Particle Size Fractions Research Articles

Tracing sources of inorganic suspended particulate matter in the Great Barrier Reef lagoon, Australia

Water clarity on the inshore Great Barrier Reef (GBR) is greatly influenced by terrestrial runoff of suspended particulate matter (SPM). Catchment sediment tracing studies often do not extend into the marine environment, preventing the analysis of preferential marine transport. This study employs novel collection and sediment tracing techniques to examine the transport of the terrigenous ‘mineral’ component of plume SPM within the GBR lagoon for two flood events. Utilising geochemical, radionuclide and clay mineral analysis, we trace terrigenous mineral sediments > 100 km from the river mouth. We show that the SPM geochemistry is highly influenced by particle-size fractionation, desorption, and dilution within the plume, rendering traditional tracing methods unviable. However, the ratios of rare earth elements (REE) to thorium (Th) provide stable tracers of mineral SPM transported across the catchment to marine continuum and allow the identification of discrete catchment sources for each flood event. Plume sediment radionuclides are also stable and consistent with sub-surface erosion sources.

Application of Multivariate Tromp Functions for Evaluating the Joint Impact of Particle Size, Shape and Wettability on the Separation of Ultrafine Particles via Flotation

Froth flotation predominantly separates particles according to their differences in wettability. However, other particle properties such as size, shape or density significantly influence the separation outcome as well. Froth flotation is most efficient for particles within a size range of about 20–200 μm, but challenges arise for very fine or coarse particles that are accompanied by low recoveries and poor selectivity. While the impact of particle size on the separation behavior in flotation is well known by now, the effect of particle shape is less studied and varies based on the investigated zone (suspension or froth) and separation apparatus used. Beyond these complexities, many particle properties are correlated, making it challenging to analyze the isolated impact of individual properties on the separation behavior. Therefore, a multidimensional perspective on the separation process, considering multiple particle properties, enhances the understanding of their collective influence. In this paper, the two-dimensional case is studied; i.e., a parametric modeling approach is applied to determine bivariate Tromp functions from scanning electron microscopy-based image data of the feed and the separated fractions. With these functions it is possible to characterize the separation behavior of particle systems. Using a model system of ultrafine (<10 μm) particles, consisting of either glass spheres or glass fragments with different wettability states as the floatable fraction and magnetite as the non-floatable fraction, allows for the investigation of the influence of descriptor vectors consisting of size, shape and wettability, on the separation. In this way, the present paper contributes to a better understanding of the complex interplay between certain descriptor vectors for the case of ultrafine particles. Furthermore, it demonstrates the benefits of using multivariate Tromp functions for evaluating separation processes and points out the limitations of SEM-based image measurements by means of mineral liberation analysis (MLA) for the studied particle size fraction.

Enhancing sub-catchment sediment source fingerprinting using chemometric models for DRIFTS in different particle size subfractions

Understanding the origins of sediment within stream networks is critical to developing effective strategies to mitigate sediment delivery and soil erosion in larger drainage basins. Sediment fingerprinting is a widely accepted approach to identifying sediment sources; however, it typically relies on labor-intensive and costly chemical analyses. Recent studies have recognized diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) as a non-destructive, cost-effective, and efficient alternative for estimating sediment contributions from multiple sources. This study aimed to assess (i) the effects of different particle size fractions on DRIFTS and conservatism tests, (ii) the effects of spectral pre-processing on discriminating sub-catchment spatial sediment sources, (iii) the efficiency of partial least squares regression (PLSR) and support vector machine regression (SVMR) chemometric models across different spectral resolutions and particle size fractions, and (iv) the quantification of sub-catchment spatial sediment source contributions using chemometric models across different particle size fractions. DRIFTS analysis was performed on three particle size fractions (<38 μm, 38–63 μm, and 63–125 μm) using 54 sediment samples from three different sub-catchments and 26 target sediment samples from the Andajrood catchment in Iran. Results showed significant effects of particle size fractions on DRIFTS for both sub-catchment sediment sources and target sediment samples. Conservatism tests indicated that DRIFTS behave conservative for the majority of target sediment samples. Spectral pre-processing techniques including SNV + SGD1 and SGD1 effectively discriminated sources across all particle size fractions and spectral resolutions. However, the optimal combination of pre-processing, spectral resolution, and regression models varied between sub-fractions. Validated model estimates revealed that sub-catchment 1 consistently contributed the most sediment across all particle size fractions, followed by sub-catchments 3 and 2. These results highlight the effectiveness of DRIFTS as a rapid, cost-effective, and precise method for discriminating and apportioning sediment sources within spatial sub-catchments.

