Heating performance of deep borehole heat exchangers (DBHEs) is heavily impacted by its design and operating flow rate. Here, various designs of coaxial DBHEs were numerically simulated and compared for 1 year of continuous operation in a cold sedimentary basin using the FEFLOW software. Factors affecting performance, including: (1) depth, (2) repurposing an oil and gas (O&G) well or drilling a larger one, (3) repurposing options, (4) inner pipe material, made of either vacuum insulated tubing (VIT) or high-density polyethylene and (5) grout with different thermal conductivity were evaluated. Where an O&G well is available, the most cost-efficient option is repurposing, with the best performance obtained from the deepest and largest diameter wells. While VIT inner pipes performed better in some designs, their performance did not compensate for their cost.
Soil fungi, as a major decomposer of organic matter, govern carbon (C) cycle and act as crucial regulators of the soil C and nutrient balance in terrestrial ecosystems. Climate change and parent material alter important environmental conditions that may affect fungal community. However, very little is known about the diversity and community structure of soil fungi along elevation gradients with distinct parent material properties. We investigated the effects of climate and vegetation changes on soil fungal diversity and community structure at two Austrian alpine sites with different bedrock properties (limestone at the Hochschwab site and silicate at the Rauris site), but with similar climatic conditions. At these sites we sampled soils from 0 to 25 cm depth along three elevation gradients ranging from 900 to 2100 m above sea level and examined how the fungal communities vary by using Illumina MiSeq sequencing. Our results show that the fungal community structures at the Hochschwab and the Rauris site were defined by elevation-induced changes in vegetation and associated differences in soil pH. In forest soils, symbiotrophic fungi (mainly belonging to the class Agaricomycetes, phylum Basidiomycota) were dominant at the Hoschwab site, while at the Rauris site the Ascomycota were the most dominant phyla. The change to grass dominated vegetation generally increased the contribution of saprotrophic fungi (mainly belonging to various classes of the phylum Mucoromycota) at both elevational sites. Prevalence of ectomycorrhizal fungi and associated lignolytic enzymes induced soil C loss might explain lower soil organic C stocks at the Rauris site compared to the Hochschwab site. Our results suggest that parent material can modulate fungal communities indirectly via vegetation (e.g., litter quality) adapted to particular soil conditions. Therefore, changes in fungal structural composition might exert important consequences on ecosystem C balances.
This paper presents a novel simulation-based method for fast economic optimization of large hybrid ground source heat pump systems. Rapid evaluation of the objective function is achieved by the joint use of previously developed efficient algorithms, including Delaunay triangulation, successive flux estimation and fast spectral convolution. The resulting objective function is concave and composed only of continuous parameters. The global optimal solution of a problem composed of several dozens of boreholes operating over a 30 year time span is found using the Ant Colony Optimization algorithm for continuous domains, and convergence is achieved in under 12 min of computation time. Results show that optimization is key for proposing a financially viable hybrid ground source heat pump project for large commercial buildings. We also show that proper project financing, such as government guaranteed loans, can significantly contribute towards achieving better economic performance. The proposed approach is fast, convergent, practical, and can help promoters present hybrid GSHP projects under a less risky type of business.
This paper reviews trends in the academic literature on cumulative effects assessment (CEA) of disturbance on forest ecosystems to advance research in the broader context of impact assessments. Disturbance is any distinct spatiotemporal event that disrupts the structure and composition of an ecosystem affecting resource availability. We developed a Python package to automate search term selection, write search strategies, reduce bias and improve the efficient and effective selection of articles from academic databases and grey literature. We identified 148 peer-reviewed literature published between 1986 and 2022 and conducted an inductive and deductive thematic analysis of the results. Our findings revealed that CEA studies are concentrated in the global north, with most publications from authors affiliated with government agencies in the USA and Canada. Methodological and analytical approaches are less interdisciplinary but mainly quantitative and expert-driven, involving modeling the impacts of disturbances on biophysical valued components. Furthermore, the assessment of socioeconomic valued components, including the effects of disturbance on Indigenous wellbeing connected to forests, has received less attention. Even though there is a high preference for regional assessment, challenges with data access, quality, and analysis, especially baseline data over long periods, are hampering effective CEA. Few articles examined CEA – policy/management nexus. Of the few studies, challenges such as the inadequate implementation of CEA mitigation strategies due to policy drawbacks and resource constraints, the high cost of monitoring multiple indicators, and poor connections between scenarios/modeling and management actions were paramount. Future CEA research is needed to broaden our understanding of how multiple disturbance affects forests in the global south and coupled social and ecological systems and their implications for sustainable forest management.
