Sand Fraction Research Articles

Dynamic Shear Responses of Combined Contaminated Soil Treated with Nano Zero-Valent Iron (nZVI) under Controlled Moisture

Nano zero-valent iron (nZVI) technologies have gained recognition for the remediation of heavily contaminated sites and reused as backfilling soil. The moisture environment at these sites not only impacts the reactions and reactivity of nZVI but also the dynamic responses of compacted backfilled soils. The research explored the effects of different nZVI dosages (0.2%, 0.5%, 1%, 2%, and 5%) on Lead-Zinc-Nickel ions contaminated soil under a controlled-moisture condition. Cyclic triaxial tests were performed to evaluate the dynamic responses of treated soil samples prepared using a consistent moisture compaction method. Particle size distribution and Atterberg limits tests assessed changes in particle size and plasticity. The study revealed a minor reduction in the particle size, liquid limit, plastic limit, and plasticity index of the contaminated soil. Notably, increasing nZVI dosages in treated soils led to growing Atterberg limits. An increase in the specific sand fraction of treated soils was observed with nZVI, suggesting nanoparticles–soil aggregations favoring existing larger particles. Stepwise loading cyclic triaxial tests indicated an optimal dynamic response of soil treated with 1% nZVI under the controlled-moisture condition, proven by notable enhancements in the maximum shear modulus, maximum shear stress, less shear strain, and higher damping ratio within the small strain range. It should be noted that moisture content in treated soils declined significantly with higher nZVI dosages during preparation, potentially impeding effective aggregation and the formation of a solid soil skeleton. These findings advance the importance of considering the balanced nZVI dosage and moisture content when employing the safety assessment of practical applications in both nano-remediation techniques and soil mechanics.

Chemodiversity of riverine dissolved organic matter: Effects of local environments and watershed characteristics

Riverine dissolved organic matter (DOM) is crucial to global carbon cycling and aquatic ecosystems. However, the geographical patterns and environmental drivers of DOM chemodiversity remain elusive especially in the waters and sediments of continental rivers. Here, we systematically analyzed DOM molecular diversity and composition in surface waters and sediments across 97 broadly distributed rivers using data from the Worldwide Hydrobiogeochemistry Observation Network for Dynamic River Systems (WHONDRS) consortium. We further examined the associations of molecular richness and composition with geographical, climatic, physicochemical variables, as well as the watershed characteristics. We found that molecular richness significantly decreased toward higher latitudes, but only in sediments (r = -0.24, p < 0.001). The environmental variables like precipitation and non-purgeable organic carbon showed strong associations with DOM molecular richness and composition. Interestingly, we identified that less-documented factors like watershed characteristics were also related to DOM molecular richness and composition. For instance, DOM molecular richness was positively correlated with the soil sand fraction for waters, while with the percentage of forest for sediments. Importantly, the effects of watershed characteristics on DOM molecular richness and composition were generally stronger in waters than sediments. This phenomenon was further supported by the fact that 11 out of 13 watershed characteristics (e.g., the percentages of impervious area and cropland) showed more positive than negative correlations with molecular abundance especially in waters. As the percentage of forest increased, there was a continuous accumulation of the compounds with higher molecular weight, aromaticity, and degree of unsaturation. In contrast, human activities accumulated the compounds with lower molecular weight and oxygenation, and higher bioavailability. Our findings imply that it may be possible to use a small set of broadly available data types to predict DOM molecular richness and composition across diverse river systems. Elucidation of mechanisms underlying these relationships will provide further enhancements to such predictions, especially when extrapolating to unsampled systems.

Thermo- mechanical and microstructural characterization of LECA and low carbon cement based lightweight mortar using box behnken design, and embodied energy analysis

