Experimental investigation of carbon dioxide trapping due to capillary retention in saline aquifers

Capillary trapping is a physical mechanism by which carbon dioxide (CO₂) is naturally immobilized in the pore spaces of aquifer rocks during geologic carbon sequestration operations, and thus a key aspect of estimating geologic storage potential. Here, we studied capillary trapping of supercritical carbon dioxide (scCO₂), and the effect of initial scCO₂ saturation and flow rate on the storage/trapping potential of Berea sandstone. We performed two‐phase, scCO₂‐brine displacements in two samples, each subject to four sequential drainage–imbibition core‐flooding cycles to quantify end‐point saturations of scCO₂ with the aid of micro‐ and macro‐computed tomography imaging. From these experiments, we found that between 51% and 75% of the initial CO₂ injected can be left behind after the brine injection. We also observed that the initial scCO₂ saturation influenced the residual scCO₂ saturation to a greater extent than the rate of brine injection under the experimental conditions examined. In spite of differences in the experimental conditions tested, as well as those reported in the literature, initial and residual saturations were found to follow a consistent relationship.     

Power to the people: when culture works as a social catalyst in urban regeneration processes (and when it does not)

This article focuses upon the relationship between culture, urban regeneration schemes, and their impact on socio-cognitive assets – namely, social and human capital. It examines three major urban regeneration projects in the districts of Saint Michel (Montreal, Canada), Auburn (Sydney, Australia) and Bicocca (Milan, Italy), where culture has been invoked as a main transformational driver at the economic and socio-environmental levels, but with different approaches and results. Through comparative analysis, we develop a more general reflection on the social impact of culture-led urban transformation processes, questioning the actual role of cultural initiatives – particularly those related to the creation of new cultural facilities and the programming of big cultural flagship events – and participation as a means to improve the local social milieu. We find that a key role for social efficacy is played by projects’ capacity to elicit the commitment of residents through inclusive cultural participation, as opposed to instrumental top-down initiatives mainly addressing city and neighbourhood branding and real estate marketing purposes.     

Recovering social and cultural dynamics from plaster floors: chemical analyses at ancient Chunchucmil,Yucatan, Mexico

Phosphate analysis and trace metals analysis were used to determine activities that took place on plaster floors in domestic contexts at the ancient Maya site of Chunchucmil, Yucatan. Research on activities and the use of space contributes to an understanding of social relations within household groups as well as unforeseen patterns that structure refuse discard. The floors analyzed in this paper pertain to three structures in two neighboring houselots dating to the Early Classic (300–600 A.D.) period. Data from the chemical analyses were utilized in conjunction with associated architectural features and artifacts found on the floors. These three lines of information were interpreted with the help of models developed from ethnographic and ethnoarchaeological research. The results demonstrated functional differentiation of rooms within elaborate residences and suggested that front rooms were used to host visitors. The results also suggested that different types of debris were managed differently. Finally, chemical analyses suggest that non-elite Maya occasionally enacted rituals often restricted to elites.     

Dangerous Places and Wild Spaces: Creating Meaning with Materials and Space at Contemporary Maya Shrines on El Duende Mountain

Ethnoarchaeological observations at Maya shrines on a sacred mountain suggest that three potent material strategies imbue ritual practices with different social meanings: 1) the use of different types of materials as offerings in various rites, 2) the ways in which the physical conditions of an offering are altered during deposition, and 3) the choice of location where the offering is deposited within the site relative to a ceremonial focal point. Through these strategies, individuals creatively negotiate limited access to material resources and assign diverse meanings to the material culture, practices, and places of ritual. Materials that represent commoners' rituals may primarily consist of quotidian items that are transformed in meaning by how and where they are deposited into an archaeological context.     

Gas breakthrough experiments on fine-grained sedimentary rocks

The capillary sealing efficiency of fine‐grained sedimentary rocks has been investigated by gas breakthrough experiments on fully water saturated claystones and siltstones (Boom Clay from Belgium, Opalinus Clay from Switzerland and Tertiary mudstone from offshore Norway) of different lithological compositions. Sand contents of the samples were consistently below 12%, major clay minerals were illite and smectite. Porosities determined by mercury injection lay between 10 and 30% while specific surface areas determined by nitrogen adsorption (BET method) ranged from 20 to 48 m² g ^{? 1}. Total organic carbon contents were below 2%. Prior to the gas breakthrough experiments the absolute (single phase) permeability (k_abs) of the samples was determined by steady state flow tests with water or NaCl brine. The k_abs values ranged between 3 and 550 nDarcy (3 × 10^?21 and 5.5 × 10^?19 m²). The maximum effective permeability to the gas‐phase (k_eff) measured after gas breakthrough on initially water‐saturated samples extended from 0.01 nDarcy (1 × 10^?23 m²) up to 1100 nDarcy (1.1 × 10^?18 m²). The residual differential pressures after re‐imbibition of the water phase, referred to as the ‘minimum capillary displacement pressures’ (P_d), ranged from 0.06 to 6.7 MPa. During the re‐imbibition process the effective permeability to the gas phase decreases with decreasing differential pressure. The recorded permeability/pressure data were used to derive the pore size distribution (mostly between 8 and 60 nm) and the transport porosity of the conducting pore system (10^‐5–10^‐2%). Correlations could be established between (i) absolute permeability coefficients and the maximum effective permeability coefficients and (ii) effective or absolute permeability coefficients and capillary sealing efficiency. No correlation was found between the capillary displacement pressures determined from gas breakthrough experiments and those derived theoretically by mercury injection.     

