Hydraulic and isotopic data collected from aquifers are routinely used to characterize hydrogeological conditions within sedimentary basins, but similar data from confining units are generally not ...collected despite their ability to provide insights on important water/solute transport controls. We characterized paleogroundwater flow and solute transport mechanisms across 384 m of Cretaceous shale (aquitard) in the Williston Basin, Canada, using high‐resolution depth profiles of water isotopes (δ18O, δ2H). Water samples were also collected from wells installed in the underlying regional sandy aquifer (Mannville Fm; 93 m thick) and from seepage inflows into potash mine shafts (to 825 m below ground). The 1‐D numerical transport modeling of δ18O profiles provided insight into large‐scale/long‐term solute transport in both Cretaceous sediments and the basin. Despite the potential for significant advective migration during glaciations, molecular diffusion appears to be the dominant solute transport mechanism through the aquitard. Simulations suggest average vertical groundwater velocities of <0.05 m/10 ka and an average excess hydraulic head of <10 m; these values are much less than anticipated by successive glaciations. The dominant paleoevent reflected in present‐day profiles is introduction during the Pleistocene of glaciogenic meteoric water to the aquifer underlying the shale, likely along an aquifer outcrop area east of the site or through local vertical conduits. Simulations suggest these recharge events occurred during one or more glacial periods. The isotopic profile over the upper 25 m of Pleistocene till and shale is consistent with glacial deposition and transport processes within these units over the Holocene (past 10 ka).
Key Points
The hydrogeology of the Williston Basin was not static over geologic time.
Groundwater flow was altered by injection of waters during glaciation(s).
The glacial recharge was from the outcrop area or collapse/fault features.
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Background Exercise capacity, which is predictive of all-cause mortality and cardiovascular disease risk, is reduced significantly in patients with non–dialysis-dependent chronic kidney disease. This ...pilot study examined the effect of moderate-intensity exercise training on kidney function and indexes of cardiovascular risk in patients with progressive chronic kidney disease stages 3 to 4. Study Design Single-blind, randomized, controlled, parallel trial. Setting & Participants 20 patients (aged 18-80 years; 17 men) randomly assigned to rehabilitation (n = 10) or usual care (n = 10). Participants were included if they were 18 years or older and had evidence of rate of decline in creatinine-based estimated glomerular filtration rate (eGFRcr ) ≥ 2.9 mL/min/1.73 m2 per year for 12 months preintervention. Patients were excluded if they had unstable medical conditions or had recently started regular exercise. Intervention The rehabilitation group received resistance and aerobic training (3 days per week) for a 12-month period. The usual care group received standard care. Outcomes Kidney function assessed by comparing mean rate of change in eGFRcr (mL/min/1.73 m2 per year) from a 12-month preintervention period against the 12-month intervention period. Pulse wave velocity (PWV), peak oxygen uptake (V o2peak ), and waist circumference assessed at 0, 6, and 12 months. Measurements eGFR assessed using creatinine, cystatin C (eGFRcys ), and a combination of both values (eGFRcr-cys ). Results 18 participants (rehabilitation, 8; usual care, 10) completed the study. A significant mean difference in rate of change in eGFRcr (+7.8 ± 3.0 95% CI, 1.1-13.5 mL/min/1.73 m2 per year; P = 0.02) was observed between the rehabilitation and usual care groups, with the rehabilitation group demonstrating a slower decline. No significant between-group mean differences existed in absolute eGFRcr , eGFRcr-cys , or eGFRcys at 12 months of study intervention. Significant between-group mean differences existed in PWV (−2.30 95% CI, −3.02 to −1.59 m/s), waist circumference (−7.1 ± 12.8 95% CI, −12.4 to −3.2 cm), and V o2peak (5.7 95% CI, 1.34-10.10 mL/kg/min). Change in eGFRcr was correlated inversely with PWV ( r = −0.5; P = 0.04) at 12 months. Limitations Small sample size, inconsistency between primary and secondary measures of kidney function. Conclusions The effect of a 1-year exercise intervention on progression of kidney disease is inconclusive. A larger study with longer follow-up may be necessary.
