Round 1

Reviewer 1 Report

Comments and suggestions are presented in the attached file.

Comments for author File: Comments.pdf

Author Response

Response to reviewer 1:

1. 1. Lines 45, 52, 70, 85, 86, 87, 88, 100, 101. 175 (…) 596: “mining waste” instead of extractive waste (EW)? Or the study considers only extractive waste (waste rock in miming context)?

The study considers both the tailings and the waste rocks which are collectively called as extractive waste (please note the following sentences for EU Waste from extractive operations (i.e. waste from extraction and processing of mineral resources) is one of the largest waste streams in the EU. It involves materials that must be removed to gain access to the mineral resource, such as topsoil, overburden and waste rock, as well as tailings remaining after minerals have been largely extracted from the ore in https://ec.europa.eu/environment/waste/mining/index.htm).

However, to improve the readability of the manuscript we added the following lines:

Moreover, the need to find RM and CRM has pushed EU to adopt policies to promote the exploitation of waste from abandoned mining sites termed as mining waste (also called as extractive waste: (EW) and from productive cycles [7, 8, 9]. It should be noted that for the present study, extractive waste is used in the upcoming sections.

Q.2. Grain liberation size

The following sentences are mentioned in the manuscript now:

In the present study, we talked about issues with mineral liberation due to coarse particle sizes and entrainment due to very fine particles. However, we further added following text after receiving your suggestion:

To account for these factors, grain liberation size experiments should be performed, which result in increased recovery of the minerals [48]. However, due to time limitations those experiments were not carried out, and the minimum size and maximum size were considered in a more general form, by crushing and sieving the coarse fraction of the WR in size fractions (0.063-0.16 mm and 0.16-0.5 mm). Such subsample preparation was not possible for tailings, as the original size of tailings was from 0-0.063 mm. Consequently, tailings were used for dressing activities, without any crushing from original size.

Q.3. Line 26: “finite mineral resources” - by definition a “resource” is not finite. What differs is our knowledge and capacity of recovery. “Reserve” is the adequate term to be use in this sentence.

It has been modified now.

Lines 33 & 34: please review/improve the sentence. The list of CRM’s defined by EU was defined for the first time earlier (2010, “Report of the Ad-hoc Working Group on defining critical raw materials”) being, in general, annually reviewed.

It is very true however our manuscript mentioned it as: In view of the recent developments, a list of 27 critical raw materials (CRM) was identified for the EU nations in 2017, which was the first time there were 27 CRM in the list.

Line 40: “Indeed, using mining waste…” instead of “Indeed, using extractive waste…”

We could not change it.

Line 41: “…helps to minimize waste and resources…” – please review the sentence, Shouldn’t it be “…helps to minimize waste production and consumption of unexplored resources…”?

Thanks for the suggestion, it has been reviewed now.

Line 43: “…unexplored resources…” instead of “…virgin resources…”

Thanks for noticing it, we altered it now.

Line 55: “…for handling and processing waste at site…” instead of “…for handling waste at site…”

Line 77: “…conducted on tailings [30]…” instead of “…conducted by [30] on tailings…”

Yes, we amended it in the new version.

Line 79: in “for e.g. [31] presented economic” the entities/ authors. etc. ([31]) should be better referred in the text.

We referred the author in the revised form.

Line 92. “…separation and mine processing engineering…” instead of “…separation engineering…”

We altered it now.

Figure 1 – “Extractive Waste” or “Mining Waste”? (in mining activities, extractive waste is in general use to refer only the waste rock that was not processed; tailings, for instance, are not included). This Figure should be reviewed according to the previous comments.

We could not change it. However, we mentioned that for the purpose of this manuscript we used the term extractive waste in the following sentences:

Moreover, the need to find RM and CRM has pushed EU to adopt policies to promote the exploitation of waste from abandoned mining sites termed as mining waste (also called as extractive waste: (EW) and from productive cycles [7, 8, 9]. It should be noted that for the present study, extractive waste is used in the upcoming sections.

Reviewer 2 Report

This is a topical manuscript in that it addresses the potential of mine wastes to be used for a range of purposes, focusing on (a) recovery of metals that were 'missed' the first time round and (b) use of tailings as soil additives.

It focuses on the mineral processing aspects of what is required to bring tailings into use.  That side of the work seems fine, but it is not my speciality.

