Sedimentation Stability Research Articles

Analysis of aggregation and sedimentation stability of process slurries

Analysis of aggregation and sedimentation stability of process slurries

LUBRICANTS FOR THE MANUFACTURE OF SAND-SMOOTHED RODS BY HYDRAULIC TOOLING

The article presents the results of research on the development of the lubricant composition for the production of sand-resin rods over a heated tooling with high technological and consumer properties. It has been established that the conditional viscosity of the developed lubricant compositions decreases when oleic acid is added to the polymethylsiloxane liquid in an amount of 5 to 25% from 10 to 8 s, and the density of lubricants is reduced from 908 to 882 kg/m3. It has been established that when oleic acid is added to the base in an amount of 15%, the sedimentation stability of the lubricant is increased by more than 30 times. It is shown that the developed lubricant composition has the best lubrication characteristics at the following component ratio: base (polymethylsiloxane liquid PMS 300) – 15%, additive (oleic acid) – 15%, surfactant – 3,0%, water – the rest. The results of the research can be used by the process engineers when choosing the composition of the lubricant for making rods by the heated tooling.

Elemental Analysis of Copper-Zinc Ores by Total Reflection X-Ray Fluorescence using Nonaqueous Suspensions

ABSTRACTNovel rapid determination of copper-zinc ore elemental composition by total reflection X-ray fluorescence (TXRF) is proposed. Approaches for solid state sample analysis by TXRF are provided. The sample preparation is chosen to obtain the suspensions in ethylene glycol. The optimum suspension preparation conditions (sample mass, volume of dispersion medium) and the measurement conditions (internal standard element, spectra acquisition time) were determined. The sedimentation stability of suspensions was studied. It was found that the suspensions remain stable for approximately 2 min, which is sufficiently long for the sampling the suspension. The proposed technique allows determining the elemental composition of solid ore samples without sample digestion. The sample preparation time takes approximately 20 min. The relative standard deviation of the analytical results did not exceed 10%.

Quantifying biostabilisation effects of biofilm-secreted and extracted extracellular polymeric substances (EPSs) on sandy substrate

Abstract. Microbial assemblages (“biofilms”) preferentially develop at water–sediment interfaces and are known to have a considerable influence on sediment stability and erodibility. There is potential for significant impacts on sediment transport and morphodynamics, and hence on the longer-term evolution of coastal and fluvial environments. However, the biostabilisation effects remain poorly understood and quantified due to the inherent complexity of biofilms and the large spatial and temporal (i.e. seasonality) variations involved. Here, we use controlled laboratory tests to systematically quantify the effects of natural biofilm colonisation as well as extracted extracellular polymeric substances (EPSs) on sediment stability. Extracted EPSs may be useful to simulate biofilm-mediated biostabilisation and potentially provide a method of speeding up timescales of physical modelling experiments investigating biostabilisation effects. We find a mean biostabilisation effect due to natural biofilm colonisation and development of almost 4 times that of the uncolonised sand. The presented cumulative probability distribution of measured critical threshold for erosion of colonised sand reflects the large spatial and temporal variations generally seen in natural biostabilised environments. For identical sand, engineered sediment stability from the addition of extracted EPSs compares well across the measured range of the critical threshold for erosion and behaves in a linear and predictable fashion. Yet, the effectiveness of extracted EPSs to stabilise sediment is sensitive to the preparation procedure, time after application and environmental conditions such as salinity, pH and temperature. These findings are expected to improve biophysical experimental models in fluvial and coastal environments and provide much-needed quantification of biostabilisation to improve predictions of sediment dynamics in aquatic ecosystems.

Sea scallops exhibit strong local spatiotemporal structure associated with seabed stability and high flows

