High Sulfide Research Articles

Confining nano FeSb2S4 in carbon nanotube/oxide graphene 3D porous networks for high-capacity sodium ion battery anode

Sodium ion batteries (SIBs) are promising alternative for lithium ion batteries (LIBs) due to the abundant reserve of Na compared to Li. Although the three-dimensional (3D) thick electrodes for LIBs have been widely studied, corresponding researches are seldom reported for SIBs anode. Herein, a high theoretical capacity binary metal sulfide (FeSb2S4) on reduced oxide graphene (rGO) was used as active component to prepare the light-weight, current collector-free, 3D thick anode (FeSb2S4/CNTs/rGO/GO) for SIBs. The as-prepared 3D discs can keep its integral structure under the pressure from the battery assembly, as the interconnected macropores are formed during the freeze-drying process. The macropores can also act as the electrolyte channel to facilitate the mass transfer, thus enabling the low Na+ diffusion resistance when the thickness of the electrodes increased from 150 µm to 540 µm. Based on the capacity calculation of the active components (FeSb2S4/rGO), the as-prepared 3D discs with a thickness of 540 µm can achieve a mass capacity of 391.7 mAh g–1 under 0.1 A g–1, corresponding to 3.11 mAh cm–2 of area-capacity and 57.64 mAh cm–3 of volume-capacity, respectively.

Physicochemical constraints on indium-, tin-, germanium-, gallium-, gold-, and tellurium-bearing mineralizations in the Pefka and St Philippos polymetallic vein- and breccia-type deposits, Greece

The Pefka Cu-Au-Te-In-Se and nearby St Philippos Pb-Zn-Bi-Sn-Ge-Ga-In vein- and breccia-type deposits in western Thrace, Greece, display strong similarities, but also differences in terms of mineralization style, ore mineralogy, and chemistry, and host rock compositions. The Pefka mineralization consists of two crosscutting vein systems with high sulfidation (HS)- and intermediate-sulfidation (IS) assemblages hosted by andesitic lavas and is unusually enriched in In (up to 700 ppm), Te (>1000 ppm), Se (>100 ppm), and Cu (>1 wt%). The main In-carriers are roquesite (CuInS2) and In-bearing “tennantite-(Cu)” and Cu-rich “tennantite-(In)” which contains up to 6.5 wt% In, substituting into the C site. Roquesite is associated with enargite and arsenosulvanite/colusite, as part of the HS assemblage at Pefka. Selenium-bearing galena and a large suite of tellurides including calaverite, sylvanite, petzite, hessite, kostovite, empressite, tellurantimony, and coloradoite, in addition to native tellurium, account for the marked tellurium and selenium enrichment in the ores from Pefka. Tellurides and native gold at Pefka accompany the precipitation of Te-bearing minerals of the tetrahedrite group, such as “stibiogoldfieldite” and “arsenogoldfieldite”, and Cu-excess varieties of tetrahedrite and tennantite. However, the bulk of telluride deposition is associated with normal, fully substituted tetrahedrite-tennantite varieties.The St Philippos deposit is associated with a brecciated fault zone hosted by Eocene sandstones and Oligocene quartz-feldspar porphyry dikes. It is enriched in a large suite of incompatible elements, including Bi (>2000 ppm), Sn (>100 ppm), U (up to 200 ppm), Pb (>1 wt%), Zn (>1 wt%), Mo (up to 62 ppm), Ge (>100 ppm), Ga (up to 466 ppm) and In (up to 222 ppm), contrasting with the element suite defining the nearby Pefka deposit. The main carrier of In, Ga, and Ge is sphalerite (and wurtzite) with In-rich zones in sphalerite containing up to 6.1. wt% In. Germanium and Ga in sphalerite reach concentrations of up to 0.27 and 0.32 wt%, respectively. Sphalerite from the St Philippos deposit is extremely Fe-poor (<0.04 wt%), and is associated with an unusual suite of Sn-bearing sulfosalts (kësterite-stannite, Mn-bearing kësterite, unnamed Cu2MnSnS4), and enargite, marking an early HS event. Kësterite also hosts indium (up to 0.6 wt% In). Mn-bearing varieties of tennantite host inclusions of minor tellurides (e.g., hessite, altaite, and tsumoite) and formed later in the paragenetic sequence under transitional HS-IS and IS conditions.Both deposits are characterized by early high-temperature (>300 °C) and HS fluid conditions, followed by IS assemblages as temperatures waned. Rhyolitic oxidized magmas are considered to be the sources of metals in the St Philippos deposit; however, their anomalous W, Sn, U, and Bi contents suggest a contamination by crustal rocks. The Cu-Au-Te signature of the Pefka deposit is compatible with a genetic relationship to less fractionated andesitic magmas, although a possible contribution of In from rhyolitic magmas could explain the high In contents of the ore. However, other factors, as for example different metal-deposition mechanisms resulting in metal zonation around causative porphyry centers at depth, may also account for the observed metal endowment in these two deposits. The Sn-Te-In-(Ge-Ga) element association at Pefka and St Philippos is unusual in that it has been previously reported from only a few other places in the world (e.g., Capillitas deposit, Argentina, and the Kawazu deposit, Japan). We conclude based on this exotic mineralization-style that the northeastern part of Greece represents an area of great potential for the exploitation of critical metals and metalloids.