I do have some problems with the way in which the soils work has been done. Clearly, and as pointed out by the authors, the ability of the materials they studied to support plant life is poor.  The tests that they have used involve germination and growth of cress. Whilst an accepted method, this is perhaps best regarded as an indicator of the ability of the tailings to be useful in soils, and assesses risk to a limited extent. There is no consideration of the agronomic properties of the tailings (which I know industry addresses in some places). Of particular interest in the context of the manuscript is the pH of the tailings, measured using soil specific methods.  Given that the ores are sulphides, the pH is likely to be low, and that is likely to make them unsuitable for soil application.

So, given the conclusions of the work, I think the abstract and parts of the manuscript need to be changed to avoid the reader being led to expect these materials to be used on soils.

It would also be appropriate to compare the results obtained in this study with those used in Brazil to evaluate the suitability of rock dust for use in agriculture.  For example: http://gmga.com.br/01-evaluation-of-potentially-toxic-elements-in-mining-tailings-coming-from-beneficiation-of-volcanic-rock-in-southern-brazil/ or 

Application of andesite rock as a clean source of fertilizer for eucalyptus crop: Evidence of sustainability

Author links open overlay panelAdilson CelimarDalmora^aClaudete GindriRamos^bMarcos LeandroSilva Oliveira^bLuis FelipeSilva Oliveira^bIvo AndréHomrich Schneider^aRubens MullerKautzmann^c Show more https://doi.org/10.1016/j.jclepro.2020.120432     In addition, the section headed 'implications' contains a lot of speculation that does not relate to the evidence obtained in the study.  This needs to be carefully revised, so there is a logical flow that leads to conclusions firmly based on evidence.   Other points that are important include: 1) please avoid acronyms, such as EW (line 100-101). You know what they are, but an unfamiliar reader will soon forget. 2) Line 178: state that the plant used was 'cress', as well as giving the Linnean botanic name. 3) line 307-308: state how the samples were digested for ICP-MS analysis. 4) line 381 on - aqua not auqa. 5) line 406: explain what 'blonde peat' is. 6) Table 2: check the formatting. 7) Line 600: what is 'idoneas'?   Finally, although easy to understand, the written English would benefit enormously from correction by a native English speaker.    

Author Response

Dear Reviwer 

please find in the following the specific feedbacks to your appreciated comments.

This is a topical manuscript in that it addresses the potential of mine wastes to be used for a range of purposes, focusing on (a) recovery of metals that were 'missed' the first time round and (b) use of tailings as soil additives.

It focuses on the mineral processing aspects of what is required to bring tailings into use. That side of the work seems fine, but it is not my speciality.

I do have some problems with the way in which the soils work has been done. Clearly, and as pointed out by the authors, the ability of the materials they studied to support plant life is poor.  The tests that they have used involve germination and growth of cress. Whilst an accepted method, this is perhaps best regarded as an indicator of the ability of the tailings to be useful in soils, and assesses risk to a limited extent. There is no consideration of the agronomic properties of the tailings (which I know industry addresses in some places). Of particular interest in the context of the manuscript is the pH of the tailings, measured using soil specific methods.  Given that the ores are sulphides, the pH is likely to be low, and that is likely to make them unsuitable for soil application.

So, given the conclusions of the work, I think the abstract and parts of the manuscript need to be changed to avoid the reader being led to expect these materials to be used on soils.

It would also be appropriate to compare the results obtained in this study with those used in Brazil to evaluate the suitability of rock dust for use in agriculture.  For example: http://gmga.com.br/01-evaluation-of-potentially-toxic-elements-in-mining-tailings-coming-from-beneficiation-of-volcanic-rock-in-southern-brazil/ or 

Application of andesite rock as a clean source of fertilizer for eucalyptus crop: Evidence of sustainability

Author links open overlay panelAdilson CelimarDalmora^aClaudete GindriRamos^bMarcos LeandroSilva Oliveira^bLuis FelipeSilva Oliveira^bIvo AndréHomrich Schneider^aRubens MullerKautzmann^c Show more https://doi.org/10.1016/j.jclepro.2020.120432     In addition, the section headed 'implications' contains a lot of speculation that does not relate to the evidence obtained in the study.  This needs to be carefully revised, so there is a logical flow that leads to conclusions firmly based on evidence.   Other points that are important include:

We have revised the text as the impact on plants and the reference to the above study has been completed in the manuscript. Many thanks, for sharing this manuscript with us.

