Original paper

Bergbaufolgelandschaft Ruhrgebiet: Geologische Ansätze zur Einschränkung der Auswirkungen des Steinkohlenbergbaus

[Mined Land in the Ruhr Area: Geological Assessments to bound the Environmental Consequences of Coal Mining]

Wiggering, Hubert

Kurzfassung

In Deutschland trägt die Steinkohle in erheblichem Umfang zur Energieversorgung bei. Der untertägige Steinkohlenabbau, die Kohlenaufbereitung sowie die Kohlenutzung als Energieträger beeinträchtigen teilweise erheblich die Umwelt. Das Zutagefördern der abgebauten Steinkohlen bedeutet eine immense Massenverlagerung. Bergsenkungen verursachen übertägige Reliefveränderungen, die eine Regulierung von Vorflut und Grundwasser notwendig machen (Polderung) und ganze Ökosysteme verändern. Durch die Mechanisierung des Abbaus nahm darüber hinaus der Anteil der nichtverwertbaren Nebengesteine stetig zu. Diese sogenannten Berge werden größtenteils auf Halden geschüttet. Die Halden sind nur schwer zu begrünen und damit nur unzulänglich in die Landschaft einzubinden. Stoffausträge aus den Halden beeinträchtigen Oberflächen- und Grundwässer. Die Standorte von Zechen und Nebengewinnungsanlagen - vor allem die ehemaligen Kokereistandorte - müssen häufig als Altlast eingeordnet werden. Darüber hinaus führt die Nutzung der Kohle in Kraftwerken zu vielfältigen Emissionen und damit zu einer Belastung des Umfeldes und einer Beeinträchtigung des regionalen Klimas. Diese Aus- und Folgewirkungen des Steinkohlenbergbaus müssen in langfristige Planungen miteinbezogen werden. Ziel eines systemorientierten Steinkohlenbergbaus muß es sein, bereits aus der Lagerstättenerkundung heraus mögliche Umweltbeeinträchtigung aufzuzeigen und von vornherein Maßnahmen gegen diese zu ergreifen.

Abstract

In Germany a considerable amount of the primary energy demand is supplied by domestic energy sources such as coal. The coal-bearing Upper Carboniferous of Germany includes paralic occurrences with marine connections and limnic occurrences, which were connected with interior basins of the Variscan fold belt. The largest coal deposits are mined in the Ruhr and Lower Rhine areas. At the Ruhr district the seams thicker than 1 m and less than 1500 m deep contain 43.0 billion tons of coal. The geological situation in the Ruhr area allows coal mining only in underground mines. The Variscan fold belt broadens in an eastly direction. Strong folding and faulting of the coal measures have led recent coal mining to be concentrated in the flat synclines. Thus, mining methods today are restricted to the extraction of selected reserve blocks. As a result nearly 60% of the geological reserves cannot be mined today. The extraction, transportation, and processing of coal has severe environmental impacts. The development of the highly mechanized underground mining has resulted in the displacement of very large quantities of coal and waste rock at the surface and underground. This has led to land subsidence, changes in groundwater flow, soil erosion, air pollution, and local climatic effects. Thus, in the Ruhr area more than 4,000 km2 is subject to subsurface mass displacement. The surface undergoes a mobile trough-shaped subsidence. The resulting deformations produce a range of different effects on geomorphology and hydrology/geohydrology. Abandoned coal mines have to be taken under long term drainage, pumping stations have to regulate the groundwater levels. There are complex conflicts between the tipping of coal mining wastes and other land usages. Coal mining wastes actually account for up to 50% of the run-of-mine production. From the 50 million tons of wastes mined annually only small portions are utilized or stowed underground, an average of 36 million tons per year accumulates in heaps. The weathering of coal mining waste heaps is strongly influenced by the changes in material parameters produced by mining, processing and heading up. The dominant weathering process is the oxidation of sulfides resulting in intense acidification after dissolution of carbonates by acid attack. Leachates components, e. g. sulfates, heavy metals, percolate through the water unsaturated soil-horizons underneath the heaps and mix with the groundwater. Thus, drinking water can be contaminated. Furtheron, coal burning is responsible for sulfur dioxide (SO2), suspended particulate matter (SPM), carbon monoxide (CO) and nitrous oxide (NOx) emissions. Mixtures of the air pollutants 03, SO2, and NOx are thought to play a major role in current forest decline. Apart from these local and regional exposure to atmospheric pollutants, globally increasing concentrations of CO2 require increasing and air pollution control strategies. Mining activities have contributed to the development of a great variety of secondary industries, such as coal refinement plants, steel industries etc. However, almost all of the former coking areas are suffering of pollution, mainly consisting of polycyclic aromatic (PAH) and monoaromatic (MAH) hydrocarbons. Due to the extent of pollution, the possibility of distribution in groundwater and soil gas, and planned restorations of the areas in question, reclamation measures, such as protection or decontamination, are required. In general, the devastated areas have to be restored, hazardous waste materials from mining activities must be treated, and the long term risks of coal mining must be assessed as part of long range planning and the protection of natural resources.

Keywords

Coal miningenvironmental impactsmass displacementwaste rock tailingssulfide weatheringgroundwater contaminationpower station emissionsland subsidencereclamation measures Ruhr DistrictNorth Rhine-Westphalia