Explore the vast range of titles available.

Mauritania is a fishing country. However, the Mauritanian coast is increasingly exposed to environmental issues mainly due to anthropogenic activities such as the mining, gas, oil, and fishing industries, as well as new agricultural practices that unreasonably use inputs. Environmental monitoring of the Mauritanian coast faces several challenges; thus, improving the fisheries sector begins with enhancing the state of marine ecosystems and implementing environmental monitoring adapted to climatic conditions and local needs. This study aims to evaluate the quality of the sediments of the “Baie du Repos” in the town of Nouadhibou, Mauritania, through the study of organic matter and the quantification of trace metallic elements in the Quaternary sediments of the Bay. Six samples deemed representative of this Bay were taken and transported to the laboratory. The physicochemical analysis of these samples shows that the superficial horizons of 30 cm depth have overall organic matter contents higher than the average threshold value proposed by the literature for 4 out of 6 of the points studied. The contents recorded for the different metallic trace elements indicate that point 1 is the most exposed to contamination, with the highest concentrations of cadmium, lead, copper, iron, and zinc. The ACP (Principal Component Analysis) showed that the metallic trace elements Pb, Cu, Fe, Cd, and Zn are closely related and evolve positively in the same direction. Additionally, it was found that the points studied are divided into three groups: Group 1 contains only point 1, which is the most exposed to contamination by these toxic elements (Pb, Cu, Zn, Fe, and Cd). Group 2 contains points 3, 5, and 6, which are moderately contaminated by metallic elements with a significant dominance of organic matter (OM). Finally, Group 3 is the least contaminated, with a very high content of organic matter (OM).

The concentrations of particulates and metallic elements that were bound to total suspended particulates in ambient air at Long Cyuan Elementary School (LCYES), Lung Ching Elementary School (LCHES) and Long Shan Primary School (LSPS) sampling sites in the Longjing area were measured. Significant difference tests were conducted at LSPS, LCYES and LCHES sites. Finally, carcinogenic and non-carcinogenic risk values for LSPS, LCYES and LCHES sites in the Longjing district were evaluated. The results show that the most average particulate and metallic element concentrations were highest in October, November, January, February, March, April, August, and September The average particulate and metallic element concentrations at LCHES were higher than at the other sampling sites. The Concentration Scatter Diagrams reveal the absence of significant variation among the LSPS, LCYES and LCHES sampling sites in the Longjing district. Therefore, these sampling sites are inferred to have similar emission sources. The children and adults inhalation carcinogenic risks which referenced US EPA method were all within acceptable ranges. Non-carcinogenic risks revealed that all metallic elements considered herein were harmless to human health.

The theory of grain boundary (the interface between crystallites, GB) structure has a long history 1 and the concept of GBs undergoing phase transformations was proposed 50 years ago 2 , 3 . The underlying assumption was that multiple stable and metastable states exist for different GB orientations 4 – 6 . The terminology ‘complexion’ was recently proposed to distinguish between interfacial states that differ in any equilibrium thermodynamic property 7 . Different types of complexion and transitions between complexions have been characterized, mostly in binary or multicomponent systems 8 – 19 . Simulations have provided insight into the phase behaviour of interfaces and shown that GB transitions can occur in many material systems 20 – 24 . However, the direct experimental observation and transformation kinetics of GBs in an elemental metal have remained elusive. Here we demonstrate atomic-scale GB phase coexistence and transformations at symmetric and asymmetric [ 11 1 ¯ ] tilt GBs in elemental copper. Atomic-resolution imaging reveals the coexistence of two different structures at Σ19b GBs (where Σ19 is the density of coincident sites and b is a GB variant), in agreement with evolutionary GB structure search and clustering analysis 21 , 25 , 26 . We also use finite-temperature molecular dynamics simulations to explore the coexistence and transformation kinetics of these GB phases. Our results demonstrate how GB phases can be kinetically trapped, enabling atomic-scale room-temperature observations. Our work paves the way for atomic-scale in situ studies of metallic GB phase transformations, which were previously detected only indirectly 9 , 15 , 27 – 29 , through their influence on abnormal grain growth, non-Arrhenius-type diffusion or liquid metal embrittlement. Atomic-resolution observations combined with simulations show that grain boundaries within elemental copper undergo temperature-induced solid-state phase transformation to different structures; grain boundary phases can also coexist and are kinetically trapped structures.

