The role of jarosite group minerals in the attenuation of metals and arsenic in mine drainage system (example from the Pekelská Adit, Czech Republic)

Mineralogy of stream sediments and acid mine drainage water chemistry were investigated in the Pekelsk Adit in Czech Republic.Bulk solid phase composition was determined using total decomposition, X-ray powder diffraction, electron microprobe, X-ray photoelectron spectroscopy, and Mssbauer spectroscopy.Water chemistry at the principal branch is acid (pH < 3.0) with high concentration of dissolved iron and sulfate, but it is close to neutral in the second stream branch and becomes more acidic only after the confluence of both branches.Minerals of alunite group including K-jarosite, plumbojarosite, and hydronium jarosite were identified in the stream sediments of acid branch by combination of complementary instrumental methods.In the acid branch, sediments comprise high contents of As (up to 8,021 ppm) and Pb (up to 4,131 ppm), but contents of Zn are much lower.In contrast, in the neutral branch, there is high content of Zn in sediments (up to 11,667 ppm) linked to goethite, but contents of As and Pb are several orders of magnitude lower.Results confirm that minerals of alunite group can be very efficient in trapping of dissolved contaminants and play crucial role in the natural attenuation of dissolved metals and metalloids in mine drainage waters.