Potential Repository Research Articles

Modelling groundwater contamination above a potential nuclear waste repository in the Columbia River Basalt, USA

Potential groundwater contamination above the one-time candidate repository for high-level nuclear waste in the Columbia River Basalt (CRB), USA, is evaluated in a flow-transport model with 260,895 elements for a period of 1 million years. The hydrogeologic database originates from the Basalt Waste Isolation Project, which ended in 1987, giving way to the Yucca Mountain project. The CRB data have been scanned recently with the object of finding a storage site for natural gas and a sequestration site for CO2. However, the impact on the nuclear issue in the USA or other countries with similar large flood-basalt provinces has never been evaluated since the suspension of the project. The peak radioactive dose predicted for a potential repository in the CRB is at least eight orders of magnitude lower than the US generic regulatory limit (0.15 mS/a) even for the most pessimistic scenario.

The Geon 14 arc-related mafic rocks from the central Grenville Province

The late Paleoproterozoic to Mesoproterozoic (ca. 1.7–1.2 Ga) evolution of the active southeastern margin of Laurentia terminated with the Grenvillian continental collision and the development of a large, hot, long-duration orogen at ca. 1.09–0.98 Ga. As a result, much of the hinterland of the Grenville Province consists of Paleoproterozoic and Mesoproterozoic rocks, mostly preserved as an imbricate stack of high-grade gneisses, that represent a potential repository of active-margin processes. This study presents geochronologic, geochemical, and isotopic analyses of two granulite-facies suites of ca. 1.45–1.40 Ga mafic tholeiites from the Canyon domain (Manicouagan area, central Grenville Province). One suite consists of 1439 +76/–68 Ma high-FeTi mafic sills with εNd values of –0.4 (TDM 2.57–2.72 Ga), indicate derivation from variably depleted to enriched MORB-type mantle sources, probably in an extensional back-arc setting, before intrusion in a ca. 1.5 Ga supracrustal metasedimentary sequence. The other, previously dated, 1410 ± 16 Ma Mafic to intermediate unit exhibits εNd values of 0.0 to +0.9 (TDM 2.02–2.25 Ga), and variably enriched MORB to arc geochemical signatures, for which formation in a transitional back-arc to arc setting is suggested. Integrated with published information, the new data support a model of a long-lived continental-margin arc and intermittent back-arc development on southeast Laurentia during the mid-Mesoproterozoic (ca. 1.5–1.4 Ga), in which repeated short periods of extension and crustal thinning in the back-arc or intra-arc regions were followed by compression and crustal thickening.

Mining Mobility Patterns from Geotagged Photos Through Semantic Trajectory Clustering

ABSTRACTIncreasing geotagged social media data has become a potential repository used to find common trajectory patterns. Various spatial trajectory behaviors have been studied in previous work. In this paper, we extract common trajectory patterns on semantic level. We enrich trajectories with additional contextual semantic annotations and propose a density-based method to find semantic common trajectory patterns with a novel similarity measure method. Real geotagged photo data are used in our experiments. Experimental results demonstrate that our methods are able to generate semantic common trajectory patterns.

English

Although intense research has gone into the exploration of various Combretaceae species towards the discovery of therapeutic relevant compounds, their endophytes have never been explored as potential repositories of alternative sources of novel and medically beneficial equivalents. In the present study, five bacterial endophytes (Lysinibacillus, Staphylococcus, Enterobacter, Pseudomonas and Bacillus species) were isolated from different parts (hard stem, leaves and soft stem) of Combretum molle and identified to species level using morphological data and sequencing of the 16S rRNA. Four of the five endophytes showed varying degrees of antimicrobial characteristics against Bacillus cereus, Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa. Key words: Bacterial endophytes, bioactive compounds, Combretum molle, phylogenetic analysis, medicinal plant.

A force-matching Stillinger-Weber potential for MoS2: Parameterization and Fisher information theory based sensitivity analysis

Two-dimensional molybdenum disulfide (MoS2) is a promising material for the next generation of switchable transistors and photodetectors. In order to perform large-scale molecular simulations of the mechanical and thermal behavior of MoS2-based devices, an accurate interatomic potential is required. To this end, we have developed a Stillinger-Weber potential for monolayer MoS2. The potential parameters are optimized to reproduce the geometry (bond lengths and bond angles) of MoS2 in its equilibrium state and to match as closely as possible the forces acting on the atoms along a dynamical trajectory obtained from ab initio molecular dynamics. Verification calculations indicate that the new potential accurately predicts important material properties including the strain dependence of the cohesive energy, the elastic constants, and the linear thermal expansion coefficient. The uncertainty in the potential parameters is determined using a Fisher information theory analysis. It is found that the parameters are fully identified, and none are redundant. In addition, the Fisher information matrix provides uncertainty bounds for predictions of the potential for new properties. As an example, bounds on the average vibrational thickness of a MoS2 monolayer at finite temperature are computed and found to be consistent with the results from a molecular dynamics simulation. The new potential is available through the OpenKIM interatomic potential repository at https://openkim.org/cite/MO_201919462778_000.