Hydrothermal dissolved iron, manganese, and aluminium from the southern East Pacific Rise is transported several thousand kilometres westward across the South Pacific Ocean; global hydrothermal dissolved iron input is estimated to be more than four times what was previously thought and modelling suggests it must be physically or chemically stabilized in solution. Trans-Pacific transport of hydrothermal metals Deep-sea hydrothermal vents are an important source of iron, an essential trace element that can limit marine productivity. Recent studies have questioned the long-standing view that most of the iron discharged from such vents is removed from seawater close to its source, and is therefore of limited importance for ocean biogeochemistry. Joseph Resing et al . report on the lateral transport of hydrothermal dissolved iron and other trace metals from the southern East Pacific Rise more than 4,000 km across the South Pacific Ocean. Using data from samples collected from 35 hydrographic stations between Manta, Ecuador and Papeete, Tahiti, the authors estimate an input of global hydrothermal dissolved iron to the ocean at least four times greater than previously reported. With the help of a model study, they suggest that physicochemical stabilization of iron enables hydrothermal activity to significantly affect the carbon cycle by supporting phytoplankton growth in the Southern Ocean. Hydrothermal venting along mid-ocean ridges exerts an important control on the chemical composition of sea water by serving as a major source or sink for a number of trace elements in the ocean 1 , 2 , 3 . Of these, iron has received considerable attention because of its role as an essential and often limiting nutrient for primary production in regions of the ocean that are of critical importance for the global carbon cycle 4 . It has been thought that most of the dissolved iron discharged by hydrothermal vents is lost from solution close to ridge-axis sources 2 , 5 and is thus of limited importance for ocean biogeochemistry 6 . This long-standing view is challenged by recent studies which suggest that stabilization of hydrothermal dissolved iron may facilitate its long-range oceanic transport 7 , 8 , 9 , 10 . Such transport has been subsequently inferred from spatially limited oceanographic observations 11 , 12 , 13 . Here we report data from the US GEOTRACES Eastern Pacific Zonal Transect (EPZT) that demonstrate lateral transport of hydrothermal dissolved iron, manganese, and aluminium from the southern East Pacific Rise (SEPR) several thousand kilometres westward across the South Pacific Ocean. Dissolved iron exhibits nearly conservative (that is, no loss from solution during transport and mixing) behaviour in this hydrothermal plume, implying a greater longevity in the deep ocean than previously assumed 6 , 14 . Based on our observations, we estimate a global hydrothermal dissolved iron input of three to four gigamoles per year to the ocean interior, which is more than fourfold higher than previous estimates 7 , 11 , 14 . Complementary simulations with a global-scale ocean biogeochemical model suggest that the observed transport of hydrothermal dissolved iron requires some means of physicochemical stabilization and indicate that hydrothermally derived iron sustains a large fraction of Southern Ocean export production.

The synthesis of graphene materials is typically carried out by oxidizing graphite to graphite oxide followed by a reduction process. Numerous methods exist for both the oxidation and reduction steps, which causes unpredictable contamination from metallic impurities into the final material. These impurities are known to have considerable impact on the properties of graphene materials. We synthesized several reduced graphene oxides from extremely pure graphite using several popular oxidation and reduction methods and tracked the concentrations of metallic impurities at each stage of synthesis. We show that different combinations of oxidation and reduction introduce varying types as well as amounts of metallic elements into the graphene materials, and their origin can be traced to impurities within the chemical reagents used during synthesis. These metallic impurities are able to alter the graphene materials’ electrochemical properties significantly and have wide-reaching implications on the potential applications of graphene materials. Significance Graphene is well-poised to revolutionize many industries because of its multitude of exceptional properties. Current bulk synthesis of graphene materials typically starts with the oxidation of graphite to graphite oxide followed by a reduction step. Many different methods exist for both the oxidation and reduction steps, leading to highly variable types and amounts of metallic contaminations that originate from the reagents themselves. These impurities are able to alter the graphene materials’ properties significantly, which impacts the range of potential applications for which these graphene materials are suitable. Thus, proper characterization of metallic contamination is highly important to ensure the suitability of a chosen set of synthetic procedures to the final application of the graphene material.

