The former Goitsche opencast lignite mine is currently being flooded. The aim of the investigations is to gauge how flooding is changing the soil, leachate and groundwater in the profile of a highly acidified dump in the mine. The interaction between the soil/soil water/leachate, groundwater/aquifer and lake/lake sediment compartments is to be qualified and quantified.

Ion balances indicate that the substance inventory of the recultivated surface layer (neutral pH values, relatively low conductivities and substance concentrations) corresponds to that of natural soil.

So far, only layers affected by leachate and with sufficient oxygen at depths of 2, 3, 8 and 13 m with pH values of 3-4 are characterised by high balance sums. In terms of anions the balance is dominated by sulphate; regarding cations it is determined by Ca and Mg along with significant fractions of Al, Fe and protons.

A change in the milieu conditions is apparent in the areas affected by rising groundwater (28 and 23 m below the surface). Against the background of falling conductivities, reduced redox potentials, declining oxygen levels and pH values of around 7, the Fe and Al levels are dropping to uncritical levels. In addition, the levels of heavy metals are significantly decreasing, resulting in the improvement of groundwater quality.