Bentonite clay is the primary candidate for buffer material in a deep geological repository for high level nuclear waste in many countries. However, the material is only suitable if the swelling capacity is maintained with respect to changing temperature and humidity, as well as the possible impact of infiltrating fluids and/or microorganisms. Therefore, it is key to investigate possible influences that may change the swelling capacity of bentonite. This dataset was used to analyze the interaction between Wyoming bentonite clay (MX-80) and the bacterial strain Stenotrophomonas bentonitica BII-R7T (DSM 103927) under the influence of solutions of different salinities (NaCl, artificial Opalinus Clay porewater, and deionized water). The swelling capacity of the Na-montmorillonite was examined at temperatures between 27°C and 80°C, and relative humidity ranging from 0% to 80%.
As reverse weathering has been shown to impact long-term changes in atmospheric CO2 levels, it is crucial to develop quantitative tools to reconstruct marine authigenic clay formation. We explored the potential of the beryllium (Be) isotope ratio (10Be/9Be) recorded in marine clay-sized sediment to track neoformation of authigenic clays. The power of such proxy relies on the orders-of-magnitude difference in 10Be/9Be ratios between continental Be and Be dissolved in seawater. On riverine and marine sediments collected along a Chilean margin transect we chemically extracted reactive phases and separated the clay-sized sediment fraction. We compare the riverine and marine 10Be/9Be ratio of this fraction. Moreover, we compare the elemental and mineralogical composition and the Nd and Sr-isotopic composition of these samples. 10Be/9Be ratios increase four-fold from riverine to marine sediment. We attribute this increase to the incorporation of Be high in 10Be/9Be from dissolved biogenic opal, which also serves as a Si-source for the precipitation of marine authigenic clays. 10Be/9Be ratios thus sensitively track reverse-weathering reactions forming marine authigenic clays.