Selenium (Se) reservoirs in coal waste rock from the Elk Valley, southeastern British Columbia, the location of Canada’s major steelmaking coal mines, were characterized and quantified by analyzing ...samples collected from the parent rock, freshly blasted waste rock (less than 10 days old), and aged waste rock (deposited between 1982 and 2012). Se is present throughout the waste rock dumps at a mean digestible (SeD) concentration of 3.12 mg/kg. Microprobe analyses show that Se is associated with the primary minerals sphalerite, pyrite, barite, and chalcopyrite and secondary Fe oxyhydroxides. Selenium K-edge X-ray absorption near-edge spectroscopy analyses indicate that, on average, 21% of Se is present as selenide (Se2–) in pyrite and sphalerite, 19% of Se is present as selenite (Se4+) in barite, 21% of Se is present as exchangeable Fe oxyhydroxide and clay-adsorbed Se4+, and 39% of Se is present as organoselenium associated with coaly matter. The dominant source minerals for aqueous-phase Se are pyrite and sphalerite. Secondary Fe oxyhydroxide sequesters, on average, 37% of Se released by pyrite oxidation. Measured long-term Se fluxes from a rock drain at the base of a waste dump suggest that at least 20% of Se2–-bearing sulfides were oxidized and released from that dump over the past 30 year period; however, the Se mass lost was not evident in SeD analyses.
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This study aimed to synthesise and interpret stable isotopic data (δ2H and δ18O) from various sources to understand the isotope hydrology around coal mine operations in Elk Valley, B.C., Canada. The ...data, including precipitation, groundwaters, seeps, and mine rock drains, were used to construct a local meteoric water line (LMWL) for the Elk Valley, evaluate the spatiotemporal isotopic composition of its groundwater, and assess mine seepage and mine rock drain discharge. The study revealed a robust LMWL relation (δ2H = 7.4 ± 0.2 · δ18O - 4.3 ± 4.1). The groundwater and seep data indicated a winter season bias and a north-south latitudinal gradient, suggesting rapid near-surface groundwater flow without significant post-precipitation evaporation. Porewater isotope samples from unsaturated mine rock piles (MRPs) showed site-specific evaporation patterns, potentially due to convective air flows or exothermic sulphide oxidation. This research revealed the influence of groundwater and meltwater on rock drain discharge. Based on evaporative mass balance calculations, MRPs seasonally contributed ca. 5 %(December base flow) and 22 % (snowmelt) to drain discharge. The findings underscore the value of stable isotope data collections in the Elk Valley to help better define and quantify the hydrology-hydrogeology, including a better understanding of evaporative conditions in MRPs.This study aimed to synthesise and interpret stable isotopic data (δ2H and δ18O) from various sources to understand the isotope hydrology around coal mine operations in Elk Valley, B.C., Canada. The data, including precipitation, groundwaters, seeps, and mine rock drains, were used to construct a local meteoric water line (LMWL) for the Elk Valley, evaluate the spatiotemporal isotopic composition of its groundwater, and assess mine seepage and mine rock drain discharge. The study revealed a robust LMWL relation (δ2H = 7.4 ± 0.2 · δ18O - 4.3 ± 4.1). The groundwater and seep data indicated a winter season bias and a north-south latitudinal gradient, suggesting rapid near-surface groundwater flow without significant post-precipitation evaporation. Porewater isotope samples from unsaturated mine rock piles (MRPs) showed site-specific evaporation patterns, potentially due to convective air flows or exothermic sulphide oxidation. This research revealed the influence of groundwater and meltwater on rock drain discharge. Based on evaporative mass balance calculations, MRPs seasonally contributed ca. 5 %(December base flow) and 22 % (snowmelt) to drain discharge. The findings underscore the value of stable isotope data collections in the Elk Valley to help better define and quantify the hydrology-hydrogeology, including a better understanding of evaporative conditions in MRPs.
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The mineralogy and evolution of Al and Mg in U mill tailings are poorly understood. Elemental analyses (ICP-MS) of both solid and aqueous phases show that precipitation of large masses of secondary ...Al and Mg mineral phases occurs throughout the raffinate neutralization process (pH 1–11) at the Key Lake U mill, Saskatchewan, Canada. Data from a suite of analytical methods (ICP-MS, EMPA, laboratory- and synchrotron-based XRD, ATR-IR, Raman, TEM, EDX, ED) and equilibrium thermodynamic modeling showed that nanoparticle-sized, spongy, porous, Mg–Al hydrotalcite is the dominant mineralogical control on Al and Mg in the neutralized raffinate (pH ≥ 6.7). The presence of this secondary Mg–Al hydrotalcite in mineral samples of both fresh and 15-year-old tailings indicates that the Mg–Al hydrotalcite is geochemically stable, even after >16 years in the oxic tailings body. Data shows an association between the Mg–Al hydrotalcite and both As and Ni and point to this Mg–Al hydrotalcite exerting a mineralogical control on the solubility of these contaminants.