Mobilization and agglomeration of uraninite nanoparticles: A nano-mineralogical study of samples from the Matoush Uranium ore deposit

The occurrence of uraninite nanoparticles in the alteration zones of uranium ore deposits suggests potential mobilization of U(IV) under reducing conditions, which is important for understanding the mobility of uranium in contaminated sites and potential repositories for nuclear waste. This study investigates the occurrence of uraninite nanoparticles in the outer alteration zone of the Matoush uranium ore deposit, Quebec, Canada. Selected samples with finely disseminated uraninite from the outer alteration zone of the deposit are examined by X-ray fluorescence spectroscopy, scanning electron microscopy, and high-resolution transmission electron microscopy on specimens prepared using the focused ion beam milling technique. Uraninite nanoparticles occur as single particles, in clusters, and in larger aggregates in close association with the Cr-rich phases chromceladonite (Cr-rich mica), ideally KMgCr3+(Si4O10)(OH)2, eskolaite, ideally Cr23+O3, bracewellite, Cr3+OOH, and an amorphous Cr-rich oxide matrix as well as with fluorapatite and galena. Nanoparticles on the surface and in the outer rim of single uraninite crystals indicate the growth of larger uraninite crystals via crystallization through particle attachment and Oswald ripening. The flow texture of the uraninite nanoparticles in the amorphous Cr-rich oxide matrix, their aggregation on the surface of nanocrystals of bracewellite, the absence of products of a redox reaction involving U(VI) and Fe(II), and the occurrence of amorphous Fe-depleted alteration layers between uraninite and eskolaite, and uraninite and Cr-rich mica indicate that the uraninite nanoparticles have been mobilized under reducing conditions (leaching of Fe2+ from the alteration layer) at low T (amorphous character of the alteration layer) after the main mineralization event from the center of the mineralization to the outer parts of the Matoush dike complex. These results indicate that fluids can mobilize U(IV) under reducing conditions in the form of uraninite nanoparticles albeit over limited distances. The potential mobilization of these nanoparticles may also explain the occurrence of proximal mineralized zones in U-ore deposits that lack common products resulting from the reduction of U(VI) by Fe2+ (e.g., hematite and other Fe3+-phases).

Probabilistic estimation of long-term volcanic hazard under evolving tectonic conditions in a 1 Ma timeframe

Risk assessments in relation to the siting of potential deep geological repositories for radioactive wastes demand the estimation of long-term tectonic hazards such as volcanicity and rock deformation. Owing to their tectonic situation, such evaluations concern many industrial regions around the world. For sites near volcanically active regions, a prevailing source of uncertainty is related to volcanic hazard. For specific situations, in particular in relation to geological repository siting, the requirements for the assessment of volcanic and tectonic hazards have to be expanded to 1millionyears. At such time scales, tectonic changes are likely to influence volcanic hazard and therefore a particular stochastic model needs to be developed for the estimation of volcanic hazard. The concepts and theoretical basis of the proposed model are given and a methodological illustration is provided using data from the Tohoku region of Japan.

Algae as potential repository of anti cancerous natural compounds

<p>Algae constitute a promising source of novel compounds with potential as human therapeutic agents. In particular, algae have been considered as a potential source of new bio-active compound. Algae possess several biological activities, including anticancer activity. This review provides a comprehensive report on the several genera of algae belonging to Chlorophyceae, Pheophyceae and Rhodophyceae having anti-proliferative, apoptotic, anti angiogenic as well as cytotoxic efficacy and their mode of action <em>in vitro</em> as well as <em>in vivo</em> condition. Algae are extensively used as functional foods and medicinal herbs, and have a long history of use in Asian countries. Many algae have been used for the treatment of cancer, many crude or partially purified polysaccharides from various brown, green, and red algae have been tested for their antitumor activities. Relevant information was collected from scientific journals, books, and reports via library and electronic search using Medline, Pubmed, Science Direct, and Scopus. The different extracts with some other solvent shows a huge anti-proliferative action on different cancer as well as on different leukemia cell lines. Here we focus on several bioactive compounds that have been derived as well as characterized from different genera of algae and there mechanism of inhibiting cancer cell growth. Considering the ability of the golden treasure present in algae to act against different cancers, this review highlights the potential use of algae as anticancer agents.</p>