Plant area density (PAD in m²·m⁻³) defines the total one-sided total plant surface area within a given volume. It is a key variable in characterizing exchange processes between the atmosphere and land surface. Terrestrial laser scanning (TLS) provides unprecedented detail of the 3D structure of forest canopies. Yet, signal occlusion and uneven sampling density of the TLS point clouds limit our capacity to characterize the 3D distribution of canopy components. Recent studies have made use of statistical estimators of PAD that are applied to TLS point clouds subdivided into three-dimensional (3D) cubes, or voxels. Computation of such metrics under actual field conditions with point clouds containing several millions of returns is challenging. Moreover, rigorous assessment of the estimated PAD and effects of occlusions in forests remain unclear due to laborious, time-consuming, and inaccurate field measurements. In the present study, we present L-Vox, a software that computes PAD per voxel for TLS scans acquired in forest environments, which is based upon recent development of unbiased estimators derived from maximum likelihood. Two applications are presented. First, the software is evaluated for virtual forest plots, which are detailed 3D models of individual trees with corresponding simulated TLS scans, for which reference data are known. Second, L-Vox is applied to actual scans that were acquired in hardwood and coniferous plots in New Brunswick and Newfoundland, Canada. Both test cases were used to investigate the effects of occlusion and the uneven sampling in estimating PAD. The test cases were also used to assess the influence of voxel size and the number of scans per plot on PAD estimates. Our results showed strong correlations between the estimated PAD profile from L-Vox and simulated PAD for virtual forest plots, with a mean R² = 0.98 and a mean coefficient of variation (CV) = 15.6%. We demonstrated that comparing multi-scan to single scan TLS acquisitions in real forest plots substantially reduced signal occlusion, resulting in an increase up to 50% in PAD values. Effects of voxel size on PAD estimates greatly depended upon the relative size of foliar and woody elements, with an optimal size around 10 cm in coniferous plots. L-Vox proved to be an efficient and accurate tool for computing 3D distributions of PAD from TLS measurements in natural forest environments.
The Cryogenian-Ediacaran transition represents a pivotal geological period in the evolution of global climate, ocean chemistry, and early organisms. The transition is concurrent with the change from Marinoan glacial deposits to overlying cap carbonate/dolomite, which is followed by the appearance of novel animal and algae fossils. Unusual carbon cycling during the deposition of cap carbonate/dolomite is recorded by prominent negative carbonate carbon isotope (δ¹³Ccarb) anomalies. The mechanisms which drove melting of the Marinoan icesheets remain uncertain. To explore the cause of this dramatic climate warming and its effect on oceanic biogeochemical cycles, we measured Hg concentrations and isotopes, along with major and trace elements, of the sedimentary succession across the Cryogenian-Ediacaran boundary at the Jiulongwan and Huajipo sections, South China. Hg concentrations show spikes with a ∼ 2 times increase at the top of the Marinoan Nantuo Formation at both sections, which are likely associated with organic matter drawdown rather than enhanced volcanism as indicated by increased TOC contents and similar Hg isotopic signature as those of background Hg deposition. A conspicuous negative shift in δ²⁰²Hg along with a positive shift in Δ¹⁹⁹Hg are observed in the cap dolomite of the Doushantuo Formation at both sections, which are ascribed to contribution of Hg from anoxic deep water and Hg associated with dissolved organic carbon (Hg-DOC), due to upwelling and oceanic oxygenation after deglaciation. Our Hg data argue against a sudden large igneous province (LIP) event causing Marinoan deglaciation. Results also indicate enhanced upwelling and oceanic oxygenation event during the Cryogenian to Ediacaran transition.
