Search

The structure of calcium aluminosilicate glasses (CaO)x(Al2O3)y(SiO2)1−x−y with the near tectosilicate compositions x ≃ 0.19 and 1 − x − y ≃ 0.61 or x ≃ 0.26 and 1 − x − y ≃ 0.49 was investigated by in situ high-pressure neutron diffraction and 27Al nuclear magnetic resonance (NMR) spectroscopy. The results show three distinct pressure regimes for the transformation of the aluminum coordination environment from tetrahedral to octahedral, which map onto the deformations observed in the production of permanently densified materials. The oxygen packing fraction serves as a marker for signaling a change to the coordination number of the network forming motifs. For a wide variety of permanently densified aluminosilicates, the aluminum speciation shares a common dependence on the reduced density ρ′ = ρ/ρ0, where ρ is the density and ρ0 is its value for the uncompressed material. The observed increase in the Al–O coordination number with ρ′ originates primarily from the formation of six-coordinated aluminum Al(VI) species, the fraction of which increases rapidly beyond a threshold ρ thr ′ ∼ 1.1. The findings are combined to produce a self-consistent model for pressure-induced structural change. Provided the glass network is depolymerized, one-coordinated non-bridging oxygen atoms are consumed to produce two-coordinated bridging oxygen atoms, thus increasing the network connectivity in accordance with the results from 17O NMR experiments. Otherwise, three-coordinated oxygen atoms or triclusters appear, and their fraction is quantified by reference to the mean coordination number of the silicon plus aluminum species. The impact of treating Al(VI) as a network modifier is discussed. [ABSTRACT FROM AUTHOR]

The chemical composition of incense-generated organic aerosol in residential indoor air has received limited attention in Western literature. In this study, we conducted incense burning experiments in a single-family California residence during vacancy. We report the chemical composition of organic fine particulate matter (PM2.5), associated emission factors (EFs), and gas-particle phase partitioning for indoor semivolatile organic compounds (SVOCs). Speciated organic PM2.5 measurements were made using two-dimensional gas chromatography coupled with high-resolution time-of-flight mass spectrometry (GC×GC-HR-ToF-MS) and semivolatile thermal desorption aerosol gas chromatography (SV-TAG). Organic PM2.5 EFs ranged from 7 to 31 mg g-1 for burned incense and were largely comprised of polar and oxygenated species, with high abundance of biomass-burning tracers such as levoglucosan. Differences in PM2.5 EFs and chemical profiles were observed in relation to the type of incense burned. Nine indoor SVOCs considered to originate from sources other than incense combustion were enhanced during incense events. Time-resolved concentrations of these SVOCs correlated well with PM2.5 mass (R 2 > 0.75), suggesting that low-volatility SVOCs such as bis(2-ethylhexyl)phthalate and butyl benzyl phthalate partitioned to incense-generated PM2.5. Both direct emissions and enhanced partitioning of low-volatility indoor SVOCs to incense-generated PM2.5 can influence inhalation exposures during and after indoor incense use.

Heavy metals are extensively discharged through various anthropogenic activities, resulting in an environmental risk on a global scale. In this case, microorganisms can survive in an extreme heavy metal-contaminated environment via detoxification or resistance, playing a pivotal role in the speciation, bioavailability, and mobility of heavy metals. Therefore, studies on the mechanism for the microbial transformation of heavy metals are of great importance and can provide guidance for heavy metal bioremediation. Current research studies on the microbial transformation of heavy metals mainly focus on the single oxidation, reduction and methylation pathways. However, complex microbial transformation processes and corresponding bioremediation strategies have never been clarified, which may involve the inherent physicochemical properties of heavy metals. To uncover the underlying mechanism, we reclassified heavy metals into three categories based on their biological transformation pathways, namely, metals that can be chelated, reduced or oxidized, and methylated. Firstly, we comprehensively characterized the difference in transmembrane pathways between heavy metal cations and anions. Further, biotransformation based on chelation by low-molecular-weight organic complexes is thoroughly discussed. Moreover, the progress and knowledge gaps in the microbial redox and (de)methylation mechanisms are discussed to establish a connection linking theoretical advancements with solutions to the heavy metal contamination problem. Finally, several efficient bioremediation strategies for heavy metals and the limitations of bioremediation are proposed. This review presents a solid contribution to the design of efficient microbial remediation strategies applied in the real environment. [ABSTRACT FROM AUTHOR]

Nitrogen (N) plays an important role in plant growth and developmental metabolic processes, research on nitrogen speciation regulating Cd accumulation in duckweed is still limited. In this study, the effects of three nitrogen sources (NH4Cl, Ca(NO3)2 and NH4NO3) on the growth, Cd accumulation, and photosynthetic parameters of Landoltia punctata (L.punctata) were analyzed. The results showed that Cd enrichment in L. punctata was significantly reduced (p < 0.05) with different nitrogen treatments compared to the control (CK). Ammonium nitrogen (NH4–N) is more conducive to the accumulation of Cd in L. punctata than nitrate nitrogen (NO3–N). The sum of the cell wall components and soluble components of Cd in the NH4–N treatment group was greater than that in the NO3–N treatment group. The proportion of FNaCl extracts in the NH4–N treatment group was greater than in the NO3–N treatment group. NO3–N led to a greater reduction in photosynthetic pigment content than NH4–N. Overall, applying different forms of nitrogen can alleviate Cd toxicity in L. punctata, and the detoxification effect of the NH4–N treatment is stronger than that of NO3–N treatment. This study will provide theoretical and practical support for the application of duckweed in Cd phytoremediation even in eutrophic aquatic environments. NOVELTY STATEMENT: Cd pollution has become a major global public environmental issue. Duckweed is an ideal species to restore Cd-polluted waters due to its fast growth, easy harvesting and hyperaccumulation Cd. Currently, no definite conclusion has been given on the detoxification effect of nitrogen morphology regulating the accumulation of Cd in plant. In this study, the influence of different nitrogen forms on Cd-induced toxicity in Landoltia punctata were revealed through the changes in biomass, Cd subcellular distribution, Cd chemical morphology and photosynthetic pigment. These findings can provide a new way of analyzing the mechanism of Cd enrichment in plants, and also provide theoretical and technical support for the remediation of Cd pollution by using duckweed resources. The Cd-accumulation duckweed can be pyrolyzed to produce biochar, which can not only control the second pollution by decomposed plant bodies but also realizes the efficient use of waste. HIGHLIGHTS: Nitrogen reduced the Cd accumulation in Landoltia punctata due to increased plant biomass. Nitrogen can alter the subcellular distribution and chemical forms of Cd in Landoltia punctata. NH4-N enhanced Cd tolerance of duckweed compared to NO3-N. Lower mobilization of Cd and cell wall combination are the main detoxification strategies for NH4-N supply. [ABSTRACT FROM AUTHOR]

Numerous studies rely on long-term PM2.5 speciation data from the EPA's Chemical Speciation Network (CSN), for example, to estimate health impacts or investigate the sources and transport of PM2.5 pollution. These studies rely on consistent, long-term time series measurements of PM2.5 species to draw conclusions about PM2.5 emissions sources and their health impacts. However, changes in contractors and associated methodological changes in 2015 and 2018 led to disruptions in the consistency of the CSN data, specifically, concentration discontinuities in the CSN time series for ions and elemental carbon (EC) from November 2015 to September 2018 and from October 2018 onward, respectively. To address the impact of these changes on downstream air quality and health analyses, this study developed correction factors by comparing collocated CSN measurements to measurements from the Interagency Monitoring of Protected Visual Environment (IMPROVE) network, which used consistent instrumentation and contractors throughout the study period. These correction factors reduced the discontinuities in the ions and EC concentration time series data, which could be critical for time series source apportionment receptor modeling, air pollution policy and accountability investigations, and health effect studies. Copyright © 2024 American Association for Aerosol Research [ABSTRACT FROM AUTHOR]

A simple and sensitive magnetic solid phase extraction (MSPE) method was developed for the separation-preconcentration and speciation of Cr in water samples. The system is based on the adsorption of Cr (VI)-ammonium pyrrolidinedithiocarbamate (APDC) complex on the activated charcoal@MoSe2@Fe3O4 composite. Total chromium has also been determined after the conversion of Cr (III) to Cr (VI) by oxidation with KMnO4. Cr (III) was determined as the difference between the total content of the Cr and Cr (VI). For quantitative recoveries, the effects of solution pH, adsorbent amount, volume of the sample, ligand volume, eluent type, and volume and effect of foreign ions were investigated. The limit of detection and limit of quantification for Cr was 0.36 ng mL−1 and 1.19 ng mL−1, respectively. The procedure was applied for the determination and speciation of chromium in water samples. [ABSTRACT FROM AUTHOR]