AbstractSea scallops (Placopecten magellanicus) live along the Northwest Atlantic continental shelf and are aggregated over a broad range of spatial scales (m2–105 km2). However, little is known about the spatial distribution of local scallop neighborhoods, the scale at which spawning, intra‐specific competition, and predator–prey interactions occur. We surveyed 30,995 km2 of Georges Bank and the Great South Channel annually from 2003 to 2010 counting the number of scallops in 54,016 locally replicated 3.24‐m2 quadrats with underwater video. There were about 4 billion scallops occupying 11,200 km2 of the study area in concentrations from 1 to 41 scallops per scallop. Scallop spatial distribution switched from dispersed to aggregated at a concentration of 3–4 scallops in every year. High concentrations (>3) occurred in 11% but were only persistent in 4% (449 km2) of scallop habitat. There were 13 persistent high‐concentration aggregations (7–217 km2), and all but two occurred on gravel‐dominated sediments left by prehistoric glacial retreat. Model‐derived benthic boundary shear stresses in the persistent aggregations averaged two times higher than in scallop habitat, but the seabed was about two times more stable because it had significantly less sand and more granule–pebble and cobble sediment. The area occupied by scallops each year varied little (9%) despite a 49% increase in total scallop abundance between 2005 and 2007, suggesting Georges Bank scallops have a proportional density population structure. Most scallops occurred alone or at low concentrations (≤2) where fertilization success is probably poor. The persistent high‐concentration aggregations we identified may be critical for successful reproduction and sustainable harvest. Observing organisms at scales corresponding to their individual interactions reveals important processes shaping their landscape‐scale spatiotemporal distributions. These processes are obscured by the methods typically employed to estimate abundances of commercial fishery species. The spatiotemporal structure of sea scallop distribution has important implications for the design of abundance surveys and the assumptions underlying stock assessment methods. These should be investigated. Finally, this work suggests that natural disturbance (sediment stability) may play a substantial role in shaping spatiotemporal distributions and dynamics of benthic marine populations.

Magneto-optical properties of binar ferrocolloids

In this work, a new method for increasing optical anisotropy of a ferrocolloid through introducing the coiled polymer molecules or elongated nanosized non-magnetic particles is realized. Since the dimensions of structural elements comprising such a binary colloidal solution are small compared to the wavelength, the ferrocolloid remains optically homogeneous. Type I binary ferrocolloids are obtained by introducing polybutadiene molecules into a magnetic fluid (magnetite + kerosene + oleic acid). In this case, an increase in the double refraction (DR) is due to the deformation and stretching of the polymer coils along the magnetic field. In weak fields, double amplification of the signal was detected for the concentration of polymer molecules of about 0.5 %. A further increase in the concentration of impurity molecules weakens DR due to a disturbance of the sedimentation stability of the solution and precipitation of colloidal particles. Type II binary solution is synthesized on the basis of a magnetic fluid and rod-shaped impurity nanoparticles of goethite ( αFeOOH). The transverse dimension of the impurity particles (10 − 30 nm) was close to the average diameter of single-domain magnetite particles, and the longitudinal dimension was an order of magnitude larger. An increase in the DR occurs due to the orientation of long axes of impurity particles along the magnetic field caused by the difference in the ”demagnetizing” coefficients along and across the axis of the particle. The magnetic double refraction has been studied depending on the concentration of magnetite and impurity particles and the strength of the magnetic field. For the first time, an experimental substantiation of the multiple amplification of the DR signal by impurity particles was obtained. In the fields (up to 10 kA/m) and for the volume fraction of impurity particles of the order of one percent, the DR signal is amplified by more than an order of magnitude. In stronger fields, the signal gain, associated with the influence of impurity particles, reaches saturation and, with further increase in the field strength, remains practically unchanged, while the total anisotropy of the solution continues to increase due to the orientation of the magnetite particles.

A three-step sensory-based approach to maximize consumer acceptability for new low-sugar licorice-chocolate-flavored milk drink

Licorice has many functional characteristics. The present study aimed to 1) develop a new flavored dairy beverage containing licorice extract powder (LEP) and cocoa powder (CP); 2) maximize the consumer acceptability of the beverage, using a three-step sensory-based approach, and 3) verify the physicochemical and microbial stability of the beverage during refrigerated storage. In the first step, 16 formulae containing four CP:LEP ratios (0.85:0.15, 0.70:0.30, 0.55:0.45, 0.40:0.60) and four sucrose levels (2, 4, 6, 8 g 100 g−1), and a control sample (chocolate milk), were evaluated by a liking test. Second, the three formulations that obtained the highest liking scores were assessed, using a preference ranking test. Third, a second liking test was performed on the significantly most preferred formulation (CP:LEP, 0.70:0.30; sucrose, 6 g 100 g−1) and three of its variants. Based on the sensory results, the milk drink was optimized at 0.65:0.35 CP:LEP and 5% sugar. During 14 days at 4 °C, the optimum drink formula showed no significant changes in acidity, pH and microbial growth and a significantly higher color and sedimentation stability than the control. Consequently, licorice showed promising potential to be used in the formulation of acceptable functional milk products, such as low-sugar flavored drinks.

