Hydrobiogeochemical impact of the underground mining discharges in Gessental, Ronneburg

This work deals with the evaluation of the impact of AMD (acid mine drainage) influenced discharges in the main discharge area Gessental of the former U mining area Ronneburg. Here, AMD from heaps at the south of Gessental, infiltrated into stream- and floodplain sediments. This is due to an influent situation resulting from draining of ground water and the development of a depression cone. Afterwards, flooding of the underground mining caused an effluent situation. This is accompanied with high volumes of rising AMD influenced waters escaping the surface from not backfilled drillings and producing another mining induced contamination. Restructuration steps lead to i.a. the construction of a bypass, resulting in an isolated part of Gessenbach. The aim of this work was to characterize the recent discharges and their influences on the pre-contaminated ecosystem, especially on the geosubstrates and the biomass within the isolated part of Gessenbach. For comparison, biomass and soil samples from a location which is not impacted by the recent discharges were analyzed. For this purpose, element contents from water, soil and biomass were determined and bioconcentration factors were calculated using the bioavailable fraction of soil as reference. Herein, the environmental relevant elements Al, Fe, Ni, U and the group of Rare Earth Elements (REE) were focused. Furthermore, a source analysis was performed using the REE and Sr/Nd isotope ratios. This work presented a decrease of elements along the flow path of mining drainages in Gessental which either remain as precipitates or were taken up into or sorbed onto biomass. For example, Sr isotopes were demonstrated to be preferentially taken up from the water phase. Whereas the combination of REE and Nd isotope ratios depicted a species dependent uptake of REE using the same source. Thus, REE and Sr/Nd isotope ratios are a suitable tool for source analyses differentiating between water and soil in a mining impacted area.