The biological removal of a mixture of soil contaminants, namely, hydrocarbons, is not equally efficient for each compound. Some pollutants can be metabolized by the microbial consortium but also generated again as by-products from the removal of others. At the end of the runs, notwithstanding the high integral removal, single compounds can still be present with a relevant concentration. This paper presents the results achieved in a study of the aerobic degradation of diesel oil in three mesocosms carried out for several months with the same operative conditions. They differed in biological management: Natural Attenuation (NA), Biostimulated without inoculation (BS), and Biostimulated with Inoculation (BS + IN). At the end of the runs, the pollution removal was calculated by measuring the residual diesel oil, both as an average in the total amount of soil and only at the bottom of each column. The overall removal was around 2%, 66%, and 72% for NA, BS and BS + IN, reduced to 0%, 48%, and 47%, respectively, if measured only at the bottom. For the biostimulated mesocosms, the speciation of the hydrocarbons was carried out to assess their concentration. The findings evidence the need to delve deeper into this issue and assess the speciation of contaminants. [ABSTRACT FROM AUTHOR]

Contaminated playground soils can expose players to harmful pollutants, increasing the risk of respiratory, skin, and gastrointestinal issues and potentially impacting long-term health and development. This study investigated the chemical forms and the human health risks associated with potentially toxic elements (PTEs) found in playground soil samples from Khagra, a historic town known for its bell metal industry, located in the Murshidabad district of eastern India. Sequential extraction techniques were employed to analyze the distribution of PTEs such as As, Cd, Co, Cu, Mn, Pb, Ni, Sn, and Zn among different fractions: exchangeable (F1), bound to carbonate phase (F2), bound to iron and manganese oxides (F3), bound to organic matter (F4), and residual (F5). The playground soil showed the highest contamination with Sn, with an IPOLL value of 3.14, indicating moderate to heavy contamination, while Cd, Cu, Mn, Pb, and Zn exhibit moderate contamination. The mean concentration of PTEs in all fractions (F1–F5) follows the order: Fe > Zn > Cu > Mn > Pb > Sn > Ni > Co > As > Cd. The maximum affinity of PTEs and their percentages are as follows: Fe (F5, 80.6%), As (F5, 55.31%), Cd (F5, 48.8), Co (F5, 64.9%), Mn (F3, 44%), Ni (F5, 53.2%), Pb (F3, 44.7%), Zn (F3, −43.19%), Sn (F3, 55%), Cu (F5 −42.18). As, Cd, Co, Cu, Fe, and Ni have a high affinity for F5, indicating geogenic source, while Mn, Pb, Sn, and Zn have a high affinity for F3, indicating anthropogenic source. Fe–Mn oxide partition was dominant for nearly all PTEs due to elevated sorption of cations onto Fe–Mn oxides at high pH. The risk assessment code for Cd, Cu, Mn, Ni, Sn, and Zn in playground soil is categorized under moderate risk, below 30%, while other elements showed no risk. Also, mobility factors were calculated for each PTEs, suggesting the degree of mobility that PTEs can easily migrate and be taken up, absorbed, or adsorbed by the human body. The mobility factor in playground soil was higher for Sn (59.89%) followed by Mn (54.24%) > Pb (52.91%) > Zn (52.01%) > Cd (39.49%) > Ni (33.20%) > As (30.39%) > Co (26.56%) > Cu (21.24%) > Fe (11.20%). Risk hazard quotients for children and adults were found to follow the order: Pb (0.263; 0.040), Cu (0.098; 0.015) > As(0.056; 0.008) > Mn (0.045; 0.009) > Zn(0.36; 0.05) > Cd(0.006; 0.001) > Ni (0.004; 0.001) > Co (0.001; 0.0). PTEs detected in the environment result from atmospheric deposition from small-scale metallurgical industries (bell metal and brass), coal and oil combustion, civil works, municipal waste incineration, and fugitive emissions from road dust. The human non-carcinogenic health risk for PTEs from ingestion and dermal contact was higher than that from inhalation. In the context of carcinogenic risk, As shows the highest health risk of 2.51E-05, followed by Cd (1.02E−09) and Co (8.14E−09). This study uniquely assesses the chemical speciation of PTEs in playground soils, revealing their geogenic and anthropogenic sources, and evaluates associated health risks. Policy intervention is vital for monitoring and remediating PTEs in playgrounds to protect children's health. [ABSTRACT FROM AUTHOR]

The conversion of CO2 into formate (HCOO−), a techno‐economically feasible product, can be achieved using earth‐abundant CuxS electrocatalysts, but questions remain regarding how catalyst structure, composition, and reaction environment influence product selectivity. A novel synthesis method based on electrodeposition of Cu foam and its subsequent sulfidation via immersion in sulfur saturated toluene solution resulted in CuxS foams. Catalytic activity studies found that HCOO− selectivity is dependent on electrochemical activation at higher overpotentials. To understand the effects of activation, determine the active forms of the catalysts, and identify the role of sulfur, the electrodes are carefully characterized as well as gaseous and sulfur dissolved in electrolyte. This included study of the effects of intentional addition of solution sulfur species, identification of the sulfur loss, determination of the electrode composition and relating sulfur speciation to observed product selectivity. It is found that residual sulfur stabilizes Cu+ during electrolysis at potentials favoring HCOO− production, in contrast to pristine Cu that undergoes complete reduction and shows poor HCOO− selectivity. Sulfur in both the catalyst and dissolved in electrolyte are of dynamic nature, and surface residues of SO42− species are identified in all activated catalysts which correspond with enhanced HCOO− production. [ABSTRACT FROM AUTHOR]

We present new insights into the study of the UO2+x/U4O9 equilibrium in UO2 as a function of the hyper-stoichiometry (x) by coupling HERFD-XANES at the uranium M4-edge with micro-Raman spectroscopy mapping. XANES allowed the measurement of uranium speciation in the samples, while Raman spectroscopy was used to individually characterize the composition and localization of the different oxide phases. UO2 pellets were oxidized under dry conditions at temperatures above the UO2+x/U4O9 phase transition to reach hyper-stoichiometries in the range of 0.01 = x = 0.1. Combining both techniques, we could determine the proportions of U4O9 and UO2+x. We show that at a low O/U ratio, U4O9 is present as small clusters inside UO2 grains. As the O/U increases, we found evidence of the formation of a network of U4O9 crystallized inside the UO2+x grains. The variation of the UO2+x phase hyperstoichiometry (x) was evaluated as a function of the sample oxidation. [ABSTRACT FROM AUTHOR]

The mobility of arsenic compounds in the soil-plant system and its interaction with biogenic macroelements K, P, Ca, Mg, Si, S, Na in plants under conditions of toxic stress have been studied. This is illustrated by the wheatgrass Elytrigia repens. It has been established that the root system is responsible for protecting the aerial part of wheatgrass from excess arsenic, and it is of great importance for phytostabilisation of arsenic pollution therefore indicating the increased tolerance of this plant. The intensity of As accumulation in plants depends on its speciation in the soil. Antagonism of the main essential elements (K, P) to the accumulation of As in wheatgrass shoots is observed. It can lead to disruption of metabolic processes in plant cells. It has been shown that changes in the K+/Na + values may lead to violation of osmotic processes in the aerial plant organs and contribute to their degradation not only under salt stress but also under the influence of higher concentrations of As in the plants. In areas intensively contaminated with arsenic, a decrease in the K/Na value in the above-ground organs of wheatgrass can be used as a criterion for the degree of phytotoxicity. [ABSTRACT FROM AUTHOR]

