Uranium Contamination of Groundwater in Southwest Parts of Punjab State, India, with Special Reference to Role of Basement Granite

The state of Punjab is known for potential aquifer system and also experiencing heavy groundwater extraction mainly to cater the irrigation sector from the shallow aquifers (<50 m depth). Uranium concentration in the groundwater from shallow tubewells (<50 m depth) ranges from 1.78 to 261 µg/L. Uranium concentration shows spatial variations even within a short distance of 200 m. In majority of samples, uranium concentration exceeds the permissible limit of 15 µg/L prescribed by WHO (2004) and 60 µg/L prescribed by AERB, DAE (2004). Most workers link the presence of uranium in groundwater to basement granite. The results of uranium analysis of basement granite sample collected earlier from Phulka (29° 29′; 75° 08′) during exploratory drilling carried out under UNDP-CGWB project reveal a normal concentration of 3.686 µg/g. Further, the granite core sample shows negligible (0.01 mR/h) radioactivity. In addition, granitic basement occurring at the depth of 242 m or more at other places could not have contributed uranium to groundwater occurring at shallow depth (up to 50 m). Uranium concentration in sediments/soils was found to range between 1 and 3 µg/g. Mobilization of uranium from sediments/soils under favorable geochemical conditions seems to be the possible explanation for uranium contamination in groundwater.