Can Isotopes Be Used as Lead Tracers in Shooting-Range Soils?

Round 1

Reviewer 1 Report

This paper reports Pb isotopic for 13 soils and 3 shotgun pellets from an abandoned shooting range in NW Spain; other results for the soils were previously published by Rodriguez-Seijo et al. (2016) and Reigosa-Alonso et al. (2021). 

Some more information about soil sampling (e.g. depths) would have been useful.

The Pb isotopic results are high precision (MC-ICP-MS) and it was encouraging to see that  the authors reported the 204Pb results, even though they did not make use of these data. (Minor point line 105: why report the ratios as 204/206 when they are given as 206/204 in the Tables?).

Line 147: It might be worth mentioning a source from 'home-made' ammunition (e.g. Changes in blood lead of a recreational shooter. Gulson, Palmer. Bryce STOTEN 2002). This paper reports high precision isotopic data which could be added to their Table 2; as could be data from Gulson et al. 2002, J Forensic Science 47, 1015-1021.

It would be worth mentioning (in the section on "Research implications..") possible complications in interpretation of soil contamination arising from Pb from primers (e.g. Pb styphenate)

Line110: ?shoots'

Line 181: Perhaps add: '...as in Table 2 reference [37].'

Author Response

Reviewer 1

This paper reports Pb isotopic for 13 soils and 3 shotgun pellets from an abandoned shooting range in NW Spain; other results for the soils were previously published by Rodriguez-Seijo et al. (2016) and Reigosa-Alonso et al. (2021).

Some more information about soil sampling (e.g. depths) would have been useful.

Dear reviewer #1,

First, we want to acknowledge your helpful comments and suggestions. Suggestions about home-made ammunition or primers were very useful for our work. Regarding this question, more information was indicated, although we can not give several details to avoid being very similar to previous works.

The Pb isotopic results are high precision (MC-ICP-MS) and it was encouraging to see that  the authors reported the ²⁰⁴Pb results, even though they did not make use of these data. (Minor point line 105: why report the ratios as ^204/206 when they are given as ^206/204 in the Tables?).

Dear reviewer #1,

Thank you for your comment. Yes, all isotope rates were measured. Initially, our objective was to try to use the isotope as tracers linked with other work, although after several issues (recycled ammunition, etc.), we forgot this idea. In any case, in this paper, we report all isotopes since they can be useful for other researchers for lead tracing, like in wildlife studies. One of our main issues was that only one or two isotope ratios were usually reported when MC-ICP-MS could determine more isotope ratios. Regarding the ²⁰⁶/²⁰⁴ we use this isotope ratio and not ²⁰⁴/²⁰⁶ since it was more used for other authors.

Line 147: It might be worth mentioning a source from 'home-made' ammunition (e.g. Changes in blood lead of a recreational shooter. Gulson, Palmer. Bryce STOTEN 2002). This paper reports high precision isotopic data which could be added to their Table 2; as could be data from Gulson et al. 2002, J Forensic Science 47, 1015-1021.

Thank you so much for the suggested references. Unfortunately, we can not access Gulson 2002 (J Forensic Science 47, 1015-1021). However, the explanation of home-made ammunition from Gulson (2002, Stoten) was very useful for our work. In any case, both references were added to our paper.

It would be worth mentioning (in the section on "Research implications..") possible complications in interpretation of soil contamination arising from Pb from primers (e.g. Pb styphenate)

Thank you so much for the suggestion. This section was improved after your suggestion and from Reviewer #2.

Line110: ?shoots'

Thank you!

Line 181: Perhaps add: '...as in Table 2 reference [37].'

Thank you!

Author Response File: Author Response.doc

Reviewer 2 Report

Please see the attached document

Comments for author File: Comments.docx

Author Response

Reviewer #2

Review on “Can isotopes be used as lead tracers in shooting ranges soils?” General: The manuscript is very well written and deserves publication in the journal “Applied Sciences” after minor corrections.

Dear reviewer #2, Thank you for your comments and suggestions.

Here are my suggestions:

Line 70: Please either use the symbol Pb, or the word “lead” in a way to b consistent throughout. In this line you use in the same sentence both.

Thank you. We updated this comment throughout the manuscript.

Figure 2: The data are crowded together, and the reader can’t distinguish among the different areas. Why don’t you expand on the crowded area? (Even showing in an additional graph).

Thank you. Please, see the new figure 2

 

Figure 2. a) Scatter plot for ²⁰⁸Pb/²⁰⁶Pb versus ^206Pb/²⁰⁷Pb of lead isotope ratios for different shot pellet and ammunition manufacturers and studied soils. “Not indicated” means that authors have not reported a probable origin of shot pellet manufacturer/brand. b) Detail of the crowded central region. Data compiled from [5, 16-19, 20-22, 26, 33-34, 39-44].

Lines 72-76 and others: In the experimental you should list only the experiments that are new in this work. If the data were obtained in another study of yours, you should indicate with just a reference. This is original research and should not be a repetition of your previous work as far as the obtained data are concerned.

Dear reviewer #2,

We understand your comment. However, after the suggestions of reviewer #1, we will maintain this information for readers to show here the information about soil sampling and soil contamination.

The introduction should include a few sentences in regard to the methods used for the reader (MC-ICP-MS and ICP-TOF-MS). E.g., why were these chosen over other options?

We didn’t add this information because this paper was submitted as a communication paper (short communication in other journals). However, a short section was added in the introduction section. Thank you for this suggestion.

What are the data for the recoveries?

Recovery information was written in lines 100-104 and also in the Supplementary data (Table S2).

The procedure was validated with a solution of 200 μg L⁻¹ of SRM 981, thus obtaining a recovery rate higher than 90 % and isotope ratios within those indicated by the certificate. During this study, data accuracy was checked using SRM 981 Pb isotope standard solution (n = 20) (Table S2). Precision for ²⁰⁴Pb/²⁰⁶Pb was around 0.14 %, and for ²⁰⁶Pb/²⁰⁷Pb and ²⁰⁸Pb/²⁰⁶Pb ratios, around 0.01 % based on two standard deviations (2σ).

Table S2. Pb stable isotope ratios in reference material SRM 981 (NIST).

Isotope ratio	SRM 981 (NIST)
	Certified value	Measured value (N=20)
204Pb/206Pb	0.059042 ± 0.000037	0.05882 ± 0.00230
207Pb/206Pb	0.91464 ± 0.00033	0.91147 ± 0.00003
208Pb/206Pb	2.1681 ± 0.008	2.16268 ± 0.00009

Line 98: Add space between number and signs.

Thanks

There is no a distinct conclusion. Please add one.

Thank you for your comment. After your comments and from Reviewer #1, this section was rewritten.

Author Response File: Author Response.docx