Visualization and quantification of processes at biogeochemical interfaces with magnetic resonance imaging

Principle investigators: PD. Dr. T. Baumann, Prof. Dr. R. Niessner

Co-worker: Dr. M. Seidel

Objectives

• Development of markers to access the spatial distribution of selected organic chemicals in soil
• Visualization of biogeochemical interfaces in soil
• Development of a technique to characterize the activity of biogeochemical interfaces in the spatial and temporal domain


Hypotheses

The fate of organic pollutants in soil is controlled by spatial features of the biogeochemical interfaces which may vary in the time domain. Most reactions at interfaces in soil are diffusion limited, that is, mass transfer rates to and from the interface are controlled by diffusion. Preferential flow might lead to a development of active interfaces along the flow path. During the development of active interfaces, flow paths might alter because of topological changes of the pore space caused by the development of interfaces and new preferential flow paths might evolve.

Foto


Scientific Approach

Biogeochemical interfaces control the fate of organic and inorganic substances in the subsurface. For a better understanding of the processes at these interfaces it is necessary to explore the spatial and temporal dynamics of the interfaces themselves and the processes associated with them.

Magnetic resonance imaging (MRI) is a good choice to visualize and quantify dynamic processes in porous systems. This research project aims at the development of techniques to visualize and quantify the interfaces in soil and the fate of phenanthrene and hexadecane in selected soils. The method will be based on MRI making heavy use of spectroscopic features of the MRI signal. Redox changes will be looked at using the paramagnetic effect of oxygen, and the different relaxation times of hexadecane and water will be used to visualize the two fluids. Using spin-labelled antibodies and humic acids, the accumulation and possible degradation of the contaminants at the interfaces will be measured.

Experiments on the pore scale in simplified pore network provide access to the interface dynamics. The high spatial and temporal resolution of the data obtained in this project provides the background for the interpretation of experiments at the column and the batch scale.

Cooperations within the priority programme

Prof. Dr. J. Bachmann (surface modifications), Prof. M.H. Gerzabek (upscaling), Dr. S. Oswald (upscaling, modelling), PD Dr. H.-J. Vogel (upscaling, visualization)

Publications
Baumann, T., Toops, L., Niessner, R. 2010. Colloid dispersion on the pore scale. Water Res. 44, 1246-1254.

Werth, C.J., Zhang, C., Brusseau, M.L., Oostrom, M., Baumann, T. 2010. A review of non-invasive imaging methods and applications in contaminant hydrogeology research. J. Contam Hydrol. 113, 1-24.