Ti-containing NPs in raw water and their removal with conventional treatments in four water treatment plants in Taiwan

The ingestion of Ti-containing nanoparticles from drinking water has emerged as a concern in recent years. This study therefore aimed to characterize Ti-containing nanoparticles in water samples collected from four water treatment plants in Taiwan and to explore the challenges associated with measuring them at low levels using single particle-inductively coupled plasma mass spectrometry. Additionally, the study sought to identify the most effective processes for the removal of Ti-containing nanoparticles. For each water treatment plant, two water samples were collected from raw water, sedimentation effluent, filtration effluent, and finished water, respectively. Results revealed that Ti-containing nanoparticles in raw water, with levels at 8.69 μg/L and 296.8 × 103 particles/L, were removed by approximately 35% and 98%, respectively, in terms of mass concentration and particle number concentration, primarily through flocculation and sedimentation processes. The largest most frequent nanoparticle size in raw water (112.0 ± 2.8 nm) was effectively reduced to 62.0 ± 0.7 nm in finished water, while nanoparticles in the size range of 50-70 nm showed limited changes. Anthracite was identified as a necessary component in the filter beds to further improve removal efficiency at the filtration unit. Moreover, the most frequent sizes of Ti-containing nanoparticles were found to be influenced by salinity. Insights into the challenges associated with measuring low-level Ti-containing nanoparticles in aqueous samples provide valuable information for future research and management of water treatment processes, thereby safeguarding human health.

Sample-to-answer lateral flow assay with integrated plasma separation and NT-proBNP detection

Through enabling whole blood detection in point-of-care testing (POCT), sedimentation-based plasma separation promises to enhance the functionality and extend the application range of lateral flow assays (LFAs). To streamline the entire process from the introduction of the blood sample to the generation of quantitative immune-fluorescence results, we combined a simple plasma separation technique, an immunoreaction, and a micropump-driven external suction control system in a polymer channel-based LFA. Our primary objective was to eliminate the reliance on sample-absorbing separation membranes, the use of active separation forces commonly found in POCT, and ultimately allowing finger prick testing. Combining the principle of agglutination of red blood cells with an on-device sedimentation-based separation, our device allows for the efficient and fast separation of plasma from a 25-µL blood volume within a mere 10 min and overcomes limitations such as clogging, analyte adsorption, and blood pre-dilution. To simplify this process, we stored the agglutination agent in a dried state on the test and incorporated a filter trench to initiate sedimentation-based separation. The separated plasma was then moved to the integrated mixing area, initiating the immunoreaction by rehydration of probe-specific fluorophore-conjugated antibodies. The biotinylated immune complex was subsequently trapped in the streptavidin-rich detection zone and quantitatively analyzed using a fluorescence microscope. Normalized to the centrifugation-based separation, our device demonstrated high separation efficiency of 96% and a yield of 7.23 µL (= 72%). Furthermore, we elaborate on its user-friendly nature and demonstrate its proof-of-concept through an all-dried ready-to-go NT-proBNP lateral flow immunoassay with clinical blood samples.

Perspectives on cultivation and harvesting technologies of microalgae, towards environmental sustainability and life cycle analysis

The development of algae is seen as a potential and ecologically sound approach to address the increasing demands in multiple sectors. However, successful implementation of processes is highly dependent on effective growing and harvesting methods. The present study provides a complete examination of contemporary techniques employed in the production and harvesting of algae, with a particular emphasis on their sustainability. The review begins by examining several culture strategies, encompassing open ponds, closed photobioreactors, and raceway ponds. The analysis of each method is conducted in a systematic manner, with a particular focus on highlighting their advantages, limitations, and potential for expansion. This approach ensures that the conversation is in line with the objectives of sustainability. Moreover, this study explores essential elements of algae harvesting, including the processes of cell separation, dewatering, and biomass extraction. Traditional methods such as centrifugation, filtration, and sedimentation are examined in conjunction with novel, environmentally concerned strategies including flocculation, electro-coagulation, and membrane filtration. It evaluates the impacts on the environment that are caused by the cultivation process, including the usage of water and land, the use of energy, the production of carbon dioxide, and the runoff of nutrients. Furthermore, this study presents a thorough examination of the current body of research pertaining to Life Cycle Analysis (LCA) studies, presenting a perspective that emphasizes sustainability in the context of algae harvesting systems. In conclusion, the analysis ends up with an examination ahead at potential areas for future study in the cultivation and harvesting of algae. This review is an essential guide for scientists, policymakers, and industry experts associated with the advancement and implementation of algae-based technologies.

Laboratory data on dynamics of microplastic particles sinking in seawater with dispersed xanthan gum and kappa-carrageenan and rheological properties of these dispersions

This paper presents a dataset comprising measurements of the sinking dynamics of microplastics settling in artificial seawater (AS) and in dispersions of polymers in seawater: xanthan gum, kappa-carrageenan, and their mixtures in two concentrations: 0.5 g/L and 1 g/L. Plastic particles are classified into fifteen groups representing various shapes: disks, rods, blades, spheres, and materials: PS, POM, PET, PA6. The sinking of individual particles in a settling tank was visualized using the shadowgraph method and images were recorded using a camera with macro lenses. Next, Particle Tracking Velocimetry was applied to retrieve the time-resolved position of MPs and their orientation and to calculate instantaneous sinking velocity. Non-Newtonian properties of solutions were measured using a rheometer. Shear-dependent viscosity, shear stress amplitude sweeps, the first normal stress difference, and gelling time were assessed. Datasets may find application in a range of scientific and engineering areas including fluid mechanics, chemical engineering, food engineering, petroleum industry, wastewater treatment, rheology, and environmental hydrodynamics, e.g. in research on particle dynamics in complex fluids, modeling of microplastics fate in aqueous systems, and to develop numerical models on the hydrodynamics of solid particles in complex liquids.

Selective recovery of gold and silver from electronic wastes through a sequential process of Qalkari and room-temperature hydrometallurgy

This work was focused on the selective recovery of gold and silver from electronic wastes using a sequential process of pyrometallurgy (Qalkari) and room-temperature hydrometallurgy. In the first step, electronic wastes underwent Qalkari recycling, yielding tablets containing precious elements (Qalkari furnace product) and melting slag (Qalkari furnace waste). In the subsequent hydrometallurgy phase, the nitric acid concentration and the input solid amount were optimized for the effective room-temperature recovery of gold. Due to the successful separation of precision elements and disturbing substances in Qalkari, the gold recovery efficiency of 99.99% was obtained at the acid concentration of 50% (v/v) and the solid input of 15% (w/v). Afterwards, HCl, NH4Cl, and NaCl were used for silver recovery from the Qalkari-processed gold-recovered leaching solution, leading to the efficiency of 99.99%. But NH4Cl was recognized as the most effective precipitant as it promises the most enhanced potential for the possible subsequent recovery of palladium. In conclusion, this study draws the effectiveness of Qalkari in recycling electronic wastes, with a significant impact on the efficiency of succeeding room-temperature hydrometallurgical processes for gold and silver recovery within a reasonable leaching time.

Impact of the crystal size of crystalline active pharmaceutical compounds on loading into microneedles

Microneedle (MN) technology offers a promising platform for the delivery of a wide variety of active pharmaceutical compounds into and/or through the skin. Yet, the low loading capacity of MNs limits their clinical translation. The solid state of loaded compounds, crystallinity versus amorphousness and crystal size of the former, could greatly affect their loading. Here, we investigated the effect of the crystal size of crystalline compounds on their loading into dissolving MNs, prepared using the solvent-casting technique. A model crystalline compound was subjected to crystal size reduction via wet bead milling and loaded into dissolving MNs. A range of crystal sizes, from micro to nano, was obtained via different milling periods. The obtained crystals were characterized for their size, morphology, and sedimentation behavior. Besides, their content, solid state inside the MNs, and impact on the MN mechanical strength were assessed. The crystals exhibited size-dependent sedimentation, which dramatically affected their loading inside the MNs. However, crystal size and sedimentation demonstrated a negligible effect on the mechanical strength and sharpness of the needles, hence no anticipated impact on the MNs' drug delivery efficiency. The elucidation of the correlation between the crystal size and MN loading opens new potentials to address a major drawback in MN technology.

