Sediment Mixtures Research Articles

Selecting the rational parameters for restoring filtration characteristics of ores during borehole mining of uranium depositst

Purpose. The research purpose is to increase the efficiency of borehole uranium mining by selecting special decolmating solutions and rational parameters of the technology for influencing the seam near-filter zone of geotechnological boreholes, as well as improving the filtration characteristics of the seam, depending on the mineralogical composition of ores and the structure of sediment-forming materials. Methods. The method of X-ray phase analysis was used to study the powders. The core material samples were studied on transparent sections using a LEICA DM 2500 P microscope. The content of the elemental composition of the ores and host rocks in the samples of the productive horizon was controlled using an atomic emission spectrometer. Findings. Based on the research results, quantitative-qualitative characteristics of the host rocks in the productive horizon, sedimentary formations from technological boreholes have been determined, revealing various levels in the productive horizon. It has been found that in the Campanian horizon boreholes, ores have a complex structure and multicomponent sedimentary formations, representing a mixture of sediments of mechanical-chemical origin. Originality. The results of quantitative-qualitative, microscopic, thermal research methods of the characteristics of ore-bearing rocks from various horizons at the Syr Darya depression uranium deposit have been studied and comparatively analyzed. The sedimentary formations of technological boreholes in the productive Santonian, Maastrichtian, Campanian horizons of the Northern Kharasan field, Syr Darya depression, have also been sampled and studied. The choice of the most appropriate composition of chemical reagents for dissolution and prevention of sedimentary formation in porous media has been substan-tiated by the microscopic research method. Practical implications. A detailed study and comparative analysis of the characteristics of ores and host rocks in various productive horizons makes it possible to more accurately plan the mining of blocks, minimizing emerging risks. Using the developed combined technology for intensifying borehole uranium mining, it is possible to increase the efficiency of borehole uranium mining and reduce its operating costs. At the same time, the ecological and industrial safety of the work of intensi-fying the leaching uranium ores increases.

Targeting the source of fine sediment and associated geochemical elements by using novel fingerprinting methods in proglacial tropical highlands (Cordillera Blanca, Perú)

AbstractIn the Cordillera Blanca, the glaciers delineated by some of the highest peaks in the tropical Peruvian Andes have experienced a fast retreat over the last few decades. At the foot of Artesonraju Peak, the glacier‐fed river conveys fine sediments to Parón Lake, which is enclosed in the proglacial area created by the retreating glaciers of the unique confluence of the Huandoy, Chacraraju, Nevado Caraz and Artesonraju peaks (above 6000 m.a.s.l.). This research addresses the sediment contributions of main glacial landforms to sediment mixtures delivered to the river and lake system (1.6 km2) by applying novel conservativeness and consistency methods for tracer selection and a frequentist unmixing model. A total of 27 surface soil and sediment sources (0–3 cm) were sampled from moraines, alluvial fans and recent colluvium, and 10 composite sediment mixtures, including suspended sediments, were collected to identify the sediment provenance. The unmixing results reveal large variability of the contributing sources related to their predominance and the locations of the mixtures. The largest contributions were from moraines, in percentages varying from 28% to as much as 77%. Alluvial fans contributed between 23% and 47% of the sediments, and colluvium material contributed the least, between 6% and 28%. At the time of sampling, ice melt discharge incising moraines and alluvial fans and eroding riverbanks were the main mechanisms of fine sediment delivery. Runoff over the bare surfaces of recently exposed moraines and the lack of vegetation cover in very active landforms also control sediment mobilization. Overall, highly dynamic changes in this paraglacial environment involve active sediment fluxes accompanying snow and ice melt. Our results indicate that in high tropical mountains, shrinking glaciers expose new surfaces of glacial materials, which deliver fine sediments. Identifying the contributing sources is of interest for water and sediment evaluation and management programs.

