Geochemical characterisation of Wadden Sea pore water and its influence on the open water column

In the Wadden Sea, a huge amount of water is incorporated in the sediments as pore water. Depending on hydrological and geological conditions as well as on the tidal regime pore water drains from the sediment into the open water column. As pore water is enriched in many elements when compared to seawater, its chemical characterisation is essential for the establishment of comprehensive mass balances in the Wadden Sea environment.

Pore water needs to be characterised both in temporal and spatial dimensions to explore its influence on the water column. To achieve this, pore water samples are collected employing two different systems. A portable probe kit is used for pore water sampling at different locations in the backbarrier tidal flat, whereas transects of fixed pore water lances are to be installed to sample pore water at constant locations over a long period of time. The latter lances are designed to take samples at different depths of down to 5 m below the sediment surface. Pore water samples are analysed for nutrients, dissolved organic carbon (DOC) as well as major and trace elements. Additionally, temperature, conductivity, and pressure are also measured at several depths in order to investigate the water flow within the tidal flat sediment.

The work on this project started in summer 2004. First results will be available in the near future.

Pore water sampling with a portable probe kit in the backbarrier tidal flat (Janssand)