Natural Streams Research Articles

Patterns of oviposition site selection of four sympatric species of amphibians in ephemeral streams

AbstractMany oviparous animals are selective about where to lay eggs, as this greatly affects their offspring’s survival. Theoretically, species sharing the same habitat are expected to experience similar selective pressures, leading to the prediction that they might share similar oviposition preferences. However, this hypothesis has not yet been tested. In this study, through an extensive field survey, we examined the oviposition site selection of four sympatric amphibian species (Rana uenoi, Hynobius quelpaertensis, Bombina orientalis, and Dryophytes japonicus) that reproduce in the same natural ephemeral stream. Our focus was on understanding how abiotic and biotic factors influence their reproductive choices. We primarily found that desiccation avoidance is a universal selective pressure affecting all species, with a tendency to avoid laying eggs in smaller pools prone to desiccation. Species-specific responses to leaf litter and canopy coverage were observed, but none of the species’ oviposition choices correlated with the quantity of stones in pools. We also explored biotic influences, revealing species-specific trends in the selection of pools with conspecific and heterospecific juveniles, predators, and mosquito larvae, indicating a complex ecological interplay. These findings highlight the complexity of ovipositional patterns in animals, where decisions are not driven solely by a single factor such as the avoidance of predators or competitors but also by intricate assessments of multiple factors. The study highlights that amphibian oviposition in ephemeral streams is influenced by a diverse interplay of biotic and abiotic factors, essential for understanding their reproductive strategies in dynamic environments.

Dominance and size affect foraging position choice by Arctic grayling (Thymallus arcticus).

Salmonid fishes are a widespread and economically important group of fishes that are strongly affected by anthropogenic environmental degradation. Consequently, studies on their behavior and ecology are essential for their conservation. Wild Arctic grayling (Thymallus arcticus) were observed in an unimpacted Alaskan river using underwater video observations for two consecutive summers (2015 and 2016). Foraging, aggressive behavior, and position held by individual fish were quantified. Fish held focal positions in the water column most of the time (mean = 81%), active foraging was observed for 14% of the observation periods, and antagonistic interactions occurred during 5% of the time. The analysis of intraspecific aggression revealed that aggressive interactions occurred between conspecifics of similar sizes (±100 mm), although the winners of bouts were significantly larger than the losers. Notably, initiators emerged as more successful in these bouts compared to receivers, irrespective of body length. These findings underscore the significance of conducting field studies to gain valuable insights into the behavior of fish in their natural stream environments.

Application of a New Mean Velocity Equation of Flow in a Natural Stream of 8.5m3/s, Its Verification and Extrapolation: Copper Creck River, Virginia (USA)

Application of a New Mean Velocity Equation of Flow in a Natural Stream of 8.5m3/s, Its Verification and Extrapolation: Copper Creck River, Virginia (USA)

Domestic and irrigation water quality on the southern slopes of Mount Kilimanjaro

This study assessed the water quality for drinking and irrigation purposes on the southern slopes of Mt. Kilimanjaro during the dry season under low flow conditions. Fifty-one samples covering eight different water sources (i.e., stream water from natural and anthropogenic impacted streams, domestic water, spring water, rainfall, groundwater, lake water and water from irrigation canals) were collected in a snapshot sampling campaign over 10 days in February 2023. First, physical, chemical and biological parameters were analysed and compared with Tanzanian and international drinking and irrigation water quality requirements. The samples were then ranked according to their suitability for drinking and/or irrigation using water quality indices (WQI). All drinking water quality parameters except for E. coli and turbidity were within the permissible limits. A generalised problem of faecal contamination was found in the study area, including in domestic water, highlighting the need to identify sources of contamination and remediate them before distribution. The drinking water quality index (DWQI) classified 89% of the samples as unsuitable and 11% as excellent for drinking. Irrigation water quality parameters were within the guidelines of restriction of use except for pH in 5 samples. In contrast to the DWQI, the vast majority of the water samples (88%) can be used for irrigation without restrictions according to the irrigation water quality index (IWQI). The suitability of water for irrigation was also assessed using three indices, i.e., Kelley’s Index, Soluble Sodium Percentage and Magnesium Ratio, which indicated potential problems with excess of sodium (about 30% of the samples) and magnesium (about 20%). Further studies combining suitability indices, soil characteristics and crop types are recommended to assess water quality for irrigation use.

