Das Projekt "Molecular-scale investigations on the reactivity and stability of manganese oxide minerals" wird vom Umweltbundesamt gefördert und von Universite de Lausanne, Institut de Mineralogie et Geochimie durchgeführt. Birnessite minerals (layer-type MnO2) produced by bacteria and fungi participate in important biogeochemical processes in oxic and suboxic environments, particularly nutrient and contaminant metal sorption. Birnessite minerals are among the strongest environmental oxidants, contributing to the decomposition of natural organic matter, the oxidative degradation of complex organic pollutants, and the respiration of metal-reducing bacteria in aquatic and terrestrial environments. Despite the importance of biogenic birnessite, several aspects regarding their reactivity remain poorly understood. We hypothesize that biogenic birnessite minerals are distinct in terms of their sorption reactivity and redox reactivity relative to abiotic birnessite minerals due to their occurrence within a biofilm matrix, their large abundance of vacancy sites, and nano-scale dimensions. The objectives of this project are to determine how metal-organic and organic-mineral interactions modify birnessite reactivity, and to determine how mineral properties and structure modify the stability of birnessite against (photo)reductive dissolution. A fundamental understanding of these processes is essential to the development of biogeochemical models that describe aqueous and surface speciation, reactive transport and environmental toxicity. The results from this research have important implications for attenuation of pollution in natural systems; remediation schemes in engineered systems and water treatment; water resource management and water security; and nutrient cycling in terrestrial and marine ecosystems.
