Leaching of selected metals from a landfill of the closed down Siersza coal mine in Trzebinia (S Poland)

Landfills of waste generated by coal mining could pose a serious environmental threat if not properly reclaimed. The study focuses on leaching select heavy metals from the waste disposed of by the closed down Siersza hard coal mine in Trzebinia (Silesian- Cracow area). The solid waste samples were analysed with the X-ray fluorescence (XRF) method for Zn, Pb, Cd, Mn and Fe contents. The eluates were obtained by leaching the solid samples with distilled water at the ratio 1:10 and analysed with the atomic absorption spectroscopy (AAS) method. The most prone for leaching were Mn and Zn (78 and 73% of the total contents), the medium prone Pb and Cd (around 50% each), and the least prone Fe (30%). In the western part of the landfill, zinc occurs in unexpectedly high amounts (0.64-3.3 wt.%), which may be related to the presence of slag of unknown provenience. The concentrations of Zn, Pb and Cd (averages in mg∙kg⁻¹: 6727, 2.3 and 10.3, respectively) in the leachates exceed the limits of Polish environmental standards. The landfill should be properly monitored and fully reclaimed.