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In this issue of I American Mineralogist i , [2] propose that a mineral paragenetic mode can be defined as "a natural process by which a collection of atoms in solid and/or fluid form are reconfigured into one or more new solid forms." Mineral evolution research ([3]), to some extent, has enriched mineral crystal chemistry. Mineral paragenetic association is the product of mineral evolution to an advanced stage, in which one mineral symbiotic assemblage may correspond to one or more natural processes. [Extracted from the article]

Determination of Fe2+/Fe3+ ratios from metallogenic belts to explore controlling physical and chemical conditions of rock formation is of great significance. In order to explore magnetite Fe2+/Fe3+ ratios of the Qimantag metallogenic belt, part of the Eastern Kunlun orogenic belt in the northeastern margin of the Qinghai–Tibetan plateau, western Central Orogenic Belt of China, and overcome the limitation of the traditional electronic probe, five different measurement methods are proposed and their respective advantages and disadvantages evaluated, with the composition data of the magnetite obtained using electron probe microanalysis (EPMA). The direct oxygen measurement method has a significant impact on the determination results of FeO and Fe2O3, but the accuracy and uniformity of the results are low. The valence method (Flank method) based on the spectral intensity ratio of Lα to Lβ for iron is also unreliable for FeO and Fe2O3 measurements because it is difficult to establish a relationship between Lβ/Lα, the spectral intensity ratio, and the Fe2+/Fe3+ content ratio. In comparison, the charge difference method, the surplus‐oxygen method and the Mössbauer spectrum method are still the most favorable. Mössbauer spectroscopy, with its isomer movement particularly sensitive to the oxidation state of iron, yields results closer to 0.5, which is relatively reliable. Earlier magnetite deposits are located in intrusions or contact zones and formed by magmatic fluids with high Fe2+/Fe3+ ratios, whereas later magnetite deposits are farther away from intrusions and have low Fe2+/Fe3+ ratios. The transformation mechanism of hematite and magnetite in the Qimantage metallogenic belt is also studied. No large volume changes, such as pore filling and shrinkage fracture, were detected in the metallogenic belt, and the transformation mechanism is more similar to a reoxidation and reduction mechanism. [ABSTRACT FROM AUTHOR]

This study has thoroughly uncovered the characteristics of the marine euphotic zone system in the Beibu Gulf, featuring adjacent semiconducting minerals and electrochemically active microbes, via mineralogical characterization, photoelectrochemical measurements, and microbiological analysis techniques. Notably, results of Raman and ESEM with EDS indicated that anatase, the semiconducting mineral with prominent photocatalytic performance, exists in large quantities in the Beibu Gulf. Photoelectrochemical measurements tested photoelectric response and redox activity of suspended particulate minerals, demonstrating the suspended particulates dominated by titanium and iron oxide semiconducting minerals presented excellent photo-response property and distinct photoelectric catalytic potential under visible light irradiation. Its significant property of photoelectric response with 110.483% increment ratio of the average photocurrent density relative to the dark current density. 16S amplicon sequence analysis revealed that the euphotic zone was dominated by Proteobacteria, Actinobacteria, and Cyanobacteria at the phylum level, and by Synechococcus CC9902, Cyanobium PCC-6307 and unclassified Ilumatobacteraceae at the genus level. Halomonas (0.2–1.2%), Vibrio (0.7–1.8%), and Nautella (0.1–1.1%), closely related to semiconducting minerals reduction reaction, were also presented in YL and RGS samples of the Beibu Gulf. This work firstly revealed that the neglected characteristics of the marine euphotic zone system in the Beibu Gulf of the South China Sea, which is an important natural ecosystem for microorganisms to uptake energy sources. It will provide a new perspective for further research on novel ways for microorganisms to acquire energy sources through semiconducting minerals in the marine euphotic zone system. [ABSTRACT FROM AUTHOR]

The present study focuses on an efficient Cr(VI)-reducing bacterial strain (CR-2) isolated from an abandoned chromate plant in Qinghai Province, China. CR-2 was confirmed as Lysinibacillus cavernae using 16S rRNA gene sequencing. CR-2 could survive at 500 mg L−1 Cr(VI) and effectively reduce Cr(VI) at concentrations of <50 mg L−1, a pH of 5–9, a temperature of 20–40 °C, and a salinity of 5–15 g L−1. According to the Box–Behnken experimental design, the maximum Cr(VI) removal efficiency by L. cavernae CR-2 was 76.21% under optimum conditions, which comprised a pH of 6.68, a temperature of 28.90 °C, and a salinity of 9.85 g L−1. With regard to Cr(VI) reduction mediated by L. cavernae CR-2, enhancement in efficiency was observed in the presence of Cu2+ and Ca2+, while significant inhibition in the reduction capacity occurred upon exposure to Mg2+, Ba2+, Ni2+, Pb2+, or Cd2+. Moreover, L. cavernae CR-2 tends to use glucose as an electron donor for the reduction of Cr(VI). Results of cell fraction separation and degeneration indicated that the Cr(VI) removal was primarily due to the reduction of Cr(VI) via chromium reductase in the cytoplasm. In addition, bioanalysis of L. cavernae CR-2 by SEM-EDS and TEM-EDS suggested that Cr was distributed both on the surface and in the cell cytoplasm. FT-IR analyses established that multiple functional groups (hydroxyl, carbonyl, amide, amino, and aldehyde groups) participated in the Cr(VI) biosorption on the cell surface. XPS and HPLC also showed that the Cr(III) end-products could be present as Cr(III) hydroxides or as organic–Cr(III) complexes. This study yields insights into the Cr(VI) bioreduction mechanism of L. cavernae CR-2. [ABSTRACT FROM AUTHOR]