Lightweight aggregate mortar (LWAM) containing different kinds of supplementary cementitious materials (SCMs) has gained significant attention as a sustainable construction material. However, the behavior of this type of mortar at elevated temperature conditions, such as those encountered in fire events, remains largely unexplored. In this study, the effect of different temperatures (i.e. at 27⁰C, 110⁰C and 850⁰C) on the Thermo-mechanical and microstructural properties of LWAM containing low grade limestone slurry (LgLS), class- F fly ash (FA), and lightweight expanded clay aggregate (LECA) is investigated. LgLS and FA were replaced with ordinary Portland cement (OPC) in the range of 0–20%, and 0–30% by weight. River sand was replaced with LECA, ranging from 0% to 50% with an increment of 25% in river sand fractions. Along with this, statistical modelling and parametric optimization were done using Box Behnken Design (BBD) of Response Surface Methodology (RSM). Advanced characterization techniques such as- Field Emission Scanning Electron Microscopy (FE-SEM) and X-ray Diffraction (XRD) were performed to investigate the effect of higher temperatures on the microstructure and hydration products of LWAM matrix. Embodied energy analysis was also carried out to investigate the environmental assessment along with cost analysis. It was concluded that as compared to the reference LWAM mix at 27 °C; CS at 28 days was increased by 15–25% at temperature of 110 °C for different mixes, while the same was drastically decreased by 60–64% at higher temperature i.e. 850 °C. Embodied energy analysis predicted that carbon emission can be minimized by about 25%, which is the need of the recent era to meet sustainable development goals.

Interdisciplinary research of ash heap sediment near Stepnoye settlement (Chelyabinsk Oblast)

An ash heap is defined as a specific object at an archaeological site, usually in the form of a separate hillock containing a layer of finely-dispersed greyish-yellow or ash-coloured soil. The existing assumptions about the formation and functional pur-pose of ash heaps, as special archaeological objects found near the Bronze Age pastoral settlements, have so far been poorly supported by scientific data. At the ash heap near the Sintashta fortified settlement of Stepnoye, Chelyabinsk Oblast, for the first time, large-scale and comprehensive studies were carried out on the structure of these deposits, their granulometric and geo-chemical composition, in combination with the analysis of plant macroremains, paleoparasites, microbiomorphic and palynologi-cal complexes, indicative bacterial groups, and keratinophilic fungi. Judging by the archaeological materials, it is patently obvi-ous that this was a multifunctional object that developed over many centuries and played different roles at different stages. The results of the conducted analyses showed that the 45 cm thick “ash” horizon in the Stepnoye ash heap contains a significant proportion of a fine sand fraction, and not a silty fraction. An increase in the biophilic elements (predominantly calcium, as well as phosphorus and sulphur), accumulated mainly in the organic matter of faunal origin, was noted in the upper bench of the ash layer. However, the high concentration of phytoliths in the “ashy” deposits indicates that the layer was formed mainly as a result of the accumulation of a large amount of plant organic matter. The absence of charcoal and the scarcity of charred macro-remains indicate that the deposited organic material was not burnt but decomposed naturally. The increased content of sapro-trophic bacteria in the “ashy” layer also supports the natural decomposition of an organic matter. The composition of the phyto-lithic and pollen spectrum of the “ashy” horizon is not typical for the steppe of the south of Western Siberia, since it is dominated by a group of mixed herbs with elements of a ruderal flora, and not by cereals. All the data supports the hypothesis that the ash heap is the result of regular practice of cleaning of the floor and interiors of the buildings of the fortified settlement of Stepnoye. This is evidenced by the increase in the number of keratinophilic fungi, which decompose wool and hair and therefore accumu-late in the occupational layer of the structures. Based on the results of the study, the hypotheses that the Stepnoye ash heap is a place of consolidated ash removal or composting of stable manure were rejected.

Changing law of permeability coefficient during compression for reconstituted sandy clays

Sandy clay is defined as a sand–clay mixture with the mechanical behavior dominated by fine clay but affected by coarse sand. Twenty sets of one-dimensional incremental load consolidation and falling head permeability coefficient tests were performed on sandy clays. The samples of sandy clays were prepared by mixing two hosted clays with different sand fractions from 0% to 60%. The interrelation between the change of permeability coefficient with void ratio and the compression curves is established. The results indicate that the effect of sand fractions on permeability coefficient can be attributed to the variation of void ratio at liquid limit induced by sand fractions. The initial void ratio affects permeability coefficient by changing the void ratio under the same effective vertical stress. These two findings highlight that the permeability coefficient-void ratio relationship of sandy clays is a function of void ratio at liquid limit and void ratio. An empirical method of estimating permeability coefficient is also proposed using two physical indices of void ratio and void ratio at liquid limit for sandy clays having void ratio at liquid limits ranging from 0.63 to 1.73 and initial void ratios varying from 0.72 to 2.67.