Structure‐from‐motion photogrammetry demonstrates that fine‐scale seascape heterogeneity is essential in shaping mesophotic fish assemblages

AbstractBenthic components of tropical mesophotic coral ecosystems (MCEs) are home to diverse fish assemblages, but the effect of multiscale spatial benthic characteristics on MCE fish is not well understood. To investigate the influence of fine‐scale benthic seascape structure and broad‐scale environmental characteristics on MCE fish, we surveyed fish assemblages in Seychelles at 30, 60 and 120 m depth using submersible video transects. Spatial pattern metrics from seascape ecology were applied to quantify fine‐scale benthic seascape composition, configuration and terrain morphology from structure‐from‐motion photogrammetry and multibeam echosounder bathymetry and to explore seascape–fish associations. Hierarchical clustering using fish abundance and biomass data identified four distinct assemblages separated by the depth and geographic location, but also significantly influenced by variations in fine‐scale seascape structure. Results further revealed variable responses of assemblage characteristics (fish biomass, abundance, trophic group richness, Shannon diversity) to seascape heterogeneity at different depths. Sites with steep slopes and high terrain complexity hosted higher fish abundance and biomass, with shallower fish assemblages (30–60 m) positively associated with aggregated patch mixtures of coral, rubble, sediment and macroalgae with variable patch shapes. Deeper fish assemblages (120 m) were positively associated with relief and structural complexity and local variability in the substratum and benthic cover. Our study demonstrates the potential of spatial pattern metrics quantifying benthic composition, configuration and terrain structure to delineate mesophotic fish–habitat associations. Furthermore, incorporating a finer‐scale perspective proved valuable to explain the compositional patterns of MCE fish assemblages. As developments in marine surveying and monitoring of MCEs continue, we suggest that future studies incorporating spatial pattern metrics with multiscale remotely sensed data can provide insights will that are both ecologically meaningful to fish and operationally relevant to conservation strategies.

Impact dynamics of mud flows against rigid walls

Mud flows represent one of the major causes of natural hazards in mountain regions. Similarly to debris flows, they consist of a hyper-concentrated mixture of water and sediments flowing down a slope and may cause serious damages to people and structures. The present paper investigates the force produced by a dam-break wave of mud impacting against a rigid wall. A power-law shear-thinning model is used to describe the rheology of the hyper-concentrated mixture. A one-dimensional shallow water model is adopted and a second-order Finite Volume scheme is employed to numerically solve the governing equations. The results indicate that depending on the fluid rheological parameters and on the bottom slope, there exists a minimum value of the wall distance above which the peak force does not exceed the asymptotic value of the hydrostatic final condition. For two different values of the channel slope, the dimensionless value of this lower bound is individuated for several values of the power-law exponent and of a dimensionless Basal Drag coefficient. An estimation of the maximum peak force for wall distance smaller than the minimum value is also provided.

North America's Midcontinent Rift magma volume: A coincidental rendezvous of a plume with a rift

Abstract The Midcontinent Rift of North America is a ca. 1.1 Ga, 3000-km-long failed rift that nearly split the Precambrian continent of Laurentia. Unlike most continental rifts, which are filled with a mixture of volcanic rocks and sediments, the Midcontinent Rift contains a large volume of flood basalts that were emplaced during both syn- and post-rift stages. Consequently, the Midcontinent Rift, which comprises the Keweenaw large igneous province, is the most significant positive anomaly on gravity maps of central North America. We investigated the mantle conditions required to produce this large volume of flood basalt and the observed two main stages of emplacement. To explore whether these magma volumes required a plume or, instead, could have resulted from the increased ambient mantle temperatures expected for the Neoproterozoic, we used a geodynamic model for a range of ambient mantle and plume temperatures under different scenarios of lithospheric extension. The most favorable scenario for the generation of both syn-rift and post-rift lavas combines a plume with excess temperatures between 175 and 225 °C introduced during the syn-rift phase and ambient mantle potential temperatures between 1393 and 1443 °C, with an initial lithospheric thickness not exceeding 150 km for 3 mm/yr extension rates.