Early structural stability of fine dam sediment in soil construction

PURPOSE: Fine sediments accumulate upstream of hydroelectric dams. To ensure that dams can operate properly, most sediments are returned downstream reaches, but a portion of them have to be dredged and land managed. In parallel, using topsoil from agricultural parcels for urban greening is currently controversial because arable surface areas are decreasing. An alternative idea for protecting these natural resources consists in reusing fine dredged sediment to construct functional soils. The agronomical use of fine dredged sediment raises the question of its ability to provide acceptable physical properties for plant growth. MATERIALS AND METHODS: Six dredged sediments with contrasted initial agronomical properties were mixed or not with green waste compost and submitted or not to drying-wetting cycles in a 105-day-long experiment under greenhouse conditions. The sediments were analyzed for their capacity to generate stable aggregates. We measured the proportion of macro aggregates > 2 mm with dry-sieved aggregate (DSA) fraction and the > 0.25 mm water-stable aggregate (WSA) fraction for each treatment over time. We also assessed the main sediment physicochemical properties, microbial biomass carbon, and carbon mineralization potential. RESULTS AND DISCUSSION: Compost addition (40% in volume) enhanced the WSA fraction of the low-organic-matter-content sediments (< 30 g kg⁻¹), whereas it had a non-significant effect in the other sediments. Multiple linear regressions highlighted a determining role of organic matter in the WSA fraction. At this scale of aggregation, organic matter seemed to mainly interact with clay in an acidic context. Compost addition had either no significant effect or a negative effect on the DSA fraction. Multiple linear regressions suggested that organic matter was not clearly involved in DSA formation in the sediment, whereas macro-porosity was. The first drying-wetting cycles enhanced the DSA proportion of the sediments, but the following cycles had a negative effect. We suggest that disaggregating mechanisms gradually predominated over aggregating mechanisms over time. CONCLUSIONS: All sediments showed acceptable physicochemical properties for plant growth. WSA formation in low-organic-matter-content sediments was improved by adding compost. Drying-wetting cycles had a controversial effect on DSA formation, and only the very first cycles had a beneficial effect on macro-aggregation. The mechanisms involved in aggregation and aggregate stability in soil constructed from sediments seem to be similar to those involved in natural soils. That is why we propose that the soil hierarchical aggregation model initially developed for natural and cultivated soils could be adapted to sediments.

A systematical study of the overall influence of carbon allotrope additives on performance, stability and redispersibility of magnetorheological fluids

To this date many different additives have been used in order to stabilize the magnetorheological fluids or to enhance their performance, but their ranking in terms of the efficiency is still lacking. To design the efficient magnetorheological fluid it is necessary to analyse the overall effects of the additives on its complex behavior. In this study, carbon allotropes – fullerene powder, carbon nanotubes, graphene nanoplatelets – were added into the carbonyl iron-based magnetorheological fluids to examine their effect on stability and utility properties. The magnetorheological behavior of designed mixtures was investigated and obtained experimental data were numerically evaluated using the Robertson–Stiff model. While the fine fullerene powder acted as a gap-filler reinforcing field-induced structures, the other additives employed rather disrupted the microstructure during the shear. The role of the additives during the formation of field-induced structures was pointed out. The sedimentation stability was examined using Turbiscan analyzer as well as by direct observation method. Both approaches revealed that the carbon nanotubes possessed the highest stabilization effect. They also most effectively prevented packing the iron microparticles into a stiff sediment as was confirmed via redispersibility measurements.