Palaeoenvironmental and Palaeoclimatic Conditions in the Bhimtal Valley, Kumaun Lesser Himalaya, Between 40 and 24 ka Using Granulometric Analysis

In this research, we conducted a detailed granulometric analysis of 9.5 m thick palaeolake succession, exposed at Bilaspur (Bhimtal) in the Kumaun Lesser Himalaya to reconstruct the palaeoenvironmental and palaeoclimatic conditions. We carried out statistical parameters of grain-size data (i.e., standard deviation, kurtosis, and skewness, bivariate plots), and end member modelling analysis (EMMA) and our study reveal sediment’s unimodal and bimodal nature, deposited via fluvial action under low to high energy environmental conditions since the origin of the lake. Some parts of the deposit show poorly sorted and mixed character (leptokurtic to platykurtic) of sediments, indicating that the sediments were primarily transported from the proximal area of the lake basin under low-energy environmental conditions. The finely skewed and poorly sorted sediments show different modes of grain size distribution, which are attributed to fluctuations in the hydrodynamic conditions of the lake. The arid climatic conditions prevailed in the valley from ca. 42 to 40 ka BP, followed by warm and moist conditions from ca. 40 to 39 ka BP. The arid conditions under the low rainfall regime were experienced by the valley from ca. 39 to 30 ka BP, while it exercised another episode of moist and warmer conditions from ca. 30 to 24 ka BP. Further, the end-Member Modelling Analysis (EMMA) shows four end members (EM1-EM4) with different climatic conditions during the deposition, e.g., clay to fine silt-size particles reflecting higher lake levels under warm-wet climatic conditions, coarse silt fraction representing moderate energy conditions, and fine to coarse sand fractions indicating shallow lake-level conditions in the arid climatic conditions as well higher energy flow. The interpretation of energy conditions in the lake and catchment area by using various methods reveals different palaeoenvironmental conditions during the sediment deposition.

Experimental and numerical investigation on low‐velocity impact response of sandwich structure with functionally graded core

AbstractThe present research investigates optimizing the impact resistance of functionally graded sandwich structures using experimental and numerical approaches. The low‐velocity impact (LVI) responses of functionally graded sandwich composite (FGSC) with different configurations with skin material jute/rubber/jute (JRJ) and core material having epoxy and sea sand by volume fraction of sea sand at 0%, 10%, 20%, and 30%. Sandwich structures were impacted with LVI (5.89, 10.92, and 15.18 m/s), with the impactor dropped from heights of 0.5, 1, and 1.5 m with precompressed spring loads. FGSC samples are considered a deformable body, and the impactor is modeled as a rigid body using commercially accessible dynamic explicit software. The burn‐out test and weight method were used to test the core's gradience; both methods' results substantially matched, and the variance in gradation could be observed. The proposed sandwich structure characteristics are examined by energy absorption, peak force, energy loss percentage, and coefficient of restitution. Results showed that SC30S provides greater energy absorption and superior damage resistance when tested on LVI. To evaluate the accuracy of experimental findings in predicting the indentation behavior of the sandwich structure, the finite element analysis was used to compare with the experimental results. According to the examination of these proposed FGSC overall performance, they could potentially be employed as sacrificial materials for LVI applications like claddings to shield major structural components. The systematic approach used in this work serves as a standard for choosing and using FGSC effectively for LVI applications.Highlights Low‐velocity impact behavior of sandwich structures was investigated. Combining flexible skin and epoxy core enhances energy absorption. Based on impact energy levels, impact damage areas were determined. Examined sandwich structure advantages in structural and aerospace uses. In terms of time and cost, the numerical analysis method would be useful.

