Discriminating groundwater salinization processes in coastal aquifers of southeastern India: geophysical, hydrogeochemical and numerical modeling approach

Groundwater salinization in coastal aquifers is mainly due to severe groundwater extraction, global sea level rise, usage of agricultural fertilizers and pesticides, waste disposal and influences of industrial and domestic effluents. The study area is the Nagapattinam and Karaikal coastal aquifers, noticeable with quick growth in population, severe industrial and urban activities resulting in groundwater abstraction ensuing deeper water level and salinization. Attempt has been made to discriminate sources of groundwater salinization using geophysical, hydrochemical and modeling techniques. The electrical resistivity survey isolated resistivity ranges between 0.5 and 1.5 Ω m as seawater intruded. Groundwater samples were collected for two different seasons and analyzed for major, minor and rare earth elements. The results signify higher conductivity (12,430.0 μS/cm), chloride (5060.0 mg/L) and sodium (1330.0 mg/L), indicating the saline nature of groundwater. The normalized REE patterns in groundwater exhibit enrichment of HREEs than LREEs due to higher mobility. The SEAWAT code predicted seawater intrusion along the eastern portion of the study area.