Hydrochemistry of the drained Skjernå delta. (Iron pollution of the river Skjernå and Ringkøbing fjord, Western Jutland)

Preliminary results of analyses of the drainage water in the Skjernå delta are presented.

The concentrations of weathering products in water from the separate areas drained by the five pumping stations are clearly different.The leaching process shows a typical seasonal cycle caused by an intensified oxidation in the dry summer periods followed by a sudden mobilization of the accumulated weat hering products in the rainy autumn and in winter.

The iron content in the drainage water from the areas seems to be present primarily as Fe²⁺ or possibly as iron-humic complexes. Both the state of the iron and the reducing environment in the Sydlige parallelkanal may prohibite a precipitation of iron . It is therefore concluded that only liming of the ironbearing water is insufficient for precipitation of the iron befo e the outlet in the Ringkøbing fjord.