Entrainment of bed sediment composed of very fine material

AbstractIn an estuary bed composed of very fine sediment material, tidal currents cause active sediment transportation, bar morphology changes, and severe bank erosion. However, it is difficult to evaluate the erosion rate of a sediment bed composed of particles measuring five to several tens of micrometres using methodologies found in the available literature that estimate entrainment in the presence of fine sediment suspension. This paper proposes a new method to evaluate the erosion rate of a sediment bed composed of very fine material by introducing the concept of entrainment developed for density stratified flows. A series of flume experiments were conducted to investigate the erosion rates of bed material with water–sediment mixtures of different concentrations, sediment particle sizes, and overall Richardson numbers. The results of the flume experiments are compared with past theories and experimental results conducted for density stratified flows. The data show that the erosion rate of a water–sediment mixture is proportional to the inverse of the overall Richardson number, as proposed in previous studies on density stratified flows. In cases with a strong cohesion, the erosion rate can be evaluated using a modified Richardson number, introduced to evaluate the influence of viscosity on entrainment rates. The applicability of the proposed method is also tested by comparing the results of the present study with those of previous studies in terms of equilibrium suspended sediment concentration and size distributions of suspended sediment. The present results show that the proposed method can be used to evaluate not only the erosion rate of suspended sediment but also the characteristics of equilibrium transport processes.

Residential and agricultural soils dominate soil organic matter loss in a typical agricultural watershed of subtropical China

Soil organic matter (SOM) loss in agricultural watersheds driven by hydrology threatens the aquatic environment, and increases the risk of greenhouse gas emissions from aquatic systems, and will be detrimental to both the green development of agriculture and the achievement of the national “carbon peaking and carbon neutrality” goal of China. Consequently, we explored the use of δ13C, δ15N, and the carbon to nitrogen ratio (C/N) as end-members and combined this with a Bayesian stable-isotope mixed model to quantitatively estimate the contribution of typical land-use types (i.e., forest, rice, vegetable, tea, and residential soils) to sedimentary organic matter in a typical agricultural watershed in subtropical China. The results indicated that there was significant spatial variation of δ13C, δ15N, and the C/N in the target sediment mixture and its sources. The range of sediment δ13C (−26.2‰ to −23.8‰) and δ15N (3.9–7.9‰) were within the ranges of the sources, with δ13C and δ15N ranges of − 29.3‰ to − 20‰ and − 1.2‰ to 9‰, respectively. The average C/N of sediment was 11.1 ± 0.52, which was significantly higher than all source samples. The spatial distribution of δ13C and δ15N indicated that SOM loss in this catchment may primarily be attributed to vegetable and residential soils. According to the qualitative identification from dual fingerprint mark composite graphs of the C/N and δ15N, as well as δ13C and δ15N, the sedimentary SOM in the Tuojia watershed was mainly derived from sewage. Furthermore, Bayesian stable-isotope mixed model analysis indicated that residential soil was the main contributor to the SOM loss in the watershed, with a contribution rate of 75.8 %, followed by agricultural land (rice and vegetable soils) with a combined input of 12 %. The findings highlight that anthropogenic life and agricultural production have a vital impact on the carbon and nitrogen cycle in this agricultural catchment, and improving the rural habitation environment may play a key role in the control of SOM loss in subtropical agricultural watersheds.

A comparative study on equilibrium scour volume around circular cylinders in clay–sand mixed cohesive beds, at near threshold velocity of sand – an experimental approach

Abstract Local scour around a bridge pier is a complex phenomenon resulting from the interaction of the three-dimensional turbulent flow field around hydraulic structures. An accurate estimation of scour depth below the stream-bed is important during design since it determines the foundation levels and the expansion of the bridge foundation structures. The present study reveals the results of flume experiments on equilibrium scour depth and scour volumes around circular bridge pier models in clay–sand sediment mixtures. The scouring process in a cohesive sediment mixture is a complex interaction between clay–sand network structure and bed shear stresses. The bed shear stress reduces inside the scour hole as scour depth increases, and this is related to the different modes of scouring in clay–sand mixtures. An exponential equation for the non-dimensional scour volume is proposed considering all the experimental runs to get a specific understanding of the surrounding volume of scour hole from maximum equilibrium scour depth in a clay–sand mixed cohesive bed, when the approach flow velocity is near to the critical velocity for mixed sand. The proposed equations are validated using the pre-existing data from the literature dealing with experimental investigations on bridge scour using clay–sand mixed cohesive sediment and show good agreement with observed data.

