Soil processes at the nano scale

Prof. Dr. Ingrid Kögel-Knabner

Particles with submicron grain sizes are substantial constituents of the inorganic soil matrix. Of particular importance are Fe oxides (goethite, ferrihydrite), short range order Al silicates (allophan, imogolite) and pedogenic clay minerals (kaolinite, smectite, vermiculite). A very high reactivity of these minerals results from their high specific surface areas in combination with a high density of surface functional groups or permanent charge sites. Representing the most important adsorbents in soil they may control transport of nutrients and pollutants, regulate organic matter fixation or catalyse precipitation of new mineral phases. Characterisation of these particles and their surface properties thus seems to be a major pre-requisite for further research. Besides inorganic particles, also organic particles (e.g. plant debris) are of major interest for sorption and nutrient exchange processes. Especially the properties of charred plant residues are of relevance for long term carbon stabilization and retention of pollutants. Additional to our focus on single particles, the study of the nanoscale constituents in-situ in intact soil structures is of fundamental interest in the future. With the new NanoSIMS 50 L, funded by the DFG and run by the Lehrstuhl für Bodenkunde since March 2010, we are able to unravel processes at lateral resolutions of up to 50 nm. Using the nanoscale secondary ion mass spectrometry we aim to unravel sorption, diffusion and microbial processes at scales never resolved before in soil science.