Cobalt (Co) is a hazardous element of significant environmental concern, primarily due to its potential leaching toxicity. However, the current assessments of leached Co residues have focused solely on the total cobalt concentration, often overlooking the distinct Co species that contribute to its hazardous nature. This study attempts to determine the impact of cobalt speciation on the toxicity of cobalt and the related hazardous characteristics. The objective of this study is to enhance the understanding of how different Co species influence the environmental toxicity of leached residues. Cobalt speciation is studied by a multivariate analysis including ignitability, reactivity, corrosiveness, acute toxicity, leaching toxicity, and toxic substance concentration. The tested concentrations are compared with the identification standards and technical specifications in China. Co species, particularly cobalt oxide, are identified as the main contributors to the toxicity of the leached Co residue. It is also noted that Co occurrence significantly affects the calculation results of cumulative toxicity, thus impacting the hazard characteristics of leached cobalt residue. The findings benefit risk evaluators and decision makers by offering a new approach for managing leached Co residues and providing a scientific foundation for the development of relevant laws and regulations in China. [ABSTRACT FROM AUTHOR]

Heavy metals persist in the sediment and can induce toxicological effects on living organisms. For analysing the risk of heavy metals, geochemical fractionation is beneficial. These geochemical fractions or speciations help to determine the heavy metals availability, mobility, toxicity, enrichment, and various risks. Here, we show how heavy metal contamination of sediment poses risks to both the ecosystem and human beings. We found significant Zn, Co and Cd contamination by analysing the geoaccumulation index. We also observed higher geoaccumulation index values for the pre-monsoon season than the post-monsoon one. Furthermore, pollution load index indicated gradual contamination of heavy metals in the sediments. This study's risk assessment and modified risk assessment codes showed low or no risk, but contamination factors indicated moderate to high risk. Our analysis of the effective range median mean quotient revealed some sampling stations as medium to high-priority sites. Similarly, probable effect level mean quotient designated some sampling stations as medium-low priority sites. We anticipated a moderate to significant mortality effect on the organisms from toxicity unit index values. Potential ecological risk index indicated a very high ecological risk on the Mahananda River. Furthermore, we predicted non-carcinogenic health hazards and carcinogenic health risks in the river's sediment. [ABSTRACT FROM AUTHOR]

The spent alum sludge was employed for the removal of specific fission products including 137Cs, 85Sr, 152+154Eu, 99Mo, and 99Tc radionuclides from radioactive waste. The physicochemical features of spent alum sludge were investigated. The results illustrated that the uptake percentages were 94.2, 90.5, 87.6, 87.1, and 76.6%, correspondingly, for 99Mo, 152+154Eu, 99Tc, 85Sr, and 137Cs. The kinetic studies illustrated that the adsorption process obeyed Langmuir kinetics which is a combination of first-order and second-order expressions. The findings demonstrated that the spent alum sludge can be applied successfully as a low-cost and effective adsorbent for the treatment of radioactive waste. [ABSTRACT FROM AUTHOR]

A novel method for the speciation and quantification of polysulfide anions and molecular sulfur in lithium polysulfide solutions in organic solvents is reported. The technique is based on hyphenation of highperformance liquid chromatography (HPLC) and inductively coupled plasma mass spectrometry (ICPMS). A sector-field mass-spectrometer was utilized which made it possible to quantify various sulfur compounds without the need for single component standards and conduct the direct detection of the main isotope of sulfur regardless of interferents such as highly abundant 16O2. Key aspects of separation and sample preparation were considered which allowed complete separation of derivatized polysulfide anions. Gradual adjustment of essential parameters and hardware is described. Variation of plasma settings allowed for obtaining chromatograms with desired analyte peak shapes. The optimized method was applied for the quantification of various lithium polysulfide mixtures in organic solvents showing the accessibility of the corresponding polysulfide distributions with this technique. [ABSTRACT FROM AUTHOR]

The toxicity and reactivity of chromium (Cr) depend on its chemical form or oxidation state which directs the significance of chromium speciation. Cr(VI) is a 'Class A' carcinogen whereas Cr(III)) is considered as essential for metabolism. In this work, concentrations of Cr species in different sampling sites of a tannery effluent have been spectroscopically determined. Cr(VI) was determined by UV-visible spectrophotometer through azo dye formation. Total Cr was determined by FAAS while Cr(III) was through subtraction. The Cr(IV) concentration before and after treatment was found in close proximity since the wastewater treatment process was evidently not effective at reducing the level of Cr(IV) in the waste stream (i.e., 3.34 mg/ L versus 3.15 mg/L). The Cr(VI) concentration after treatment (3.15 mg/L) is more than 31 times higher than the permissible limit of WHO (0.1 mg/L). Furthermore, the concentration of Cr(VI) in the downstream of the receiving river (0.59 mg/L) is more than 12 times higher than the upstream (0.046 mg/L) while Cr(III) in the downstream (25.73 mg/L) is more than 50 times higher than the upstream concentration (0.51 mg/L), confirming that the pollution of the river is from the tannery effluent. [ABSTRACT FROM AUTHOR]

The complete characterization of selenium-enriched yeast in terms of selenium species has been the goal of extensive research for the last three decades. This contribution addresses the two outstanding questions: the mass balance of the identified and reported selenium species and the possible presence of inorganic selenium. For this purpose, four procedures have been designed combining, in diverse order, the principal steps of selenium speciation analysis in Se-rich yeast: extraction of the Se-metabolome, derivatization of cysteine and Se-cysteine (SeCys) residues, proteolysis, and definitive Se recovery using SDS extraction, followed by mineralization. The recovery of selenium in each step and its speciation were controlled by ICP MS and by reversed-phase HPLC-ICP MS, respectively. The study, carried out for the SELM-1 reference material, demonstrated the presence of about 10% of inorganic selenium and a serious risk of losses of SeCys during derivatization and proteolysis. As result of our work, we postulate the following values for SELM-1: Se-metabolome fraction (SeMF) 14.8 ± 0.7%; total selenomethionine (SeMet) 66.2 ± 2.7% (including ca. 1.5% SeMet present in the SeMF); total SeCys 12.5 ± 1.5% (including 2% of SeCys present in the Se-MF); total inorganic selenium 9.7 ± 1.7%, accounting for > 99.8% of the selenium. [ABSTRACT FROM AUTHOR]

The oxidation states of dissolved iron (Fe) and sulfur (S) in silicate melts were studied experimentally by heating Hawaiian olivines containing S-bearing melt inclusions (MIs) in a 1 atm gas-mixing furnace. The MIs are closed with respect to S and C, but equilibrate with the oxygen fugacity (ƒO 2) and water fugacity (ƒH 2 O) of the furnace. We also conducted experiments using a S-free synthetic Hawaiian MI composition held on Pt-loops. Experiments were run at 1225 °C for 8–96 hr in H 2 -CO 2 gas mixtures corresponding to ƒO 2 values that varied over seven orders of magnitude and then drop-quenched into water. Time-series experiments show that MI Fe3+/Fe2+ and S6+/S2− ratios reached constant values within ∼24 hr. The H 2 O contents of the Pt-loop glasses and the dehydrated MIs overlap and are proportional to the f H 2 O in the furnace gas. The slope of log 10 (Fe3+/Fe2+) vs. log 10 ƒO 2 is 0.25±0.02(2σ) for the Pt-loop glasses and 0.23±0.01(2σ) for the quenched MIs; the slopes of the two sets of experiments are consistent with equilibrium having been reached via the reaction FeO + ¼ O 2 = FeO 1.5. S-bearing quenched MI glasses have Fe3+/Fe2+ ratios that are systematically low compared to ratios measured in the S-free Pt-loop glasses run at the same T and ƒO 2 ; this may reflect an effect of S on Fe3+/Fe2+, although further experiments are needed to explore this possibility. S6+/S2− ratios in the experimental melt inclusions vary systematically as a function of ƒO 2 , and the measured ratios agree with independent calculations of S oxidation state in basaltic melts. After being held at 1225 °C for 24 or 48 hr, a subset of olivine-hosted MIs were cooled at rates of 1700–40,000 °C/hr and quenched at temperatures between 900 °C and 1150 °C to explore whether Fe and S speciation are modified during cooling. Fe and S speciation in isothermal and cooled MIs held initially at the same ƒO 2 overlap within uncertainty, suggesting that the T dependence of the homogeneous reaction 8Fe3+ + S2− = 8Fe2+ + S6+ is small and/or its kinetics are sluggish relative to cooling rates required to quench basaltic liquids to glasses. The centers of unheated, naturally quenched MIs from Papakōlea, Hawaii with syneruptive cooling rates ranging from ∼50 to 12,000 °C/hr were also measured for Fe and S speciation. MIs that experienced the lowest cooling rates have higher Fe3+/Fe2+ and S6+/S2− ratios relative to rapidly cooled inclusions of comparable size. The increase in Fe3+/Fe2+ is due to olivine crystallization on the inclusion walls during cooling and diffusion of the resulting oxidized boundary layer into MI interiors. Diffusive modification is minimized in MIs that have been rapidly cooled and/or are sufficiently large such that the oxidized boundary layer is restricted to a narrow region adjacent to the inclusion walls. Our experiments and their comparison to naturally quenched MIs show that measurements of Fe3+/Fe2+ and S6+/S2− ratios in quenched basaltic glasses and in the centers of rapidly cooled and/or large MIs are likely to be representative of the redox state in the melt at magmatic temperatures prior to quenching to glass. [ABSTRACT FROM AUTHOR]

