Sedimentation Stability Research Articles

Construction of lignosulphonate-containing polymersomes and prospects for their use for elemental sulfur encapsulation

The renewable nature and natural origin of sulfite lignin (lignosulfonate) allow considering it as a potential raw material for the synthesis of valuable environmentally friendly polymer nanomaterials. To create them, a deep understanding of the relationship between the structure of the lignosulfonate macromolecule and the nature of intramolecular and intermolecular interactions is necessary, which would make it possible to control self-assembly processes and obtain nanostructures of specified sizes and morphology. The work discusses the structure formation processes occurring in the lignosulfonate – water – acetone system during the spontaneous formation of polymer nanostructures and submicrostructures. The electrostatic effects of sulfo groups and counterions under conditions of changing the medium polarity and their contribution to self-associations of lignosulfonates have been established. A state diagram was plotted for the ternary lignosulfonate – water – acetone system under conditions of induced phase separation at T = 298 K and under atmospheric pressure. The size and ζ-potential of these nanostructures and submicrostructures of lignosulfonates were estimated depending on the composition of the medium of their formation. The morphology of the resulting nanostructures and submicrostructures of lignosulfonates has been established. The vesicular nature of the aggregates (polymersomes) was confirmed, their shape being close to ideal spheroids with one hole, ranging in size from 40 to 500 nm. A multi-stage mechanism for the formation of lignosulfonate nanoassociates and submicroassociates is proposed. The encapsulating ability of our polymersomes with respect to elemental sulfur from the instant of its inception until the loss of aggregative and sedimentation stability was assessed. Lignosulfonate polymersomes can be recommended as additives to prevent the occluding effect of sulfur melts during hydrometallurgical processing of sulfide ores.

Accounting for uncertainty in marine ecosystem service predictions for spatial prioritisation

AbstractAimSpatial assessments of Ecosystem Services (ES) are increasingly used in environmental management, but rarely provide information on the prediction accuracy. Uncertainty estimates are essential to provide confidence in the quality and credibility of ES assessments for informed decision making. In marine environments, the need for uncertainty assessments for ES is unparalleled as they are data scarce, poorly (spatially) defined, with complex interconnectivity of seascapes. This study illustrates the uncertainty associated with a principle‐based method for ES modelling by accounting for model variability, data coverage and uncertainty in thresholds and parameters.LocationTauranga, New Zealand.MethodsA sensitivity analysis was applied on ES models for marine bivalves (Austrovenus stutchburyi and Paphies australis) and their contribution to Food provision, Water quality regulation, Nitrogen removal and Sediment stabilisation. ES estimates from the sensitivity analysis were compared against baseline ES predictions. Spatial uncertainty patterns were analysed for individual ES through bi‐plots and multiple ES through spatial prioritisation using Zonation.ResultsOur study showed spatially explicit differences in uncertainty patterns for ES and between species. Food provision had highest maximum uncertainty (>5 points) but also the largest area of high ES and high certainty conditions. Zonation analysis conducted on baseline and conservative ES values showed overall robust outcomes of top 30% area, but important nuances through shifts in top 5% and 10% areas that allowed for a consistently better representation of ES when accounting for uncertainty.Main ConclusionsThe spatial prioritisation in combination with the ES uncertainty biplots provide tools for spatial planning of individual and multiple ES to focus on area of highest value with highest certainty and can thereby help reduce risk and aid decision‐making at acceptable confidence levels. This type of information is urgently needed in marine ES assessments and their management, but likewise extends to other environments to improve transparency.

Determinants of mangrove seedling survival incorporated within hybrid living shorelines

