Clay-sized Particles Research Articles

Global-scale no-tillage impacts on soil aggregates and associated carbon and nitrogen concentrations in croplands: A meta-analysis

No-tillage treatment, including no-tillage with straw retention (NTS) and without (NT), has been widely used as an efficient and sustainable alternative to conventional tillage with straw retention (CTS) and without (CT) and greatly affects soil physical quality and organic matter dynamics in cropland ecosystems. Although some studies have reported the effects of NTS on soil aggregate stability and soil organic carbon (SOC) concentration, the underlying mechanisms of how soil aggregates, aggregate-associated SOC and total nitrogen (TN) respond to no-tillage remain unclear. Through a global meta-analysis of 91 studies in cropland ecosystems, we evaluated the effects of no-tillage on soil aggregates and their associated SOC and TN concentrations. On average, no-tillage treatment significantly decreased the proportions of microaggregates (MA) by 21.4 % (95 % CI, −25.5 to −17.3 %) and silt+clay size particles (SIC) by 24.1 (95 % CI, −30.9 to −17.0 %), and increased the proportions of large macroaggregate (LA) by 49.5 % (95 % CI, 36.7–63.0 %) and small macroaggregate (SA) by 6.1 % (95 % CI, 2.0–10.9 %) compared to those in conventional tillage. The SOC concentrations for all three aggregate sizes increased significantly with no tillage: for LA by 28.2 % (95 % CI, 18.8–39.5 %), SA by 18.0 % (95 % CI, 12.8–23.3 %), and MA by 9.1 % (95 % CI, 2.6–16.8 %). TN also increased significantly for all sizes with no tillage, with LA by 13.6 % (95 % CI, 8.6–17.6 %), SA by 11.0 % (95 % CI, 5.0–17.0 %), MA by 11.7 % (95 % CI, 7.0–16.4 %), and SIC by 7.6 % (95 % CI, 2.4–13.8 %). The magnitude of the no-tillage treatment effect on soil aggregation, aggregate-associated SOC and TN varied with the environmental and experimental conditions. The positive effect on the proportions of LA occurred with initial soil organic matter (SOM) content >10 g kg−1, whereas SOM <10 g kg−1 did not change significantly. Additionally, the effect size of NTS compared with CTS was lower than that of NT compared with CT. These findings suggest that NTS may promote physically protective SOC accumulation through the formation of macroaggregates by reducing disturbance destruction and increasing plant-derived binding agents. The findings highlight that no-tillage may enhance the formation of soil aggregates and the associated SOC and TN concentrations in global cropland ecosystems.

Salt Ion Diffusion Behavior and Adsorption Characteristics of Fracturing Fluid in Tight Sandstone Gas Reservoir

The degree of salinity in the hydraulic fracturing rejection fluid of the Shaximiao reservoir in the central Sichuan Basin is high, and the underlying mechanism causing this salinity is not clearly understood. We evaluated the rock structure of tight sandstone, including rock composition, pore structure, ion diffusion, and adsorption behavior, to determine how the rock structure influences the mechanism of the sandstone’s interaction with the fracturing fluid. X-ray diffraction revealed that the rock mineral fraction has a significant clay mineral concentration. The results of linear swelling experiments revealed that the water sensitivity of tight sandstone reservoirs exhibits moderately robust characteristics. The time required for salt ion diffusion stabilization is much longer than that required for self-imbibition stabilization, and the diffusion of salt ions is almost log-linear with time after imbibition stabilization. The diffusion rates of salt ions were determined for different single minerals and particle sizes, with clay minerals and particle sizes controlling the diffusion rates. The samples were treated with different concentrations of KCl and acrylamide polymer solutions, and both the pore size distribution and pore throat properties were characterized by low-temperature nitrogen adsorption. Although the adsorption isotherms of both KCl and polymers are consistent with the Langmuir model, their adsorption mechanisms acting on tight sandstone and the effect of adsorption on the pore throat structure are inconsistent. The adsorption of potassium chloride enhances the rock’s pore throat diameter and permeability by increasing the uniformity of the pore throat by electrostatic adsorption with clay particles. However, polymer adsorption reduces the pore diameter of the rock and forms a thin film that obstructs the pore throat, complicating the pore throat and weakening its permeability. This research has led to a greater comprehension of the ion diffusion characteristics of the tight sandstone in the Shaximiao reservoir and the adsorption mechanism on the pore structure of the rock.