• please avoid acronyms, such as EW (line 100-101). You know what they are, but an unfamiliar reader will soon forget.

Many thanks for the comment, the EW has been changed to extractive waste at different places in the manuscript. Moreover, for increased ease in the manuscript all the abbreviations in the conclusions are removed now. Also, the WR has been changed to waste rock sparingly throughout the manuscript.

2) Line 178: state that the plant used was 'cress', as well as giving the Linnean botanic name.

Cress has been added to the section and the sentence is now modified to: The seed germination test and plant growth experiments were conducted using Cress (Lepidium sativum) seeds, following methodology described by [41, 42].

3) line 307-308: state how the samples were digested for ICP-MS analysis.

It has been added now: The heavy and light samples from shaking table experiments and sink and float samples from flotation (using 1 g/kg reagent) were analyzed for presence of elements using ICP-MS by the same methods described in Section 2.5.1.

4) line 381 on - aqua not auqa.

Thanks for noticing this. It has been done now throughout the manuscript.

5) line 406: explain what 'blonde peat' is.

It has been completed now.

6) Table 2: check the formatting.

It is completed now. This is added to manuscript now: (blond peat is a stick-free peat that allows suitable contact between seed and substrate, promoting uniform seed germination).

7) Line 600: what is 'idoneas'?

We have removed that part now, we understand that conclusions are the section that brings the work presented throughout the article from introduction and results and does not include anything new, that has not been talked throughout.

Finally, although easy to understand, the written English would benefit enormously from correction by a native English speaker.    

Reviewer 3 Report

The manuscript deals with re-usability of extractive waste at abandoned mine site, in Gorno, Italy. I appreciate the authors’ effort to collect materials for the manuscript, however, this is just a report not an academic article. The authors should extract logical and theoretical conclusions from the result.

1. In 1. Introduction, the purpose of this work is ambiguity. The last paragraph in Introduction is too long, in which the purpose may be written I assume.
2. There is no explanation about Figure 1. The contents in Figure 1 are related to the description in 2. Methodology. Hence, 2. Methodology and the sections inside should be written referring to Figure 1.
   The situation is the same for Figure 2. And the reviewer wonders the figure on the top of Figure 2 is necessary or not? There is no description about strata in northwestern Italy. If the authors wanted to indicate the location of Gorno, a white map on the top right is enough.
3. Where is the abandoned mine site? How the tailing sampling site was chosen? What is the relation between the abandoned mine site and tailings sampling site?
4. The experiments dealing with the dependence of metal recovery on pH were conducted carefully, and the highest recovery was obtained at pH 8.5. The authors should discuss why pH 8.5 is the most effective.
5. Implications is unnecessary. The contents are not directly related to the results in this work.
6. Conclusion is too long, and the reviewer is not aware of which are important conclusions. It should be more compact. Could you try to improve description?

The followings are minor mistakes.

1. I sometimes find reference number usage, such as “A recent study by [22] estimated …” (on line number 58). It should be changed to “A recent study by van Zyl et al [22] estimated ….” Please check the whole manuscript.
2. WR may stand for waste rock, right? There is no explanation about WR (WR appeared on the line number 65 for the first time
3. On line numbers 362 and 363, Ccm(3) and Ccw(3) are unnecessary. They are explained by Ccm(i) and Ccw(i).
4. On line number from 381 to 382, the concentrations of Ni and Sb are exchanged. Or the contents in Table 1 are mistake?
5. In Table 1, the concentrations of Zn are 147,367 and 10,338. Is the significant figure OK?
6. In section 3.1.2, there is no conclusion or suggestion whether EW from Gorno can be used as soil additive. Although in 5. Conclusion, a brief description concerning usability of EW as soil additive is found, it should be noted here, too.
7. On line numbers 407 and 414, Germination Index should be Plant Growth Index.
8. On line number 448, Figure 7a should be Figure 8a.
9. On line number 505, 0.016-0.5 mm should be 0.16-0.5 mm.

Author Response

Dear Reviewer

Thanks for your effort during the revision phase. Please, find below our responses to your specific comments.