Many communities around the world face a pressing need to increase coastal resilience due to widespread coastal erosion and rising sea levels. Natural habitats such as mangrove forests have been increasingly recognised for their ability to protect coastlines through wave attenuation and sediment deposition and stabilisation. However, attempts to rehabilitate mangroves for coastal protection have been met with difficulties due to smaller windows of opportunity for seedling survival at sites experiencing high wave energy and erosion. In this study, we planted the mangrove Avicennia alba in planting pods (n = 348) deployed on an eroding shoreline in Singapore and compared survival to those planted in control plots. Several ecological factors that might influence A. alba survival were manipulated, such as life stage during planting, reduction of wrack accumulation, elevation, and post-planting maintenance. We found that mangrove pods significantly increased mangrove seedling survival. Planting older A. alba seedlings, reducing wrack accumulation, and deploying the pods at a higher elevation further increased survival. Additionally, pressure gauges deployed showed that the pods were able to attenuate wave energy, thus providing hydrodynamic shelter to mangroves. Hybrid living shorelines have the potential to facilitate mangrove rehabilitation through the alleviation of adverse environmental conditions, but other ecological requirements for mangrove seedling survival will need to be met to optimise rehabilitation efforts.

Particle aggregation induced by microorganisms is a key mechanism for the biostabilization of coastal sediment

Biofilm surrounding sediment particles can significantly enhance the stability of coastal sediment. This phenomenon is known as biostabilization. Biofilm mainly consists of extracellular polymeric substances (EPS) and microorganisms. While the role of EPS in biostabilization is well-established, microbial contribution requires further exploration. Herein, an experiment was conducted to compare the stability and morphological characteristics of sediment under the effects of biofilm (with microorganisms) and pure EPS extracted from the biofilm (without microorganisms). The microorganisms used for biofilm culture are composed of diatoms and chlorella. The sediment used is a mixture of well-sorted muddy sand (D50 = 77 μm). Erosion tests showed that in the early stage of biofilm culture (within 17 days), biofilm and pure EPS had a similar ability to stabilize sediment, suggesting that in this stage, biofilm stabilized sediment relying on EPS. However, after 17 days of culture, biofilm showed a stronger ability to stabilize sediment than pure EPS, implying that in this stage, biofilm stabilized sediment by both EPS and microorganisms. These results indicate that microorganisms can also contribute to biostabilization, but during the early stage of culture, microorganisms in biofilm cannot make such contributions. Optical observations found that when the sediment-stabilizing ability of biofilm and pure EPS was comparable, the morphological characteristics of sediment particles under the effects of them were similar, both appearing as scattered single particles. However, when biofilm exhibited a stronger sediment-stabilizing ability, sediment particles with biofilm connected into large-size aggregates, whereas sediment particles with pure EPS remained single and scattered. These results suggest that in the later stage of biofilm culture, microorganisms play a role in the aggregation of sediment particles and hence contribute to biostabilization. Based on these findings, a conceptual framework has been proposed for predicting sediment stability under the effects of biofilm.

Mangroves as Coastal Protection for Restoring Low-Energy Waterfront Property

Mangroves offer vital ecological advantages including air and water filtration, coastal and estuarine habitat provision, sediment stabilization, and wave energy dissipation. Their intricate root systems play a key role in safeguarding shorelines from tsunamis and erosive storms by dissipating wave energy. Moreover, mangroves shield against boat wakes and wind-waves, thus naturally bolstering shoreline defense. Wave dissipation is a function of forest width, tree diameter, and forest density. Restoration efforts of juvenile mangroves in Florida’s Indian River Lagoon (IRL) aim to reduce wave energy in areas vulnerable to erosion. Physical model testing of wave dissipation through mangroves is limited due to the complexity in representing the mangrove structure, where prop roots are non-uniform in both diameter and location. Previous studies have quantified wave-dissipating effects through the use of scaled and parameterized mangrove structures. This study measures the dissipation effects of live mangroves in a wave flume, forced by conditions representative of the IRL. These measurements are used to validate a parameterized dowel model. Error between wave attenuation factors for the live mangrove and dowel system was on average 2.5%. Validation of the modularized dowel system allowed for further parameterized testing to understand forest structure effects, such as sediment stabilization and wave attenuation. Maximum wave attenuation achieved in this study was 27–35% corresponding to a 40–60% reduction in wave energy depending on the configuration of the system. The wave reduction resulted in a 50–70% decrease in sediment erosion from the berm. The dowel tests indicate a target minimum thickness for mangrove root systems of 0.6 m for shoreline stabilization and restoration in the IRL.