Understanding the conditionality of ecosystem services: The effect of tidal flat morphology and oyster reef characteristics on sediment stabilization by oyster reefs

Ecosystem-based coastal protection by means of conserving, restoring or creating intertidal ecosystems that attenuate waves and stabilize shorelines, offers a promising way to climate proof coastlines for the future. The Pacific oyster (Crassostrea gigas) is an ecosystem engineering species, which is known for its wave attenuating and sediment trapping ecosystem services, but it remains unknown to which extent this is conditional. We aim to test the hypothesis that the ecosystem engineering effect concerning sediment trapping and stability by oyster reefs is conditional, and can be predicted based on i) local physical forcing, ii) morphological characteristics of the tidal flat, and iii) biological characteristics of the oyster reef.Analyses of long-term sediment accretion patterns on natural intertidal oyster reefs at the Oosterschelde basin (The Netherlands) showed that this ecosystem engineering effect is strongest on tidal flats under erosional conditions, lower aspect ratio (i.e., relative long and narrow reefs), relatively closed reefs (i.e., few open patches) and higher coverage of oysters within reef patches. The ability of C. gigas to shape the environment thus depends both on biotic and abiotic conditions, meaning that oyster reefs only work under specific conditions for erosion control. Overall, our results provide baseline understanding for ecosystem management aimed at affecting sediment dynamics, thereby contributing to a better understanding for designing ecosystem-based solutions under different abiotic and biotic conditions. In addition, present study provides a clear example of how we need to gain a better understanding of the conditionality of ecosystem services in general, to be able to create and restore ecosystems for obtaining their services.

Investigation the stability of reservoir sediments in the lab and field

To investigate the erosion stability of reservoir sediments, two measuring strategies were applied. Next to in situ measurements, sediment cores were extracted and analysed in the laboratory. At several sampling points at a reservoir in Germany, the in situ device was used to determine the critical bed shear stresses at the sediment surface. At the same time, sediment cores were withdrawn at each site to perform depth-orientated investigations in the hydraulic laboratory. The objective of this study is to investigate the remobilisation potential of the deposited fine sediments and to compare different methods to determine the erosion threshold. Next to critical shear stresses and erosion rates, additional sedimentary and biological parameters were examined such as bulk densities, particle size distributions, TOC-contents and chlorophylla concentrations. The results show generally a very low erosion stability, especially at the sediment surface and in the upper sediment layers. Deeper sediment layers are characterised by consolidation effects and show a higher erosion resistance. High clay contents result in increased stability while high sand contents show a high remobilisation potential. No significant relation to the parameters TOC-content or chlorophylla concentration are identified. A comparison between the different applied techniques to determine the critical bed shear stresses reveals values in the same order of magnitude; however, some significant variations occur because of different hydromorphological conditions and the different limitations for each device.

Effect of Surfactant HLB Value on Settlement Stability of Magnetorheological Fluid

The hydrophilic-hydrophobic balance (HLB) of surfactants has a great influ-ence on surfactants. Among them, polyethylene glycol has an HLB value of 20 and is highly hydrophilic; oleic acid has an HLB value of 1, which is very lipophilic; and sodium dodecylbenzenesulfonate has an HLB value of 10.6 be-tween the two. This paper explores the use of these three surfactants with typi-cal HLB values to improve the performance of magnetorheological fluids, mainly to study its effect on the stability of magnetorheological fluids. Tests have shown that the use of lipophilic surfactants in oil-based magnetorheologi-cal fluids has better sedimentation stability than the use of hydrophilic surfac-tants.

Improvement of Cement Properties Using a Single Multi-functional Polymer

Cementing of the casing pipes inside the wellbore is considered as one of the most expensive and difficult operations during the well construction process. A low quality cementing job leads to further repair operations, which are usually costly and time-consuming to conduct. Polymer cements are being used for decades in the oil and gas industry due to their improved properties such as sedimentation stability, flexural strength and adhesion. Furthermore, these cements are characterized by improved pore structure, decreased slurry density, decreased porosity and controllable rheological parameters. In this research, a single domestic polymer is added as a cement modifying agent. Domestic additive are easier to buy in the market and are usually cheaper than the imported additives. In addition, using a single additive leads to a simplified logistics operation. Results of the experimental investigations on the main properties of the developed cement systems show that using the proposed polymer in the proper concentration leads to an optimum flow-ability and pump-ability of the slurry, reduced cement water loss, increased strength characteristics and improved adhesion properties of the set cement.