Overlooked encounter process that affects physical behaviors of stabilized nanoscale zero-valent iron during in situ groundwater remediation

Dynamic encountering between groundwater matrices and nanoscale zero-valent iron (NZVI) injected for in situ subsurface remediation affects NZVI's mobility and has not been well recognized. Polyacrylic acid (PAA)-stabilized NZVI (NZVI-PAA) and Mg(OH)2-coated NZVI (NZVI@Mg(OH)2) were investigated as representative NZVIs stabilized by enhanced electrostatic repulsion and reduced magnetic attraction, respectively. Encounters with divalent cations and humic acid (HA) induced the drastic aggregation and sedimentation (presedimentation) of NZVI-PAA owing to Lewis acid-base interactions and heteroaggregation. In addition, encountered groundwater electrolytes could not effectively provide electrostatic repulsion for NZVI-PAA, resulting in breakthrough ripening dynamics. The presedimentation and ripening behaviors of NZVI-PAA were eliminated and unheeded after mixing the NZVI slurry with groundwater by sonication. In comparison, the encountering process barely impacted NZVI@Mg(OH)2, for which settling was hindered. Although the particle-collector attraction promoted NZVI@Mg(OH)2 adsorption on pristine and hybrid-coated sands, the Langmuirian blocking dynamics of the NZVI@Mg(OH)2 breakthrough demonstrated its high mobility after adsorption sites of sand surface were exhausted. Extended Derjaguin-Landau-Verwey-Overbeek analysis and transport modeling provided insights into overlooked effects of encountering on physical behaviors of different stabilized NZVIs, which should be considered during practical applications under diverse subsurface conditions.

Sedimentation and Laser Light Scattering Methods for Quantifying Synthetic Tau Aggregation Propensity

Tau aggregation assays detect and quantify the conversion of soluble tau monomers into species having filamentous or oligomeric structure. Assays for filamentous aggregates in cross-β-sheet conformation leverage optical, biochemical, or biophysical methods, each with their own advantages and throughput capacity. Here we provide protocols for two medium-throughput assays based on sedimentation and laser light scattering and compare their performance, their utility for characterizing tau aggregation dynamics, and their limitations relative to other approaches. Additionally, a protocol for transmission electron microscopy analysis is updated so as to be compatible with the truncated tau variants that have emerged as powerful tools for interrogating the structural basis of tau polymorphism. Together these methods contribute to a rich tool kit for interrogating tau aggregation kinetics and propensity over a wide range of experimental conditions.

Canister valve and actuator deposition in metered dose inhalers formulated with low-GWP propellants

A challenge in pressurised metered-dose inhaler (pMDI) formulation design is management of adhesion of the drug to the canister wall, valve and actuator internal components and surfaces. Wall-material interactions differ between transparent vials used for visual inspection and metal canister pMDI systems. This is of particular concern for low greenhouse warming potential (GWP) formulations where propellant chemistry and solubility with many drugs are not well understood. In this study, we demonstrate a novel application of X-ray fluorescence spectroscopy using synchrotron radiation to assay the contents of surrogate solution and suspension pMDI formulations of potassium iodide and barium sulphate in propellants HFA134a, HFA152a and HFO1234ze(E) using aluminium canisters and standard components. Preliminary results indicate that through unit life drug distribution in the canister valve closure region and actuator can vary significantly with new propellants. For solution formulations HFO1234ze(E) propellant shows the greatest increase in local deposition inside the canister valve closure region as compared to HFA134a and HFA152a, with correspondingly reduced actuator deposition. This is likely driven by chemistry changes. For suspension formulations HFA152a shows the greatest differences, due to its low specific gravity. These changes must be taken into consideration in the development of products utilising low-GWP propellants.

Interaction of polystyrene nanoplastics with impurity-bearing ferrihydrite and implication on complex particle sedimentation

Nanoplastics (NPs) usually coexist with impurity-bearing ferrihydrite (ImFh), and their interaction is related to their environmental fate. In this study, the aggregation between ImFh (impurities: Al, Mn and Si) and polystyrene nanoplastics (PSNPs), as well as the sedimentation of ImFh-PSNP complex particles in the aqueous phase were investigated systematically with particle concentrations of 100 mg/L ImFh and 10 mg/L PSNPs. Our results revealed that the PSNP suspension was dispersive and stable under various pH values and low ion strength. After coexisting with ImFh, PSNPs aggregated with the positively charged ImFh to form ImFh-PSNP complex particles, which destroyed the stability of PSNPs. The increase in pH and Na+ concentration could inhibit their aggregation, but high Na+ concentration (>20 mM) caused the homoaggregation of PSNPs. The aggregation capacity of PSNPs with ImFh was in the order of Al-bearing Fh > Fh > Mn-bearing Fh > Si-bearing Fh. Zeta potential and Derjaguin-Landau-Verwey-Overbeek (DLVO) calculations indicated that Al-bearing Fh showed higher positive potential than pure Fh, which caused stronger electrostatic interactions with PSNPs. However, Mn and Si in ImFh decreased the positive potential and inhibited the electrostatic interaction with PSNPs, and the effect of Si was greater than that of Mn. The aggregation between ImFh and PSNPs inhibited the sedimentation of their complex particles, and the higher aggregation capacity appeared to have a greater inhibition degree. Due to the "electrostatic patches" effect of PSNPs, the energy barrier of the ImFh-PSNPs particles was higher than that of the ImFh particles. Our findings clarified the influence of impurities on the interaction between ImFh and PSNPs and provided insight regarding their fate in the environment.

Modeling mass removal and sediment deposition in stormwater ponds using floating treatment islands: a computational approach

Floating treatment islands (FTIs) offer effective solutions for stormwater management, providing flood attenuation and pollutant removal capabilities. However, there remains a knowledge gap concerning their performance, specifically in terms of pollutant removal and sediment deposition. To address this gap, the present study employs computational fluid dynamics (CFD) modeling to investigate the intricate interactions within FTI systems. Various FTI configurations are analyzed, considering mass removal through FTIs and sediment deposition, the first time where these two processes were considered together in a CFD environment. The findings demonstrate that FTIs have a significant influence on flow patterns and mass removal. Notably, FTIs enhance mass removal compared to the control case, with larger sediment particles exhibiting higher removal rates. The correlation between the short-circuit index and sedimentation in FTI ponds highlights the potential of FTIs as indicators of treatment efficiency. Furthermore, the study focuses on mass removal exclusively through the FTI root zones. The positioning of FTIs within the pond has a considerable impact, resulting in differences of up to 20% in mass removal. Moreover, the FTI configuration exerts a more pronounced influence on mass removal through FTIs than through sediment deposition alone. In cases where both processes occur simultaneously, the presence of FTIs lead to higher mass removal, primarily attributed to the FTIs themselves, particularly in the initial segment. Remarkably, certain FTI configurations enable mass removal exceeding 70% for large sediment particles, even with a pond length less than half of the original.

The role epiphytes play in particle capture of seagrass canopies

Seagrass epiphytic communities act as ecological indicators of the quality status of vegetated coastal environments. This study aims to determine the effect leaf epiphytes has on the sediment capture and distribution from outside sources. Thirteen laboratory experiments were conducted under a wave frequency of 0.5 Hz. Three epiphyte models were attached to a Zostera marina canopy of 100 plants/m2 density. The sediment deposited to the seabed, captured by the epiphytic leaf surface, and remaining in suspension within the canopy were quantified. This study demonstrated that the amount of epiphytes impacts on the sediment stocks. Zostera marina canopies with high epiphytic areas and long effective leaf heights may increase the sediment captured on the epiphyte surfaces. Also, reducing suspended sediment and increasing the deposition to the seabed, therefore enhancing the clarity of the water column. For largest epiphytic areas, a 34.5% increase of captured sediment mass is observed. The sediment trapped on the leaves can be 10 times greater for canopies with the highest epiphytic areas than those without epiphytes. Therefore, both the effective leaf length and the level of epiphytic colonization are found to determine the seagrass canopy ability at distributing sediment.

Bio-physical determinants of sediment accumulation on an offshore coral reef: A snapshot study

Sediments are found on all coral reefs around the globe. However, the amount of sediment in different reservoirs, and the rates at which sediments move between reservoirs, can shape the biological functioning of coral reefs. Unfortunately, relatively few studies have examined reef sediment dynamics, and associated bio-physical drivers, simultaneously over matching spatial and temporal scales. This has led to a partial understanding of how sediments and living reef systems are connected, especially on clear-water offshore reefs. To address this problem, four sediment reservoirs/sedimentary processes and three bio-physical drivers were quantified across seven different reef habitats/depths at Lizard Island, an exposed mid-shelf reef on the Great Barrier Reef. Even in this clear-water reef location a substantial load of suspended sediment passed over the reef; a load theoretically capable of replacing the entire standing stock of on-reef turf sediments in just 8 h. However, quantification of actual sediment deposition suggested that just 2 % of this passing sediment settled on the reef. The data also revealed marked spatial incongruence in sediment deposition (sediment trap data) and accumulation (TurfPod data) across the reef profile, with the flat and back reef emerging as key areas of both deposition and accumulation. By contrast, the shallow windward reef crest was an area of deposition but had a limited capacity for sediment accumulation. These cross-reef patterns related to wave energy and reef geomorphology, with low sediment accumulation on the ecologically important reef crest aligning with substantial wave energy. These findings reveal a disconnect between patterns of sediment deposition and accumulation on the benthos, with the 'post-settlement' fate of sediments dependent on local hydrodynamic conditions. From an ecological perspective, the data suggests key contextual constraints (wave energy and reef geomorphology) may predispose some reefs or reef areas to high-load turf sediment regimes.

