Selenite Distribution in Multicomponent System Consisting of Filamentous Fungus,Humic Acids,Bentonite, and Ferric Oxyhydroxides

Selenite is an environmental toxicant whose mobility is affected in soil by various natural components, including humic acids, clay minerals, amorphous ferric oxyhydroxides FeO_x(OH)_y], and microorganisms. However, interactions of selenite with these components are usually evaluated separately. Therefore, we addressed selenite behavior in multicomponent system in this study with emphasis on its immobilization and fungal accumulation. Our results highlighted significant acidification of culture medium by common soil fungus Aspergillus niger’s production of protons in selenite presence which affected selenium immobilization. While bentonite and humic acids did not enhanced immobilization efficiency significantly, composite of FeO_x(OH)_y/humic acids was extremely successful in selenium immobilization. This was most likely by enhanced redox transformation of selenite into elemental selenium as the contribution of each component was synergistic. Subsequently, selenium bioavailability in culture medium decreased and negatively affected bioaccumulation efficiency by fungus. Our results highlighted the significance of multicomponent systems in more realistic evaluation of selenium mobility and transfer to microorganisms.