红壤坡面土壤团聚体特性与侵蚀泥沙的相关性

PDF HTML阅读 XML下载 导出引用 引用提醒 红壤坡面土壤团聚体特性与侵蚀泥沙的相关性 DOI: 10.5846/stxb201611112299 作者: 作者单位: 浙江大学环境与资源学院,浙江大学环境与资源学院,浙江大学环境与资源学院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（41471221） The relationship between soil aggregates and eroded sediments from sloping vegetated red soils of South China Author: Affiliation: College of Environmental and Resource Sciences,Zhejiang University,Zhejiang Provincial Key Laboratory of Agricultural Resources and Environment,College of Environmental and Resource Sciences,Zhejiang University,Zhejiang Provincial Key Laboratory of Agricultural Resources and Environment,College of Environmental and Resource Sciences,Zhejiang University,Zhejiang Provincial Key Laboratory of Agricultural Resources and Environment Fund Project: National Natural Science Foundation of China [grant number 41471221] 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:借助室内人工模拟降雨试验为研究手段，以强降雨过程中红壤丘陵区坡菜地侵蚀泥沙颗粒组成及土壤团聚体稳定性变化特征与规律为研究目的，分别在不同坡长（2，3，4m）、不同植被覆盖度（0，30%，60%，90%）条件下进行了有效模拟降雨试验共计12场次，每场次降雨试验的产流历时设计为30min，固定雨强为2.0mm/min。试验结果表明：1）侵蚀泥沙中颗粒粒径以 < 2μm粘粒和2-20μm细粉粒为主。在原土中，粘粒（0-2μm）和细粉粒（2-20μm）含量之和占总量的43.92%，在泥沙中粘粒和细粉粒之和占总量的约57.08%，均出现不同程度的增加；2）在不同处理中，坡面土壤 > 1mm干筛法团聚体含量明显大于湿筛团聚体（ > 1mm）的含量，可认为水稳性团聚体的含量更能作为衡量土壤结构的稳定性的指标。 > 0.25mm团聚体分散度（PAD0.25）和 > 2mm团聚体分散度（PAD2）含量均出现增大，而 > 0.25mm水稳性团聚体含量（WAS0.25）减少，植被覆盖度对土壤团聚体稳定性影响明显强于坡长；3）WAS0.25含量是影响侵蚀泥沙的颗粒粒径分布的主要因素，随着坡面土壤中WAS0.25的增加，侵蚀泥沙的平均重量直径逐渐降低。同时，泥沙颗粒平均直径与土壤团聚体平均重量直径（MWD团聚体）含量呈极显著负相关，可知坡面大团聚体越稳定，坡面土壤的粗化过程越不易形成。 Abstract:Soil erosion is a serious problem that has significant environmental impacts, including declines in soil quality, sedimentation of reservoirs, and nonpoint source water pollution. Thus, it is important to study soil erodibility and mechanisms for nutrient loss on sloping land. Plenty of studies have researched soil erosion factors, such as land use patterns, plant cover type and ratio, slope length and gradient, rainfall intensity and amount, and raindrop kinetic energy; these studies have been key to characterizing these processes. It is generally recognized that plant cover and slope length have a significant impact on soil erosion and nutrient loss. However, these parameters have often been studied in isolation, and few have researched the combined effects of sedimentation and nutrient loss. In this study, we analyzed the effects of slope length and plant cover ratio on the particle size distributions (PSDs) of soil and eroded sediments from sloping vegetated fields under heavy rainfall. We evaluated the change in soil aggregate stability characteristics to explain the relationship between PSDs of the eroded sediment and soil aggregate stability. Twelve simulated rainfall experiments were conducted in a glasshouse with a rainfall intensity of 2mm/min and runoff was produced within 30min. For this study, we implemented three slope lengths, 2, 3, and 4m, and four levels of vegetation cover ratios, 0, 30%, 60%, and 90%, in 2014 and 2015. The micropipette method was used for particle size analysis of soils and eroded sediments. Surface soil samples before and after rainfall were separated into five soil aggregate sizes, > 2mm, 1-2 mm, 0.5-1mm, 0.25-0.5mm, and < 0.25mm, by dry sieving and wet sieving. The experimental indexes to evaluate soil aggregate stability included water stable aggregates (WSA), mean weight diameter (MWD), and dispersion degree of soil aggregate (PAD). The results showed that clay particles ( < 2μm) and fine silt particles (2-20μm) were the main size fractions in eroded sediments. Surface runoff, which causes soil erosion, is a selective transport process; hence, there were more clay particles and fine silt particles in the eroded sediments (approximately 57.08%) than in the original soils (43.92%). The proportion of clay particles in the eroded sediment increased slightly as the vegetation cover ratio increased. There were no significant differences in PSDs of eroded sediments for different slope lengths with the same cover ratio (P > 0.05). The content of > 2mm and > 0.25mm PAD (PAD0.25, PAD2) increased, whereas the content of > 0.25mm WSA (WSA0.25) decreased after rainfall. Vegetation cover ratio had a more significant effect on > 0.25mm soil aggregate stability than did slope length. We found that the WSA index generally reflected the difference in soil structure stability. WSA0.25 was the main factor affecting PSDs of eroded sediments; the MWD content of the eroded sediments decreased gradually whereas WSA0.25 content increased. We also found a significant negative correlation between PSDs of eroded sediment and MWD of soil aggregate. Finally, we observed that more stable soil macro-aggregates resulted in less coarse soil surfaces. 参考文献 相似文献 引证文献

