Spatiotemporal variation of dissolved 238U in the Gironde fluvial–estuarine system (France)

Dissolved uranium (238UD) was measured within the Gironde fluvial–estuarine system (France), which is well known for its heavy metal pollution and its subsequent environmental effects. Dissolved 238U activities exhibit the highest levels and variability in the small watersheds of the Isle and Riou-Mort rivers, ascribed to low discharges and the occurrence of peculiar features (local U ore deposits; Permian layers). The major tributaries of the Gironde Estuary: Garonne, Lot and Dordogne, show rather stable 238UD, higher than the global mean riverine uranium activity. In the Gironde Estuary 238UD behaves conservatively along the river–estuary–ocean transect. Dissolved 238U distribution in the Gironde fluvial–estuarine system can be explained by the characteristics of considered drainage basins. There is no evidence of anthropogenic pollution.