Environmental biogeochemical characterization of a lignite coal spoil and overburden site in Central Germany

Abstract During the 20th century lignite coal was an important resource for energy and chemical production in Germany. The legacy of the extended open pit lignite coal mining consists of spacious coal spoil areas and the occurrence of large and numerous pit lakes. Various approaches for the remediation of lignite spoil and overburden substrates have been carried out for the last 50 years. The results of former remediation can currently be evaluated by the long-term effects. It is important to learn from the success or problems of the former remediation activities, and to improve these methods for a successful current or future application in mining processes. Seepage waters from coal spoil sites can impact billions of m 3 of groundwater in affected areas over a very long time horizon (eternity impacts). A coal spoil site in Central Germany with cohesive soil substrates and layers of carbonaceous drift clays was studied, and biogeochemical parameters of this spoil substrate were characterized. The investigated site partially had a remediated topsoil layer for 40 years, and over this time agricultural cultivation of different plants (grains, legumes, Pocaceae ) has been performed. The counts of different microbial populations at several locations and in spatial distribution in the coal spoil substrate were investigated, and geochemical data of the coal spoil substrate were measured. The impact of microbial and geochemical processes on ground- and surface water was evaluated. The measurement results were compared with previous data of microbial communities in sandy substrates and their impact to the environment. Finally, the success of long-term remediation of such sites, the influence onto microbial life and impact to the environment were compared and discussed.