Supercritical CO2 extraction of valuable lipophilic compounds from pre-fractionated sour cherry pomace and evaluation of their composition and properties

Valorisation of fruit processing by-products and waste is an important task for increasing the sustainability of agro-food sector. In this study, pitted sour cherry pomace was mechanically pre-fractionated into the 6 different particle size (>10, 4−10, 3−4, 1−3, 0.8−1, <0.8 mm) fractions (9.71−16.41 % proteins, 5.68−12.16 % fat, 62.55−78.39 % carbohydrates) and subjected to supercritical fluid extraction with CO2 for the recovery of lipophilic constituents. Extract yield depended on fat content and was from 3.38 % to 8.69 %. Linoleic (38.52−47.11 %) and oleic (21.85−39.03 %) were major fatty acids, while triacylglycerols composed of these acids were major in the extracted oils. The concentrations of tocopherols, carotenoids and phytosterols in the extracts were 116.3−432.0, 1218−2564 and 4294−8449 μg/g. Antioxidant activity values were determined for the extracts and solids of initial dry pomace and its residue after extraction. Folin-Ciocalteu Index (basically similar to total phenolic content, TPC), ABTS•+-scavenging and oxygen radical absorbance (ORAC) values of extracts were 7.86−8.75 mg of gallic acid equivalents/g, 1.72−6.37 and 35.12−95.49 of mg trolox equivalents/g, respectively. It is the first report on comprehensive characterisation of sour cherry pomace fractions extracted by supercritical CO2.

Experimental and theoretical study on the smoldering combustion of size-fractioned forest duff particles

Smoldering combustion process has been suggested as a new method potentially useful in the treatment of biosolids. Natural forest duff (FD) often consists of organic fuel layers with varying particle sizes, yet the influence of the size-fractioned particles on the smoldering combustion dynamics in terms of the heat and mass transfer is not well understood. In this study, the oxidative pyrolysis and smoldering behavior of FD samples with four particle sizes (0 < d1 ≤ 0.425 mm, 0.425 < d2 ≤ 1 mm, 1 < d3 ≤ 2 mm, 2 < d4 ≤ 4 mm) were experimentally and theoretically investigated. Micro-scale thermo-gravimetric (TG) analysis, and a four-step kinetic model incorporating water evaporation, FD pyrolysis, FD oxidation and char oxidation showed that the activation energy of the FD pyrolysis and the ash content are negatively correlated, while the activation energy of the char oxidation increases from 87.26 kJ mol−1 to 119.22 kJ mol−1 with the particle size increasing from d1 to d4. Furthermore, the order of the combustion performance of the FD samples is shown as d1<d2<d4<d3. A series of laboratory-scale smoldering experiments revealed that the peak smoldering temperature increases with the fuel depth while the horizontal spread rate decreases with the fuel depth. Both the peak mass loss rate and the smoldering duration presented a reverse order (d1>d2>d4>d3) of the combustion performance found in the TG tests. A simplified heat transfer analysis qualitatively revealed the beneficial effects of the size-fractioned particles on the smoldering spread rate, while a mass transfer analysis revealed the favorable and adverse influences of the particle size on the kinetic-controlled and diffusion-controlled char oxidation rate, respectively. These findings verify that particle sizes alter the FD physicochemical properties (e.g., specific surface area, bulk density, porosity, permeability, chemical components, and lower calorific value), which in return impact the chemical kinetics, heat and mass transfer process in smoldering combustion. This work provides new insights into the effects of the size-fractioned particles on smoldering combustion, ultimately improving the fundamental understanding for optimizing particle sizes for energy conversion and usage.