The influence of cold seepage on the grain size and geochemistry of sediments from the Laptev Sea shelf

The East Siberian Arctic shelf is renowned for its active methane-rich fluid seeps, confirmed by numerous gas flares in the water column and direct observations of methane release from the seafloor. These cold-seep sites serve as natural laboratories for studying the impact of methane seepage on early diagenesis, authigenic mineral formation, and the geochemical cycles of carbon, sulfur, and other elements. This study examines the grain size and chemical composition of two sediment types from the Laptev Sea shelf: cold-seep sediments influenced by sulfate-driven anaerobic methane oxidation, and unaffected “seep-free” sediments (i.e., control site). High methane concentrations (up to 649 μM/L) in the surface layer of sediments indicate that the sulfate–methane transition zone is found close to the sediment–water interface approximately 5–6 cm below the seabed. At the cold-seep site, thin layers containing up to 40% sand fraction were discovered among the fine-grained sediments. We infer that upward-migrating fluids may contribute to the remobilization of the fine fraction, resulting in concentration of coarse particles. Cold-seep sediments are characterized by molybdenum (Mo) enrichment compared to the lithological background, although one “seep-free” core exhibits evidence of authigenic Mo deposition. The Mo concentration (up to 16.8 ppm) indicates that enrichment occurs under sulfidic conditions restricted to pore water, which are caused by anaerobic methane oxidation. The high Mo concentration in one “seep-free” core likely implies past cold-seep activity. A general Mo–U covariation indicates that the molybdenum enrichment in cold-seep sediments from the Laptev Sea outer shelf is controlled by a weak particulate shuttle process.

Pervious Concrete Made with Recycled Coarse Aggregate and Reinforced with Date Palm Leaves Fibers

This study considers 12 pervious concrete mixes incorporating 100% recycled coarse aggregate from old concrete demolition waste and containing various amounts of natural fine aggregate and date palm leaves fibers. First, the properties of the recycled aggregate in terms of their particle size distribution, abrasion resistance, crushing values, specific gravity and water absorption are obtained. Next, the pervious concrete density, compressive strength, tensile strength, permeability and porosity are determined by experimental testing following the relevant standards. The results are analyzed and compared to determine the influence of using recycled coarse aggregate in the mixtures and the impact of the amount of natural sand and volume fraction of the fibers on the mechanical properties, permeability and porosity of the concrete. Findings of the study showed that the use of recycled coarse aggregate in pervious concrete without fine aggregate reduced the compressive strength by 36% and tensile strength by 57%. Replacing 11.7% of the recycled coarse aggregate with natural sand and adding date palm leaves fibers in an amount equivalent to 0.64% volumetric content to such concrete helped increase the compressive strength by 16.2% and tensile strength by 3.2% above the corresponding strengths of the control mix. There is a clear relationship between permeability and porosity due to their correlation with the density of pervious concrete, and the effect of porosity on tensile strength is more influential than it is on the compressive strength. An equation that can predict the tensile strength of pervious concrete from the compressive strength is proposed, as a function of the natural fine aggregate fraction of the coarse aggregate and volumetric content of natural fibers. Results of the research confirm the feasibility of using recycled aggregate in pervious concrete mixes and the positive impact of natural fibers on the mechanical properties.

Search for the Substantiation of Reasonable Native Elemental Background Values and Reference Variables in Topsoil on Glaciogenic and Postglacial Deposits in a Vilnius Peri-Urban Area

Geochemical indices used to identify the emerging anomalies of potentially harmful elements in topsoil depend on background values (BVs). For urban sites, it is reasonable to estimate native BVs through the targeted selection of peri-urban sampling sites or by distinguishing a useful background subset (BS) within the peri-urban dataset. Here, the goals were to examine the influence of Quaternary deposits on various types of topsoil variables, identify the variables most helpful for cluster analysis intended for the choice of background subset (BS), and compare background values (BVs) based on different background subsets. Composite topsoil samples from a peri-urban area were used for the determination of the following variables: contents of 26 elements and components of the bulk mineralogical composition, as well as the sand, silt, and clay fractions and loss-on-ignition (LOI) at 550 °C and at 950 °C. Although Quaternary lithology influences topsoil elemental contents or granulometric fractions, percentages of illite, kaolinite, orthoclase, quartz, albite, dolomite, and LOI at 550 °C, the choice of BS, according to it, is not recommended, as BVs based on topsoil texture are superior. However, cluster analysis using topsoil fractions &lt; 2, &lt;63, and &gt;63 μm or the contents of Al, Fe, K, Ti, Ga, Nb, Rb, and Si are preferable. It is recommended to use these reference variables for the selection of BS.