Exploring expert perceptions towards emerging pollutants and their impacts in reused wastewater and agriculture

Water sustainability involves several natural and human spheres conditioning the availability and quality of water resources and life conservation. Regarding water quality, currently emerging pollutants (EPs) are a key topic at global scale since they are difficult to remove by traditional water treatment systems. In this context, this work aims to evaluate experts’ perception of several EPs issues with a special focus on semi-arid Mediterranean areas where EPs are negatively impacting water, environmental, and agricultural systems as, in these areas, effluents from water treatment plants are widely reused in the irrigation of crops, urban gardens, and golf courses or directly discharged on natural streams. Particularly, a detailed survey composed of questions about EPs regulation, risk insight, equipment, social and economic impacts, was performed collecting 437 responses. Main results suggested that EPs existence may pose a significant risk and a destabilizing factor in wastewater reuse, with negative impacts to crop irrigation, being managers the class with more concern followed by scientifics and administratives. New EPs regulations raises uncertainty amongst experts since 29 % considered positive its creation, while 20 % estimated this fact as regular and 14 % as negative. As well, although the combination of technologies to improve EPs removal generated agreement, aspects like the treatment charges at water treatment plants or the price/bill of EPs-free water were features of ambiguity. Within EPs elimination, the three expert groups highlighted that technologies impacts in the sustainability spheres will be positive on public health (87 % of responses), social trust (75 %), and environmental sustainability (76 %). Likewise, 88 % of experts concurred that the future of wastewater reuse relies on a combination of technologies. These findings offer valuable information to water legislators and policymakers to manage water resources, especially in semi-arid areas due to the final use of treated effluents and, therefore, the great implications for agriculture, environment and human health.

Drag coefficients and water surface profiles in channels with arrays of linear rigid emergent vegetation

Although vegetation in watercourses has an important ecological function, from a hydraulic point of view, it increases flow resistance, determinates higher water levels and generates a greater risk of flooding. In engineering practice, to determine water levels, the drag coefficient must be known, whose experimental values, in literature, are provided for uniform or quasi-uniform flow. In this paper, the expression of a drag coefficient, previously proposed by the authors for the case of emergent rigid vegetation arranged in a linear manner, was used to simulate experimental water surface profiles, employing the effective width for the first time. The formula was validated by simulating 26 experimental profiles observed at the University of Calabria, over 1100 points in total, plus 8 published in literature. In some of these applications, the vegetation density was much higher than that for which the drag coefficient expression was derived. For this reason, it is possible to consider a new, wider field of validity for it. The proposed equation is independent of the Reynolds stem number, so that it can be used in natural streams and rivers, provided that viscosity effects can be considered negligible. Finally, some comments are offered on the application of a new formula proposed in literature regarding the computation of the profile when downstream depth is taken as a boundary condition.

Fixed-bed natural gas CO2 adsorption performance of ZSM-5 zeolites impregnated with amines