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Hematite is a thermodynamically stable iron oxide under the aerobic conditions present in most natural surface soils and sediments. Most studies to date have focused on the capacity of hematite to ...adsorb trace metals and metalloids, but structural incorporation of trace metals within hematite is less recognized. This study assessed the incorporation of molybdenum within the structure of hematite during the phase transformation of 2-line ferrihydrite under alkaline conditions (pH ∼10). Extended X-ray absorption fine structure analyses show molybdenum incorporated into hematite, with two Mo-O shells having a coordination number (CN) of 3 and average bond distances of 1.78 ± 0.01 and 2.08 ± 0.02 Å, respectively, as well as two Mo-Fe shells with a CN of 3 and average bond distances of 3.10 ± 0.02 Å and 3.44 ± 0.02 Å, respectively. This observation suggests the tetrahedrally-coordinated Mo in the molybdate that adsorbs onto the 2-line ferrihydrite changes to an octahedrally-coordinated Mo within the hematite with Mo possibly substituting for Fe in the hematite structure. Our findings suggest that molybdenum partitioning (low concentrations) to iron oxides in the environment can occur due to structural incorporation as well as adsorption.
•Incorporation of Mo to hematite structure during transformation of ferrihydrite was investigated.•EXAFS analyses showed that molybdate incorporated into hematite:•Two Mo-O shells having a coordination number (CN) of 3 and average bond distances of 1.78 ± 0.01 Å and 2.08 ± 0.02 Å.•Two Mo-Fe shells with a CN of 3 and average bond distances of 3.10 ± 0.02 Å and 3.44 ± 0.02 Å.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
The Universe is undergoing a late time acceleration. We investigate the idea that this acceleration could be the consequence of gravitational leakage into extra dimensions on cosmological scales ...rather than the result of a non-zero cosmological constant, and consider the ability of future gravitational-wave (GW) siren observations to probe this phenomenon and constrain the parameters of phenomenological models of this gravitational leakage. A gravitational space interferometer such as LISA will observe massive black hole binary (MBHB) merger events at cosmological distances, and will also provide sky localization information that may permit optical and other electromagnetic (EM) surveys to identify an EM counterpart of these events. In theories that include additional non-compact spacetime dimensions, the gravitational leakage intro extra dimensions leads to a reduction in the amplitude of observed gravitational waves and thereby a systematic discrepancy between the distance inferred to such sources from GW and EM observations. We investigate the capability of LISA to probe this modified gravity on large scales, specifically in the Dvali, Gabadadze and Porrati (DGP) model. Additionally, we include a Supernova Ia sample at lower redshift in order to explore the efficacy of this cosmological probe across a range of redshifts. We then use previously published simulated catalogues of cosmologically distant MBHB merger events detectable by LISA, and which are likely to produce an observable EM counterpart. We find that the extent to which LISA will be able to place limits on the number of spacetime dimensions and other cosmological parameters characterising modified gravity will strongly depend on the actual number and redshift distribution of sources, together with the uncertainty on the GW distance measurements. A relatively small number of sources (∼1) and high measurement uncertainties would strongly restrict the ability of LISA to place meaningful constraints on the parameters in cosmological scenarios where gravity is only five-dimensional and modified at scales larger than about ∼4 times the Hubble radius. Conversely, if the number of sources observed amounts to a four-year average of ∼27, then in the most favourable cosmological scenarios LISA has the potential to place meaningful constraints on the cosmological parameters—with a precision of ∼1% on the number of dimensions and ∼7.5% on the scale beyond which gravity is modified, thereby probing the late expansion of the universe up to a redshift of ∼8, i.e. on scales not yet tested by present EM observations.