TREATMENT OF TRADITIONAL ETHANOL FERMENTATION WASTE WITH ELECTROLYSIS METHOD FOR DECREASING COD AND SULFIDE

Ethanol is produced from molasses by a fermentation process. In Bekonang, ethanol manufacturingby a home-scale industry so the waste just thrown away in free water then pollution occurs both in rivers and in paddy fields. Ethanol waste has very high chemical oxygen demand (COD) and contain high sulfide. Electrolysis that use for reduce leves COD dan Sulfide with electricity as main source for direct current flowing electricity (dc) to the anode and cathode. Electrolysis time 10, 15, 20, 25 and 30 minutes and voltage variation 5, 10 and 15 volt. Based on data obtained in the test COD obtained optimum levels of 284.5 mg/L from the initial content of 586 mg/L , at a time variation of 30 minutes and voltage 15 volt. The sulfide test obtained optimum levels of 0.0661 mg/L from the initial content of 0.305 mg/L, at time variation of 25 minutes and a voltage of 15 volt.

Pollutant-Removing Biofilter Strains Associated with High Ammonia and Hydrogen Sulfide Removal Rate in a Livestock Wastewater Treatment Facility

This study analyzed the microbial community metagenomically to determine the cause of the functionality of a livestock wastewater treatment facility that can effectively remove pollutants, such as ammonia and hydrogen sulfide. Illumina MiSeq sequencing was used in analyzing the composition and structure of the microbial community, and the 16S rRNA gene was used. Through Illumina MiSeq sequencing, information such as diversity indicators as well as the composition and structure of microbial communities present in the livestock wastewater treatment facility were obtained, and differences between microbial communities present in the investigated samples were compared. The number of reads, operational taxonomic units, and species richness were lower in influent sample (NLF), where the wastewater enters, than in effluent sample (NL), in which treated wastewater is found. This difference was greater in June 2019 than in January 2020, and the removal rates of ammonia (86.93%) and hydrogen sulfide (99.72%) were also higher in June 2019. In both areas, the community composition was similar in January 2020, whereas the influent sample (NLF) and effluent sample (NL) areas in June 2019 were dominated by Proteobacteria (76.23%) and Firmicutes (67.13%), respectively. Oleiphilaceae (40.89%) and Thioalkalibacteraceae (12.91%), which are related to ammonia and hydrogen sulfide removal, respectively, were identified in influent sample (NLF) in June 2019. They were more abundant in June 2019 than in January 2020. Therefore, the functionality of the livestock wastewater treatment facility was affected by characteristics, including the composition of the microbial community. Compared to Illumina MiSeq sequencing, fewer species were isolated and identified in both areas using culture-based methods, suggesting Illumina MiSeq sequencing as a powerful tool to determine the relevance of microbial communities for pollutant removal.