This research studies the fixed-bed natural gas carbon dioxide (CO2) adsorption performance of ZSM-5 zeolites impregnation with different amines: monoethanolamine (MEA), ethylenediamine (ED), ethylenediaminetetraacetic acid (EDTA), and 4-aminophenol. The structural, morphological, and performance characteristics of the modified zeolites were examined through the use of several analytical techniques. These techniques featured Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The thermogravimetric analysis revealed weight losses in two stages linked to the removal of bound water molecules and the breakdown of the hydroxyl structure. Through fixed bed adsorption experiments, it was discovered that ZSM-5 zeolites functionalized with MEA/ED showed the CO2 adsorption capacity. This study investigated how well four different mathematical models—Clark, Yoon-Nelson, Thomas, and Adams-Bohart—could predict CO2 adsorption breakthrough curves from natural gas using non-linear regression methods. The results showed that all models had very high adjusted determination coefficients (Adj. R²) of over 0.99, indicating they matched the experimental data really well for various adsorbents. The analysis highlighted the models' effectiveness in reflecting adsorption kinetics and capacities, particularly noting the superior performance of the Thomas, Adams-Bohart, and Yoon-Nelson models in capturing uniform breakthrough behaviors. These findings underscore the models' utility in enhancing CO2 removal processes in natural gas purification, which is pivotal for optimizing industrial gas processing systems. These results highlight the efficiency of amine-functionalized ZSM 5 zeolites in capturing CO2 from natural gas streams.

Effects of woody debris on alluvial sediment differentiation and particulate organic matter accumulation in a mountainous forest stream in the Polish Carpathians

Woody debris (WD) stabilizes riverbeds, creates habitats, supports biodiversity, and enhances water quality in ecosystems. This study investigates the impact of WD on sediment characteristics and particulate organic matter (POM) accumulation in the Roztoka stream, located within a forested catchment in the Polish Carpathians. The focus is on the influence of different WD types: coarse (CWD, length > 1 m and diameter > 10 cm), fine (FWD, length < 1 m and diameter < 10 cm), and mixed (MWD, a combination of CWD and FWD) on sediment differentiation and POM accumulation. Stand age, ranging from 20 to over 120 years (in 20-year intervals), was also analyzed as a factor affecting WD structure and POM deposition. Results indicate that MWD had the greatest effect on sediment differentiation, with mean grain size (Mz) ranging from −3.91 phi to −0.95 phi. Stand age significantly influenced POM accumulation, with the highest content (19.51%) observed in age classes III and VI. Older stands (> 120 years) had a diminished effect on both WD structure and POM accumulation. This study underscores the critical role of WD in sediment differentiation and provides insights for improving the ecological function of natural streams. Although the findings are region-specific, they have broader implications for similar temperate mountainous forests.

Study on the Water Use at the Tailwater of Nam Theun 2 Hydropower Station through the Canal of the 3rd Water Gate (Case study: Nongping and Boungbao villages) Nhommalath District, Khammounce Province

Water management is managed through the Nam Theun 2 hydroelectric project. The project has released water in two parts: 1) Water gates and channels release water into natural streams about 30 km long and can drain 1,200 m3/s; and 2) Releasing through the newly constructed regulating dam to the Xe Bang Fai River directly, with a length of about 27 km, can drain 330 m3/s. According to the length of the channel, there is a built water gate for 5 irrigations. Currently, only 3 water gates have been opened to supply water for production in 9 villages that depend on Nhommalath district, Khammouane province. In order to make the use of water through the channel to the maximum benefit, it can operate together between electricity generation and the actual use of water by the community. In this chapter, we have studied the amount of water flow according to the season through Regulating Dam during the past 11 years. Since 2012 to 2022, we have studied the participation of farmers in the management and use of water within the scope of agricultural land. Through comparing the amount of water flow during the past 11 years, from 2012 to 2022, The amount of water flow through the channel with the lowest flow in December 2022 is equal to 0.0 cubic meters per second caused by the stoppage of the company's electricity production to do various repairs, and the highest flow rate in November 2016 was 318.18 cubic meters per second. The reason is that the project has full production capacity to respond to the electricity buyers. Among them, the annual average flow volume with the lowest value in 2022 is equal to 153.06 cubic meters per second, and the annual average flow volume with the highest value in 2017 is equal to 239.11 cubic meters per second. At the time the company stopped production, it used a backup pump with a suction power equal to 0.083 m3/s, which was installed at 2 points to pump water into the irrigation channel for the people. The company is responsible for all costs, such as fuel for the pump, maintenance of the pump, and the water system from the pump to the channel. Assessment of farmers' participation in water management with topics such as survey participation and data collection, participation in the implementation of four seasonal plans, participation in monitoring and evaluation, and participation in the review of all outputs is at a very satisfactory level ( = 3-3.8), except for the topic of participation in determining water use regulations within the channel, and the flood problems are evaluated at a moderate level ( = 2.4). Because of management, the municipality has appointed a committee and has specific management rules. There has never been a natural disaster in the area in the past, such as a drought or flood.