Remediation of perfluorooctanoic acid (PFOA) with nano ceramic clay: Synthesis, characterization, scale-up and regenerations

Perfluorooctanoic acid (PFOA) in the ecosystem, resulting from industrial effluent and water bodies, has attracted greater concern. An economical treatment is in demand to optimize the current issue. In this research work, Perfluorooctanoic Acid was treated from drinking water sources with nano-ceramic clay. The ceramic clay was synthesized and characterized with Fourier infrared transformation, scanning electron micrograph, transmission electron micrograph, x-ray diffraction, and thermal analysis. An adsorption process was performed in batch and continuous modes for the effective conditions for maximum removal. In batch mode 82 ± 12 nm ceramic clay particle size; 3.0 initial pH; 210 rpm agitation 1.2 mg/L PFOA concentration; 100 mg/L clay dosage; 27 °C temperature, and 20hrs experimental time shows maximum 99.15% adsorption. The experimental data is well fitted with kinetics, isotherms, and thermodynamics calculated data. In fixed bed, continuous column study 10 h treatment time, 10 cm of bed height, and 2 ml/min were adsorbed 99.99% of PFOA. The experimental data from the fixed bed adsorption equipment was correlated using a number of different mathematical models, including the Thomas, Adams-Bohart, Yoon-Nelson, and Clark models. Overall nano ceramic clay was found to potential adsorbent for Perfluorooctanoic acid removal.

Effect of particle size of zeolite clay included in high-energy diets for feedlot lambs: Growth performance, dietary energy, carcass traits, and visceral mass.

Several reports on the effects of zeolite (ZEO) inclusion in diets for feedlot lamb diets have indicated improvements in dietary energy efficiency and decreases in internal fat. Inclusion levels and the type of zeolite used have been the main focus of those reports. However, the possible effect of the zeolite particle size on the growth performance and carcass characteristics has not yet been investigated. Forty-eight male intact Pelibuey × Katahdin lambs were fed for 67 days with a high-energy diet supplemented with ZEO as follows: 1) basal diet 0% ZEO (control); 2) basal diet 3% ZEO particle size 250 µM (sieve 60); 3) basal diet 3% ZEO particle size 149 µM (sieve 100); and 4) basal diet 3% ZEO particle size 74 µM (sieve 200). ZEO replaced corn grain and soybean meal in equal parts. At the end of feeding, lambs were slaughtered, and variables such as carcass characteristics and visceral mass were evaluated. Particle size did not affect growth performance, carcass characteristics, or visceral mass. The inclusion of ZEO reduced 3.4% of dietary net energy in diets but did not affect dry matter intake or average daily gain, thus improving (p ≤ 0.05) dietary energy efficiency by 2.9%. Except for an 18.9% reduction (p = 0.02) in visceral mass fat, ZEO did not affect other carcass characteristics or visceral organ mass. The particle size studied in the present experiment has not affected any of the variables of growth performance or carcass characteristics. ZEO inclusion could be a strategy to reduce the visceral fat in finishing lambs.

