

Valdiviezo Gonzales et al. (2023), in their article “Scientometric study of treatment technologies of soil pollution: Present and future challenges”, present current technologies and their combinations for the remediation of contaminated soils, they also discuss various soil remediation techniques and mechanisms, including physical, chemical, and biological remediation techniques, being the biological technique of phytoremediation the keyword with the highest number of occurrences in the WoS and Scopus databases, which allowed us to identify the degree of similarity with our document.

 

We could say that the main difference lies in the fact that our paper, we are only based on the phytoremediation of a single pollutant, in this case, mercury, while Valdiviezo Gonzales et al., 2023, covers a broader topic, presents current technologies and their combinations for the remediation of soils contaminated with organic and inorganic pollutants, such as heavy metals. They also include physical, chemical, and biological remediation techniques, with the biological technique of phytoremediation being the keyword with the highest number of occurrences in the WoS and Scopus databases.

 

Regarding similarities, both documents use the WoS and Scopus databases and provide a parallel through figures of the annual publication rate, including the number of published documents. Both documents use VOSviewer software to present research sources, countries with the highest number of publications, and word co-occurrence. The fact that "Phytoremediation" is the keyword with the highest number of occurrences in the document presented by Valdiviezo-Gonzales et al. (2023) indicates that this field has remained relevant over time. As a result, there were similarities in the outcomes of both documents, for example, in terms of subject areas, environmental sciences covered most of the publications. Likewise, the most prolific countries were China, the United States, India, and Spain, and the main research sources were Environmental Science and Pollution, Chemosphere, Journal of Hazardous Materials, and Science of the Total Environment.

 

In general, the use of bibliometric analysis allows for a clearer examination of research interests, as data mapping enables visualization of the network formed between countries, association of related keywords, and other characteristics.

 

 

Comment 8:

You have found that most productive countries and organizations are China, India, and Spain with the highest production in WoS; India, China, and the United States have the highest production of documents in Scopus. Please discuss the subjective circumstances that influence the publication activity of researchers in certain countries. These circumstances may include the funding of science and the ability for authors to publish in journals that are highly ranked and high cost for publication, the income level of the population, the requirements of scientific institutions for publication activity and publications in certain journals. Such a discussion is very relevant and of great interest to research readers.

 

Response:

 

In general, global emissions are mostly caused by human activity, the static burning of fossil fuels, and biomass, accounting for about 24% of emissions. However, small-scale artisanal gold mining represents nearly 38% of total global emissions and was the main source of emissions in South America and sub-Saharan Africa (The United Nations Environment Programme (UN Environment, 2019). In addition, mercury mines are one of the persistent anthropogenic sources of environmental contamination. Historical mining and cinnabar ore retorting release many elemental Hg (Hg⁰) and water-soluble Hg compounds into nearby surroundings (Qiu et al., 2005, 2013), and generate numerous wastelands composed of mercury-enriched mine tailings (calcines) adjacent to abandoned retorts and smelters (Z. Liu et al., 2020a).

 

China is the country with the most publications related to the phytoremediation of mercury pollution. This could be attributed to the fact that, despite being rich in plant resources and preserving various ancient plants, including more than 14000 plant species, significant amounts of mercury-enriched wastelands are found in the Wanshan mining region. Mercury concentrations in calcines have been recorded as high as 4400 μg/g (Qiu et al., 2005), continuously releasing mercury into surrounding ecosystems even after the mercury mines have been abandoned for several decades, emitting Hg⁰ and secondary Hg compounds through natural weathering and runoff into the air, soil, and water, entering the biota (David Kocman et al., 2011; Gosar & Žibret, 2011; Tomiyasu et al., 2012). Due to the large cinnabar ore reserves and elemental Hg production, Wanshan was once called the "Mercury Capital" of China. Thus, the abundant plant resources and high mercury concentrations have provided the basis for the evolution of accumulator plants (Qian et al., 2018). Furthermore, the Chinese government has actively been improving environmental quality in recent years and has invested significant financial and human resources in remediating contaminated soils (Q. Yang et al., 2018; Z. Yang et al., 2021). The most prolific institutions and authors come from this country (Table 2 and Table S1). It is also worth noting that the three main sources of funding for research related to the phytoremediation of mercury contamination come from China: the National Natural Science Foundation of China, the Ministry of Science and Technology of the People's Republic of China, and the National Key Research and Development Program of China.