Sedimentation of a starch microsphere: What is usually missed and why?

Gravimetric sedimentation is known as a relatively simple method of determining density of spherical particles. When the method is applied to water-swollen starch microparticles of about submillimeter sizes, it becomes evident that a careful selection of the experimental setup parameters is needed for producing accurate testing results. The main reason for this is that the mean particle density is very close to the density of water, and therefore, a dynamic model accounting for the so-called Bassett history force should be employed for describing the unsteady accelerating particle settling. A main novelty of this study consists in deriving a priori estimates for the settling time and distance.

Large-scale sediment and phosphorus transport in the Three Gorges Reservoir based on a new reservoir operation method

Change of hydrodynamic conditions is a key factor inducing sedimentation, water eutrophication and algal blooms in the Three Gorges Reservoir (TGR). How to mitigate sedimentation and phosphorus (P) retention by improving hydrodynamic conditions in the Three Gorges Reservoir area (TGRA) is an urgent issue in the study of sediment and water environment. In this study, a Hydrodynamic-Sediment-Water quality model for the whole TGRA is proposed considering sediment and P inputs from numerous tributaries, and a new reservoir operation method namely the tide-type operation method (TTOM) is used to investigate the large-scale sediment and P transport in the TGR based on the model. Results indicate that the TTOM can reduce sedimentation and total phosphorus (TP) retention in the TGR. Compared with the actual operation method (AOM), sediment outflow and sediment export ratio (Eratio) of the TGR increased about 17.13% and 1%-3% in 2015-2017, and sedimentation decreased about 3% under the TTOM. TP retention flux and retention rate (RE) decreased about 13.77% and 2%-4%. The flow velocity (V) and sediment carrying capacity (S*) increased about 40% in the local reach. Larger daily water level fluctuation at dam site is more conducive to reducing sedimentation and TP retention in the TGR. Sediment inputs from the Yangtze River, Jialing River, Wu River and other tributaries account for 59.27%, 11.21%, 3.81% and 25.70% of the total sediment inflow during 2015-2017, and TP inputs were 65.96%, 10.01%, 17.40% and 6.63%. In the paper, an innovative method is proposed to reduce sedimentation and P retention in the TGR under the given hydrodynamic conditions and related quantitative contribution driven by the proposed method is analyzed. The work is favorable for expanding the understanding of the hydrodynamic and nutrition flux changes in the TGR, and provides a new perspective for water environment protection and reasonable operation of large reservoirs.

Distribution of artisanal fishing gears with impacts on sedimentation and benthic macroinvertebrate assemblages in Songkhla Lake, the largest lagoon in Thailand

The present study investigated the distribution and diversity of stationary fishing gears in Songkhla Lake and assessed the effects of the most abundant gear in the lake, the standing trap, on sedimentation and the abundance of benthic macroinvertebrates. Our survey revealed that six types of fishing gear were used: standing traps, fyke nets, fish aggregating devices, seabass net cages, small traps and stationary lift nets. The type of fishing gear used depended on the depth of water. The density of installed standing traps reached a maximum of 357 traps/km2, which was the highest density of any fishing gear installed on the lake. They were mainly set in the middle part of the lake, where the water was less than 2 m deep. Sedimentation was examined inside and outside the areas influenced by standing traps. Sediment samples were collected with sediment traps in the northeast and southwest monsoon seasons. Sedimentation rates inside and outside the areas influenced by standing traps differed at some sites but the pattern was not consistent across seasons. Sedimentation rates were higher in the northeast monsoon season with the average rate 1132.32 ± 43.73 (mean ± SE) g m-2day-1 when precipitation and run-off were higher and 323.98 ± 10.68 g m-2day-1 in the southwest monsoon or dry season. Moreover, the proportion of finer clay particles was greater in the sediment from the areas influenced by traps. Benthic macroinvertebrate communities between the two areas were different. A bivalve, Potamocorbula sp., which dominated benthic macroinvertebrate assemblages, had a higher abundance in areas influenced by traps. The effects of stationary fishing gears on sedimentation and benthic macroinvertebrates highlighted in this study suggest that the long-term deployment of these gears may affect food chain dynamics in this lagoon system. Ultimately, a proper regulation of the use of these gears may be needed.

Comparison of Mini-FLOTAC, Flukefinder and sedimentation techniques for detection and quantification of Fasciola hepatica and Calicophoron daubneyi eggs using spiked and naturally infected bovine faecal samples

BACKGROUND

Fasciolosis (Fasciola hepatica) and paramphistomosis (Calicophoron daubneyi) are two important infections of livestock. Calicophoron daubneyi is the predominant Paramphistomidae species in Europe, and its prevalence has increased in the last 10-15 years. In Italy, evidence suggests that the prevalence of F. hepatica in ruminants is low in the southern part, but C. daubneyi has been recently reported at high prevalence in the same area. Given the importance of reliable tools for liver and rumen fluke diagnosis in ruminants, this study evaluated the diagnostic performance of the Mini-FLOTAC (MF), Flukefinder(R) (FF) and sedimentation (SED) techniques to detect and quantify F. hepatica and C. daubneyi eggs using spiked and naturally infected cattle faecal samples.

METHODS

Briefly, negative bovine faecal samples were artificially spiked with either F. hepatica or C. daubneyi eggs to achieve different egg count levels: 10, 50 and 100 eggs per gram (EPG) of faeces. Moreover, ten naturally infected cattle farms from southern Italy with either F. hepatica and/or C. daubneyi were selected. For each farm, the samples were analysed individually only with MF technique and as pools using MF, FF and SED techniques. Bayesian latent class analysis (LCA) was used to estimate sensitivity and accuracy of the predicted intensity of infection as well as the infection rate in the naturally infected farms.

RESULTS

The outcome of this study showed that the highest number of eggs (F. hepatica and C. daubneyi) recovered was obtained with MF, followed by FF and SED in spiked infected samples at 50 and 100 EPG, while at lower infection levels of 10 EPG, FF gave the best results. Moreover, the sensitivity for all the techniques included in the study was estimated at > 90% at infection levels > 20 EPG for both F. hepatica and C. daubneyi eggs. However, MF was the most accurate of the three techniques evaluated to estimate fluke infection intensity. Nevertheless, all three techniques can potentially estimate infection rate at farm level accurately.

CONCLUSIONS

Optimization and standardization of techniques are needed to improve the FEC of fluke eggs.

Bifunctional clay based sorbent for 'Ochratoxin A' removal and wine fining

The treatment of Ochratoxin A (OTA), present in many agricultural commodities including wine, is unsatisfying even by adsorption to fining agents, such as the commercial clay montmorillonite (MMT), bentonite. We developed, characterized and tested new clay-polymer nanocomposites (CPNs) to optimize OTA treatment, adsorption and OTA-CPN removal by sedimentation, while maintaining product quality. OTA adsorption to the CPNs was optimized, fast and high, by varying polymer chemistry and configuration. OTA adsorption from grape juice was nearly 3 times higher by the CPN than by the MMT despite the larger particle size of the CPN, 125 vs. 3 µm, explained by diverse OTA-CPN interactions. The CPN outperformed MMT in terms of sedimentation rate (2-4 orders of magnitude faster), grape juice quality and volume loss (an order of magnitude less), highlighting the potential of applying composites for the removal of target molecules form beverages.

Suspended sediment load prediction modelling based on artificial intelligence methods: The tropical region as a case study

The impact of the suspended sediment load (SSL) on environmental health, agricultural operations, and water resources planning, is significant. The deposit of SSL restricts the streamflow region, affecting aquatic life migration and finally causing a river course shift. As a result, data on suspended sediments and their fluctuations are essential for a number of authorities especially for water resources decision makers. SSL prediction is often difficult due to a number of issues such as site-specific data, site-specific models, lack of several substantial components to use in prediction, and complexity its pattern. In the past two decades, many machine learning algorithms have shown huge potential for SSL river prediction. However, these models did not provide very reliable results, which led to the conclusion that the accuracy of SSL prediction should be improved. As a result, in order to solve past concerns, this research proposes a Long Short-Term Memory (LSTM) model for SSL prediction. The proposed model was applied for SSL prediction in Johor River located in Malaysia. The study allocated data for suspended sediment load and river flow for period 2010 to 2020. In the current research, four alternative models-Multi-Layer Perceptron (MLP) neural network, Support Vector Regression (SVR), Random Forest (RF), and Long Short-term Memory (LSTM) were investigated to predict the suspended sediment load. The proposed model attained a high correlation value between predicted and actual SSL (0.97), with a minimum RMSE (148.4 ton/day and a minimum MAE (33.43 ton/day). and can thus be generalized for application in similar rivers around the world.

