Magnesium Coprecipitation with Calcite at Low Supersaturation: Implications for Mg-Enriched Water in Calcareous Soils
Round 1
Reviewer 1 Report
Very nice SEM pictures. I would put them more central. And describe more about them.
Nice article
Author Response
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Author Response File: 
Author Response.pdf
Reviewer 2 Report
Please refer to the PDF document for the review.
Comments for author File: Comments.pdf
Author Response
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Author Response File: Author Response.pdf
Reviewer 3 Report
see file
Comments for author File: Comments.pdf
Author Response
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Author Response File: Author Response.pdf
Reviewer 4 Report
This manuscript is an experimental study on the coprecipitation of magnesium with calcite at low supersaturations. Solids that were coprecipitated from slightly supersaturated solutions were analyzed using ICP-OES and ICP-MS as well as SEM-EDX. The authors derive the Guggenheim parameter for the Mg-calcite solid solution. Furthermore, the authors evaluate the effect of clay mineral on the incorporation of Mg into calcite. This study provides a sound and easily understandable justification for the relevance of this research. Overall, this manuscript should be considered for publication in Minerals after changes which I outline below.
- How was tested that the synthesis product was vaterite?
- Which database was used in PHREEQC?
- What voltage and current was used in SEM? What method was used for quantification?
Usually EDS only has a standardless ZAF correction for quantification which is not very accurate. Was any test performed for accuracy of the SEM-EDS measurements, e.g. measurement of standards?
- Quantification in EDS is not very reliable, especially if the surface of the sample is not flat (Figure 3 clearly shows that this is not the case). Table 3 clearly shows differences between Mg quantification by digestion and SEM-EDS measurements.
Also, how many EDS measurements were performed per sample? It is somewhat unclear if the EDS results were homogeneous between particles.
line 43/44:“Typically, Mg, Strontium (Sr), 43 and Manganese (Mn) are major impurities in natural calcites” please provide some references.
Line 78/79: Please give 1-2 examples of references for Mg coprecipitation with calcite studied at high supersaturation. Please explain why this is not relevant here.
Line 126/127: The concentration of Ca and Mg were measured by ICP-OES. – The concentration of Ca and Mg in what? In the supernatant or in the precipitates? Please clarify!
This assumes a homogeneous incorporation of the Mg into the calcite – Mg has been shown to influence calcite growth rates – possible layers? How did they test for homogeneity of the samples?
Was there any microscopy characterization of the clays? Did the Mg-carbonate precipitate separately from the clays or onto the clays? Same here - how was homogeneity of the samples assessed?
What is the supersaturation with respect to the solid solution? Described here: Pina, C.M., Enders, M. and Putnis, A., 2000. The composition of solid solutions crystallising from aqueous solutions: the influence of supersaturation and growth mechanisms. Chemical Geology, 168(3-4), pp.195-210.
Author Response
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Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
The authors have responded to the my main enquiries from the first round of revision and I believe that the article is suited for publication. All concerns that were not directly responded with new results (which I believed was important) was discussed in the new version with references' support.
Author Response
We thank the reviewer for his comments, and we are happy that our changes to the manuscript resolved his concerns.
Reviewer 3 Report
see attached
Comments for author File: Comments.pdf
Author Response
We want to thank the reviewer for his thoughtful comments. We agree with all the proposed corrections and made corresponding changes to the uploaded manuscript (see: manuscript_changes_highlighted.docx).