1. In 1. Introduction, the purpose of this work is ambiguity. The last paragraph in Introduction is too long, in which the purpose may be written I assume.

It has been added now at the end of second paragraph only of the manuscript: Consequently, the present study focuses on assessment of recovery of raw materials from EW and the effects of EW on plants if used as additive to soil from abandoned mines of Gorno in northwest Italy. To improve the readability, additional subsections 1.1 for relevant literature and 1.2 for study objectives are also added.

1. There is no explanation about Figure 1. The contents in Figure 1 are related to the description in 2. Methodology. Hence, 2. Methodology and the sections inside should be written referring to Figure 1. The situation is the same for Figure 2. And the reviewer wonders the figure on the top of Figure 2 is necessary or not? There is no description about strata in northwestern Italy. If the authors wanted to indicate the location of Gorno, a white map on the top right is enough.

The Figure numbers for 1 and 2, are referenced twice in the text. Moreover, the figure 2 is now corrected.

1. Where is the abandoned mine site? How the tailing sampling site was chosen? What is the relation between the abandoned mine site and tailings sampling site?

Please refer to: “For the treatment of valuable ores, flotation process was used (information from historic documents maintained by Municipal Corporation of Gorno), leading to generation of tailings deposited close to Riso creek. Thus the two important types of EW present at the site are waste rock and tailings, produced due to separation and ore processing respectively of resources at the site.”

1. The experiments dealing with the dependence of metal recovery on pH were conducted carefully, and the highest recovery was obtained at pH 8.5. The authors should discuss why pH 8.5 is the most effective.

It has been added now, please find the added text as: The possible reason for this could be that Zn2+ cations (due to ZnO, Zn (OH)2 species) exhibit a marked effect on the zeta potential if they are present on the sphalerite surface in the region (pH 8–9) making the sphalerite strongly negatively charged at pH 8–9 [64].

1. Implications is unnecessary. The contents are not directly related to the results in this work.

This section has been removed now.

1. Conclusion is too long, and the reviewer is not aware of which are important conclusions. It should be more compact. Could you try to improve description?

Yes, conclusions section has been presented in concise form now.

The followings are minor mistakes.

1. I sometimes find reference number usage, such as “A recent study by [22] estimated …” (on line number 58). It should be changed to “A recent study by van Zyl et al [22] estimated ….” Please check the whole manuscript.

It has been replaced now.

1. WR may stand for waste rock, right? There is no explanation about WR (WR appeared on the line number 65 for the first time

Waste rock for WR has been inserted in the sentence now.

1. On line numbers 362 and 363, Ccm(3) and Ccw(3) are unnecessary. They are explained by Ccm(i) and Ccw(i).

The description Ccm(3) and Ccw(3) is removed now.

1. On line number from 381 to 382, the concentrations of Ni and Sb are exchanged. Or the contents in Table 1 are mistake?

The sentence has been changed now: Waste rock sample recorded the aqua regia extractable concentrations of As as 143 mg/kg, Cu as 868 mg/kg, Ni as 1063 mg/kg, and Sb as77 mg/kg.

1. In Table 1, the concentrations of Zn are 147,367 and 10,338. Is the significant figure OK?

Yes, the significant figure is OK, the reason for very high concentration of Zn is that secondary mineralization was used for ore recovery during the mining activities, Thus the Zn rich minerals are still present in high concentrations.

1. In section 3.1.2, there is no conclusion or suggestion whether EW from Gorno can be used as soil additive. Although in 5. Conclusion, a brief description concerning usability of EW as soil additive is found, it should be noted here, too.

These results serve as the indication towards the impact of EW on plants so as to assess the usability of extractive waste as soil additive. The results recorded that in the present form and without the use of amendments and fertilizers the extractive waste samples cannot be sued for growing plants.

1. On line numbers 407 and 414, Germination Index should be Plant Growth Index.

It has been changed now.

1. On line number 448, Figure 7a should be Figure 8a.

It is modified now.

1. On line number 505, 0.016-0.5 mm should be 0.16-0.5 mm.

Many thanks for noticing this, we changed 0.063-0.16 to 0.16-0.5 mm.

Round 2

Reviewer 3 Report

The reviewer appreciates the authors' faith.

The revised version is much better than the original.

The reviewer anticipates the authors continue this kind of research for sustainable society and obtain great results.