Economic Growth through Rent Streams, Financial Development and Institutional Quality in Mena

This study examines the relationships between natural rent streams, financial development, institutional quality, and economic growth in the Middle East and North Africa (MENA) region and is the development of fixed effects panel models during 1990–2020. The analysis of the MENA region sheds light on the complex, dynamic nature of the region’s economies and societies, as this region is an interesting case study where economic, political and cultural dynamics are diverse. The region faces economic diversification needs, conflicts, migration, and climate change, making this study timely and relevant. To this end, fixed effects regressions and scenario approaches were applied to the collected panel data. The findings reveal natural resource rents as the primary driver of economic growth, their effectiveness dependent on financial development and institutional quality levels. A well-developed financial sector facilitates efficient channeling of rents into productive investments, while strong institutions mitigate resource curse effects. In contrast, while remittances and foreign aid do not directly impact growth, their effectiveness is enhanced by financial development and institutional frameworks. The results highlight the critical roles of financial sector development, institutional quality, and robust governance in shaping the impacts of resource rents in this resource-rich region. The policy recommendations emphasize strategies for managing resource wealth, strengthening financial systems, promoting inclusion, improving institutions, and fostering an enabling environment for remittances and foreign aid to promote sustainable economic growth.

Sample selection disparity: Sampling only cobble overestimates the biomass of stream benthic algae

AbstractDespite the fact that scientists are aware that the streambed consists of various substrata in size, the estimation of benthic algal biomass has been conducted based almost exclusively on cobble sampling. This disparity in samples selected for the biomass estimation occurs because frame sampling collects all substrata, encompassed by the frame, including sand and stones, and is a time‐consuming method compared to single‐stone sampling. We conducted frame versus cobble sampling to test for sample selection disparity (SSD) in the estimation of benthic algal biomass. Estimates of algal biomass based on the frame sampling (area: 0.25 m2) were compared with those based on the cobble sampling taken at the same sampling points in a diatom‐dominated stream. Benthic algal biomass estimated based on cobble sampling was larger than the biomass estimated with frame sampling. The contribution of cobbles to the algal biomass encompassed by the frame was considerably higher than smaller substrata. These results suggest that cobble sampling tends to result in an overestimate of the benthic algal biomass in natural streams. Because the frame sampling requires intensive labor and time, we here proposed a general model based on quick visual assessments for percentage cover of cobbles on the streambed to calibrate estimates obtained by cobble sampling.

Assessing the Potential of Environmental DNA for Monitoring Nature‐Like Bypasses: Erroneous Surveillance Owing to DNA Flow‐Through

ABSTRACTNature‐like bypasses refer to fishways that simulate natural streams. Apart from facilitating fish migrations, bypasses possess the capacity to enhance biodiversity in dammed rivers. Feasibility of environmental DNA (eDNA) as a tool for bypass assessments is unknown. This study investigated fish eDNA in 10 bypasses and their main channels. Initially, the relative DNA flow‐through was estimated in bypasses. Subsequently, the impact of environmental factors and bypasses on fish assemblages was evaluated, and the robustness of the eDNA and electrofishing methods was assessed pertaining to bypass monitoring. The eDNA flow‐through was computed using an equation to estimate the residual DNA at specified distances downstream of the source site. The relative DNA flow‐through was lowest in the longest bypass with low flow rate and highest in the shortest bypass with higher flow rate and was dependent on the DNA decay rate coefficient used. The redundancy analysis revealed significant effects of spatial location, agriculture, catchment area, and bypass length on the species composition. The within‐river analyses indicated significant and nonsignificant bypass effects on species composition and total species richness, respectively. Higher richness and DNA abundance of migratory and threatened species were observed in the bypasses than in the main channels. The eDNA samples displayed higher species richness compared to electrofishing. The species composition of the bypass eDNA samples was intermediate between that of the main channel eDNA and bypass electrofishing samples, which further corroborated performance of eDNA flow‐through in bypasses. Therefore, bypass eDNA samples represented variable mixtures of local and main channel assemblages, indicating relatively low robustness of eDNA for quantitative and spatially accurate bypass assessments. Nevertheless, these results demonstrate practical applicability of eDNA in surveying the presence of desired species and evidence of the benefits of bypasses in supporting biodiversity and species threatened by damming.

