Analysis and calculation of scour critical velocity of suspended particles in a storm sewer.

The suspended particles in storm sewer can be easily washed away and migrated. However, few studies analyzed the scouring state of suspended particles in pipelines, and also, there was a lack of quantitative calculation. This study simulated the scouring process of suspended particles in a storm sewer with different pipe materials, and mathematical models were built for the scour critical velocity. The results showed that with the increase of particle size, density and the roughness of the pipe wall, the scour resistance of suspended particles increased, and the scouring rate decreased; therefore, the corresponding scour critical velocity increased. In accordance with the scouring rates of quartz sand and zeolite at different flow velocities in the storm sewer, the scouring state of the suspended particles could be divided into three types: no scouring, minor scouring, and massive scouring. The scour critical velocity ranges of quartz sand and zeolite with two densities in four kinds of pipes were determined, and mathematical models for the scour critical velocity of suspended particles were established. After verification, the difference rate between the calculated values and measured values was in the range of -10.56% to 6.63%, and the two values had good consistency. PRACTITIONER POINTS: Scour resistance of suspended particles increases with particle size or density. The smaller the roughness of the pipe wall, the higher the scouring rate. Higher flow velocity leads to a higher scouring rate. As scouring rate rises, no scouring, minor or massive scouring occur in sequence. Difference between the calculated and measured values is from -10.56% to 6.63%.

[Changes of lung function and inflammatory factors in rat models of coal workers' pneumoconiosis].

Objective: To observe the changes of lung function and inflammatory factors in rat models of coal workers' pneumoconiosis at different time points. Methods: In June 2021, 96 healthy male SD rats with SPF grade were divided into 1, 3, and 6-month control group and dust staining group (coal dust group, coal silica dust group, quartz group) according to random number table method, with 8 rats in each group. After one week of adaptive feeding, a one-time non-exposed tracheal perfusion method (1 ml/ piece) was used. The dust dyeing group was given 50 g/L coal dust, coal silica mixed dust and quartz dust suspension, respectively, and the control group was given 0.9% normal saline solution. At 1, 3 and 6 months after perfusion, lung function was detected by animal lung function apparatus, then all lung tissues and alveolar lavage fluid were killed, and lung histopathological morphological changes were observed by HE staining, and the contents of interleukin (IL-1ß), IL-18, IL-4 and IL-10 in alveolar lavage fluid were detected by ELISA. One-way analysis of variance was used to compare groups. Two factors (inter-group treatment factor (4 levels) and observation time factor (3 levels) ) were used in the analysis of the effects of inter-group treatment and treatment time on related indicators. Results: HE staining results showed that coal spot appeared in the lung tissue of coal dust group, coal spot and coal silicon nodule appeared in the lung tissue of coal dust group, and silicon nodule appeared in the lung tissue of quartz group. Compared with the control group, the forced vital capacity (FVC) and forced expiratory volume at 0.2 second (FEV(0.2)) of rats in the dust staining group had interaction between the treatment and treatment time (P<0.05). With the increase of dust dyeing time, FVC and FEV(0.2) decreased significantly at 3-6 months of dust dyeing, and the maximum gas volume per minute (MVV) decreased significantly at 1-3 months of dust dyeing (P<0.05). The lowest lung function index was in quartz group, followed by coal-silica group and coal-dust group. There were statistically significant differences in the main effect and interaction effect of the pro-inflammatory factor IL-18 among all groups in treatment and treatment time (IL-18: F=70.79, 45.97, 5.90, P<0.001), and interaction existed. The highest content of inflammatory factors in alveolar lavage fluid of all dust groups was quartz group, followed by coal silica group and coal dust group. There were significant differences in the main effect and interaction effect of anti-inflammatory factors between groups and treatment time (IL-4: F=41.55, 33.01, 5.23, P<0.001, <0.001, <0.001; IL-10: F=7.46, 20.80, 2.91, P=0.002, <0.001, 0.024), and there was interaction. The highest content of anti-inflammatory factor was in quartz group, followed by coal silica group and coal dust group. Conclusion: Lung function decreased and levels of inflammatory fators increased in rat models of coal workers' pneumoconiosis, with the quartz group being the most severely damaged. Lung function is mainly impaired in thrid-six months, and the content of inflammatory factors begins to change in first-thrid months. MVV are the earliest and most obvious in lung function. IL-18 is suitable for monitoring changes in the pro-inflammatory response of coal workers' pneumoconiosis, and IL-10 is suitable for monitoring changes in anti-inflammatory response.

