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Martin Novak, Czech Geological Survey (Czech Republic)
Lucie Erbanova, Czech Geological Survey (Czech Republic)
Ivana Jackova, Czech Geological Survey (Czech Republic)
Petra Pacherova, Czech Geological Survey (Czech Republic)
Frantisek Buzek, Czech Geological Survey (Czech Republic)
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The toxic waste repository at Pozdatky (western Moravia, Czech Republic) was opened in 1994 and closed in 1997. During the three years of operation, 136 different types of mainly industrial waste were deposited at the site, containing large amounts of toxic metals. At the same time, more than 10 thousand tons of ferrous sulfate were brought to Pozdatky from an abandoned chemical plant. The ferrous sulfate was soaked with 15 wt. % of sulfuric acid. This sulfuric acid was mobilized from the landfill by rainwater. Acid solutions moved downward while dissolving large amounts of toxic metals and transporting them into groundwaters in the granitoid bedrock. State of emergency was declared by regional authorities repeatedly after spill-overs of contaminated rainwater from the landfill reached a brook (pH of 1.9). Two villages downstream have not been affected by contaminated water yet. The distance of these villages from the landfill is 600 meters. Currently, the surface of the repository is sealed by a plastic cover. The drainage water is still highly contaminated (pH of 2.7).
Sulfur (δ34S) and lead (206Pb/207Pb, 208Pb/207Pb) isotope ratios of groundwaters collected from ca. 15 shallow wells situated 20-300 meters from the landfill were measured periodically between 2005 and 2007. Stream water in the valley (400 m downslope), rainfall, and several private wells in both villages and nearby natural springs were also sampled.
The Pozdatky water samples form four distinct mixing end-members, as seen in a δ34S vs. 1/[SO4] plot. These mixing end-members are: contaminated landfill waters (δ34S of 5.5-8.5 per mil; high SO4 concentration), mineral water in the village Dobra Voda (10.5 per mil), spruce canopy throughfall (4.0 per mil), and open area (bulk) precipitation (7.0 per mil; low S concentration). Private wells in the village, used by farmers for irrigating crops, have lower SO4 concentrations and lower δ34S values than the landfill leachates, but they currently form an outer envelope of the cluster of landfill data points. A time series of S isotope and concentration data will make it possible to identify any admixture of toxic leachates in wells used by local farmers.
The 206Pb/207Pb system at Pozdatky exhibits three mixing end-members (1.15 precipitation, 1.38 bedrock, and 1.25 landfill). Lead isotope systematics in the monitoring wells appear to contradict the finding of electrical profiling, which identified a high permeability zone in bedrock underneath the landfill. In the presumed pathway of preferential leachate movement the Pb isotope ratios differ from the landfill leachate.
Preliminary data on δ56Fe of groundwater fall in the range of ?2.0 to +0.1 per mil, with less negative values closer to the landfill. The δ56Fe value may be controlled by redox processes rather than by mixing of natural and anthropogenic Fe.
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