Artisanal and Small-Scale Gold Mining (ASGM): Management and Socioenvironmental Impacts in the Northern Amazon of Ecuador

Round 1

Reviewer 1 Report

 The paper aims to evaluate the socio-environmental impacts caused by artisanal and small-scale mining in the northern Ecuadorian Amazon in Northern Amazon of Ecuador, by bibliographic review and fieldwork. However, the contribution of the paper is unclear. Without a deep discussion, it is hard to tell if the proposed method has any academic merits.

I suggest the authors keep the Conclusion as itself and move the future work to the Discussion section. Conclusions should include precise, concise, and quantitative statements (if possible) about the significance of the study, and highlight any new findings.

Line 61-62: change “artisanal and small-scale mining (ASGM)” to “ASGM”.

Line 85: Please delete the period.

Line 90: km2 to km².

Author Response

Dear reviewer, we appreciate your general and specific comments. Your input as a reviewer has served to improve our manuscript. The tables have been improved considering your comments, we have initially deepened in the introduction and methodology. 

In addition, all the documents you recommended have been considered, which strengthened the bibliographic references. Finally, the discussion of the results was separated.

The comment on line 85 I have not been able to understand, I am very sorry, if it is possible to explain it better, thank you. The rest of the comments have been applied.

Thank you for all your comments.

Reviewer 2 Report

Dear Authors,

I've read your manuscript with a great interest, because I've been involved into ASGM studies myself. Indeed, your manuscript presents various information interesting to the international research audience. However, it has to be strengthened in several aspects, and I hope my recommendations will help you doing so.

• Abstract: this should be totally re-written to be focused on your findings and interpretations and to avoid too general statements.
• Tables 1 & 2: have these persons permitted to disclose their names? What is their average profile – age, gender, educational background, work experience (the latter is indicated, but not everywhere), etc.?
• Section 3: it is strongly recommended in all major international journals to separate results from interpretations. This means that you need to split this section into two sections, namely Results (=your direct findings) and Discussion (=interpretations of your findings).
• Table 6: are these true impacts or just perceived impacts? You should explain here and in the previous, methodological section. I think the factor of "just perception" (perception may differ from the reality strongly depending on the personal intelligence, curiosity, experience, etc.etc.) should be taken into account serious.
• In the section Discussion, you MIUST compare your findings with what has been already reported from the other areas of South America and the rest of the world. You have to cite various literature here, including

https://0-link-springer-com.brum.beds.ac.uk/article/10.1007/s40831-021-00394-8

https://0-www-sciencedirect-com.brum.beds.ac.uk/science/article/pii/S0048969720304174

https://0-www-mdpi-com.brum.beds.ac.uk/journal/ijerph/special_issues/asgm

https://0-www-sciencedirect-com.brum.beds.ac.uk/science/article/pii/S0013935119305171

https://0-chemistry--europe-onlinelibrary-wiley-com.brum.beds.ac.uk/doi/10.1002/chem.201704840

See also some basic literature cited in these sources, as well as the other suitable sources. Citing some of them would also be suitable to your Introduction.

• You need to write more about the general roots of the registered situation and the possible ways of its normalization. The only strict regulation may not be enough – some people may not see the opportunities for personal income other than ASGM.
• I strongly encourage you to write with more details and deeper interpretations everywhere.

Author Response

Dear reviewer, we appreciate your general and specific comments. Your input as a reviewer has served to improve our manuscript. The tables have been improved considering your comments, we have initially deepened in the introduction and methodology. 

In addition, all the documents you recommended have been considered, which strengthened the bibliographic references. Finally, the discussion of the results has been separated.

Thank you for all your comments.

Reviewer 3 Report

Line 74: "or consumed by fish and 74 crustaceans"

This does not happen directly. The emitted mercury by ASM is metallic mercury which ist not directly consumed by fish. Over a long period of time, metallic mercury can be transformed by the action of bacteria in soils into organic mecury (methylmercury) which is then bioavailable and can enter the food chain, from microrganisms and algae mainly to small crustaceans and non-carnivorous fish, which then are consumed by larger carnivorous fish which then accumulate the methylmercury.  By eating these fish, the population is intoxicatd by the very dangerous methylmercury.

Line 202: must be 1kg, definitely not 1 gram

Table 5: This table has various mistakes.

Initial exploration

This stage refers to the initial process in which artisanal miners travel long distances in search of an area with indications of gold-bearing materials.

Traveling over long distances is not necessary a destructive process. What happens indeed is that the miners invade so far untouched areas, build paths and roads, clear trees, build houses and camps, use (and spill) fuel, hunt animals, etc.

Gravel classification This process consists of classifying the auriferous gravels and separating them from the heavy sediments, with the help of small dredges and/or metal chutes.

This is technically not correct and also does not use the correct technical terms.

