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Manganese (Mn) oxides have been prevalent on Earth since before the Great Oxidation Event and the Mn cycle is one of the most important biogeochemical processes on the Earth's surface. In sunlit natural environments, the photochemistry of Mn oxides has been discovered to enable solar energy harvesting and conversion in both geological and biological systems. One of the most widespread Mn oxides is birnessite, which is a semiconducting layered mineral that actively drives Mn photochemical cycling in Nature. The oxygen-evolving centre in biological photosystem II (PSII) is also a Mn-cluster of Mn4CaO5, which transforms into a birnessite-like structure during the photocatalytic oxygen evolution process. This phenomenon draws the potential parallel of Mn-functioned photoreactions between the organic and inorganic world. The Mn photoredox cycling involves both the photo-oxidation of Mn(II) and the photoreductive dissolution of Mn(IV/III) oxides. In Nature, the occurrence of Mn(IV/III) photoreduction is usually accompanied with the oxidative degradation of natural organics. For Mn(II) oxidation into Mn oxides, mechanisms of biological catalysis mediated by microorganisms (such as Pseudomonas putida and Bacillus species) and abiotic photoreactions by semiconducting minerals or reactive oxygen species have both been proposed. In particular, anaerobic Mn(II) photo-oxidation processes have been demonstrated experimentally, which shed light on Mn oxide emergence before atmospheric oxygenation on Earth. This review provides a comprehensive and up-to-date elaboration of Mn oxide photoredox cycling in Nature, and gives brand-new insight into the photochemical properties of semiconducting Mn oxides widespread on the Earth's surface. [ABSTRACT FROM AUTHOR]

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]

Sericite, fine-grained muscovite, is one of the most common altered minerals from hydrothermal ore-forming processes. Due to the similar geochemical property of Au and Cr, chromium sericite usually occurred in gold mineralization. The typomorphic feature of crystal chemistry of chromium sericite from gold deposits are K content in the interlayer indicating degree of hydrothermal alteration, Si content in the tetrahedral sites indicating degree of silicification and Mg, Fe especially Cr contents in the octahedral sites indicating gold mineralization. There are systematic changes in chemical compositions and polymorphism of chromium sericite from the gold deposits hosted in granite in Jiaodong Peninsula. The SiO 2 contents of the chromium sericite are relatively high from 44.92 to 52.22 wt.%; and the K 2 O contents are relatively low from 9.44 to 11.55 wt.%, with K cation in formula unit less than 1. These features reflect strong silicification and hydrothermal alteration. The Cr 2 O 3 contents of the chromium sericite in gold deposits hosted in granite is below 1.92 wt.%, much lower than those hosted in basic to ultrabasic volcanics like Helmo deposit in Canada. Different Cr background abundance and alteration degree are the reasons to explain these phenomenon. Chromium sericite occurring under low Cr background abundance means high alteration degree. Chromium sericite polymorphism includes 1 M , 2 M 1 and 2 M 2 . Different polytypes reflect multiple hydrothermal episodes, which are favorable for large-scale and strong alteration. The chromium sericite is a typomorphic mineral for mineralizing and prospecting of gold deposits in granite similar to Jiaodong Peninsula. [ABSTRACT FROM AUTHOR]

Energy is the key issue of all life activities. The energy source and energy yielding pathway are the key scientific issues of the origin and early evolution of life on Earth. Current researches indicate that the utilization of solar energy in large scale by life was an important breaking point of the early evolution of life on Earth and afterwards life gradually developed and flourished. However, in the widespread biochemical electron transfer of life activities, it is still not clear whether the electron source is sun or how electrons originated from sun. For billions of years, the ubiquitous semiconducting minerals in epigeosphere absorb solar energy, forming photoelectrons and photoholes. In reductive and weak acidic environment of early Earth, when photoholes were easily scavenged by reducing matters, photoelectrons were separated. Photoelectrons could effectively reduce carbon dioxide to organic matters, possibly providing organic matter foundation for the origin of life. Photoelectrons participated in photoelectron transfer chains driven by potential difference and transfer into primitive cells to maintain metabolisms. Semiconducting minerals, by absorbing ultraviolet, also protected primitive cells from being damaged by ultraviolet in the origin of life. Due to the continuous photoelectrons generation in semiconducting minerals and utilization by primitive cells, photoelectrons from semiconducting minerals' photocatalysis played multiple roles in the origin of life on early Earth, such as organic synthesis, cell protection, and energy supply. This mechanism still plays important roles in modern Earth surface systems. [ABSTRACT FROM AUTHOR]

