High fluxes of radium and barium from the mouth of the Ganges-Brahmaputra River during low river discharge suggest a large groundwater source

The annual flux of sediment from the Ganges-Brahmaputra River is among the highest in the world. The desorption of226Ra and Ba from this sediment produces a major point source of226Ra and Ba input to the ocean. Highest226Ra and Ba fluxes are expected to occur during high river flow (June-September) when most of the sediment is discharged. Surprisingly, during low discharge of the Ganges-Brahmaputra River, fluxes of226Ra and Ba to the northern Bay of Bengal are comparable to expected river-derived fluxes during peak river discharge. A large non-riverine source of Ra and Ba is required to explain the high fluxes during low river discharge. I suggest that this source is submarine discharge of groundwater containing high concentrations of226Ra and Ba. Total annual fluxes of226Ra and Ba to the ocean from this system are significantly greater than estimated previously.