Geochemical signatures of ground water in a part of Kancheepuram district, Tamil Nadu, India, were used to identify the chemical processes that control hydrogeochemistry. Physical parameters, such as electrical conductivity, pH, and major ion concentrations, such as Ca, Mg, Na, K, Cl, HCO3, CO3, and SO4, of ground water were taken into consideration. Concentrations of these cations and anions in the ground water vary spatially and temporally. Abundance of these ions are in the following order: Ca > Na > Mg > K = HCO3 > Cl > CO3 > SO4. Ca-HCO3 and Ca-Cl-HCO3 are the dominant hydrochemical facies of the study area. Interpretation of hydrochemical data suggests that calcium carbonate dissolution, ion-exchange processes, silicate weathering, and mixing of aerosols are responsible for the ground-water chemistry of the study area. Identified hydrogeochemical processes were verified and quantified using hydrogeochemical inverse mass-balance modeling (net geochemical reactions along a flow path, NETPATH). The models suggest that carbonate dissolution, halite dissolution, Ca/Na ion exchange, and Mg/Na ion exchange are the major processes that control the ground-water chemistry. Gypsum dissolution and illite precipitation/dissolution are also partly responsible for the chemistry of ground water.

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