Fate and transport of fragmented and spherical microplastics in saturated gravel and quartz sand.

Microplastics in urban runoff undergo rapid fragmentation and accumulate in the soil, potentially endangering shallow groundwater. To improve the understanding of microplastic transport in groundwater, column experiments were performed to compare the transport behavior of fragmented microplastics (FMPs ∼1-µm diameter) and spherical microplastics (SMPs ∼1-, 10-, and 20-µm diameter) in natural gravel (medium and fine) and quartz sand (coarse and medium). Polystyrene microspheres were physically abraded with glass beads to mimic the rapid fragmentation process. The experiments were conducted at a constant flow rate of 1.50 m day-1 by injecting two pore volumes of SMPs and FMPs. Key findings indicate that SMPs showed higher breakthrough, compared to FMPs in natural gravel, possibly due to size exclusion of the larger SMPs. Interestingly, FMPs exhibited higher breakthrough in quartz sand, likely due to tumbling and their tendency to align with flow paths, while both sizes (larger and smaller relative to FMPs) of SMPs exhibited higher removal in quartz sand. Therefore, an effect due to shape and size was observed.

Comparative study of polystyrene microplastic transport behavior in three different filter media: Quartz sand, zeolite, and anthracite.

Microplastics (MPs) are emerging contaminants that are attracting increasing interest from researchers, and the safety of drinking water is greatly affected by their transportation during filtration. Polystyrene (PS) was selected as a representative MPs, and three filter media (quartz sand, zeolite, and anthracite) commonly found in water plants were used. The retention patterns of PS-MPs by various filter media under various background water quality conditions were methodically investigated with the aid of DLVO theory and colloidal filtration theory. The results show that the different structures and elemental compositions of the three filter media cause them to exhibit different surface roughnesses and surface potentials. A greater surface roughness of the filter media can provide more deposition sites for PS-MPs, and the greater surface roughness of zeolite and anthracite significantly enhances their ability to inhibit the migration of PS-MPs compared with that of quartz sand. However, surface roughness is not the only factor affecting the migration of MPs. The lower absolute value of the surface potential of anthracite causes the DLVO energy between it and PS-MPs to be significantly lower than that between zeolite and PS-MPs, which results in stronger retention of PS-MPs by anthracite, which has a lower surface roughness, than zeolite, which has a higher surface roughness. The transport of PS-MPs in the medium is affected by the combination of the surface roughness of the filter media and the DLVO energy. Under the same operating conditions, the retention efficiencies of the three filter materials for PS-MPs followed the order of quartz sand < zeolite < anthracite. Additionally, the conditions of the solution markedly influenced the transport ability of PS-MPs within the simulated filter column. The transport PS-MPs in the simulated filter column decreased with increasing solution ionic strength and cation valence. Naturally, dissolved organic matter promoted the transfer of PS-MPs in the filter layer, and humic acid had a much stronger facilitating impact than fulvic acid. The study findings might offer helpful insight for improving the ability of filter units ability to retain MPs.

Anti-IgG Doped Melanin Nanoparticles Functionalized Quartz Tuning Fork Immunosensors for Immunoglobulin G Detection: In Vitro and In Silico Study.

