Abstract: Zn-Pb ore deposits in Olkusz area (S- Poland) occur within a Triassic dolomites and limestones. These carbonate rocks constitute also a large fissured-karstic type aquifer. Mining exploration and ore processing, which began in the Middle Ages, caused serious changes in groundwater flow regime and groundwater chemistry. It also influenced surface waters causing important changes in surface morphology and created multiple potential sources of environmental pollution. The main subjects of this investigation were impacts of the ore mining on environment thus the authors focused on a mining drainage and changes in chemical composition of groundwater close to mines' excavations. Underground mining inevitably leaded to intensive dewatering of excavations and surrounding aquifers in order to make deep exploration and exploitation of ores possible. In the Olkusz area, long-term dewatering created a depression zone of regional scale. It is estimated that it affected the area of over 400 km2, and influenced all aquifers remaining in hydraulic connections (Quarternary, Jurrasic, Triassic), and that in central part of mining region a water table level has dropped up to over 150 metres. As an effect of this drop many springs cease to exist and water levels observed in wells significantly decreased. Due to significant increase in hydraulic gradients' values in some areas, deformations of land surface appeared (e.g. suffosion and karstic pits, irregular subsidence). This caused damages in infrastructure and buildings. Changes in water regime triggered activation of numerous sources of pollution (internal and external), mostly in Triassic aquifer. External sources of pollution are located at the surface or just below the surface in shallow excavations. Mining drainage caused contamination or pollution of water mostly within Triassic aquifer, with substances from those sources. The internal sources of pollution were induced also by mining drainage, which led to the expansion of an aeration zone within carbonate rocks which are reach with metal's sulphides (mostly pyrite, marcasite, galena and sphalerite). Development of a thick aeration zone caused significant changes in red-ox conditions and oxidizing of those sulphides. In this process large amounts of acid solutions were created, which were then buffered in contact with carbonate rocks. As a result, highly soluble hydroxy-sulphates were produced. High concentrations of SO₄^2- (up to 20 g/L), Ca²⁺ (up to 0,7 g/L) and Mg²⁺ (up to 5 g/L) appeared in groundwater, especially in the inflow to the mining excavations.

Biography: Adam POSTAWA earned his PhD and DSc at AGH University. Since 2014 he is a Head of Department of Hydrogeology and Engineering Geology, and since 2016 a Deputy Dean of Faculty of Geology, Geophysics and Environmental protection, AGH University. He authored or co-authored over 70 research papers and books. During his career he participated in numerous national and international projects i.e.: BASELINE - Natural Baseline Quality of European Aquifers; A Basis for Aquifer Management, BRIDGE – Background cRiteria for the Identification of Groundwater thrEsholds, COST Action 637 – METEAU. Metals and Related Substances in Drinking Water, GENESIS - Groundwater and dependent Ecosystems: New Scientific basis on climate change and land-use impacts for the update of the EU Groundwater Directive.

From the beginning of his research carrier he has been focusing on water quality, methodology of water sampling and monitoring, water protection in industrial and post-industrial areas, including regions of extensive mining, hydrogeological parameters of various rocks forming aquifers and aquitards. For the last 12 years he has been working on quality of water intended for human consumption, focussing on metals and related substances.