Phytoremediation of Heavy Metals in Tropical Soils an Overview
Round 1
Reviewer 1 Report
Title of manuscript – to accept
Abstract – to accept
Key words
Maybe: plants to phytoremediation
Introduction
- 26 - Are you sure ? Soils for mining ?
L 31– ash and slag
- 83 - Please give how much?, range from ...to...%C
How much of Fe in the tropical soils ....
- 102 - Please provide definition of heave metals according to IUPAC
In table 2 - Are you sure ? These elements are not heavy metals ...
- 257 - Please add 1-2 sentences about effect heavy metals on photosynthetic ...
For examples:
Bączek-Kwinta R., Juzoń K., Borek M., Antonkiewicz J. 2019. Photosynthetic response of cabbage in cadmium-spiked soil. Photosynthetica, 57, 3, 731-739. DOI: 10.32615/ps.2019.070
L – 302 I suggest add information about using energy crops to phytoremediation
Fot instance:
Antonkiewicz J., Kołodziej B., Bielińska E.J., Popławska A. 2019. The possibility of using sewage sludge for energy crop cultivation exemplified by reed canary grass and giant miscanthus. Soil Science Annual, 70, 1, 21-33. DOI: https://doi.org/10.2478/ssa-2019-0003
L – 335- Maybe add others grassess
- 475 – Maybe ne wplant to remediation ore and other waste ....
Please mention about using crops energy to remediation of soils ...
Conclusion
Please provide species to remediation tropical soils as potential, recommended.....acording to Authors .....
Author Response
Please see the attachment
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The manuscript is a review presenting a general overview of phytoremediation in tropical soils.
The manuscript is generally well written and contains the key-elements for a review paper.
When present mobility of metals and metalloids in soils as the determining factor for their availability and leaching potential through various soil profiles, the authors should also consider methods to evaluate metals availability in soils. The Diffusive Gradients in Thin-films (DGT) is a promising tool in the assessment of bioavailable fraction of metals in soil. A short presentation of this technique will improve the quality of this paper, with appropriate citation of several relevant articles in this field:
Environmental Science & Technology 2001, 35:2602–2607; Environmental Pollution 2010, 158:3330–3337; Chemistry Central Journal 2012, 6:119; Journal of Environmental Health Science & Engineering 2014, 12:108.
Author Response
Please see the attachment
Author Response File: Author Response.pdf
Reviewer 3 Report
The paper aimed to discuss phytoremediation of heavy metals in tropical soils, which is an interesting and important perspective. The author failed to make a meaningful connection between phytoremediation of heavy metal and tropical soils. Throughout the text, phytoremediation of heavy metal and tropical soils are two parallel storylines, that only cross path in section 8 "Phytoremediation in tropical soils – advantages and limitations". Instead of making a significant conclusion or summary, section 8 simply listed research conducted on tropical plants in each families. I would like to see the authors making meaningful connections between phytoremediation of heavy metal and tropical soils, and draw meaningful summary/conclusion from existing research literatures.
Comments for author File: Comments.pdf
Author Response
Please see the attachment
Author Response File: Author Response.pdf
Reviewer 4 Report
I have found the review paper “Phytoremediation of heavy metals in tropical soils an overview” quite confusing and superficial in some points/sections. Whereas some issues should be addressed more deeply, for others it is difficult to find a link with the subject of the review paper: heavy metal phytoremediation in tropical soils.
Indeed, there are many points in which phytoremediation of heavy metals and that of organic compounds are mixed, without a proper justification in the text. Also, it is not clear when authors are giving general information valid for every soil type or specific information for tropical soils. If the focus of the paper is heavy metals phytoremediation in tropical soils, this should be clear through the whole review paper. On the other hand, there are some concepts repeated too much times in different sections.
However, I think that the object of this review paper is of great interest, due to the worldwide problem of contaminated soils and the potential for phytoremediation of the great variety of plants grown on tropical soils.
Specific comments:
Page 2, lines 50-54: This paragraph is not clear. In line 52, which factors do you refer to?
Page 2, line 60: Please include “should” before the verb “be”
Page 2, lines 68-77: These issues should be better explained. Line 70: Which characteristics do you refer to? Lines 71-72: I suppose that “latter” refer to weathering. Could you briefly explain the relationship between weathering and soil deficiencies?