Improving the performance of an unmixing model in sediment source apportionment using synthetic sediment mixtures and an adaptive boosting algorithm

Tracing technology is increasingly being used in fluvial and aeolian sediment provenance assessments. Using synthetic sample mixtures in validations of unmixing model performance is becoming a standard step in sediment source fingerprinting. With tracer variability fully considered in the sources and target sediment, this study explored a semiempirical modelling strategy based on virtual sediment mixtures and the adaptive boosting (AdaBoost) algorithm. The obtained integrated unmixing model contained multiple composite fingerprints, and the weight coefficient was obtained from the iterative process. The performance of the integrated unmixing model was compared with that of unmixing models applying single or equal-weighted multiple composite fingerprints. All generated virtual sediment mixtures (280) were split into a training dataset (240) and a test dataset (40) to validate the generalization ability of the models. The results showed that the integrated unmixing model achieved better performance than the unmixing models with a single composite fingerprint (basic models). The integrated unmixing model yielded an average mean absolute error (A-MAE) of 5.51% for training data and 5.72% for test data, and it achieved better accuracy than the best basic model (6.23% on the training and 6.75% on the test dataset, composite fingerprint C-1) or equal-weighted model (6.32% on the training and 6.41% on the test dataset, average of 42 basic models). The robustness of the model accuracy was also improved with the AdaBoost algorithm. The modelling approach proposed in this study has the potential to maximize the use of all tracer information and further improve the reliability of sediment fingerprinting.

Mercury isotopes as a useful tracer of magma sources: An example from the Daocheng-Cuojiaoma batholith, eastern Tibetan Plateau

Magma mixing between mafic and felsic melts is a common magmatic process. Tracing the sources of different magma endmembers is often challenging using traditional isotopes, given the source isotopic signatures are often altered due to isotope fractionation. Mass-independent fractionation of mercury (Hg), which is predominantly generated during Hg photochemical reactions on Earth's surface with little influence from other processes, has the potential to be used as a petrogenetic tracer. This study investigates the Hg isotopic composition of mafic microgranular enclaves (MMEs) and their host granitoids from the Daocheng-Cuojiaoma batholith (DCGB), eastern Tibetan Plateau. Zircon U-Pb dating indicates both the host granitoids and two types of MMEs formed coevally at ca. 216–217 Ma, coherent to the subduction of Garzê–Litang paleo-Tethyan ocean. The host granitoids exhibit negative to slightly positive ∆199Hg values (−0.20 to 0.02‰), indicating that their source magma was a mixture of terrestrial sediments- and mantle-derived melts. Type-I MMEs display arc-like trace element patterns, low SiO2 (53.8 to 55.0 wt%) and positive ∆199Hg values (0.00 to 0.10 ‰), indicating their derivation from a subduction-related fluid/melt metasomatized mantle source. Type-II MMEs show intervening concentrations of major/trace elements, and intermediate ∆199Hg values (−0.18 to 0.02‰), suggesting they were generated via mixing of magmas for Type-I MMEs and granitoid. This study demonstrates the powerful use of Hg isotope as a tracer of magma sources during crustal-mantle interactions.

CFD simulation and model predictive control of the pipeline transportation system in a trailing suction hopper dredger

Abstract The phenomenon of blocking pipe would appear for a trailing suction hopper dredger (TSHD) rake arm pipe in the construction process. Thus, based on the theory of particle flow mechanics, a transient three-dimensional two-phase hydrodynamic and sediment mixture model was established in this paper. Besides, different particle sizes of sediment concentration and velocity in the piping in the rake arm of the law were analyzed to solve the problem of blocking pipe and the prevention of dredging to provide theoretical support. Then, a model predictive controller was designed to regulate the mudflow in the pipeline by controlling the mud pump speed and compared with the proportional-integral (PI) controller. According to the results, the particle size of sediment affects concentration distribution in the pipeline under the same construction conditions for the TSHD. Besides, the larger the particle size of the sediment, the more significant the difference in the sediment concentration distribution in the pipeline. Similarly, the flow velocity is another influencing factor behind the change in concentration distribution in the pipeline, the increase in the flow velocity will improve the uniformity of concentration distribution in the pipeline, and the critical velocity will maintain the concentration distribution within a reasonable range. In terms of transportation control, the designed predictive model controller is capable of reducing overshoot and shorten the time required for adjustment. To sum up, the research result not only provides a valuable reference for the theoretical analysis and a controller design of the pipeline transportation system in the TSHD but also verifies the feasibility of the computational fluid dynamics model used in the study of pipeline transportation mechanisms.

