The improvement of Elbe water quality in the years 1990 – 1992 was mainly the result of closing factories and reducing production output in the area of the new German federal states. In the following years the water quality continued to improve as a result of rehabilitation measures, mainly by building municipal and industrial wastewater treatment plants and by implementing technological changes in industrial enterprises.
Changes of Elbe water quality since 1990s
The oxygen concentration required for life in the water has steadily increased. Oxygen concentrations near 3 mg/l, which is critical for fish, have only been measured in the Elbe section affected by high and low tide downstream of Hamburg in the summer months.
The average concentrations of heavy metals in the water phase have gone down considerably since 1990, for some heavy metals they have decreased many times over. These parameters include mercury, among other substances.
The positive changes of the Elbe water quality are shown in the two figures below that represent the development of the average annual concentration for the parameters mercury and ƴ-hexachlorocyclohexane/lindane on the basis of the samples taken at the Schmilka/Hřensko monitoring profile.
Even though large progress has been made, the nutrient load in the water phase (nitrogen and phosphor compounds) that is mainly emitted from diffuse sources (particularly from agriculture) is still high.
A part of the pollutants is also bound in suspended solids and in sediments. These are mainly heavy metals (mercury, cadmium, lead, zinc), specific organic substances (chlorinated benzenes, chlorinated pesticides, polychlorinated biphenyls, polycyclic aromatic carbohydrates) as well as tributyltin. These pollutants can be remobilised from sediments when the water level rises.