In Ukrainian

The investigation results are shown directed onto development of the concept of creation of magnetosensitive nanocomposites (NC) with multilevel hierarchical nanoarchitecture and functions of biomedical nanorobots. We synthesized nanosized magnetite in monodomain state and magnetosensitive NC based on that (Fe3O4/dimercaptosuccinic acid (DMSA), Fe3O4/γ-aminopropylsiloxane (γ-APS), Fe3O4/polyacrylamide (PAA), Fe3O4/hydroxyapatite (HA), Fe3O4/SiO2, Fe3O4/TiO2, Fe3O4/Al2О3). Isotherms and adsorption kinetics of cisplatin were studied depending on chemical nature of the surface of nanostructures. Adsorption of doxorubicin (DOX) onto the surface of Fe3O4/HА NC from solution in physiological liquid was studied. Magnetic fluids containing Fe3O4/HА/DOX NC were produced and investigated. Using an ensemble of Fe3O4 carriers as a superparamagnetic probe, Langeven’s paramagnetism theory, we appreciated size parameters of their shell, which was confirmed by independent measurements of specific surface area of the nanostructures and thermodynamic sedimentation stability of the corresponding magnetic fluids. The results obtained may be used in development of new forms of magnetocarried medical remedies for targeted delivery, and adsorbents based on NC of superparamagnetic core-shell type with multilevel nanoarchitecture, and for determination, control and optimization of size parameters of its components.

Non-stoichiometric zinc-doped spinel ferrite nanoparticles with enhanced magnetic property and their magnetorheology

To improve the magnetorheological (MR) performance compared to typical ferrites, non-stoichiometric zinc-doped spinel ferrite (Zn0.417Fe2.583O4) nanoparticles with a high saturation magnetization value and a truncated octahedron-like shape were synthesized using a simple thermal decomposition process with benefits of monodisperse and high crystallinity. The Zn0.417Fe2.583O4 had a high saturation magnetization value of 106 A m2/kg, which is generally higher than the other ferrites. The MR characteristics of the Zn0.417Fe2.583O4 particles dispersed in silicone oil were measured using a rotational rheometer under various magnetic field strengths. The flow curves and dynamic yield stress for the different magnetic field strengths exhibited the Herschel-Bulkley behavior with a slope of 2.0 and typical MR behavior. The sedimentation stability was further examined using Turbiscan.

Overproduction of microbial extracellular polymeric substances in subtropical intertidal sediments in response to endocrine disrupting chemicals

