Unintended Consequences of Urban Expansion and Gold Mining: Elevated Indoor Radon Levels in Gauteng Communities’ Neighboring Gold Mine Tailings

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

In general, the research results have shown good results, but there are several points that need to be improved:

1. Why is research related to radon gas so important and urgent to carry out? explain this in the introduction

2. What is novelty that was obtained after carrying out this research? explain

3. Figure 1 does not represent the location of the research site, it is best to use direct images taken from the researcher's camera/Google Street View

4. Based on table 2, what characteristics of houses are recommended for the community to build?

5. Based on table 5, what should the relevant community do to prevent negative impacts on the environment? explain in the discussion section

Author Response

MDPI Atmosphere

Subject: Response to reviewer’s comments

Reviewer 1

Comment 1

Comments and Suggestions for Authors

In general, the research results have shown good results, but there are several points that need to be improved: Why is research related to radon gas so important and urgent to carry out? explain this in the introduction

Response: We have responded to the aforementioned question in Lines 102 – 116 by outlining the current knowledge gap associated with indoor radon exposure in the country. In addition, the first two paragraphs show that a large number of residents may be highly exposed to elevated indoor radon exposure.

Comment 2

What is novelty that was obtained after carrying out this research? Explain

Response: We have responded to the aforementioned by outlining how the findings of this study challenge the long-held assumption of lower indoor radon concentration in South Africa due to warm climate. The novelty of this study is found in lines 464 -471

Comment 3

Figure 1 does not represent the location of the research site, it is best to use direct images taken from the researcher's camera/Google Street View.

Response: We have adopted the suggestion by utilizing Google Earth to present a better-quality image of the study area. See line 136

Comment 4 &5 Based on table 2, what characteristics of houses are recommended for the community to build? Based on table 5, what should the relevant community do to prevent negative impacts on the environment? explain in the discussion section

Response: We have added a subsection that deals specifically with recommendations for the residents. These recommendations are explained in detail in Lines 438 – 452.

Thanks

 

Reviewer 2 Report

Comments and Suggestions for Authors

Unintended Consequences of Urban Expansion and gold mining: Elevated Indoor Radon Levels in Gauteng Communities Neighboring Gold Mine Tailings

 

In this manuscript, the author points out a meaningful and important project. The analysis process is very standardized and rigorous. However, there are still several problems which need revising.

 

1.    It is suggested that more relevant information should be added to the Introduction part, including background, review of this research field and the detailed highlights and importance of this research at the end.

2.    There are many informative tables in the manuscript, however, more high-quality figures are recommended to show the analytical process and valuable results of this research.

3.    References should be updated and the author had better add more recent references to show the novelty of this research.

 

To sum up, considering the standard of the journal the overall quality of this manuscript, I suggest that it should be rejected.

Comments on the Quality of English Language

English very difficult to understand/incomprehensible.

Author Response

MDPI Atmosphere

 Subject: Response to reviewer’s comments

 Reviewer 2

Comment

It is suggested that more relevant information should be added to the Introduction section, including background, a review of this research field, and detailed highlights and the importance of this research at the end.

Response: We have revised the entire introduction to incorporate all the required key elements of the introduction section. Line 40 – 48, introduce the background of the study area, as well as factors which could elevated indoor radon exposure. Line 59 -67 provide further information on uranium levels found at these tailings. This section was important to add as it add more information that support the potential for elevated indoor radon concentrations near tailings that are known to have elevated radon’s precursors. Lines 102 – 115 provide a brief review of indoor radon exposure in South Africa, including gaps within radon strategies in South Africa. This information added more value on why this study was urgent. 

Comment

There are many informative tables in the manuscript, however, more high-quality figures are recommended to show the analytical process and valuable research results.

Response: We have deleted the table on radiation dose as this information was provided in the preceding paragraph; see line 316 Section 3.6. Furthermore, we have replaced the previous map with a better-quality map, see line 136. Furthermore, we have made significant improvements in how results were reported. See all tracked changes in the results section. Section 3, from line 200 onwards. 