The quartz tuning fork (QTF) is a promising instrument for biosensor applications due to its advanced properties such as high sensitivity to physical quantities, cost-effectiveness, frequency stability, and high-quality factor. Nevertheless, the fork's small size and difficulty in modifying the prongs' surfaces limit its wide use in experimental research. Our study presents the development of a QTF immunosensor composed of three active layers: biocompatible natural melanin nanoparticles (MNPs), glutaraldehyde (GLU), and anti-IgG layers, for the detection of immunoglobulin G (IgG). Frequency shifts of QTFs after MNP functionalization, GLU activation, and anti-IgG immobilization were measured with an Asensis QTF F-master device. Using QTF immunosensors that had been modified under optimum conditions, the performance of QTF immunosensors for IgG detection was evaluated. Accordingly, a finite element method (FEM)-based model was produced using the COMSOL Multiphysics software program (COMSOL License No. 2102058) to simulate the effect of deposited layers on the QTF resonance frequency. The experimental results, which demonstrated shifts in frequency with each layer during QTF surface functionalization, corroborated the simulation model predictions. A modelling error of 0.05% was observed for the MNP-functionalized QTF biosensor compared to experimental findings. This study validated a simulation model that demonstrates the advantages of a simulation-based approach to optimize QTF biosensors, thereby reducing the need for extensive laboratory work.

Comparison of TL characteristics of natural quartz and zircon.

The dosimetry of different minerals is carried out to investigate the dose received by the population in case of a nuclear accident. Retrospective dosimetry is a field where there is a continuous search to find new materials. Beach sand minerals, namely quartz and zircon, were exposed to beta and gamma radiation and studied separately. A comparison of the thermoluminescence (TL) output of different peaks of quartz for beta and gamma was studied. Comparison of quartz peaks with the TL output of zircon peaks was carried out. TL output for a constant dose of gamma is always higher compared to the TL output received due to beta.

A New SPQC Biosensor for the Detection of a New Target of Escherichia/Shigella Genera Based on a Novel Method of Synthesizing Long-Range DNA.

The rapid and sensitive detection of Escherichia/Shigella genera is crucial for human disease and health. This study introduces a novel series of piezoelectric quartz crystal (SPQC) sensors for detecting Escherichia/Shigella genera. In this innovative biosensor, we propose a new target and novel method for synthesizing long-range DNA. The method relies on the amplification of two DNA probes, referred to as H and P amplification (HPA), resulting in the products of long-range DNA named Sn. The new target was screened from the 16S rRNA gene and utilized as a biomarker. The SPQC sensor operates as follows: the Capture probe is modified on the electrodes. In the presence of a Displace probe and target, the Capture can form a complex with the Displace probe. The resulting complex hybridizes with Sn, bridging the gap between the electrodes. Finally, silver wires are deposited between the electrodes using Sn as a template. This process results in a sensitive response from the SPQC. The detection limit of the SPQC sensor is 1 CFU/mL, and the detection time is within 2 h. This sensor would be of great benefit for food safety monitoring and clinical diagnosis.

Thin seams and small mines are associated with higher exposures to respirable crystalline silica in US underground coal mines.

OBJECTIVES: Previous radiologic and histopathologic studies suggest respirable crystalline silica (RCS) overexposure has been driving the resurgence of pneumoconiosis among contemporary US coal miners, with a higher prevalence of severe disease in Central Appalachia. We sought to better understand RCS exposure among US underground coal miners. METHODS: We analysed RCS levels, as measured by respirable quartz, from coal mine dust compliance data from 1982 to 2021. RESULTS: We analysed 322 919 respirable quartz samples from 5064 US underground coal mines. Mean mine-level respirable quartz percentage and mass concentrations were consistently higher for Central Appalachian mines than the rest of the USA. Mean mine-level respirable quartz mass concentrations decreased significantly over time, from 0.116 mg/m3 in 1982 to as low as 0.017 mg/m3 for Central Appalachian mines, and from 0.089 mg/m3 in 1983 to 0.015 mg/m3 in 2020 for the rest of the USA. Smaller mine size, location in Central Appalachia, lack of mine safety committee and thinner coal seams were predictive of higher respirable quartz mass concentrations. CONCLUSIONS: These data substantially support the association between RCS overexposure and the resurgence of coal workers' pneumoconiosis in the USA, particularly in smaller mines in Central Appalachia.

Protecting against micropollutants in water storage tanks using in-situ TiO2 coated quartz optical fibers.