Bioreduction of Cr(VI) is an efficient and environmentally friendly remediation method. In this study, we isolated and screened a strain of Penicillium rubens LR6 that could tolerate to Cr(VI) and investigated its mechanism for removing Cr(VI). We ascertained the factors affecting the ability of strain to remove Cr(VI) through batch experiments. The results revealed that the strain could effectively remove high concentrations of Cr(VI) and exhibit excellent removal efficiency under different environmental conditions. The removal of Cr(VI) by the strain could be accurately explained by the exponential decay equation, where approximately 9.45% of the Cr was immobilized on the microorganisms. We further investigated the ability of different cell fractions to remove Cr(VI) and found that bioreduction was the primary mechanism involved. This was supported by SEM and TEM analyses, which showed the presence of Cr on the surface and inside the cells. Additionally, XPS analysis confirmed the presence of both Cr(VI) and Cr(III) on the cell surface, and FTIR analysis suggested the involvement of amino, carboxyl, and hydroxyl groups in the reduction and fixation of Cr(VI) on the cell surface. The findings offer a novel technique for bioremediation of Cr(VI)-contaminated wastewater in weakly acidic to weakly alkaline and high salinity environments, providing potential solutions for remediating chromium-contaminated environments. [ABSTRACT FROM AUTHOR]

Submarine volcanos are the most active areas in the deep sea, but the environmental consequences of frequent volcanic activity on the geophysical fields and biogeochemical processes near hydrothermal chimneys have not been fully understood yet. In particular, how continuous high‐flux thermal energy, the most typical form of energy in active submarine volcanic systems, affects electron transport and geoelectric field remains unknown. This study provides the first evidence that thermal energy can be efficiently converted to electrical energy at an extremely small spatial scale of the submarine black chimneys. The Seebeck coefficient of sulfide chimneys can reach more than 200 μV/K, with high electrical conductivity of 104 S/m and low thermal conductivity of 1.0 W/(m·K) within 300–700 K. A maximal potential gradient of 300 mV/cm under a temperature difference of 300–700 K can be generated by the thermoelectric conversion of sulfide chimneys, with a maximum energy converting efficiency up to 1%. The thermoelectric conversion effect of a global‐scale submarine volcanos could enable electroactive bacteria to fix appromaxiately 105–106 tons of carbon per year. In addition, the thermal‐electrochemical experiments indicated sulfides underwent rapid oxidation under thermoelectric effects, which may help explain the intense oxidative weathering of sulfides in some anoxic deep‐sea hydrothermal zones. Plain Language Summary: Hydrothermal vents are the most active areas for energy and material exchange in the submarine volcanic systems. The conversion of chemical and biomass energy has been considered as the major driving force for biogeochemical processes in hydrothermal vents, while the primary thermal energy has rarely been a concern. This study revealed that hydrothermal black chimneys could achieve stable thermoelectric conversion with a maximum energy conversion efficiency of 1%. The thermoelectric transport performance of sulfides is mainly influenced by crystal structure, chemical composition and substituting ions. Both the generation of natural electric field and the growth and metabolism of electroactive microorganisms in deep sea are clolsely related to the thermoelectric effects of sulfides. The rapid oxidation of sulfides under a thermoelectric potential well explains the intense weathering of minerals in anoxic seafloor regions. Key Points: Proposing a geoelectric mechanism caused by thermoelectric effects of sulfides in submarine volcanic systemsBuilding a quantitative model to estimate the efficiency of thermoelectric conversion and carbon fixationExplaining rapid oxidative weathering of hydrothermal vent sulfides by thermoelectric mechanism [ABSTRACT FROM AUTHOR]

Cr(VI) is a hazardous environmental pollutant that poses significant risks to ecosystems and human health. We successfully isolated a novel strain of Bacillus mobilis, strain CR3, from Cr(VI)-contaminated soil. Strain CR3 showed 86.70% removal capacity at 200 mg/L Cr(VI), and a good Cr(VI) removal capacity at different pH, temperature, coexisting ions, and electron donor conditions. Different concentrations of Cr(VI) affected the activity of CR3 cells and the removal rate of Cr(VI), and approximately 3.46% of total Cr was immobilized at the end of the reaction. The combination of SEM–EDS and TEM-EDS analysis showed that Cr accumulated both on the cell surface and inside the cells after treatment with Cr(VI). XPS analysis showed that both Cr(III) and Cr(VI) were present on the cell surface, and FTIR results indicated that the presence of Cr on the cell surface was mainly related to functional groups, such as O–H, phosphate, and -COOH. The removal of Cr(VI) was mainly achieved through bioreduction, which primarily occurred outside the cell. Metabolomics analysis revealed the upregulation of five metabolites, including phenol and l-carnosine, was closely associated with Cr(VI) reduction, heavy metal chelation, and detoxification mechanisms. In addition, numerous metabolites were linked to cellular homeostasis exhibited differential expression. Cr(VI) exerted inhibitory effects on the division rate and influenced critical pathways, including energy metabolism, nucleotide metabolism, and amino acid synthesis and catabolism. These findings reveal the molecular mechanism of Cr(VI) removal by strain CR3 and provide valuable insights to guide the remediation of Cr(VI)-contaminated sites. [ABSTRACT FROM AUTHOR]

Microbially induced formation and transformation of clay minerals are known to be ubiquitous in nature. This work investigated the smectite-to-kaolinite transformation by Bacillus mucilaginosus, a kind of silicate-weathering bacterium. Results showed that the microbe-smectite system doubled protein production compared with the abiotic controls and enhanced dissolved 1.6% of total Si and 0.9% of total Al from smectite after the 25 days experiment. The formation of kaolinite was verified through its distinguished d(001)-spacing of 0.710 nm revealed by synchrotron radiation X-ray difrac-tion (SR-XRD) and high-resolution transmission electron microscope (HR-TEM). HR-TEM analysis indicated some mixed layers of smectite and kaolinite appeared in the form of a super-lattice structure. Moreover, the compositional and morphological changes of the solids suggested the emergence of kaolinite was associated with the formation of amorphous SiO2 and fragmented clay particles with lower Si/Al ratio and exposed crystal edge. Based on the detection of –C=O species on the smectite surface and the decrease of pH from 8.5 to 6.5, we inferred the organic ligands secreted by Bacillus mucilaginosus complexed with cations, especially for Si, which stripped the tetrahedral sheets and promoted the kaolinization of smectite. To our knowledge, this is the first report of microbially induced smectite-to-kaolinite transformation under ambient conditions in a highly-efficient way. This work could shed light on a novel pathway of microbe-promoted weathering of smectite to kaolinite at the Earth surface conditions. Such a robust and eficient transformation from expansive smectite to non-expansive clays as kaolinite may be of great potential in enhancing oil recovery in reservoirs. [ABSTRACT FROM AUTHOR]

