Influence of Arsenic from Anthropogenic Loaded Soils on the Mine Water Quality in the Tin District Ehrenfriedersdorf, Erzgebirge (Germany)

Abstract

AbstractThe central part of the tin ore deposit Ehrenfriedersdorf/Erzgebirge, which was exploited from the 13th century to 1990, was flooded from 1994 to 1996. Since that time mine waters have flown through the gallery “Tiefer Sauberger Stolln” to the creek Wilisch in the Elbe river catchment area. The water at the mine portal shows high concentrations of arsenic and heavy metals. The average arsenic concentration is about 0.5 mg/L. Approximately two thirds of arsenic are transported dissolved. Where the mine water ascends from deeper levels, arsenic concentrations of about 0.4 mg/L were found. Here arsenic occurs predominantly particular. The mining gallery “Tiefer Sauberger Stolln” provides the unique opportunity of subsurface sampling for the identification of the arsenic sources under different hydrological conditions (normal and high water level). The sources of dissolved arsenic in the gallery part between the raise and the portal were determined and analyzed. Between these two monitoring points, many inflows of infiltration water were detected. The concentration of As in the infiltration water reaches up to 1.8 mg/L, which varies depending on the location in the gallery and the hydrological situation. The first part of the gallery was straightened, heightened and partly concreted with modern mining technique. The arsenic concentrations can decrease owing to high precipitation rates and snow melt events. The last part of the gallery was preserved due to low coverage. Here the arsenic concentrations in the infiltration waters increase with the surface water inflow. At a normal water level, 1 kg arsenic per day leaves the raise and 2.1 kg the gallery portal, which means that 50 % of the arsenic load comes from the infiltration water. At a high water level, 2.5 kg arsenic per day are transported through the raise and 8.2 kg per day through the gallery portal, which means that about 70 % of the arsenic load comes from infiltration water. The area of Ehrenfriedersdorf is characterized by a superposition of anthropogenic soil pollution over the geogenic inventory. There is a close connection between ancient soil contaminations by high amounts of water‐soluble arsenic compounds, e.g. arsenic trioxide formed by roasting the ores during ancient tin smelting, and high concentrations of dissolved arsenic in the infiltration water. The contamination of surface water and river sediments by arsenic is originating from an anthropogenic pollution of soils by ancient tailings via infiltration of water rich in arsenic into the mine gallery.