 Comment

References should be updated and the author had better add more recent references to show the novelty of this research. 

Response: We have revised the manuscript and supported most of the information in this manuscript with references. The initial reference were 59, we now have about 80 references. Furthermore, we only kept relevant references in the manuscript. See citations and reference list at the end of the manuscript. See line 500, as well as citations throughout the manuscript.

 Thanks

Reviewer 3 Report

Comments and Suggestions for Authors

Thank you for the opportunity to review an interesting manuscript.

The work concerns one of the most important geo-ecological problem - the release of radon in residential areas. The problem is presented clearly and well structured. The citation corresponds to the current state of the problem. The design of the experiment is scientific, at the same time, some points that give ambiguity are indicated in the remarks. The results are reproducible when comparing 2 sites. In the illustrative material, it can be refined some of the points indicated in the remarks.

 

Remarks.

1. Since the main share of radon emission occurs in the soil, it is necessary to explain how the proximity to the tailings dump affects the soil under buildings? Or we are talking about the fact that residential buildings were constructed on old or modern tailings dumps.

2. What is the situation with tectonic faults under residential areas.

3. Line 52. Is there data on U238 content in tailings samples? Such information could significantly strengthen the theses presented in the work.

4. Line 79. What were the climatic conditions at the time of the study? Was there a significant temperature difference between June and September? Were there significant temperature variations when measuring VAR in the 2 areas?

5. Line 87. Double dots here.

6. Line 93 It would be worth adding to this map a line indication of relative length on the map. Also remove technical symbols in the legend area, “question”, “pencil”.

7. Line 93. While discussing the dust factor, the wind patterns in this area are not given, it would be extremely interesting to assess the prevailing wind directions throughout the year.

8. Line 132. Are these symbols (dots) concerned to figure 4? This should be clarified.

9. Table numeration 1,2,2,3,5.

10. 3.4. Section can be shortened because it highly repeated information from Table2. Same for 3.5 section. Also, in Table 2 (second 2^nd) some percentages look strange, (94/4 – 85.1%+4.1%), (4/6/5/84 – 4%, 6.1%, 5.1 %, 31%) and so on.

11. It seemed interlinear interval is different in some parts of the manuscript is it ok?

12. Table 5 looks excessive, because the reader has known yet average radon level and annual effective doses represents at lines 307 and 309.

13. Line 320. 21000 estimates for USA only, not for the whole world. This should be clarified.

14. Line 322. “unique contribution” seems to be an exaggerated formulation, although the work is undoubtedly valuable in its field, methodologically only a single 2-hour measurement of volumetric activity was carried out and it is hardly possible to assert the unique nature of the conclusions.

15. Line 328. Maybe “Volume Radon Activity – VAR” is a more accurate description of the indicator than IRC, because it is the activity expressed in the number of decays that is measured. Also line 335 same abbreviation IRC confused here.

16. Line 391. Sentence not completed.

17. Line 401-406. This part is confusing. How tobacco smoking can influence radon level if radon is predominantly released from soil, basements, faults and, to a lesser extent, from building materials. Obviously, aerosols, including tobacco smoke, enhance the effects of radon already present in the air, but do not affect its release.

18. Line 334: Considering radon dispersion, what is the level of radon in the ambient air in the study area?

Author Response

MDPI Atmosphere

Subject: Response to reviewer’s comments

Reviewer 3 Comments

Comment

Since the main share of radon emission occurs in the soil, it is necessary to explain how the proximity to the tailings dump affects the soil under buildings? Or we are talking about the fact that residential buildings were constructed on old or modern tailings dumps.

Response: We have clarified this issue in lines 80 – 88 of the manuscript. We have outlined how proximity to gold mine tailings may influence indoor radon concentration, considering that these gold mine tailings contain elevated uranium concentrations, which studies have shown uranium migration from the tailings.

