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Scientific Project A2 - Interactions between soil solution and mineral surfaces: significance for initial element cycling 

Staff

Main objective of the project is to characterize the contribution of the mineral parent material to the initial development of element cycles. On the one hand, processes of mineral weathering result in a source function, e.g. for nutrients. On the other hand, the development of reactive mineral surfaces and sorption capacity as well as complexation reactions may increasingly result in a sink function, e.g. for dissolved organic matter. For both functions the interaction with the soil solution as a mobile phase plays a crucial role. We hypothesize that in the initial phase these processes and interactions preferentially occur along existing and developing structures and patterns (e.g. preferential flow paths, surfaces of aggregates and soil skeleton, rhizosphere).

To find suitable parameters for the definition of development stages (subproject C5) we include the artificial catchment, the experimental plots, chronosequence sites on inland dunes as well as sites in glacier retreat areas in our investigations. Within the catchment we also study samples from semi-aquatic sites and surface water stretches in cooperation with other subprojects. In addition, identified small-scale structures and patterns will be sampled directly.

Our experimental approach includes the analysis of soil solutions and mineral surfaces at different spatial and temporal scales. Within the catchment (at the scale of ha) we follow the ´natural´ changes in soil solution composition and solid phases by continuous solution sampling (together with subproject Z1) and replicated soil sampling. In selected treatments plots of the experimental site (at the scale of m²) we study the impact of different vegetation on soil solution composition and element cycling dynamics. At the scale of soil columns the potential changes of interactions between the soil solid phase and soils solutions of different compositions are studied including stable isotope technique. At the smallest scale we investigate the changes in reactive surfaces (e.g. BET method, surface charge).