Origin of sulfates in the post-mining lakes in the eastern part of Muskau Arch (Polish-German borderland)

Exploitation of lignites, carried out within glaciotectonic structures of Muskau Arch, led to formation of numerous post-minng lakes impacted by Acid Mine Drainage (AMD). The isotopic analyses decribed in this paper allowed for identification of sources of the dissolved sulphates in the waters of two representative lakes. One of the sources of sulfur isotopes could be oxidation of sulphides (supplied in debris sliding from the slopes of waste dumps, which are surrounding the lakes) in the water column. The fraction of oxygen from water in forming the sulphates vary from about 5% to 25% in the first lake, while in the second it falls within the range 25%-85%. The research confirmed that the main source of sulfates in the lakes is the oxidation of pyrite.