The first step of exploitation is mining or excavation of the gold bearing gravel. This can be done by hand (shovel) or small suction dredges. Classification means the separation of coarse stones from small sand and gravel. This is done (if applied) by sieving.

The next step is pre-concentration. This means the separation of light material (sand and gravel) from a mixed heavy minerals concentrate. This is done by "sluicing" in a wooden or metal chute with usually a rough carpet on the bottom, where heavy minerals and gold are hold back and light material overflows with the water. The carpet is washed from time to time and the pre-concentrate is collected.

Concentration and separation
In this step, the gold is concentrated and separated from the heavy sedi-
ments. The process uses a tool called a "pan", in which one to two drops of
mercury are applied. The material is then placed in the pan and circular
movements are made until the gold in the form of amalgam is obtained at the bottom of the pan

What you describe is already amalgamation!

Correct would be:

Amalgamation

The pre-concentrate (also called black sand due to its high content of black iron minerals) is then amalgamated in a pan, where mercury and water is added and the pan is shaken. Fine gold and mercury combine to coarse amalgam flakes, which then are separated from the heavy minerals by panning. The amalgam is collected for further burning.

Distillation

Finally, distillation of the amalgam consists of burning the amalgam to separate the gold from the mercury to obtain the final product, the gold, for marketing.

This is no distillation! Distillation means that a liquid is first evaporated and then converted again into liquid by cooling the gas. Destillation would be the desired process (using a retort, to recover the mercury). What happens instead is just "burning" (heating) of the amalgam to evaporate the mercury without recovering it.

Correct would be:

Burning of the amalgam

The collected amalgam is then burned. This means that mercury is evaporated by heat (e.g. using a char coal fire) and enters the atmosphere. Is can be inhaled by the operators and leads to their intoxification by metalic mercury. Usually, the largest part of mercury vapour due to its high weight is settling down arround the burning place and contaminates the soil, some of it may travel a bit further by wind. By rain and erosion this metallic mercury enters the waterways.

Author Response

The authors are very grateful to the reviewer, the time he has taken to read our manuscript has served to improve it significantly. There were some errors in the processes or steps followed in ASM, which was extracted through interviews with local miners, we believe that this is where the error could have occurred. But thanks to the knowledge of the reviewer it has been repaired, thank you very much.

Also, the minor corrections have been applied.

Again, thank you for everything, it helps us to grow in our training as researchers.

Round 2

Reviewer 2 Report

Dear Authors,

thanks for your revisions! The new version of your manuscript looks much better. However, I still see three issues to work on. Please, note that really significant improvements and additions are expected.

First, if your assessment is based on the knowledge of experts, you establish the perceived impact. For instance, you or your experts cannot conclude about contamination without in-depth geochemical analyses of water, soil, etc. Of course, this does not mean your analysis is weak. I just wish to warn that you register the impact as perceived by experts, and this should be well-articulated everywhere in the paper, and the possible differences between what is perceived and what happens in fact must be discussed. In the methodological part of the work, you need to explain all grades used in Table 6: for instance, what is the difference between contamination and alteration, and on the basis of which criteria these are established?

Second, the literature additions are fine. However, these new sources are omitted in References! Please, add.

Third, you should state (for instance, in "Conflict of Interest" or "Acknowledgements" that all persons involved as experts have permitted you to disclose their names). To be sincere, it'd be better if you can supply to the editors their written permissions.

Author Response

Dear reviewer we would like to thank you for your time in reading our manuscript in this second round. Your comments and observations have served to improve our manuscript. Thank you for being very thorough in your corrections. Thus, considering all this, the following changes have been made:

It was made very clear in the abstract, last paragraph of the introduction, methodology section that the evaluation and assignment of magnitude was based on a perception analysis considering the experience of the experts. 

In addition, a paragraph was added to the introduction about the use of this technique in other studies and the benefits in the field of research being applied in this investigation.

Finally, the bibliographical references were corrected and the consent to use the names of the interviewees was described.

Reviewer 3 Report

One last comment:

On page 12 is written:

"One fact to take into account is that three kilos of mercury are needed for each kilo of gold processed in areas near rivers, according to ASGM members, a fact that is no different in other international mining areas"

In alluvial mining (river gold) the ratio Hg:Au is usually 1:1. Mercury loss is usually by burning the amalgam. Amalgam from river gold consists usually of about 50% gold and 50% mercury, depending on particle size of the gold.

Higher ratios ocure when ore is milled (hard rock mining) and mercury is ground to small particle sizes and lost to the tailings. In hard rock mining, the ratio Hg:Au can go up to 10:1

Author Response

Dear reviewer, we really appreciate your input, in our research process it has served to strengthen the manuscript and our knowledge. The paragraph has been corrected and we have searched for articles that affirm what you have stated.

Thank you for everything, the world needs more reviewers like you.

Round 3

Reviewer 2 Report

Dear Authors, thanks for revisions!