Photocatalyst-coated optical fibers (P-OFs) using UV-A LEDs offer a highly promising solution for the degradation of micropollutants within municipal, reuse, industrial or home distribution systems, by integrating P-OFs into water storage tanks. P-OFs have photocatalysts attached to bundles of optical fibers, enabling their direct deployment within tanks. This eliminates the necessity for photocatalyst slurries, which would require additional membrane or separation systems. However, a current limitation of P-OFs is light management, specifically light oversaturation of the coated photocatalysts and short light transmission distances along fibers. This study overcomes this limitation and reveals strategies to improve the light dissipation uniformity along P-OFs, and demonstrates the performance of P-OFs on degrading a model micropollutant, carbamazepine (CBZ). Key tunable variables of fibers and light emission conditions, including photocatalyst coating patchiness (p), minimum light incident angles (θm), radiant flux launched to fibers (Φi), and fiber diameters (D), were modeled to establish their relationships with the light dissipation uniformity in TiO2-coated quartz optical fibers (TiO2-QOFs). We then validated modeling insights by conducting experiments to examine how these variables influence the generation of evanescent waves which are localized energy on fiber surfaces, leading to either photocatalyst activation or the recapture of unused light back into fibers. We observed substantial enhancements in evanescent waves generation by decreasing p and increasing θm, resulting in uniform light dissipation which reduces light oversaturation and improves light transmission distances. Moreover, these optimizations led to a remarkable three-fold improvement in CBZ degradation rates and a 65% reduction in energy consumption. Such improvement substantially reduces the capital and operational cost and enhances practicality of energy-efficient photocatalysis without additional chemical oxidants for micropollutant degradation in water storage tanks.

Characterization of particle exposure during tunnel excavation by tunnel boring machines.

Tunnel boring machines (TBMs) are used to excavate tunnels in a manner where the rock is constantly penetrated with rotating cutter heads. Fine particles of the rock minerals are thereby generated. Workers on and in the vicinity of the TBM are exposed to particulate matter (PM) consisting of bedrock minerals including α-quartz. Exposure to respirable α-quartz remains a concern because of the respiratory diseases associated with this exposure. The particle size distribution of PM and α-quartz is of special importance because of its influence on adverse health effects, monitoring and control strategies as well as accurate quantification of α-quartz concentrations. The major aim of our study was therefore to investigate the particle size distribution of airborne PM and α-quartz generated during tunnel excavation using TBMs in an area dominated by gneiss, a metamorphic type of rock. Sioutas cascade impactors were used to collect personal samples on 3 separate days. The impactor fractionates the dust in 5 size fractions, from 10 µm down to below 0.25 µm. The filters were weighted, and the α-quartz concentrations were quantified using X-ray diffraction (XRD) analysis and the NIOSH 7500 method on the 5 size fractions. Other minerals were determined using Rietveld refinement XRD analysis. The size and elemental composition of individual particles were investigated by scanning electron microscopy. The majority of PM mass was collected on the first 3 stages (aerodynamic diameter = 10 to 0.5 µm) of the Sioutas cascade impactor. No observable differences were found for the size distribution of the collected PM and α-quartz for the 3 sampling days nor the various work tasks. However, the α-quartz proportion varied for the 3 sampling days demonstrating a dependence on geology. The collected α-quartz consisted of more particles with sizes below 1 µm than the calibration material, which most likely affected the accuracy of the measured respirable α-quartz concentrations. This potential systematic error is important to keep in mind when analyzing α-quartz from occupational samples. Knowledge of the particle size distribution is also important for control measures, which should target particle sizes that efficiently capture the respirable α-quartz concentration.

Development of SPQC sensor based on the specific recognition of TAL-effectors for locus-specific detection of 6-methyladenine in DNA.

N6-methyladenosine (6mA) plays a pivotal role in diverse biological processes, including cancer, bacterial toxin secretion, and bacterial drug resistance. However, to date there has not been a selective, sensitive, and simple method for quantitative detection of 6mA at single base resolution. Herein, we present a series piezoelectric quartz crystal (SPQC) sensor based on the specific recognition of transcription-activator-like effectors (TALEs) for locus-specific detection of 6mA. Detection sensitivity is enhanced through the use of a hybridization chain reaction (HCR) in conjunction with silver staining. The limit of detection (LOD) of the sensor was 0.63 pM and can distinguish single base mismatches. We demonstrate the applicability of the sensor platform by quantitating 6mA DNA at a specific site in biological matrix. The SPQC sensor presented herein offers a promising platform for in-depth study of cancer, bacterial toxin secretion, and bacterial drug resistance.