Reactive transport in the complex heterogeneous alluvial aquifer of Fortymile Wash, Nevada

Yucca Mountain, Nevada, had been extensively investigated as a potential deep geologic repository for storing high-level nuclear wastes. Previous field investigations of stratified alluvial aquifer downstream of the site revealed that there is a hierarchy of sedimentary facies types. There is a corresponding log conductivity and reactive surface area subpopulations within each facies at each scale of sedimentary architecture. Here we use a Lagrangian-based transport model in order to analyze radionuclide dispersion in the saturated alluvium of Fortymile Wash, Nevada. First, we validate the Lagrangian model using high-resolution flow and reactive transport simulations. Then, we used the validated model to investigate how each scale of sedimentary architecture may affect long-term radionuclide transport at Yucca Mountain. Results show that the reactive solute dispersion developed by the Lagrangian model matches the ensemble average of numerical simulations well. The link between the alluvium spatial variability and reactive solute dispersion at different spatiotemporal scales is demonstrated using the Lagrangian model. The longitudinal dispersivity of the reactive plume can be on the order of hundreds to thousands of meters, and it may not reach its asymptotic value even after 10,000 years of travel time and 2–3 km of travel distance.

Volcanic Sulfides and Outgassing

Sulfides are a major potential repository for magmatic metals and sulfur. In relatively reduced magmas, there may be a dynamic interplay between sulfide liquids and magma degassing as magmas ascend/erupt. Sulfide-bubble aggregates may segregate to shallow levels. Exsolved fluids may oxidize sulfides to produce SO 2 gas and metals, which can vent to the atmosphere with chalcophile metal ratios reflecting those in their parent sulfide liquids. Sulfide breakdown and/or sequestration timing and balance define the role of sulfides in both ore formation and the environmental impacts of volcanic eruptions, including during the evolution of large igneous provinces, which are key periods of heightened volcanism during Earth history.

Geologic environments for nuclear waste repositories

High-level radioactive waste (HLW) results from spent reactor fuel and reprocessed nuclear material. Since 1957 the scientific consensus is that deep geologic disposal constitutes the safest means for isolating HLW for long timescales. Nuclear power is becoming significant for the Arab Gulf countries as a way to diversify energy sources and drive economic developments. Hence, it is of interest to the UAE to examine the geologic environments currently considered internationally to guide site selection. Sweden and Finland are proceeding with deep underground repositories mined in bedrock at depths of 500m, and 400m, respectively. Equally, Canada’s proposals are deep burial in the plutonic rock masses of the Canadian Shield. Denmark and Switzerland are considering disposal of their relative small quantities of HLW into crystalline basement rocks through boreholes at depths of 5,000m. In USA, the potential repository at Yucca Mountain, Nevada lies at a depth of 300m in unsaturated layers of welded volcanic tuffs. Disposal of low and intermediate-level radioactive wastes, as well as the German HLW repository favour structurally-sound layered salt stata and domes. Our article provides a comprehensive review of the current concepts regarding HLW disposal together with some preliminary analysis of potentially appropriate geologic environments in the UAE.

Urban sacred natural sites – a call for research

Urban sacred natural sites are not well documented or understood as potential repositories of biological diversity or as critical components of local and indigenous tradition and cultural patrimony in urban areas. Virtually all research and activity on sacred natural sites thus far has focused on sites in non-urban areas, and most interest in sacred sites in urban areas has been on human-built heritage and structures. Minimal attention has been given to sacred natural sites that are in urban areas. These urban sacred natural sites may be connected to mainstream religions, or may exist where cities have developed on indigenous land and associated sacred sites. Given the lack of systematic study of urban sacred natural sites, we recommend further research, including: undertaking inventories; assessing biological features and their possible contributions to conservation; assessing the possible contribution of these sites to wider strategies; examining possible management and protection options; and promoting linkages to relevant global initiatives.

