EGU2020-15848
https://doi.org/10.5194/egusphere-egu2020-15848
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Complex soil mass redistribution along a catena using meteoric and in-situ 10Be as tracers

Francesca Calitri1,2, Markus Egli1, Michael Sommer2,3, Dmitry Tikhomirov1, and Marcus Christl4
Francesca Calitri et al.
  • 1University of Zurich, Department of Geography, Zurich, Switzerland (francesca.calitri@geo.uzh.ch)
  • 2Leibniz-Centre for Agricultural Landscape Research (ZALF), Müncheberg, Germany
  • 3Institute of Earth and Environmental Sciences, University of Potsdam, Potsdam, Germany
  • 4Laboratory of Ion Beam Physics, ETH-Zürich, Zurich, Switzerland

In hilly and mountainous landscapes, the bedrock is actively converted to a continuous soil mantle. The bedrock-soil interface lowers spatially at the soil production rate, and the soil acts as a layer removing sediment produced locally and transported from upslope. Forested soils of a hummocky ground moraine landscape in Northern Germany exhibit strongly varying soil thicknesses with very shallow soils on crest positions and buried soils at the footslope. We explored the explanatory power of both 10Be forms (in situ and meteoric) for forest soils on a hillslope to shed light into the complex mass redistribution. Our main research questions were: how do meteoric and in-situ 10Be compare to each other? What do they really indicate in terms of soil processes (erosion, sedimentation, reworking)? By using both types of 10Be, the dynamics of soils and related mass transports should be better traceable. Both 10Be forms were measured along three profiles at different slope positions: Hydro1 (summit), Hydro3 (shoulder), Hydro4 (backslope). Furthermore, a buried horizon was found in the profile Hydro4 at 160 cm depth and 14C-dated. The distribution pattern of meteoric 10Be of Hydro4 shows an inverse exponential depth profile, and an almost uniform content of in-situ 10Be along the profile. Meteoric 10Be indicates on the one hand that a new soil was put on top of an older, now buried soil. On the other hand, meteoric 10Be is involved in pedogenetic processes and clearly exhibits clay eluviation in the topsoil and clay illuviation in the subsoil. The uniform content of the in situ 10Be shows soil mixing that must have occurred during erosion and sedimentation. The14C dated buried soil horizon indicates a deposition of eroded soil material about 7 ka BP. Consequently, an increase in the in-situ 10Be content towards the surface should be expect which however was not the case. The reason for this is so far unknown. Radiocarbon dating and 10Be data demonstrate that strong events of soil mass redistribution in Melzower Forest are mainly a result of ancient natural events. Further measurements of fallout radionuclides (239+240Pu) showed no erosion for the last few decades in the same catchment.

How to cite: Calitri, F., Egli, M., Sommer, M., Tikhomirov, D., and Christl, M.: Complex soil mass redistribution along a catena using meteoric and in-situ 10Be as tracers, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-15848, https://doi.org/10.5194/egusphere-egu2020-15848, 2020

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Display material version 1 – uploaded on 04 May 2020
  • CC1: Comment on EGU2020-15848, Kai Deng, 05 May 2020

    Dear Francesca Calitri,

    Thanks for presenting such a nice dataset combining meteoric and in situ 10Be. I just have two small questions:

    1) In Page 8, why does the meteoric 10Be concentration decrease with soil pH (at 5.5-8)? In general, I think higher pH means higher retentivity and perhaps higher 10Be concentrations? One explanation on this negative correlation  is that high pH commonly dominates the lower part of each soil profile, and meteoric 10Be also shows lower values at a deeper depth? (i.e. both parameters are related to profile depth). Is that true regarding your dataset?

    2) In Page 8, R2 for correlation between in-situ 10Be and pH is quite high (0.60) (much higher than other parameters with in-situ 10Be). But I don't know what kind of process can explain such a correlation. Perhaps both parameters (in-situ 10Be and pH) vary with profile depth in a similar way?

    Looking forward to your reply.

     

    Best regards,

    Kai

    • AC1: Reply to CC1, Francesca Calitri, 05 May 2020

      Dear Kai,

      Thank you very much for your comment.

      1) One explanation is exactly the one you gave. 10Be concentrations are related to depth. So, high pH is found at lower depths where 10Be concentrations are lower and viceversa. But also, the meteoric 10Be is primarily in the oxyhydroxyde fraction and this allows more transport to depth (in some types of soil). And we found a positive correlation with the oxalate-extractable Fe (weakly or non-crystalline forms; Feox), the dithionite-extractable Fe (Fedith) and dithionite-extractable Mndith.

      2) Yes, for in situ 10Be I would say that the correlation is quite high due to the same depth profile variability of pH and in situ 10Be. 

      I hope I answered your questions!

      Best regards,

      Francesca

      • CC2: Reply to AC1, Kai Deng, 08 May 2020

        Dear Francesca,

         

        Got it! Thanks a lot for your detailed reply!

         

        Have a nice post-EGU weekend!

        Kai