This study investigates the biomineralization of lead ions by Aspergillus niger from aqueous environments, focusing on the dynamic effects of fungal metabolism and biological components. Three biomolecules (glutamate, methionine, and lysine) were used to induce lead oxalate mineralization under lead stress. Comparative experiments were conducted to analyze the growth characteristics and Pb (II) removal ability of A. niger, as well as the morphological and structural properties of the resulting lead oxalate minerals using inductively coupled plasma atomic emission spectroscopy, X‐ray powder diffraction, and scanning electron microscopy–energy dispersive spectroscopy techniques. The findings reveal that A. niger plays a crucial role in controlling the mineralization process of Pb (II), with biomineralization experiments demonstrating the specific morphogenesis of lead oxalate over time. Additionally, the inclusion of the three biomolecules in the system indirectly influenced the rate of Pb (II) removal and mineral morphology. These results contribute to a better understanding of A. niger‐mediated biomineralization process of lead oxalate and suggest its potential application in the removal of Pb (II) from aqueous environments, particularly in combination with amino acids for enhanced immobilization and mineral recovery. Practitioner Points: Fungal activity and amino acids play a crucial role in shaping lead oxalate crystals during water treatment processes.Specific amino acids can effectively delay lead oxalate recrystallization, enhancing the stability and removal efficiency of the crystals.Biomineralization mediated by fungi offers a promising and eco‐friendly approach for lead removal and recovery in wastewater treatment.Exploring the influence of organic additives and fungal metabolism on crystal growth provides valuable insights for developing efficient remediation strategies.Further research on the utilization of fungi and amino acids can help with innovative and sustainable wastewater treatment technologies. [ABSTRACT FROM AUTHOR]

Dolomite exhibits a wide distribution in geological strata. The metabolic activities of microorganisms in marine sediments play a crucial role in the formation of dolomite. Semiconducting minerals, such as hematite, goethite, and rutile, generate photoelectrons when exposed to sunlight, which can impact the community structure and metabolic activities of microorganisms. In this study, a simulated photoelectron system was conducted to investigate the response of the microbial community, as well as the regulation of sulfate reduction, to photoelectrons using high-throughput sequencing of the 16S rRNA gene. The regulatory effect of semiconducting mineral photoelectrons on the induction of carbonate precipitation by sulfate-reducing bacteria was explored. X-ray diffraction and Raman spectroscopy were used to characterize carbonate precipitation. During cultivation, the pH values of the system increased from 8.0 to approximately 8.5 and the rate of sulfate reduction was significantly enhanced under the influence of simulated photoelectrons. The alpha diversity of the microbial community decreased, and the semiconducting mineral photoelectronic system had a promoting effect on the enrichment of sulfate-reducing bacteria, mainly Desulfovibrio. Under the regulation of photoelectrons, sulfate-reducing bacteria can effectively oxidize organic matter and reduce sulfate in the environment, and proto-dolomite can be formed at a low Mg/Ca ratio. This process has important implications for carbon and sulfur element cycling in estuarine and oceanic photic zones, and provides a new explanation for the formation of large amounts of dolomite in geological history. [ABSTRACT FROM AUTHOR]

Native sulfur (denoted as S0) has been regarded as the crucial species in the biogeochemical cycle of sulfur, and the opening of its eight-membered rings is critical to its activation. However, due to the extreme difficulty in detecting transient ring-opening species, the activation process and inducing factors have yet to be revealed. This study investigates the external (incident optical energy) and internal factors (impurity elements) that trigger the opening of S0 ring, and the underlying activation mechanisms by combining optical measurements, theoretical calculations, and photochemical experiments. Synchrotron radiation in situ X-ray absorption near edge spectra confirms that S0 can undergo ring-opening reactions under light irradiation below ∼575 nm, which results from electron transition via indirect bandgap. Density functional theory calculations and ab initio nonadiabatic molecular dynamics reveal that photo-assisted electron transition evokes ring opening in the femtosecond scale, resulting in a new chain-like molecular configuration with changed charge density and electronic structure. Compared with the ring-like structure, the ring cleavage can provide two unpaired electrons on the terminal S atoms as reactive sites for reducing bicarbonate to formate. The room-temperature bandgap of four S0 samples with different substituting concentrations of impurity elements (mainly As and Se, up to 282.0 and 19.3 μg/g, respectively) decreases linearly with the increase of doping amount. It confirms that As and Se can add 4p orbitals into the S 3p -dominated valence and conduction band of S0, thus reducing the energy required for electron transition and promoting the ring-opening reaction. S0 sample with 282.0 μg/g of As would produce much less HCOOH (3.3 nM·g·h−1·m−2) from carbonates compared with the few-As sample (34.0 nM·g·h−1·m−2), attributed to the new three bonds of As with only one active unpaired electron left after ring opening. Uncovering the critical roles of ring-opening reactions in improving the chemical activities of S0 under the impact of natural light and impurity elements can significantly deepen the understanding of molecular crystalline mineral S0 and the involved biogeochemical sulfur cycle. [ABSTRACT FROM AUTHOR]