Analysis of Hydraulic Characteristics and Acquisition of Flood Management Data Using D-HSI in Natural Streams

Natural disaster prevention requires the maintenance of the proper function of river flow during droughts and heavy rains caused by abnormal weather as well as the minimization of damage via rapid and accurate predictions. This study analyzed hydraulic characteristics by utilizing D-LiDAR (Drone LiDAR) topographic data and D-HSI (Drone Hyperspectral Image) data to quickly and accurately collect and analyze related data. The HEC-RAS model was used to compare and analyze the results obtained via the D-LiDAR topographic data of this study, the roughness coefficient of the river master plan, and the results of applying parameters by adding NDVI. As a result, in the case of a 100-year frequency flood discharge, the average velocity decreased by an average of 2.23 m/s when applying the resistance coefficient by area, based on NDVI. Moreover, the flood level increased by an average of 0.30 m, and the cross-sectional area of ​​the flow capacity increased by an average of 20.17 m2. These results confirms that vegetation has a significant influence on the flow characteristics of natural streams. Hence, the data construction and analysis method used in this study can provide useful information regarding the rapid measurement and analysis of river flow characteristics during floods as well as and the development of prediction techniques and warning-related systems for drought and flood prevention.

Carbon capture using ionic liquids: An explicit data driven model for carbon (IV) Oxide solubility estimation

In this study, carbon dioxide (CO2) solubility in 20 different ionic liquids (ILs) belonging to various chemical families was estimated across a broad range of pressures (0.0098–72.24 MPa) and temperatures (292–450 K) utilizing an artificial neural network. The developed model exhibited high accuracy in predicting experimental values, yielding an R2 value of 0.992, a root mean squared error (RMSE) of 0.04, and a mean square error (MSE) of 0.00173. Additionally, the model was presented in an explicit and transparent manner that facilitates its deployment in software applications, which is not commonly seen in other machine learning models in this field. Moreover, the model was made interpretable by utilizing the connection weights algorithm to demonstrate the relative contribution of each model input and the direction in which the input influences the output prediction. In this regard, it was observed that parameters such as pressure, critical pressure, acentric factor, and ionic liquid density enhance CO2 solubility as their values increase, while parameters like temperature and critical temperature exhibit the opposite effect. Another distinguishing aspect of this study is the evaluation of the computational cost of the formulated model and a proposal for its implementation in practical settings. Given that CO2 solubility plays a crucial role in solvent selection for CO2 capture, this research holds relevance for industry professionals in the oil and gas sector who aim to remove CO2 from natural gas streams with the objective of enhancing the calorific value of the product and reducing the damage caused by corrosion to transmission pipelines.