A new family of water‐degradable elastic polymers prepared by oxidative crosslinking of the parent polythionolactones shows promise in a broad range of applications, but the compositions of these materials elude conventional analytical methods. Here we use sulfur K‐edge X‐ray absorption spectroscopy to quantify the amounts of thioether, disulfide, sulfone, sulfate ester, and thionoester in each polymer and to rule out the presence of several other functional groups, including sulfonate, thiosulfonate, sulfate, and sulfoxide. We rationalize this speciation as a function of linker flexibility in the context of sulfinyl cycloaddition reactions and propose a mechanism of aggregation for the oxidized polymers. Our results correlate with swelling ratios but not with porosity nor crosslink density measurements, demonstrating the importance of pairing mechanical and chemical techniques when characterizing heterogeneous organic polymers. Finally, we take advantage of the proximity of the gold M4,5‐edges to the sulfur K‐edge to analyze the binding and reactivity of Au(III) with the crosslinked polymers. [ABSTRACT FROM AUTHOR]

Metal contamination in the Arctic region has increased over the years despite its remote and isolated location. Thus, to evaluate the bioavailable fractions of various metals and their effects on sediment-associated biota, the surface sediments from the fjords were analyzed for bulk concentration of metals and their speciation in different fractions. Metals concentrations were higher in the inner fjord region and decreased towards the outer fjord, supported by the terrigenous influence (TI%) calculated. Cr and Pb showed higher excess values attributed to their additional source other than the catchment rocks. So, to assess the metal-related ecological risk, the bulk concentration of metals was compared with Arctic sediment quality guidelines (ASQGs). Cr, Cd, and Pb concentrations were high, indicating potential adverse biological effects in the study. To avoid the risk of overestimation, metal speciation was conducted, showing that overall metal concentrations were higher in the residual fraction; however, higher concentrations of Mn in labile phases pose a moderate risk to the sediment-associated biota. Additionally, the population density of foraminifera in the sediments was calculated to assess the influence of bioavailable metal on benthic foraminifera. It was found that the presence of metals in bioavailable fractions affected the abundance of the foraminifera. However, no morphological abnormalities were observed in the species. [ABSTRACT FROM AUTHOR]

The present paper deals with an analysis of total arsenic concentration using ICP-MS/MS and an analysis of concentration of several arsenic species, arsenite (AsIII), arsenate (AsV), monomethylarsonate (MMA), dimethylarsenite (DMA), and trimethylarsine oxide (TMAO), using HPLC-ICP-MS/MS in the PM10 fraction of airborne urban aerosol. The samples were collected during two campaigns, in the autumn of 2022 and in the winter of 2023, at three locations within the central European city of Brno, with the aim to evaluate the seasonal and spatial variations in the PM10 composition. The results confirmed only the seasonal variability in the content of the methylated arsenic species in PM10 influenced by biomethylation processes. To gain better understanding of the possible arsenic origin, a supplementary analysis of the total arsenic concentrations was performed in samples of different size fractions of particulate matter collected using ELPI +. Local emissions, including industrial activities and heating during the winter season, were suggested as the most likely predominant source contributing to the total As content in PM10. [ABSTRACT FROM AUTHOR]

Metals such as Zn and Cu present in sewage sludge applied to agricultural land can accumulate in soils and potentially mobilise into crops. Sequential extractions and X-ray absorption spectroscopy results are presented that show the speciation changes of Cu and Zn sorbed to anaerobic digestion sludge after mixing with soils over three consecutive 6-week cropping cycles, with and without spring barley (Hordeum vulgare). Cu and Zn in digested sewage sludge are primarily in metal sulphide phases formed during anaerobic digestion. When Cu and Zn spiked sludge was mixed with the soil, about 40% of Cu(I)-S phases and all Zn(II)-S phases in the amended sludge were converted to other phases (mainly Cu(I)-O and outer sphere Zn(II)-O phases). Further transformations occurred over time, and with crop growth. After 18 weeks of crop growth, about 60% of Cu added as Cu(I)-S phases was converted to other phases, with an increase in organo-Cu(II) phases. As a result, Cu and Zn extractability in the sludge-amended soil decreased with time and crop growth. Over 18 weeks, the proportions of Cu and Zn in the exchangeable fraction decreased from 36% and 70%, respectively, in freshly amended soil, to 28% and 59% without crop growth, and to 24% and 53% with crop growth. Overall, while sewage sludge application to land will probably increase the overall metal concentrations, metal bioavailability tends to reduce over time. Therefore, safety assessments for sludge application in agriculture should be based on both metal concentrations present and their specific binding strength within the amended soil. [ABSTRACT FROM AUTHOR]

The chemical speciation of ternary systems involving Fe(II), 2,6-pyridinedicarboxylic acid (H2Dipi), and various amino acids (glycine, β-alanine, α-alanine, leucine, methionine, lysine, phenylalanine, threonine, serine, proline, valine, and histidine) was investigated in this work. Potentiometric titrations were conducted for each system in aqueous solution at 25 °C using 1 mol dm−3 NaCl solution as the ionic medium. The resulting data were analyzed using the least-squares program LETAGROP. Additionally, the binary system of Fe(II)-2,6-pyridinedicarboxylic acid in aqueous solution at 25 °C with NaCl 1.0 mol dm−3 as the ionic medium was also examined. Species distribution diagrams were generated, and the relative stability parameter Δlog K was calculated. [ABSTRACT FROM AUTHOR]

The distribution equilibria of Am(III) and Cm(III) between the organic phase of bis(2,4,4-trimethylpentyl)dithiophosphonic acid (purified Cyanex301, HA) in xylene and aqueous solutions containing varying concentrations of formic acid or glycolic acid have been investigated aiming at the separation of the two actinides from each other after the groups separation of Am(III)/Cm(III) from Ln(III) ions. The apparent extraction constants for Am(III) and Cm(III) in the Cyanex301-xylene system are determined to be −8.84 and −9.37, respectively, at 0.01 M ionic strength. The specific ion interaction method (SIT) is used to obtain the stability constants of Am(III) and Cm(III) with nitrate and glycolate for calculating the speciation of the ions in extraction at 25°C and I = 0.01 M. The separation of Cm(III) from Am(III) loaded in 0.5 M HA in xylene can be considerably improved by emplying 0.01 to 0.05 M formic acid or glycolic acid as selective stripping reagents favoring complexation with Cm(III). Specifically, with 0.01 M formic acid or glycolic acid in the aqueous phase, the separation factor (SF) for Am(III) over Cm(III) is improved from 3.61 to 5.87 and 5.26, respectively. Hence, both separations of An(III) from Ln(III) and then Am(III) from Cm(III) are achieved by a selective extraction process at first and then a selective stripping process in one simple efficient system using purified Cyanex301 as extractant in organic phase and carboxylic acids as stripping chelates in aqueous. [ABSTRACT FROM AUTHOR]

Isolation of desert springs often leads to the evolution of unique biodiversity. We investigated the taxonomy and evolutionary relationships of members of the Gammarus pecos complex, an assemblage of narrowly endemic amphipod species in the Chihuahuan Desert of the USA. Morphological and molecular phylogenetic analyses, including newly obtained COI sequences from the now-extinct type population of Gammarus desperatus , reveal the presence of two undescribed species and lead to redescription of G. desperatus. Gammarus acerbatus sp. nov. is split from G. desperatus and Gammarus balmorhea sp. nov. is split from G. hyalelloides. Each of these species is endemic to a single spring system. Speciation in the Gammarus pecos complex was likely promoted by the lineage's ties to marine/riverine systems and geological events during the Oligocene/Miocene. The additional diversity discovered within the complex highlights the effects of both habitat and evolutionary history on the processes of speciation at local and regional spatial scales. The entire complex of at least six species is imperilled due to the narrow ranges occupied by each species and human water-use that threatens the existence of their spring habitats. [ABSTRACT FROM AUTHOR]

