This is a follow-on of a running SNF project (NSF K-23K1-120601) with the same title. As the previous project it addresses the most important gaps in the knowledge of biogeochemical weathering in alpine areas. Weathering is seen as provision of nutrients that are required by the pioneering life in deglaciated alpine areas, where soil development is at its initial stage. In the course of glacier retrieval and loss of permafrost, rocks become loose and subject to erosion. This development can be limited or prevented only if soil and vegetation cover is developed rapidly. Where terrestrial life has to evolve under harsh conditions, microbial colonization is slow. This is related to the fact that dissolution of most primary rock-forming minerals is limited by slow reaction kinetics. The project is focused on the mineral-water interface, where aqueous solutes act directly as dissolution-promoting agents. The rates are dependent on intrinsic (e.g. mineral-surface properties, weathering state) and extrinsic factors (e.g. temperature, pH, redox conditions, presence of biotic exudates). Fine rock materials, that are most important for nutrient supply can have either freshly exposed or weathered surfaces. Both kind of rock material are studied systematically with respect to proton- and ligand-promoted dissolution, considering cyanide as well as the organic ligands oxalate and citrate (although salicylate has been suggested in the original proposal). In addition to freshly ground granite from the Damma glacier area, we sampled and investigated sediments from differently exposed sites. The fine rock material was exposed to the field conditions in parallel to reference material of mica (in part biotite, K and Fe source), and apatite (accessory mineral, P source).
The main objectives of the running project include the study of (1) intrinsic and (2) extrinsic weathering factors, (3) ligand-promoted dissolution, (4) the weathering potential of cyanide-producing bacteria, and (5) computer modelling of weathering processes in the glacier forefield. In deviation of the original proposal, the extrinsic factor temperature was not investigated, as well as the comparison of flow-through vs. batch experiments. This decision was taken after intense work on the experimental setup, where we experienced serious difficulties to control the partial pressure of the hydrogen cyanide gas in the reactor. Consequently we decided to stick to batch experiments and to use sodium cyanide salt in combination with pH adjustment. The main body of the other tasks are planned to be fulfilled in the course of the remaining project time including the extension period.