Flocculation and dewatering of the Kaolin slurry treated by single- and dual-polymer flocculants

To mitigate the sudden increase in the production of waste engineering slurry, predominantly composed of Kaolinite, this study investigated the flocculation and dewatering of Kaolin slurry treated with single- and dual-polymer flocculants. The influence of the flocculant type and dosage, under single- and dual-dose conditions, on slurry's sedimentation and the filtration characteristics, were thoroughly discussed. The results reveal that the adsorption bridging of the polymeric flocculant, resulting from hydrogen bonds, exerts a more significant effect than electrical neutralization on forming a large floc. Under single-dose conditions, nonionic polyacrylamides (NPAMs) with the strongest adsorption bridging leads to biggest flocs and the maximum settling rate of 21.55 mm/s. Under the dual-dose conditions of polymeric aluminium chloride (PAC) and PAM, the size of the slurry's floc decreases with an increase in PAC dosage. Nevertheless, the filtration performance of the slurry improves, with the lowest SRF value of the flocculated slurry being 1.58 × 10¹¹ m/kg as 3‰ PAC and 3‰ NPAM is dosed. The improvement is explained by the micro-pore distribution of sludge. According to Mercury intrusion porosimetry (MIP) test, the slurry treated with the optimal dosage of dual-polymer flocculant exhibits the greatest sludge pore size and connected porosity (with a maximum value of 20.99%). Furthermore, the study discusses and compares the flocculation mechanism of single- and dual-polymer flocculants. The obtained results provide guidance for selecting appropriate flocculants for dewatering inorganic slurries, using different dewatering methods, such as gravitational thickening or filter pressing.

Deficiency in homologous recombination is associated with changes in cell cycling and morphology in Saccharomyces cerevisiae

Exposure of eukaryotic cells to ionizing radiation or clastogenic chemicals leads to formation of DNA double-strand breaks (DSBs). These lesions are also generated internally by chemicals and enzymes, in the absence of exogenous agents, though the sources and consequences of such endogenously generated DSBs remain poorly understood. In the current study, we have investigated the impact of reduced recombinational repair of endogenous DSBs on stress responses, cell morphology and other physical properties of S. cerevisiae (budding yeast) cells. Use of phase contrast and DAPI-based fluorescence microscopy combined with FACS analysis confirmed that recombination-deficient rad52 cell cultures exhibit chronically high levels of G₂ phase cells. Cell cycle phase transit times during G₁, S and M were similar in WT and rad52 cells, but the length of G₂ phase was increased by three-fold in the mutants. rad52 cells were larger than WT in all phases of the cycle and displayed other quantifiable changes in physical characteristics. The high G₂ cell phenotype was abolished when DNA damage checkpoint genes, but not spindle assembly checkpoint genes, were co-inactivated with RAD52. Several other RAD52 group mutants (rad51, rad54, rad55, rad57 and rad59) also exhibited the high G₂ cell phenotype. The results indicate that recombination deficiency leads to accumulation of unrepaired DSBs during normal mitotic growth that activate a major stress response and produce distinct changes in cellular physiology and morphology.

Effects of size and surface charge on the sedimentation of nanoplastics in freshwater

The environmental issues caused by nanoplastics (NPs) are increasingly noticeable. Environmental behavior study of the NPs could provide vital information for their environmental impact assessment. However, associations between NPs' inherent properties and their sedimentation behaviors were seldom investigated. In this study, six types of PSNPs (polystyrene nanoplastics) with different charges (positive and negative) and particle sizes (20-50 nm, 150-190 nm and 220-250 nm) were synthesized, and their sedimentations under different environmental factors, (e.g., pH value, ionic strength (IS), electrolyte type and natural organic matter) were investigated. Results displayed that both particle size and surface charge would affect the sedimentation of PSNPs. The maximum sedimentation ratio of 26.48% was obtained in positive charged PSNPs with size of 20-50 nm, while the minimum sedimentation ratio of 1.02% was obtained in negative charged PSNPs with size of 220-250 nm at pH 7.6. The pH value shift (range of 5-10) triggered negligible changes of sedimentation ratio, the average particle size and the Zeta potential. Small size PSNPs (20-50 nm) showed higher sensitivity to IS, electrolyte type and HA condition than large size PSNPs. At high IS value ( [Formula: see text]  = 30 mM or IS_NaCl = 100 mM), the sedimentation ratios of the PSNPs all increased differently according to their properties, and the sedimentation promoting effect of CaCl₂ was more significant on negative charged PSNPs than positive charged PSNPs. When [Formula: see text] increased from 0.9 to 9 mM, the sedimentation ratios of negative charged PSNPs increased by 0.53%-23.49%, while that of positive charged PSNPs increased by less than 10%. Besides, humic acid (HA) addition (1-10 mg/L) would lead to a stable suspension status for PSNPs in water with different degree and perhaps different mechanism due to their charge characteristics. These results showed new light on influence factor studies of NPs' sedimentation and would be helpful for further knowledge of NPs' environmental behaviors.

Impact of sand bund removal on seagrass ecosystems: A study of macrobenthic community structure and correlation with macrophytes cover and sediments

This study investigated the impacts of the removal of sand bund on the macrobenthos community structure, seagrass cover, and sediment particle size in Merambong Shoal, Malaysia. The reclamation project deposited sand bund in the middle of Merambong seagrass shoal, resulting in its division into northern (NS) and southern (SS) halves. Ecosystem changes were monitored over a 31-month period using the transect lines method. Bi-monthly samples were collected for assessment. The results revealed a substantial decline in macrobenthos densities compared to previous studies. However, after the removal of the sand bund, there was a significant increase in macrobenthos density, specifically Polychaeta and Malacostraca, at NS. Seagrass cover at NS was initially lower than SS but showed an increase after the complete removal of the sand blockage. Sediment particle analysis reported a higher silt percentage at NS, indicating greater sedimentation at NS, which was partially sheltered from wave actions.

Technology in scientific practice: how H. J. Muller used the fruit fly to investigate the X-ray machine

Since the practice turn, the role technologies play in the production of scientific knowledge has become a prominent topic in science studies. Much existing scholarship, however, either limits technology to merely mechanical instrumentation or uses the term for a wide variety of items. This article argues that technologies in scientific practice can be understood as a result of past scientific knowledge becoming sedimented in materials, like model organisms, synthetic reagents or mechanical instruments, through the routine use of these materials in subsequent research practice. The proposed theoretical interpretation of technology is examined through a case where a model organism-Drosophila melanogaster-acted as a technology for investigating a contested biological effect of a mechanical instrument: Hermann J. Muller's experiments on X-ray mutagenicity in the 1920s. The article reconstructs how Muller employed two synthetic Drosophila stocks as tests for measuring X-rays' capacity to cause genetic aberration. It argues that past scientific knowledge sedimented in the Drosophila stocks influenced Muller's perception of X-ray-induced mutation. It further describes how Muller's concept of X-ray mutagenicity sedimented through the adoption of X-ray machines as a ready-made resource for producing mutants by other geneticists, for instance George Beadle and Edward Tatum in their experiments on Neurospora crassa, despite ongoing disputes surrounding Muller's conclusions. Technological sedimentation is proposed as a potential explanation why sedimentation and disputation may often coexist in the history of science.

Spatial sedimentation and plant captured sediment within seagrass patches

Habitat degradation in coastal ecosystems has resulted in the fragmentation of coastal aquatic vegetation and compromised their role in supplying essential ecological services such as trapping sediment or sequestering carbon. Fragmentation has changed seagrass architecture by decreasing the density of the canopy or engendering small patches of vegetated areas. This study aims to quantify the role different patch sizes of vegetation with different canopy densities have in the spatial distribution of sediment within a patch. To this aim, two canopy densities, four different patch lengths, and two wave frequencies were considered. The amounts of sediment deposited onto the bed, captured by plant leaves, remaining in suspension within the canopy, and remaining in suspension above the canopy were used to understand the impact hydrodynamics has on sediment distribution patterns within seagrass patches. In all the cases studied, patches reduced the suspended sediment concentrations, increased the capture of particles in the leaves, and increased the sedimentation rates to the bed. For the lowest wave frequency studied (0.5 Hz), the sediment deposited to the bottom was enhanced at canopy edges, resulting in spatial heterogeneous sedimentation patterns. Therefore, restoration and preservation of coastal aquatic vegetation landscapes can help face future climate change scenarios where an increase in sedimentation can help mitigate predicted sea level rise in coastal areas.