Page 2, lines 78-80: This is again a very generic sentence. Expansion and collapse should be, at least, briefly explained. Also, the anthropogenic activities should be, at least, enumerated.
Page 3, lines 93-100, Page 5, lines 132-139. These two paragraphs should be put together. Information is complementary. Information in this section should be ordered in a less confusing way.
Page 5, lines 148,149: One of the two parts of this sentence is wrong:
“HM are less available when soil pH is about 6.5 to 7.0”
“Higher retention of metals and lower solubility in soil occurs at high pH values”
As “lower solubility” is the same as “less available”
Table 4: Could you also indicate the legal limits established by various countries?
Page 7, line 237: Please add references for these “few studies”
Page 9, lines 303-307: First authors say that the phytoremediation process steps varies according to the heavy metal concerned and then, they state that metals and metalloids pass only through phytoextraction and phytostabilization steps. You should be more clear.
Page 9, line 334: Can you explain more in detail the morphological adaptations?
Page 10, lines 350-354: Could you explain more in detail these hypotheses?
Page 10. Section “Phytoremediation in tropical soils”
I have not understood why some plants used for phytoremediation are in Table 5 whereas other plants families are described along the text. Is there any difference in their use for phytoremediation? Some of the plant families that appear in the text have been also studied for heavy metal remediation (eg A. hibridus, Brassica, Sesbania rostrata…).
Author Response
"Please see the attachment"
Author Response File: Author Response.pdf
Round 2
Reviewer 3 Report
My previous comments to the author---- "The paper aimed to discuss phytoremediation of heavy metals in tropical soils, which is an
interesting and important perspective. The author failed to make a meaningful connection between phytoremediation of heavy metal and tropical soils. Throughout the text, phytoremediation of heavy metal and tropical soils are two parallel storylines, that only cross path in section 8 "Phytoremediation in tropical soils – advantages and limitations". Instead of making a significant conclusion or summary, section 8 simply listed research conducted on tropical plants in each family. I would like to see the authors making meaningful connections between phytoremediation of heavy metal and tropical soils, and draw meaningful summary/conclusion from existing research literatures"----was ignored by the authors. The authors argued that "We believe that the lines that are shown between phytoremediation and tropical soils are not parallel, in that aspects of phytoremediation in tropical soils cross over into the influence of physico-chemical properties, the particular characteristics of tropical soils, and the great potential represented by the biodiversity of existing plant species; all of which provides the reader with jumping-off point from which to continue similar studies – in addition to those suggested in the text."
I read the paper very carefully for several times and I simply can't see where those two story lines crossed in the manuscript. Can you highlight those sections? Thanks!
Author Response
Reviewer's question “The paper aimed to discuss phytoremediation of heavy metals in tropical soils, which is an interesting and important perspective”. The author failed to make a meaningful connection between phytoremediation of heavy metal and tropical soils
Response: A considerable number of publications already exist concerning heavy metal phytoremediation processes, and have presented their own interesting conclusions for readers, so in this review our purpose was to give a general overview as quoted in the title "PHYTOREMEDIATION OF HEAVY METALS IN TROPICAL SOILS AN OVERVIEW”, outlining various topics that are related and influence phytoremediation processes. The objective that this paper seeks is described in abstract lines 11-19, as:
Goal: “The aim of this review is to provide a general overview of phytoremediation in tropical soils, placing special emphasis on the factors that affect this process, such as nanoagrochemicals, and highlighting the value of biodiversity among plant species that have the potential to grow and develop in soils impacted by heavy metals, as a useful resource upon which to base further research.