The chromium slags left by industry emission has caused serious damage to the local ecological environment, and microorganisms were sensitive to the variation in the surrounding environmental factors. In this work, 14 soil samples around an abandoned chromate factory were collected. We utilized the 16S rRNA regions from soil DNA to explore the possible effects of environmental factors on soil bacterial communities. High-throughput DNA sequencing results suggested that bacterial communities varied greatly from different soil samples, but Actinobacteria and Proteobacteria were predominant in all samples in the phylum level. In addition, Pseudarthrobacter, Thiobacillus, Paenisporosarcina, Sphingomonas, and Bacillus were abundant at a more refined species level. Based on redundancy analysis (RDA) and variation partitioning analysis (VPA), the results revealed that pH value, soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), chromium (Cr) and lead (Pb) could obviously affect the bacterial community structure. Heavy metals, soil nutrients, and pH could explain 37.69%, 13.61%, and 31.41% of bacterial community variation, respectively. This study would provide a theoretical basis for future remediation of local Cr-contaminated soil. [ABSTRACT FROM AUTHOR]

In the estuary and nearshore environments, suspended particulate matter (SPM) plays a particularly important role. This article presents a study on the suspended particulate matter and microbial communities in the euphotic zone of China's nearshore and estuarine regions. The study used various analytical techniques, including ICP-OES, SR-XRD, confocal Raman microscopy, ESEM, and EDX, to investigate the spatial distribution and elemental and mineral compositions of the suspended particulate matters. The study found that semiconducting minerals, such as iron oxide, sulfide minerals (hematite, goethite, and pyrrhotite), and titanium oxide minerals (rutile and anatase), were widely present in the suspended particulate matter. This discovery highlights the photochemical activity of suspended particulate matter in the euphotic zone. Furthermore, a correlation analysis of microbial communities revealed that the content of suspended particulate matter was positively correlated with denitrifying bacteria and metal-reducing bacteria in seawater. This study provides valuable insight into the ecosystem dynamics and biogeochemical cycling of estuaries and coastal seas, which are critical for sustaining the biodiversity and productivity of these ecosystems. [ABSTRACT FROM AUTHOR]

High concentrations of lead (Pb) in agricultural soil and wastewater represent a severe threat to the ecosystem and health of living organisms. Among available removal techniques, microbial remediation has attracted much attention due to its lower cost, higher efficiency, and less impact on the environment; hence, it is an effective alternative to conventional physical or chemical Pb-remediation technologies. In the present review, recent advances on the Pb-remediation mechanisms of bacteria, fungi and microalgae have been reported, as well as their detoxification pathways. Based on the previous researches, microorganisms have various remediation mechanisms to cope with Pb pollution, which are basically categorized into biosorption, bioprecipitation, biomineralization, and bioaccumulations. This paper summarizes microbial Pb-remediation mechanisms, factors affecting Pb removal, and examples of each case are described in detail. We emphatically discuss the mechanisms of microbial immobilization of Pb, which can resist toxicity by synthesizing nanoparticles to convert dissolved Pb(II) into less toxic forms. The tolerance mechanisms of microbes to Pb are discussed at the molecular level as well. Finally, we conclude the research challenges and development prospects regarding the microbial remediation of Pb-polluted environment. The current review provides insight of interaction between lead and microbes and their potential applications for Pb removal. [ABSTRACT FROM AUTHOR]

Silicate minerals are essential bricks of solid planets, which have been studied deeply by infrared absorption spectroscopy. Along with the rapid development of planetary exploration, infrared emission spectroscopy and corresponding radiation properties of minerals have been receiving attention. However, systematic research on silicate minerals using infrared emission spectroscopy has been absent so far. In this work, various silicate minerals (totally ten in five series included nesosilicates, eyclosilicates, inosilicates, phyllosilicates and tectosilicates) were investigated infrared spectral characteristics and infrared radiation properties using X-ray diffraction, X-ray fluorescence, and infrared spectroscopy (absorption and emission spectroscopy). Results indicated that the assignment of each band in infrared emission spectra of all samples could be obtainable referring to the well-known infrared absorption spectra, presenting a dominant absorption band near 1000 cm−1 related with the stretching of Si–O bonds and several weak bending-driven absorption bands in the range of 400–650 cm−1. A good linear relationship (coefficient of determination R2 = 0.996) between two corresponding wavenumbers suggested emission bands of silicate minerals have great correspondence with their absorption bands. Both vibrational stretching and bending of Si–O bonds in both spectra regularly shifted to higher frequencies as the increase of Si/O from 0.25 for nesosilicates and 0.50 for tectosilicates. The average emissivity of silicates, obtained from radiation energy spectra from 400 to 2000 cm−1 in the temperature range of 50–140 °C, showed all silicate minerals presented relatively higher emissivity (> 0.910) and displayed a remarkable reduction from nesosilicates (e.g., 0.981 for forsterite) to tectosilicates minerals (e.g., 0.913 for quartz). It was thus concluded that higher emissivity of silicates was attributed to the decrease of polymerization degree of SiO4 tetrahedron (R2 = 0.86), vibrational frequency and range for Si–O stretching (R2 = 0.88, 0.92, respectively), and vibrational range for Si–O bending (R2 = 0.85). This work gets insight into the relationship among spectral characteristics, crystal chemistry, and radiation properties of silicate minerals, and would help accurately identify and distinguish various silicate minerals in remote sensing analysis for understanding the composition of planetary surfaces and their evolutionary path. [ABSTRACT FROM AUTHOR]

