Study of the behaviour of dissolved silica in the estuary of the Scheldt

Evolution of the silica dissolved in the Scheldt estuary shows that the reduction in silica content observed is much greater than that predicted by the dilution curve computed from the mixture of fresh water rich in silica and surface sea water.According to the results reported in the literature and our own experiments, the removal of silica from the solution is not due to a reaction with clay minerals in suspension, but to biological activity, essentially by diatoms that live preferentially in saline waters.After death, diatoms that become part of the sediments return silica to the interstitial waters, which can then combine with disordered clays of continental origin to give rise to new aluminosilicates richer in silica and in alkaline or alkaline-earth ions