Effects of Ultrasonic Oscillations on Colloidal Properties of Sulfonated Drilling Fluids

Summary The property development of drilling fluids strongly relies on the emergence of novelty additives and the formulation design of drilling fluids. Few studies focus on the influences of preparation technology on various properties of drilling fluids. At present, high-speed mechanical agitation is still the only method of formulating drilling fluids in the industrial community. In the paper, two kinds of sulfonated drilling fluids that were used frequently in China were prepared by the combination of high-power ultrasound and high-speed mechanical agitation. After the mechanical agitation, we exerted ultrasonic oscillations on the sulfonated drilling fluids and intensified the input of ultrasonic energy by increasing ultrasonic time or power. In addition, the superposition of mechanical agitation during ultrasonic oscillations could further help the sulfonated drilling fluids to absorb more ultrasonic energy when the time and power of ultrasonic oscillations remained unchanged. The effects of ultrasonic oscillations on the colloidal properties of sulfonated drilling fluids were investigated. The results show that the introduction of ultrasonic energy into sulfonated drilling fluids is able to cause the formation of thinner and denser mudcakes on borehole walls and further reduce the low temperature and low pressure (LTLP) and high temperature and high pressure (HTHP) filtrate volume. The HTHP accumulative filtrate volume within 30 minutes can be decreased by a maximum of 24.7%. Simultaneously, various Bingham-type rheological values, particularly yield point, get decreased. The ultrasonic improvement of filtration and rheological properties benefits from the formation of the stable colloidal structure of drilling fluids under acoustic cavitation. According to the total organic carbon (TOC) measurements, it is found that ultrasonic oscillations promote the adsorption of sulfonated additives on bentonite clays. The analysis of particle size and zeta potential also confirms that ultrasonic oscillations not only decrease the average clay particle size but also enhance the zeta potential absolute value. In our experimental range, all the colloidal properties acquire the continuing improvement with the increase in ultrasonic energy input, which cannot be achieved only through the high-speed mechanical agitation. Compared with our previous research works, the subject investigated in the paper is the given drilling fluid system, but not the bentonite suspension containing one single additive. It indicates that we take a step forward in the field application of ultrasound-assisted mud preparation technique.

Geotechnical Properties and Geochemical Composition of Mudrock from the Douala Sub Basin, Cameroon: Implication for Industrial Potentials

The geotechnical and compositional characteristics of mudrock deposits in the Douala Sub basin were investigated using a combination of analytical methods, including particle size distribution, Atterberg limits, mineralogical (X-ray diffraction) analyses, and whole rock geochemistry. The goal is to characterize the nature and physicochemical properties of mudrock in order to determine its applicability in industries. Grain size analysis reveals that clay-sized particles dominate the samples, with a plasticity index ranging from 6.8% to 20.67%. The mudrock materials are primarily composed of kaolinite (16.8-49.4%), quartz (15.8-68.9%), and illite (00-15.3%), which are typical of the Douala Sub- basin sedimentary environment and morphoclimatic conditions. SiO2 (42.77-73.5%) and Al2O3 (13.13-29.98%) are the most abundant oxides in the samples. Iron oxide content is moderate (1.73- 17.18%). Methylene blue values range from 1.12 to 6.95, confirming the clay content of (39.43-45.43%) and also attesting that the sediments in the study area are rich in 1:1 clay. They are suitable for ceramic applications such as (refractory bricks and tiles) and pottery due to the physicochemical parameters associated with mineralogical and geochemical data

Analysis of variance of injection moulding process parameters and clay particles size effects on impact strength, shrinkage and warpage of polyethylene/kaolin clay composites

A correlation effect between particle size of kaolin clay and injection moulding process parameters on impact strength, shrinkage and warpage of high-density polyethylene/kaolin clay (HDPE/KC) composites was carried out using analysis of variance (ANOVA). Kaolin clay with particle sizes of < 75, 75–106 and 106–150 μm was used. The process parameters that were taken into consideration were injection temperature, packing pressure and packing time. In general, experimental results showed that the impact strength and shrinkage of the HDPE/KC composites clearly depended on the injection temperature. However, no clear dependency of the warpage on the injection temperature was observed. Furthermore, clay particle size showed to have an influence only on the shrinkage of the composites, where smaller clay particle size led to injected composite parts with relatively less shrinkage. ANOVA showed that the effect of injection temperature on shrinkage of composites containing clay particle sizes of < 75 and 106–150 μm was statistically significant (p = 0.01 and 0.04, respectively). However, the effect of injection temperature on shrinkage of the composite made with clay having particle sizes of 75–106 μm was not significant (p = 0.07). ANOVA also indicated that the injection temperature effect on the impact strength of composites that contain clays with particle sizes of < 75 μm and 75–106 μm was significant (p = 0.03 and p = 0.01, respectively), whereas the injection temperature effect on the impact strength of the composite containing clay with a particle size of 106–150 μm was not significant (p = 0.17). Contrary to shrinkage and impact strength, the effect of the studied parameters on the warpage was not statistically significant, which was in good agreement with the experimental observations.

