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SOIL An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/soil-2017-20
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Original research article
14 Jul 2017
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal SOIL (SOIL).
Saturated and unsaturated salt transport in peat from a constructed fen
Reuven B. Simhayov1, Tobias K. D. Weber1,2, and Jonathan S. Price1 1Department of Geography, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada
2Soil Science and Soil Physics Division, Institute of Geoecology, TU Braunschweig, Langer Kamp 19c, 38106 Braunschweig, Germany
Abstract. To determine the underlying processes of solute transport in peat an experimental constructed fen peatland, soil hydraulic properties were measured and saturated and unsaturated solute breakthrough experiments were performed using Na+ and Cl as reactive and non-reactive solutes, respectively. We tested the performanceof three solute transport models, including the classical equilibrium Convection-Dispersion Equation (CDE), a chemical non equilibrium one-site adsorption model (OSA) and a model to account for physical non-equilibrium, the mobile-immobile phases (MIM). The selection was motivated by the fact that the applicability of the MIM in peat soils finds a wide consensus. However, results from inverse modelling and a robust statistical evaluation of this peat provide evidence that the measured breakthrough of the conservative tracer, Cl could be simulated well using the CDE. This is demonstrated by a very high Damköhler number (→infinity) suggesting instantaneous equilibration between the mobile and immobile phases; this underscores the redundancy of the MIM approach for this particular peat. Scanning electron microscope images of the peat show the typical multi-pore size distributions structure have been homogenised sufficiently by decomposition, such that physical non-equilibrium solute transport no longer governs the transport process. This is corroborated by the fact the soil hydraulic properties were adequately described using a unimodal van Genuchten-Mualem model between saturation and a pressure head of ~ −1000 cm of water. Hence, MIM is not the most suitable choice, and the long tailing of the Na+ breakthrough curve is caused by chemical non-equilibrium. Successful description was possible using the OSA model. To test our results for the unsaturated case, we conducted an unsaturated steady state evaporation experiment to drive Na+ and Cl transport. Using the parameterised transport models from the saturated experiments, we could numerically simulate the unsaturated transport using Hydrus-1D. The simulation showed a good prediction of observed values, confirming the suitability of the parameters for use in a slightly unsaturated transport simulation. The findings improve the understanding of solute redistribution in the constructed fen.

Citation: Simhayov, R. B., Weber, T. K. D., and Price, J. S.: Saturated and unsaturated salt transport in peat from a constructed fen, SOIL Discuss., https://doi.org/10.5194/soil-2017-20, in review, 2017.
Reuven B. Simhayov et al.
Reuven B. Simhayov et al.
Reuven B. Simhayov et al.

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