Author(s): Schankat; Mirko; Hinkelmann; Reinhard; Schluter; Michael
Linked Author(s): Reinhard Hinkelmann, Michael Tadesse
Keywords: Submarine groundwater discharge (SGD); Numerical modelling; Advection; Diffusion; Dispersion; Seep; Sensitivity; Density-driven; Rhizon sampling
Abstract: A one-phase/two-component (fresh water, salt water) model concept for flow and transport processes in a porous medium was applied for modelling submarine groundwater discharges (SGD) from so-called “seeps” into the overlying sea water. This approach accounts for density-driven flow associated with transport processes between fresh water and salt water (concentrated brine), which are fully miscible. The system is highly controlled by advective flow processes in the seep centres and dispersion processes. Flow and transport processes around submarine groundwater springs (so-called “seeps”) were investigated with special emphasis on sensitivity of governing model parameters. Physical process parameters like the molecular diffusion coefficient and the dispersion lengths were found to be very sensitive, whereas most of the model domain parameters like fresh water inflow width and model domain width were found to be less sensitive. At the Alfred-Wegener-Institute for Polar and Marine Research (AWI), pore water sampling of chloride concentrations was carried out in the uppermost part of the marine sediments using horizontal and vertical Rhizon sampling. Also submarine groundwater discharge measurements were taken using a Benthic Chamber. The model set-up in this research was used to compare simulation results, i. e. resulting chloride concentration profiles from submarine groundwater discharge from seeps, with Rhizon and Benthic Chamber measurements at a site in the Wadden Sea of Sahlenburg, Germany. Good agreement between measurements and simulation results was achieved for different seeps, i. e. for different submarine groundwater discharge rates or seep widths, using dispersion lengths of 0. 5 mm (longitudinal) and 0. 05 mm (transversal).
Year: 2007