Can argillaceous formations isolate nuclear waste? Insights from isotopic,noble gas,and geochemical profiles

There is considerable interest in the use of thick argillaceous geologic formations to contain nuclear waste. Here, we show that diffusion can be the controlling transport process in these formations and diffusional time scales for δ¹⁸O and δ²H in water, dissolved He, and Cl transport in shale‐dominated aquitards are typically over 10⁶ years, well exceeding the regulatory requirements for isolation in most countries. Our scientific understanding of diffusive solute transport processes through argillaceous formations would benefit from the application of additional isotopic tracers (e.g., using new ⁴He sampling technology), multidimensional diffusive‐dispersive modeling of groundwater flow and diffusive‐dispersive solute transport over long geologic time scales, and an improved understanding of spatial heterogeneity as well as time‐dependent changes in the subsurface conditions and properties of argillaceous formations in response to events such as glaciation. Based on our current isotopic and geochemical understanding of transport, we argue that argillaceous formations can provide favorable long‐term conditions for isolating nuclear wastes.     

We will be known by the tracks we leave behind: Exotic lithic raw materials,mobility and social networking among the Côa Valley foragers (Portugal)

The aim of this study is to establish different socio-cultural models based on lithic raw material sourcing integrated with regional rock art distributions to infer social behaviours within the context of central Iberian Upper Palaeolithic societies. Specifically, we focus on Upper Palaeolithic hunter–gatherer mobility and social interaction in the Côa Valley. This study relies on a knowledge of regional geology and field work to identify the sources of the lithic raw material found at Côa Valley Upper Palaeolithic sites. We expose the context of use and discard of flint, which is naturally absent from the region, and other local materials. From this, we present a GIS based analysis concerning space, time and least-cost paths travelled. This analysis, along with the environmental data available, forms a baseline to evaluate different anthropological models on hunter–gatherer lithic use, mobility, and social networks. We conclude with a three-level model for social interaction, in the context of aggregation activities between different social meta-groups, which involves embedded procurement, long-distance raw material exchange, and symbolic community, reflected in the largest known open-air Upper Palaeolithic rock art concentration.     

Modern and early-middle Holocene shells of the freshwater mollusc Unio, from Çatalhöyük in the Konya Basin, Turkey: preliminary palaeoclimatic implications from molluscan isotope data

Carbon and oxygen isotope ratios in the shells of the freshwater Unio mollusc yield information on the isotopic composition of the water in which the shell was formed, which in turn relates to climatic conditions prevailing during the bivalves’ life span. Here we analysed shells from one modern Unio, from a modern lake shore in Anatolia, and 4 subfossil Unio shells from Çatalhöyük (dated between 7200 BC and 5000 BC, Neolithic and Chalcolithic periods). Sequential carbon and oxygen isotope analysis along the surface of the shells provides information on seasonal or shorter-term variability of lake waters during the lifetime of the organisms. δ¹⁸O values of the modern shell are consistent with it being collected from a dammed portion of the Seyhan River that does not undergo intensive summer evaporation. This is in contrast to many of the surface water bodies in Anatolia which suffer extensive evaporation in the arid summers. δ¹⁸O values of the subfossil shells from the Çatalhöyük middens indicate that the bivalves came from lakes which evaporated extensively during the summer months but were replenished by high winter rainfall, suggesting that the subfossil shells lived in relatively small lakes or ponds. Stable isotope analysis along the growth of freshwater bivalves is one of the few methods for investigating seasonal water fluctuations in the past. These results may alter current interpretations on the environment of Çatalhöyük during the Neolithic, although more work is needed to confirm these initial findings.