The hydrological and biogeochemical responses and dynamics of riparian wetlands play a critical role in the global cycling of Carbon C through the exchange of CO2 with the atmosphere, the emission of CH4, the production and export of dissolved organic carbon (DOC) and the storage of C.
The interactions between hydrology and biogeochemistry are important control mechanisms for wetland ecosystem function and the services they provide. The complex coupling between hydrology and biogeochemistry together with the consequent potential influence on biogeochemical hot-spot development, solute transformation and mobilization processes is only poorly understood.
We aim at an integrated understanding of complex riparian wetlands processes and their links to easily accessible hydrological metrics such as water table depth. New robust and autonomous methods can be used in further studies especially in remote locations. Thus, in this work we combine novel methods of high temporal resolution measurements of Rn-222 with continuous monitoring of DOC and complementing hydrological and hydrogeological observations. The objective is to understand how short term changes in hydrology (e.g. daily cycles, storm events) lead to preferential mobilisation and internal cycling (hot-spot generation) of biogeochemically active ions and molecules.
First results indicate an inverse diurnal cycle of Rn-222 and DOC in the Mid-August outflow of a riparian wetland site located within the Fichtelgebirge mountains in northern Bavaria, Germany. Rn-222 concentrations fluctuate by approx. 300 Bqm-3 between a minimum shortly after sunrise and a maximum in the late afternoon. These extremes correspond to a maximum and minimum in DOC concentration and water level elevation, respectively. DOC concentration varies around 2 mgL-1 and water level elevation around 1 cm. A fast response of distinct flow paths contributing to runoff after precipitation events is depicted in the data.