Potential Uranium Migration within the Geochemical Gradient of the Opalinus Clay System at the Mont Terri

Transport properties of potential host rocks for nuclear waste disposal are typically determined in laboratory or in-situ experiments under geochemically controlled and constant conditions. Such a homogeneous assumption is no longer applicable on the host rock scale as can be seen from the pore water profiles of the potential host rock Opalinus Clay at Mont Terri (Switzerland). The embedding aquifers are the hydro-geological boundaries, that established gradients in the 210 m thick low permeable section through diffusive exchange over millions of years. Present-day pore water profiles were confirmed by a data-driven as well as by a conceptual scenario. Based on the modelled profiles, the influence of the geochemical gradient on uranium migration was quantified by comparing the distances after one million years with results of common homogeneous models. Considering the heterogeneous system, uranium migrated up to 24 m farther through the formation depending on the source term position within the gradient and on the partial pressure of carbon dioxide pCO2 of the system. Migration lengths were almost equal for single- and multicomponent diffusion. Differences can predominantly be attributed to changes in the sorption capacity, whereby pCO2 governs how strong uranium migration is affected by the geochemical gradient. Thus, the governing parameters for uranium migration in the Opalinus Clay can be ordered in descending priority: pCO2, geochemical gradients, mineralogical heterogeneity.

Study involving removal of azo dye Direct Orange 34 by adsorption in zeolite–clay system

Recently, dyes have procured a wide range of application in the textile industry. These organic compounds possess toxic agents and act as water pollutants. Such dyes can be extracted by adsorption to prevent water pollution. The present work proposes removal of azo dye Direct Orange 34 from the aqueous solution using mixtures of sodalite zeolite (Si/Al ratio 2.5) and clay (vermiculite in 1.0, 2.5, 5.0 g). The methodology involves a system with different stages of separation, considering specified retention time (72, 48, 24, 12, 6 h) of adsorbate and dye concentrations (100, 50, 25, 10, 5 mg/L). The zeolite–vermiculite mixture has a high potential of dye removal due to extensive surface area and porosity with excellent cation exchange capacity conferring its adsorbent property. High concentrations (50 and 100 mg/L) and longer retention times than 48 h results in 50% removal of dyes, whereas a low concentration level (25, 10, 5 mg/L) increases the removal efficiency (74%). Henceforth, the experiment concluded that the zeolite–clay mixtures are capable of azo dye extraction.

Litterbox—A gnotobiotic Zeolite-Clay System to Investigate Arabidopsis–Microbe Interactions

Plants are colonised by millions of microorganisms representing thousands of species with varying effects on plant growth and health. The microbial communities found on plants are compositionally consistent and their overall positive effect on the plant is well known. However, the effects of individual microbiota members on plant hosts and vice versa, as well as the underlying mechanisms, remain largely unknown. Here, we describe “Litterbox”, a highly controlled system to investigate plant–microbe interactions. Plants were grown gnotobiotically, otherwise sterile, on zeolite-clay, a soil replacement that retains enough moisture to avoid subsequent watering. Litterbox-grown plants resemble greenhouse-grown plants more closely than agar-grown plants and exhibit lower leaf epiphyte densities (106 cfu/g), reflecting natural conditions. A polydimethylsiloxane (PDMS) sheet was used to cover the zeolite, significantly lowering the bacterial load in the zeolite and rhizosphere. This reduced the likelihood of potential systemic responses in leaves induced by microbial rhizosphere colonisation. We present results of example experiments studying the transcriptional responses of leaves to defined microbiota members and the spatial distribution of bacteria on leaves. We anticipate that this versatile and affordable plant growth system will promote microbiota research and help in elucidating plant-microbe interactions and their underlying mechanisms.

The effect of hydrogenation of epoxy resin on the dispersion of organo-clay in the epoxy resin matrix

The hydrogenated diglycidylether of Bisphenol A epoxy resin (HDGEBA)was successfully employed to prepare nanocomposites with a more homogeneous distribution of clay, compared to that of bisphenol A epoxy resin (DGEBA)/clay system. Nanocomposites, with amounts up to 7.5 wt% of Organo-clay, were synthetized by means of “slurry-compounding” method and followed by a curing process with cis-1,2-Cyclohexanedicarboxylic anhydride and Glutaric Anhydride as the curing agent. A combination of X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to characterize the dispersion behavior of organo-clay in epoxy/clay nanocomposites. It was found that, in HDGEBA/clay nanocomposites, organo-clay was uniformly dispersed and even partly exfoliated, whereas, in DGEBA/clay system, large particle aggregates were seen when examined by TEM under lower magnification. Accordingly, the rheology and compatibility experiments were carried out to investigate the interactions within each system. It turned out that, after hydrogenation, HDGEBA was endowed with stronger interactions with organo-clay, thus resulting in the enhanced dispersion behavior, which may generate more chances to be mechanically reinforced by adding inorganic clays.

Litterbox - A gnotobiotic zeolite-clay system to investigate Arabidopsis-microbe interactions

Plants are colonised by millions of microorganisms representing thousands of species with varying effects on plant growth and health. The microbial communities found on plants are compositionally consistent and their overall positive effect on the plant is well known. However, the effects of individual microbiota members on plant hosts and vice versa, as well as the underlying mechanisms remain largely unknown. Here, we describe ‘Litterbox’, a highly controlled system to investigate plant-microbe interactions. Plants were grown gnotobiotically on zeolite-clay, an excellent soil replacement that retains enough moisture to avoid subsequent watering. Plants grown on zeolite phenotypically resemble plants grown under environmental conditions. Further, bacterial densities on leaves in the Litterbox system resembled those in temperate environments. A PDMS sheet was used to cover the zeolite, thereby significantly lowering the bacterial load in the zeolite and rhizosphere. This reduced the likelihood of potential systemic responses in leaves induced by microbial rhizosphere colonisation. We present results of example experiments studying the transcriptional responses of leaves to defined microbiota members and the spatial distribution of bacteria on leaves. We anticipate that this versatile and affordable plant growth system will promote microbiota research and help in elucidating plant-microbe interactions and their underlying mechanisms.