Zika Virus Causes Testis Damage and Leads to Male Infertility in Mice

Zika virus (ZIKV) persists in the semen of male patients, a first for flavivirus infection. Here, we demonstrate that ZIKV can induce inflammation in the testis and epididymidis, but not in the prostate or seminal vesicle, and can lead to damaged testes after 60days post-infection in mice. ZIKV induces innate immune responses in Leydig, Sertoli, and epididymal epithelial cells, resulting in the production of pro-inflammatory cytokines/chemokines. However, ZIKV does not induce a rapid and abundant cytokine production in peritubular cell and spermatogonia, suggesting that these cells are vulnerable for ZIKV infection and could be the potential repositories for ZIKV. Our study demonstrates a correlation between ZIKV and testis infection/damage and suggests that ZIKV infection, under certain circumstances, can eventually lead to male infertility.

Gypsum solubility under pressure conditions relevant to CO2 geological storage

Deep saline aquifers are among the preferred potential repositories for carbon dioxide Geological Storage (CGS). Modeling the interaction of the injected CO2 with the brine is essential for proper planning of CGS, including avoidance of local precipitation of minerals such as sulfates which may clog the injection borehole and decrease the injectivity of the surrounding rock mass. In the present study gypsum solubility at various molal concentrations of dissolved CO2 at pressures of up to 100bar was investigated. A series of semi-batch experiments was performed in a novel flow-through reactor system, designed to withstand high pressures, temperatures and corrosion. Solubilities attained in the experiments match (within a 3% uncertainty) the new PHREEQC v.3′s predictions (Appelo et al., 2014) in which pressure and dissolved CO2 concentrations are two of the new variables. Accordingly, gypsum solubility was found to increase as pressure rises and to decrease as CO2 concentration ascends.

Brassica juncea tested on urban soils moderately contaminated by lead: Origin of contamination and effect of chelates

ABSTRACTUrban garden soils are a potential repository of heavy metal pollution, resulting from either anthropogenic or geogenic origin. The efficiency of phytoextraction was compared on two garden soils with the same texture and topsoil Pb concentration (170 mg kg−1) but not the same origin: one geogenic, the other anthropogenic. Two varieties of Brassica juncea were tested with citric acid (25 mmol kg−1) or ethylenediaminetetraacetic acid (EDTA, 2.5 mmol kg−1). Geogenic Pb was shown to be two times less available than anthropogenic Pb, as a result of which the phytoextraction efficiency was reduced by 59%. Pb mobility in the soil was solely enhanced with EDTA, which increased the Pb concentration in shoots of B. juncea by between 14 and 26 times in comparison with the control. The highest Pb concentration in shoots still remained low, however (i.e., 45 mg kg−1 dry weight). Regardless of the chelates introduced, B. juncea 426308 accumulated roughly twice as much lead as B. juncea 211000, but only for the anthropogenic contaminated soil. Under these conditions, the amount of Pb accumulated by B. juncea (even when assisted by EDTA) was not high enough to envision achieving soil clean-up within a reasonable time frame.

SYNTHESIS OF GEOCHEMICAL AND FRACTURE MINERAL STUDIES RELEVANT TO A DEEP GEOLOGICAL REPOSITORY FOR NONFUEL WASTES AT CHALK RIVER

As part of a feasibility study under the Nuclear Legacy Liabilities Program, the geochemistry of the crystalline bedrock at the Chalk River Laboratories site has been investigated to examine the suitability of the bedrock to host a potential deep geologic repository, termed a Geologic Waste Management Facility, for the long-term management of intermediate-level radioactive wastes for Canadian Nuclear Laboratories, formerly Atomic Energy of Canada Limited. Characterization of the groundwater and fracture-filling minerals are important considerations in assessing how the geochemical environment would affect the performance and safety of such a facility. Regional groundwater chemistry at the site has evolved over time by groundwater mixing and by rock–water interactions. Collaborative studies with the University of Waterloo and the United States Geological Survey have provided data for whole-rock, fracture minerals, and groundwater isotope systematics. The sampled groundwaters appear in general to be geologi...