Long-term quantification of the intensity of clay-sized particles transfers due to earthworm bioturbation and eluviation/illuviation in a cultivated Luvisol

As a result of the limited knowledge on eluviation/illuviation and bioturbation rates, these two processes of soil particles translocation are qualitatively described either as synergic or competing processes. Here we take the opportunity of the recent development of an image analysis procedure to quantify illuvial clay and earthworm’s porosity to quantify the intensity of illuviation and bioturbation cumulated over soil formation in a temperate cultivated Luvisol. The key objectives of the study are i) to quantify the total intensity of illuviation and bioturbation and their depth distributions and ii) to assess the possibility for bioturbation to limit or compensate the depletion of the clay-sized fraction in topsoil horizons due to eluviation. The total quantity of illuvial clay is 1,100 t.ha−1 while the estimated annual amount of clay-sized fraction translocated by eluviation is between 0.08 and 1 t ha−1 yr−1. This is comparable to the annual loss of land by water erosion (between 1 and 5 t ha−1 yr−1) or by arable erosion (3.3 t ha−1 yr−1). Eluviation/illuviation is thus a discrete and active form of soil loss. With approximately 1,900 t.ha−1 of clay-sized fraction, the amount of fine particles displaced at least once by bioturbation is higher than the one related to eluviation/illuviation. At first sight, it therefore seems possible for biological activity to compensate for vertical transfers of the clay-sized fraction by eluviation/illuviation. However, our study shows that a considerable amount of the clay-sized fraction will never be brought up by the bioturbation and will remain definitively lost for the surface horizons as bioturbation decreases non-linearly with depth. Consequently, a preventive management of the depletion of the clay-sized fraction in topsoil horizons by eluviation/illuviation should be preferred to the curative management of its consequences by bioturbation.

Nano and sub-nano scale distribution of organic carbon species on soil particles revealed by Cs-STEM EELS

Understanding the heterogeneous distribution of soil organic matter (SOM) on soil particles is essential for predicting the stability of organic carbon (C) in soil, but direct visualization of the microscopic distribution of organic C in soil is still challenging due to the complexity of soil particles. In this study, a paddy soil was fractionated and spherical aberration corrected scanning transmission electron microscopy (Cs-STEM) coupled with electron energy loss spectroscopy (EELS) was employed to analyze the microscopic distribution of organic C species on clay-sized soil particles (<2000 nm) from the different size fractions (800–2000 nm, 100–800 nm and 0–100 nm) at the nano and sub-nano scale. The EELS results demonstrated that the relative abundance of both phenolic and aliphatic C was quite independent of the particle size fractions, while aromatic and carboxyl carbon demonstrated the largest variations between fractions. With the decrease in soil particle size from 800 to 2000 nm to 0–100 nm, the median abundance of carboxyl (oxidized) C increased from 23% to 35%, and aromatic (reduced) C decreased accordingly from 40% to 16%. The statistical analysis demonstrated that the local organic C concentration was the major factor accounting for the variations in oxidized and reduced C species in soil particles, in which selective sorption of the organic C abundant of acidic functional groups by reactive minerals was responsible for the enrichment of oxidized C in small clay size soil particles. Overall, the results of this study contribute to an improved understanding of the chemical diversity of SOM in organo-mineral interfaces and provide insights in the microscopic C stabilization mechanisms in natural soils.