Revealing Topsoil Behavior to Compaction from Mining Field Observations

Soils are a finite resource that is under threat, mainly due to human pressure. Therefore, there is an urgent need to produce maps of soil properties, functions and behaviors that can support land management and various stakeholders’ decisions. Compaction is a major threat to soil functions, such as water infiltration and storage, and crops’ root growth. However, there is no general agreement on a universal and easy-to-implement indicator of soil susceptibility to compaction. The proposed indicators of soil compaction require numerous analytical determinations (mainly bulk density measurements) that are cost prohibitive to implement. In this study, we used data collected in numerous in situ topsoil observations during conventional soil survey and compared field observations to usual indicators of soil compactness. We unraveled the relationships between field estimates of soil compactness and measured soil properties. Most of the quantitative indicators proposed by the literature were rather consistent with the ordering of soil compactness classes observed in the field. The best relationship was obtained with an indicator using bulk density and clay (BDr2) to define three classes of rooting limitation. We distinguished six clusters of topsoil behaviors using hierarchical clustering. These clusters exhibited different soil behaviors to compaction that were related to soil properties, such as particle-size fractions, pH, CaCO3 and organic carbon content, cation exchange capacity, and some BDr2 threshold values. We demonstrate and discuss the usefulness of field observations to assess topsoil behavior to compaction. The main novelty of this study is the use of large numbers of qualitative field observations of soil profiles and clustering to identify contrasting behavior. To our knowledge, this approach has almost never been implemented. Overall, analysis of qualitative and quantitative information collected in numerous profiles offers a new way to discriminate some broad categories of soil behavior that could be used to support land management and stakeholders’ decisions.

Two-dimensional real-time dosimetry system using micro-and nano-(C44H38P2)MnCl4 radioluminescence coatings

This study investigates the impact of particle size on the radioluminescence (RL) response of (C44H38P2)MnCl4 coatings, which have been made with five crystal size fractions ranging from ≈200 nm to 75 μm. These coatings underwent testing using a bespoke 2D real time prototype system, comprising a camera affixed to the head of a linear accelerator and oriented towards the flexible RL coatings positioned at the beams' isocentre. Upon irradiation, a consistent RL peak at 525 nm was observed across all particle size fractions, albeit with varying light intensities. Minimum detectable dose-rate values were determined to be 0.05 Gy/min, and even for the coating exhibiting the lowest light intensity (Nano-01), individual pulses could be discerned, yielding a minimum detectable dose of 0.28 mGy. Basic dosimetric tests were conducted to characterize these coatings, evaluating their response with respect to dose-rate, dose, and small field relative responses. Subsequently, the coating demonstrating the most favorable dosimetric properties underwent further analysis to assess its suitability for machine quality assurance (QA). These tests included the standard alternating leaves, chair, and pyramid checks routinely employed for QA purposes.

Risk of Mycotoxin Contamination in Thermophilic Composting of Kitchen and Garden Waste at Large-Scale

Although toxicogenic moulds have been identified in municipal waste and composting facilities, only a few reports exist on the occurrence of mycotoxins in compost. Those reports mostly concern sewage sludge as a substrate, tested only a limited range of mycotoxins, and did not monitor the production of mycotoxins during the composting process. Therefore, this study aimed to investigate whether mycotoxins are produced during composting of selectively collected kitchen and garden waste. The study was carried out at pilot scale (550 L reactor with passive aeration). Kitchen waste (59.0% w/w), garden leaves (28.2%), and wood chips (12.8%) were used as a substrate, which was sampled every five days to determine its basic physicochemical characteristics (temperature, moisture, size-fraction content, loss on ignition) and respirometric activity (AT4). The substrate and leachate samples were also tested for the content of eight mycotoxins by HPLC-MS/MS. To screen the local compost market, commercial organic-compost samples were analysed for mycotoxin contamination. The substrate was successfully stabilized after 45 days (thermophilic peak of 62.6 °C, 40.4% mass reduction, 26.9% loss of organic matter, increase in the share of particles in the smallest size fraction, AT4 of 9.82 g O2/kg). Although the substrate was colonised by moulds at an early stage, only trace amounts of mycotoxins were detected in a few samples. Similarly, little or no mycotoxins were found in the commercial compost. Our results suggest a low risk of mycotoxin contamination in biowaste compost produced under appropriate technological conditions. Future research should focus on screening compost produced at smaller scales (e.g., in agricultural/residential compost piles) and on identifying factors associated with the risk of mycotoxin contamination in compost.

