Consequences of mining: the suffering of the Spree
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The Spree (in Sorbian Sprjewja/Sprewja) has its source in the Upper Lusatian Highlands and meanders for almost 400 kilometres from Saxony and Brandenburg to its mouth in the Havel in Berlin-Spandau. The Spree is first mentioned in writing in 965 as the Sprewa in a document of Otto I. The name is said to originate from the Germanic basic form of “spreu?” (meaning to spray, sow or sprinkle). On its route through eastern Germany, the Spree crosses the lignite mining areas of Lusatia.
The lignite mine in Lusatia required and still requires a massive water table drawdown in order to prevent flooding of the pits. The groundwater level needs to be lowered to a depth of 100 metres below the ground surface. Owing to the water table drawdown, the mineral pyrite (FeS2, also known as “fool’s gold”), which is present in the subsoil, comes into contact with oxygen. Contact with oxygen and water sets a weathering process in motion that results in dissolved iron, sulphate and acidification. When the groundwater rises again, the weathering products are flushed out and enter the fresh water of Lusatia and the Spree. The Spree is also contaminated via seepage from the spoil deposits within and outside the surface mines and directly as a result of surface mine drainage. The dissolved iron then flocculates in the neutral waters in the form of iron hydroxide (known as iron ochre). Depending on the speed and flow and how long it has been there, it becomes deposited on the river bed as iron hydroxide sludge.
The discharge of ferrous water to the fresh water can result directly in depletion of fauna and influence the flora in the fresh water owing to toxic effects. For example, concentrations of 2 to 3 mg/l in dissolved divalent iron can lead to a complete loss of fry. High concentrations of iron flakes can clog the gills of fish. Deposits of iron hydroxide mud on the river bed cause soil life and aquatic plants to die, which in turn has an effect on the subsequent food chain. Excessive acidification is lethal for most animals and plants in fresh water.
The sulphate, which is formed by pyrite oxidation, is likewise flushed out when the groundwater rises again and is carried into the Spree. Large quantities of sulphate also enter the Spree from the dumps of the active mine in Saxony and Brandenburg. In the medium term, sulphate poses a threat to the drinking water supply of the capital Berlin and to Frankfurt (Oder) via the Spree. The threshold value for sulphate in drinking water is 250 mg/l. Sulphate is highly inert and is carried a very long way in flowing water. Long-term consumption of water with high sulphate content can result in disturbances to our digestive systems. In addition, sulphate can damage older concrete structures, such as bridges, in particular. Higher sulphate content can also lead to increased algae growth in lakes.
The effects of decades of intensive mining in Lusatia can be felt everywhere in Saxony and Brandenburg. That jeopardises not only the drinking water supply, but also a whole business sector, namely tourism. If the iron clogging spreads to the inner Spreewald, tourists will stop visiting, because nobody wants to spend their holiday in a region with ochre brown sludge.
Further trouble is brewing, since in recent years international gas and oil corporations have also increasingly discovered the region to the left and right of the Spree and secured claims there. If the corporations use the controversial fracking method, which involves pumping a cocktail of chemicals into the ground to extract natural gas or petroleum, the groundwater could be massively polluted, as examples in the USA show.