Natural ferric ochres that precipitate in streambeds at abandoned mining sites are natural scavengers of various metals and metalloids. Thus, their chemical and structural modification via microbial activity should be considered in evaluation of the risks emerging from probable spread of contamination at mining sites. Our results highlight the role of various aspergilli strains in this process via production of acidic metabolites that affect mobility and bioavailability of coprecipitated contaminants. The Mössbauer analysis revealed subtle structural changes of iron in ochres, while the elemental analysis of non-dissolved residues of ochres that were exposed to filamentous fungi suggest coinciding bioextraction of arsenic and antimony with extensive iron mobilisation. However, the zinc bioextraction by filamentous fungi is less likely dependent on iron leaching from ferric ochres. The strain specific bioextraction efficiency and subsequent bioaccumulation of mobilised metals resulted in distinct tolerance responses among the studied soil fungal strains. However, regardless the burden of bioextracted metal(loid)s on its activity, the Aspergillus niger strain has shown remarkable capability to decrease pH of its environment and, thus, bioextract significant and environmentally relevant amounts of potentially toxic elements from the natural ochres.

Department of Mineral Resources and Energy Engineering and Department of Environment and Energy Jeonbuk National University 567 Baekje daero Deokjin gu Jeonju 54896 Jeonbuk Republic of Korea

Department of Nuclear Reactors Faculty of Nuclear Sciences and Physical Engineering Czech Technical University Prague 5 Holešovičkách 2 18000 Prague Czech Republic

Institute of Experimental Physics Slovak Academy of Sciences Watsonova 47 04001 Košice Slovakia

Institute of Laboratory Research on Geomaterials Faculty of Natural Sciences Comenius University in Bratislava Mlynská dolina 84215 Bratislava Slovakia

Slovak University of Technology Institute of Nuclear and Physical Engineering Ilkovičova 3 81219 Bratislava Slovakia

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