 

Similarly, countries such as the United States and Spain have large-scale mercury mineralization zones distributed along the world’s plate margins. For example, the New Almaden mine in the United States and the Spanish Almaden mine (the largest mercury mine in the world), with approximately 34000 mg/kg of mercury, where the smelting process discharges a large amount of Hg into the environment (Corella et al., 2017; Z. Liu et al., 2020a). Furthermore, the United States was the first country to actively participate in this field of study, indicating that it was a pioneer in this area (P. B. A. Nanda. Kumar et al., 1995; van der Ent et al., 2013)

 

It is also important to mention that in countries such as Colombia, Brazil, Southeast Asian countries, and some African countries, gold mining also causes severe mercury contamination (Chen et al., 2016; Z. Liu et al., 2020a; Palacios-Torres et al., 2018).

 

Therefore, due to the remediation of large amounts of mercury-contaminated farmlands, phytoremediation, as an eco-friendly and efficient technology for the treatment of contaminated soils, has received significant attention and application in different countries.  See lines (269-314).

 

Comment 9:

 

 Please, check the reference list as it contains double references:

 

Response:

 

(6 - 45). Liu, Z.; Chen, B.; Wang, L. AO.; Urbanovich, O.; Nagorskaya, L.; Li, X.; Tang, L. A review on phytoremediation of 719 mercury-contaminated soils. J. Hazard. Mater. 2020, 400, 123138. https://doi.org/10.1016/j.jhazmat.2020.123138720

 

(29-77). Liu, Z.; Wang, L.; Ding, S.; Xiao, H. Enhancer assisted-phytoremediation of mercury-contaminated soils by Oxalis 802 corniculata L., and rhizosphere microorganism distribution of Oxalis corniculata L. J. Ecotoxicol Environ Saf. 2018, 160, 171–803 177. https://doi.org/10.1016/j.ecoenv.2018.05.041. 804

 

(32-50). Mao, G.; Shi, T.; Zhang, S.; Crittenden, J.; Guo, S.; Du, H. Bibliometric analysis of insights into soil remediation. J. Soils 689 Sediments. 2018, 18, 7, 2520–2534.

https://doi.org/10.1007/s11368-018-1932-4

 

(68-80). Sharma, P.; Chaturvedi, P.; Chandra, R.; Kumar, S. Identification of heavy metals tolerant Brevundimonas sp. from 779 rhizospheric zone of Saccharum munja L. and their efficacy in in-situ phytoremediation. J. Chemosphere. 2022, 295, 133823. 780. https://doi.org/10.1016/j.chemosphere.2022.133823. 781

 

(52-76). Wang, J.; Xia, J.; Feng, X. Screening of chelating ligands to enhance mercury accumulation from historically mercury-736 contaminated soils for phytoextraction. J Environ Manage. 2017, 186, 233–239. 737  https://doi.org/10.1016/j.jenvman.2016.05.031

 

 

We appreciate your thoughtful comment about the duplicate references in our list. We have carefully reviewed the references section and confirmed that there are indeed duplications in the citations you mention.

 

In the revised version of the manuscript, we corrected this error by removing the duplicate references and ensuring that the numbering of citations is correct and consistent throughout the paper.

 

Thank you again for pointing out this area of improvement.

 

We have revised the manuscript according to your valuable comments and believe that these changes improved the quality and clarity of the article. We thank you again for your time and consideration in reviewing our work.

 

Sincerely yours,

 

Lina M Mosquera

On behalf of the co-authors

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

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Reviewer 3 Report

Comments and Suggestions for Authors

Dear Authors,

 Your manuscript have been drastically improved, as a result of which it may be of induce increased interest to readers as it contains a lot of unique and useful information. Thank you for your efforts.

 For the final completion of the manuscript, please eliminate small technical errors:

1. In the title of Table 2, replace the numbers 105 with 15;

2 Please, check the reference list as it contains double references:

 5-49. Liu, Z.; Chen, B; Wang, L. A.O.; Urbanovich, O.; Nagorskaya, L.; Li, X.; Tang, L. A review on phytoremediation of mercury-842 contaminated soils. J. Hazard. Mater. 2020, 400, 123138. https://doi.org/10.1016/j.jhazmat.2020.123138

 43-91. Shi, D.; Xie, C.; Wang, J.; Xiong, L. Changes in the structures and directions of heavy metal-contaminated soil remediation 939 research from 1999 to 2020: A bibliometric & scientometric study. J. Environ Res Public Health. 2021, 18, 7358. 940 https://doi.org/10.3390/ijerph18147358

 70-110. Liu, L.; Li, W.; Song, W.; Guo, M. Remediation techniques for heavy metal-contaminated soils: Principles and applicability. 1003 J. Environ Sci Technol. 2018, 633, 206-219. https://doi.org/10.1016/j.scitotenv.2018.03.161

 Best wishes and continued success.

Comments for author File: Comments.docx