BioGeoChemistry of Tidal Flats


M. Beck, O. Dellwig, G. Liebezeit, R. Reuter, H. J. Brumsack

Porewater Geochemistry of a tiday flat, NW Germany

In the Wadden Sea, a huge amount of water is incorporated in the sediments as pore water. Depending on the tidal regime, pore water drains from the sediment into the open water column and vice versa. As pore water is enriched in many elements when compared with seawater, its chemical characterisation is essential for the establishment of comprehensive mass balances of the Wadden Sea environment. Pore water lances are installed in the sediment to sample pore water at fixed locations over a long period of time at depths up to 3m. Pore water samples are analysed for nutrients, dissolved organic carbon as well as major and trace elements. Trace metals like Mn, Mo and V show increased concentrations with depth, while U concentrations are elevated near the sediment surface. Changing concentrations with depth can be explained by release at the sediment water interface, dissolution of oxides in sediment depths of several metres as well as by varying organic matter and oxygen concentrations.