# Interactive comment on "Understanding the role of water and tillage erosion from <sup>239+240</sup>Pu tracer measurements using inverse modelling" by Florian Wilken et al

O. Evrard

► To cite this version:

O. Evrard. Interactive comment on "Understanding the role of water and tillage erosion from <sup>239+240</sup>Pu tracer measurements using inverse modelling" by Florian Wilken et al. [0] EGU SOIL journal. 2020. cea-02569251

HAL Id: cea-02569251

https://cea.hal.science/cea-02569251

Submitted on 11 May 2020

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Distributed under a Creative Commons Attribution 4.0 International License
**Interactive comment on** "Understanding the role
of water and tillage erosion from <sup>239+240</sup>Pu tracer
measurements using inverse modelling" by
Florian Wilken et al.

Olivier Evrard (Referee)

olivier.evrard@lsce.ipsl.fr

Received and published: 8 May 2020

General comments This study quantifies soil redistribution due to both water and tillage erosion processes in a 4.2-ha catchment (corresponding to one single field) located in an intensively cultivated region of Northeastern Germany. To reach this goal, Pu-239+240 inventory measurements have been conducted (and interpolated) and an inverse modelling approach (based on the SPEROS-Pu conceptual model) has been undertaken. Overall, the study was well designed (through a nice nested sampling approach with five densified sub-grids). In total, soil cores were collected at 219 locations (including 10 detailed depth profiles sampled at different topographic locations
across the study site) and analysed for Pu-239 and Pu-240 by ICP-MS, which repre-
sents considerable field and lab work efforts! The authors should be congratulated for
that!

At some places, the text is unclear and could be improved, the use of several terms
and technical formulations is sometimes misleading, but this will likely be fixed easily
by the authors when revising the text (see the annotated pdf file).

In the discussion and in the conclusions, I have the feeling that, at some places, the
authors go maybe a bit too far when extrapolating their results, and they should be
more nuanced in the text. Importantly, the advantages of using Pu-239+240 inven-
tories (compared to Cs-137 inventories) for reconstructing soil redistribution between
1964-2016 should be better justified in the text, in my opinion. Of note, analysing Pu-
239 and Pu-240 requires time-consuming chemical sample preparation steps that are
not required for analysing Cs-137 ('simple' physical measurement). A reason for us-
ing Pu isotopes could be that the study area received significant Chernobyl fallout in
1986 (in addition to the global fallout with a peak in 1963-64), which would complicate
the temporal reconstruction. However, this is not specifically addressed by the authors
(nor supported by their measurement of both Pu-239 and Pu-240, the ratio of which
should directly provide the answer?) Of course, there could also be other (good) rea-
sons to use Pu isotopes instead of Cs-137, but their clarification in the text would be
appreciated.

For detailed comments, questions and suggestions all throughout the text, please refer
to the enclosed annotated pdf file.

Please also note the supplement to this comment:
https://www.soil-discuss.net/soil-2020-22/soil-2020-22-RC2-supplement.pdf

Interactive comment on SOIL Discuss., https://doi.org/10.5194/soil-2020-22, 2020.