Mulberry-like NiFe2O4 nanospheres for smart magnetic fluid: Facile synthesis, magneto-responsive performances and sedimentation stability study

Magnetorheological (MR) fluids have been extensively studied and utilized in various fields but are still restricted for their broad applications owing to the relatively poor sedimentation stability. Herein, mulberry-like NiFe2O4 nanospheres were fabricated via a facile solvothermal route to fight against the sedimentation challenge. Different analytical approaches were employed to thoroughly characterize the fabricated mulberry-like NiFe2O4 nanospheres. The resultant NiFe2O4 nanospheres were suspended in silicone oil to produce the model MR suspension and its magneto-responsive properties and sedimentation stability were investigated in detail. It was revealed that the NiFe2O4 nanospheres-based suspension demonstrated sufficient MR responses, which can be interpreted as evidence that the increased rheological and viscoelastic properties were observed as the magnetic field intensity increased. Furthermore, the designed novel MR suspension demonstrated a superior sedimentation stability in comparison with the carbonyl iron particles-based MR system, which was positive in the practical application of MR fluids to microfluidic devices.

The Investigation of Broad-Spectrum Sealing Drilling Fluid Based on Horsfield Close-Packing Theory

Summary In shale gas drilling operations, oil-based drilling fluids have proved to be effective in addressing the issue of shale reservoir hydration expansion, serving as the primary working fluid for complex subsurface shale formations. However, the presence of shale laminations and the development of microfractures with varying widths require drilling fluids with excellent sealing capabilities. In this study, a comprehensive investigation was conducted to develop a drilling fluid system with broad-spectrum high-sealing performance. The porosity of bridging particles was determined by using the Archimedean drainage method. The bridging particle size and quantity at each level were meticulously designed through leveraging the Horsfield close-packing theory. The incorporation of deformable nanoscale polymer sealing materials further enhanced the sealing performance of the drilling fluid system. Additionally, hydrophobic nanoscale silica particles were introduced as coemulsifier to prepare Pickering emulsions, thereby improving emulsion stability and enhancing particle-size distribution for improved sealing. Through formulation optimization, a drilling fluid system with broad-spectrum, high-sealing performance capabilities was developed. The study revealed a reduction in porosity of closely packed bridging particles from 35.36% to 11.38%. The drilling fluid system exhibited a remarkable sealing efficiency of 99.2% for microfractures in the 1–10 μm range and 95.8% for microfractures in the 30–50 μm range. Furthermore, it demonstrated excellent sedimentation stability, with a sedimentation factor of less than 0.52 after 48 hours of static sedimentation at 150°C. The drilling fluid system also exhibited favorable rheological, lubrication, and inhibition properties, thus meeting the demands of field applications.

Synthesis and mechanism analysis of a non-toxic amine-based clay mineral surface hydration intercalation inhibitor

The surface hydration of clay minerals remains a serious challenge for drilling projects. Herein, we synthesized a non-toxic amine-based clay mineral surface hydration intercalation inhibitor (ODBB) whose structure was characterized using fourier transform infrared spectroscopy, mass spectrometry, and proton nuclear magnetic resonance spectroscopy. The inhibitory ability of ODBB was evaluated through isothermal adsorption, X-ray diffraction, thermogravimetric analysis, linear expansion, rolling recovery, and sedimentation stability. The biological toxicity of ODBB was tested with a bioluminescent bacteriological method. The inhibition mechanism was analysed using elemental analysis, atomic absorption spectroscopy, wettability measurement, zeta potential analysis, capacity of exchangeable cation, scanning electron microscopy, and molecular dynamics simulation. The addition of more than 0.5 wt% ODBB resulted in a reduction in the base spacing of Na-MMT/ODBB from 2.10 to 1.31 nm, while the derivative thermogravimetric curve showed a single peak at 50–200 °C. These results showed that the surface hydration of Na-MMT was completely inhibited. Meanwhile, an EC50 value of 93,000 indicated that ODBB was non-toxic. ODBB intercalated into the crystal layer space of Na-MMT, replaced interlayer cations (Na+), adsorbed on the surface (d001) of Na-MMT by electrostatic interactions, and formed hydrogen bonds with the oxygen atoms on the surface (d001). Furthermore, ODBB tightened the crystalline layer and reduced the base spacing through hydrogen bonding and electrostatic forces.

