title: Impact of uranium mines closure and abandonment on groundwater quality.
abstract: The aim of the study is to assess the evolving mine water quality of closed uranium mines (abandoned between 1958 and 1992) in the Czech Republic. This paper focuses on the changes in mine water quality over time and spatial variability. In 2010, systematic monitoring of mine water quality was performed at all available locations of previous uranium exploitation. Gravity flow discharges (mine adits, uncontrolled discharges) or shafts (in dynamic state or stagnating) were sampled. Since the quality of mine water results from multiple conditions-geology, type of sample, sampling depth, time since mine flooding, an assessment of mine water quality evolution was done taking into account all these conditions. Multivariate analyses were applied in order to identify the groups of samples based on their similarity. Evaluation of hydrogeochemical equilibrium and evolution of mine waters was done using the Geochemist's Workbench and PHREEQC software. The sampling proved that uranium concentrations in mine waters did not predominantly exceed 0.45 mg/L. In case of discharges from old adits abandoned more than 40 years ago, uranium concentrations were below the MCL of US Environmental Protection Agency for uranium in drinking water (0.03 mg/L). Higher concentrations, up to 1.23 mg/L of U, were found only at active dewatered mines. Activity concentration of 226Ra varied from 0.03 up to 1.85 Bq/L except for two sites with increased background values due to rock formation (granites). Radium has a typically increasing trend after mine abandonment with a large variability. Concerning metals in mine water, Al, Co and Ni exceeded legislative limits on two sites with low pH waters. The mine water quality changes with a focus on uranium mobility were described from recently dewatered mines to shafts with water level maintained in order to prevent outflows to surface water and finally to stagnating shafts and discharges of mine water from old adits. The results were in good agreement with published experience on mine water stratification, its disturbance by pumping or natural water decant and the "first flush" phenomenon after mine flooding.
authors.affiliation: Institute of Clean Technologies for Mining and Utilization of Raw Materials for Energy Use, VSB-Technical University of Ostrava, 17, Listopadu 15, 708 33, Ostrava, Czech Republic, nada.rapantova@vsb.cz.
authors.forename: Nada
authors.initials: N
authors.lastname: Rapantova
authors.forename: Monika
authors.initials: M
authors.lastname: Licbinska
authors.forename: Ondrej
authors.initials: O
authors.lastname: Babka
authors.forename: Arnost
authors.initials: A
authors.lastname: Grmela
authors.forename: Pavel
authors.initials: P
authors.lastname: Pospisil
mesh_terms: D018153:Czech Republic; D004777:Environment; D060587:Groundwater / Q000737:chemistry*; D008670:Metals / Q000032:analysis; D008906:Mining; D011883:Radium / Q000032:analysis*; D014501:Uranium / Q000032:analysis*; D014873:Water Pollutants / Q000032:analysis*; D014876:Water Pollution / Q000706:statistics & numerical data; D060753:Water Quality
chemical_list: D008670:Metals; D014873:Water Pollutants; D014501:Uranium; D011883:Radium