The Cryogenian (ca. 717–635 Ma) snowball Earth glaciations ended with the precipitation of “cap” carbonate successions with negative carbon isotope (δ13Ccarb) values, which have been explained by the addition of various 13C-depleted carbon sources in the deglacial process. These arguments assumed that marine dissolved inorganic carbon (DIC) was enriched in 13C in the synglacial ocean. However, this assumption has not yet been tested, because the synglacial ocean chemistry is unknown. In this study, we carried out detailed analyses of the petrology, carbonate carbon (δ13Ccarb) and oxygen (δ18Ocarb) isotopes, organic carbon (δ13Corg) isotopes, major and minor elemental compositions (Ca, Mg, Mn, Fe, Sr), and iron speciation (total Fe, highly reactive Fe, pyrite Fe) of the carbonate layers (also called synglacial carbonate layers) from the Nantuo Formation (ca. 650–635 Ma) on the Yangtze block, South China. Petrographic observations indicated that the synglacial carbonate comprises dolomicrite, mud-crystal powder dolomite, lime dolomite, and dolomitic limestone, supporting an authigenic carbonate origin, and thus, it potentially recorded the ocean chemistry during the Marinoan ice age. The synglacial carbonate is characterized by extreme Mn enrichment, low Fe/Mn ratios, and low δ13Ccarb (−7‰) values. High Mn contents and low Fe/Mn ratios imply marine redox conditions favoring Mn2+ accumulation and Fe2+ oxidation, while low δ13Ccarb values might be attributed to CO2 degassing of submarine volcanoes as well as low primary burial during the glaciation. Since the δ13CDIC value of the synglacial ocean was lower than the δ13Ccarb values of most cap carbonates, we infer the addition of 13C-enriched DIC or removal of 12C during cap carbonate precipitation, such as through carbonate weathering or organic carbon burial. These findings provide new insights into the nature of Cryogenian glaciation, the origin of cap carbonates, and the aftermath of global glaciation [ABSTRACT FROM AUTHOR]

Mercury is a neurotoxin that, unlike many localized industrial pollutants, spreads globally through atmospheric transport. Mercury in the atmosphere is operationally partitioned into gaseous elemental mercury (GEM), gaseous oxidized mercury (GOM), and particulate-bound mercury (TPM). Although GOM makes up only a small fraction of Hg in the free troposphere under normal conditions, its role in the dry and wet deposition of mercury makes GOM a significant species for understanding the transport and fate of mercury in the atmosphere. Although instruments for atmospheric mercury speciation are commercially available, significant uncertainty is associated with the current speciation methods, from sample collection to calibration, for GOM measurements. This paper examines the custom-made calibration sources that have been developed for GOM measuring instruments, evaluates the factors influencing the source performance, and synthesizes recommendations for the design and operation of GOM calibration sources in the future. [ABSTRACT FROM AUTHOR]

In this study, surface dust samples were collected within the second ring road of Shenyang City under different land-use types, and the concentration and chemical speciation of metals in different particle sizes under different land-use types were analyzed. Dust samples were separated into four particle size fractions (＜50, 50–100, 100–500, 500–2000 μm), and particles in the range of 100–500 µm were the highest representing one-third of the dust mass. The results revealed that metals were detected in order Zn > Cr > Pb > Cu > Ni > As > Cd in different particle sizes of dust under different land-use types. The relative contribution of individual particle-size fractions for seven metals was different, but the results showed preferential partitioning to small particle-size fractions. The relative contribution of metals in individual particle-size fractions and chemical speciation were significantly affected by the type of land use. Metals concentrated on the smaller particles in the traffic area, and the particles (<50 µm) contained the highest percentage of metals but Cr. The residual fractions (F5) of Ni, Cr, As and Cu overall represented the predominant portion in different particle size of fractions under different land-use types, Zn and Pb were mostly bound to the Fe–Mn oxides-bound fraction (F3), and the exchangeable fraction (F1) accounted for a relatively large proportion of Cd. The results of the risk assessment code (RAC) of Cd indicated that the risk of Zn was medium, and it was high for Cd in the dust of Shenyang City. [ABSTRACT FROM AUTHOR]

We discuss the X-ray absorption spectroscopy (XAS) methods elaborated using the high pressure and high-temperature autoclaves installed at FAME and FAME-UHD beamlines. These methods are based on the in situ acquisition of X-ray transmission and fluorescence spectra of hydrothermal fluids and silicate melts and enable the derivation of both solubility and speciation information about metal complexes. The technological assets of our autoclaves are described across a wide range of experimental conditions spanning from different types of hydrothermal fluids, from liquid-like to vapor-like densities having metal concentrations of <1–10,000 ppm, to magmatic fluid-melt systems at 1000°C. Scientific examples are presented to illustrate the use and the advantages of our spectroscopic 'micro-batch' reactors. Finally, the integration of our autoclave setups on the FAME-UHD crystal analyzer spectrometer and the benefits of this technique are demonstrated. [ABSTRACT FROM AUTHOR]

The growing concern of aquatic heavy metal (HM) pollution is dependent on the toxic nature of its bio-available form. Thus, bio-availability is guided by the HM fractionation in water. This study was therefore conducted to evaluate the spatial impact on physicochemical fractionation of HM (Zn, Mn, Cu, and Fe) in the waters of the Hirakud reservoir in India. Speciation along different pores using a filtration technique was adopted to fractionate the HMs in water samples. The result suggests that the water of the study area is polluted with Cu (0.22–0.35 mg/L), Mn (0.15–0.23 mg/L), and Fe (1.90–3.10 mg/L) that have crossed their permissible limits while Zn (0.17–0.97 mg/L) was within the permissible standard. When studied for physical partitioning, the right dyke was comparatively more polluted than the left dyke. While the water samples were dominated by the dissolved fraction of heavy metals, it was construed that a large proportion of the HMs are in bio-available form. Further, a distinct impact of spatial variation on metal fractionation was also evident in the study with PCA revealing site-specific behaviour. Therefore, it can be concluded that multiple anthropogenic activities lead to the distribution and fractionation of HMs in water. [ABSTRACT FROM AUTHOR]

This study evaluates the sustainability of spreading wastewater or sewage sludge on agricultural land, balancing benefits with contamination risks. Conventional ecological risk indices often fail to address the long-term accumulation of metals in soils. We investigate the feasibility of spreading based on current knowledge of potentially contaminating metals and their behavior in soil. We analyzed the speciation of metals (Ag, Cd, Co, Cr, Cu, Ni, Pb, Ti, Zn) through sequential extraction in sludge, treated wastewater, and soils after 14 years of application of sewage sludge and treated wastewater issued from an Algerian wastewater treatment plant. We introduce a Time to Critical Content Index (TCCI) that calculates the time required to reach critical levels of potentially mobile metals, considering total metal content and speciation. The TCCI takes into account product knowledge, soil characteristics, metal behavior, ecological/toxicological thresholds, and regulations. Applied to our case study, the TCCI indicates that spreading sewage sludge can continue despite metal contents exceeding regulatory ceiling values. The index serves as a precautionary measure, adaptable to evolving knowledge, providing a comprehensive framework for sustainable agricultural practices. [ABSTRACT FROM AUTHOR]

In the latest years, the concentration levels of certain metals and metalloids in the sediments of the Galician Rías have shown an increasing trend (e.g., As, Zn, Cu, Pb, Hg). These areas are also characterized by their richness in nutrients and their great aquaculture or mariculture activity, with the presence of more than 3500 mussel rafts in the Rías Baixas. The inner areas of the Galician Rías are subjected to activities that resuspend the sediment such as high levels of maritime traffic and dredging or cleaning operations. It is likely that a transfer of these elements to the water column happens during the resuspension of sediments caused by natural events or anthropogenic activities. In this study, selected samples of surface sediments of the Ría de Pontevedra (NW Spain) were subjected to a procedure of aerobic oxidation to determine the concentration of some elements (Fe, Mn, Cu, Cr, Pb, Hg, and Zn) released from the sediment to the aqueous phase. The experiment was carried out within 5 days. Measurements of pH and total concentration were taken both in water and sediment samples. Furthermore, speciation of trace elements was carried out in the sediment samples. Trace element concentrations were lower in the sediments during aerobic oxidation, being released to the aqueous phase. From an environmental point of view, Cu was the only trace element released in quantities that may be toxic for the organisms in the area. This problem of sediment oxidation related to dredging activities or natural storm conditions should be considered in environmental impact studies and transferred to stakeholders. [ABSTRACT FROM AUTHOR]