A method to measure the δ2H and δ18O composition of pore waters in saturated and unsaturated geologic core samples using direct vapour equilibration and laser spectrometry (DVE–LS) was first ...described in 2008, and has since been rapidly adopted. Here, we describe a number of important methodological improvements and limitations encountered in routine application of DVE–LS over several years. Generally, good comparative agreement, as well as accuracy, is obtained between core pore water isotopic data obtained using DVE–LS and that measured on water squeezed from the same core. In complex hydrogeologic settings, high-resolution DVE–LS depth profiles provide greater spatial resolution of isotopic profiles compared to long-screened or nested piezometers. When fluid is used during drilling and coring (e.g. water rotary or wet sonic drill methods), spiking the drill fluid with 2H can be conducted to identify core contamination. DVE–LS analyses yield accurate formational isotopic data for fine-textured core (e.g. clay, shale) samples, but are less effective for cores obtained from saturated permeable (e.g. sand, gravels) geologic media or on chip samples that are easily contaminated by wet rotary drilling fluid. Data obtained from DVE–LS analyses of core samples collected using wet (contamination by drill water) and dry sonic (water loss by heating) methods were also problematic. Accurate DVE–LS results can be obtained on core samples with gravimetric water contents > 5 % by increasing the sample size tested. Inexpensive Ziploc™ gas-sampling bags were determined to be as good as, if not better than, other, more expensive specialty bags. Sample storage in sample bags provides acceptable results for up to 10 days of storage; however, measurable water loss, as well as evaporitic isotopic enrichment, occurs for samples stored for up to 6 months. With appropriate care taken during sample collection and storage, the DVE–LS approach for obtaining high-resolution pore water isotopic data is a promising alternative to study the hydrogeology of saturated and unsaturated sediments. Eliminating analytical interferences from volatile organics remains a challenge.
Understanding the kinematics and triggers of a landslide is central to assessing the risk of a landslide. This understanding can be achieved through a robust instrumentation plan that addresses key ...factors such as meteorological conditions, groundwater conditions, and deformation trends and velocity. High-frequency landslide displacement measurements at multiple locations across a sliding mass allow for the evaluation of the impact of meteorological events in the short and long terms. Installation of a monitoring system that provides reliable and accurate high-frequency displacement data from multiple locations can be expensive, and thus, this approach is not commonly used. Single-frequency differential GNSS (dGNSS) provides a relatively low-cost alternative to achieve long-term monitoring goals at multiple locations within a landslide. Networks of single-frequency Geocube™ dGNSS units were installed at test sites at two slow-moving Canadian landslides: the Ten-mile landslide near Lillooet, BC, and the Chin Coulee landslide near Taber, AB. The Geocube system monitored surficial deformation every 60 s for the duration of the monitoring program (> 500 day) and achieved a precision in direct measurements characterized by a standard deviation of 10.5 mm or less. The quality of the collected data was compared to data provided by a high-end multi-frequency GMX 910 Leica GPS, installed at the Ripley landslide near Ashcroft, BC. The data collected from the Geocube systems revealed that displacement orientations and rates varied within each of the sliding masses. The application of multiple monitoring points provided a relatively low-cost method to evaluate the shape of the sliding shear surface and the causal factors driving movement at each site. A practical evaluation of cost-effective dGNSS systems that provide reliable information as required for enhanced understanding of landslide kinematics and the development of early warning systems is presented in this paper.
The Athabasca Basin, located in northern Saskatchewan, Canada, is a major source of global U and an important economic driver for the province and country. Athabasca Basin U deposits consist of ...uraninite and pitchblende dominated by quartz and aluminosilicates and varying amounts of sulfide and arsenide minerals associated with varying concentrations of As, Se, Mo, Ni, and
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Ra (elements of concern; EOCs). Processing these U ores results in tailings that are often enriched in EOCs. Mill treatment processes are designed to generate tailings that minimize the long-term environmental impact of U tailings, although many challenges exist in reaching this goal. Many studies have contributed to our understanding of the geochemistry of these tailings and EOCs and their potential impact on the surrounding hydrosphere. Using nearly two decades of data from tailings samples, mill sampling campaigns, and laboratory experiments, this review provides a comprehensive analysis of the geochemistry and long-term behavior of U tailings in the Athabasca Basin and develops a geochemical model of the tailings. Results of this review are applicable to tailings generated from other milling operations with comparable acid leaching hydrometallurgical processes. This holistic review also highlights the limitations to our current understanding of U tailings geochemistry.
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