Longshore Sediment Transport in Lake Ladoga Based on Analyses of the Heavy Mineral Fraction of Sand in Coastal Sediments

Abstract—In order to identify the directions of transport of coastal sediments of Lake Ladoga, heavy mineral fraction was extracted from sand samples collected on all types of its shores. The mineral composition, size and roundness of particles − features characterising the degree of reworking of coastal sediments − were assessed under a microscopic analysis. We identified 4 clusters with similar degrees of reworking of the source material, which, based on the results of the factor analysis, were ranked by relative transport distance from insignificant to very significant. The maximum number of samples with small transport distances was found on the northern shores of the lake, which can be explained by the location of bedrock shores − the main sources of clastic material in the lake. Samples with maximum transport distances are relatively evenly distributed along all shores of the lake. The analysis of the results showed that on all shore reaches there is a transport of heavy fraction of bottom sediments in a certain direction: on the southern shore – to the west, on the western shore – to the north, on the northern shore – to the east and on the eastern shore – to the south-east. This allows us to conclude that there is a long-term trend of coastal sediment transport along the shores of Lake Ladoga in a clockwise direction.

Land Evaluation for Cassava Cultivation in Southern Slope of Mount Merapi: Case Study in Palemsari Hamlet, Umbulharjo Village (Cangkringan, Sleman)

Palemsari Hamlet (Umbulharjo Village, Cangkringan District, Sleman Regency) is one of areas located in Southern Slope of Mt. Merapi, which was directly affected by the eruption cycle of Mt. Merapi. The aftereffect of 2010 eruption had reduced land productivity, making it less suitable for crop cultivation. Therefore, this study was aimed to re-evaluate the land suitability of Palemsari Hamlet, particularly for cassava cultivation, after 10 years of eruption. This study was carried out from June – November 2021 in Palemsari Hamlet. Physiographic conditions and soil properties were observed through survey. The data obtained were analyzed descriptively and spatially to determine the characteristics through a series of laboratory analysis. This data was used to determine the class of land suitability. Results showed that the land suitability in PalemsariHamlet was considered as moderately suitable (S2) for cassava cultivation. This area was found to have less suitable soil texture due to the high percentage of sand fraction. According to this result, the soil condition in Palemsari Hamlet is potential to be used for cassava cultivation with the support of organic matter application to improve its physical properties. This recommendation could be beneficial for the future land use planning in the affected areas of Mt. Merapi eruption.

Characteristics and potential of tidal swampland to support the lowland rice development: a case study in Maliku Sub-District, Pulang Pisau Regency, Central Kalimantan Province

Tidal swampland is an agroecosystem with distinct characteristics. Studying on this land was very important to support national food security. This study aims to identify the soil characteristics and the potential of tidal rice fields in the Maliku Sub-District, Pulang Pisau Regency, Central Kalimantan Province, Indonesia. Four representative soil profiles were characterized in the field and laboratory to determine the soil’s chemical, physical, and mineralogical properties. The results showed that these soils were generally fine textured, had very acid to acid reaction (soil pH 3.2-4.7), moderate to high C-organic (2-6%), varied potential P2O5 (22-289 mg/100g), low potential K2O (11-17 mg/100g), varied available P2O5 (8.6-56.1 mg/kg), very low exchangeable Ca (<2 cmolc/kg), varied exchangeable Mg (0.6-3.0 cmolc/kg), moderate soil CEC (18-22 cmolc/kg), very low base saturation (<20%), and shallow to very deep (35 - >100 cm) of pyrite depth. The sand fraction mineral is mainly composed of quartz and rock fragments, while the clay fraction is dominated by kaolinite. The lands are marginally suitable for tidal rice fields with the limiting factor being very acid soil reaction and shallow pyrite depth. The application of balanced fertilization, liming, organic matter, minimum tillage, and micro-water control can increase land productivity.

The Content of Magnetic Material in Black Sand of Yeh Gangga Beach

Yeh Gangga Beach is one of the black sand beaches in the Tabanan district. The abundant black sand on this beach stretches along the shoreline with varying grain sizes. This black sand characterizes the specific surface composition as iron sand deposits with high magnetic mineral content. The very high need and use of magnetic minerals in various fields prompt a study of the magnetic mineral content in the black sand of Yeh Gangga beach.The magnetic material content was determined by the extraction method which was expressed in terms of mass fraction. The grain size distribution was determined by the sieve method using a sieve shaker consisting of six mesh numbers, namely 30, 100, 170, 200, 270, and 325.The density of magnetic materials was determined by the principle of mass and volume ratio. The magnetic susceptibility was tested by using a Bartington MS2B susceptibility meter. Meanwhile, the characterization of the elements and their oxides used non-magnetic methods, namely the X-Ray Fluorescence test.The research results show that the magnetic material fraction of Yeh Gangga black sand reach 84.84% with 58.39% of the grains having sizes in the range 150r ≥90 μm. The magnetic susceptibility value is 28.26 10-6 m3/kg with an Fe element content of 85.15% w. The hematite (Fe2O3) content reaches 81.69%. This magnetic material has a density of 1914.43 kg/m3.