Reviewer's question : Instead of making a significant conclusion or summary, section 8 simply listed research conducted on tropical plants in each family
Response: Beyond simply providing a list of tropical plant species, our purpose in this section is to highlight plant species representative of the diversity of tropical soils, in order to inspire the reader’s interest to promote new studied aimed at the phytoremediation of tropical soils that have been negatively impacted by intensive agriculture, uncontrolled use of pesticides, mining pollution, and emerging pollutants that are described in the paper.( lines: 28-55, 87-97, 107-127 -164-170, 186-200,202-291) This section also references and summarizes numerous studies (in Table 5, lines 456-457), in relation to the biodiversity of plants used in phytoremediation processes and described within the text of the manuscript ( References: ref: 121,155, 158, 159,161,162, 164,166,167, 168,169,171,173,174,175,178,179,180,181,182, 183,187,191,192,193,194 ). We consider that we do not overlook the work that has been carried out with tropical plants for the phytoremediation of heavy metals, and that these were not ignored, as several examples are mentioned throughout the text
However, we respect the opinion of the reviewer, and have added to Section 8 a small discussion of the importance of phytoremediation in tropical soils, referring to other existing research works as the reviewer suggests, see “
Reviewer's question I would like to see the authors making meaningful connections between phytoremediation of heavy metal and tropical soils, and draw meaningful summary/conclusion from existing research literatures"
Response: The enormous number of plant species in Latin American tropical soils represent the highest levels of biodiversity worldwide, and form a valuable natural resource for heavy metal phytoremediation processes. However, tropical soils also experience serious environmental impacts attributed to mining, intensive use of pesticides, industrial activities, and emerging pollutants. Most of this mining occurs in the Andean countries, leading to high metal concentrations in soil and metal contamination problems (1). Phytorremediation of toxic mine sites is a long-term process. After the invasion of successional plants, the growth of potentially useful toxic metal remediating plants is inhibited. Thus, this restoration process is time consuming and will require monitoring and human assistance over time, as invasive plant species that develop rapidly in tropical soils can have catastrophic impacts on ecosystem services such as reduced habitat quality and decreased vegetation cover and diversity. (2) Most of the available metal hyperaccumulator species have limitations in commercial phytoremediation due to their slow growth rate and low biomass production (3). A good strategy would use energy crop species, as these can provide high biomass yields in a short period of time, are resistant to abiotic stress conditions, and have the ability to accumulate toxic substances (4). Therefore, the diversity of plant species in tropical soils should be taken advantage of to carry out studies that lead to the selection of hyper-accumulators that grow rapidly and produce large biomass.
References
- Utmazian, M. N., & Wenzel, W. W. 2006. Phytoextraction of metal polluted soils in Latin America. Environ Applications Poplar and Willow Working Party, 16-20. Maria N. Dos Santos Utmazian and Walter W. Wenzel.
- Chen, F., Yang, Y., Mi, J., Liu, R., Hou, H., & Zhang, S. (2019). Effects of vegetation pattern and spontaneous succession on remediation of potential toxic metal-polluted soil in mine dumps. Sustainability, 11(2), 397.
- Huang, J. W., & Chen, J. 2003. Role of pH in phytoremediation of contaminated soils. Handbook of soil acidity, 449-472.
- Hauptvogl, M., Kotrla, M., Prčík, M., Pauková, Ž., Kováčik, M., & Lošák, T. (2019). Phytoremediation Potential of Fast-Growing Energy Plants: Challenges and Perspectives–a Review. Polish Journal of Environmental Studies, 29(1), 505-516.
Reviewer 4 Report
The manuscript has considerably improved after revision. I just only recommend to check English language.
For instance I have observed these mistakes:
Line 51: this sentence is not correct. A "which" is missing before "can enhance".
Lines 88-90: This sentence should be shortened. It is too much to use three conectors one "caused by" and two "due to" in the same sentence.
Author Response
The manuscript has considerably improved after revision. I just only recommend to check English language. For instance I have observed these mistakes:
Line 51: this sentence is not correct. A "which" is missing before "can enhance".
50 Studies also suggest that plants benefit from heavy metal tolerant soil microorganisms, such as
51 growth-promoting bacteria [17] or arbuscular mycorrhizal fungi (AMF), which can enhance
52 phytoremediation of contaminated soils
Lines 88-90: This sentence should be shortened. It is too much to use three conectors one "caused by" and two "due to" in the same sentence.
87 Tropical soils are also associated with atypical behaviors, for example, expansion and collapse. Misuse and anthropogenic activities affect the quality of various types of these soils.
89 Due to changes in land use, tropical ecosystems are being altered and will face even greater pressures
90 as the human population increases, driving significant expansion and
91 intensification of tropical agriculture, especially in sub-Saharan Africa and South America.
92 [31] Anthropogenic activities such as deforestation and fragmentation affect the quality of various
93 types of tropical soil, with the biodiversity of tropical forests being especially impacted
Round 3
Reviewer 3 Report
I appreciate the author's response to my previous comments.