Allometric shifts in foraging site selection and area increase energy intake for Yellowstone Cutthroat Trout but are constrained by functional limits to prey capture

AbstractObjectiveFor foraging animals, energy acquisition is often influenced by an interaction of prey abundance and the amount of space needed to capture sufficient food. Suitable habitat includes those locations where prey capture rates are sufficient to meet energetic requirements for growth and reproduction. Hence, quantifying how space use changes with energy requirements and how prey densities affect prey capture rates in foraging animals provides insight into the mechanisms that create suitable habitat. Here, we were interested in assessing how body size influences foraging site selection, space use, and energy intake by Yellowstone Cutthroat Trout Oncorhynchus virginalis bouvieri. Furthermore, we sought to quantify how foraging rates changed with increasing levels of food.MethodsWe recorded Yellowstone Cutthroat Trout foraging behavior in natural streams and measured space use and foraging rates using three‐dimensional videography.ResultWe found that physical habitat features, such as current velocity, water depth, and foraging distance, were positively correlated with fish body size, but when foraging area was compared to a model of space use, we found that Yellowstone Cutthroat Trout used less space to capture prey than the model predicted. Fish foraging rates and estimated energy intake also increased with increasing prey availability; however, trout captured prey according to a type II functional response, indicating an upper limit to prey capture from handling time constraints.ConclusionThese data demonstrate that Yellowstone Cutthroat Trout display allometric changes in foraging habitat use: larger fish can occupy deeper and faster areas that increase prey encounter rates, but as prey encounter rates increase, the foraging rates become limited by an individual's ability to identify, pursue, and handle prey items.

(Invited) Understanding Potential Losses and pH Distribution in Electrochemical Nitrate Reduction Reaction to Ammonia

Electrochemical nitrate reduction reaction (NO3 -RR) to ammonia is a promising route to eliminate one of the major pollutants in surface and groundwater. When powered by renewable electricity, electrolysis provides a sustainable method to generate ammonia from nitrate ions, facilitating the transition from a linear to a circular economy. Optimizing the physical and chemical properties of electrolysis cells is crucial to make this process economically viable for widespread implementation. Here, we explore how the choice of current density, conductivity, pH, inter-electrode distance, membrane, catalyst, and buffer solution affect nitrate removal performance and efficiency. We develop a modeling framework to investigate the cell characteristics and fluid dynamics during electrochemical NO3-RR using both laminar and bubbly flows. To obtain more precise results, we employed the bubbly flow model (i.e., Multi-phase Fluid) to take into account how gas production near the electrode surface affects liquid velocity, pH distribution, and, ultimately, potential losses. We exploit mass transfer theory to include the current density effect on migration and diffusion. In the absence of a buffer solution, the Nernstian loss became a significant portion of the polarization loss, which increased with current density. We identified the positive effect of the membrane on energy efficiency to be more significant at smaller inter-electrode distances. This study provides insights into the origin of potential losses and pH distribution, enabling electrochemical cell optimization for renewable fuel synthesis. Next, we will discuss our recent work on designing single atom alloys (SAAs) for selective conversion of low concentration nitrate ions in natural wastewater streams from Dairy farm into ammonia. We benchmarked the catalyst's selectivity, activity, and stability following standard protocols established in the field of nitrogen fixation, including control experiments by using an electrolyte that does not contain nitrate ions and performing experiments under the same operating conditions using nitrogen isotopes (i.e., 14NO3 -, 15NO3 -).

Body length determines flow refuging for rainbow trout (Oncorhynchus mykiss) behind wing dams.

Complex hydrodynamics abound in natural streams, yet the selective pressures these impose upon different size classes of fish are not well understood. Attached vortices are produced by relatively large objects that block freestream flow, which fish routinely utilize for flow refuging. To test how flow refuging and the potential harvesting of energy (as seen in Kármán gaiting) vary across size classes in rainbow trout (Oncorhynchus mykiss; fingerling, 8 cm; parr, 14 cm; adult, 22 cm; n=4 per size class), we used a water flume (4100 l; freestream flow at 65 cm s-1) and created vortices using 45deg wing dams of varying size (small, 15 cm; medium, 31 cm; large, 48 cm). We monitored microhabitat selection and swimming kinematics of individual trout and measured the flow field in the wake of wing dams using time-resolved particle image velocimetry (PIV). Trout of each size class preferentially swam in vortices rather than the freestream, but the capacity to flow refuge varied according to the ratio of vortex width to fish length (WV:LF). Consistent refuging behavior was exhibited when WV:LF≥1.5. All size classes exhibited increased wavelength and Strouhal number and decreased tailbeat frequency within vortices compared with freestream, suggesting that swimming in vortices requires less power output. In 17% of the trials, fish preferentially swam in a manner that suggests energy harvesting from the shear layer. Our results can inform efforts toward riparian restoration and fishway design to improve salmonid conservation.

