Interlaboratory Comparison of ²²⁶Ra and ²²⁸Ra Activity Concentrations in Groundwater and Surface Water

Round 1

Reviewer 1 Report

Note:

1. Line 156. There must be a space after the subsection number. 3.2. Summary of ²²⁶Ra Results

2. Line 175. There must be a space after the subsection number. 3.3. Summary of ²²⁸Ra Results

3. Line 218. There must be a space after the subsection number. 3.4. Detailed Comparison of Total vs. Dissolved Ra

4. Line 298. Wrong section number. 5. Conclusions and Recommendations

I recommend carefully proofreading the text of the paper in order to eliminate technical errors.

Questions and recommendations for your consideration:

1. Is there any information obtained for the same samples on the assessment of the activity of ²²⁶Ra, ²²⁸Ra in groundwater and in the waters of reservoirs by various methods and laboratories at various points in time. If yes, then you can specify the corresponding values of the correlation coefficients.

2. Figures 3-7 show the results of comparison of measurements for different laboratories. The figures graphically marked the average values and standard deviations. In the scientific literature, the Student's t-test for a given degree of reliability is most often used to assess the closeness of means. The Student's coefficient makes it possible to judge the reproducibility of measurements. This is true if the measurements are correct. It may be possible to give the values of Student's coefficients for the probability of closeness of means, for example, 95%.

3. To verify the correctness of measurements, calibration measurements are used, that is, measurements on standard samples, in this case, standard samples of ²²⁶Ra, ²²⁸Ra activity in water. Carrying out such measurements in different laboratories by different methods on the same standard samples would greatly facilitate the interpretation and acceptance of the corresponding hypotheses about the discrepancy between the measurement results.

Author Response

Response to Reviewer No. 1:

Thank you very much for your comments:

Comments and Suggestions:

1. I would be happy to make the correction, however, there is already a space after the Section 3.2 heading (it is a 3-point space, with 12-point before, following the text, the same as used for the preceding sub-section 3.1).  The space is more obvious when looking at the line numbers. This spacing convention is unchanged from the publication template provided by Applied Sciences.
2. There is already a space after the Section 3.3 heading (it is a 3-point space, with 12-point before, following the text, the same as used for the preceding sub-section 3.1). The space is more obvious when looking at the line numbers. This spacing convention is unchanged from the publication template provided by Applied Sciences.
3. There is already a space after the Section 3.4 heading (it is a 3-point space, with 12-point before, following the text, the same as used for the preceding sub-section 3.1). The space is more obvious when looking at the line numbers. This spacing convention is unchanged from the publication template provided by Applied Sciences.
4. The section number for Conclusions and Recommendations has been corrected. Thank you.

The paper has been reviewed once more to eliminate technical errors but no additional errors were identified. Thank you.

Response to Questions and Recommendations:

1. That type of correlation would be interesting, however, the comparison between labs was only conducted once. There are no additional information for the same samples by various methods and labs at various points in time.
2. The data in Figure 7 represent the sum of the measured Ra-226 plus Ra-228 values (from Table 3), and the error bar is the degree of analytical precision reported by the laboratory. The presentation of data on figures is also discussed in Section 3.1. This figure does not mark the average values and their standard deviations as indicated by the reviewer.
3. It is agreed that use of a known standard would have allowed us to evaluate individual laboratory accuracy of the Ra measurements. However, this was not possible because our company does not possess a Radioactive Materials License to possess and use Ra-226 or Ra-228. Additional complications would be the safety issues associated with traveling to the Site and handling a more concentrated Ra standard, and performing dilutions in the field (the Ra analyses require large volumes of approximately 5 pCi/L activity). 

Reviewer 2 Report

Dear Author, I read you work with high interest.

Suggestions:

- to elaborate a map with the water sampling points.

- increase the bibliography.

- clatify results about J+ and Blank, for the no-laboratory expert

Best Regards

Author Response

To Reviewer No, 2- Thank you very much for the review and comments. Here are my responses.

1. It is agreed that a map of the sampling locations would be of general interest, but a map was not included for several reasons: (a) the number of locations was limited (three groundwaters and one surface water) and the focus of the study was comparison of lab results, not geochemistry of Ra at the site. Therefore, specific sample locations are not relevant to the objectives of the study. (b) the owner of the Site has requested that the Site not be identified in this publication.
2. The appropriate citations have been provided in the bibliography to support statements in the text as needed. I would be happy to add additional references to the bibliography, if the reviewer could please be more specific regarding which statements in the text should be supported by additional bibliographic information. I did add one additional reference on chemistry of Ra in the environment (the new reference "[3]" in the revised manuscript).
3. I slightly modified the sentence (lines 142 and 143) but not sure how to clarify this any further. Essentially, having Ra in the blank causes the sample result to be an estimate and with a high bias. The corresponding data qualifier is a J+, as explained in the text (Lines 141 - 143) and as also provided as a footnote to Table 3.

Reviewer 3 Report

The current work entitled “Interlaboratory Comparison of 226Ra and 228Ra Activity Concentrations in Groundwater and Surface Water " reported by David. This work is interesting and of significance impact in this field. The manuscript is well-written and well-presented. But, It is suggested to author to include more references in the manuscript. After this, the manuscript can be accepted in Applied sciences.

Author Response

Response to Reviewer No. 3 - Thank you very much for your comments. I realize the bibliography does not contain many references, however the statements in the text are supported by the applicable references where needed. I would be happy to provide more references to support the information in the text, if you could please be more specific as to where additional references are needed. I did, however, add one additional reference related to the chemistry of Ra (the new citation "[3]" in the revised manuscript.