Design and experiment study of a novel dual-channel independent-coil magnetorheological grease damper

In order to address the issue of reduced damping force dynamic range in magnetorheological (MR) damper caused by the high zero-field viscosity of MR grease, known for its sedimentation stability, this paper introduces a novel dual-channel independent-coil MR damper (DCICMRD). Firstly, the dual-channel configuration and the magnetic circuit structure of independent coils were meticulously designed, and a genetic algorithm was employed to conduct multi-objective optimization of the structural parameters for DCICMRD. The optimization results indicate that all performance metrics of the damper post-optimization exhibit improvements exceeding 15%. Then, the theocratical model of the damping force for DCICMRD under three operational modes are established, and the output damping force of various input currents for different operating mode is obtained. Finally, the DCICMRD was manufactured and subjected to dynamic performance testing. The results revealed that the damping force dynamic range in Mode III, i.e. dual-channel structure, can achieve approximately 15 times, whereas Mode I, i.e. traditional single-channel structure, only attains approximately 9 times. The aforementioned research holds significant implications for expanding the further engineering applications of MR dampers.

Assessing the reclamation of a contaminated site affected by the Fundão dam tailings trough phytoremediation and bioremediation

The rupture of the Fundão dam (Brazil) spread tailings contaminated with sodium and ether-amine into the Doce River Basin. Aiming at rehabilitating a contaminated riparian site, phytoremediation with native species of the Atlantic Forest was performed under four treatments: ES-1: physical remediation (sediment scraping) + chemical remediation (organic matter) + bioremediation (double inoculation with the arbuscular mycorrhizal fungus (AMF) Rhizophagus irregularis and the plant growth-promoting bacteria Bacillus subtilis); ES-2: chemical remediation + bioremediation; ES-3: physical remediation + chemical remediation; ES-4: chemical remediation. Ether-amine and sodium contents, plant growth and, soil quality parameters were compared among treatments and relative to preserved and degraded sites. Two years after planting, the outstanding plant growth was attributed to the phytoremediation of ether-amine and ammonium, followed by a significant increase in soil microbial biomass (Phospholipid fatty acids-PLFAs), particularly the Gram+ bacteria and total fungi but not AMF, whose response was independent of the inoculation. While sodium and ether-amine declined, soil K, P, NO3− contents, dehydrogenase and acid phosphatase activities, cation exchange capacity (CEC) and soil aggregation increased, especially in ES-1. Thus, such remediation procedures are recommended for the restoration of riparian areas affected by the Fundão tailings, ultimately improving sediment fertility, aggregation and stabilization.

Influence of structural properties on the suspension performance of ultra-high temperature stabilizers

One of the key challenges preventing the exploration and development of ultra-deep oil and gas deposits is the settlement instability of cement slurry at extremely high temperatures. In the previous work, an ultra-high temperature suspension stabilizer was created to enhance the cement slurry's high temperature settlement stability. This work investigates its mechanism from the standpoint of structural characteristics based on the prior research. Thermal stability tests and calculations of the pyrolysis activation energy were used to examine the structural features of the suspension stabilizer. The viscosity-temperature relationship, the microstructure of the suspension stabilizer solution, the molecular structure change of the suspension stabilizer in the solution environment, and the interaction energy with water molecules were all studied in conjunction with contemporary material testing techniques and molecular dynamics simulation calculations. The findings indicate that: 1) The bulk structure of the suspension stabilizer has a pyrolysis temperature of 330 °C, which indicates a degree of heat resistance; 2) In a solution environment, the viscosity of the solution is a critical factor in determining the stability of the cement slurry's sedimentation, which is dependent on the integrity of the amide group in the suspension stabilizer. The cyclic functional group's ortho action prevents the amide monomer from hydrolyzing in the ultra-high temperature suspension stabilizer. The cement slurry has good sedimentation stability because the hydrogen link between the retained amide group and the water molecule has not entirely broken down, and the solution still has some viscosity.

