Role of biocolloids for the formation, dynamics and maturing of biogeochemical interfaces
Principle investigators: Prof. Dr. K.U. Totsche, Prof. Dr. E. Kothe, Prof. Dr. K.D. Jandt
Co-workers: D. Link, F. Macht
Relocation of organic matter (OM) in soil including biocolloids such as fungi and bacteria is a decisive process for the formation and depth propagation of biogeochemical interfaces. We assume that during the transport in soil mobile OM (I) accumulates under no-flow conditions, (II) is mobilised upon onset of flow and is (III) preferentially retarded at materials with high surface area and porosity (clay minerals, charcoal, Fe oxides). We study the initial formation of biogeochemical interfaces in soil and their dynamics with water-unsaturated column experiments packed with a biologically active source layer and a reception layer. By using artificial soil materials composed of mixtures of quartz, clay minerals, Fe oxides and charcoal, the transport of OM and the initial interface formation will be studied "from scratch" and compared with experiments with natural soils (Cambisols, Luvisols) that represent matured interfaces. The soil-column effluent will be analysed for organic and inorganic solutes, (bio)colloids and bulk solution properties. We study the retardation of organic and inorganic tracers at different stages of the experiments to determine the effects of relocation and inhabitation on interface structure and properties. We also investigate the transport of an organic contaminant (phenanthrene) and its metabolisation by using the 13C-labelled compound. The materials (soils and components of the artificial soils) are studied before and after the experiments. Atomic-force microscopy is used to measure topography, surface-charge heterogeneity and force volume to explore the effects of interface maturing on surface properties. X-ray photoelectron spectroscopy is applied to obtain chemical information on the elements and their electronic state of the individual soil components and to identify biomolecules such as DNA or proteins.
These findings, in combination with results of other groups, will help to unravel the role of biocolloids for the formation and maturing of biogeochemical interfaces and the transport of organic chemicals in soil.
Cooperations within the priority programme:
Prof. Dr. M.H. Gerzabek, Prof. Dr. M. Kästner, Prof. Dr. I. Kögel-Knabner, Prof. Dr. K. Smalla, Prof. Dr. Dr. h.c. M. Spiteller, PD Dr. H.-J. Vogel
Macht, F., Eusterhues, K., Pronk, G.J., Totsche, K.U. 2011. Specific surface area of clay minerals: Comparison between atomic force microscopy measurements and bulk-gas (N2) and -liquid (EGME) adsorption methods. Appl. Clay Sci. 53, 20-26.
Tunega, D., Gerzabek, M.H., Haberhauer, G., Totsche, K.U., Lischka, H. 2009. Model study on sorption of polycyclic aromatic hydrocarbons on goethite. J. Colloid Interface Sci. 330, 244-249.