Investigation of dissolved uranium content in the watershed of Seine River (France)

A systematic survey of dissolved uranium activity was carried out in the Seine and the Marne over one year. A small watershed, the Grand Morin, included in the Seine one, was also investigated from stream to medium-sized rivers. The Melarchez stream exhibits low but variable dissolved 238U levels (3.3±2.0 mBq l−1). Thereafter, uranium activities show a rapid increase to reach, from the Grand Morin River, a rather constant range (8–11 mBq l−1). On the Marne before the confluence with the Seine, dissolved 238U is nearly invariable (9.1±0.8 mBq l−1), for flow rates comprised between 60 and 423 m3 s−1. Dissolved 238U in the Seine corresponds to almost triple the global mean riverine uranium concentration. In the estuary of the Seine, uranium shows a gradual increase, resulting from conservative mixing of river with sea waters.