Bioturbating megafauna limits the expansion of Cymodocea nodosa seagrass meadows

In seagrass systems, there is a realization that biotic interactions affecting sediment stability might be as important as abiotic stressors in shaping the growth and distribution patterns of seagrass vegetation. However, few studies have looked at the interaction between seagrass and large (mega) bioturbating species, although through sediment reworking activity they may have the capacity to cause large scale impact on seagrass establishment. We assessed the effect of bioturbation by mobile megabioturbators (species lager than 5 cm) on subtidal seagrass (Cymodocea nodosa) using a manipulative field experiment where access by megabioturbators was restricted for 4 months during the growth season. There was a negative effect of megabioturbators on both the biomass and density of young seagrass ramets extending outwards from a mature seagrass meadow, but megabioturbators did not have a notable effect on seagrass growth in the meadows. Interestingly, the exclusion of megabioturbators in all tested habitats significantly modified the infaunal community composition, indicating the presence of complexity in biotic interactions and the possibility of indirect effects caused by the megabioturbators. Overall, megabioturbators have direct and indirect impact in seagrass habitats, playing a significant role in seagrass distribution patterns.

Liquid crystallinity and magnetorheological performance of polymeric liquid crystal magnetic composites

ABSTRACT Magnetorheological fluids (MRF) are regarded as a novel ‘intelligent’ material because they show the ability to respond to external stimuli. However, with the extension of working time, the agglomeration and sedimentation of magnetic particles become a serious problem, which has a great impact on the magnetorheological performance. Many methods have been proposed to overcome the particle settling problem, including magnetic particle modification and carrier liquid modification, but they all show negative effects on the magnetorheological performance of MRF. A new method to prepare the magnetic liquid crystal (LC) composites [PEA-COOH]SO3H@Fe3O4 series, with Fe3O4 nanoparticles as core and side-chain supramolecular LC polymers with different mesogen contents as coating, were reported. The chemical structure, magnetic property and LC properties were investigated by a variety of techniques. In order to study the effects of the mesogen content and LC phase state of magnetic LC composites on magnetorheological performance and sedimentation stability, MRF based on silicone oil carrier liquid and [PEA-COOH]SO3H@Fe3O4 dispersed phase were prepared. It was found that dynamic yield stress, plastic viscosity and the sedimentation ratio increased slightly with increasing mesogen content in the magnetic LC composites. What’s more, MRF prepared by magnetic LC composites annealed in LC state exhibited better magnetorheological performance and sedimentation stability than those in glassy state and isotropic state. These results indicated that the synergetic effects of LC orientation and magnetic field-induced arrangement of Fe3O4 magnetic particles can improve the magnetorheological performance and sedimentation stability of MRF.

Sedimentation evaluation of high-viscosity linear polysiloxane-based magnetorheological fluids using automated vertical axis inductance monitoring system

The sedimentation evaluation of magnetorheological fluids (MRFs) is a key component to developing successful commercial MRF-based engineering applications. In this study, the long-term sedimentation stability of highly stable high-viscosity linear polysiloxane-based MRFs (HVLP MRFs) was experimentally investigated by using an automated vertical axis inductance monitoring system (AVAIMS). The sedimentation evaluation of the HVLP MRFs with high particle loadings up to 45 vol% was tracked for 295 days, and the four different sedimentation zones such as supernatant, original concentration, variable concentration, and sediment were identified. To this end, the automated identification method to determine the sedimentation zone boundaries of highly stable MRFs was proposed. Three HVLP MRF samples with two different high particle loadings of 35 vol% and 45 vol% and two different high carrier viscosities of 5k and 10k cSt were selected as testing samples and one commercial MRF with a particle loading of 40 vol% (i.e., LORD MRF-140CG) also was tested as a baseline.

Effect of the transition section on the flow structure of consecutive river bends with point bars

