Modeling of physical and geochemical behaviors of saltwater in a coastal aquifer

Groundwater quality is affected by the various reactions such as precipitation of dissolved ions, solid-liquid phase interaction, and the bacteriamediated reduction-oxidation process. The geochemical properties in coastal aquifers are unique and important for the management of groundwater environment. Although the studies analyzing the hydrological behaviors have been intensively done up to now, a study of coupling both groundwater flow and geochemical analysis is limited. In this study, the one-dimensional multicomponent solute transport model which accounts for the cation exchange reaction and the reduction reaction induced by anaerobic degradation is studied. It is found out both through experiment and numerical simulation that the cation exchange process is significant at the frontal part of the seawater infiltration, while reducing process by the bacteria mediation takes places at the entire soil column except for the top of the soil where dissolved oxygen infiltrates. Saltwater intrusion into a coastal aquifer is a traditional but still important for the hydro-geologists and civil engineers even at present time. Contamination of salt is a trouble for various freshwater uses. Therefore, much attention has been put on the movement and potential contamination. Meanwhile, the geophysical study is solely carried out. However, the consistent and accurate conclusion will be hardly obtained due to the complicated and limited information on the aquifer properties. In order to get a confident conclusion that can be agreed by the researchers in various fields, an interdisciplinary approach anticipating both hydrological and geochemical processes is indispensable.