Microorganisms and their extracellular polymeric substances (EPS) in sediments are important in sediment stabilization and the fate of pollutants. However, how toxic organic pollutants affect bacteria and EPS in sediments, particularly in subtropical intertidal zones is poorly known. The present study aims to investigate the bacterial abundance and related EPS in simulated intertidal sandflat and mangrove sediments under the stress of endocrine disrupting chemicals (EDCs). Results showed that the temporal changes of the bacterial number in both sandflat and mangrove sediments were similar, increased from days 0 to 56 then became steady during the 84-days incubation. Bacteria exhibited an important role in the production of high molecular weight (HMW) EPS protein and the degradation of the low molecular weight (LMW) EPS protein. During incubation, the EPS polysaccharides changed from a colloidal-LMW fraction at the beginning to a more complex-HMW fraction at the end of the experiment. The increases in the concentration of HMW polysaccharides might contribute to sediment stabilization. Among different spiked EDCs, nonylphenol (NP) and 17α-ethinylestradiol (EE2) tended to accumulate in both sandflat and mangrove sediments and posed stresses to bacterial growth, especially the latter sediment. The persistent EDCs promoted a higher production of EPS polysaccharides and proteins in both sediments when compared to the respective control, but the EPS in the sandflat sediment was mainly in the colloidal fraction while the bound fraction was more abundant in the mangrove sediment. The present results enhance our understanding of the effects of EDCs on sediment biofilms in intertidal systems. This study also demonstrates the significance of EPS polysaccharides and proteins in sediment stabilization and provides a fundamental basis for future microbiology studies.

Utilization of pneumatic flow tube mixing technique (PFTM) for processing and stabilization of contaminated soft sediments in the NY/NJ Harbor

ABSTRACTA pilot study was conducted to evaluate the use of the pneumatic flow tube mixing method for stabilization and solidification of soft sediments dredged from the New York/New Jersey Harbor. The study included a comprehensive laboratory investigation aimed at determining the ideal mix for pneumatic flow tube mixing stabilization, and a pilot-scale demonstration of the pneumatic flow tube mixing technique in the field. Material stabilized during the demonstration was analyzed through unconfined compression tests, needle tests, laboratory vane shear tests, and flow tests in the laboratory and the cone penetration test in the field. Curing times for the samples were 3, 7, 14, and 28 days. The three cement content mixes were 4, 8, and 12% by weight (wet weight). Pneumatic flow tube mixing was demonstrated to be an efficient and rapid method for soft sediment stabilization with the resulting material showing uniform quality of mix meeting, New Jersey Department of Environmental Protection’s geotechnical and environmental fill placement criteria.

Benthic controls of resuspension in UK shelf seas: Implications for resuspension frequency

In situ measurements and ship-based resuspension experiments using annular flumes are used to determine sediment stability and critical erosion thresholds for four sites with significantly different sediment characteristics, located in the Celtic Sea at water depths of 100 m. Seasonal and spatial variability of sediment characteristics and erodability is examined, and found to be the result of changes in percentage of organic carbon in the surface sediments (R2 = 0.82) and bulk density (R2 = 0.73) respectively when individual characteristic bed parameters are considered. Principal component analysis and linear regression analysis are used to determine a predictive model for erosion threshold in the Celtic Sea (R2 = 0.99), based on grain size, sorting, kurtosis, bulk density, porosity, percentage fines, organic carbon content and chlorophyll a concentration. Physical sediment characteristics were found to be more significant controls of bed stability than biological factors. Local hydrodynamic conditions are used to determine the likelihood and frequency of resuspension given these critical erosion thresholds. Resuspension is driven by tidal currents, and is common year-round, leading to a constant re-working of bed sediments in particular at the muddier sites. This is confirmed by in situ measurements of suspended sediment concentration.

Gripping characteristics of an electromagnetically activated magnetorheological fluid-based gripper

The design and test of a magnetorheological fluid (MRF)-based universal gripper (MR gripper) are presented in this study. The MR gripper was developed to have a simple design, but with the ability to produce reliable gripping and handling of a wide range of simple objects. The MR gripper design consists of a bladder mounted atop an electromagnet, where the bladder is filled with an MRF, which was formulated to have long-term stable sedimentation stability, that was synthesized using a high viscosity linear polysiloxane (HVLP) carrier fluid with a carbonyl iron particle (CIP) volume fraction of 35%. Two bladders were fabricated: a magnetizable bladder using a magnetorheological elastomer (MRE), and a passive (non-magnetizable) silicone rubber bladder. The holding force and applied (initial compression) force of the MR gripper for a bladder fill volume of 75% were experimentally measured, for both magnetizable and passive bladders, using a servohydraulic material testing machine for a range of objects. The gripping performance of the MR gripper using an MRE bladder was compared to that of the MR gripper using a passive bladder.