We report the crystal structure of allanite-(Ce), with composition (Ca1.0REE0.9□0.1)Σ2.0(Al1.46Fe3+0.52Fe2+0.76Mg0.12Ti0.15)Σ3.01Si3O12(OH) from the Xinfeng rare earth element (REE)-bearing granite in Guangdong Province, China. It has the unit cell a = 8.9550(4) Å, b = 5.77875(16) Å, c = 10.2053(4) Å, β = 114.929(5)° and Z = 2 in space group P21/m and is characterised by site splitting at M3 into M3a and M3b, at a distance of 0.38(3) Å, which are occupied partially by Fe0.764Mg0.12 and Ti0.15, respectively. The structure was determined by single-crystal X-ray diffraction and refined with anisotropic full-matrix least-squares refinement on F2 to R1 = 2.82%, wR2 = 7.77% for 1856 independent reflections (8772 collected reflections). However, M3 splitting is not present in either ferriallanite-(Ce) or epidote, in which M3 is almost fully occupied either by Fe2+ or by Fe3+. Comparisons of bond lengths and volumes in cation polyhedra among allanite-(Ce), ferriallanite-(Ce) and epidote tend to indicate that the essential factor that facilitates site splitting of M3 in allanite-(Ce) is heterovalent substitution and occupation of a crystallographic site between Fe2+(Mg2+/Mn2+)–Al3+(Ti4+), a common phenomenon in minerals, such as the plagioclase series. Fine structure analysis of the M3 split model revealed that deformation of A2 is related closely to distorted M3, which is consistent with Fe2+ incorporation following REE substitution. [ABSTRACT FROM AUTHOR]

• The water oxidation activity of birnessite was significantly altered by the doping ions. • Ca-birnessite exhibits a smaller overpotential of 579 mV at 10 mA/cm2 compared to K-birnessite. • Doping-Ca enhanced the kinetic properties with a significant reduction of 100 mV/dec in the Tafel slope. Birnessite is an affordable and high-efficiency catalyst for water oxidation. In this study, we attempted to doping Ca into birnessite to investigate the influence on its photocatalytic oxidation activity. The study was carried out through a combination of experimental investigations and DFT calculations of the relevant crystal and electronic structures. The analysis of Raman spectra using 2T2D correlation and DFT indicates that Ca contributes more to the high frequency regions (400–600 cm−1) than K. DFT further reveals that the introduction of Ca leads to an increase in the number of localized electrons at the Fermi energy level and in the conduction band. Photo-electrochemical experiments demonstrate a significant reduction of 100 mV/dec in the Tafel slope, along with a 1.48-fold increase in photo-current density for Ca-birnessite when compared to K-birnessite. In general, the results demonstrate that Ca-birnessite can effectively heighten visible light absorption, reduce the band gap, and enhance water oxidation activity. [ABSTRACT FROM AUTHOR]

Pedogenic weathering of aeolian materials plays an essential role in global nutrient and carbon cycling. A quick and effective approach for temporally high‐resolution and spatially large‐scale pedogenic investigations has long been needed. Here, we used visible and near‐infrared, mid‐infrared and sensor‐fused data to predict pedogenesis‐related soil properties (i.e., grain‐size distribution, clay‐mineral properties and geochemical ratios) in a thick loess sequence in central China. Sensor fusion was achieved at three different levels: (1) direct combination of spectral parameters (low‐level fusion; Fusionpara); (2) combination of spectral features selected by principal component analysis (middle‐level fusion; FusionPCA) and (3) fusion using outer product analysis (high‐level fusion; FusionOPA). Sensor‐fusion generally improves the model predictions for all soil properties, with increases in the values of the model efficiency coefficient (MEC) of 8% and the performance‐to‐interquartile range of 12%. Whole‐soil properties are optimally predicted with the Fusionpara dataset using the random forest algorithm, yielding a mean MEC of 0.85. Spectral parameters D2200/D1900 and AS2200 are demonstrated as promising new pedogenic proxies, with higher values indicating more intense hydrolysis during pedogenesis. Spectral proxies along the loess sequence suggest that intense soil formation occurred during warm and humid interglacial periods when the East Asian summer monsoon intensified. The sensor‐fusion technique improved model performance for assessing mineral transformations and chemical weathering intensity, providing a quick and efficient means of interpreting pedogenic evolution, especially in the case of spatially large‐scale soil investigations. Highlights: Fusion of VNIR and MIR spectra to model loess pedogenesis.Spectral modeling provides a robust surrogate for pedogenic evolution studies.Sensor fusion improves the performance of chemometric models.Sensor‐fusion models can reconstruct loess pedogenesis. [ABSTRACT FROM AUTHOR]

The energy conversion in Earth's surface environments over geological history heavily involves the redox reactions of natural minerals. Natural Mn(III/IV) oxides and Mn2+(aq) is one of the most important redox couples that significantly dictate the electron flow in nature. Elucidating their formation and redox reactions is of critical importance for understanding numerous elemental cycles and the evolution of redox environments on Earth and other planets. Previous studies generally consider biotic processes as the dominant oxidation pathway for Mn2+(aq) in natural environments. In this study, we demonstrate rapid abiotic oxidation of Mn2+(aq) through photocatalytic reactions in the presence of natural Fe oxide minerals at rates comparable to those of currently known biotic/abiotic oxidation processes. Fe oxide minerals not only facilitate the electron transfer, but also serve as templates for the heterogeneous nucleation of tunnel structured Mn oxides. This finding highlights an important yet previously overlooked abiotic process on the formation of Mn oxides, which offers a new pathway for explaining the commonly observed co-occurrence of Fe and Mn oxide minerals in nature and the origin of diverse structures of Mn oxides. [ABSTRACT FROM AUTHOR]

Natural hydrogen (H2) has gained considerable attentions as a renewable energy resource to mitigate the globally increasing environmental concerns. Low‐temperature serpentinization (<200 °C) as a typical water–rock reaction is a major source of the natural H2. However, the reaction mechanism and the controlling step to product H2 remained unclear, which hinders the further utilization of natural H2. Herein, we demonstrated that the H2 production rate could be determined by the Fe(OH)2 oxidation during low‐temperature serpentinization. Moreover, the co‐existence of Ni2+ could largely enhance the H2 production kinetics. With the addition of only 1 % Ni2+, the H2 production rate was remarkably enhanced by about two orders of magnitude at 90 °C. D2O isotopic experiment and theoretical calculations revealed that the enhanced H2 production kinetics could be attributed to the catalytic role of Ni2+ to promote the reduction of H2O. [ABSTRACT FROM AUTHOR]

