Hydrogeochemical Analysis and Paleo-Hydrogeological Modeling of Shallow Groundwater Salinization Processes in North China Plain

Abstract

Coastal groundwater salinization induced by marine transgression, sea level rising, and/or seawater intrusion due to anthropogenic activities has been a grand challenge for water security worldwide. Protecting the invaluable fresh groundwater resources from salinization necessitates the understanding of the spatial distribution of saline water and its sources. In this study, the process of groundwater salinization in two shallow aquifers of the North China Plain near Bohai Sea was characterized using hydrogeochemical analysis and paleo-hydrogeological modeling. The spatial variation in groundwater chemistry and isotopic composition in the two aquifers reflected the evident influence of paleo-transgression/regression events, while paleo-hydrogeological modeling further confirmed the primary role of several events of marine transgressions in groundwater salinization. Moreover, the fingering process of vertical saline water infiltration by free convection was identified from the results of the modeling, which was constrained by preferential flow paths and low permeability barriers of aquitards. The modeling results show that seawater infiltration was rapid, reaching a depth of 120 m B.S.L. in a short time at an average rate of 23 mm/yr. The trend of downward permeation of shallow saline water may threaten the groundwater quality of deep confined aquifers that sever as the main sources of water supply in coastal area of the North China Plain.

Keywords: Groundwater salinization, Paleo-hydrogeological Modeling, North China Plain, Marine Transgression