Relationship between the size composition observed from the photosedimention technique and chromaticity of the fine-grained surface sediments from the modern lakes, Songnen Plain

The relationship between clay particle size in fine-grained sediments and the enrichment of organic matter and the redox degree of their environment is conducive to the judgment and evaluation of the hydrocarbon generation potential of fine-grained sediments. The grain size characteristics of clay particles in the surface fine-grained sediments of Chaersen lake, Delong lake, Hongyuan lake, Lamasi lake, and Zhongnei lake in Songnen Plain are revealed by light sedimentation method. On the basis of the test, the relationship between the particle size of clay particles and the sediment chromaticity is analyzed, and the directivity of chromaticity to the content of organic matter and redox degree of fine-grained sediments is used for the organic content estimation. It is confirmed that the particle size of clay is negatively correlated with its organic matter content and positively correlated with its redox degree. This has important reference significance for discussing the hydrocarbon generation potential and evaluation of Cretaceous lacustrine fine-grained source rocks in the Songliao Basin.

Nano-laponite/polymer composite as filtration reducer on water-based drilling fluid and mechanism study.

In drilling deep complex formations, most drilling fluid additives have insufficient temperature and salt tolerance, resulting in the decline of drilling fluid performance. This study used 2-acrylamide-2-methylpropane sulfonic acid, acrylamide, dimethyl diallyl ammonium chloride and modified nano-laponite to synthesize a nanocomposite filtrate reducer (ANDP) with excellent temperature and salt resistance, which can maintain the performance of drilling fluid. The structure of ANDP was analysed by a transmission electron microscope and an infrared spectrometer. The thermal stability of ANDP was studied by thermogravimetric analysis. The performance of ANDP was evaluated in a water-based drilling fluid. The mechanism was analysed per clay particle size distribution, Zeta potential, filter cake permeability and scanning electron microscopy imaging. The results show that ANDP has good thermal stability and the expected molecular structure. The filtration of freshwater drilling fluid after ageing at 200°C is 10.4 ml and that of saturated brine drilling fluid is 6.4 ml after ageing at 150°C. Mechanism analysis suggests that the ANDP increases the thickness of clay particle hydration layer and maintains the colloidal stability of the drilling fluid. ANDP inhibits the agglomeration of clay particles and significantly reduces the filtration by forming dense mud cake.

Soil wind erosion resistance analysis for soft rock and sand compound soil: A case study for the Mu Us Sandy Land, China

Abstract Mixtures of soft rock and sand have been applied extensively in the Mu Us Sandy Land (MUSL, also known as the Mu Us Desert) to limit the loss of top soil by wind erosion. In this study, the efficacy of sand-fixing technology was investigated in a series of experiments. The sand-fixing effect of seven different mixtures (ratios) on soft rock and sand was evaluated in a wind tunnel. The results indicated that the MUSL soils are susceptible to wind erosion, as the textural composition of sand is dominated by coarse particles. MUSL soils dominated by silt and clay particle sizes are more resistant to wind erosion. Each soft rock and sand combination experiences severe wind erosion. However, wind erosion was significantly reduced when soft rock and sand were mixed. An increase in particle size was associated with an increase in the resistance of soft rock and sand mixtures to wind erosion. The ability to resist wind erosion was greatest when the ratio of soft rock and sand was between 1:2 and 1:5. This study provided data to support the approaches to sand-fixing commonly used at present in the MUSL. The results of this study have important practical significance for the improvement of agricultural land potential in dry sandy areas.

