HAL Id: hal-02742565
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Submitted on 3 Jun 2020
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Generic reactive transport codes as flexible tools to
integrate soil organic matter degradation models with
water, transport and geochemistry in soils
Diederik Jacques, Frédéric Gérard, Uli Mayer, Bertrand Leterme
To cite this version:
Diederik Jacques, Frédéric Gérard, Uli Mayer, Bertrand Leterme. Generic reactive transport codes as
flexible tools to integrate soil organic matter degradation models with water, transport and
geochem-istry in soils. EGU, European Geosciences Union General Assembly 2016, Apr 2016, Vienne, Austria.
�hal-02742565�
Geophysical Research Abstracts Vol. 18, EGU2016-14182, 2016 EGU General Assembly 2016
© Author(s) 2016. CC Attribution 3.0 License.
Generic reactive transport codes as flexible tools to integrate soil organic
matter degradation models with water, transport and geochemistry in soils
Diederik Jacques (1), Fréderic Gérard (2), Uli Mayer (3), Jirka Simunek (4), and Bertrand Leterme (1)
(1) SCK-CEN, Belgium (djacques@sckcen.be), (2) INRA, UMR Eco&Sols, Montpellier, France, (3) Earth, Ocean and Atmospheric Sciences, University of British Columbia, Vancouver, BC, Canada, (4) Department of Environmental Sciences, University of California Riverside, CA, USA
A large number of organic matter degradation, CO2transport and dissolved organic matter models have been
de-veloped during the last decades. However, organic matter degradation models are in many cases strictly hard-coded in terms of organic pools, degradation kinetics and dependency on environmental variables. The scientific input of the model user is typically limited to the adjustment of input parameters. In addition, the coupling with geochem-ical soil processes including aqueous speciation, pH-dependent sorption and colloid-facilitated transport are not incorporated in many of these models, strongly limiting the scope of their application. Furthermore, the most com-prehensive organic matter degradation models are combined with simplified representations of flow and transport processes in the soil system. We illustrate the capability of generic reactive transport codes to overcome these short-comings. The formulations of reactive transport codes include a physics-based continuum representation of flow and transport processes, while biogeochemical reactions can be described as equilibrium processes constrained by thermodynamic principles and/or kinetic reaction networks. The flexibility of these type of codes allows for straight-forward extension of reaction networks, permits the inclusion of new model components (e.g.: organic matter pools, rate equations, parameter dependency on environmental conditions) and in such a way facilitates an application-tailored implementation of organic matter degradation models and related processes. A numerical benchmark involving two reactive transport codes (HPx and MIN3P) demonstrates how the process-based simula-tion of transient variably saturated water flow (Richards equasimula-tion), solute transport (advecsimula-tion-dispersion equasimula-tion), heat transfer and diffusion in the gas phase can be combined with a flexible implementation of a soil organic matter degradation model. The benchmark includes the production of leachable organic matter and inorganic carbon in the aqueous and gaseous phases, as well as different decomposition functions with first-order, linear dependence or nonlinear dependence on a biomass pool. In addition, we show how processes such as local bioturbation (bio-diffusion) can be included implicitly through a Fickian formulation of transport of soil organic matter. Coupling soil organic matter models with generic and flexible reactive transport codes offers a valuable tool to enhance in-sights into coupled physico-chemical processes at different scales within the scope of C-biogeochemical cycles, possibly linked with other chemical elements such as plant nutrients and pollutants.