Grain Size Analyses and Mineral Compositions of Core Sediments in the Western North Pacific Ocean: Implications for the Rare Earth Element and Yttrium Enrichment and Deposition Environment

Rare earth element and Yttrium (REY)-rich deep-sea sediments have been identified as significant potential resources. Although grain size analysis is important for the study of deposition environment and the future exploration of REY, related research is limited. Here, we have investigated the grain size and mineral composition of bulk pelagic sediments from Western North Pacific to indicate the evolutions of deposition environment. Grain size analysis results reveal that silt contents are dominant, and the grain size ranges between 20 and 40 μm and can be an additional grain characteristic indicator for REY-rich sediments. Furthermore, the better sorting coefficient of REY-rich sediments reflects the scouring action of bottom currents, which allows the preservation of coarse-grained bioapatite and the removal of clay fraction particles. ΣREY is negatively correlated with clay fractions but positively correlated with sand and silt fractions for the REY-rich sediments, and this is consistent with the dominant distribution of silt-sized biogenic apatite. In addition, grain size distribution (GSD) varies significantly after HCl treatment in the REY-rich sediment. Therefore, for deep-sea sediments collected below the carbonate compensation depth (CCD), an additional presence of a grain size peak at ~20–40 μm and distinct differences in GSD after HCl treatment can serve as important indicators for REY enrichment sediments.

Uniformity in Tophet Ceramics?

Abstract Burial urns and lids found in the Carthage tophet precinct play a pivotal role in our understanding of material trajectories. Significant differences in macroscopic features present problems as to where and how these vessels were made. In general, issues in sourcing north African ceramic materials stem from their compositional homogeneity, having mostly sand and calcareous fractions varying to a greater or lesser degree. In this paper we present the results of a petrographic study of ceramic materials in order to understand the different fabrics present within the tophet assemblage, with the ultimate aim of determining whether or not their production took place in Carthage itself and to trace transformations in local and regional ceramic fabric types.

Soil Texture Mapping in Songnen Plain of China Using Sentinel-2 Imagery

Soil texture is a key physical property that affects the soil’s ability to retain moisture and nutrients. As a result, it is of extreme importance to conduct remote sensing monitoring of soil texture. Songnen Plain is located in the black soil belt of Northeast China. The development of satellite imagery in remote sensing technology enables the rapid monitoring of large areas. This study aimed to map the surface soil texture of cultivated land in Songnen Plain using Sentinel-2 images and Random Forest (RF) algorithm. We conducted this study by collecting 354 topsoil (0–20 cm) samples in Songnen Plain and evaluating the effectiveness of the bands and spectral indices of Sentinel-2 images and RF algorithm in predicting soil texture (sand, silt, and clay fractions). The results demonstrated that the 16 covariates were moderately and highly correlated with soil texture. And, Band11 of Sentinel-2 images could be used as the corresponding band of soil texture. For sand fraction, the Sentinel-2 images and RF algorithm’s Coefficient of Determination (R2) and Root Mean Square Error (RMSE) were 0.77 and 10.48%, respectively, and for silt fraction, they were 0.75 and 9.38%. Sand fraction decreased from southwest to northeast in Songnen Plain, while silt and clay fractions increased. We found that the Songnen Plain was affected by water erosion and wind erosion, in the northeast and southwest, respectively, providing reference for the implementation of Conservation Tillage policies. The outcome of the study can provide reference for future soil texture mapping with a high resolution.

MOC Composites for Construction: Improvement in Water Resistance by Addition of Nanodopants and Polyphenol.