Thermal behavior of polyhalite: a high-temperature synchrotron XRD study

As an accessory mineral in marine evaporites, polyhalite, K2MgCa2(SO4)4·2H2O, coexists with halite (NaCl) in salt formations, which have been considered as potential repositories for permanent storage of high-level nuclear wastes. However, because of the heat generated by radioactive decays in the wastes, polyhalite may dehydrate, and the released water will dissolve its neighboring salt, potentially affecting the repository integrity. Thus, studying the thermal behavior of polyhalite is important. In this work, a polyhalite sample containing a small amount of halite was collected from the Salado formation at the WIPP site in Carlsbad, New Mexico. To determine its thermal behavior, in situ high-temperature synchrotron X-ray diffraction was conducted from room temperature to 1066 K with the sample powders sealed in a silica-glass capillary. At about 506 K, polyhalite started to decompose into water vapor, anhydrite (CaSO4) and two langbeinite-type phases, K2Ca x Mg2-x (SO4)3, with different Ca/Mg ratios. XRD peaks of the minor halite disappeared, presumably due to its dissolution by water vapor. With further increasing temperature, the two langbeinite solid solution phases displayed complex variations in crystallinity, composition and their molar ratio and then were combined into the single-phase triple salt, K2CaMg(SO4)3, at ~919 K. Rietveld analyses of the XRD data allowed determination of structural parameters of polyhalite and its decomposed anhydrite and langbeinite phases as a function of temperature. From the results, the thermal expansion coefficients of these phases have been derived, and the structural mechanisms of their thermal behavior been discussed.

Sorption and redox speciation of plutonium at the illite surface under highly saline conditions

Natural groundwater may contain high salt concentrations, such as those occurring at several potential deep geological nuclear waste repository sites. Actinide sorption to clays (e.g. illite) under saline conditions has, however, been rarely studied. Furthermore, both illite surface and ionic strength may affect redox speciation of actinides like plutonium. In the present study, Pu sorption to illite is investigated under anaerobic conditions for 3<pHm (=−log mH+)<10andmNaCl=1.0and3.2 molal (m). Results are compared with previous data for mNaCl=0.1m. According to redox potential measurements and based on Eu(III)-illite sorption data (taken as analogue of Pu(III)), the strong effect of mNaCl on overall Pu uptake observed for pHm<6 is mainly attributed to the presence of Pu(III) and its competition with Na+ for ion exchange sites. For pHm>6, overall Pu uptake is largely insensitive to mNaCl due to the prevalence of strongly adsorbed Pu(IV). By applying appropriate corrections to the activity coefficients of dissolved ions and using the 2-site protolysis non-electrostatic surface complexation and cation exchange (2 SPNE SC/CE) model, experimental data on Pu sorption to illite as a function of pH, Eh and mNaCl can be very well reproduced.

The effect of CO2-enriched brine injection on the mechanical properties of calcite-bearing sandstone

The mechanical and fluid-flow response of subsurface geological reservoirs due to injection of CO2 is of critical importance for the safe management and storage of anthropogenic carbon emissions. Although the time-lapse seismic method has proven to be an effective tool to remotely monitor changes in underground fluid saturations, variations in reservoir properties caused by geochemical interactions can also influence the seismic response. This can lead to ambiguity and uncertainty in monitoring the movement of injected CO2 and hence determination of reservoir seal integrity. Geochemical interactions can also modify the mechanical strength of the reservoir and therefore threaten its integrity. We conducted experiments to assess how the velocity and rock strength of a calcite-bearing sandstone are affected by flooding with CO2 saturated brine. The results indicate that both seismic velocity and rock strength are significantly reduced due to minor calcite dissolution. The implications at the reservoir scale for CO2 storage are twofold. Firstly, modifications in velocity can complicate seismic monitoring operations and lead to interpretation errors. This can be accounted for if shear wave velocity variations are used to detect fluid-rock interactions. Secondly, reduction in rock strength, caused by calcite dissolution, can threaten reservoir and wellbore integrity under stress conditions typically found in potential carbon repositories.

Preliminary geochemical modeling of water–rock–gas interactions controlling CO2 storage in the Badenian Aquifer within Czech Part of Vienna Basin

AbstractPrediction of hydrogeochemical effects of geological CO2sequestration is crucial for planning an industrial or even experimental scale injection of carbon dioxide gas into geological formations. This paper presents a preliminary study of the suitability of saline aquifer associated with a depleted oil field in Czech Part of Vienna Basin, as potential greenhouse gas repository. Two steps of modeling enabled prediction of immediate changes in the aquifer and caprocks impacted by the first stage of CO2injection and the assessment of long-term effects of sequestration. Hydrochemical modeling and experimental tests of rock–water–gas interactions allowed for evaluation of trapping mechanisms and assessment of CO2storage capacity of the formations. In the analyzed aquifer, CO2gas may be locked in mineral form in dolomite and dawsonite, and the calculated trapping capacity reaches 13.22 kgCO2/m3. For the caprock, the only mineral able to trap CO2is dolomite, and trapping capacity equals to 5.07 kgCO2/m3.