All nine five-needle white pine species (genus Pinus, subgenus Strobus, subsections Strobus and Balfourianae) native to the U.S. and Canada are highly susceptible to white pine blister rust (WPBR), caused by the non-native fungal pathogen Cronartium ribicola. WPBR is present within the geographic range of eight of the nine species in the U.S. including the four species also present in Canada, but has not yet been documented in Mexico. Genetic resistance to WPBR has been documented in eight of the white pine species present in the U.S., with extensive work on foxtail pine (Pinus balfouriana) just recently started. The development of populations of trees with durable genetic resistance, while also retaining genetic diversity and adaptability, is seen as a fundamental step in restoring white pine species. Major gene resistance (MGR) has been documented in four species, and quantitative resistance (QR) is likely present in all species, but at levels ranging from very low to moderately high. Restoration using seed from WPBR resistant parent trees has been underway for several decades for western white pine (P. monticola), sugar pine (P. lambertiana), and eastern white pine (P. strobus), and has begun more recently for whitebark pine (P. albicaulis) and limber pine (P. flexilis). For many of these white pine species, locating additional resistant parents and acquiring more seed will be needed over the ensuing decades. The previous efforts in developing populations of trees with genetic resistance to WPBR has used conventional tree improvement techniques of tree selection and seedling inoculation trials. However, in the future with the continued development of omics resources and tools in white pines, biotechnology has the potential to aid resistance programs. Candidate genes have been identified for host MGR, QR, and disease susceptibility (S) to WPBR, as well as for C. ribicola effectors. Marker-assisted selection (MAS) tools developed from MGR-linked genes would be useful to combine MGR and QR, which should improve the potential durability of resistance. Integration of breeding programs with omics information and tools can help pave a road towards improvement of WPBR resistance through biotechnological approaches such as MAS, and genomic selection (GS), or potentially helping to incorporate unique resistance not currently found in North American five-needle white pines. In the near future, these tools could potentially aid in the initial search for candidate trees which would increase the efficiency of developing WPBR resistant populations, as well as defining the extent and distribution of adaptive genetic variation in the species, which will aid in planning restoration efforts.
Climate is a critical driver in shaping patterns of tree distribution and productivity in Canadian forests. Canada’s climate is changing and, as a result, tree populations may become maladapted to the climate at their current growing locations. In 2020, Ontario updated its tree seed transfer policy to respond to the evolving natural, operational, scientific, and policy environments, including a changing climate. Collaboration among federal and provincial science, operations, and policy staff was essential to update the policy, which involved a custom climate similarity analysis, a related assessment of critical seed transfer distances, various engagement efforts to assess end-user receptivity, and the development of an online interactive tool to allow users to explore seed transfer options under climate change. Here we describe several factors considered during the policy update, major steps in the update process, and highlights of the outcome. The intent of this effort is to support other jurisdictions considering similar changes and to emphasize the need for a changing culture in seed procurement and management.
