Saturday, 15 July 2006
148-2

Preliminary Results from Special Lysimeters on the Recultivated Dump of the Former Lignite Mine Witznitz, Germany.

Ulrike Haferkorn, Staatliche Umweltbetriebsgesellschaft, Kleinsteinberger-Str. 13, Brandis, Germany

About 170 km2 of mine dump area and 70 km2 of water surface have been created north and south of Leipzig as a result lignite mining in Central Germany's mining district. Once mine dewatering stops and the remaining pits fill with water, it is expected that by the year 2010 about 60 percent of this area will have shallow groundwater levels. Areas with shallow groundwater will be characterized by permanent soil wetness and low pH, high acidity percolate and groundwater. Furthermore, soil water budget and water quality processes will be significantly different from natural soils. No measured data were available that address this issue in Central Germany. Therefore, two new lysimeters were installed on a reclaimed dump of the former Witnitz mine south of Leipzig that was closed 30 years ago. In spring 2004, the Federal Environmental Management Services started to operate these lysimeters to determine: (i) maximum evapotranspiration caused by the weather for different vegetation types, (ii) negative groundwater recharge due to transpiration, (iii) substance transport and transformation in the zone of changing groundwater levels, (iv) substance uptake by plants, and (v) possible plant damaging effects of these substances. These tasks and specific characteristics of the area represented a special challenge for installing and operating the new lysimeter stations. Two soil monoliths 3 m in height with a surface area of 1 m2 were constructed using the method developed by Meissner et al (2000) for undisturbed sampling. Both monoliths were installed in a container on the mine dump, each on three scales. A filter 2 m below the surface connected the two lysimeters and the surrounding dump area to prevent differences in water levels between the lysimeters and the surrounding dump. Exchange flow rates were measured and recorded by a new flow gauge that measured rates from 3 to 300 ml/h. Percolate was gathered with a tension-regulated suction probe. The lysimeter bodies were fitted into waterproof PE-HD containers such that the lysimeter surface was at the same level as the surrounding soil surface. To avoid oasis effects, crops planted on the lysimeters corresponded to surrounding crops (corn in 2004, peas in 2005). All data from the lysimeter station (including meteorological data) were recorded on a data logger and sent to a computer at the UBG in Brandis via GSM-modem.

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