Coproscopical diagnosis of patent Fasciola hepatica infections in sheep - A comparison between standard sedimentation, FLUKEFINDER® and a combination of both

The liver fluke Fasciola hepatica is a highly pathogenic and zoonotic trematode with a cosmopolitan distribution. In livestock, infections may lead to significant economic losses if not diagnosed promptly and treated effectively. Particularly for small ruminants, the standard method for the detection of fluke infection is based on coproscopical methods such as the sedimentation method, which detects F. hepatica eggs in faecal samples. In this respect a recent innovative coproscopical approach to diagnose patent infections is the FLUKEFINDER® method, which relies on differential sieving before sedimentation. These two methods and a combination of both methods that allows larger amounts of faeces to be processed with the FLUKEFINDER® apparatus were compared, to assess which method is most appropriate to determine the prevalence and intensity of F. hepatica egg shedding. The methods were compared for their ability to recover eggs from ovine faecal samples containing different numbers of fluke eggs per gram (EPG) of faeces and diluting the samples further by mixing with faeces from uninfected sheep. To compare the specificity of the test procedures, positive and negative samples with a low EPG were analysed in parallel by an investigator blinded to the nature of the samples. Significant differences concerning the EPG outcome were found: The FLUKEFINDER® method demonstrated the highest EPG values (p < 0.001) in the undiluted samples as well as in all mixing levels, followed by the modified FLUKEFINDER® method. The standard sedimentation showed the lowest EPG values and the highest variability between technical replicates. The precision of the FLUKEFINDER® method and the modified FLUKEFINDER® method were significantly higher than the precision of the standard sedimentation as determined by comparison of variability between technical replicates. The highest raw egg counts were detected using the modified FLUKEFINDER® method. The FLUKEFINDER® method and the combined method showed a sensitivity of 100 % even at the lowest egg concentrations, whereas the sensitivity of the standard sedimentation was 98.1 % for the same set of samples (i.e. one false negative sample). In a separate investigation aiming to estimate the specificity no differences were found between the three methods: all protocols showed 100 % specificity and were able to correctly distinguish between truly positive and truly negative samples without any evidence of cross-contamination between positive and negative samples processed in parallel.

Investigation of the reduction of sediment deposition and river flow resistance around dimpled surface piers

To reduce sediment accumulation in urban rivers due to the influence of cylindrical bridge piers on river flow resistance, the hydraulic performances of cylindrical piers were investigated using the computational fluid dynamics software FLOW 3D and compared with experimental data. The method included scouring and sedimentation analysis of piers and showed high accuracy at predicting experimental data. A dimpled surface pier was used as the model, and a series of simulations were conducted to evaluate its hydraulic performance. The results showed that scouring extents of a dimpled surface pier are larger than those of a cylindrical pier under different working conditions. This difference helped reducing sludge sedimentation at the bottom of the river in the former. The ratio of the maximum sedimentation height to the pier diameter ([Formula: see text]), ratio of the sedimentation area, and cross-sectional area of the dimpled surface pier ([Formula: see text]) are all smaller than those of a cylindrical pier at different flow velocities, indicating that dimpled surface piers have a lower silting probability. Compared with cylindrical piers, dimpled surface piers offer less interference to turbulent flow and generate a small-scale spiral flow; a lower lateral velocity is also obtained behind the dimpled surface pier, which leads to lower flow resistances and lower energy dissipation, which helps scour.

Size Distribution Analysis of the Adeno-Associated Virus Vector by the c(s) Analysis of Band Sedimentation Analytical Ultracentrifugation with Multiwavelength Detection

Adeno-associated virus (AAV) vector is a promising platform for in vivo gene therapy. The accurate assessment of distribution state of particles contained in AAV vector samples is one of the most important and challenging matters and is necessary because the product-related impurities with the capsid structure (empty particles, intermediate particles, and aggregates) could be a possible cause of reducing the therapeutic efficacy and enhancing the unfavorable immune response. In this study, we report an effective approach for size distribution analysis with component identification. A small amount of AAV vectors were used by the analytical zone centrifugation c(s) analysis of band sedimentation analytical ultracentrifugation (BS-AUC) with multiwavelength detection. Using PBS/H₂¹⁸O, the concentration of each component could be determined in BS-AUC with high resolution. Compared with the sedimentation velocity AUC (SV-AUC), which generally requires 2 × 10¹² vg of AAV vectors, BS-AUC could be performed with about 1/25 of the AAV vector amount at 260 nm detection and ideally with about 1/50 of the AAV vector amount at 230 nm detection (4 × 10¹⁰ vg), depending on the extinction coefficient of the AAV sample at each wavelength. According to the limit of quantification of this BS-AUC, 6.3 × 10¹¹ cp mL^-1 of empty particle (EP) and 4.4 × 10¹¹ vg mL^-1 of full particle (FP) could be quantified for 4 × 10¹⁰ vg in 15 µL of AAV8-CMV-EGFP. These results demonstrated that proposed BS-AUC approach we established here can compensate for the drawback in terms of the sample amount of SV-AUC.

A simple approach for coffee-ring suppression yielding homogeneous drying patterns of ZnO and TiO2 nanoparticles

Evaporation-induced self-assembly in colloidal droplets is a method for organising nanoparticles on substrates, with various resulting patterns. The coffee-ring pattern is among the most common ones, but its non-uniformity limits its applicability, which led to efforts for developing coffee-ring suppression strategies. Considering the wide applicability of ZnO and TiO₂ nanoparticles, there is a high demand for practical means to deposit them as uniform films. Here, we present a simple approach for obtaining highly uniform thin films of ZnO and TiO₂ nanoparticles by drop-coating in ambient conditions, without using surfactants or other surface chemistry modifications. Disc-like films were obtained via a restricted evaporation achieved by covering the droplets with a lid during drying, seconded by the relatively high sedimentation rate of these nanoparticles. To better understand the assembly mechanism, the influence of suspension concentration, type and temperature of the substrate, droplet volume, colloid type, and evaporation rate were studied. The method allows preparing disc-like nanoparticle films with a good control over their diameter and thickness, onto different kinds of substrates (glass, Si, polyethylene terephthalate, polystyrene). By fabricating both two-dimensional lattices and custom disc patterns we highlight the versatility of this drop-coating method and its potential for, e.g., automatized serial production processes.

Multi-indicator 'state space' approach to assessing changes in shallow urban reef ecosystem health

Tracking changes in ecosystem health is an important objective for environmental managers, but is often limited by an understanding of what constitutes a "healthy" system and how to aggregate a range of health indicators into a single meaningful metric. We used a multi-indicator 'state space' approach to quantify changes over 13 years in reef ecosystem health in an urban area that has undergone intense housing development. Based on nine health indicators (macroalgal canopy length and biomass, macroalgal canopy and habitat functional diversity, mobile and predatory invertebrate density and size, total species and non-indigenous species richness), we found that the overall health of the reef community declined at five of the ten study sites. This decline was associated with a large collapse in the gastropod community, a shortening of macroalgal canopies and an increase in the number of non-indigenous species. While the cause of this decline and mechanisms responsible are not fully understood, the decline correlated with an increase in sediment cover on the reefs and warming ocean temperatures over the monitoring period. The proposed approach provides an objective and multifaceted quantitative assessment of ecosystem health that can be easily interpreted and communicated. These methods could be adapted to other ecosystem types to inform management decisions regarding future monitoring, conservation and restoration priorities to achieve greater ecosystem health.

Gravity sedimentation of eukaryotic algae Euglena gracilis accelerated by ethanol cultivation

Euglena gracilis (E. gracilis) is a unicellular microalga with various applications in medicine, agriculture, aquaculture, health supplement, and jet fuel production. Euglena possibly solves population growth and exhaustion of fossil resources. Efficient cell harvesting is needed for the industry, and the gravity sedimentation method is low cost and does not require any equipment, although it has low efficiency. This study showed that the gravity sedimentation of E. gracilis cells is improved by cultivation in the presence of ethanol (EtOH). The gravity sedimentation of E. gracilis cells cultivated under 0.5% or 1.0% EtOH conditions was faster than that cultivated without EtOH. The mean calculated cell diameter was also found to be largest in cells cultivated under 0.5% or 1.0% EtOH conditions compared to that in cells cultivated without EtOH. Intracellular paramylon content, cell shapes, and motility differed between cells cultivated under 0.5% or 1.0% EtOH conditions and in the absence of EtOH. The results suggest that E. gracilis cultivation with EtOH leads to increased cell productivity, paramylon production, and efficient cell harvesting. KEY POINTS: • Euglena gracilis is an edible microalga producing value-added metabolites. • Ethanol addition upregulates E. gracilis growth and paramylon accumulation. • Gravity sedimentation is accelerated by ethanol-grown E. gracilis cells.