Global technological advancements drive daily energy consumption, generating additional carbon-induced climate challenges. Modifying process parameters, optimizing design, and employing high-performance working fluids are among the techniques offered by researchers for improving the thermal efficiency of heating and cooling systems. This study investigates the heat transfer enhancement of hybrid "Al2O3-Cu/water" nanofluids flowing in a two-dimensional channel with semicircle ribs. The novelty of this research is in employing semicircle ribs combined with hybrid nanofluids in turbulent flow regimes. A computer modeling approach using a finite volume approach with k-ω shear stress transport turbulence model was used in these simulations. Six cases with varying rib step heights and pitch gaps, with Re numbers ranging from 10,000 to 25,000, were explored for various volume concentrations of hybrid nanofluids Al2O3-Cu/water (0.33%, 0.75%, 1%, and 2%). The simulation results showed that the presence of ribs enhanced the heat transfer in the passage. The Nusselt number increased when the solid volume fraction of "Al2O3-Cu/water" hybrid nanofluids and the Re number increased. The Nu number reached its maximum value at a 2 percent solid volume fraction for a Reynolds number of 25,000. The local pressure coefficient also improved as the Re number and volume concentration of "Al2O3-Cu/water" hybrid nanofluids increased. The creation of recirculation zones after and before each rib was observed in the velocity and temperature contours. A higher number of ribs was also shown to result in a larger number of recirculation zones, increasing the thermal performance. Citation: Togun, H.; Homod, R.Z.; Yaseen, Z.M.; Abed, A.M.; Dhabab, J.M.; Ibrahem, R.K.; Dhahbi, S.; Rashidi, M.M.; Ahmadi, G.; Yaïci, W.; Mahdi, J.M. Efficient Heat Transfer Augmentation in Channels with Semicircle Ribs and Hybrid Al2O3-Cu/ Water Nanofluids. Nanomaterials 2022, 12, 2720. https://doi.
The coastline of the Inuvialuit Settlement Region (ISR) in the Mackenzie –Beaufort region of the western Canadian Arctic is characterized by rapid erosion of ice-bonded sediments with abundant excess ground ice, resulting in widespread thermal and mechanical process interactions in the shore zone. Coastal communities within the ISR are acutely aware of the rapidly eroding coastline and its impacts on infrastructure, subsistence activities, cultural or ancestral sites, and natural habitats. Tuktoyaktuk Island is a large natural barrier protecting the harbour and surrounding community from exposure to waves. It is threatened by coastal erosion, a better understanding of which will inform adaptation strategies. Using historical and recent aerial imagery, high-resolution digital elevation models, cliff geomorphology, stratigraphy, and sedimentology, including ground-ice content, this study documents erosional processes, recession rates, volume losses and sediment delivery since 1947, and projected into the future. Erosion along the northwest-facing (exposed) cliff, primarily by thermo-abrasional undercutting and block failure, has accelerated since 2000 to a mean of 1.8 ± 0.02 m/yr, a 22% increase over the previous 15 years and 17% faster than 1947-2000. Lower recession rates on the harbour side of the island increased more than two-fold. Projection of future shoreline vectors by extrapolation, using the post-2000 accelerated coastal recession rates at 284 transects, points to breaching of this vital natural harbour barrier by 2044, after which rapid realignment is expected to occur as the new inlet evolves. Further acceleration of rates, as seems highly likely, brings the breaching date closer.
Vanadium is currently considered a critical material in the European Union, the U.S.A., and other jurisdictions. The vanadium mine production for 2021 is estimated at more than 120 000 tonnes; however, the market base is expected to grow rapidly due to the increase in the use of vanadium for redox flow batteries. Currently, worldwide , many projects are in the advanced stages of exploration and development. In the longer term, should vanadium cease to be a critical material and the law of supply and demand applies, the marginal mines will be decommissioned, and the best deposits will remain economic. Depending on the prevailing regulations in specific jurisdictions, geological settings, and the most up-to-date metallurgical research results, the main vanadium deposit types that could be considered as potential exploration and development targets are the vanadiferous titanomagnetite deposits, sandstone-hosted uranium-vanadium deposits (Salt Wash category), shale-hosted vanadium deposits, and base metal-related vanadate deposits. However, placer deposits, surficial uranium-vanadium type mineralisation, and the Minas Ragra type patrónite deposits should also be considered. ARTICLE HISTORY
