Systematic non-conservative behavior of molybdenum in a macrotidal estuarine system (Aulne-Bay of Brest, France)

In this study, we focused on the behavior of molybdenum in a macrotidal estuarine system (Aulne-Bay of Brest, France). A systematic and pronounced loss of dissolved molybdenum was observed in the inner part of the system which was ∼10–30 fold higher than the inputs from the fluvial waters. Further to the examination of Mo concentrations in the water column and in the sediment pore waters over a 6-month period at a coastal station, we found that the systematic deficit in Mo concentrations in the coastal area was related to the loss of metal in the inner part of the system. We also estimated that benthic inputs in the downstream part of the system could be sufficient to counterbalance the upstream losses. After its incorporation in particles within the high turbidity area of the estuary, we postulate that Mo is redistributed downward following the deposition of the particles in areas of sedimentation and the redissolution of Mo in pore waters.