Natural hydrogen (H2) has gained considerable attentions as a renewable energy resource to mitigate the globally increasing environmental concerns. Low‐temperature serpentinization (<200 °C) as a typical water–rock reaction is a major source of the natural H2. However, the reaction mechanism and the controlling step to product H2 remained unclear, which hinders the further utilization of natural H2. Herein, we demonstrated that the H2 production rate could be determined by the Fe(OH)2 oxidation during low‐temperature serpentinization. Moreover, the co‐existence of Ni2+ could largely enhance the H2 production kinetics. With the addition of only 1 % Ni2+, the H2 production rate was remarkably enhanced by about two orders of magnitude at 90 °C. D2O isotopic experiment and theoretical calculations revealed that the enhanced H2 production kinetics could be attributed to the catalytic role of Ni2+ to promote the reduction of H2O. [ABSTRACT FROM AUTHOR]

The Jingren deposit is part of the Qimantage metallogenic belt within the eastern Kunlun orogenic belt, the largest metallogenic belt in Qinghai Province, northwestern China. Exploration data show that the metal resources of the Jingren deposit are greater than 93000 t in a mining area of 76.15 km2, which indicates significant exploration potential in the near future. Three W–E‐trending faults, F1‐3, dominate the extension of the mineralization zone, which consists of chalcopyrite, pyrite, magnetite, galena, sphalerite, and molybdenite as well as bismuth‐bearing minerals. The deposit contains a large amount of late Triassic intrusive rocks, however, previous research did not reach a consensus on the timing or the origin of the mineralization owing to a lack of geochronological data and poor exposure conditions. In the present study, Re‐Os isotopic dating from six molybdenite samples collected from a borehole of the granodiorite in the Jingren deposit using negative thermal ionization mass spectrometry (NTIMS) showed 187Re and 187Os concentrations of 0.26–4.40 ppm and 1.03–16.46 ppb, respectively, with an initial 187Os/188Os value of 0.06 ± 0.19. This proves that the Jingren deposit has a metallogenic age of (225 ± 4) Ma and is the product of united mineralization of the Qimantage metallogenic belt and that the Jingren deposit might actually be an Indosinian metallogeny. In addition, the Re content of these samples, at 0.42 ppm to 7.00 ppm shows that the mineralization was derived mainly from a crustal source. Furthermore, electron probe microanalysis (EPMA) conducted on chalcopyrite obtained from 22 metallic mineral samples revealed (Fe + Cu)/S ratios of 1.801–1.947 with an average of 1.852, which is lower than the ideal value (1.875). Besides, the main ore body formed in a relatively higher temperature environment than the surrounding rocks in the Jingren deposit. These data indicate that the Jingren deposit formed in a metallogenic environment at lower temperature. Moreover, according to the TiO2‐Al2O3‐(MgO + MnO) and TiO2‐Al2O3‐MgO genetic classification diagram for magnetite, the Jingren deposit most likely belongs to the skarn family. In addition, the Co‐Ni‐As genetic classification diagram of the pyrite indicates sedimentary and skarn genetic characteristics. [ABSTRACT FROM AUTHOR]

Hematite is usually considered as a terminal electron acceptor for dissimilatory metal-reducing bacteria (DMRB), such as Shewanella oneidensis MR-1. However, hematite is also a semiconductor with visible light response. How the photocatalytic activity of hematite affects its electrical interplay with DMRB, as well as its role in relevant biogeochemical processes under sunlight, is still unclear. In this study, we investigated the effect of hematite on Cr(VI) removal by S. oneidensis MR-1 in the dark versus under stimulated sunlight using both batch experiments and photoelectrochemical analysis in a solar-assisted microbial photoelectrochemical system with a hematite photoanode covered by S. oneidensis MR-1. Under the dark conditions, hematite at low mineral-to-cell ratios can promote Cr(VI) removal through adsorbing both Cr(VI) and bacteria on/near hematite surface, which facilitates Cr(VI) bio-reduction and also alleviates self-poisoning processes of cells with time. However, as mineral-to-cell ratios reach a high level, hematite particles may cover cell surface and impact Cr(VI) bio-reduction, leading to the decreased Cr(VI) removal with increasing hematite particles. Under simulated sunlight, S. oneidensis MR-1 generates electrons from lactate metabolism and utilizes them to fill photoexcited holes in hematite, generating photoexcited electrons to reduce Cr(VI). Thus, in addition to directly enzymatic reduction of Cr(VI), the new light-triggered electron transfer pathway: lactate → S. oneidensis MR-1 → hematite → Cr(VI) further increases Cr(VI) removal and lactate metabolism. Also, the time-dependent cell survival is increased by the presence of hematite under the simulated sunlight, probably owing to the promoted Cr(VI) reduction and accumulation of Cr(III)-products on hematite surface. Moreover, organic hole scavenger, such as Ethylenediaminetetraacetic acid (EDTA), can further enhance Cr(VI) removal by hematite and S. oneidensis MR-1 under light irradiation. The photoelectrochemical results confirm that the light-triggered electron transfer pathway can be promptly and repeatedly produced upon illumination, and the rapid decrease of photocurrents after spiking Cr(VI) indicates Cr(VI) reduction by the photogenerated electrons from hematite. These findings suggest that semiconducting minerals, like hematite, can harvest solar energy to boost microbial metabolism and contaminant transformation by non-phototrophic, electroactive bacteria, which in turn increases bacterial tolerance toward toxic compounds in surrounding environments. [ABSTRACT FROM AUTHOR]