The transition section (TS), linking the front bend and the back bend in consecutive river bends, plays a key role in the flow hydraulic characteristics, sediment transport, and riverbed evolution in meandering rivers, which is crucial for flood control, navigation, and river stability. Most existing studies on the hydraulic effect of the TS focus on flat-bed scenarios, rendering an inadequate understanding of the TS in consecutive bends with point bars, often found in natural rivers. Based on three-dimensional numerical simulations, the effects of the length and the topography of the TS are investigated in detail on the flow structure in consecutive bends with point bars, respectively. The results reveal that without an adequate TS length, the residual circulation of the front bend (RC) inhibits the development of the main circulation in the back bend (MC), causing the positions of the maximum strength of the MC and the maximum value of cross-section-averaged turbulent kinetic energy (<tke˜>) in the back bend moving upstream. As the length of the TS increases, the above effect of the front bend gradually decreases. The critical length of the TS to fully decay the RC is 4.8 times the bend width (B) in consecutive bends with point bars, longer than that (4B) in the flat-bed bend. Furthermore, the central bar in the TS is found to facilitate the generation of the outer bank cell and accelerate the decay of the RC. These effects of the TS can profoundly change the flow hydraulics, sedimentation, and stream stability of consecutive bends. The results of the study will help to further understand the linkage role of the TS in consecutive bends and may serve as a rational reference for managing natural meandering rivers with multiple hydrological, geomorphological, and/or ecological goals.

Nanosuspension of Purwoceng Extract (Pimpinella Pruatjan Molk) Using Alginate and Sodium Chloride

Pimpinella pruatjan Molk (Purwoceng) is known to increase the degree of spermatogenesis in the testes, the number and motility of spermatozoa. This study aimed to prepare purwoceng nanosuspension using ionic gelation method to increase the effectiveness of purwoceng roots extract. Pimpinella pruatjan Molk (Purwoceng) nanosuspension was made using sodium alginate and calcium chloride as a crosslinker. The optimum nanosuspension were chosen from the most stable formula which is contained 0.001% sodium alginate, 18 mM calcium chloride, and 0.666% purwoceng roots extract, or by comparing polymer and crosslinker of 1,6: 0,4 mL (formula F129). The organoleptic observation displayed that the nanosuspension is a clear yellow colloid, slightly viscous, and smell like purwoceng roots extract. Nanosuspension has pH 4, stable on the sedimentation stability test and showed no agglomeration. Nanosuspension’s drops of formula F129 were observed by PSA (particle size analyzer) result at average size 150,8 nm (SD=100,5). Nanosuspension morphology was spheres which the average size 150 nm until 630 nm and zeta potential value was -2.29 mV. Therefore, it can be concluded that formula F129 can form an optimum nanosuspension of purwoceng roots extract.

Improving the colloidal stability of pectin-phycocyanin complexes by increasing the mixing ratio.

In the food industry, the phycobiliprotein phycocyanin acts as a color pigment or the functional part of the superfood "Spirulina." It is industrially extracted from Arthrospira platensis. Current scientific research is focusing on finding complex partners with the potential to stabilize phycocyanin against its sensitivity toward heating and pH changes. Less attention is paid to the factors that influence complexation. This study focuses on the mixing ratio of phycocyanin with pectin. Phycocyanin concentration was fixed, and the mixing ratios ranged from 0.67 to 2.50 (pectin:phycocyanin). All samples were analyzed for their color, size, microscopic structure, zeta potential, and sedimentation stability before and after heating at 85°C. It was found that increasing the pectin content fostered the initial interactions with the protein and chromophore, resulting in a color shift from blue to turquoise. The size of the complexes decreased from several micrometers to nanometers with increasing pectin concentration. Those smaller complexes that were formed at a mixing ratio of 2.5 showed a higher colloidal stability over a period of ∼2days. It is suggested that at a low mixing ratio (0.67), phycocyanin cannot be completely entrapped within the complexes and attaches to the complex surface as well. This results in aggregation and precipitation of the complexes upon heating. With increasing aggregation and consequently size as well as density of the complexes, sedimentation was accelerated. PRACTICAL APPLICATION: Under acidic conditions, as found in many foods and beverages (e.g.,soft drinks, hard candy), phycocyanin tends to agglomerate and lose its color. Specifically heating, triggers denaturation, causing phycocyanin to aggregate and lose vitalprotein-chromophore interactions necessary to maintain a blue color. To prevent precipitation of the phycocyanin-pectin complexes, increasing the amount of pectin to a ratio of at least 2.0 is effective. This illustrates how adjusting the mixing ratio improves stability. Conversely, lower mixing ratios induce color precipitation, valuable in purification processes. Thus, practical use of biopolymer-complexes, requires determination of the optimal mixing ratio for the desired effect.