Source and fate of atmospheric iron supplied to the subarctic North Pacific traced by stable iron isotope ratios

The availability of dissolved iron (Fe) limits primary production over some regions of the surface ocean, especially in regions such as the subarctic North Pacific. In this work, we use Fe stable isotope ratios (δ56Fe) in bulk and size-fractionated marine aerosol particles and dissolved Fe of surface seawater in the subarctic North Pacific on Japanese GEOTRACES cruise GP02 (Summer 2017) as a tracer to clarify the relative contribution of combustion and natural Fe in both marine aerosol particles and surface seawater. The bulk aerosols collected in the coastal regions of both East Asia and western North Pacific have total δ56Fe values that are as low as −0.5 ‰ when compared to crustal (+0.1 ‰), with both the water-soluble phase and the fine particles even more fractionated (as low as −1.9 and −2.8 ‰, respectively). The negative correlation between the aerosol δ56Fe signatures and the enrichment factors of Fe and other elements dominated by anthropogenic sources (e.g., lead and cadmium) in these coastal regions indicates the presence of Fe emitted from high-temperature combustion sources, such as coal combustion and metal smelting. In these regions, combustion Fe accounts for 4–13 and 13–45 % of the total and water-soluble aerosol Fe, respectively. The results demonstrate that soluble aerosol Fe sourced from combustion Fe can be equivalent to that sourced from natural dust Fe in these coastal regions. By contrast, the aerosol particles in pelagic regions were near crustal δ56Fe in all particle size fractions, indicating the dominance of natural Fe and little to no combustion Fe. The relationships among the fractional Fe solubility, major ion concentration, Fe species, and δ56Fe indicate that the presence of combustion Fe is the dominant reason for the solubility increase in the coastal regions and that the atmospheric processing of mineral dust during transport is more important in the pelagic regions. The dissolved Fe of the surface seawater at 10 m depth had a consistently higher δ56Fe by up to +1.5 ‰ than that of the simultaneously collected water-soluble aerosol Fe. The pattern of the elevated δ56Fe in the surface seawater corresponds to decreasing Fe concentrations and can be approximated by Rayleigh fractionation; we attribute these elevated surface δ56Fe values to the effect of biological uptake. New Fe fluxes from both the atmosphere and deeper depths are limited at least in summer compared with the biological uptake in the open ocean of the subarctic North Pacific.

Particle size shapes prokaryotic communities and vertical connectivity in the water columns of the slope and central basin of the South China Sea

Sinking of organic matter represents an essential mechanism for sequestration of carbon that is exported from the ocean surface to deeper depths. While recent studies have highlighted the important role of microorganisms in the biological pump, the impact of sinking particles on the vertical connectivity of microbial communities has received limited attention. In this study, we present the microbial profile of sinking particles in the northern slope and the central basin of the marginal South China Sea (SCS) using an in-line size-fractionated water filtration and Illumina high-throughput 16S rRNA amplicon sequencing. We investigate the microbial community composition within organic particles of different size fractions (30, 5, 3, 0.22 μm), and we reveal significant differences in the microbial community structure between these two distinct areas of SCS. The vertical connectivity of microbial communities in the slope and the central basin of SCS shows distinct patterns of microbial dispersal along the water column that occurs via the sinking of organic particles. We find that the microbial communities have different abundances on the different examined particle size fractions and which highlights the role of sinking particles in shaping microbial lifestyles along the water column. Our study underscores the influence of environmental variations on the vertical connectivity of microorganisms and provides additional insights into the marine biological pump under different environmental conditions.

The influence of milling of ribbons on selected granule quality attributes and carvedilol release from roller-compacted hypromellose-based matrix tablets

Roller compaction is gaining importance in the pharmaceutical industry. This study evaluates the impact of ribbon milling conditions on properties of granules and compression mixtures and on drug release from hypromellose-based matrix tablets prepared with two different fillers. In the first part of the study, design of experiments (DoE) was utilized to investigate the effect of filler type (lactose and microcrystalline cellulose (MCC)), mill type (oscillating, conical and hammer mill), milling speed and the size of screen apertures on selected attributes (granule particle size distribution (PSD), porosity and shape), and on the compressibility and compactibility of compression mixtures. The effect of DoE factors and selected attributes on the release of carvedilol at different timepoints of the release profile (t = 1–7 h) was further assessed. The study showed that drug release was affected by filler type, mill type, and various attributes; however, their effect proved to be complex and strongly related to granule PSD. Therefore, this effect was minimized in the second part of the study, in which tablets containing the same amount of different particle size fractions of granules were prepared with different mills and fillers. The drug release profiles confirmed that drug release is mainly related to differences in filler type and granule PSD. However, they indicate that with lactose mill type also affected drug release, possibly due to differences identified in particle shape.