Surface modifications of short quartz fibers and their influence on the physicochemical properties and in vitro cell viability of dental composites.

OBJECTIVE: Although glass fibers are more common, quartz fibers (QFs) are also considered as the ideal reinforcing material in dentistry, due to their superior mechanical strength, high purity, and good photoconductive properties. However, the relatively inert surfaces limit their further applications. Therefore, the aim of this study is to modify the fiber surface properties to improve the interfacial interactions with polymeric resins. METHODS: In this study, we systematically introduced four different surface modification strategies onto short quartz fibers (SQFs) for the preparation of dental composites. Particularly, the acid etching was a facile way to create mechanical interlocking structures. In addition, the silanization process, the sol-gel treatment, and the polymer grafting were further proposed to increase the surface roughness and the reactive sites. The effect of surface modifications on the fiber surface morphological changes, mechanical properties, water stability, and in vitro cell viability of dental composites were investigated. RESULTS: Among all surface-modified SQFs, SQFs-POSS (SQFs modified with methacrylate-POSS) exhibited the roughest surface morphology and highest grafting rates compared with other three materials. Furthermore, all these SQFs were applied as reinforcements to make dimethacrylate-based dental resin composites. Of all fillers, SQFs-POSS demonstrated the best reinforcing effect, providing significantly higher improvements of 55.7 %, 114.3 %, and 164.7 % for flexural strength, flexural modulus, and breaking energy, respectively, over those of SQFs-filled composite. The related reinforcing mechanism was further investigated. The SQFs-POSS-filled composite also exhibited the best water stability performance and in vitro cell viability. SIGNIFICANCE: This work provided valuable insights into the optimization of filler-matrix interaction through fiber surface modifications. Specifically, SQFs-POSS markedly outperformed other formulations in terms of the physicochemical performance and in vitro cytotoxicity, which offers possibilities for developing high-performance dental composites for clinical applications in restorative dentistry.

Microbial induced wettability alteration with implications for Underground Hydrogen Storage.

Characterization of the microbial activity impacts on transport and storage of hydrogen is a crucial aspect of successful Underground Hydrogen Storage (UHS). Microbes can use hydrogen for their metabolism, which can then lead to formation of biofilms. Biofilms can potentially alter the wettability of the system and, consequently, impact the flow dynamics and trapping mechanisms in the reservoir. In this study, we investigate the impact of microbial activity on wettability of the hydrogen/brine/rock system, using the captive-bubble cell experimental approach. Apparent contact angles are measured for bubbles of pure hydrogen in contact with a solid surface inside a cell filled with living brine which contains sulphate reducing microbes. To investigate the impact of surface roughness, two different solid samples are used: a "rough" Bentheimer Sandstone sample and a "smooth" pure Quartz sample. It is found that, in systems where buoyancy and interfacial forces are the main acting forces, the impact of biofilm formation on the apparent contact angle highly depends on the surface roughness. For the "rough" Bentheimer sandstone, the apparent contact angle was unchanged by biofilm formation, while for the smooth pure Quartz sample the apparent contact angle decreased significantly, making the system more water-wet. This decrease in apparent contact angle is in contrast with an earlier study present in the literature where a significant increase in contact angle due to microbial activity was reported. The wettability of the biofilm is mainly determined by the consistency of the Extracellular Polymeric Substances (EPS) which depends on the growth conditions in the system. Therefore, to determine the impact of microbial activity on the wettability during UHS will require accurate replication of the reservoir conditions including surface roughness, chemical composition of the brine, the microbial community, as well as temperature, pressure and pH-value conditions.

Rapid Detection of Broad-Spectrum Pathogenic Bacteria Based on Highly Sensitive Proton Response of the Nucleic Acid Amplification SPQC Platform.