Sedimentation assessment using hydrological simulation and bathymetry survey: The case of river Amissa drainage basin, Ghana

Studies on freshwater bodies in Ghana for their sustainability are mostly concentrated on a few large rivers. However, other equally important rivers that do not attract research attention provide varied services and benefits to inhabitants and living organisms in their riparian communities. The basin of River Amissa as a major source of freshwater supply for several communities within its catchment has undergone various changes due to rapid socioeconomic and increasing anthropogenic disturbances. This consequently has led to increased sediment yield on the reservoir beside the river and the river basin itself. Hence the need to estimate the amount of sediment accumulated in the reservoir and in the river's catchment for their sustainability and management purposes. Sediment yield in the reservoir and the river basin were estimated using a bathymetric survey integrated with Geographic Information System (GIS) and the Soil and Water Assessment Tool (SWAT) hydrological model respectively. Results from the bathymetric survey estimated the current capacity of the reservoir to be 4,321,060 m³. Reservoir storage capacity lost to sedimentation was 1,438,940 m³ representing 25% of the reservoir volume. Additionally, the SWAT (Arc SWAT) performance was very good with Nash-Sutcliffe efficiency coefficient (NSE) for calibration and validation being 0.88 and 0.84 respectively. For the entire 28-year period, simulated sediment yield increased by 10,263 tons per kilometer square.

Soil erosion risk for farming futures: Novel model application and validation to an agricultural landscape in southern England

Increasingly, agricultural land managers are seeking new approaches for understanding the potential challenges posed by sediment connectivity across catchments from source to sink, and implications for delivery of ecosystem services determined by the condition of natural capital assets. Connectivity indices have been frequently applied in the calculation of risk in spatial and temporal assessment frameworks, and tools which facilitate rapid modelling and mapping of soil erosion risk using broad-scale environmental data are therefore of considerable interest. One such indicative tool is SCIMAP (Sensitive Catchment Integrated Mapping and Analysis Platform), which highlights where sediment runoff is likely to occur and be delivered to a watercourse by simulating the generation of saturation-excess overland flow. In this paper, we examine the utility of SCIMAP for exploring the changing nature of soil erosion risk as a function of land use change in the lower Rother catchment in West Sussex, southern England through the formulation of a suite of foresight scenarios informed by knowledge of historical land cover conditions and current management practice. The study area has previously been investigated at the field scale in terms of locating and quantifying sources of erosion and areas where in-stream sedimentation manifests. Output risk values from all simulations were quantified, mapped and compared to highlight areas of greatest/lowest risk. An area was identified immediately north of the main Rother channel that consistently exhibited greatest risk across each land cover scenario. We explore (i) the spatial and temporal variation in modelled risk and (ii) the utility value of SCIMAP for agricultural land-managers and policy-makers in generating robust risk estimates of soil erosion and in-stream sedimentation, and challenges with model verification in a foresight context.

Source and sequestration of sediment organic carbon from different elevation zones in estuarine wetland, North China

Estuarine wetland plays an important role in regulating global carbon cycle due to high terrestrial carbon input and burial. However, it is unclear how the source and sequestration of sediment organic carbon (SOC) in estuarine wetlands changes under the anthropogenic impact in the past century. In this study, combining parameters of TOC/TN ratios, δ¹³C, δ¹⁵N and ²¹⁰Pb-chronology, temporal trends of SOC source and sequestration flux in Liaohe estuarine wetland were studied. The results showed that the source of organic carbon in Liaohe estuarine wetland was dominated by terrestrial input (contribution >60 %). Due to vegetation, TOC in shallow reed marsh was significantly higher than that of bare beach and subtidal flat. Affected by elevation, the sediment mass accumulation rate (MAR, kg·m^-2·yr^-1) showed differences in reed marsh (C1), bare beach (C2) and subtidal flat (C3), which were 6.57, 13.56 and 13.25 respectively in the past century. MAR fluctuated over time, it showed an overall increasing trend, especially since the 1980s. Correspondingly, the sequestration flux of SOC (SF-SOC, g·m^-2·yr^-1) showed an overall increasing trend with average of 82.84 (reed marsh), 151.93 (bare beach) and 123.71 (subtidal flat). Comparing to TOC, the higher MAR had a more distinct effect on carbon sequestration in Liaohe estuarine wetland. The difference in sedimentation rate and carbon sequestration are linked to the changes in sediment flux of riverine input and land utilization in the catchment area due to human activities in recent decades, including the construction of reservoirs, dams and local ditch wharf.

Shift of major driver for chemical weathering from the natural control to human dominance since 1980s in the Taihu watershed, China

Anthropogenic acidification has become a concerned problem in the Taihu region; however, how it affected the regional weathering rate, especially at the different sub-watershed levels has hardly been studied. To reveal the impact of human activities on watershed weathering and water chemistry in Taihu sub-watersheds, historical water chemistry data (1950s-1970s) and recent water samples (2018-2021) of the local river systems, as well as sediment samples of Taihu lake were collected and analyzed, and a linear addition mass balance method was used to determine the weathering rate at the sub-watershed level. The results indicated that, compared with 60 years ago, the current weathering rate of carbonates and silicates in the Taoge water system (TG) was the highest, reaching 67.2 and 11.4 t·km^-2·a^-1, increasing by 4.1 and 2.7-folds, respectively; and meanwhile the carbonate and silicate weathering rates increased by 3.1 and 4.9-folds in the Nanhe water system (NH), and 5.2 and 3.4-folds in the Tiaoxi water system (TX), respectively. The increasing rate was significantly correlated to the atmospheric SO₂ concentration in different sub-watersheds and was affected by the sub-watershed lithology, e.g., TX had a higher increase rate of silicate weathering due to the wider distribution of silicates in this sub-watershed than the other two. The sediment evidence of Na/K and Ca/Al on the profile in different lake parts, which was influenced by different influx river systems, confirmed that the overall intensity of watershed weathering was higher in TG than in the TX sub-watershed and was higher in the recent decade than 50-60 years ago. The accelerated weathering rate was found to present a definite consistency with the social and economic development in the watershed. Combined analyses of the accelerated weathering rate in the watershed and sedimentation evidence indicated that the major driving force for the watershed weathering has shifted from carbonic acid under the natural condition to human-induced sulfuric acid since 1980s.

Effects of Mn addittion, cooling rate and holding temperature on the modification and purification of iron-rich compounds in AlSi10MnMg(Fe) alloy

The use of secondary aluminum alloys in industry is still limited by the high Fe contents in recycled alloys. In general, the Fe-rich intermetallic compounds deteriorate the performance of secondary Al-Si alloys, specially the β-Fe phase. To mitigate the detrimental effects of iron, the influence of diferent cooling rates and holding temperatures on the modification and purification of iron-rich compounds in commercial AlSi10MnMg alloy with 1.1 wt % Fe was studied. According to the results obtained by CALPHAD calculations, the alloy was modified by adding a 0.7 wt%, 1.2 wt%. and 2.0 wt% of Mn. The phase formation and morphology of iron-rich compounds was systematically studied and correlated by different microstructural characterization techniques. The experimental results showed that the detrimental β-Fe phase can be avoided by adding at least 1.2 wt % of Mn at the studied cooling rates. Finally, the effect of different holding temperatures in the sedimentation of Fe-rich compounds also was studied. Hence, the gravitational sedimentation experiments at different holding times and temperatures were conducted to validate the feasibility of the methodology in different processing conditions. The experimental results showed a high Fe removal efficiency up to 64% and 61%, after a holding time of 30 min at 600 °C and 670 °C, respectively. The addition of Mn improved the Fe removal efficiency but not gradually, as the best results were obtained in the alloy containing 1.2 wt % Mn.

