Scholarly record

APPLICATION OF GEOCHEMICAL MODELING FOR THE IDENTIFICATION OF MAIN PROCESSES AFFECTING CHANGES IN THE QUALITY OF GROUNDWATER IN THE LAZY BLEDOWSKIE WELL FIELD, SOUTHERN POLAND

Andrzej Witkowski

Abstract

Lazy Bledowskie well field located in the area of the Upper Silesia, was established in 1959. It consisted of max. 22 wells abstracting water from the Triassic carbonate aquifer (Olkusz-Zawiercie major aquifer). This aquifer is additionally heavily drained by Zn-Pb ore mines. Due to the decreasing demand for water and the deterioration of its quality, wells were gradually excluded from operation and liquidated. Currently, only 2 wells are exploited, pumping approx. 11500 m3 /d. As a result of the overlapping impact of various factors (changes of the groundwater table related to Zn-Pb ore mining and intensive groundwater abstraction by well fields, impact of industrial areas and landfills, discharges of municipal and industrial sewage, as well as agricultural activity) there was a significant deterioration in the groundwater quality. Elevated values of total hardness, sulphates, manganese, iron, turbidity and occasionally mercury and lead were found. The PHREEQC software was used to identify the ongoing hydrogeochemical processes. The database for geochemical modeling of saturation indices for mineral phases consisted the results of 280 physicochemical analyzes of water from the ?azy B??dowskie well field. The analysis showed that the main processes forming the chemical composition of groundwater are dissolution of carbonates and oxidation of sulphides, and subsequent dissolution of oxidation products. There may also be a dedolomitization process. These processes are intensified as a result of water table fluctuation, and thus changes in the oxidation-reduction conditions.

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