Pathogenic bacteria significantly contribute to elevated morbidity and mortality rates, highlighting the urgent need for early and precise detection. Currently, there is a paucity of effective broad-spectrum methods for detecting pathogenic bacteria. We have developed an innovative proton-responsive series piezoelectric quartz crystal (PR-SPQC) platform for the broad-spectrum identification of pathogenic bacteria. This was achieved by retrieving and aligning sequences from the NCBI GenBank database to identify and validate 16S rRNA oligonucleotide sequences that are signatures of pathogenic bacteria but absent in humans or fungi. The hyperbranched rolling circle amplification, activated exclusively by the screened target, exponentially generates protons that are detected by SPQC through a 2D polyaniline (PANI) film. The PR-SPQC platform demonstrates broad-spectrum capabilities in detecting pathogenic bacteria, with a detection limit of 2 CFU/mL within 90 min. Clinical testing of blood samples yielded satisfactory results. With its advantages in miniaturization, cost efficiency, and suitability for point-of-care testing, PR-SPQC has the potential to be extensively used for the rapid identification of diverse pathogenic bacteria within clinical practice and public health sectors.

[Australia's engineered stone ban. A sound decision]. / La prohibición de los aglomerados de cuarzo en Australia, una decisión modélica.

Australia se convirtió en diciembre de 2023 en el primer país en prohibir el uso de los aglomerados de cuarzo. El consumo de estos materiales sintéticos, que contienen más del 80% de sílice cristalina y que desde los años 90 se han empleado para la fabricación de encimeras de cocina y baños, ha contribuido al resurgimiento en numerosos países de formas aceleradas de silicosis y a una notable incidencia de enfermedades sistémicas. El objeto de este trabajo es analizar los fundamentos que sustentan la decisión australiana. Dichos fundamentos están principalmente recogidos en el informe elaborado en 2023 por la agencia gubernamental Safe Work Australia (SWA), que recomendó la prohibición del producto. SWA llevó a cabo una consulta pública entre todos los actores sociales y científicos interesados en el problema. El informe de SWA señaló la ausencia de evidencia científica sobre un umbral de sílice toxicológicamente seguro cuestionando la estrategia de los fabricantes del material de presentar como productos seguros a los aglomerados con menos del 40% de contenido de sílice. La recomendación de SWA tomó en consideración la evaluación del nivel de cumplimiento de las estrictas medidas de prevención implementadas entre 2019 y 2023, constatando que el incumplimiento siguió siendo generalizado en el sector. Además se realizó un análisis coste-beneficio para valorar el número de casos de silicosis que sería necesario evitar para "compensar" los costes económicos asociados a cada opción de prohibición. Para ello empleó el Valor Estadístico de la Vida (VEV) actualizado en 2023 en Australia y estimó en 4,9 millones de dólares australianos cada vida salvada y silicosis evitada. En nuestra opinión, la prohibición australiana es modélica por la forma en que se ha gestado la decisión, por su sólida fundamentación científica y socio-laboral, y por la aplicación del principio de precaución.

Adsorption-desorption of 241Am(â ¢) on montmorillonite colloids and quartz sand: Effects of pH, ionic strength, colloid concentration and grain size.