Dataset on rheological measurements of xanthan gum aqueous dispersions containing sodium chloride and settling dynamics of spheres and disks in these dispersions

This paper presents a dataset collected in laboratory experiments on the settling of solid spheres and disks in shear-thinning and viscoelastic aqueous solutions of xanthan gum with sodium chloride addition. Two types of spheres with density of 1.41 g/cm³ varying in diameter (3.00 mm and 1.59 mm) and four types of disks with density of 1.43 g/cm³ and thickness of 0.3 mm varying in diameter (1.5 mm, 2.0 mm, 2.5 mm, and 3.0 mm) were considered. A single particle was settling in a column filled with a test solution which varied in salt content (from 0 M to 0.9 M), while xanthan gum content was constant (1 g/L). The total of elven solutions were tested. For each experimental set, a sequence of images with a falling particle was captured using a camera with macro lenses. Dataset includes position of particle in time and enables the evaluation of settling velocity. Rheological measurements were carried out for each test solution to assess flow properties and viscoelasticity. The following measurements were performed: shear dependent viscosity, shear stress amplitude sweeps, frequency sweeps, the dependence of the first normal stresses difference on shear strain at constant frequency (1 Hz). Datasets may be useful in various areas on fluid mechanics and rheology, e.g., in research on the impact of salinity on rheological properties of exopolymer solutions, to develop numerical models on solid particles settling in non-Newtonian fluids, and in studies on the impact of exopolymers and electrolytes dissolved in water on settling dynamics of solid particles.

Impacts of multiple anthropogenic stressors on the transcriptional response of Gammarus fossarum in a mesocosm field experiment

BACKGROUND

Freshwaters are exposed to multiple anthropogenic stressors, leading to habitat degradation and biodiversity decline. In particular, agricultural stressors are known to result in decreased abundances and community shifts towards more tolerant taxa. However, the combined effects of stressors are difficult to predict as they can interact in complex ways, leading to enhanced (synergistic) or decreased (antagonistic) response patterns. Furthermore, stress responses may remain undetected if only the abundance changes in ecological experiments are considered, as organisms may have physiological protective pathways to counteract stressor effects. Therefore, we here used transcriptome-wide sequencing data to quantify single and combined effects of elevated fine sediment deposition, increased salinity and reduced flow velocity on the gene expression of the amphipod Gammarus fossarum in a mesocosm field experiment.

RESULTS

Stressor exposure resulted in a strong transcriptional suppression of genes involved in metabolic and energy consuming cellular processes, indicating that G. fossarum responds to stressor exposure by directing energy to vitally essential processes. Treatments involving increased salinity induced by far the strongest transcriptional response, contrasting the observed abundance patterns where no effect was detected. Specifically, increased salinity induced the expression of detoxification enzymes and ion transporter genes, which control the membrane permeability of sodium, potassium or chloride. Stressor interactions at the physiological level were mainly antagonistic, such as the combined effect of increased fine sediment and reduced flow velocity. The compensation of the fine sediment induced effect by reduced flow velocity is in line with observations based on specimen abundance data.

CONCLUSIONS

Our findings show that gene expression data provide new mechanistic insights in responses of freshwater organisms to multiple anthropogenic stressors. The assessment of stressor effects at the transcriptomic level and its integration with stressor effects at the level of specimen abundances significantly contribute to our understanding of multiple stressor effects in freshwater ecosystems.

Impact of nanoplastic debris on the stability and transport of metal oxide nanoparticles: role of varying soil solution chemistry

The release of metal-based nanoparticles (MNPs) and nanoplastic debris (NPDs) has become ubiquitous in the natural ecosystem. Interaction between MNPs and NPDs may alter their fate and transport in the sub-surface environment and have not been addressed so far. Therefore, the present study has explored the role of NPDs on the stability and mobility of extensively used MNPs, i.e., CuO nanoparticles (NPs) under varying soil solutions (SS) chemistry. In the absence of NPDs, a very high aggregation of CuO NPs observed in SS extracted from black, lateritic, and red soils, which can be correlated with ionic strength (IS) and type of ionic species. The sedimentation rate (k_sed(1/h)) for CuO NPs was >0.5 h^-1 in the case of these SS. Interestingly, the stability and sedimentation behavior of CuO NPs varied significantly in the presence of NPDs. The k_sed for CuO NPs decreased to half and found <0.25 h^-1 in the presence of NPDs in all SS. C/C₀ values in breakthrough curves increased drastically (black < alluvial < laterite < red) in presence of NPDs. Results suggest that the release of NPDs in the terrestrial ecosystem is a potential threat leading to increased mobility of MNPs in the environment.

Humic acid-mediated reduction in toxicity of Co3O4 NPs towards freshwater and marine microalgae in surfactant mixed medium

The ever-increasing applications of Co3O4 nanoparticles (NPs) have posed a serious concern about their discharge in the aquatic environment and ecotoxic implications. Being toxic towards aquatic species, the impact of other aquatic components such as dissolved organic matter (DOM), salinity, and surfactants are not studied sufficiently for their effect on the stability and ecotoxicity of Co3O4 NPs. The present study aims at the influence of humic acid (HA) on the toxicity of Co3O4 NPs in freshwater (C. minutissima) and marine (T. suecica) microalgae under surfactants mixed medium. The measure of % reduction in biomass and photosynthetic pigment were used as toxicity endpoints. Among various tested concentrations of HA, 25 mg/L HA was found suitable to minimize the NP's toxicity with or without the presence of surfactants. Co3O4 NPs mediated reduction in biomass of C. minutissima was significantly minimized by the cumulative effect of HA with T80 (51.68 ± 4.55%) followed by CTAB (46.23 ± 5.62%) and SDS (42.60 ± 2.46%). Similarly, HA with T80 (26.93 ± 6.38%) followed by SDS (17.02 ± 6.64%) and CTAB (13.01 ± 3.81%) were found to minimize the growth inhibitory effect of Co3O4 NPs in T. suecica. The estimation of chlorophyll - a content also indicated that microalgae treated with HA could maintain their photosynthetic ability more than control even in the co-presence of surfactants. Also, the reduced toxicity of Co3O4 NPs were attributed to an increase in hydrodynamic sizes of HA-treated Co3O4 NPs in both marine media (f/2) and freshwater media (BG11) due to increased aggregation and faster sedimentation of Co3O4 NPs.

Occurrence and accumulation of heavy metals in algal turf particulates and sediments on coral reefs

Algal turfs form a critical interface on coral reefs that interacts with several key ecosystem processes. While we know these turfs have a remarkable propensity to accumulate sediments, which can have a range of ecosystem impacts, their role as sinks for heavy metals remains largely unexamined. Here we quantified the concentration of 15 metals in algal turf sediments from Lizard Island and Orpheus Island on the Great Barrier Reef, and specifically explored how the loads of arsenic, cobalt, iron and lead were related to turf length. Metal composition differed markedly between the two islands, with the composition at Orpheus Island suggesting closer links to terrestrial sediment sources. Furthermore, metal loads increased significantly with turf length, suggesting that longer turfs can accumulate these pollutants on reefs. Given that algal turfs are a crucial component of herbivorous/detritivorous trophic pathways, this could represent a key juncture at which these metals enter food chains.

Optimization of coagulation and sedimentation conditions by turbidity measurement for nano- and microplastic removal

Plastic pollution has emerged as a potential threat to drinking water quality. Coagulation and sedimentation processes are suggested to be an effective way of removing small plastic particles from water. However, a conventional jar test consumes a large volume of plastic specimens, producing secondary wastes and hindering a quick optimization of the treatment processes for nano/microplastic removal. This study investigates the monitoring of nano- and microplastic behavior (0.1, 1, and 10 μm-sized polystyrene) in coagulation and sedimentation processes by a simple turbidity measurement. The coagulation and the subsequent floc sedimentation of the plastic particles could be observed in a turbidity vial with a small volume (∼15 mL), allowing a fast screening of coagulant type, dose, sedimentation time, and water environment. In particular, the physicochemical properties of coagulants could be screened in the turbidity monitoring, where the hydrophobic interaction is identified to be important for the coagulation of nano-sized plastic particles. The optimal coagulation/sedimentation conditions from the turbidity monitoring could be applied to the jar test, achieving the high removal efficiencies of nano/microplastic particles. The plastic removal after the coagulation/sedimentation process could be estimated based on linearity between the plastic concentration and the turbidity. The turbidity-driven removal efficiency well corresponds to that derived from the mass-based calculation of the jar test when with a complete floc settling. Our findings suggest that the turbidity measurement can provide a rational optimization of the water treatment processes for the effective removal of nano- and microplastics.

Sediment trap height affects mass, particle size, and biogeochemical composition of material collected in an equatorial coral reef

Anthropogenic sedimentation is a major contributor to the worldwide decline in coral cover. Resuspension of benthic material can exacerbate the threat to corals, but evidence of vertical sediment gradients is limited. Here, we installed sediment traps at 10, 20, 30, 40, and 50 cm above the substrate at three equatorial reef sites for three months and determined the dry mass, particle size, and biogeochemical composition of the material collected. As the trap mouth height increased from 10 to 50 cm, dry mass decreased as sediments became finer, poorer in carbonate, and richer in silicate. Despite among-site differences in collected sediment, this vertical gradient was present in all trap arrays, likely driven by resuspension mechanisms on seabed sediments. These results have implications for coral vertical ecology and underline the importance of standardising sediment collection protocols.

