Poster, International Symposium Soil processes under extreme meteorological conditions, Bayreuth: 25.02.2007 - 28.02.2007
Abstract:
Wetlands are subject to a complex interplay between various electron transfer processes that occur both under anaerobic and aerobic conditions. Under flooded conditions, the build-up of reduced compounds occurs that may be mobilized and exported from the wetlands during rainfall events. These processes significantly affect the dynamics of the export of redox-sensitive nutrients from headwater fens, such as phosphate, the fate of which is closely linked to the dynamics of iron. The temporal and spatial variability of the chemical composition in groundwater was investigated monthly at the wetland test site of the DFG research unit 562 in the Fichtelgebirge/Bavaria using a dense network of piezometers. We observed significant differences of P and dissolved Fe both in space and time in dependence of the ground water level. With decreasing water level, ground water became more reducing as indicated by the high Fe concentrations. It appears that the concentrations of both components do not depend on the water level which implies that water saturation does not control their mobility In an attempt to relate the observed mobility of phosphate to its chemical binding form we started an inventory of the spatial resolution of total P and Fe. In total 32 samples were collected and are being analyzed from three different depths. Additionally, a sequential extraction protocol (Psenner et al, 1984) for analyzing the P-speciation is being applied to six samples. The results of this study will be discussed in the Poster together with the ground water data.