Remediation of Spent Vegetable Tannins from Waste Tanning Liquor through Coagulation and Ultrasound Pre-Treatment

Vegetable tanning is one of the oldest methods of tanning. Vegetable tannins present in spent tanning liquor necessitates suitable remediation measures for sustainable solution. Vegetable tanning agent, wattle extract powder and vegetable tanning process spent liquor collected from a commercial tannery were used for the experiments. In the present approach, natural clay has been employed for the coagulation of spent vegetable tannins. Various other suitable precipitating agents such as zinc chloride (ZnCl2), barium chloride (BaCl2), ferric alum, lime and poly-electrolyte have also been studied for their efficacy in the treatment process and their requirement optimized. The efficacy of coagulation was monitored through settling characteristics of precipitation process and % settled volume for a given time. In the case of wattle powder, better settling of tannins was obtained due to combined use of optimized amount of clay and ZnCl2. Whereas, ultrasound pre-treatment provided further enhancement. In the case of spent tannery vegetable tanning liquor, ultrasound pre-treatment of polyelectrolyte along with optimized amount of normal lime, clay and ferric alum provided rapid settling behavior, with steady state achieved in 20 minutes with settled volume of ~10 ml. Similar trend was also achieved (10 ml, 8 min.) for ultrasound pre-treated optimized clay with the use of other agents as normal. There was a significant reduction in particle size of clay (from 539 nm to 298 nm) through ultrasound pre-treatment (20 min.), leading to more surface area facilitating the coagulation process. This method could be useful for remediation of vegetable tannins present in spent vegetable tanning liquors using available natural material clay and shall also be extended to other streams. The present study has explored the ultrasound assisted coagulation science and technology for remediation of wastewater in general, whereas, spent vegetable tanning liquor in specific.

C:N ratios of bulk soils and particle-size fractions: Global trends and major drivers

C:N ratios are the most ancillary and available proxy for soil organic matter (SOM) chemical composition and quality in the literature, but there is surprising little information on how it is affected by environmental factors. To address this knowledge gap, we searched the global literature and gathered information from 74 studies conducted between 1980 and 2019, covering 29 countries and a wide range of variation environmental settings. We compiled data on soil organic carbon (SOC), total N (TN) and C:N ratios in bulk soil and, for the first time, within soil particle-size fractions – sand, silt, and clay. Correlation and random forest statistical analyses showed that SOC and TN contents were mostly controlled by macroscale, climatic drivers, namely temperature and precipitation, whereas soil C:N ratios were more responsive to microscale drivers, e.g. soil particle-size distribution. Specifically, C:N ratios in bulk soil were most strongly correlated with sand contents (r = 0.52; p < 0.001), consistent with the high C:N of sand-sized SOM (median 16.7). Otherwise, clay-sized SOM showed much less variation in C:N ratios (5.0–17.6, median 9.6), regardless of sampling depth and land use. Clay C:N ratios were only consistently lower under arid climate types. Silt-sized SOM showed intermediate C:N ratios (median 13.1) relative to sand and clay-sized fractions. Hence, our results suggest a preferential immobilization of N-enriched SOM onto clay-sized particles coupled to a segregation of N-depleted SOM in sand-sized fractions. Although bulk soil C:N increased with sand contents, the accumulation of N-depleted SOM within sand-sized fractions increased with clay content. Overall, by identifying the complementarity of macro- and microscale factors underpinning soil C and N pools and their C:N ratios, our results contribute to reduce the inherent complexity to model SOM cycling across global to local scales.

Evaluation of Soil Characteristics for Agricultural Machinery Management and Cropping Requirements in AL Aflaj Oasis, Saudi Arabia