Metal contamination is a crucial environmental issue because of its persistence and toxicity, which can have deleterious effects on aquatic ecosystems. Coastal sediments serve as reservoirs for metals. Aquaculture is an important human activity in coastal areas; however, the actual status of metal distribution in these areas has not been well characterized. We investigated the distribution and geochemical speciation of metals in the sediments of the Japanese aquaculture areas of Shidugawa and Furue Bays. Total metals were generally in the order Zn > Cu > Ni > Cd > Pb and occurred at high levels at the sites in the inner parts and near the fish cages in the sampling areas. Pearson's correlations and principal component analysis results suggested that the metals in these aquaculture areas might originate from several sources, such as fish feces, fish feeds, corrosion of antifouling material residues, and local anthropogenic activities, including fertilizers and manures. Furthermore, metals were mainly in silts and fine sediments, associated with residual speciation, followed by organic fractions, oxides, and high fractions of exchangeable Cd. These results provide important insights into the accumulation of metals in sediments for better managing marine aquaculture in Japan. [ABSTRACT FROM AUTHOR]

Bixa orellana is a plant that has a variety of uses, such as applications in the food and cosmetic industries, as well as culinary uses, and body painting for Indigenous people. Despite its versatility, few studies have explored its inorganic composition, and its sulfur chemical speciation has only been assessed from the point of view of sulfurous amino acids. Here, we report on the inorganic composition of Bixa orellana fruits, pericarps, and seeds obtained using Wavelength Dispersive X-ray Fluorescence (WD-XRF) and sulfur chemical speciation using X-ray Absorption Near-Edge Structure (XANES). Our results show that the seed is a source of potassium, calcium, magnesium, and phosphorous. But also, the pericarp, which is considered waste, contains a high amount of nutrients. From the XANES measurements, the distribution of the oxidation state of the sulfur atom was obtained, and it was shown that although several oxidation states of sulfur are present, oxidized sulfur (sulfate) is the dominant form of sulfur in all samples. [ABSTRACT FROM AUTHOR]

In the marine cryosphere, seasonal sea ice dynamics affect the behavior of gaseous mercury, yet the mechanism remains poorly understood. By carrying out an outdoor sea ice mesocosm study, we examine primarily the abiotic factors influencing mercury dynamics and show distinct behaviors of gaseous mercury across the sea ice‐seawater interface over the full growth‐melt cycle. The distribution of gaseous mercury in sea ice is influenced by entrapment of gaseous mercury from different sources into sea ice of different textures, transport schemes within sea ice, and in situ cryo‐processes that affect mercury speciation. In the growing sea ice sections where solar radiation penetrated, production of gaseous mercury was observed, supporting the occurrence of in‐ice cryo‐photoreduction of divalent mercury. In under‐ice seawater, concentrations of dissolved gaseous mercury decreased gradually during ice growth and increased rapidly to pre‐freezing levels as ice started to melt, suggesting that the atmosphere‐sea ice‐seawater exchange pathway of gaseous mercury could be re‐established through melting first‐year sea ice. Our results from this unique mesocosm study provide new insights on the dynamics of gaseous mercury in and around sea ice that are primarily driven by abiotic processes, assisting model parameterizations for mercury cycling in polar regions. Plain Language Summary: Mercury is a contaminant of health concern that can be readily redistributed globally in the form of gaseous mercury. The air‐sea exchange of gaseous mercury is the primary pathway for mercury transport between the atmosphere and surface oceans. However, such a process is largely modified in polar regions where the presence of sea ice not only physically impedes the direct air‐sea interaction but also induces cryo‐processes that influence mercury speciation. Despite studies on the distribution of gaseous mercury in the Arctic, little is known about the cryo‐processes controlling the dynamics of gaseous mercury in sea ice. In this study, we report temporal evolution of total and gaseous mercury in experimental first‐year sea ice from an outdoor sea ice mesocosm. We show that the distribution and entrapment of gaseous mercury in sea ice depend on ice textures and vary temporally over the growth‐melt cycle. We further show evidence for in‐ice mercury photoreduction that leads to the production of gaseous mercury during the formation of sea ice. Key Points: The dynamics of gaseous mercury in sea ice and seawater, primarily driven by abiotic processes, were studied over a full growth‐melt cycleThe sources, sinks and dynamics of gaseous mercury in sea ice evolve temporally and are associated with ice textures and cryo‐processesNet mercury photoreduction could occur in sea ice where solar radiation penetrates [ABSTRACT FROM AUTHOR]

Evolution of nitrogen under shock compression up to 100 GPa is revisited via molecular dynamics simulations using a machine-learned interatomic potential. The model is shown to be capable of recovering the structure, dynamics, speciation, and kinetics in hot compressed liquid nitrogen predicted by first-principles molecular dynamics, as well as the measured principal shock Hugoniot and double shock experimental data, albeit without shock cooling. Our results indicate that a purely molecular dissociation description of nitrogen chemistry under shock compression provides an incomplete picture and that short oligomers form in non-negligible quantities. This suggests that classical models representing the shock dissociation of nitrogen as a transition to an atomic fluid need to be revised to include reversible polymerization effects. [ABSTRACT FROM AUTHOR]

• SC, Mg/SC and ZVI decreased concentrations of Cd and iAs in rice grain concurrently. • Mg/SC and ZVI simultaneously reduced Cd and iAs concentrations in soil porewater. • ZVI raised DMA concentrations in porewater and rice grain, but SC and Mg/SC didn't. • SC, Mg/SC and ZVI affected Cd/As accumulation through divergent mechanisms. Cadmium (Cd) and arsenic (As) co-contamination has threatened rice production and food safety. It is challenging to mitigate Cd and As contamination in rice simultaneously due to their opposite geochemical behaviors. Mg-loaded biochar with outstanding adsorption capacity for As and Cd was used for the first time to remediate Cd/As contaminated paddy soils. In addition, the effect of zero-valent iron (ZVI) on grain As speciation accumulation in alkaline paddy soils was first investigated. The effect of rice straw biochar (SC), magnesium-loaded rice straw biochar (Mg/SC), and ZVI on concentrations of Cd and As speciation in soil porewater and their accumulation in rice tissues was investigated in a pot experiment. Addition of SC, Mg/SC and ZVI to soil reduced Cd concentrations in rice grain by 46.1%, 90.3% and 100%, and inorganic As (iAs) by 35.4%, 33.1% and 29.1%, respectively, and reduced Cd concentrations in porewater by 74.3%, 96.5% and 96.2%, respectively. Reductions of 51.6% and 87.7% in porewater iAs concentrations were observed with Mg/SC and ZVI amendments, but not with SC. Dimethylarsinic acid (DMA) concentrations in porewater and grain increased by a factor of 4.9 and 3.3, respectively, with ZVI amendment. The three amendments affected grain concentrations of iAs, DMA and Cd mainly by modulating their translocation within plant and the levels of As(III), silicon, dissolved organic carbon, iron or Cd in porewater. All three amendments (SC, Mg/SC and ZVI) have the potential to simultaneously mitigate Cd and iAs accumulation in rice grain, although the pathways are different. [Display omitted] [ABSTRACT FROM AUTHOR]

Reducing the bioavailability of lead (Pb) in soil is the key to alleviating the toxicity of Pb to plants. The present study investigated the effects of phosphorus application on Pb speciation in soil and the oxidative stress of plant to Pb. Maize was planted in 100 mg/kg Pb soil with three fertilizer levels. The phosphate application led to reductions of 25%, 30% and 25% in the activity of total superoxide dismutase (T-SOD) and peroxidase (POD) and the concentration of lipid peroxidation (MDA) in maize leaves, and reduced Pb accumulation in the above- and belowground biomass of maize by 39% and 30%, comparing to the control. The water-soluble, ionic, and carbonate Pb fractions in rhizosphere soil decreased by 38%, 36% and 43%, respectively, and the organic and residual Pb fraction were increased with values of 11.7 ± 0.6 and 18.6 ± 0.4 mg/kg. The soil aluminum-bound (Al–P) and iron-bound phosphate (Fe–P) were highest, with values of 94 ± 8.2 and 230 ± 16.0 mg/kg, indicating that phosphate supplementation increased the soil ionic phosphorus and transformed chemically mobilized P (such as O–P and Ca–P) into bioavailable P. The phosphate supplementation of Pb-contaminated soil could transfer the unstable Pb fraction into the stable Pb fraction by P-induced Pb immobilization, could reduce the bioavailability of Pb and could alleviate the toxicity of heavy metals to plants. [ABSTRACT FROM AUTHOR]