Diagnosing microbiologically influenced corrosion at a crude oil pipeline facility leak site – A multiple lines of evidence approach

In crude oil transmission pipelines, some parts of the system receive minimal or no fluid flow (‘dead legs’), which can on occasion lead to under deposit corrosion wherein a mixture of sediments, hydrocarbons, water, and microorganisms collectively contribute to an integrity failure. However, the microbial contribution to this phenomenon in crude oil transmission pipelines is poorly characterized. To better understand this process, we used a multiple lines of evidence approach to examine a dead leg failure event using sludge samples collected from at andnear the leak location and from non-corroded areas on the same pipe segment. Chemical analyses revealed elevated levels of acetate, total iron, and FeCO3 at the leak locations compared to non-corroded areas. Electrochemical techniques showed increased evidence for corrosion in leak site samples compared to non-corroded samples, while corrosion coupon analysis revealed many localized pits of up to 20 μm deep in leak location samples compared to fewer pits that were up to 4 μm deep from the non-corroded sample after incubating the samples for 30 days. 16S rRNA gene analysis revealed sulfide-producers, acetogens, and methanogens in all collected samples. The lack of detection of FeS as a corrosion product, no significant differences in sulfate and sulfide concentrations across all samples, and elevated levels of acetate at the leak location suggested that acetogens and/or fermentative bacteria contributed to this pipeline leak. This study highlights the use of a multiple lines of evidence approach that can be used to garner evidence to determine the contribution of MIC to failures in dead leg pipeline segments.

Waste-free processing of lowland peat for production of liquid organomineral fertilizers

The Tyumen Region holds extensive resources of peat, which should be considered as a raw material for the production of organic and organomineral fertilizers. The purpose of this research is the development of a waste-free technology for the production of organomineral fertilizers based on humic substances of lowland peat. The tests of three grades of organomineral fertilizer were carried out in accordance with the State Test Methodology, and soil properties were determined in accordance with the relevant state standards (GOSTs). The humic acid extraction method developed at the General Chemistry Department of the Northern Trans-Ural State Agricultural University produces two types of waste in a large volume: a liquid sediment mixture after separation of humic substances from peat and a supernatant solution after precipitation of humic acids. At present, a non-waste method for obtaining organic-mineral fertilizers from lowland peat has been patented. From a liquid sedimentary mixture of peat and humic substances, a peat–humic fertilizer is prepared for application to the soil. This fertilizer increases crop productivity and humus content, and reduces soil acidity. From the supernatant solution with fulvic acids, a huminomineral fertilizer is prepared for foliar feeding of plants. After centrifugation, a humic product is prepared from the gel of precipitated humic acids for pre-sowing, foliar and root feeding of plants. The products were tested on spring wheat, spring rapeseed, onion and apple trees. All products increased the yield and quality of products. The profitability of the production of three grades of organomineral (one product of each stage of production) fertilizer in comparison with the production technology of only one biostimulant is increased by 2.3 times. Currently, the procedure for their state registration is underway.

Scour model for circular compound bridge pier

Abstract Scour is a complex phenomenon, whose complexity increases with the change in the geometry of the obstruction. Most investigations have been carried out on the scour process at a uniform pier. However, in reality, many bridge piers behave as non-uniform depending on the exposure of their foundation into the flow field. All the experimental investigations were carried out in the present study to understand the effect of pier geometry, the position of footing top with respect to bed level, and sediment mixtures (uniform and non-uniform) on local scour under clear water conditions. A total of 106 experiments were conducted in the present study with a different combination of pier models, sediment mixture, and footing top with respect to bed. A maximum scour depth model was developed using 182 data points consisting of experimental data (106) and extracted from the literature (76). To develop a model, a state-of-the-art artificial intelligence (AI) based modeling technique known as gene expression programming (GEP) was employed in this study. The GEP model was developed by using 130 data points and independent 52 data points for the model validation. The performance of the proposed scour model for the compound bridge pier was found to be satisfactory.

