Tuesday, 11 July 2006

Lysimeter Experiments to Estimate Parameters for Recultivation of former Lignite Mining Areas with Sewage Sludge Composts.

Sabine Bernsdorf1, Sebastian J. Tauchnitz1, Ralph Meissner2, and Holger Rupp2. (1) Martin-Luther-University Halle-Wittenberg, Institute of Agricultural Engineering and Land Use Management, Ludwig-Wucherer-Str. 81, Halle (S.), D-06108, Germany, (2) UFZ Centre for Environmental Research Leipzig-Halle, Department of Soil Science, Lysimeter Station, Dorfstrasse 55, Falkenberg, 39615, Germany

Since 1920, lignite mining in central Germany lignite district has been carried out in large open-cut brown coal mines. Large areas have been directly affected by these mining activities. Areas which are still active and those being prepared for relict lakes (containing flooded residual basins) alternate with recultivated areas. Some of which began to be used for agriculture decades ago. The primary aim in these recultivation areas is to obtain a vegetation cover by application of fertile substrates. Sewage sludge compost with its high content of organic matter can be used for recultivation. But until now, in Germany there is no legal basis for the use of sewage sludge compost in the landscape reclamation. Lysimeter experiments in different scales are started to tackle this problem. The main objective of this study is to estimate the optimal thickness of the sewage sludge compost recultivation layer to avoid seepage water formation. In total 24 heaps (basic area 5 m x 6 m) were designed to investigate the effects of different cultivation layer thicknesses of 0.5 m, 1.0 m, 1.5 m and 2.0 m on seepage water quantity and quality. Each of these heaps was equipped with two cylindrical lysimeters with a diameter of 0.4 m. The seepage water from the lysimeters (if occurred) is sampled outside of the heap. The sewage sludge compost was mixed with different amounts of sand and clay. Twelve heaps are covered with grass and the other 12 are bare. Furthermore, 24 laboratory lysimeters with a diameter of 0.2 m and depths comparable to the heaps were arranged. This experimental design allows a direct comparison between field and laboratory lysimeters. The poster will inform about the optimal design of the compost cultivation layer. The results show that sewage sludge compost can be used for the recultivation of former lignite mining areas. Reduction of seepage water can be achieved by increasing the thickness of the recultivation layer, by covering with grass and by blending the compost with soil material to increase the soil water storage capacity. The seepage quantities are comparable in fled and laboratory lysimeters.

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