Porous PLGA microparticles prepared with nanosized/micronized sugar particles as porogens

The objective of this study was to explore the use of nanosized/micronized sugar particles as porogens for preparing porous poly(lactide-co-glycolide) (PLGA) microparticles by a solid-in-oil-in-water (S/O/W) solvent evaporation method. Porous PLGA microparticles containing dexamethasone were prepared with different nanosized/micronized sugars (sucrose, trehalose and lactose), types of PLGA, and osmogens (NaCl or sucrose) in the external water phase. The microparticles were characterized for morphology, thermal properties, particle size, surface area, encapsulation efficiency and drug release/swelling during release. The addition of nanosized/micronized sugar particles resulted in porous PLGA microparticles with high encapsulation efficiencies. The porosity of the microparticles was caused both by the influx of water into the polymer droplets and the encapsulation and subsequent dissolution of sugar particles during the manufacturing process. The porosity (pore size) of the microparticles and, as a result, the drug release pattern could be well controlled by the particle size and weight fraction of the sugar particles. Because of a larger inner surface area, nanosized sugar particles were more efficient porogen than micronized sugar particles to obtain porous PLGA microparticles with flexible release patterns.

Impact of melon seed oil cake with different particle sizes on bread quality

Melon seed oil cake (MSOC), as the secondary by-product from melon seed oil pressing process, has high potential nutritional value. The aim of this study was to assess the effect of incorporating MSOC as wheat flour substitute and its particle size on bread quality; three particle size fractions of MSOC (coarse, medium, and fine) and two substitution levels (3 and 6%, w/w) were employed. Functional properties and colour of different particle sizes of MSOC were assessed, and the physical properties of bread made with MSOC were explored and compared to control bread (100% wheat flour). Results showed that bread made with 3% MSOC had relatively satisfactory quality in terms of specific volume (2.64–2.86 mL/g), hardness (14.31–15.04 N) compared to the control bread (specific volume 2.79 mL/g and hardness 13.87 N). Bread made with fine particle size of MSOC (2.64 mL/g and 15.04 N at 3% substitution level; 2.44 mL/g and 16.03 N at 6% substitution level) had lower specific volume and higher hardness values than the bread made with medium (2.80 mL/g and 14.31 N at 3% substitution level; 2.50 mL/g and 15.50 N at 6% substitution level) and coarse (2.86 mL/g and 14.72 N at 3% substitution level; 2.52 mL/g and 15.12 N at 6% substitution level) particle sizes of MSOC. These results indicate that using 3% MSOC with larger particle size could be more suitable for making bread with relatively satisfactory quality. Overall, MSOC could be re-introduced into food chain as ingredient for bread production, which offers possibilities to develop novel sustainable foods. Future work will be conducted on sensory quality and consumer acceptance to provide a desirable quality of bread.Graphical

Assessing eDNA capture method from aquatic environment to optimise recovery of human mt-eDNA

Previous studies have shown that environmental DNA (eDNA) from human sources can be recovered from natural bodies of water, and the generation of DNA profiles from such environmental samples may assist in forensic investigations. However, fundamental knowledge gaps exist around the factors influencing the probability of detecting human eDNA and the design of optimal sampling protocols. One of these is understanding the particle sizes eDNA signals are most strongly associated with and the most appropriate filter size needed for efficiently capturing eDNA particles. This study assessed the amount of mitochondrial eDNA associated with different particle sizes from human blood and skin cells recovered from freshwater samples. Samples (300 mL) were taken from experimental 10 L tanks of freshwater spiked with 50 µL of human blood or skin cells deposited by vigorously rubbing hands together for two minutes in freshwater. Subsamples were collected by passing 250 mL of experimental water sample through six different filter pore sizes (from 0.1 to 8 µm). This process was repeated at four time intervals after spiking over 72 hours to assess if the particle size of the amount of eDNA recovered changes as the eDNA degrades. Using a human-specific quantitative polymerase chain reaction (qPCR) assay targeting the HV1 mitochondrial gene region, the total amount of mitochondrial eDNA associated with different particle size fractions was determined. In the case of human blood, at 0 h, the 0.45 µm filter pore size captured the greatest amount of mitochondrial eDNA, capturing 42 % of the eDNA detected. The pattern then changed after 48 h, with the 5 µm filter pore size capturing the greatest amount of eDNA (67 %), and 81 % of eDNA at 72 h. Notably, a ten-fold dilution proved to be a valuable strategy for enhancing eDNA recovery from the 8 µm filter at all time points, primarily due to the PCR inhibition observed in hemoglobin. For human skin cells, the greatest amounts of eDNA were recovered from the 8 µm filter pore size and were consistent through time (capturing 37 %, 56 %, and 88 % of eDNA at 0 hours, 48 hours, and 72 hours respectively). There is a clear variation in the amount of eDNA recovered between different cell types, and in some forensic scenarios, there is likely to be a mix of cell types present. These results suggest it would be best to use a 5 µm filter pore size to capture human blood and an 8 µm filter pore size to capture human skin cells to maximize DNA recovery from freshwater samples. Depending on the cell type contributing to the eDNA, a combination of different filter pore sizes may be employed to optimize the recovery of human DNA from water samples. This study provides the groundwork for optimizing a strategy for the efficient recovery of human eDNA from aquatic environments, paving the way for its broader application in forensic and environmental sciences.