Highlights: [•] Semiconducting mineral photocatalysis to evaluate origin and evolution of life. [•] New model on the use of solar energy by non-phototrophic microorganisms. [•] New insights on energy yielding pathway for life on early Earth. [Copyright &y& Elsevier]

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]

In this work we demonstrated that the active oxygen radicals could be produced by the synergistic interaction between electricigens and natural pyrrhotite. The identification of such an interactive pathway was conducted by using a fuel cell-type design, in which the electricigen-attached carbon felt electrode was used as the anode and the pyrrhotite-coated graphite electrode was used as the corresponding cathode. Current density, polarization and power density curves obtained at different treatments demonstrated the synergistic effects of electricigens and pyrrhotite improved the electrons transfer rate between them. Cyclic voltammetry (CV) analysis showed the reductive peaks of O2/H2O2 at 0.88 V (vs. SCE, saturated calomel electrode) and ionic and structural Fe(III)/Fe(II) at 0.31 V (vs. SCE) and 0 V (vs. SCE), respectively. The electrochemical results indicated the electricigen-assisted pyrrhotite photoelectrochemical reactions gave rise to Fenton's reagents: Fe2+ and H2O2, which underwent a further reaction to generate active oxygen radical ·OH. By using N, N-dimethyl-p-nitrosoaniline discoloration as a model reaction, the ·OH production rate at the pyrrhotite-cathode was found to follow the first-order kinetics. Practical application of the synergistic interaction between the electricigen and natural pyrrhotite to a real old-aged landfill leachate degradation resulted in 78% chemical oxygen demand (COD) removal and 77% decolourization efficiency. The current generation lasted more than 45 days verified the validity of such system in long-term operation. The proposed interactive pathway would be expected as an alternative cost-effective technology for future wastewater treatment. [ABSTRACT FROM AUTHOR]

Geophotocatalysis of natural semiconducting minerals plays key roles in driving redox reactions on the earth's surface. Whether it is related to microbial metabolism remains unknown. This study proposed a novel device, light fuel cell (LFC) to investigate a new aspect of microbe-mineral interactive pathway involved by both microorganisms and semiconducting minerals. When using O2 as the cathodic electron acceptor, the volumetric power density of a LFC with a microbial anode and a visible light-irradiated rutile-cathode was 12.1 W/m3, 1.6 times higher than that obtained in the dark (7.5 W/m3). Electrochemical impedance spectroscopy (EIS) data indicated that the cathodic polarization resistance of the LFC in light was 196 Ω, while that operated in the dark was 2820 Ω. These results manifested the bio-photo-electrochemically interactive pathway between the microorganisms and semiconducting minerals, in which the semiconductor photocatalysis significantly improved the electron transfer efficiency. A thorough investigation was then performed on a LFC to evaluate the parameters such as catholyte pH, electron acceptor concentration, equipment configuration, electrode preparation method and the type of semiconducting minerals that affected its performance. The results reported in this study showed that further improvements of LFCs with the special purpose of minimizing ohmic resistances, maximizing solar to chemical energy conversion efficiency and enhancing the rates of photocatalytic reaction, will finally lead to potential applications of LFCs in wastewater treatment. [ABSTRACT FROM AUTHOR]

Abstract: The photocatalytic disinfection of Escherichia coli K-12 is investigated by the natural sphalerite (NS) under different spectra, wavelengths and intensities of visible light (VL) emitted by light-emitting-diode lamp (LED). The spectrum effect of VL on disinfection efficiency is studied by using white LED, fluorescent tube (FT) and xenon lamp (XE), which indicates that the “discreted peak spectrum” of FT is more effective to inactivate bacteria than “continuous spectrum” of LED and XE. Besides, the photocatalytic disinfection of bacteria is compared under different single spectrum (blue, green, yellow and red color) LEDs. The results show that the most effective wavelength ranges of VL for photocatalytic disinfection with the NS are 440–490 and 570–620nm. Furthermore, a positive relationship is obtained between the disinfection efficiency and the VL intensity. The experiment shows that NS can completely inactivate 107 cfumL−1 E. coli K-12 within 8h irradiation by white LED with the intensity of 200mWcm−2 at pH 8. Moreover, the destruction process of the cell wall and the cell membrane are directly observed by TEM. Finally, no bacterial colony can be detected within a 96h regrowth test of inactivated bacteria, which reveals that the VL-photocatalytic disinfection leads to an irreversible damage to the bacterial cells. [Copyright &y& Elsevier]

