Prof. Peter Knabner1, Dr. Nadja Ray1, M.Sc. Andreas Rupp1, Dr. Alexander Prechtel1, Prof. Kai Totsche2, Prof. Ingrid Kögel-Knabner3
1University Erlangen-Nürnberg Department Mathematics, D 91058 Erlangen, Germany, 2University Jena Institute for Geosciences Geohydrology, D07749 Jena, Germany, 3Technical University Munich Chair of Soil Science, D85354 Freising, Germany
Microaggregates are the fundamental building blocks of soils and thus important for their structure, properties, and functions. Mathematically based modeling can facilitate the understanding of self-organization, formation, build-up, composition, properties, and stability of microaggregates provided that the complex coupling of biological, chemical and physical processes is taken into account.
Our model is based on a cellular automaton method (CAM) for the pore scale evolution of the solid , biomass and liquid (water, air) phases, all transport and reaction processes are described continuum mechanics based. In the CAM framework, prototypic solid building units quartz (spherical), goethite (needle-like), and illite (platy) are implemented to investigate the formation and self-organization of soil microaggregates. Interaction of these building units by means of stabilizing sticky agents (EPS) in combination with electrostatic attraction/repulsion lead to composite building units and eventually to soil microaggregates. Modern numerical techniques (DG methods) allow for the simulation of the full model The operational, comprehensive model allows rating the influencing factors for the formation of soil microaggregates and also investigating optimal aggregation conditions. Moreover, our modeling approach enables revealing the effect soil organic matter has as nucleus for the aggregation process.
Finally, soil’s characteristic properties such as porosity, effective diffusion tensors and permeabilities for the resulting complex geometries are deduced rigorously on the basis of such a detailed structure evolution and allow for Darcy scale simulations of flow and reactive transport taking into account the pore scale evolution at the level of detail described above. In this way it is possible to assess the impact of microaggregate formation on soil functions.