Clay colloids in the subsurface environment have a strong adsorption capacity for radionuclides, and the mobile colloids will carry the nuclides for migration, which would promote the movability of radionuclides in the groundwater environment and pose a threat to the ecosphere. The investigations of the adsorption/desorption behaviors of radionuclides in colloids and porous media are significant for the evaluation of the geological disposal of radioactive wastes. To illustrate the adsorption/desorption behaviors of 241Am(Ⅲ) in Na-montmorillonite colloid and/or quartz sand systems at different pH (5, 7 and 9), ionic strengths (0, 0.1 and 5 mM), colloid concentrations (300 and 900 mg/L), nuclide concentrations (500, 800, 1100 and 1400 Bq/mL) and grain sizes (40 and 60 mesh), a series of batch sorption-desorption experiments were conducted. Combining the analysis of the physical and chemical properties of Na-montmorillonite with the Freundlich model, the influencing mechanism of different controlling factors is discussed. The experimental results show that the adsorption/desorption behaviors of 241Am(Ⅲ) in Na-montmorillonite colloid and/or quartz sand strongly are influenced by the pH value and ionic strength of a solution, the colloid concentration as well as quartz sand grain size. The adsorption and desorption isotherms within all the experimental conditions could be well-fitted by the Freundlich model and the correlation coefficients (R2) are bigger than 0.9. With the increase in pH, the adsorption partition coefficient (Kd) at 241Am(Ⅲ)-Na-montmorillonite colloid two-phase system and 241Am(Ⅲ)-Na-montmorillonite colloid-quartz sand three-phase system presents a trend which increases firstly followed by decreasing, due to the changes in the morphology of Am with pH. The Kd of 241Am(Ⅲ) adsorption on montmorillonite colloid and quartz sand decreases with increasing in ionic strength, which is mainly attributed to the competitive adsorption, surface complexation and the reduction of surface zeta potential. Additionally, the Kd increases with increasing colloid concentrations because of the increase in adsorption sites. When the mean grain diameter changes from 0.45 to 0.3 mm, the adsorption variation trends of 241Am(Ⅲ) remain basically unchanged. The research results obtained in this work are meaningful and helpful in understanding the migration behaviors of radionuclides in the underground environment.

Transport and retention of ciprofloxacin with presence of multi-walled carbon nanotubes in the saturated porous media: impacts of ionic strength and cation types.

The environmental fate and risks of ciprofloxacin (CIP) in the subsurface have raised intensive concerns. Herein, the transport behaviors of CIP in both saturated quartz sand and sand/multi-walled carbon nanotubes (MWCNTs) mixtures under different solution ionic strength of the solution and coexisting cation types were investigated. Batch adsorption experiments highlighted growing adsorptive capacity for CIP with the increasing content of MWCNTs in the MWCNTs-quartz sand mixtures (from 0.5% to 1.5%, w/w). Breakthrough curves (BTCs) of CIP in the MWCNTs-quartz sand mixtures were well fitted by the two-site chemical nonequilibrium model (R2 > 0.833). The estimated retardation factors for CIP increased from 9.68 to 282 with growing content of MWCNTs in the sand column, suggesting the presence of MWCNTs significantly inhibited the transport of CIP in saturated porous media. Moreover, the values of retardation factors are negatively correlated with the ionic strength and higher ionic strength could facilitate the transport of CIP in the saturated porous media. Compared with monovalent cations (Na+), the presence of divalent cations (Ca2+) significantly facilitated the transport of CIP in the columns due to the complexation between CIP and Ca2+ as well as deposition of MWCNTs aggregates on the sand surface. Results regarding CIP retention in columns indicated that MWCNTs could enhance the accumulation of CIP in the layers close to the influent of sand columns, while they could hinder upward transport of CIP to the effluent. This study improves our understanding for transport behaviors and environmental risk assessments of CIP in the saturated porous media with MWCNTs.

Respirable dust and crystalline silica concentrations among workers at a brick kiln in Bhaktapur, Nepal.

