SOM-AGING: Physicochemical aging mechanisms in soil organic matter
Principal investigators: Prof. Dr. Gabriele E. Schaumann, Dr. Marko Bertmer
Co-worker: Jette Schwarz, Alex Jäger
One of the most valuable ecological potentials of soil organic matter (SOM) is based on its highly dynamic nature enabling flexible reactions on a variety of environmental conditions. SOM controls large part of the processes occurring at biogeochemical interfaces in soil and may contribute to sequestration of organic chemicals. This project focuses on understanding of these dynamics in SOM from a new viewpoint regarding SOM as amorphous matrix. The dynamics addressed in this view are mainly based on "weak" intermolecular interactions rather than covalent binding.
Based on results of our recent studies, our central hypothesis is that physicochemical SOM matrix aging, driven by dynamics in intermolecular cross-linking via bridges of water molecules and multivalent cations, is responsible for sequestration of organic chemicals. We will therefore assess mobility of SOM structural elements and sorbed probe compounds via sophisticated solid state NMR techniques from macromolecular chemistry and combine these with Differential Scanning Calorimetry, 1H NMR Relaxometry and a modified inverse gas chromatography. This set of methods will link SOM matrix rigidity and swelling properties with the presence sequestered probe compounds. Via controlled heating/cooling cycles, drying/remoistening cycles and targeted modification of SOM by biofilm enrichment and coordinative cross-linking, we will establish the relation between SOM sequestration potential, SOM structural characteristics and environmental conditions leading to immobilization or unexpected release of contaminants in the field.
Cooperation within the priority programme:
Prof. Dr. M.H. Gerzabek, Prof. Dr. B. Marschner, Prof. Dr. J. Bachmann, Prof. Dr. I. Kögel-Knabner
Aquino, A.J.A., Tunega, D., Schaumann, G.E., Haberhauer, G., Gerzabek, M.H., HLischka, H. 2011. The functionality of cation bridges for binding polar groups in soil aggregates. Int. J. Quant. Chem. 111, 1531-1542.
Jäger, A., Schaumann, G.E., MBertmer, M. 2011. Optimized NMR spectroscopic strategy to characterize water dynamics in soil samples. Org. Geochem. 42, 917-925.
Jaeger, F., Shchegolikhina, A., van As, H., Schaumann, G.E. 2010. Proton NMR relaxometry as a useful tool to evaluate swelling processes in peat soils. The Open Magnetic Resonance Journal 3, 27-45.
Schaumann, G.E., Bertmer, M. 2008. Do water molecules bridge soil organic matter molecule segments? Eur. J. Soil Sci. 59, 423-429.