HR: 0801h
AN: NS11B-0495    [Abstracts]
TI: NMR Studies of Biodegradation Reactions in Porous Media
AU: * Mitreiter, I
EM: ivonne.mitreiter@ufz.de
AF: UFZ – Helmholtz Centre for Environmental Research, Department of Hydrogeology, Permoserstrasse 15, Leipzig, 04318, Germany
AU: Oswald, S E
EM: sascha.oswald@ufz.de
AF: UFZ – Helmholtz Centre for Environmental Research, Department of Hydrogeology, Permoserstrasse 15, Leipzig, 04318, Germany
AU: Stallmach, F
EM: stallmac@physik.uni-leipzig.de
AF: University of Leipzig, Department of Interface Physics, Linnestrasse 5, Leipzig, 04103, Germany
AB: Subsurface contamination caused by organic compounds is a widespread environmental problem. Biodegradation is the main process to reduce the mass of organic contaminants in soils and groundwater. Often the biodegradation is limited by the supply of electron acceptors at the location of the contaminants, and mixing and diffusion are therefore coupled to the degradation process. Nuclear magnetic resonance (NMR) allows non- invasive and non-destructive insight into diffusion processes and effects of microbial biomass on the pore scale, where the mixing and degradation processes actually are taking place. Studying key processes non-invasively with high temporal resolution will contribute to a better understanding of the effective biodegradation rates of organic contaminants in saturated porous systems. The application of ¹H NMR relaxometry and PFG NMR diffusometry provide the possibilities to study diffusive transport at the mixing zones in porous media, where contaminants and electron acceptors show strong concentration gradients due to degradation reactions. Nuclear spin relaxation times of water reflect its interaction with the porous media as well as the biomass. To localize microbial biomass the mobility of the water molecules (relaxation times) can be classified corresponding to bound water in the biomass and bulk water. Oxygen is the most important electron acceptor that stimulate the activity and growth of aerobic microbes, and iron(III) a major one for anaerobes. In our work we applied low field (0.2 T) and high field (3 T) NMR measurements to analyze the diffusion in water and biomass and to monitor the concentration changes of electron acceptors. The experimental setup consists of small columns containing saturated porous media applying inversion recovery (IR) and pulsed field gradient (PFG) sequences. We show that both, oxygen as well as iron(III) affect the relaxation times by their paramagnetic properties, and can be determined by NMR relaxometry in environmentally relevant concentrations. So relaxation time measurements in presence of either oxygen or iron(III) can be used to detect consumption of these electron acceptors and thereby redox reactions and degradation rates.
DE: 0418 Bioremediation
DE: 0452 Instruments and techniques
DE: 0461 Metals
DE: 1835 Hydrogeophysics
DE: 3929 NMR, Mossbauer spectroscopy, and other magnetic techniques
SC: Near-Surface Geophysics [NS]
MN: 2007 Fall Meeting