BACKGROUND: Including seaweed in cattle feed has gained increased interest, but it is important to take into account that the concentration of toxic metals, especially arsenic, is high in seaweed. This study investigated the arsenic species in milk from seaweed‐fed cows. RESULTS: Total arsenic in milk of control diets (9.3 ± 1.0 μg As kg−1, n = 4, dry mass) was significantly higher than seaweed‐based diet (high‐seaweed diet: 7.8 ± 0.4 μg As kg−1, P < 0.05, n = 4, dry mass; low‐seaweed diet: 6.2 ± 1.0 μg As kg−1, P < 0.01, n = 4, dry mass). Arsenic speciation showed that the main species present were arsenobetaine (AB) and arsenate (As(V)) (37% and 24% of the total arsenic, respectively). Trace amounts of dimethylarsinic acid (DMA) and arsenocholine (AC) have also been detected in milk. Apart from arsenate being significantly lower (P < 0.001) in milk from seaweed‐fed cows than in milk from the control group, other arsenic species showed no significant differences between groups. CONCLUSION: The lower total arsenic and arsenate in seaweed diet groups indicates a possible competition of uptake between arsenate and phosphate, and the presence of AC indicates that a reduction of AB occurred in the digestive tract. Feeding a seaweed blend (91% Ascophyllum nodosum and 9% Laminaria digitata) does not raise As‐related safety concerns for milk. © 2024 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Investigating the different chemical species of soluble iron in food digests provides more relevant information on the nutritional potential of an iron‐rich food. The objective of this study was to assess the bioaccessibility and speciation of iron from various aqueous extracts of Moringa (Moringa oleifera) leaves. Aqueous extracts were prepared from fresh and dried Moringa leaves using infusion and decoction methods. Spectrophotometric assays were performed to quantify inhibitors and enhancers of iron absorption in the extracts, bioaccessible iron, and its different chemical species. The highest contents of inhibitors (239.43 mg/L for polyphenols and 2.92 mg/L for phytates) and enhancers of iron absorption (1.58 mmol/L for carotenoids and 488.00 mg/L for ascorbic acid) were found in the 5‐minute decoction extract of fresh leaves, and the lowest in all infusion extracts (27.34 mg/L for polyphenols, 0.50 mg/L for phytates, 0.15 mmol/L for carotenoids, and 86.00 mg/L for ascorbic acid). The percentages of bioaccessible iron were higher for decoction extracts (42.57–52.70%) compared to infusion extracts (33.89–36.44%). Ferrous iron was the dominant inorganic species of bioaccessible iron and was more concentrated in the digests of decoction extracts (1.32–4.85 mg/L). The highest content of organic iron (5.33 mg/L) was found in the digest of the 8‐minute decoction extract of dried leaves. Drinking decoction extracts of fresh and dried Moringa leaves could be recommended to alleviate iron deficiency in vulnerable groups of the population living in areas where this plant can grow. [ABSTRACT FROM AUTHOR]

Samarium diiodide (SmI2) is a privileged, single-electron reductant deployed in diverse synthetic settings. However, generalizable methods for catalytic turnover remain elusive because of the well-known challenge associated with cleaving strong SmIII–O bonds. Prior efforts have focused on the use of highly reactive oxophiles to enable catalyst turnover. However, such approaches give rise to complex catalyst speciation and intrinsically limit the synthetic scope. Herein, we leveraged a mild and selective protonolysis strategy to achieve samarium-catalyzed, intermolecular reductive cross-coupling of ketones and acrylates with broad scope. The modularity of our approach allows rational control of selectivity based on solvent, pKa (where Ka is the acid dissociation constant), and the samarium coordination sphere and provides a basis for future developments in catalytic and electrocatalytic lanthanide chemistry. [ABSTRACT FROM AUTHOR]

Knowledge of the geochemistry of selenium (Se) is crucial for understanding its behavior in the environment. While numerous studies have explored selenium geochemistry, there is a notable inadequacy, especially in extreme soil conditions such as saline soils, which are widespread globally. This study focuses on characterizing the geochemistry of selenium in saline soils, with a specific focus on the El Hamadna perimeter in Bas-Cheliff, Algeria. This location was chosen due to its diverse salinity levels and selenium content. Utilizing Phreeqc software, the study examines selenium's chemical speciation. In the arid soils of this region, predicted selenium (IV) concentrations range from 0.19 to 3.05 mg kg–1, and selenium (VI) concentrations range from 0.54 to 5.58 mg kg–1. A significant negative correlation was observed between total selenium and Se(VI) concentrations with pH, whereas Se(IV) showed a positive and significant correlation with pH. No correlation was found between selenium concentrations and the salinity gradient in the studied soils. Non-significant correlations were observed between selenium levels and CaCO3, clay, and organic matter in the soils, suggesting that these soil properties do not influence the distribution of selenium concentrations in the examined soils. Only the pH and the presence of the main form MgSeO3 control the representation of selenium in the soil profile. [ABSTRACT FROM AUTHOR]

Mercury (Hg) is a toxic element which impacts on biological systems and ecosystems. Because the toxicity of Hg species is highly dependent on their concentration levels and chemical forms, the sensitive identification of the chemical forms of Hg—i.e., Hg speciation—is of major significance in providing meaningful information about the sources of Hg exposure. In this study, a microfluidic-based device made of high-clarity poly(methyl methacrylate) (PMMA) was fabricated. Then, titanium dioxide nanoparticles (nano-TiO2s) were attached to the treated channel's interior with the aid of poly(diallyldimethylammonium chloride) (PDADMAC). After coupling the nano-TiO2-coated microfluidic-based photocatalyst-assisted reduction device (the nano-TiO2-coated microfluidic-based PCARD) with high-performance liquid chromatography (HPLC) and inductively coupled plasma mass spectrometry (ICP-MS), a selective and sensitive, hyphenated system for Hg speciation was established. Validation procedures demonstrated that the method could be satisfactorily applied to the determination of mercury ions (Hg2+) and methylmercury ions (CH3Hg+) in both human urine and water samples. Remarkably, the zeta potential measured clearly indicated that the PDADMAC-capped nano-TiO2s with a predominance of positive charges indeed provided a steady force for firm attachment to the negatively charged device channel. The cause of the durability of the nano-TiO2-coated microfluidic-based PCARD was clarified thus. [ABSTRACT FROM AUTHOR]

Copper-catalysed intramolecular Ullman arylation has been frequently used to synthesise benzoxazoles and benzothiazoles. Despite widespread use, investigations into the mechanism and speciation of copper-containing complexes relevant to the catalytic pathway have remained relatively limited. Accordingly, this study aims to elucidate the structural details of potential copper(I) intermediates through the analysis of their solid-state structures using X-ray crystallography, while also investigating the reactivities of these complexes. Five novel copper complexes are reported which are formed prior to the aryl halide activation step and feature distinct aggregation modes based on either Cu4N4O4C4 or Cu4N4S4C4 clusters. [ABSTRACT FROM AUTHOR]

This study investigated the distribution of sedimentary phosphorus (P) species along an area of a rapid current at the southern coast of Zhoushan Island. The objective of this study was to improve the understanding of P cycling in a zone of rapid water cycling. Results showed that the average percentage of each P form to total P (TP) was in the following order: apatite P (Ca-P; 52%) was found in the most abundant, followed by organic P (OP; 16%), exchangeable-P (Ex-P; 14%), detrital P (De-P; 11%), and iron-bound P (Fe-P; 7%). Ca-P showed a trend of an increasing concentration from a location at the west (ZS1 has mean Ca-P = 45.6 mg kg−1) toward the east (ZS2 has mean Ca-P = 82.69 mg kg−1) and south-east (ZS3 has mean Ca-P = 82.17 mg kg−1); De-P also increased from 15.12 mg kg−1 at ZS1 to 22.53 mg kg−1 at ZS2 and 27.45 mg kg−1 at ZS3, but the three bioavailable P species, OP, Ex-P, and Fe-P, decreased from the west toward the east of the coastal area. Results along the cores showed the occurrences of sediment P adsorption and release throughout the time span from the 1930s to the present, with an overall trend of decreasing Ca-P and TP from the bottom to surface sediments. There was a tendency of Ca-P formation at the expense of Ex-P and OP release during transport and organic matter decomposition. The likely impact of climate change in the coastal zone would be an increased temperature resulting in elevated organic matter decomposition and P release. [ABSTRACT FROM AUTHOR]