The Ellrott grab: A small, lightweight sediment sampler for collecting undisturbed sandy sediments

AbstractSampling sandy surface sediments is an important first step in understanding biogeochemical processes in these dynamic environments. However, sampling such sediments poses several challenges, especially when undisturbed samples with porewater are required. Several grab samplers are commercially available, but they are either prone to sample loss, too heavy or bulky for use in small vessels, or those with spring‐loaded mechanisms present safety issues. Here, we present the Ellrott grab, a lightweight sediment sampler designed for collecting undisturbed surface sediments including porewater and overlying bottom seawater. The sampler consists of a frame and a rotating bowl that can collect 370 cm2 of surface sediments up to 10 cm deep (2.5 liters total volume). The instrument is 40 × 60 cm in size, has a basic weight of 10 kg, with up to 20 kg additional weights for stability in sandy sediments. Two persons can operate the grab and it can be used on small boats with a crane and winch system or a hand winch. The grab is now in routine use in the Wadden Sea and in Isfjorden, Svalbard. The samples obtained from the grab were suitable for various geochemical and microbial analyses. Using microelectrodes, we found that in situ oxygen profiles were similar to ex situ profiles in cores subsampled from the grab, confirming that the grab causes minimal disturbance to the sample. Although the grab was designed for collecting sandy sediments, it could also be applied to silty sediments, allowing straightforward and efficient sampling of various sediment types.

Long-term effectiveness of lead precipitation as carbonate and its stability under acidic conditions by using activated serpentine mineral

Utilization of readily accessible serpentine mineral, for lead removal from wastewater is a sustainable strategy, but the adsorption capacity of the raw serpentine is limited due to its small interlayer spacing and low surface reactivity, not to say the cases under acidic conditions. In this study, natural serpentine was simply ball-milled to obtain enhanced reactivity and dissolution due to the generation of various lattice defects, which allowed the highly efficient lead fixation even under acidic conditions (at initial pH of 3), compared to that driven by the surface adsorption. Characterizations demonstrated the continuous dissolution of serpentine in solution with the reaction time prolonged, inducing the heterogeneous precipitation of significant (basic) lead carbonate on serpentine surface with an aid of even very dilute atmospheric CO2, which worked as the dominated mechanism for enhancing the whole lead fixation efficiency. Results showed that more than 99.5 % of soluble lead could be immobilized within 1 ∼ 2 h with serpentine dosage of 0.5 g/L under low concentration (5 ∼ 100 mg/L), with a high lead fixation capacity about 1782.9 mg/g after 48 h under high concentration (1000 mg/L). Moreover, the stability of the Pb-bearing sediment under acidic exposure (pH 3) for 24 h was confirmed, and the dissolved lead from chloride and sulfate salts could also be immobilized using the as-proposed strategy. Altogether, these findings demonstrated the high efficiency and long-term effectiveness of lead fixation on the ball-milled serpentine, which makes it a promising candidate for application to green remediation of heavy metal contaminations in various sites along with the utilization of waste mineral resources.

Petroleum products in wastewater and their properties

Water bodies are polluted by oil and petroleum products from various sources. The primary sources are navigation, accidents on ships and coastal areas, industrial wastewater discharges, surface wastewater from settlements, and transportation crossings of water bodies. Reducing the content of oil products in water bodies is an important task of nature protection, requiring the development of new effective methods of wastewater treatment from oil products. A systematic approach is proposed to solve this problem, including analysis of conditions of wastewater formation, study of phase-disperse composition of pollutants and their physical and chemical properties, and analysis of possible water treatment methods. According to the formation conditions, oily wastewater can be divided into domestic wastewater, surface runoff, and industrial wastewater. Depending on the formation conditions, oil products in wastewater are in different phase-disperse states with different sedimentation and aggregative stability values. Separation methods are most effective for sediment-unstable petroleum product systems and are sufficiently simple and reliable. Sedimentation stable systems of petroleum products in water need to be preliminarily destabilized. This is achieved by adding alkaline acids, mineral coagulants, or organic polyelectrolytes. Wastewater characterized by aggregative stable systems of petroleum products can be treated by degradation methods such as ozonation or sorption.