• Primary Mn, Mo, Ce and Cr minerals evolved periodically after the GOE. • The evolutionary dynamics of high-valent minerals followed Mn>Ce>Mo>Cr. • All minerals kept continuous deposition and active evolution from 1.8 to 0.8 Ga. • There are two depositional discontinuities around the GOE and the NOE. Understanding the co-evolution of redox-sensitive minerals is crucial for unraveling Earth's oxygenation history. In this study, we used a global-scale mineralogical dataset encompassing 12,141 samples of both the primary and secondary minerals containing manganese (Mn), molybdenum (Mo), chromium (Cr) and cerium (Ce), and 18,777 samples of primary phosphorus (P) and carbon (C) minerals. By developing mathematical models of evolutionary dynamics, we quantified the time lag between changes in the atmospheric oxygen level (p O 2) and the corresponding response in the evolution of these minerals. The analysis revealed that the evolutionary time lag sequence of high-valent Mn, Ce, Mo and Cr minerals after 2.4 Ga, aligns with the thermodynamic sequence of oxidation reactions, with Mn and Ce minerals displaying the most rapid dynamic response, followed by Mo and Cr minerals (denoted as MnIV>CeIV>MoVI>CrVI). All minerals maintained active and continuous evolution throughout the period of orogenic quiescence from 1.8 to 0.8 Ga, but have two depositional discontinuities during the Great Oxidation Event (the GOE) and the Neoproterozoic Oxidation Event (the NOE) (C, P minerals had a depositional slowdown at around the NOE). The collective missing of mineralogical records pointed to the rapid evolution of the Earth's internal and external environment, and is possibly caused by a sharp decrease in material input (such as the tectono-magmatic lull or slowdown) or strong secondary alterations at around the GOE and the NOE. The quantitative analysis on the evolutionary dynamics of redox-sensitive minerals may contribute to refining proxies that constrain the evolving redox state of deep-time Earth. [ABSTRACT FROM AUTHOR]

Many paleo-karstic bauxite deposits contain elevated concentrations of Ni and Co. It has been known that Co and Ni are dominantly hosted in sulfides, but it remains unclear how Ni and Co were incorporated into sulfides and what kind of physiochemical conditions were involved. The Maochang bauxite deposit, as one of the large Ni- and Co-bearing paleo-karstic bauxite deposits in Guizhou Province, southwest China, was selected to tackle these questions. Detailed mineralogical and sulfur isotopic analyses using integrated EBSD, EPMA, LA-ICPMS, and LA-MC-ICPMS methods revealed three stages of sulfide mineralization: stage I with pyrite (PyI), stage II with pyrite (PyII), millerite, sphalerite, chalcopyrite and violarite, and stage III with pyrite (PyIII), chalcopyrite and galena. The fine-grained, euhedral PyI has up to 0.79 wt% Ni and up to 0.53 wt% Co. In contrast, PyII, which replaced or overgrew PyI, exhibits high but variable Ni, Co and As contents, and is further divided into three sub-types: Ni-rich PyII-a (up to 16.54 wt% Ni, 0.94 wt% Co, and 0.38 wt% As) and PyII-b (up to 3.30 wt% Ni, 1.41 wt% Co, and 0.36 wt% As), and Co-rich PyII-c (up to 0.99 wt% Ni, 7.57 wt% Co, and 1.81 wt% As). PyIII is Ni- and Co-poor. Ni increases from PyI to PyIIa and PyIIb, and then decreases to PyIIc and PyIII, whereas Co remains at similar levels for PyI, PyIIa and PyIIb, significantly increases to PyIIc, and then drops abruptly to PyIII. δ34S V-CDT values vary dramatically from negative values for PyI (−6.9 to −16.6‰) to positive values for PyII-b (+19.4 to +22.8‰), sphalerite (+17.2 to +19.7‰), and PyIII (+25.3 to +32.3‰). Based on these results, and considering that the protoliths of the bauxites were likely Ni- and Co-rich black shales according to previous studies, a four-step model is proposed to explain the enrichment of Ni and Co in the bauxites: 1) during weathering and bauxite formation on the surface, Ni and Co were leached from the black shale together with sulfate; the metals were dissolved in the solution and partly adsorbed by Fe-oxides/hydroxides under moderate to high f O2 ; 2) during early diagenesis, the sulfate was partially reduced to sulfide via the bacterial sulfate reduction (BSR) process and formed PyI; much of the Ni and Co, together with sulfate, remained in the solution; 3) with increasing burial, temperature increased and f O2 decreased, and the remaining sulfate (with elevated δ34S V-CDT) was reduced to sulfide via the same BSR process and formed PyII; Ni was largely consumed and incorporated into PyIIa and PyIIb, whereas Co remained in the solution until precipitation of PyIIc; 4) by the time of PyIII precipitation, both Ni and Co had been taken by PyII, leaving a Ni- and Co-poor solution and PyIII. Step 1 occurred in a relatively open system, whereas steps 2–4 likely occurred in a closed system. [Display omitted] [ABSTRACT FROM AUTHOR]

The interactions between widespread iron (oxyhydr)oxides (Fe oxides) and natural soil dissolved organic matters (DOM) are the dominant drivers in the geochemical behavior of Fe and the cycle of carbon in soil. Under visible light irradiation, their interactions become more complex due to the unique semiconducting structure of Fe oxides and complex components in DOM, which have not been deeply studied. In this study, the complex reactions occurred at the DOM-goethite interface under irradiation were investigated in detail. Fe2+ (aq) from goethite reductive dissolution was accumulated at the DOM-goethite interface, along with the generation of reactive oxidative species (ROS). The reasons could be ascribed to the enhanced generation of photoelectron from the conduct band of goethite, ligand-to-metal charge transfer and photolysis of Fe(III)-carboxylate complexes. Moreover, the generated ROS were the main driving forces in the coupling process of Fe redox cycle and oxidative decomposition of DOM at goethite surface, inducing the formation of secondary Fe minerals and chemical composition change of DOM. This work provided new insights into the light-induced coupling process of Fe semiconducting minerals reductive dissolution and dissolved organic matters oxidation in top soil. [Display omitted] • Fe2+ were accumulated at the DOM-goethite surface under irradiation. • ROS were generated significantly at the DOM-goethite surface under irradiation. • ROS played a major role in Fe redox cycling at the goethite surface. • Oxidative decomposition of DOM was caused by ROS. [ABSTRACT FROM AUTHOR]