Abstract: An investigation aimed at checking the integration of cathodic pyrrhotite Fenton''s reaction with anodic microbial respiration for the enhancement of MFC performance and treatment of a real landfill leachate was carried out. The MFC equipped with a pyrrhotite-coated graphite-cathode generated the maximum power density of 4.2W/m3 that was 133% higher than graphite-cathode. Concomitantly, electrochemical impedance spectroscopy (EIS) showed that the polarization resistance of pyrrhotite-cathode (92Ω) was much lower than the graphite-cathode (1057Ω), indicating that the cathodic overpotential was significantly lowered, probably due to the occurrence of pyrrhotite Fenton''s reaction. The in situ generation of Fenton''s reagents (Fe2+ and H2O2) at the pyrrhotite-cathode was demonstrated by the cyclic voltammetry measurement. Besides, reactive oxygen species produced from the pyrrhotite Fenton''s reaction were detected and demonstrated to be vital to the enhancement of MFC power output. Further, the effectiveness of this system was examined by treating an old-aged landfill leachate. 77% of color and 78% of COD were removed from the original leachate, indicating that the pyrrhotite not only acted as a cost-effective cathodic catalyst for MFCs in power generation, but also extended the practical merits of traditional MFCs towards advanced oxidation of biorefractory pollutants. [Copyright &y& Elsevier]

Abstract: This paper deals with treating high phenol-concentrated wastewater from coal gasification by manganese oxide method. Mixed-phase manganese oxides of manganite and hausmannite were synthesized with industrial MnSO4 and NaOH by air oxidation. The effects of sulfuric acid dosage, reaction time, temperature, manganese oxide grain size and concentration on removal efficiency of total phenols were studied with laboratory bench-scale experiments. The results indicated that the removal process was more effective under the experimental conditions, i.e. acidified media at pH<4 and an excessive amount of fine particles with a long reaction time. Solution pH and manganese oxide concentration were two of the most important factors which should be well regulated to guarantee higher removal rate. The mixture of manganite and hausmannite showed improved activity for removal of total phenols, TOC and CODCr as compared with MnO2 (AR) but similar to cryptomelane and K-birnessite. Most of organic contaminants especially phenol which occupied absolute predominance in initial wastewater were removed to enhance the biodegradability for further biological treatment. This investigation will provide fundamental method for developing a pretreatment method of industrial phenolic wastewater with flexibility, simplicity and high activity. [Copyright &y& Elsevier]

Abstract: Natural sphalerite, which represents a new class of mineral-based catalyst, was characterized and investigated for photo-reduction of an azo dye methyl orange (MO) under visible light. After 2h of visible light irradiation, a complete decolorization of the MO solution was achieved. The degradation rate was related to the pH conditions. Spectra from FT-IR analysis indicate an initial adsorption of MO to sphalerite via its sulfonate group. Further reduction of the adsorbed MO by sphalerite under light irradiation led to the destruction of the azo structure, as indicated by the results from UV–vis, FT-IR and ESI-MS analyses. The visible light-induced photocatalytic reductive activity of natural sphalerite was mainly attributed to the distribution of foreign metal atoms in its crystal lattice, which reduces the intrinsic bandgap of sphalerite and also broadens its spectra responding range. In addition, the high conduction band potential of natural sphalerite may also enhance the photo-reduction of MO. [Copyright &y& Elsevier]