The growing increase in antibiotic-resistant bacteria has led to the search for new antibacterial agents capable of overcoming the resistance problem. In recent years, nanoparticles (NPs) have been increasingly used to target bacteria as an alternative to antibiotics. The most promising nanomaterials for biomedical applications are metal and metal oxide NPs, due to their intrinsic antibacterial activity. Although NPs show interesting antibacterial properties, the mechanisms underlying their action are still poorly understood, limiting their use in clinical applications. In this review, an overview of the mechanisms underlying the antibacterial activity of metal and metal oxide NPs will be provided, relating their efficacy to: (i) bacterial strain; (ii) higher microbial organizations (biofilm); (iii) and physico-chemical properties of NPs. In addition, bacterial resistance strategies will be also discussed to better evaluate the feasibility of the different treatments adopted in the clinical safety fields. Finally, a wide analysis on recent biomedical applications of metal and metal oxide NPs with antibacterial activity will be provided.

Global municipal solid waste (~2B tons/year) affects sustainability, as landfill and incineration face persistent leachate contamination, demanding effective management to advance water recycling and circular economies. Accelerated investigation of hybrid biocatalytic ozonation systems is imperative to enhance contaminant removal efficiency for stringent discharge compliance. This study investigates the catalytic ozonation effects of γ-Al[sub.2] O[sub.3] -based catalysts loaded with different metals (Cu, Mn, Zn, Y, Ce, Fe, Mg) on the biochemical effluent of landfill leachate. The catalysts were synthesized via a mixed method and subsequently characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD). Pseudo-second-order kinetics revealed active metal loading’s impact on adsorption capacity, with Cu/γ-Al[sub.2] O[sub.3] and Mg/γ-Al[sub.2] O[sub.3] achieving the highest Q[sub.e] (0.85). To elucidate differential degradation performance among the catalysts, the ozone/oxygen gas mixture was introduced at a controlled flow rate. Experimental results demonstrate that the Cu/γ-Al[sub.2] O[sub.3] catalyst, exhibiting optimal comprehensive degradation performance, achieved COD and TOC removal efficiencies of 84.5% and 70.9%, respectively. UV–vis absorbance ratios revealed the following catalytic disparities: Mg/γ-Al[sub.2] O[sub.3] achieved the highest aromatic compound removal efficiency; Ce/γ-Al[sub.2] O[sub.3] excelled in macromolecular organics degradation. EEM-PARAFAC analysis revealed differential fluorophore removal: Cu/γ-Al[sub.2] O[sub.3] exhibited broad efficacy across all five components, while Mg/γ-Al[sub.2] O[sub.3] demonstrated optimal removal of C2 and C4, but showed limited efficacy toward C5. These findings provide important insights into selecting catalysts in practical engineering applications for landfill leachate treatment. This study aims to elucidate catalyst formulation-dependent degradation disparities, guiding water quality-specific catalyst selection to ultimately enhance catalytic ozonation efficiency.