The molecular composition of dissolved organic matter (DOM) is increasingly recognized as fundamentally important to mercury transport and transformations, with numerous approaches undertaken to examine DOM characteristics beyond dissolved organic carbon concentrations. In this study, we use a high-resolution mass spectrometry approach, Fourier-transform ion cyclotron resonance mass spectrometry, to characterize DOM compound classes, DOM aromaticity (AImod), and the nominal oxygenation state of carbon (NOSC) across thirteen small boreal forest streams in central Canada. We then relate the relative abundance of hundreds of different DOM molecules with inorganic mercury and methylmercury (MeHg) concentrations across late spring and fall seasons. The number of significant correlations and the classes of DOM compounds significantly correlating with inorganic mercury and MeHg concentrations differs substantially across seasons and between mercury forms. For inorganic mercury, the abundance of nitrogen and sulfur containing DOM are most often positively correlated (mean ρ = 0.80) in the late spring, whereas during the fall, the abundance of low-oxidized lignins is more important, though with weaker correlations (mean ρ = 0.51). For MeHg, low-oxidized lignins and hydrolysable tannins, likely sourced from conifer throughfall and litter, account for up to 83% of all DOM-MeHg correlations regardless of season. Further network analyses reveal that the strongest and most significant inorganic mercury-DOM correlations are found across a wide range of NOSC values, indicating that DOM involved with the transport of inorganic mercury encompasses a wide range of polarities and thermodynamic stabilities. In contrast, DOM molecules exclusively correlated with MeHg concentrations have more positive NOSC and AImod values, implying the preferential transport of MeHg with more thermodynamically stable and aromatic DOM molecules. DOM molecules significantly correlated with both inorganic mercury and MeHg concentrations are found exclusively in the late spring. Overall, this non-targeted approach may help to inform further targeted investigations, especially as it relates to the underrepresented importance of plant biomolecules in facilitating mercury transport. Graphical abstract
In present research, the effect of building orientation on microstructure, texture and mechanical properties of a low carbon maraging steel processed by selective laser melting (SLM) technique is studied. The microstructural characterization and grain structure observations of the fabricated samples are conducted using electron microscopies and electron backscatter diffraction. It is observed that by altering the building orientation from vertical to horizontal, the morphology of the grains changes from columnar-dendritic to equiaxed. In addition, a higher volume fraction of austenite is retained in the horizontal sample compared with the vertically printed sample due to a faster cooling rate, higher degree of micro-segregation, and smaller prior austenite grains. Consequently, a higher strength and better ductility are achieved in the horizontally printed sample. The Taylor factorshows that different obtained tensile properties are not related to the crystallographic texture but are affected by grain size, retained austenite, and stress concentration conditions.
In this study, the severity of slugging is assessed by predicting maximum slug lengths (MSL) quickly using the random forest (RF) algorithm based on the geometric features of well trajectories for a shale gas field. Severe slugging is one of the critical issues production engineering-wise because it causes operation shut-down. Thus it should be predicted for proactive measurements. A total of 5033 well trajectories were acquired from the northeastern area of British Columbia, Canada. The well trajectories are described using ten geometric features such as X, Y, and Z lengths in the Cartesian coordinate system, inclination, azimuth, and the other five. The 5033 well trajectories are grouped using the k-medoids clustering algorithm. The well trajectories in each group and the groups are compared visually to see if the ten features are representative enough to describe the geometric features of the well trajectories. The ten geometric features of the well trajectories are used as the input for RF, and MSL, which represents the severity of slugging, is used as the output for RF. The output data is simulation results by a pipe flow simulator, OLGA. The trained RF model provides the satisfactory prediction performance of MSL (R values, 0.866 and 0.857 for training and test data, respectively). In the trained RF model, X, Y, and Z lengths have the most significant importance among the ten geometric features. Because it is impractical to simulate all well trajectory scenarios by OLGA, the MSL values are projected onto a 3-dimensional map of which axes are X, Y, and Z lengths to visualize the trend of MSL. The 3-dimensional map showing the relation between MSL and the geometric features of well trajectories can be utilized as a quick reference to avoid severe slugging in designing well trajectories.
