Temporal fluctuations in water contamination from abandoned pyrite Wieściszowice mine (Western Sudetes, Poland).

Production of acid mine drainage may occur during mining operations and may continue for many years after closure. In some cases, especially when host rock is capable of reacting with acidic drainage, metal concentrations may decrease over time and distance. Seasonal variations in water flow rate also play an important role in metals concentration both in surface and groundwater. The present study evaluates the contamination of an abandoned pyrite mining area (Wieściszowice, SW Poland) and the temporal variation of the water contamination in selected locations of 2 sampling campaigns (2000 and 2015). The mining surrounding Rudawy Janowickie Mountains range is well known for the rich mining history and is considered as one of the oldest in Europe. The Wieściszowice pyrite mine was exploited for several hundreds of years and processed Fe and Cu sulfides, and sulfur. This mine was closed in 1925 because of the high competition of pyrites from Spain. Results show clearly that water samples collected in the mining area are mainly Ca-SO4 and acid/high metal, while spring water and surface water samples, representing the local geochemical background, are Ca-HCO3 and neutral-low metal. The analysis of data shows an improvement in water quality from 2000 to 2015 as well as a decreasing of water risk assessment for human use. This improvement can be related to the fact that 2015 was a very dry year, with over 60% less flow than in 2000, leading to less water contamination.