Abstract: A halophilic bacterial strain TM-1 was isolated from the reservoir of the Shengli oil field in East China. Strain TM-1, which was found to be able to degrade crude oils, is a gram-positive non-motile bacterium with a coccus shape that can grow at temperatures of up to 58°C and in 18% NaCl solution. Depending on the culture conditions, the organism may occur in tetrads. In addition, strain TM-1 produced acid from glucose without gas formation and was catalase-negative. Furthermore, strain TM-1 was found to be a facultative aerobe capable of growth under anaerobic conditions. Moreover, it produced butylated hydroxytoluene, 1,2-benzenedicarboxylic acid-bis ester and dibutyl phthalate and could use different organic substrates. Laboratory studies indicated that strain TM-1 affected different heavy oils by degrading various components and by changing the chemical properties of the oils. In addition, growth of the bacterium in heavy oils resulted in the loss of aromatic hydrocarbons, resins and asphaltenes, and enrichment with light hydrocarbons and an overall redistribution of these hydrocarbons. [Copyright &y& Elsevier]

Abstract: Cathodic reduction of hexavalent chromium (Cr(VI)) and simultaneous power generation were successfully achieved in a microbial fuel cell (MFC) containing a novel rutile-coated cathode. The selected rutile was previously characterized to be sensitive to visible light and capable of both non-photo- and photocatalysis. In the MFCs containing rutile-coated cathode, Cr(VI) was rapidly reduced in the cathode chamber in presence and absence of light irradiation; and the rate of Cr(VI) reduction under light irradiation was substantially higher than that in the dark. Under light irradiation, 97% of Cr(VI) (initial concentration 26mg/L) was reduced within 26h, which was 1.6× faster than that in the dark controls in which only background non-photocatalysis occurred. The maximal potential generated under light irradiation was 0.80 vs. 0.55V in the dark controls. These results indicate that photocatalysis at the rutile-coated cathode in the MFCs might have lowered the cathodic overpotential, and enhanced electron transfer from the cathode to Cr(VI) for its reduction. In addition, photoexcited electrons generated during the cathode photocatalysis might also have contributed to the higher Cr(VI) reduction rates when under light irradiation. This work assessed natural rutile as a novel cathodic catalyst for MFCs in power generation; particularly it extended the practical merits of conventional MFCs to cathodic reduction of environmental contaminants such as Cr(VI). [Copyright &y& Elsevier]

Abstract: The modification of nano-fibriform silica by dimethyldichlorosilane was studied by transmission electron microscopy, X-ray powder diffraction, infrared spectroscopy, Raman spectroscopy, physical N2 adsorption techniques, differential thermal and thermogravimetric analysis, scanning electron microscopy, and elemental analyzer. The results show that dimethyl silane derivatives have been successfully covalently grafted on nano-fibriform silica. The polarity of the modified product decreases with the substitution of –OH groups by siloxyl groups. Therefore, the modified product can be easily dispersed in organic solvent and its compatibility with organic molecules is improved. After modification the pore volume decreases and the ductility greatly increases, indicating that the modified product is of a higher strength than before. The study demonstrates that the modified product can be used as an ideal additive to reinforce the strength of organic materials. [Copyright &y& Elsevier]

Abstract: Industrial manganese sulfate from manganese mines has been utilized to synthesize cryptomelane in a simple and feasible route. K-birnessite precursor was prepared by air oxidation of the mixture of MnSO4 and KOH solutions under alkaline conditions, and then transformed to cryptomelane under a heating process. The effects of OH− concentration, airflow rate, liquid reaction temperature, stirring rate, liquid reaction time, washing condition, calcination time, and temperature were investigated. X-ray diffraction (XRD), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HRTEM) revealed that cryptomelane prepared under optimal conditions had a tetragonal symmetry and the particles were mostly in short lathy form with sizes of 20–30 nm. The average pore size and BET surface area of cryptomelane examined by N2 adsorption methods were 24.15 nm and 32.21 m2/g, respectively. X-ray photoelectron spectroscopy (XPS) studies demonstrated that the average oxidation state of manganese in cryptomelane was about 3.9 in comparison with prephase K-birnessite of 3.4. The synthesized cryptomelane sample showed improved catalytic activity for decomposition of hydrogen peroxide as compared with natural cryptomelane, but lower than those synthesized with hydrothermal and sol–gel methods. The results of this investigation will provide fundamental information for developing a large-scale production process for transforming manganese sulfate to cryptomelane. [Copyright &y& Elsevier]

