Application of Geophysical and Hydrogeochemical Tracers to Investigate Salinisation Sources in Nagapatinam and Karaikal Coastal Aquifers, South India

Groundwater in coastal aquifers of Nagapattinam and Karaikal regions are characterized by large saline variations with Conductivity levels up to (12,430.0 μS/cm). The high salinity collective with deterioration in water level creates a serious threat to current groundwater quality for human consumption. An integrated electrical resistivity and hydrogeochemical investigations were carried out to isolate the saline sources of groundwater. The Vertical Electrode Spacing isolated resistivity ranges between 0.5 to 1.5 μ m as saline intruded up to a stretch of 20 km inland along the eastern parts of the study area. A total of 122 groundwater samples were collected twice during summer and south west monsoon seasons and analyzed for 14 different water quality parameters using standard procedures. Results demarcate higher Conductivity (12,430.0 μS/cm), Cl− (5060.0 mg/L) and Na+ (1330.0 mg/L) indicating the saline nature of groundwater. The multi-rectangular diagram suggests groundwater influenced by recharge during south west monsoon and increasing salinity during SUM. The disseminate plots for various ions suggest saline water intrusion along the coastal tracts, cation exchange and rock water interaction along the south western and north western parts of the study area. Anthropogenic influences like sewage effluents and agricultural activities dominate south western parts of the study area. Higher Mn, Zn and Pb indicate influence from anthropogenic activities.