Capillary Active Interior Insulation Systems for Wall Retrofitting: A More Nuanced Story

To thermally upgrade exterior masonry walls, interior insulation is often the only possible retrofitting technique, especially when dealing with historic buildings. Unfortunately, it is also the riskiest post-insulation technique, as frost damage, interstitial condensation, and other damage patterns might be induced. To diminish those risks, nowadays so-called capillary active interior insulation systems are often promoted. These systems aim a minimal reduction of the inward drying potential, while interstitial condensation is buffered.

Currently, several capillary active systems are on sale. These different types have, however, widely varying properties. In this article, a closer look at the hygrothermal properties and the working principle of a number of “capillary active” interior insulation systems is made. The spread in capillary absorption coefficients and the vapor diffusion resistances of the different systems is discussed and their influence is illustrated. Based on all this, a more nuanced view on capillary active insulation systems is pursued.

Abbreviations: AC: aerated concrete; CaSi: calcium silicate; GM: glue mortar; GB: gypsum board; HAMFEM: Heat Air and Moisture Finite Element Method; MW: mineral wool; PE: polyethylene; PIR: polyisocyanurate; PUR: polyurethane; VIP: vacuum insulation panel; WFB: wood fiber board; XPS: extruded polystyrene; sd_dry: dry vapor diffusion resistance factor; µ_dry: dry vapor diffusion resistance     

Investigating archaeological site formation processes on the battleship USS Arizona using finite element analysis

Scientists from the National Institute of Standards and Technology (NIST) worked in a collaborative partnership with archaeologists from the National Park Service's (NPS) Submerged Resources Center (SRC) to develop a finite element model (FEM) of the battleship USS Arizona. An FEM is a computer-based engineering model that calculates theoretical stresses, propagation of force, and shape changes to a structure under loads using thousands or even millions of individual elements whose individual responses are well understood. NIST researchers created an FEM of an 80 ft. (25 m) midships section of the Arizona site to analyze archaeological site formation processes on the sunken battleship, in particular to determine the current condition of the wreck and predict its future strength and structural integrity as it continues to corrode. The NIST's FEM study is one aspect of a larger project under the direction of the NPS, the USS Arizona Preservation Project, whose goal is to determine the nature and rate of corrosion affecting USS Arizona, and to model its long-term structural deterioration. The FEM incorporates findings from other key components of the USS Arizona Preservation Project, such as steel hull corrosion rates, structural surveys of the vessel, sediment compaction studies, and analysis of the concretion that covers the ship's hull, into a single tool that is being used to predict how the wreck will degrade in the future.     

Phytolith evidence for hearths and beds in the late Mousterian occupations of Esquilleu cave (Cantabria,Spain)

Esquilleu cave site has provided a moderately well preserved archaeological cave deposit from the Late Pleistocene in the Cantabrian area. Phytolith quantification, identification and determination of the refractive index have been carried out, together with FTIR analyses, from sediment samples collected in the profile. The comparison of the data obtained with the previous micromorphological results allows us to make inferences about the site formation processes and the Neanderthals use of the cave. Phytolith results show the presence of grass leaves nearby the hearth suggesting the repetitive existence of a bedding zone on the same area. Neanderthal behavioral patterns should be revised on the light of high resolution analyses, since diagenetic processes can obscure the existence of differentiated activity areas in the site.     

Sedimentological and archaeological fabrics in Palaeolithic levels of the South-Eastern Pyrenees: Cova Gran and Roca dels Bous Sites (Lleida, Spain)

The comparative study of sedimentary fabrics in relation to archaeological fabrics in various levels of the sites of Cova Gran de Santa Linya (Middle and Early Upper Palaeolithic) and the Roca dels Bous (Middle Palaeolithic) has made it possible to analyse the formation dynamics of the deposits and determine the extent of disturbance of the archaeological levels by natural processes. To achieve this, diagrams and two- and three-dimensional indices were calculated from the azimuth and dip angle of natural clasts and artefacts. The results indicate that the sedimentary levels were formed mainly by planar fabric shape gravitational processes (low depositional angles), which differ notably from the archaeological fabrics they contain, characterised by a greater degree of isotropy. This difference in the fabrics would reflect human activity and indicates that the archaeological levels both in Cova Gran and Roca dels Bous have not been subject to significant natural modifications, and are preserved in situ.     

Pre-Clovis in Texas? A critical assessment of the “Buttermilk Creek Complex”

Lithic artifacts from the lowest strata of the Debra L. Friedkin site, located on Buttermilk Creek in central Texas, have been interpreted as an undisturbed pre-Clovis assemblage (Waters et al., 2011a). Stone tools and debitage were recovered from sediments stratified just below diagnostic Clovis artifacts and dated by OSL to between 13.2 and >15.5 cal kya. Invoking commonly observed cultural and natural site formation processes, we offer an alternative explanation of the “Buttermilk Creek Complex” as a Clovis assemblage in secondary association with the dated sediments.