On the Influence and Correction of Water Content on pXRF Analysis of Lateritic Nickel Ore Deposits in the Context of Open Pit Mines of New-Caledonia

Round 1

Reviewer 1 Report

1.The title of this article mentions "influence and correction of water content", but the article only discusses the situation under saturated water content. How about the changes of other different water content?

2. How to define soil water saturation? epi-saturation or endo-saturation?field water holding capacity or maximum water holding capacity?

3. L67-72: As mentioned by authors, water, particle size, and sampling are three important points, but the current study focused more on the water content in the quantification of chemical elements. However, in section 2.3.2 the authors proposed tow different sampling process (Figure 5), but there are no explains or descriptions about the results of different sampling  process. Please clearly explain.

4. L228: Please explain "Sample saturation with water (water in excess was removed thanks to a pump)"? How many water added? the suction power of the pump?the suction time?how to make sure the soil in the cup has fully saturated with water?Saturation method is very important in the manuscript, the authors should tell it clearly with a scientific description.

5. L257-259:How to judge that the soil is saturated with water? How many times should it be sprayed to judge that the soil is saturated with water? The author should clearly define and explain.

6.L311-312: Please explain how multiple linear regression (Equation 4) is produced?

7.On the whole, the article contains too many figures and tables, which confuses readers, and the cumbersome experiment design and discussion confuses readers.

8.If the impact of soil moisture content is within an acceptable error range, whether the soil is saturated with water may not cause a big error. Therefore, a large part of this article seems to be comparing the pros and cons of the three research devices. 

Author Response

Thank you to the reviewers for their constructive remarks, which contribute to greatly improve our manuscript.

The manuscript has been reviewed carefully to remove inconsistencies and was modified to highlight the scientific challenges in the field of the influence of water content on pXRF analysis of lateritic nickel ore deposits in the context of open pit mines.

Please see in attached file the answers of the remarks, and find attached the revised manuscript with the corrections for the other remarks.

Author Response File: Author Response.pdf

Reviewer 2 Report

The authors present a new suggestion about correction parameters for elements quantitation by portable XRF devices on site in the miles. More specifically, the water content influence was studied, while water saturation method was used for correction. Three portable XRF devices were also compared. The authors documented their method and experiments very well and clearly presented. The proposed method seems to give accurate results after the correction equations used. However, the authors should also provide some data about the precision of the method.

Finally, the text contains few grammar and syntax errors.

Author Response

Thank you to the reviewers for their constructive remarks, which contribute to greatly improve our manuscript.

The manuscript has been reviewed carefully to remove inconsistencies and was modified to highlight the scientific challenges in the field of the influence of water content on pXRF analysis of lateritic nickel ore deposits in the context of open pit mines.

Please see in attached file the answers of the remarks, and find attached the revised manuscript with the corrections for the other remarks.

Author Response File: Author Response.pdf

Reviewer 3 Report

The paper deals with the use of pXRF devices under humid, tropical conditions in mining operations and mineral exploration, focused on the classical Nickel laterite deposits of New Caledonia (SW Pacific). While the application of pXRF devices rests primarily as largely used, fast and economic method of geochemical assessment of rock materials, pXRF data obviously still require to be compared with conventional and more accurate laboratory XRF analyses. One main problem emerging from method application in humid areas is that of high water contents in rock, which cause significant problems in the correct acquisition of the signal intensity and background control. In the study, the Authors verify the influence of water contents on quite large sets of samples collected in two stages in Ni-mineralized (garnierite) laterite and saprolite layers of a New Caledonia open pit mine area, tested under natural and water-saturated conditions using three different pXRF devices, both in field and in laboratory. Ni and Fe analyses, critical for mine operations in the studied area, were performed for the sample sets and underwent to a statistical treatment. The results and their statistical study allowed the Authors to find a correction method to compensate humidity effect for the used devices; corrections could be confidently extended to other pXRF instruments, and the method sets the stage for further, future calibrations. I found the paper well structured and well written, the methods adequate and the results properly discussed. English is good, I found only a short sentence that I suggest to rephrase and some minor errors and typos in the text (see the attached pdf file).

Comments for author File: Comments.pdf

Author Response

Thank you to the reviewers for their constructive remarks, which contribute to greatly improve our manuscript.

The manuscript has been reviewed carefully to remove inconsistencies and was modified to highlight the scientific challenges in the field of the influence of water content on pXRF analysis of lateritic nickel ore deposits in the context of open pit mines.

Please see in attached file the answers of the remarks, and find attached the revised manuscript with the corrections for the other remarks.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

1.The author has no positive response to all my comments, and I cannot accept such an answer and justification.

2.L 85-87:"Whatever the element considered, it is generally accepted that moisture contents up to 20% don’t significantly influence XRF intensity and the quantification by this method [19, 20, 21]." If it is generally accepted that moisture levels up to 20% do not significantly affect the XRF intensity and quantification of the method, should an upper limit be explored?

3.What is the real objective of this research?

4.If water content is an important factor, is it too simplistic to only discuss "saturated moisture state" in this article? 

5.L611-615:"The pXRF measurements are carried out on wet samples, XRF intensities will therefore be lower, which will reduce the accuracy of the measurement and increase minimum detectable concentration. Application to a larger number of samples is now necessary to estimate more precisely precision and accuracy of this method." This paragraph is similar to the description of L73-84, that is, the results of this study do not have new and progressive findings, and analysis of a large number of more samples is still required. From the reader's point of view, this lengthy article does not provide a clear Scientific information and research innovations.

Author Response

Dear Reviewer, Thank you for all your constructive suggestions that help us to improve our reflection. Our work is still ongoing and a number of fundamental questions are still pending. In the literature, water influence on pXRF measurements has received little attention (probably because the most evident way of doing is to dry the sample) and the most used law (based on Beer Lambert law) do not perform very well on our samples (and this is also the case in others published works). Although we have not yet found the underlying mechanisms or the missing parameters, we believe that beyond the practical method we propose in the field, our work will be usefull for the community who is interested by water content and XRF.

See the attachment for the answers.

Author Response File: Author Response.pdf

Round 3

Reviewer 1 Report

Dear authors:

The descriptions of Author' Response are much more than the correction in the text.

Please reply to comments instead of expressing your own comments. 

Author Response

Dear reviewer,

All our apologies for our last response and in particular to your Q5 question. This was the response of one of us for the others, and it should not have been transmit.

Q2 and Q4: we have added two paragraphs at the end of the conclusion.

Q3: some elements are already in the text, see lines 604-313 for point 1 and lines 630-638 for point 2.

Sincerely,

The authors

Author Response File: Author Response.pdf