Impact of HPGR operational pressing force and material moisture on energy consumption and crushing product fineness in high-pressure grinding processes

The paper concerns investigations on potential energy savings and breakage effectiveness, resulting from the application of HPGR device into ore mineral processing circuit. A series of laboratory experiments in HPGR for sulphide copper ore was carried out at four values of pressing force in the press and four levels of moisture of the feed material (according to factorial design 42). Fineness analyses on HPGR products were carried out along with a determination of Bond work indices, specific energy consumption, and throughput for each crushing product. Specific mathematical models for Bond work index, energy consumption, productivity, and breakage intensity measured through the yield of finest particle size fraction and specific comminution ratios in relationship to operational pressing force in HPGR and the feed moisture, were calculated. All models appeared to be highly accurate from the statistical point of view and relationships of both pressing force and the moisture appeared significant. The pressing force has generally demonstrated the highest impact on the investigated effects among all analyzed variables, but it depends on the specific model type.

Corymbia citriodora Girdling Aiming Forest Restoration Intensifies the Production of Labile C, N and P in the Soil

ABSTRACT Understanding the effect of different C. citriodora removal management in a Conservation Unit (CU) aimed at forest restoration on the dynamics of the labile and stable fractions of the SOM and to quantify the stoichiometric relationships of these fractions. Soil samples were collected in four areas in the União Biological Reserve (REBIO), Rio de Janeiro, Brazil, namely: forest (FF); C. citriodora trees submitted to girdling (GR); C. citriodora trees submitted to the practice of clear cutting and subsequent planting of native species (PL); abandoned C. citriodora trees without management practice (EU). In these samples, the total content of carbon (C), nitrogen (N) and phosphorus (P) in the air-dried fine earth (ADFE) were determined; in light-fraction organic matter (LFOM) and in the particle size fractions of SOM. It was observed that the C:N and C:P ratios were higher in the EU area and lower in PL in both ADFE and LFOM samples. In EU, lower levels of C, N and P were observed in the SOM particulate fraction. GR favors the production of less recalcitrant and more labile material when compared to EU. The short time (4 years) of implementation of the system in PL directly affects the low production of LFOM; however, this material has high levels of N and P, favoring the low C:N and C:P ratio. EU intensifies the concentration of nutrients in stable fractions in the soil, which can favor the preservation of the soil structure, mitigating its losses.

Influence of chemical pretreatment on the pozzolanicity of recycled glass microparticles used as a substitute for Portland cement

This research investigated the influence of using chemically treated glass microparticles as a partial replacement for cement in Portland cement pastes and mortars. The microparticles were obtained by grinding glass waste into three different particle size fractions (&lt; 75 µm, &lt; 45 µm, and &lt; 25 µm), treated with calcium hydroxide (CH), and characterized using SEM/EDS and a laser particle size analyzer. Samples prepared with the incorporation of glass were characterized using XRD, TGA/DTG, and SEM/EDS. The pretreatment with calcium hydroxide induced the formation of C-S-H with different morphologies on the surface of the particles, in addition to causing changes in particle size distribution due to the formation of agglomerates. The pastes prepared with treated particles had lower amounts of CH and higher levels of hydrated silicates. However, when indirectly measuring the pozzolanicity of treated particles through the compressive strength of mortars, no significant differences were observed in the strengths of mortars made with treated and untreated particles.

