Groundwaters from shallow and deep wells were collected on seasonal basis from a tropical enclosure of 2900 km2 of Udupi district, Karnataka, Southern India. Groundwater samples were analyzed for major ions, trace elements and dissolved organic carbon (DOC) from silicate rock dominated two composite river catchments, Swarna-Madisal-Seetha for a period of two years and Halady-Chakra-Kollur (Gangolli basin) for a period of one year. Physico-chemical parameters vary seasonally with average values of temperature 27.5°C and 26.8°C, pH 6.1 and 5.8, electrical conductivity 102.7 µS cm-1 and 58.3 µS cm-1 and dissolved oxygen 4.54 mg L-1 and 4.49 mg L-1 in Swarna and Gangolli composite basins respectively. DOC concentration measured in groundwater samples range between 0.34 mg L-1 in dry season and 1.8 mg L-1 in monsoonal season indicating an overall higher correlation with Al. The total dissolved solids is found to be higher in deep wells with a maximum of 344.5 mg L-1 and lesser concentration of 32.3 mg L-1 in shallow open wells with an average of 100.7 mg L-1 for the sampling locations. Abundance of major cations reflects the dominance of Ca followed by Na, K, Mg, Al and Fe whereas the major anions follow the trend of higher concentration of HCO3 followed by Cl, NO3, SO4 and F. In general, higher correlation of Ca with HCO3 and pH is observed for the study period. The study shows the influence of lithology and climate over the major ion and trace element composition in the inland samples and marine aerosol impact over the coastal track. The impacts of anthropogenic activities at few locations are supported by higher nitrate and sulphate concentration in shallow groundwaters.
Discipline Categories: Geochemistry, Geochemistry, Organic, Environmental GeosciencePreferred Presentation Type: Oral