Estuarine sediments chemical processes

The estuarine sediment was collected in an amount of ca. 650 kg near the Zandvliet-locks in the Belgian part of the Scheldt Estuary using a Van Veen grab. This material was polluted with the effluents of chemical and metallurgical industries. The sediment was oven dried at 105°C in layers of approximately 5 cm, crushed and shipped to the Joint Research Centre of Ispra (Italy) for further processing. 

Note that plots, such as Figure 5.1, provide information only on the net outcome of chemical reactions. In the case of iron, a small addition does take place in estuaries as a result of desorption of Fe from the surfaces of riverine particles. As these solids move through the estuarine salinity gradient, the major cation concentrations increase and effectively displace the iron ions from the particle surfeces. Since this release of iron is much smaller than the removal processes, the net effect is a chemical removal of iron. Sedimentation of these iron-enriched particles serves to trap within estuaries most of the riverine transport of reactive iron, thereby preventing its entry into the oceans. 

---