• 3D spectral model developed to fingerprint loess soils using principal component analysis. • Sensor fusion improves the performance of machine-learning-based models. • Spectral modeling provides alternative to mineral/geochemical pedogenic proxies. • Loess deposits from various climatic zones were influenced by the Asian monsoons. • Spectral modeling facilitates large-scale investigation of environmental changes. Loess deposits are important records of the evolution of the soil environment and pedogenic weathering. Changes in pedogenic weathering conditions through space and time, as well as discrimination/sourcing of loess-derived soils, are important scientific issues in the soil (paleosol) community. Here, 502 soil samples from four loess chronosequences representing different climatic zones of China were investigated using portable X-ray fluorescence (PXRF) and visible to near-infrared reflectance (VNIR) in combination with previously published mineralogic and magnetic datasets. A spectral modeling approach was employed to discriminate loess-derived soils from different regions of China. We developed a three-dimensional model to fingerprint loess-derived soils using principal component analysis (PCA), showing that soils accumulating under varying climatic conditions were effectively discriminated with sensor fusion data. Six key soil mineralogic and magnetic attributes serving as pedogenic-weathering proxies were analyzed and predicted with conventional methods and chemometric models. Predictive models were constructed with machine learning methods, including partial least squares regression (PLSR), random forest (RF), and Cubist algorithms. The results indicate that the Cubist algorithm works better than PLSR and RF in predicting pedogenic-weathering proxies. The cross-validation results indicate that, although models derived from single sensors (i.e., PXRF or VNIR) work well in predicting pedogenic-weathering proxies, the sensor fusion approach is superior with regard to accuracy and robustness of results in most cases. We suggest that the combined elemental and secondary-mineral information provided by the fused PXRF-VNIR datasets can yield high-accuracy models in soil (paleosol) investigations. The sensor fusion models reveal that pedogenic processes in the loess chronosequences are diversified both spatially and temporally in different climate zones of China. Our results suggest that spectral modeling can be an alternative to geochemical, mineralogic and magnetic pedogenic-weathering proxies, and that it has great potential for investigating soil-forming conditions and pedogenic-weathering evolution, especially when large-area and/or high-resolution analysis is required. [ABSTRACT FROM AUTHOR]

• Reveal the microorganism-mineral electron transfer in the euphotic zone. • Extracellular electron transfer from P. aeruginosa PAO1 to semiconducting anatase. • Anatase with photoelectric activity promotes extracellular electron transfer. • Both direct and indirect electron transfer appear between anatase and PAO1. • Pyocyanin and pili of PAO1 dominate extracellular electron transfer process. Focusing the marine euphotic zone, which is the pivotal region for interaction of solar light-mineral-microorganism and the elements cycle, we have conducted the research on the mechanism of semiconducting minerals promoting extracellular electron transfer with microorganisms in depth. Therein, anatase which is one of the most representative semiconducting minerals in marine euphotic zone was selected. The mineralogical characterization of anatase was identified by ESEM, AFM, EDS, Raman, XRD, and its semiconducting characteristics was determined by UV–Vis and Mott-Schottky plots. Determined by the electrochemical measurement of I-t curves, the photocurrent density of anatase was more prominent than dark current density. Pseudomonas aeruginosa PAO1 was widely distributed in the euphotic zone, and its mutants of operons deficient in biosynthesis pyocyanin (Δ phz1 Δ phz2) and pili deficient (Δ pilA) were employed in this study. I-t curves indicated that both direct and indirect extracellular electron transfer processes occurred between anatase and PAO1. The indirect electron transfer depending on pyocyanin secreted by PAO1 was the main electron transfer mode. This work demonstrated the light-driven extracellular electron transfer and further revealed the photo-catalyzed mechanisms between anatase and PAO1 in marine euphotic zone. [ABSTRACT FROM AUTHOR]

Natural semiconducting minerals are widely distributed in supergene environments and are famous for their solar-driven redox activities, in which wolframite (Fe x Mn 1-x WO 4) as a fascinating member got less attention. In this work, the semiconducting photocatalytic activities of Fe x Mn 1-x WO 4 series samples (x = 1, 0.74, 0.48, 0.24, 0) influenced by their crystal chemistry were investigated. The bandgaps of MnWO 4 , Fe 0.24 Mn 0.76 WO 4 , Fe 0.48 Mn 0.52 WO 4 , Fe 0.74 Mn 0.26 WO 4 and FeWO 4 as measured by UV–vis diffuse reflection (DRS), were 2.7, 2.4, 2.3, 2.2, and 2 eV, respectively, which were linearly decreased (R2 = 0.971) when x increased from 0 to 1. The density functional theory (DFT) calculations further indicated with the increasing content of Fe, the contribution of valence-band maximum (VBM) was stepwise occupied by Fe 3d orbits and the bandgap was thus gradually decreased. The photocatalytic activities of Fe x Mn 1-x WO 4 samples were examined on the degradation of methylene blue (MB, 5 mg/L). The MB removal rate was the highest in Fe 0.74 Mn 0.26 WO 4 system, which was 3.2, 1.9, 1.2, and 1.5 times faster than that of MnWO 4 , Fe 0.24 Mn 0.76 WO 4 , Fe 0.48 Mn 0.52 WO 4 , and FeWO 4 , respectively. The concentration of produced hydroxyl radical (•OH) by Fe x Mn 1-x WO 4 , detected in electron paramagnetic resonance (EPR) measurement, had a positive correlation with the degradation rate of MB. The degradation rate slowed down when •OH was removed, demonstrating that •OH was the major reactive oxygen species in the photocatalytic oxidative degradation of MB. The best-performing Fe 0.74 Mn 0.26 WO 4 photocatalytically produced the most •OH, which was closely linked with its most abundant oxygen-vacancy defects, revealed by X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL) spectroscopy. It thus can be concluded that narrow bandgap and appropriate oxygen vacancies can give rise to synergistic effect on the improvement of photocatalytic performance. This study helps get insight into the role of crystal chemistry in semiconducting properties and photocatalytic activities of wolframite, which also puts forward a new strategy to control environmental pollution by using natural minerals. [ABSTRACT FROM AUTHOR]