To understand the birth of stars, observations of the clouds in which they form are key; here, interferometric observations are reported of carbon monoxide clouds in the galaxy WLM, which has a metallicity that is 13 per cent of the value of our Sun. CO clouds in a star-forming galaxy The dwarf irregular galaxy Wolf–Lundmark–Melotte (WLM) in the constellation Cetus has a remarkably low metallicity (a low level of elements heavier than helium), just 13% of that of the Sun. That helps to make it a useful model for the study of star formation under conditions close to those of the early Universe. Monica Rubio et al . report interferometric observations of CO clouds in WLM. The clouds are tiny compared to the surrounding atomic and H 2 envelopes, but they have typical densities and column densities for CO clouds in the Milky Way. The normal CO density explains why star clusters forming in dwarf irregulars have similar densities to star clusters in giant spiral galaxies. The low cloud masses suggest that these clusters will also be low mass. Understanding stellar birth requires observations of the clouds in which they form. These clouds are dense and self-gravitating, and in all existing observations they are molecular, with H 2 the dominant species and carbon monoxide (CO) the best available tracer 1 , 2 . When the abundances of carbon and oxygen are low compared with that of hydrogen, and the opacity from dust is also low, as in primeval galaxies and local dwarf irregular galaxies 3 , CO forms slowly and is easily destroyed, so it is difficult for it to accumulate inside dense clouds 4 . Here we report interferometric observations of CO clouds in the local group dwarf irregular galaxy Wolf–Lundmark–Melotte (WLM) 5 , which has a metallicity that is 13 per cent of the solar value 6 , 7 and 50 per cent lower than the previous CO detection threshold. The clouds are tiny compared to the surrounding atomic and H 2 envelopes, but they have typical densities and column densities for CO clouds in the Milky Way. The normal CO density explains why star clusters forming in dwarf irregulars have similar densities to star clusters in giant spiral galaxies. The low cloud masses suggest that these clusters will also be low mass, unless some galaxy-scale compression occurs, such as an impact from a cosmic cloud or other galaxy. If the massive metal-poor globular clusters in the halo of the Milky Way formed in dwarf galaxies, as is commonly believed, then they were probably triggered by such an impact.

Recently, stimuli-responsive supramolecular gels have received significant attention because their properties can be modulated through external stimuli such as heat, light, electricity, magnetic fields, mechanical stress, pH, ions, chemicals and enzymes. Among these gels, stimuli-responsive supramolecular metallogels have shown promising applications in material science because of their fascinating redox, optical, electronic and magnetic properties. In this review, research progress on stimuli-responsive supramolecular metallogels in recent years is systematically summarized. According to external stimulus sources, stimuli-responsive supramolecular metallogels, including chemical, physical and multiple stimuli-responsive metallogels, are discussed separately. Moreover, challenges, suggestions and opportunities regarding the development of novel stimuli-responsive metallogels are presented. We believe the knowledge and inspiration gained from this review will deepen the current understanding of stimuli-responsive smart metallogels and encourage more scientists to provide valuable contributions to this topic in the coming decades.

The rapid evolution of electronic cigarette (e-cigarette) products warrants surveillance of the differences in exposure across device types-modifiable devices (MODs), cartridge (\"pod\")-containing devices (PODs), disposable PODs (d-PODs)-and flavors of the products available on the market. This study aimed to measure and compare metal aerosol concentrations by device type and common flavors. We collected aerosol from 104 MODs, 67 PODs (four brands: JUUL, Bo, Suorin, PHIX), and 23 d-PODs (three brands: ZPOD, Bidi, Stig) via droplet deposition in a series of conical pipette tips. Metals and metalloids [aluminum (Al), arsenic (As), cobalt (Co), chromium (Cr), copper (Cu), iron (Fe), manganese (Mn), nickel (Ni), lead (Pb), antimony (Sb), tin (Sn), and zinc (Zn)] were measured using inductively coupled plasma mass spectrometry (ICP-MS), results were log-transformed for statistical analysis, and concentrations are reported in aerosol units ( ). Of the 12 elements analyzed, concentrations were statistically significantly higher in MOD devices, except for Co and Ni, which were higher in PODs and d-PODs. Of the POD brands analyzed, PHIX had the highest median concentrations among four metals (Al, Ni, Pb, and Sn) compared to the rest of the POD brands. According to POD flavor, seven metals were three to seven orders of magnitude higher in tobacco-flavored aerosol compared to those in mint and mango flavors. Among the d-POD brands, concentrations of four metals (Al, Cu, Ni, and Pb) were higher in the ZPOD brand than in Bidi Stick and Stig devices. According to d-POD flavor, only Cr concentrations were found to be statistically significantly higher in mint than tobacco-flavored d-PODs. We observed wide variability in aerosol metal concentrations within and between the different e-cigarette device types, brands, and flavors. Overall, MOD devices generated aerosols with higher metal concentrations than PODs and d-PODs, and tobacco-flavored aerosols contained the highest metal concentrations. Continued research is needed to evaluate additional factors (i.e., nicotine type) that contribute to metal exposure from new and emerging e-cigarette devices in order to inform policy. https://doi.org/10.1289/EHP11921.