ABSTRACT
The chemical processes at the fresh/seawater interface in a shallow sandy aquifer were studied. The results indicate that a coupling of calcite dissolution, redox- and exchange reactions are responsible for the evolution of a sodium bicarbonate type water. Methanogenesis with the related production of CO2 is driving the system. Also the results indicate that the sodium bicarbonate type water develops without the advective displacement of the fresh-/seawater interface normally attributed with it. A proper understanding of these processes is a prerequisite for predicting effects of sea level changes or overexploitation of groundwater resources.