SURFACE FLOWS SIMULATION BY CELLULAR AUTOMATA: A SHORT REVIEW OF THE LLUNPIY MODEL

Lahars represent one of the most destructive natural disasters regarding the loss of human lives, but also for making havoc on public infrastructures and ecological habitats. They are very complex surface flows subdivided into two main categories, primary and secondary lahars. Primary lahars are those that originated directly from eruptive volcanic activity, as in the tremendous 1985 Colombian event of Nevado del Ruiz. In contrast, secondary lahars may occur in post-eruptive events or quiescent periods. This volcanic debris flow, a mixture of water and pyroclastic sediments with high density and viscosity, under steep-slope conditions, is capable of reaching high speeds and can travel great distances. A variety of approaches have been adopted to model the behavior of lahar and to predict the hazards posed to downstream communities: empirical models developed, accounting mainly for some macro-observable phenomena, simple rheological and hydrological models that assume reasonable simplifications as a composition-independent flow behavior or a Newtonian flow regime, partial differential equations (PDE) which approximately describe the lahars, highly complex physics and hydrodynamics, and the Cellular Automata alternative methodology. Cellular Automata are a parallel computational paradigm for modeling complex systems by defining simple laws at a local level that generate a global complex evolution. The research, reported in this book, adopts a Multicomponent (or Macroscopic) Cellular Automata (MCA) approach that was developed for numerical simulation purposes by an interdisciplinary research group in Italy. Its reliability and validation on various past events, related to both primary and secondary lahars and debris flow catastrophic events, produced many significant scientific results.

BASIC RESEARCH ON THE MECHANICAL BEHAVIOR OF METHANE HYDRATE-SEDIMENTS MIXTURE

The possible existence of a vast amount of methane hydrate around islands has attracted attention as the largest potential hydrocarbon resource in Japan. At the same time, several production methods have been considered to extract the gas from the hydrate zone. Although it is known that the hydrates pose significant obstacles to drilling and production operations, there is at present only limited knowledge on the mechanical behavior of hydrate-rich zones, which is necessary to understand the stability around the site. In order to know the properties of methane hydrate and/ or its sand mixtures, a series of tests was carried out on artificial methane hydrate-sand mixtures, using low temperature and a newly developed high confining pressure triaxial compression technique. The sediments used in the mixture were obtained from a 207.75 m sea bottom core from the Nankai Trough, located 1152.75 m below sea level. The specimens used were prepared by compressing a mixture of artificial methane hydrate and the sediments with a volume ratio of sediments to the whole of specimen. On the basis of these experimental results, the factors affecting mechanical properties of the hydrate and sediment mixtures are discussed. It is very essential to collect more data on the properties of methane hydrate and/or sedimentation (soil) mixture to understand the stability of any attempt at methane hydrate production.

Particle size effect on geochemical composition of experimental soil mixtures relevant for unmixing modelling

Sediment fingerprinting experiments have been used to demonstrate the sensitivity of numerical mixing model outputs to different particle size distributions in source materials and experimental sediment mixtures. The study aims to examine further grain size effects in the distribution of geochemical elements by soils through a laboratory experiment simulating mixing and sorting processes, to investigate if different size fractions are influencing fingerprinting analyses and unmixing model results. Multiple particle size fractions are analysed to understand the relationship between particle size and source signal through elemental signatures. FingerPro model was applied to unmix six experimental mixtures with known percentages contribution from three experimental sources. The experimental design comprised four different setups with a specific size fraction for sources (S) and mixtures (M). Setups A (S <63 and M <63 μm) and B (S <20 and M <20 μm) relies upon a comparable particle size fraction for sources and mixtures, while C (S <63 and M <20 with PSC) and D (S <63 and M <20) address particle size impacts simulating fine enrichment, with and without a single particle size correction factor, respectively. Tracers were extracted after applying two statistical tests, the range test (RT) and a combination of RT, Kruskal-Wallis (KW) and DFA tests thus obtaining the set of optimum tracers for each mixture. Our findings indicate that source apportionment results are sensitive to tracer selection and particle size. The most accurate source apportionment results were achieved when comparing sources and mixtures with the <63 μm grain-size fraction (setup A) by using the set of tracers extracted after RT, KW and DFA tests, (mean RMSE: 2%, AE: 2%). Larger errors were obtained progressively for setups B, C and D with better results when using more number of tracers from RT (mean RMSE: 7, 10, 13%, AE: 8, 11, 15%, respectively). The main strength of using experimental mixtures with a known contribution of the sources relies on reducing the uncertainty of the unmixing model outputs, one of the main limitations in fingerprint studies. The impact of SSA on the elemental concentration is difficult to predict because the positive linearity between them does not apply equally to all elements and this assumption needs to be constantly examined and considered for fingerprinting studies. Otherwise, the use of a single particle size correction factor could negatively affect unmixing results. The outcomes of this research will help to develop appropriate strategies for sediment fingerprinting, contributing to our knowledge of processes affecting sediment geochemistry and sediment transport across different particle sizes.

