WPŁYW ZAPRZESTANIA ODWODNIENIA ZG „KONRAD” NA CHEMIZM WÓD PODZIEMNYCH SYNKLINY GRODZIECKIEJ W REJONIE IWIN KOŁO BOLESŁAWCA

Abstract

IMPACT OF THE ABANDONMENT OF DEWATERING IN THE “KONRAD” MINE ON GROUNDWATER QUALITY OF THE GRODZIEC SYNCLINE IWINY REGION NEAR BOLESŁAWIEC

Abstract. The Grodziec Syncline is situated in the Kaczawskie Foothills near Bolesławiec in Lower Silesia. Copper ore mining activity in the “Konrad” and “Lubichów” mines began in the early 1940s. The “Konrad” mine stopped the copper ore exploitation at the end of 1988. The impact of long-term mining inflow resulted in the formation of a cone of depression in the Zechstein water-bearing horizon and indirectly in the Quaternary aquifer due to hydraulic connection. The total surface of the cone of depression in the in the Zechstein aquifer is 29 km2, whereas in the Quaternary aquifer it is about 64 km2. The most important role in the drainage of the “Konrad” mine was played by the Zechstein aquifer that is composed of porous-fractured-cavernous limestones. The “Konrad” mine closure began in 2001 and included two stages. During the mining activity, HCO3–Ca–Mg and SO4–Ca–Mg chemical water types were identified within the Zechstein carbonate- rock aquifer. After 2001, groundwater from old mineworking in the Zechstein aquifer observed at AQ-1 and AQ-2 piezometers and K-I and K-II mine shafts, became more acid and more contaminated by sulphates and iron. Oxidation of sulphides is the initial reaction of groundwater acidification, which is neutralized by limestone dissolution. At the piezometers located out of the mineworking area, groundwater quality changes in the Zechstein aquifer were not observed.