Fine particulate matter as a key factor promoting the spread of antibiotics in river network

The extensive utilization of antibiotics has resulted in their frequent detection, contributing to an increased abundance of antibiotic resistance genes in rivers and posing a significant threat to environmental health. Particulate matter plays a crucial role as the primary carrier of various pollutants in river ecosystem. Its physicochemical properties and processes of sedimentation and re-suspension can influence the migration and transformation of antibiotics, yet the mechanisms of this impact remain unclear. In this study, we investigated the distribution characteristics at the micro-scale of particles in the upstream plain river network of the Taihu basin and the adsorption behaviors of antibiotics in particulate matter. The results revealed that particles were predominantly in the size range of 30 to 150 μm in the river network and highest total antibiotic concentrations in 0 to 10 μm particle size fractions. Adsorption experiments also confirmed that the smaller the suspended particle size, the stronger the adsorption capacity for antibiotics. Spatially, both the average particle size and total antibiotic concentrations were lower downstream than upstream. The distribution mechanism of antibiotic in river network sediments was significantly influenced by frequent resuspension and settling of fine particles with a stronger capacity to adsorb antibiotics under hydrodynamic conditions. This ultimately facilitated the release of antibiotics from sediment into the water, resulting in lower antibiotic concentrations in downstream sediments relative to upstream These findings suggest that fine particles serve as the primary carriers of antibiotics, and their sorting and transport processes can significantly influence the distribution of antibiotics in water-sediment systems. This study enhances our understanding of the migration mechanisms of antibiotics in river networks and will prove beneficial for the development of management strategies aimed at controlling antibiotic dissemination.

Size and Shape Selective Classification of Nanoparticles

As nanoparticle syntheses on a large scale usually yield products with broad size and shape distributions, the properties of nanoparticle-based products need to be tuned after synthesis by narrowing the size and shape distributions or via the removal of undesired fractions. The development of property-selective classification processes requires a universal framework for the quantitative evaluation of multi-dimensional particle fractionation processes. This framework must be applicable to any property and any particle classification process. We extended the well-known one-dimensional methodology commonly used for describing particle size distributions and fractionation processes to the multi-dimensional case to account for the higher complexity of the property distribution and separation functions. In particular, multi-dimensional lognormal distributions are introduced and applied to diameter and length distributions of gold nanorods. The fractionation of nanorods via centrifugation and by orthogonal centrifugal and electric forces is modeled. Moreover, we demonstrate that analytical ultracentrifugation with a multi-wavelength detector (MWL-AUC) is a fast and very accurate method for the measurement of two-dimensional particle size distributions in suspension. The MWL-AUC method is widely applicable to any class of nanoparticles with size-, shape- or composition-dependent optical properties. In addition, we obtained distributions of the lateral diameter and the number of layers of molybdenum disulfide nanosheets via stepwise centrifugation and spectroscopic evaluation of the size fractions.

Occurrence and Fate of Per- and Polyfluoroalkyl Substances (PFAS) in Atmosphere: Size-Dependent Gas-Particle Partitioning, Precipitation Scavenging, and Amplification.

The concerns about the fate of per- and polyfluoroalkyl substances (PFAS) in the atmosphere are continuously growing. In this study, size-fractionated particles, gas, and rainwater samples were simultaneously collected in Shijiazhuang, China, to investigate the multiphase distribution of PFAS in the atmosphere. Perfluoroalkyl carboxylic acids (PFCAs) dominated the total concentration of PFAS in atmospheric media. A strong positive relationship (0.79 < R2 < 0.99) was observed between the concentration of PFCAs and organic matter fraction (fOM) in different particle size fractions, while no such relationship for perfluoroalkyl sulfonic acids (PFSAs) and fOM, suggesting fOM may be an important factor influencing the size-dependent distribution of PFCAs. Temperature played a key role in the gas-particle partitioning of PFAS, while it did not significantly affect their particle-size-dependent distribution. The associative concentration fluctuation of particle and particle-bound PFAS during precipitation suggested that precipitation scavenging was an important mechanism for the removal of PFAS from the atmosphere. Furthermore, temporary increases in atmospheric PFAS concentrations were observed during the precipitation. Fugacity ratios of PFAS in rainwater and gas phase (log fR/fG ranged between 2.0 and 6.6) indicated a strong trend for PFAS to diffuse from the rainwater to the gas phase during the precipitation, which may explain that the concentration of PFAS in the gas phase continued to increase even at the end of the precipitation.