Assessment of the Flow Dynamic of a Mining Lake by Stable Isotope Investigations

For water samples from mining lake ML 111 of the Lusatian Lignite District and surrounding aquifers δ³⁴S(SO₄^-b), δ¹⁵N(NH₄⁺), δD, and δ¹⁸O (H₂O) values have been determined to asess the flow dynamic of the in- and outflow scenario. The high mineralization and acidification (pH > 2.6) of the lake water results from an intensive interaction with the surrounding dump sites and the inflow of extremely sulfate rich dump water (up to 4,100mg/1 SO₄^-). δ³⁴S values range from -7‰ to + 7°CDT in the inflow aquifers. The lake water is considered to be a mixture of different water bodies. The evaporation signature in the outflow aquifer suggests that the groundwater consists of 60% lake water. The nitrogen transfer is explained by ¹⁵N signature of ammonium. Sulfate reduction, perceptible in outflow and dump aquifer, cannot be proved within the mining lake by ³⁴S and hydrochemistry.