Abstract: Natural sphalerite (ZnS), as a visible light-induced photocatalyst, was characterized by X-ray diffractometry (XRD), electron microprobe analysis (EMPA), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectroscopy (DRS) and zeta-potential analysis. Its photoactivity was tested and compared with pure sphalerite by methyl orange (MO) photoreduction. The isomorphous substitution and other defect states in natural sphalerite altered the band structure and surface properties, resulting in different photoactivity. The results showed 98.74% MO was photoreduced by natural sphalerite after 2h visible light irradiation. Our study indicated that natural sphalerite might be suggested as a new cost-effective and solar light-responsive photocatalyst. [Copyright &y& Elsevier]

Abstract: Natural rutile, which contains substituting metal ions as V5+ and Fe3+, was found to exhibit good photoactivity in visible light. The result showed that 60.59% of methyl orange (MO) was photodegraded after 1h visible light irradiation. Compared with P25 TiO2, the efficiency and mechanism of MO degradation by natural rutile was discussed. The visible light response was due to the substituting ions altering the band structure, and the effective photoactivity was related to the presence of H2O2 and surface hydroxyl groups. Moreover, the substituting metal ions in their high oxidation states could capture photogenerated electrons to suppress electron–hole combination. [Copyright &y& Elsevier]

The objective of this study is to demonstrate the basic characteristics of Bacillus SP3 and evaluate its effect on different crude oils. Strain SP3 is a motile, gram-positive, spore-producing rod that was isolated from a reservoir of the Shengli oil field in East China. The cells of strain SP3 grew at high temperatures up to 58°C at the pH range of 5.5–8.5. Strain SP3 grew facultatively and could use different organic substrates, and produce some metabolites such as 4-hydroxy-4-methyl-2-pentanone, methyl-2-nitrogen benzene and 1, 2-benzenedicarboxylic acid bis ester. Laboratory studies have demonstrated that the strain converted and degraded different components and changed the physical and chemical properties of crude oils. Strain SP3 degraded crude oil and the growth of bacteria on crude oil resulted in loss of aromatic hydrocarbons, resins and asphaltenes. The bioconversion of crude oils would lead to an enrichment in lighter hydrocarbons and an overall redistribution of saturate hydrocarbons. The interactions of microorganisms with crude oils are variable, depending on the microbial species and the chemical compositions of crude oils. [ABSTRACT FROM AUTHOR]

Abstract: Nano-fibriform silica was extracted from chrysotile by the acid-leaching method. The acid-leached residue of chrysotile has been studied by TEM, XRD, FT-IR, and thermal analysis techniques, etc. When the magnesium leaching degree (MLD) is over 90%, the nano-fibriform silica consists of hydrous silicon dioxide (above 90%) with small amount of magnesium trapped inside the Si. The amount of hydroxyl on surface of nano-fibriform silica is 6 unit nm−2. This value is between the values of fumed and precipitated silica. This study shows that nano-fibriform silica is a kind of amorphous matter with a high special surface area (368 m2/g), a high adsorption (330 cm3/g), and a larger pore volume (0.51 cm3/g). The diameter of a single silica fiber is 20–30 nm. The nitrogen adsorption isotherm is similar to Type IV curve. The nano-fibriform silica is one of mesopores materials. [Copyright &y& Elsevier]

A natural ruffle TiO2, which displays photocatalysis on degrading halohydrocarbon pollutants, was reported. The rutile contains up to 1.22% V2O5 (weight percent). Substitutions of Ti by V, as well as Fe, Cu and Zn, result in lattice distortions and defects. Grinding, heating and quenching modify the surface characteristics of rutile, and consequently increase its photoactivity. It is found that the heating and quenching treatments enhance visible-light absorption of ruffle, especially at 1000 and 1100 °C. Ground rutile is effective to degrade tetrachloroethylene and trichloroethylene. While, heating at 1000 °C, and quenching at 1000 and 1100 °C distinctly improve degradation rate of samples. The special properties of the natural rutile have particular capabilities in photocatalytic oxidation, especially in degradation of halohydrocarbons. [ABSTRACT FROM AUTHOR]