Improper disposal of municipal solid waste led to the release of heavy metals into the environment through leachate accumulation, causing a range of health and environmental problems. Phycoremediation, using microalgae to remove heavy metals from contaminated water, was investigated as a promising alternative to traditional remediation methods. This study explored the potential of Scenedesmus sp. as a phycoremediation agent for heavy metal removal from landfill leachate. The study was conducted in batch, continuous, and membrane bioreactor (MBR). In the batch system, Scenedesmus sp. was added to the leachate and incubated for 15 days before the biomass was separated from the suspension. In the continuous system, Scenedesmus sp. was cultured in a flow-through system, and the leachate was continuously fed into the system with flow rates measured at 120, 150, and 180 mL/h for 27 days. The MBR system was similar to the continuous system, but it incorporated a membrane filtration step to remove suspended solids from the treated water. The peristaltic pump was calibrated to operate at five different flow rates: 0.24 L/h, 0.30 L/h, 0.36 L/h, 0.42 L/h, and 0.48 L/h for the MBR system and ran for 24 h. The results showed that Scenedesmus sp. was effective in removing heavy metals such as lead (Pb), cobalt (Co), chromium (Cr), nickel (Ni), and zinc (Zn) from landfill leachate in all three systems. The highest removal efficiency was observed for Ni, with a removal of 0.083 mg/L in the MBR and 0.068 mg/L in batch mode. The lowest removal efficiency was observed for Zn, with a removal of 0.032 mg/L in the MBR, 0.027 mg/L in continuous mode, and 0.022 mg/L in batch mode. The findings depicted that the adsorption capacity varied among the studied metal ions, with the highest capacity observed for Ni (II) and the lowest for Zn (II), reflecting differences in metal speciation, surface charge interactions, and affinity for the adsorbent material. These factors influenced the adsorption process and resulted in varying adsorption capacities for different metal ions. The study also evaluated the biomass growth of Scenedesmus sp. and found that it was significantly influenced by the initial metal concentration in the leachate. The results of this study suggest that Scenedesmus sp. can be used as an effective phycoremediation agent for removing heavy metals from landfill leachate. [ABSTRACT FROM AUTHOR]

The most varied ecosystem on Earth has been the subject of study for soil scientists and microbiologists for more than three centuries. Using a wide range of methods, they have characterized the composition, structure, and function of the soil microbial community. However, model systems and isolated organisms continue to be the main sources of our knowledge regarding the soil microbiome and the reciprocal dynamics with metal speciation and bioavailability. On the other hand, metals are vital to life processes and are widely present in agriculture and the environment. This chapter's goal is to highlight the current gaps in metal-microbiome research by reviewing our current understanding of the soil factors that control metal bioavailability and combining it with our understanding of the dynamics of metals and metalloids with microbial communities in soil. In the end, only a complete knowledge of the interactions between soil microbiome and the soil, plant communities that they are associated with, and the molecular mechanisms underlying their biogeochemical function will allow for the restoration of ecosystem function, improved soil health and quality, and any kind of management for microbial metal transformations. [ABSTRACT FROM AUTHOR]

This study explores how climate variables influenced the evolution and diversification of Neurergus newts within the Irano‐Anatolian biodiversity hotspot. We use a dated phylogenetic tree and climatic niche models to analyze their evolutionary history and ecological preferences. Using genetic data from nuclear (KIAA) and mitochondrial (16s and 12s) genes, we estimate divergence times and identify four major Neurergus clades. The initial speciation event occurred approximately 11.3 million years ago, coinciding with the uplift of the Zagros and Anatolian mountains. This geological transformation isolated newt populations, likely triggering the first speciation event. By integrating potential geographic distribution with climate variables, we reconstruct ancestral niche occupancy profiles. This highlights the critical roles of temperature and precipitation in shaping Neurergus habitat preferences and distribution. We observe both phylogenetic niche conservatism and divergence, with niche divergence playing a dominant role in diversification. This research emphasizes the complex interplay of geography, climate, and ecology in speciation and the vulnerability of isolated mountain newt populations to environmental changes. [ABSTRACT FROM AUTHOR]

Hydration by H 2 O clusters has been shown to be an important means of transporting metal complexes in hydrothermal vapours and low-density supercritical aqueous fluids. However, the effect of hydration on the transport of relatively volatile metal complexes such as those involving bismuth and chloride has not been evaluated. This effect is important to evaluate because bismuth is a key pathfinder element for gold in many intrusion-related gold ore-forming systems, where low-density supercritical aqueous fluids and vapour may play an important role in metal transport. Here, we present the results of experiments investigating the solubility of BiOCl(s) and the speciation of bismuth in HCl-bearing aqueous vapour and low-density supercritical aqueous fluids at temperatures between 250 and 400 °C and pressures of 5 to 296 bar. Two gaseous bismuth species formed in the HCl-bearing fluids (X (HCl) > 0.0005), namely BiCl 3 (g) and BiCl 3 (H 2 O) n (g). Our data clearly show that BiCl 3 (g) is highly volatile at low water fugacity (between 30 and 110 bar) and acts as an unhydrated gas molecule. At higher water fugacity, the gaseous BiCl 3 (g) reacts with water to form hydrated BiCl 3 (H 2 O) n (g) species. Significantly, the stability of hydrated bismuth chloride species, BiCl 3 (H 2 O) n (g), with low hydration numbers is lower than that of the unhydrated species, BiCl 3 (g), resulting in a decrease in bismuth solubility with increasing f (H 2 O). However, at a water fugacity great than 30–110 bar, that increases with increasing temperature, the hydration number and the solubility of hydrated species BiCl 3 (H 2 O) n (g) increase with increasing water fugacity or the density of the fluid. Consequently, unhydrated gaseous bismuth species increase in importance with increasing temperature and become dominant at temperatures > 450 °C in fluids that have low density (<0.10 g/cm3). Hydrated bismuth chloride species are dominant in fluids having higher density (0.10–0.34 g/cm3). The overarching conclusion of this study is that aqueous low-density supercritical fluids, which exsolve from magmas to form intrusion-related gold deposits, can transport bismuth in concentrations (up to hundreds ppm) sufficient to form economic deposits. [ABSTRACT FROM AUTHOR]

A number of regolith-hosted REE occurrences have recently been discovered in the Esperance region in southern Western Australia. This paper summarizes major characteristics of REE mineralization and discusses contributing factors and potential controls. The main aim is to explain why there is a lack of highly sought-after ion-adsorption-clay-type REE deposits across the region despite the presence of the regolith-hosted REE mineralization on a regional scale. Local mineralization mostly occurs as continuous flat-lying enrichment "blankets" within the residual regolith developed over Archaean–Proterozoic granite gneisses and granitoids with elevated REE content. The enriched horizon is commonly located in the lower saprolite and saprock and is accompanied by an overlying REE-depleted zone. This distribution pattern, together with the data on HREE fractionation and the presence of the supergene REE minerals, indicates chemogenic type enrichment formed by supergene REE mobilization into groundwater, downward transport, and accumulation in the lower part of the weathering profile. Residual REE accumulation processes due to bulk rock volume and mass reduction during weathering also contribute to mineralization. It is proposed that climate and groundwater chemistry are the critical regional controls on the distribution of REEs in the weathering profile and on their speciation in the enrichment zone. Cenozoic aridification of climate in southwest Australia heavily overprinted pre-existing REE distributions in the weathering profile. Acidic (pH < 4), highly saline groundwaters intensely leached away any relatively weakly bound, adsorbed or colloidal REE forms, moving them downward. Dissolved REEs precipitated as secondary phosphates in neutral to alkaline environment at lower Eh near the base of the weathering profile forming the supergene enrichment zone. Low denudation rates, characteristic of areas of low relief under the arid climate, are favourable for the preservation of the existing weathering profiles with REE mineralization. [ABSTRACT FROM AUTHOR]