Environmental Factors and Metal Mobilisation in Alluvial Sediments—Minas Gerais, Brazil
Round 1
Reviewer 1 Report
This manuscript reports an interesting study on the concentration and mobility of metals in alluvium. This type of studies is essential to identify contamination and is the basis for remediation plans. Congratulations to the authors. However, I think that authors can improve the text of the manuscript. Here are some suggestions:
- Introduction – the river São Francisco, Consciência creek and Grota Seca stream are not highlighted in Figure 1.
2.3. Spatial modelling - Geostatistical approach - Please explain the choice of variogram parameter values in Table 1
- Results
Table 2 – The statistical parameters are calculated, separately, for Conciência alluvium and Grota Seca alluvium, but these alluvia are not delimited in Figure 1 or Figure 2. For Conciência alluvium the N value is missing.
Line 237 – “pH values of sediments are essentially neutral, or near neutral” – the pH values look more “slightly acid”.
Figure 3 – The identification of the samples or the proximity to the stream should be indicated to better understanding the variation of the contaminant concentration in depth and distribution in the area.
Fig. 3A - In the legend of second yy axis the unit (m) is missing.
Fig. 3B – The unit of the elements concentrations is missing in YY axis.
Figures 4 to 7 – The location of the samples was already presented in Figure 2. That the maps resulting from the static modeling are very small, and do not allow a good visualization of the results. I suggest that the location map be removed from these figures and the Sequential Gaussian Simulation Mean Images be enlarged. Like figures in Appendix A.
In the Geochemistry of the interstitial water section the indication of the variation of pH and Eh with depth will allow to deepen the discussion about the mobility of metals.
Figure 9 – In the caption there is no relation between the fractions #1 ... # 5 with the different colours of the bars in the graphics.
- Discussion
Line 572 – “there is no significant proportionality between the soluble contents and the pH and Eh values”. Nowhere in the article are these pH and Eh values reported to support this sentence.
There is some repetition of text in the discussion and previous sections. As the manuscript is a little long, this repetition could be avoided.
The Conclusions are very extensive, they seem more like a summary of the manuscript. Please avoid repeating the introduction text.
A native speaker should be carefully proofread the text. Some sentences are too long.
Author Response
Évora, February 16th 2021
Dear Reviewer #1
We are grateful for your positive appraisal of our manuscript and for your comments, which have been fundamental to the improvement of our manuscript “Environmental factors and metals mobilisation in alluvial sediments - Minas Gerais, Brazil”
Please find below our replies to those comments. Whenever we do not agree with the suggestions or comments, we provide a suitable rebuttal.
We hope we have satisfactorily addressed all the relevant questions and improved our manuscript according to your suggestions.
Yours sincerely,
Rita Fonseca
Teresa Albuquerque
Author Response File: 
Author Response.pdf
Reviewer 2 Report
In this paper the authors did an extensive and meticulous work to define the extent of the pollution affecting an alluvial plain in Brazil. The authors studied the variation of the concentration of the main pollutants at various depth levels and how this is influenced by the type of season (wet/dry), while a geostatistical approach was used to model their distribution in the studied region. The mobility and speciation of the elements was defined, other than in sediments, also in interstitial water. The authors of the manuscript are well qualified researchers and have experience in this kind of studies. The manuscript is clear and well written. Some minor grammatical errors should be corrected. • Lines 359-368 as well as 406-412 are more suitable for the discussion • Figure 3: why the comparison between dry and wet season has been presented only for Zn? Why a different number of sampling point for each sample? If we look at only the first three sampling points (corresponding to the same depth) of samples CA2-10 and CA2-10A, the trend in Zn concentration seems the same. Please, specific dry/wet in in each graph. • Please add the color description to the legend in figure 9 caption. Why did the authors decide to not present data for Zn? • Line 645 retype “small oscillation” since it is not clear • Line 654 “which are the elements” is superfluous • Line 282 double “this” typoAuthor Response
Évora, February 16th 2021
Dear Reviewer #2
We are grateful for your positive appraisal of our manuscript and for your comments, which have been fundamental to the improvement of our manuscript “Environmental factors and metals mobilisation in alluvial sediments - Minas Gerais, Brazil”
Please find below our replies to those comments. Whenever we do not agree with the suggestions or comments, we provide a suitable rebuttal.
We hope we have satisfactorily addressed all the relevant questions and improved our manuscript according to your suggestions.
Yours sincerely,
Rita Fonseca
Teresa Albuquerque
Author Response File: Author Response.pdf
