Geochemical and Advanced Electron Microscopical Characterisations of Artisanal Gold Mining Rejects in Colombia

Round 1

Reviewer 1 Report

Title: Particle dynamics of artisanal gold mining rejects in Colombia

Manuscript ID: sustainability-1912004

Authors: Akinyemi et al.

 

Dear Authors,

 

Thank you for the opportunity to read your article. I found the topic is interesting and fundamental. Generally speaking, the methods and results need more clear explanation and detail discussion with fair point of view. Your statements/discussions are often not based on your results. I suggest that this article will be revised extensively before its re-submission for another review process if applicable. Honestly speaking, this article is not ready for peer review. As a conclusion, I recommend its major revision/rejection at this state.

 

I hope my comments are helpful.

Good luck,

A reviewer

 

Major concerns:

“Article title”

->Please consider revising the title by reflecting the contents of the study. For example, there is no contents of “dynamics” in this article but all the contents are rather static. You may also add some keywords specific to this study, for example, electron microscope and X-ray analyses.

 

“Keywords”

->Please consider providing keywords that are not used in the article title.

 

“1. Introduction”

-Please consider focusing your introduction directly on your study and minimizing general background of artisanal gold mining.

 

“2. Materials and Methods”

“2.1 Study area and general context”

- Please consider sending the information given in this section to introduction since all the information is literature review.

 

“2.2. Raw samples”

-Figure 1: Please consider removing this figure or add more information (e.g. geological map) there. The current figure does not have more value than the coordinates that can be written in the text.

-Figure 2: Please consider explaining the figure. If you do not, please consider removing it.

-Lines 91-92: “…the collected samples were completely homogenized…”->Please consider mentioning how you homogenized your samples. Splitting? Quartering?

 

“2.3. Analytical methods”

-In general, please consider (a) stating more details of the experimental procedure in this section and (b) introducing the equipment you used and showed the results in this article.

(a)

For example, for SEM imaging, please consider stating the way you deposited your sample(s) in an SEM chamber, detector type (SE? BSE?), accelerating voltage, and working distance. Also, please consider explaining how you analyzed your images. Those information would be helpful for future researchers. This comment also applied to all the characterization methods introduced in this section.

doi.org/10.1016/j.actamat.2005.12.014

doi:10.3390/electronics8101202

(b)

In this article, did you show the results you obtained with Raman, SAED, MBD? If not, please consider removing those phrases from this section.

 

“3. Results”

-In general, please consider describing and discussing the results with a fair point of view. This comment also applies to the section “4. Discussion”. Please see my specific comments below.

-Lines 148-149: “…clay particles of 1 µm size and Fe-oxyhydroxides of 500 nm size were also detected.”->Please consider showing the images and SEM/TEM-EDS results in order to justify your statement.

-Figures 3-9: In the figure title, please consider stating the sample name.

-Figure 4: (a) In the figure title, please consider clearly mentioning the title for the main figure and sub-figure. (b) Please consider providing larger letters for mineral names and their equations.

-Line 186: “…goethite.”->Please consider showing the results indicating the presence of goethite.

-Lines 197-198: “…a dynamic correlation…”->Please consider providing more details about a dynamic correlation identified from static images, or removing this phrase from the statement.

-Lines 234-236: “Figure 6 illustrates the transformations of cubic and spherical pyrites into jarosite…”->Please consider providing the support of your statement in addition to those images. Since the sizes of jarosite (about 10-20 nm) and pyrite (about 20 µm) are quite different, your statement is not so convincing.   

-Lines 238-239: “…the EDSs analysis revealed that different types of PHEs, including Cd, Hg, Ti, and Sr were also found...”->Please consider showing your results indicating this point.

 

“4. Discussion”

-Figure 8: (a) “Figure 8: Typical pure hematite containing a minor portion of aluminosilicates.”->Hematite containing a minor portion of aluminosilicates? Pure hematite should not contain other minerals? (b)“Figure 8…containing…aluminosilicates.”->Please consider stating your justification of the presence of aluminosilicates. From your EDS results, there is no strong evidence of the presence of aluminosilicates. (c) Please consider pointing out which point or area within the image you bombarded X-ray for EDS analysis. (d) In case, you did SEM-EDS analysis, please clearly mentioned it in the figure title and there is no proof of the presence of aluminosilicates in the hematite imaged under TEM since the spatial resolution of SEM-EDS is larger than several µm and impossible to match your TEM image in 10 nm with SEM-EDS results obtained in larger than µm order.

-Figure 9: Please consider removing this figure as there is no justification of fixation of Hg by the Fe-nanominerals unless you have point elemental analysis within this specific mineral particles/aggregates.

 

“5. Conclusion”

-In this section, please consider providing the good summary of your study in agreement with the results presented in the article.

-Lines 325-326: “The results showed that the amount of As, Hg, and Zn were highest in the clay particles.”->Please consider revising this statement as you did not inform the amount of those elements in this article.

 

Minor concerns:

-Please consider polishing English more. You may use some of my comments above for this purpose.

 

Author Response

See the attachment

Author Response File: Author Response.pdf

Reviewer 2 Report

The manuscript describes the practices of illegal gold mining activities in Colombia and its impact on environment and inhabitants. The ambition of the study is to describe the mineralogical processes of interactions between minerals and selected potentially hazardous elements. The context of the study is interesting and serious. The main findings of the study (bindings of As, Hg and Zn on clay particles) is not very surprising, nevertheless the detail mineralogy of the process is the contribution to the field of interest. The manuscript formal level needs some partial corrections: r. 15: potentially hazardous element (PHE) - potentially hazardous elements (PHEs) is better. The References must be checked carefully, because some names of the journals are not written correctly with capitals - r. 357, 402, 408..What about reference r. 382???

Author Response

See the attachment

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Dear Authors,

As all the comments were addressed to some extent, I would suggest the journal accept this article for its publication.

Best regards,
A reviewer