Determination of 137Cs in Natural Water and Waste Streams Using Ferrocyanide Sorbents Based on Various Supports: a Comparative Analysis

Determination of 137Cs in Natural Water and Waste Streams Using Ferrocyanide Sorbents Based on Various Supports: a Comparative Analysis

OLD UKRAINIAN SLOVUTA AND «OLD EUROPEAN» HYDRONYMY

The paper offers a new etymology of the Old Ukrainian hydronym Slovuta and its derivational congeners Slovuticь and Slovutičь against the background of the non-Slavic equivalent Dъněprъ and the Greek transcriptions Δάναπρις and Βορυσϑένης. The proposed explication of OU Slovuta is undertaken in the context of research on «Old European» hydronymy as first introduced within Krahe’s school of thought. The author substantiates the origins of the derivative Slovuticь / Slovutičь in the historical paratactic construction Dъneprъ-Slovuticь. A comparison with other paratactic constructions shows that this derivative is a result of the historical substantivization of Slavic nouns used primarily in the attributive function. In place of its commonly accepted participial interpretation, the author treats the form Slovuta as an athematic denominative from PU *slov-ǫt-a continuing an earlier formation with the original meaning ‛the one who possesses the quality of *slov-’. The postulated base *slov- is characterized by onomatopoetic syncretism of both the sound of rinsing, washing, flowing (PIE *k̂leṷH-) and its perception (PIE *k̂leṷ-), while the termination -ā functions as a «noun class marker» designating a natural stream of fresh water. The author also argues that the underlying formation PIE *k̂leṷH-/ *k̂leṷ-ont-ā >*k̂leṷ(H)-ont-ā (> PS slov-ont-ā > PU slov-ǫt-ā > OU slov-ut-a) could have appeared in the early-inflecting «Old European» period in the formation of Indo-European, transitional from the active grammar type to the system of nominative-accusative grammar.

Efficient separation of carbon dioxide and methane in high-pressure and wet gas mixtures using Zr-MOF-808

The capture and separation of carbon dioxide (CO2) has been the focus of a plethora of research in order to mitigate its emissions and contribute to global development. Given that CO2 is commonly found in natural gas streams, there have been efforts to seek more efficient materials to separate gaseous mixtures such as CO2/CH4. However, there are only a few reports regarding adsorption processes within pressurized systems. In the offshore scenario, natural gas streams still exhibit high moisture content, necessitating a greater understanding of processes in moist systems. In this article, a metal-organic framework synthesis based on zirconium (MOF-808) was carried out through a conventional solvothermal method and autoclave for the adsorption of CO2 and CH4 under different temperatures (45–65 °C) and pressures up to 100 bar. Furthermore, the adsorption of humid CO2 was evaluated using thermal analyses. The MOF-808 synthesized in autoclave showed a high surface area (1502 m2/g), a high capacity for CO2 adsorption at 50 bar and 45 °C and had a low selectivity to capture CH4 molecules. It also exhibited a fine stability after five cycles of CO2 adsorption and desorption at 50 bar and 45 °C − as confirmed by structural post-adsorption analyses while maintaining its adsorption capacity and crystallinity. Furthermore, it can be observed that the adsorption capacity increased in a humid environment, and that the adsorbent remained stable after adsorption cycles in the presence of moisture. Finally, it was possible to confirm the occurrence of physisorption processes through nuclear magnetic resonance (NMR) analyses, thus validating the choice of mild temperatures for regeneration and contributing to the reduction of energy consumption in processing plants.