Tracing groundwater inputs to Bay of Bengal from Sankarabarani River Basin, Pondicherry, India, using continuous radon monitoring

Abstract

Sankarabarani river basin gains importance due to agriculture, an industrial and recreational activity that delivers large groundwater fluxes to the Bay. Attempt has been made by continuous monitoring of radon isotopes to evaluate submarine groundwater discharge with reference to groundwater and surface and pore water samples with distance perpendicular to the coast. 222Rn in groundwater samples were higher (543.0 Bq m−3) signifying major radon sources due to coastal groundwater discharge. Radon mass balance model attempted by considering fluxes like tides, atmospheric emissions, and sediment diffusion suggests higher groundwater and surface water fluxes (7.2 and 20.15 m day−1) near to the coast and higher fluxes (19.7 and 9.7 m day−1) in pore water away from the coast, suggesting influence of hydraulic gradient and radium retention in sediments. The average fresh submarine groundwater discharge calculated accounts 0.88 m day−1, higher in comparison with world studies.