Ex and In Situ Reactivity and Sorption of Selenium in Opalinus Clay in the Presence of a Selenium Reducing Microbial Community

79Se is a critical radionuclide concerning the safety of deep geological disposal certain radioactive wastes in clay-rich formations. To study fate selenium oxyanions clayey rocks presence reducing microbial community, situ tests were performed Opalinus Clay at Mont Terri Rock Laboratory (Switzerland). Furthermore, biotic and abiotic batch to assess Se(VI) Se(IV) reactivity and/or stainless steel, order support interpretation tests. Geochemical modeling was applied simulate reduction, sorption solubility, diffusion processes. This shows that activity required transform into more reduced sorbing Se species Clay, while conditions, remains unreactive. On other hand, can be by microorganisms but also sorb clay without microorganisms. In reduction occur with electron donors provided itself. If would active surrounding facility, leached could thus contribute overall retention host rocks.