Saudi Arabia’s topographic features have great significance and impact on the diversity of physical environments for plant growth and agricultural activities. Cultivated land is at a premium in Saudi Arabia, and soil evaluation is increasingly important. Thus, the intended purpose of this investigation was to determine both the genesis and soil properties to improve the management of arid soil, which is represented by Al-Aflaj Oasis, during tillage operations. The parameters of this research output were the soil’s chemical and physical properties. Data were collected from field experiments by drilling and evaluating soil profiles using soil sampling tools. This study classified the soil of Al Aflaj Oasis, which is a part of the Najd Plateau. It analyzed the soil profile, the failure to provide nutrients for agricultural production, and the impact of spring floods, modern equipment, fertilizer management, and irrigation methods on agricultural prospects. Topographic and geological maps provided the origin of the soils in the area. The morphological description included measurements and characterization of soil horizons and boundaries, moisture status, soil texture, construction, cohesion, estimation of calcium carbonate, and other morphological phenomena. Laboratory analysis measured the soil particle size, soluble salts, calcium carbonate, organic material, electrical conductivity, and percentages of silt, clay, and sand. The soil was deep, with a coarse texture characterized as sandy to sandy clay; the gravel content ranged from 19.70 to 62.50%, with a cohesive structure at the bottom of the soil profile and slight cohesion at the surface. The soil had low organic matter content, and a hard layer of calcium existed at a depth of 100 cm. The soil was classified as arable land within a subgroup of Typic Haplocalcids. Chemical analysis showed low salinity, slight alkalinity, and high calcium carbonate (22–64%). The soil underwent a historical transformation. To enhance agricultural potential, the chemical and physical properties need adjustment by introducing organic matter, intensive deep cultivation, diversification of agricultural fertilizers, and careful irrigation management. Since recent cultivation has been limited to a depth of 100 cm, the hard calcium carbonate layer should be considered carefully. Future crop cultivation should include deep plowing (e.g., chisel and furrow plows) to fragment the solid soil structure and facilitate suitable farming practices, and the growth of plants in the lands affected by the ancient overflows of the Al Aflaj springs, such as the Al Aflaj Oasis, can be made productive and consistent with other agricultural areas.

Enhanced Bentonite/PVA Matrix for Advanced Shielding Applications

The shielding characteristics of natural bentonite can be enhanced based on calcination and ball-milling processes for protection against gamma radiation. The calcination process increases the content of the oxide, which enhances the mass attenuation coefficient; however, the elimination of water and organic matter from bentonite clay structures increases the particle size, where large particle size has a negative effect on this mass attenuation coefficient. Therefore, the calcinated bentonite has been ball-milled to reduce the particle size and improve the attenuation properties of natural bentonite. Furthermore, the calcination process occurs at 700°C for 2 h because dehydration is completed above 500°C while dehydroxylation is observed at 700°C. Therefore, the shielding parameters have been determined for calcinated, ball-milled, pressed bentonite clay samples according to different gamma-ray energies (662, 1173, and 1332 keV), where the experimental setup is based on narrow beam transmission techniques with two sources (137Cs and 60Co). In addition, the particle size of bentonite clay has been characterized using X-ray diffraction patterns depending on two different methods: dynamic light scattering and Williamson-Hall size analyses. This study shows that the calcinated, ball-milled bentonite pressed at 150 bar has the highest linear and mass attenuation coefficients of μ = 0.13 cm−1 and μm = 0.082 cm2/gm, respectively. Moreover, the experimental and theoretical investigation of the mass attenuation coefficient is in good agreement.

Hydrothermal metalliferous sediments in Red Sea deeps: Formation, characterization and properties

Sediment accumulations within the Red Sea central deeps have unique genesis and properties. We piece together available information to understand their geological setting and formation history, and conduct an extensive sediment characterization study to assess their geotechnical properties in order to anticipate engineering/mining implications. The various sediment columns reflect slow-rate background sedimentation (biogenic and detrital particles – Valdivia deep) and hydrothermal metalliferous sediments that nucleate and grow within the overlying brine pools (primarily in the Atlantis II, as well as in the Wando deep, and to a lesser extent in Discovery deep). All sediments are fine-grained silt and clay-size particles; smaller particles tend to have higher specific gravity and define the metalliferous content. Hydrothermal sediments exhibit extreme properties when compared to sediments worldwide: they have uncharacteristically large maximum void ratio and compressibility, and their self-compaction is very different from background Red Sea sediments. Their unique self-compaction trends have a strong effect on remote acoustic characterization and sampling, and must be carefully accounted for during field studies and resource assessment. Three distinct properties of hydrothermal metalliferous sediments are relevant for separation and enrichment: high specific surface area, high specific gravity, and ferromagnetic signature. Small grains and low-density flocs have low terminal Stokes' velocities and their residency times may be extended in convective stratified brine pools; this observation affects the environmental analysis of mining operations and tailings disposal.

