A Study on Variation in Ionic Composition of Aqueous System in Different Lithounits around Perambalur Region, Tamil Nadu

Hydrogeochemistry of a region is a reflection of the hydrodynamic processes, Lithological composition and physical constraints. Case study has been carried out in a varied lithologica] terrain with Archaean, Gondwana and Cretaceous rocks to unravel the hydrogeochemical process. The study area is around Perambalur region lying between Latitudes 11°O8OO" - ll°31OO" and Longitudes 78°35'00" - 78°5950" P_co2 values of water samples show wide variation in lithology, reflecting higher saturation index in carbonate minerals Mixing of water was witnessed in the Cretaceous formation Release of bicarbonate ions into the system is mainly derived from weathering of carbonate minerals reflecting lesser significance of silicate weathering. Thermodynamic equilibrium plot shows grouping of samples in the Kaolinite field with seasonal variation Saturation index (SI) for carbonate minerals is higher than silicate minerals Dilutions of samples are noted in the Archaean formation during Post-Monsoon season and migration of SI plume of carbonate minerals is towards southeast during Post-Monsoon season Geochemical reactions determining the water chemistry of the study area are also obtained by statistical analysis.