Comment

What is the situation with tectonic faults under residential areas.

Response: Our main focus was on the proximity to gold mine tailings. We have added information on other sources of elevated indoor radon exposure, including tectonic faults, earthquakes and mine tremors. See line 65-76

 

Comment

Line 52. Is there data on U238 content in tailings samples? Such information could significantly strengthen the theses presented in the work.

Response: We have added information on uranium concentration found at the tailings, proximal tailings and other environmental media. See line 61 -64.

Comment

Line 79. What were the climatic conditions at the time of the study? Was there a significant temperature difference between June and September? Were there significant temperature variations when measuring VAR in the 2 areas?

Response: This issue has been integrated into the study results. See Table 1, Line 227, and Table 2, Line 278, which both confirmed that temperature variation was negligible between the two communities and had little influence on radon concentrations.

Comment

Line 87. Double dots here.

Response: One dot was removed; see line 129.

Comment

Line 93 It would be worth adding to this map a line indication of relative length on the map. Also remove technical symbols in the legend area, “question”, “pencil”.

Response: We have created a new map using Goggle Earth. The new map has improved image quality compared to the previous one. See line 136

Comment

Line 93. While discussing the dust factor, the wind patterns in this area are not given, it would be extremely interesting to assess the prevailing wind directions throughout the year.

Response: Wind direction information obtained from a previous study in the same community has been added. See line 131 -133.

Comment

Line 132. Are these symbols (dots) related to Figure 4? This should be clarified.

Response: Corrected in line 177

Comment

Table numeration 1,2,2,3,5.

Response: Corrected, see Table 1 (line 122), Table 2 (278), Table 3 (296).

Comment

Section can be shortened because it highly repeated information from Table2. Same for 3.5 section. Also, in Table 2 (second 2nd) some percentages look strange, (94/4 – 85.1%+4.1%), (4/6/5/84 – 4%, 6.1%, 5.1 %, 31%) and so on.

Response: Corrected by re-doing data analysis focusing on the table in question. See line 278

Comment

It seems the interlinear interval is different in some parts of the manuscript. Is it ok?

Response: Interlinear interval has been adjusted, see the manuscript

Comment

Table 5 looks excessive, because the reader has known yet average radon level and annual effective doses represents at lines 307 and 309.

Response: Table in question has been removed from the manuscript.

Comment

Line 320. 21000 estimates for USA only, not for the whole world. This should be clarified.

Response: Clarified, see line 328-329

Comment

Line 322. “unique contribution” seems to be an exaggerated formulation, although the work is undoubtedly valuable in its field, methodologically only a single 2-hour measurement of volumetric activity was carried out and it is hardly possible to assert the unique nature of the conclusions.

Response: Revised, see line 321 - 332

Comment

Line 328. Maybe “Volume Radon Activity – VAR” is a more accurate description of the indicator than IRC, because it is the activity expressed in the number of decays that is measured. Also line 335 same abbreviation IRC confused here.

Response: Suggestion adopted; see line 19, section 4.1 and 4.2

Comment

Line 391. The sentence is not completed.

Response: Sentence completed, see line 394-398

Comment

Line 401-406. This part is confusing. How tobacco smoking can influence radon level if radon is predominantly released from soil, basements, faults and, to a lesser extent, from building materials. Obviously, aerosols, including tobacco smoke, enhance the effects of radon already present in the air, but do not affect its release.

Response: Sentence in question has been revised, see line 394-398

Comment

Line 334: Considering radon dispersion, what is the level of radon in the ambient air in the study area?

Response: We have answered this question in line 341 – 342, by acknowledging that we did not measure ambient outdoor radon concentration but have used previous study finding to answer this question or to provide information on ambient radon levels.

Thanks

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript is accepted in its present state.

 

Comments on the Quality of English Language

Extensive editing of English language required.

Reviewer 3 Report

Comments and Suggestions for Authors

Thank you, i've found all manuscript corrections appropriate.