A proposed framework for assigning soil drainage classes to non-redoximorphic soils in the Canadian System of Soil Classification

Drainage refers to the frequency and duration of periods of saturation, and how quickly excess water is removed from the soil profile. It is one of the central concepts used to differentiate soil series within the Canadian System of Soil Classification (CSSC). Currently, seven drainage classes are recognized in the CSSC: very rapid, rapid, well, moderately well, imperfect, poor, and very poor. In redoximorphic soils (imperfect, poor, and very poor drainage classes), drainage is typically differentiated based on morphological features (i.e., the presence of gleying and mottles). Non-redoximorphic soils (very rapid, rapid, and well-drained classes) do not display such morphological features but are differentiated based on available water holding capacity (AWHC) as inferred from soil texture and particle size. Moderately well-drained soils are intermediate, in some cases defined by the presence of redoximorphic characteristics, but in other cases inferred based on texture. In effect, drainage in materials without redoximorphic features is estimated based on AWHC as related to texture class, which should include sand subfractions. Values for AWHC were calculated using a published pedotransfer function for combinations of sand, silt, and clay-sized particles, including various combinations of very fine to very coarse sand separates as input. Calculated values were compared with currently assigned drainage classes and several inconsistencies were identified. Revisions are proposed to textural assessment of soil drainage for non-redoximorphic soils.

Low-dimensional physics of clay particle size distribution and layer ordering

Clays are known for their small particle sizes and complex layer stacking. We show here that the limited dimension of clay particles arises from the lack of long-range order in low-dimensional systems. Because of its weak interlayer interaction, a clay mineral can be treated as two separate low-dimensional systems: a 2D system for individual phyllosilicate layers and a quasi-1D system for layer stacking. The layer stacking or ordering in an interstratified clay can be described by a 1D Ising model while the limited extension of individual phyllosilicate layers can be related to a 2D Berezinskii–Kosterlitz–Thouless transition. This treatment allows for a systematic prediction of clay particle size distributions and layer stacking as controlled by the physical and chemical conditions for mineral growth and transformation. Clay minerals provide a useful model system for studying a transition from a 1D to 3D system in crystal growth and for a nanoscale structural manipulation of a general type of layered materials.

Insights into the high temperature-induced failure mechanism of bentonite in drilling fluid

Designing ultrahigh-temperature water-based drilling fluid for an ultra-deep well is a long-standing critical technical problem. Unraveling the failure mechanism of clay in the drilling fluid at ultrahigh temperatures harbors tremendous scientific and industrial significance. Herein, the high-temperature failure mechanism was elucidated by molecular dynamics (MD) simulation, the multi-characterizations (e.g., XPS, Zeta potential, XRD, SEM, Contact angle, and FT-IR) together with the rheology and filtration experiments. It was found that high temperature could destroy the layered structure of clay in the drilling fluid, leading to reduction of aluminum element and hydroxyl species on its surface, thus reducing the amount of negative electricity of clay and its hydrophilicity. As a result, the size of the clay particle in the drilling fluid increased, and the as-formed filter cake was thicker and looser. Furthermore, the rheology and fluid loss performance of the drilling fluid degraded or disrupted. When the temperature increased from 25 to 200 °C, the amount of hydroxyl group on the surface of the clay reduced by 45%. Moreover, the median size of clay particles increased by 2.7 times and the fluid loss increased by 1.6 times. The insights and methodology reported here shed new light on the fundamental understanding of failure mechanism in drilling fluid and may pave the way for improving the efficiency of drilling fluid at high temperature.