Microplastic Extraction from the Sediment Using Potassium Formate Water Solution (H2O/KCOOH)

Microplastics (MPs) are considered an important stratigraphic indicator, or ‘technofossils’, of the Anthropocene. Research on MP abundance in the environment has gained much attention but the lack of a standardized procedure has hindered the comparability of the results. The development of an effective and efficient method of MP extraction from the matrix is crucial for the proper identification and quantifying analysis of MPs in environmental samples. The procedures of density separation used currently have various limitations: high cost of reagents, limited solution density range, hazardous reagents, or a combination of the above. In this research, a procedure based on density separation with the use of potassium formate water solution (H2O/KCOOH) in controlled conditions was performed. Experimental sediment mixtures, spiked with polyethylene (PE), polystyrene (PS), polyurethane (PUR) and polyethylene terephthalate (PET) particles were prepared and an extraction procedure was tested in the context of a weight-based quantitative analysis of MPs. This article discusses the effectiveness and safety of the method. It additionally provides new information on the interactions between MP particles and the mineral matter of the sediment. Results were acquired with the use of instrumental methods, namely thermogravimetry (TG), Fourier Transform Infrared (FTIR) spectroscopy, Field Emission Scanning Electron microscopy and Energy Dispersive spectrometry (SEM/EDS), as well as X-ray fluorescence (XRF) analysis.

Thermophiles and carbohydrate-active enzymes (CAZymes) in biofilm microbial consortia that decompose lignocellulosic plant litters at high temperatures

The SKY hot spring is a unique site filled with a thick layer of plant litter. With the advancement of next-generation sequencing, it is now possible to mine many new biocatalyst sequences. In this study, we aimed to (i) identify the metataxonomic of prokaryotes and eukaryotes in microbial mats using 16S and 18S rRNA markers, (ii) and explore carbohydrate degrading enzymes (CAZymes) that have a high potential for future applications. Green microbial mat, predominantly photosynthetic bacteria, was attached to submerged or floating leaves litter. At the spring head, the sediment mixture consisted of plant debris, predominantly brownish-reddish gelatinous microbial mat, pale tan biofilm, and grey-white filament biofilm. The population in the spring head had a higher percentage of archaea and hyperthermophiles than the green mat. Concurrently, we cataloged nearly 10,000 sequences of CAZymes in both green and brown biofilms using the shotgun metagenomic sequencing approach. These sequences include β-glucosidase, cellulase, xylanase, α-N-arabinofuranosidase, α-l-arabinofuranosidase, and other CAZymes. In conclusion, this work elucidated that SKY is a unique hot spring due to its rich lignocellulosic material, often absent in other hot springs. The data collected from this study serves as a repository of new thermostable macromolecules, in particular families of glycoside hydrolases.

Numerical modeling of two dimensional non-capacity model for sediment transport by an unstructured finite volume method with a new discretization of the source term

The main goal of this work is the resolution of the two-dimensional shallow water equations of water–sediment mixture coupled to the transport diffusion equation for the total sediment load, and bed change rate equation by Roe scheme with a new discretization of the source term. The proposed discretization is well-balanced with the flux gradient and uses data right and left on the interfaces between two control volumes and satisfies the C-property. The numerical method uses unstructured meshes and incorporates minmod limiter and Runge–Kutta method to reach second order spatial and temporal accuracy. We also use an adaptive mesh based on gradient concentration of sediments to refine the study domain with a lower computational cost. We present some numerical results in order to verify and validate the performance of the numerical scheme, particular attention is given to the treatment of the dam-break problem over mobile beds. The numerical scheme demonstrates the intended accuracy and robustness to modelize dam-break flows over erodible bed.