Widespread occurrence of microplastics in marine bays with diverse drivers and environmental risk

Microplastic contamination in the sediment of marine bays has attracted widespread attention, whereas the distribution, sedimentation, morphology and risk of microplastics at regional scale remain poorly understood. By introducing a data mining framework into microplastic research, we compiled a microplastic dataset of 649 samples from 24 bays to enhance the understanding of geographical difference and drivers, transfer, composition profile and environmental risk of sedimental microplastics. Microplastic abundance varied from 0.72 to 1963.96 items/kg dry weight, with higher concentrations mainly occurring in East Asian bays. The spatial pattern in abundance was driven by the river plastic emissions, aquaculture production and hydrodynamic condition. A significantly positive correlation between microplastic abundance in water and sediment was found, and microplastic sedimentation was related to polymer density, hydrodynamic conditions and sediment properties. The dominant shape and polymer of sedimental microplastics were fiber and polypropylene, respectively, and the similarity of microplastic composition decreased with increasing geographical distance. The environmental risks of microplastics were partitioned into three classes (Rank II-Rank IV) with a two-dimensional assessment system considering the bioavailability and toxicity of microplastics, and Asian bays were identified as potential high-risk areas. To reduce the environmental risk of sedimental microplastics in bays, priority should be given to the removal of microfibers, and control measures depend on the risk classes and dominant polymers. Microplastic abundance and composition were significantly affected by methodological choices regarding sampling, pretreatment and identification, suggesting a unified methodology is essential to further enhance our knowledge on the distribution and risk of microplastics in marine bays.

Reservoir sedimentation and spatiotemporal land use changes in their watersheds: the case of two sub-catchments of the White Volta Basin

Reservoir storage is compromised by sedimentation for which reason it has become an important matter in reservoir operation and management. While many studies have investigated sediment deposition rate in reservoirs, few have analyzed reservoir sedimentation from their catchment's land use change perspective. Based on bathymetric survey conducted on two reservoirs in the White Volta Basin in 2020 and analysis of four Landsat satellite imagery (1986, 1996, 2006, and 2020) within their watersheds, this study assessed the land cover change within the watersheds to draw inferences on the rate of sedimentation of the reservoirs located downstream of their catchments. The results revealed rapid sedimentation in the small-sized reservoir (Vea), with an annual sedimentation rate of 0.304% and a nominal sedimentation rate of 0.17% for the mid-sized reservoir (Tono). Furthermore, the savannah forest within the Vea catchment declined drastically from 29.4% (1985) to 9.9% (2020) influenced by the rapid expansion of farmlands from 18.7% to 47.9% within the same period, respectively. On the other hand, the savannah forest within the Tono catchment declined from 34.7% (1985) to 21.6% (2020) due to farmland expansion from 19.2% to 39% within the same period, respectively. The higher sedimentation rate observed in the small-sized reservoir was observed to be worsened by extensive tree cover removal in its catchment. Therefore, land cover characteristics within a watershed have a significant bearing on the rate of sedimentation in the reservoirs located downstream of their catchment. Hence, adopting a multi-sectorial approach to dealing with land use management is necessary to sustain reservoirs' storage.

Significant input of organophosphate esters through particle-mediated transport into the Pearl River Estuary, China

Most organophosphate esters (OPEs) enter the marine environment through atmospheric deposition and surface runoff, yet the role of particle-mediated transport in their inputs and loss processes remains poorly understood. To fill this knowledge gap, samples of size-segregated atmospheric particles, suspended particulate matter (SPM) in seawater, and sediments in the Pearl River Estuary (PRE) were collected and analyzed for OPEs. Total concentrations of atmospheric particulate OPEs showed a decreasing trend with increasing offshore distance in the PRE. The spatial and vertical distribution patterns of OPEs in SPM were diverse, which could be largely affected by physicochemical properties of SPM, marine microbial activities, hydrodynamic conditions, and environmental factors. Sediment in the region close to Modaomen outlet was subject to relatively high OPE concentrations. Approximately 24,100 and 65,100 g d^-1 of particulate OPEs were imported into the PRE through atmospheric deposition and surface runoff, respectively; 83,200 g d^-1 of which were exported to the open sea. The input and environmental fate of particulate OPEs were found to be dependent on sources, particulate media, and chemical species. The present study provides insights into the influence of OPEs in the PRE through particle-mediated transport and calls for more concern on anthropogenic impact on the estuary.

Escherichia coli removal in a treatment wetland - pond system: A mathematical modelling experience

A full-scale treatment wetland (TW) (100 inhabitants, 14 m³·d^-1), composed of two horizontal subsurface flow wetlands (TW1-400 m² and TW2-200 m²) and a small pond (13 m²), has been evaluated for Escherichia coli (E. coli) removal. The results indicate a global removal from 1.74·10⁶ to 685 MPN·100 mL^-1 (3.41 log units), reducing E. coli sufficiently to reach values suitable for reuse purposes such as agricultural reuse, without energy and reagent consumption. The small pond at the end of the treatment train plays an important role in E. coli removal and biodiversity enhancement. Data from TW1 and TW2 have been fitted to the P-k-C* model, giving values of 134 and 100 m·yr^-1 for the first-order kinetic reaction coefficient. For the pond, a process-based model using continuous stirred-tank reactor (CSTR) and a 3d-CFD model have been implemented and compared. The models indicate that solar disinfection and predation by daphnids are the most important mechanisms in the studied pond, representing 65% and 25% of the removal respectively. It can be concluded that CSTR can provide good results for small ponds and 3d-CFD model provides extra information, useful to enhance their design.

Molecular responses of a key Antarctic species to sedimentation due to rapid climate change

Rapid regional warming causing glacial retreat and melting of ice caps in Antarctica leads benthic filter-feeders to be exposed to periods of food shortage and high respiratory impairment as a consequence of seasonal sediment discharge in the West Antarctic Peninsula coastal areas. The molecular physiological response and its fine-tuning allow species to survive acute environmental stress and are thus a prerequisite to longer-term adaptation to changing environments. Under experimental conditions, we analyzed here the metabolic response to changes in suspended sediment concentrations, through transcriptome sequencing and enzymatic measurements in a highly abundant Antarctic ascidian. We found that the mechanisms underlying short-term response to sedimentation in Cnemidocarpa verrucosa sp. A involved apoptosis, immune defense, and general metabolic depression. These mechanisms may be understood as an adaptive protection against sedimentation caused by glacial retreat. This process can strongly contribute to the structuring of future benthic filter-feeder communities in the face of climate change.

Distribution of microplastics in benthic sediments of Qinghai Lake on the Tibetan Plateau, China

Although several studies of microplastics (MPs) with size <5 mm in lake sediments focused on lakeshore areas, there have been no studies of distributions of MPs from lakeshores to the center of a lake. To test our hypothesis that MPs decrease from lakeshore to the center, a study was conducted on the largest brackish lake on the remote and high-altitude Tibetan Plateau, China. Abundances and characteristics of MPs in 14 samples of surface sediment collected from a river bay, a lake bay, and a lake central area were investigated. Distributions were influenced by river inflow, tourism, and minimal activity of humans, respectively around Qinghai Lake. The mean abundance of MPs in sediments of Qinghai Lake was 393 ± 457 items/kg, dry mass (dm). Based on the range of MP abundances in surface sediments of lakes worldwide, Qinghai Lake was classified as being moderately polluted with MPs. The dominant color, shape, size, and polymer type of MPs in sediments were transparent, fiber, 0.05-1 mm, and polypropylene, respectively. The river bay had a mean abundance of MPs two-fold greater than either the bay or central area of the lake. This indicates that the river catchment caused more pollution with MPs, while the central area of the lake was not a sink for MPs. Spatial trends of MPs in sediments from the shore to the center of the lake differed among areas, and were significantly related to wind, lake current, sedimentation rate, water- and sediment-properties, water depth, and proximity to land sources of MPs.

Modelling of Harvesting Techniques for the Evaluation of the Density of Microalgae

A better estimation of the density of cells has great relevance in the design of harvesting units. In the case of microalgae, the density is a function of the internal composition, which in turn is affected by external environmental conditions. The density of microalgae is often regarded as a constant or a generic value is retrieved from literature. This study proposes a procedure to evaluate the density of Chlorococcum sp. with simple sedimentation and centrifugation experiments coupled with the population balance equation (PBE), which is solved numerically. The density of cells is not constant; instead, it is a function of the size of particles, which in turn changes with the cells' phase of their life cycle. The calculated cellular density ranged between 1000 and 1100 kg m^-3 in function of the cell size in both the sedimentation and centrifugation tests. The method can be extended to other microalgae species as well as to other types of cells.