Studies on hydrogeochemistry of uranium in groundwater of Tirunelveli district, Tamil Nadu, India

Uranium ingestion through drinking groundwater is hazardous to human health. The present study aims to find the quality of groundwater and uranium in the Tirunelveli district's groundwater. Two hundred eighty eight samples were collected and analyzed during pre-monsoon (August 2017, 144 samples) and post-monsoon (February 2018, 144 samples). Uranium concentration is in the ranges from 0.5 to 65 ppb (pre-monsoon) and 0.5-52 ppb (post-monsoon). All the samples in both seasons (except one sample during pre-monsoon) have a uranium concentration within the permissible radiological limit of 60 ppb, and 3% of samples in both seasons exceeded the chemical toxicity permissible limit of 30 ppb. The geochemical modelling studies confirm that the lower uranium concentration in groundwater samples may be due to the least dissolution of uranium with the predominantly distributed species of U4O9. Hydrogeochemical investigation shows that the weathering of rocks (sedimentary rocks), and the water is in disequilibrium with reverse ion exchange conditions in the collected samples. The spatial distribution map shows the polluted regions of the uranium and other analyzed water quality parameters (pH, TDS, Cl-, Ca2+, F-, Mg2+, NO3-, SO42-).