The topic of modification of magnesium oxychloride cement (MOC) using specific functional additives is very much pronounced in the research of alternative building materials. This study deals with the co-doping of MOC by 1D and 2D carbon nanomaterials in order to improve its mechanical properties while using tannic acid (TA) as a surfactant. Furthermore, the effect of TA on MOC also improves its water resistance. As a filler, three size fractions of standard quartz sand are used. The proposed types of MOC-based composites show promising results considering their mechanical, macro- and microstructural, chemical, and hygric properties. The use of 1D and 2D nanoadditives and their mixture enables the improvement in the flexural strength and particularly the softening coefficient, which is the durability parameter characterizing the resistance of the prepared materials to water. After immersion in water for 24 h, the compressive strength of all tested specimens of modified composites was higher than that of the reference composite. Quantitatively, the developed co-doped composites show mechanical parameters comparable to or even better than those of commonly used Portland cement-based materials while maintaining high environmental efficiency. This indicates their potential use as an environmentally friendly alternative to Portland cement-based products.

Sr-Nd isotopic compositions of aeolian sand in the northern Ulan Buh Desert and Yamalik Desert: Implications for provenance and transport processes

Tracing the provenance of aeolian sand in deserts is essential for comprehending the mechanisms underlying desert formation and sediment transportation processes. There are multiple sand belts that interconnect major deserts within the Alxa Plateau of northern China, as evidenced by satellite images and field research. However, the aeolian sand transport from the Badain Jaran Desert (BJD) to the Yamalik Desert (YD) and Ulan Buh Desert (UBD) through these expanding sand belts is still being underestimated. In this study, we analyzed trace metal contents and Sr-Nd isotopic compositions in the < 125 μm fraction of dune sands in the northern UBD and YD, along with bedrocks from the Langshan Mountains (LM). Based on bivariate plots of Zr vs. Hf, Zr/Hf vs. Hf, Cr/V vs. Y/Ni, and Th/Co vs. Th/Sc, the aeolian sands in the northern UBD and YD have similar sources but are different from those in the southern UBD. Comparison of Sr-Nd isotopes with potential source areas suggests that fine-grained aeolian sands in the YD and northern UBD are mainly sourced from the BJD and the southern Mongolian Gobi. Although the heterogeneity of bedrock samples impeded the precise interpretation of contributions from all potential sources, the εNd(0) signatures in the UBD suggest that up to 25% of the fine-grained sand is derived from the LM, which displays highly negative εNd(0) values. On a larger geographical scale, the northern UBD serves as a transfer intersection for long-distance transportation of sand and dust ultimately sourced from the Central Asian Orogen and northern Tibetan Plateau. This study also demonstrates the essential role of sand belts in facilitating aeolian transport within the Alxa Deserts.

Understanding the impact of sand extraction on benthic ecosystem functioning: a combination of functional indices and biological trait analysis

Marine aggregates have been intensively extracted in the North-East Atlantic over the past decades. This study aimed to assess the effect of sand extraction on benthic ecosystem functioning using a combination of biological traits and functional indices (the bioturbation (BPc) and irrigation potential (IPc) and secondary production (SPc) of the macrobenthic community). Data on macrobenthos, sediment properties and extraction intensity were collected over a time period of ten years (2010 – 2019) for three coarse sediment extraction areas in the Belgian Part of the North Sea, each with a different extraction regime. Sediment parameters such as the medium sand fraction (250 – 500 µm) and median grain size showed a significant effect on all functional indices. Whilst sand extraction variables only significantly affected secondary production estimates. The secondary production of the macrobenthic community decreased following a high yearly extraction intensity, whereas a high cumulative (10-year period) extraction intensity resulted in a slightly increased secondary production. Species-specific responses revealed that these high cumulative extraction volumes increased the abundance of opportunistic species, which could have contributed to the higher SPc values observed in cumulative disturbed areas. Response traits such as tube-living and sessile individuals with a pelagic egg development were positively influenced by a long-term disturbance, an indication of a more disturbance-tolerant community. A short-term disturbance rather seemed to favor a macrobenthic community characterized by a higher burrowing capability. In terms of effect traits, both short- and long-term extraction clearly favored deposit feeders, which can structure organic matter distribution and thus indirectly influence nutrient and oxygen fluxes as well. Future in situ measurements in sand extraction areas could help to unravel and strengthen our understanding of the ecosystem processes linked to these trait-based observations.