HYDROCHEMISTRY OF MINE WATER DISCHARGES IN THE ABANDONED UPPER BAVARIAN PITCH COAL MINING DISTRICT/GERMANY

摘要

Upper Bavaria hosts several dozen of abandoned underground pitch coal mines where mine water is discharging into the receiving steams. First mining activities in the Upper Bavarian pitch coal district date back to the end of the 16th century, but industrial coal mining started in the 19th century. In 1971 the last remaining pitch coal mine in PeiBenberg closed after having produced 40 Mt of coal. None of the mine water discharges is currently treated and since its closure no scientific investigations have been conducted. The paper describes the location of the abandoned coal mines and the results of water analyses at 17 mine water, discharges. At all locations also the flow was measured, which ranges between 1 and 2100 L/min. Because the coal mines are located in carbonate rich host rocks most of the sites cause no visible environmental impact to the receiving streams. Most of the pH-values range between 6.7 and 8.3 and therefore are an indication for the well buffered discharge waters. Electrical conductivities reaches values of up to 4.9 mS/cm and at least 6 discharges cause a local negative impact to the receiving streams. The most problematic discharge is that of the Friedrichstollen with a flow of 2 m3/min, an electrical conductivity of 4.9 mS/cm and an iron concentration of 13 mg/L. In general, all waters are Ca bi-carbonate waters with some Ca-Mg sulphate waters.