Exposure to respirable dust and crystalline silica (SiO2) has been linked to chronic obstructive pulmonary disease, silicosis, cancer, heart disease, and other respiratory diseases. Relatively few studies have measured respirable dust and SiO2 concentrations among workers at brick kilns in low- and middle-income countries. The purpose of this study was to measure personal breathing zone (PBZ) respirable dust and SiO2 concentrations among workers at one brick kiln in Bhaktapur, Nepal. A cross-sectional study was conducted among 49 workers in five job categories: administration, fire master, green (unfired) brick hand molder, green brick machine molder, and top loader. PBZ air samples were collected from each worker following Methods 0600 (respirable dust) and 7500 (respirable crystalline SiO2: cristobalite, quartz, tridymite) of the U.S. National Institute for Occupational Safety and Health. Eight-hour time-weighted average (TWA) respirable dust and quartz concentrations were also calculated. SiO2 percentage was measured in one bulk sample each of wet clay, the release agent used by green brick hand molders, and top coat soil at the brick kiln. The geometric mean (GM) sample and TWA respirable dust concentrations were 0.20 (95% confidence interval [CI]: 0.16, 0.27) and 0.12 (95% CI: 0.09, 0.16) mg/m3, respectively. GM sample and TWA quartz concentrations were 15.28 (95% CI: 11.11, 21.02) and 8.60 (95% CI: 5.99, 12.34) µg/m3, respectively. Job category was significantly associated with GM sample and TWA respirable dust and quartz concentrations (all p < 0.0001). Top loaders had the highest GM sample and TWA respirable dust concentrations of 1.49 and 0.99 mg/m3, respectively. Top loaders also had the highest GM sample and TWA quartz concentrations of 173.08 and 114.39 µg/m3, respectively. Quartz percentages in bulk samples were 16%-27%. Interventions including using wet methods to reduce dust generation, administrative controls, personal protective equipment, and education and training should be implemented to reduce brick kiln worker exposures to respirable dust and SiO2.

Preliminary insights on the development of a continuous-flow solar system for the photocatalytic degradation of contaminants of emerging concern in water.

The ubiquity and impact of pharmaceuticals and pesticides, as well as their residues in environmental compartments, particularly in water, have raised human and environmental health concerns. This emphasizes the need of developing sustainable methods for their removal. Solar-driven photocatalytic degradation has emerged as a promising approach for the chemical decontamination of water, sparking intensive scientific research in this field. Advancements in photocatalytic materials have driven the need for solar reactors that efficiently integrate photocatalysts for real-world water treatment. This study reports preliminary results from the development and evaluation of a solar system for TiO2-based photocatalytic degradation of intermittently flowing water contaminated with doxycycline (DXC), sulfamethoxazole (SMX), dexamethasone (DXM), and carbendazim (CBZ). The system consisted of a Fresnel-type UV solar concentrator that focused on the opening and focal point of a parabolic trough concentrator, within which tubular quartz glass reactors were fixed. Concentric springs coated with TiO2, arranged one inside the other, were fixed inside the quartz reactors. The reactors are connected to a raw water tank at the inlet and a check valve at the outlet. Rotating wheels at the collector base enable solar tracking in two axes. The substances (SMX, DXC, and CBZ) were dissolved in dechlorinated tap water at a concentration of 1.0 mg/L, except DXM (0.8 mg/L). The water underwent sequential batch (~ 3 L each, without recirculation) processing with retention times of 15, 30, 60, 90, and 120 min. After 15 min, the degradation rates were as follows: DXC 87%, SMX 35.5%, DXM 32%, and CBZ 31.8%. The system processed 101 L of water daily, simultaneously removing 870, 355, 256, and 318 µg/L of DXC, SMX, DXM, and CBZ, respectively, showcasing its potential for real-world chemical water decontamination application. Further enhancements that enable continuous-flow operation and integrate highly effective adsorbents and photocatalytic materials can significantly enhance system performance.

Tepuazines A-E: Phenazine Glycosides from a Venezuelan Quartz-Rich (Tepui) Cave Soil-Derived Streptomyces virginiae CMB-CA091.

Investigation of the secondary metabolites of Streptomyces virginiae CMB-CA091 isolated from the quartz-rich (tepui) soil of a cave in Venezuela yielded two new dimeric phenazine glycosides, tepuazines A and B (1 and 2); three new monomeric phenazine glycosides, tepuazines C-E (3-5); and a series of known analogues, baraphenazine G (6), phenazinolin D (7), izumiphenazine C (8), 4-methylaminobenzoyl-l-rhamnopyranoside (9), and 2-acetamidophenol (10). Structures were assigned to 1-10 on the basis of detailed spectroscopic analysis and biosynthetic considerations, with 1 and 2 featuring a rare 2-oxabicyclo[3.3.1]nonane-like ring C/D bridge shared with only a handful of known Streptomyces natural products. We propose a plausible convergent biosynthetic relationship linking all known members of this structure class that provides a rationale for the observed ring C/D configuration.