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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.
E. Lakshmanan has a teaching and research experience of more than 18 years. He is a professor and head of the Department of Geology, Anna University. His areas of research interests include environmental hydrogeology, with special emphasis to hydrogeochemistry, ground-water modeling, and unsaturated zone studies. He has carried out several funded research projects and consultancy work in the area of hydrogeology.R. Kannan is a research fellow in a project on ground-water pollution sponsored by the Department of Science and Technology, Government of India. He obtained his Master's degree in applied geology in 2001 from Anna University. His current research interests include the study of hydrogeochemical processes, unsaturated zone flow, and transport of contaminants.
M. Senthil Kumar was a research fellow in a project on solute transport modeling sponsored by the All India Council of Technical Education, Government of India. He obtained his Master's degree in applied geology in the year 1999 from Anna University. His research interests include ground-water flow and solute transport modeling. At present, he is working as a scientist in the Central Ground Water Board, Government of India.