In this paper, solvent bubble nucleation and liberation processes in the heavy crude oil−CO2 systems, heavy crude oil−CH4 systems and heavy crude oil−C3H8 systems were experimentally studied and theoretically analyzed. First, two respective series of tests were conducted for different heavy crude oil−solvent systems. The first series included eleven conventional isothermal constant-composition-expansion (CCE) tests and the other series consisted of three new isothermal constant-composition-expansion & compression (CCEC) tests. Second, the amount of the evolved gas (i.e., the dispersed gas and free gas) in each pressure reduction step was determined from the measured CCE test data to study the solvent bubble nucleation process in each heavy crude oil−solvent system. A new quantity named the bubble nucleation index (BNI) was introduced and used to represent the solvent bubble nucleation strength. Third, the respective amounts of the dispersed gas and free gas in each pressure reduction step were obtained from the measured CCEC test data to examine the solvent bubble liberation processes in three heavy crude oil−solvent systems. A second new quantity named the bubble liberation index (BLI) was defined and applied to represent the solvent bubble liberation strength. It was found from the CCE and CCEC tests that the measured Pcell−vt data for each heavy crude oil−solvent system had three distinct regions. Region I was the one-phase region. Region II was the foamy-oil region, in which the solvent bubble nucleation started and the solvent bubbles were dispersed in the heavy oil. Region III was the two-phase region, in which the free-gas phase was formed and started to dominate the total compressibility of the heavy crude oil−solvent system. In addition, the solvent supersaturation vs. reduced pressure data indicated that the heavy crude oil−CH4 system had the lowest solvent supersaturation at the same reduced pressure in comparison with the heavy crude oil−CO2 or C3H8 system. Thus CH4 was easier to be nucleated from the heavy oil in comparison with CO2 or C3H8. Moreover, the BNI vs. solvent supersaturation data showed that the BNI of the heavy crude oil−CH4 or C3H8 system was slowly increased at lower solvent supersaturations but quickly increased at higher solvent supersaturations, whereas the BNI of the heavy crude oil−CO2 system was almost linearly increased with solvent supersaturation. Furthermore, the BLI vs. reduced pressure data revealed that in comparison with C3H8/CO2, CH4 was the most difficult solvent to be liberated from the heavy oil once its bubbles were nucleated. A large amount of CH4 bubbles could be trapped in the heavy oil to induce the strongest and most stable foamy oil in comparison with C3H8 and CO2. The above experimental findings help to better understand the foamy-oil strengths and stabilities in different heavy crude oil−solvent systems and determine the most suitable solvent to optimize a solvent-based enhanced oil recovery (EOR) process in a heavy oil reservoir.
Much uncertainty exists about the vulnerability of valuable tidal marsh ecosystems to relative sea level rise. Previous assessments of resilience to sea level rise, to which marshes can adjust by sediment accretion and elevation gain, revealed contrasting results, depending on contemporary or Holocene geological data. By analyzing globally distributed contemporary data, we found that marsh sediment accretion increases in parity with sea level rise, seemingly confirming previously claimed marsh resilience. However, subsidence of the substrate shows a nonlinear increase with accretion. As a result, marsh elevation gain is constrained in relation to sea level rise, and deficits emerge that are consistent with Holocene observations of tidal marsh vulnerability.
Canada’s interest in agricultural lands has changed with time from a desire of crop yields at Confederation through to discussions in the Senate on adaptation and resilience in 2018. Long-term research experiments (LTRs) have been present and utilized by federal and university researchers to provide answers throughout. Here we highlight the importance of LTRs by identifying the historical context of LTRs and soil health research in Canada. We then briefly describe the history and key results from select LTRs and illustrate the wealth of information collected from the North American Project to Evaluate Soil Health Measurements cross-country point-in-time soil sampling from these LTRs. We discuss the LTRs, and the knowledge gained from them, with the hope that by showing the distinctive narratives associated with each of these study sites, researchers will be inspired to use them to address their research questions and make sound predictions to facilitate the adaptation of Canadian agroecosystems to climate challenges. Through identifying the value generated by these unique LTRs, we hope that the importance of these sites will inspire not only their continued maintenance, but also a next generation of LTRs.
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