Iron-containing spontaneously precipitated ochreous sediments serve as natural scavengers of various migrating elements and in this way contribute to removal and immobilization of potentially hazardous elements especially from mine drainage outflows. On the other hand, presence of filamentous fungi in their surroundings triggers biotransformation and contributes to the mobility of these elements. Three groups of samples of spontaneously precipitated ochreous sediments from an abandoned antimony mine in Poproč, Slovakia were studied: as-collected, sterilized at 95 °C for 30 min, and exposed to incubation with filamentous fungus Aspergillus niger which is frequently found in soils. Employing chemical analyses have determined the content of Fe, As, Sb, and Zn in the samples as well as their mobilization among the non-dissolved residue, culture medium of the fungus and/or its biomass. Significant degree of biovolatilization of antimony was unveiled. Speciation of iron was performed by 57Fe Mössbauer spectroscopy performed in a wide temperature range 300-4.2 K and external magnetic field of 6 T. Hyperfine interactions between 57Fe nuclei and their electronic shells have revealed superparamagnetic behavior characteristic for small particles. Their blocking temperatures of 46, 53, and 40 K, respectively, indicate a dependence of the size of the particles upon the sample treatment. While sterilization has supported their growth, incubation with fungus has changed their chemical environment and removed mainly bigger particles.

Department of Low Temperature Physics Faculty of Mathematics and Physics Charles University 5 Holešovičkách 2 180 00 Prague Czech Republic

Department of Nuclear Reactors Faculty of Nuclear Sciences and Physical Engineering Czech Technical University Prague 5 Holešovičkách 2 180 00 Prague Czech Republic

Institute of Laboratory Research on Geomaterials Faculty of Natural Sciences Comenius University in Bratislava Ilkovičova 6 842 15 Bratislava Slovakia

Slovak University of Technology in Bratislava Faculty of Electrical Engineering and Information Technology Institute of Nuclear and Physical Engineering Ilkovičova 3 812 19 Bratislava Slovakia

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