Analysis of multiple salinization processes and quality of shallow and deep groundwater in coastal delta using hydrochemical approaches: A case study in Luanhe River Delta

Coastal groundwater salinization, contaminants and water resource shortage have become the main coastal groundwater environmental issues globally, drastically affecting human living and ecological environments. This study provides a new insight into the salinization process and influencing factors of groundwater in different aquifers of coastal deltas. Luanhe River Delta, a typical estuarine delta, is used to analyze multiple salinization processes and the quality of shallow and deep groundwater using hydrochemical and monitoring approaches. The analysis has verified the obvious difference of groundwater quality and, the location and influencing factors of saline-fresh water interface in shallow groundwater and deep groundwater. For shallow groundwater, water-rock interactions, seawater intrusion, evaporation and reclamation are the main salinization processes. For deep groundwater, water-rock interactions, saline water intrusion, evaporation and marine transgression are the main salinization processes. The salinization and quality of groundwater are divided into four units in shallow groundwater and three units in deep groundwater. Coastal groundwater salinization causes complex groundwater quality unsuitable for human consumption in some areas. Groundwater resources in different aquifers of coastal deltas should be managed and used in different zones. Local governments should formulate groundwater exploitation plans and rationally plan for groundwater utilization.