A MODEL TO PREDICT 238U IN AQUIFER ROCK BASED ON 222Rn AND 226Ra MEASUREMENT IN GROUNDWATER SAMPLES: A CASE STUDY AT SOUTH BENGALURU CITY, KARNATAKA, INDIA

Naturally occurring Rn-222 and Ra-226 concentrations were investigated in groundwater samples collected from different parts of South Bengaluru city using Smart RnDuo monitor developed indigenously by Bhabha Atomic Research Centre (BARC), India. The study area has been divided into two zones on the basis of external gamma radiation dose rates as zone A (100-200 nSv/h) and zone B (above 200 nSv/h). Radon concentration in groundwater for various sites, both supported (contribution from dissolved Ra-226 in water) and unsupported (contribution from aquifer rock), was estimated. Assuming that U-238 and Ra-226 are roughly in secular equilibrium in the aquifer rock, a model has been proposed to predict the uranium (U-238) content in the aquifer rocks using onsite measured Rn-222 concentration and dissolved Ra-226 concentration in the groundwater. Results of a case study carried out at South Bengaluru city, Karnataka, India have been discussed in the paper.