The objective of this study is to demonstrate the basic characteristics of thermophilic strain TH-2 and evaluate the effect of strain TH-2 on different crude oils. Strain TH-2 is a non-motile, Gram-negative, oil-degrading thermophile that was isolated from a reservoir of the Shengli oil field in East China. The cells of strain TH-2 were grown at high temperatures up to 85 °C in the neutral to alkaline pH range. Depending on the culture conditions, the organisms occurred as single rods, or as filamentous aggregates. Strain TH-2 was grown chemoorganotrophically and produced volatile fatty acids and such surfactants as 1,2-benzenedicarboxylic acid-bis ester, dibutyl phthalate, and di-n-octyl phthalate. It could use different organic substrates (acetate, d-glucose, fructose, glycerol, maltose, pyruvate, starch, sucrose, and xylose). Laboratory studies have demonstrated that the strain affected different crude oils, converted and degraded various components and changed the physical and chemical properties of crude oils. The strain TH-2 degraded crude oil and growth of the bacterium on crude oil resulted in loss of aromatic hydrocarbons, resins, and asphaltenes. The bioconversion of crude oils leads to an enrichment in lighter hydrocarbons and an overall redistribution of these hydrocarbons. The interactions of microorganisms with crude oils are variable and depend on the microbial species and the chemical compositions of crude oils. Different interactions may influence the efficiency of processes in which single or mixed microbial species are used for the oil treatment and may also suggest possible combinations of biological and chemical technologies. [Copyright &y& Elsevier]

Natural rutile TiO2 shows photocatalysis on degrading trichloroethylene and tetrachloroethylene. In natural rutile, V, Fe, Cu, etc. substitute for Ti, resulting in lattice distortions and defects. We found that rutile, after heating, quenching and electron irradiation, changes its surface characteristics and photoactivity. The quenched rutile has the highest concentrations of adsorbed water and V on its surface, resulting in high photoactivity. For example, quenching at 1273 and 1373 K significantly improved photoactivity of rutile. The heated rutile also increased the concentration of adsorption water on the surface, e.g., rutile heated to 1273 K improved degradation rate of halohydrocarbons. On the contrary, electron irradiation decreased the concentration of adsorbed water on the rutile’s surface, which results in lower degradation rate for trichloroethylene. Therefore, heating and quenching over 1237 K improve the photocatalytic efficiency of the natural V-bearing rutile on degrading halohydrocarbons. The XRD spectra of the rutile samples showed that heating, quenching and electron irradiation did not result in formation of new phases or phase transitions. [Copyright &y& Elsevier]

Reports on the identification of the naturally outcropping cryptomelane by examining the physical, chemical and structural features of the Xiangtan manganese deposit supergene oxide manganese ore. Cell parameters of the cryptomelane; Implication of the discovery on the application of octahedral molecular sieve of natural cryptomelane.

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]

• Cobalt is enriched (up to 962 ppm) in the paleo-karstic bauxite deposit at Yunfeng. • Cobalt is positively correlated with sulfur. • Cobalt occurs mainly as Co-bearing pyrites and Co-rich sulfides/sulfoarsenides. Cobalt can be enriched in a variety of different geologic settings, while it is mainly produced as a by-product of sediment-hosted stratiform Cu deposits and magmatic Ni-Cu deposits associated with mafic and ultramafic rocks. In this study, we report elevated Co concentrations in a paleo-karstic bauxite deposit at Yunfeng, Guizhou Province. Whole-rock chemical analyses indicate that Co is concentrated in carbonaceous ferruginous clay layers (167–962 ppm, average 383 ppm, n = 5) and siderite layers (47–439 ppm, average 213 ppm, n = 7) within the bauxite deposit. The positive correlation between Co and S, together with petrographic and EPMA analyses, suggests that Co occurs primarily as Co-rich/bearing sulfides/sulfoarsenides rather than cobaltiferous oxides/hydroxides as in most lateritic Ni-Co deposits. Many of the Co concentrations measured in this study are higher than the minimum grade (300 ppm) or cut-off grade (200 ppm) for economic exploitation of Co from sulfides or arsenides. Basing on these results, we put forward the scientific significance of Co enrichment in paleo-karstic environments and the potential importance of Co resources (as by-products of aluminum production) in bauxite deposits. [ABSTRACT FROM AUTHOR]

Presents a study on the one-step disposal of Cr(VI) by natural pyrrhotite which takes the role of reductant for Cr(VI) and precipitant Cr(III) simultaneously. Experimental methods; Results of the study; Conclusion.

