Solid-phase distribution and mobilization of iron and manganese from sulfidic mine waste under neutral drainage conditions at Rudabánya mine, Hungary

This study characterizes mine waste near Rudabánya, Hungary (Eastern-Central Europe) to evaluate its potential long-term effects on local stream contamination. Five stream water samples were collected and analyzed to determine their chemical composition. Mineralogical and geochemical analyses of eight mine waste samples were combined with sequential extraction procedures to identify minerals and determine the distribution of metals between these phases. Geochemical modeling was performed to estimate the release of potential contaminants over the next 50 years upon interaction between the waste and rainwater. Results indicate that Fe and Mn contamination are present in the stream. Key minerals in the waste are calcite, dolomite, and siderite, with subordinate amount of pyrite, sphalerite, illite, quartz, barite, and Fe-Mn (oxyhydr)oxides. Most waste samples show elevated Cu, Zn, Pb, Cd, and As concentrations with a significant portion associated with environmentally available fractions and sulfide minerals. Geochemical modeling indicates circumneutral conditions (pH 6.2) in the pore space, with the formation of gypsum and Fe-Mn-Al (oxyhydr)oxides, along with the dissolution of pyrite, illite, and carbonates. The model predicts a consistent release of Fe (<1.2 x 10⁻¹ mg/L) and Mn (<4.0 x 10⁻⁶ mg/L) over the next 50 years, which is expected to maintain water contamination in the area.