Dear authors,

many thanks for providing a detailed answer to the various reviewers comments and for sketching a pathway by which these can be addressed.

I continue to believe that your contribution is of great interest, and would therefore invite you to proceed with the production of a revised version. Please allow me, however, to stress some of the most important points that seem to emerge from the reviewers’ comments:

1) The methodology will need to be satisfactorily explained. In your answers, you proposed a new figure to facilitate comprehension and I believe that to be very valuable. It will be equally important, though, to provide the required additional information in the manuscript’s text.

2) The omission of some of the samples is obviously a key point. You suggest to provide a more in-depth explanation for why this was done, which is certainly necessary. If somehow possible, however, I would strongly encourage you to also conduct a sensitivity analysis addressing the omission of individual samples. The central question is “how would your interpretation change if this or that sample would have been included or excluded from the analysis?”. If such a sensitivity experiment is not possible, the manuscript’s text should clarify why this is the case.

3) For a large number of questions asked by the reviewers, your responses provide a good series of arguments in favour of your hypotheses or your way of proceeding. Similarly as for the above point “1)”, it will be important to have these arguments and explanations included in your revised manuscript text, rather than in the rebuttal letter alone. If you sense a danger for the manuscript becoming too long because of that, consider moving some of the additional discussion into the supplementary and to “call” the corresponding sections from the manuscript. As an example related to “RC1 231-2”, the manuscript could include a sentence saying “For further justification of the chosen quadratic function, please see Supplementary Section X”.

4) I agree with your appreciation that, although equally important, the rearrangements requested in terms of manuscript structure will be easier to address.

In light of the substantial amendments requested by the reviewers, it will be necessary to have your revisions re-assessed by them. I plan to ask the revisions to be seen by the same set of reviewers, unless you have strong reasons to question their independence or competence.

I’m looking forward to your revised submission.

Best regards
Daniel Farinotti

Dear authors,

your manuscript has now be re-seen by two referees. They are both very positive about the improvements that you were able to perform, and commend on the thorough way by which their previous comments have been taken into account.

The two reviewer both recommend the article being accepted after a further round of minor revisions. The new set of comments mostly request a clearer distinction between ascertained facts and interpretations, which seems a fair and important point. Some further comments are related to individual assumptions, or address the interpretations as such. In all cases I felt that the comments are justified, clear and constructive, so that they definitively merit to be addressed. I am convinced that this will further improve your manuscript.

For the time being, however, I just wish you a healthy, restful, and merry Christmas.
Best wishes
Daniel Farinotti

Dear authors,

many thanks for taking on board the last set of comments that were left by the referees.

As far as I’m concerned, the comments have all been adequately handled: The requested comparison of your Cs- and Pb-concentrations to other values in the literature, for example, looks well placed and has improved the interpretability of your results. Similarly, I felt that the parts of your results that are based on interpretation rather than on hard evidence are more clearly highlighted, most notably in the abstract but also in the Results and Discussion sections. The information added in terms of new tables or revised figures has additionally helped in clarifying some of the more important remaining questions, and finally, the various technical requests seem to have all been accommodated or replied to as well.

Based on the above assessment, I am delighted to say that your manuscript can now be accepted for publication. I gladly take the chance to be the first to congratulate you for the great efforts that you have performed, and for succeeding with this very interesting piece of research.

Best wishes
Daniel Farinotti