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]

Based on the most active hydrosphere on the earth, the interplay between adjacent semiconducting minerals and electrochemically active microorganisms was scientifically researched in the marine euphotic zone of the Yellow Sea, China. Fe and Ti were found in suspended minerals by ICP-MS and EDS, probing the element composition of suspended minerals from macro to micro. Moreover, SR-XRD and Raman indicated that semiconducting minerals of iron and titanium metal oxide in situ such as anatase, rutile, brookite, and goethite consisted in suspended minerals, notably, which retained prominent photo-response property and distinct photoelectric catalytic potential under visible light. 16S rRNA gene systematically emerged that electrochemically active microorganisms, such as Pseudomonas and Paraclostridium, were pivotal in the solution and preponderant on the electrode respectively after a period of cultivation. Whereupon a dual-chamber reactor was established to probe into the mechanism of redox reaction and electron transfer process between microorganisms and suspended minerals. Importantly, compared with a graphite electrode, the maximum power density of the reaction was 2.78 times with the increase of suspended minerals as the electron acceptor under dark conditions, as well as 236.53% promotion with visible light. Experiments gave an index that semiconducting minerals could interact with electroactive microorganisms, effectively promoting the process of extracellular electron transfer in the euphotic zone, which will make a foundation for further research on electron energy transfer based on the interactions of semiconducting minerals and electrochemically active microorganisms, as well as the regulation mechanism of elements cycling. [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]

The article discusses a study that was conducted to differentiate between the effects of porosity and key oxide content on the electrical conductivity of low-porosity rocks in Dayingezhuang Gold Deposit, Shandong Province, Northeast China. Topics discussed include measurement of electrical conductivity of different types of granite, relatively high porosity of granite on which the influence of resistivity was estimated and correlation between resistivity and chemical composition of rock.

The article focuses on a study that investigates geological characteristics of major iron (Fe)-copper (Cu) polymetallic deposits in Qimantag Metallogenic Belt, Eastern Kunlun Area, China. Topics include the Hutouya Cu-Fe-lead (Pb)-zinc (Zn) deposit which is related to a porphyritic monzonite granite, the Galinge Fe-Pb-Zn deposit which represents the most important Fe deposit in the Qimantag area, and the Kendekeke Fe-cobalt (Co)-bismuth (Bi)-silver (Ag) deposit.

The article focuses on a study that investigates formation and importance of chromium (Cr)-bearing sericite in granite-hosted gold deposits. The study shows that high alteration intensity leads to formation of Cr-bearing micas in granite environments, followed by gold mineralization. Also the study mentions that with strong alteration, chromium precipitate in mica phase and gold in pyrite or quartz phase.

The article discusses a research of rare earth elements (REE) and trace element characteristics of quartz from Dayingezhuang gold deposit, Jiaodong Peninsular, China. Topics discussed include association of the most of the gold deposit in north China craton to Mesozoic era's crust thining events, a table related to a study that shows the detected limits of element in quartz, and estimation of temperature of quartz from Dayingezhuang gold deposit.

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]

An introduction is presented in which the editors discuss various reports within the issue on topics including microbial diversity, implications of microbial cell surfaces' metal sorption in bioremediation, and light fuel cell (LFC) interactions.

Abstract Anode electron transfer efficiency is one of the main bottlenecks in determining the performance of microbial fuel cells (MFCs). Here, we report for the first time a novel design of a silicon solar cell equipped MFC with one-dimensional TiO 2 /Fe 2 O 3 photoanode and conventional bioanode to overcome the constraints of using traditional anodes. The novel MFC has the maximum power density of 638.3 mW m−2, which is nearly 7.6 times higher than that of general MFCs (84.2 mW m−2). In addition, the novel MFC achieves 90.9% removal of hexavalent chromium Cr(VI) with concentration of 50 ppm within 13.5 h, and this rate is significantly high at 3.67 g m−3 h−1. Efficient microbial oxidation and photoelectrocatalysis are realized after constructing the SSC with double-anode MFC, thereafter leading to enhanced electron transfer to the external circuit. In addition, the electrons are driven by the built-in electric field in silicon solar cell, in which system barriers are resolved at the same time. Power output and Cr(VI) reduction efficiency are both remarkably enhanced. Such a novel MFC strategy provides new directions for designing new systems that can increase the efficiency of MFCs by utilizing solar energy economically, which further suggest great potential in environmental remediation. Graphical abstract Image 1 Highlights • A SSC coupled double anodes novel MFC constructed for the first time. • Increment of electrons overcame the bottlenecks in traditional MFC. • Decreased transfer barrier realized after utilizing solar energy by SSC. • The maximum power density was 7.6 times higher than that in general MFC. • Such system exhibited high reduction rate (3.67 g m−3 h−1) for Cr(VI) wastewater. [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]

Using a mineralogy method to reflect climate evolution is a new approach to research Cenozoic environmental progression of the Qaidam Basin. In this paper, we present the chemical composition and crystallographic parameter of atacamite, nantokite, and tenorite in cryptocrystalline aggregates from the Kaerqueka copper deposit of Qimantag metallogenic belt by means of electron microprobe and in-situ X-ray diffraction analyses. Atacamite and nantokite occur in an intimate intergrowth as the secondary precipitation of chalcopyrite and bornite filling in the interstitial space of andradite in the Kaerqueka copper deposit, with an average composition of Cl: 12.38 wt.% Cu: 63.76 wt.% O: 21.46 wt.% X-ray microdiffraction shows that the intergrowth contains nantokite with a cubic unit cell a=5.403(2) Å and atacamite with an orthorhombic unit cell a=6.030(3), b=6.883(2), c=9.114(1) Å XRD quantitative calculation shows that the nanometric aggregate contains 36.07 wt.% tenorite, 18.41 wt.% atacamite, and 45.52 wt.% nantokite. The presence of nantokite and atacamite requires saline solutions for their formation and hyper-arid climate conditions for their preservation. Combined with the data of salt lakes and the pollen sequence of western China, we suggest that during the uplift of the Tibetan Plateau and the retreat of the Paratethys, saline water was forced to the surface through a basal fracture zone. In the hyper-arid climate of the Qaidam Basin, the recharge of groundwater by direct precipitation is negligible, and groundwater is derived from inflow from the salt lakes. Thus, atacamite is preserved. In addition, spertiniite in the edge and fractures of atacamite and nantokite may represent wetter climate after the formation of atacamite and nantokite. [ABSTRACT FROM AUTHOR]

Bacillus mucilaginosus is one of the common soil bacteria and is widely used as a microbial fertilizer to release potassium from K-rich soil minerals. But few researchers have discussed possible effects that the bacteria may have on montmorillonite. This study investigated the effect of B. mucilaginosus strain on the capability of montmorillonite to retain water/cations. After 20 days of interaction with B. mucilaginosus D4B1, the expansion ratios of montmorillonite samples decreased from 83.2% to 76.7%, and the cation exchange capacities (CEC) decreased from 80.8 mmol/100 g to 67.8 mmol/100 g, suggesting the durative interaction with the bacteria may reduce the capabilities of incorporating water molecules and nutrient into the interlayer space of montmorillonite. Morphological changes of discrete layers and etch pits were observed with scanning electron microscope (SEM). In the synchrotron radiation X-ray diffraction (SR-XRD) profiles, the full-width at half maximum (FWHM) of 001 reflection increased to 0.24 nm as compared to the abiotic sample (0.19 nm), indicating a decreased structural order in bacteria-treated montmorillonite. Also, a new band at 1540 cm − 1 assigned to asymmetric stretching vibrations of carboxylate was detected by micro fourier-transform infrared spectroscopy (FTIR) in bacteria-treated samples, suggesting the alteration in the mineral structure of montmorillonite was possibly triggered by the organic acids produced by bacteria. Moreover, in bacteria involved dispersion, a significant decrease of the pH value was coupled with a consecutive increase of total protein concentration, indicating the continuous activities of the bacteria during 20 days of interaction. Above all, the decreased water-holding or cations-exchange capacity of montmorillonite was related to the partial alteration in the mineral structure of montmorillonite by B. mucilaginosus D4B1. Such a durable interaction on structural alteration of soil clays would have detrimental impact on long-term sustainability of soil resources. [ABSTRACT FROM AUTHOR]