Geology, mineralogy, and sulfur isotopes of the Mowana copper deposit, Matsitama Schist Belt, NE Botswana

AbstractThe Mowana hydrothermal Cu deposit is located within the Matsitama–Motloutse Complex in the southwestern part of the Zimbabwe Craton in the northeastern part of Botswana. This study aims to document the characteristics of the mineralization based on geology, quartz textures, ore mineralogy, chlorite geothermometry, and sulfur isotope analyses. The deposit is hosted by the NNE‐striking and nearly vertically dipping (70–80°) Bushman Lineament, within the graphitic schist lenses in the carbonaceous and argillaceous metasedimentary rocks of the Neoarchean to Paleoproterozoic Matsitama Sedimentary Group. The hydrothermal alteration of the host rocks is characterized by silicification, chloritization, epidotization, sericitization, hematite, and calcite alteration. Based on the alteration mineral assemblage, the main mineralization stage is attributed to near neutral pH fluids at temperatures between ~200 and ~340°C. The base metal mineralization of the Mowana deposit was evolved in at least two vein types. The first mineralization type, represented by the quartz+calcite±K‐feldspar veins and breccias is characterized by the precipitation of principal chalcopyrite with pyrite, minor bornite, and trace amounts of galena. The Type 2 veins represented by the quartz+calcite±fluorite veins, host appreciable amounts of galena. The supergene mineralization widely distributed in the shallow levels of the deposit is manifested by the significant presence of chalcocite, bornite, covellite, anglesite, malachite, and hematite. The temperature obtained from the chlorite geothermometry in the Type 1 veins indicate that the mineralization associated with chlorite alteration formed at a temperature ranging from 340 to 400°C. The ore mineral assemblage: pyrite, bornite, and chalcopyrite, paired with the chlorite geothermometry data indicate that the Type 1 veins formed at an intemediate to high sulfidation state. Sulfur isotopic ratios determined on the sulfides indicate the magmatic S and/or leaching of the host metasedimentary rocks and closed system reduction of seawater sulfate as the sources of S.

Young's modulus of thin SmS films measured by nanoindentation and laser acoustic wave

High quality phase pure samarium sulphide (SmS) thin films with low surface roughness were prepared by electron beam evaporation using a samarium metal source in an H2S atmosphere. SmS shows a strong piezoresistive response due to a phase transition between a semiconducting and metallic state, which can be employed in piezo-electronic devices and stress sensing. Measurement of fundamental mechanical properties such as Young's modulus is thus a major objective to assess the elastic behaviour of SmS under external stress. Nanoindentation was used to measure the elastic modulus of thin semiconducting films with nominal thickness of 100 nm, 200 nm and 400 nm on silicon substrate at different loads. The indentation results were fitted to a modified King's model to exclude the effect of the substrate, giving Young's moduli of the films in the range of 79–82 GPa, consistent with measurements with a Laser Surface Acoustic Wave system (LAwave) and results from literature.

Mechanisms of passivation and chloride-induced corrosion of mild steel in sulfide-containing alkaline solutions

The pore fluid within many concretes is highly alkaline and rich in reduced sulfur species, but the influence of such alkaline-sulfide solutions on the surface film formed on steel reinforcement is poorly understood. This study investigates the critical role of HS− in defining mild steel passivation chemistry. The surface film formed on the steel in alkaline-sulfide solutions contains Fe(OH)2 and Fe–S complexes, and the critical chloride concentration to induce corrosion increases at high sulfide concentration. However, this behavior is dependent on the duration of exposure of the steel to the electrolyte, and the nature of the sulfidic surface layer.

Risk assessment of toxic hydrogen sulfide concentrations on swine farms

Hydrogen sulfide is a highly toxic gas, causing many lethal accidents in farming environment. Until now, the understanding of the interactive impact of different variables on hydrogen sulfide concentrations on swine farms has been limited. The risk of high hydrogen sulfide concentrations has not yet been assessed comprehensively. The main goal of this study is to identify and investigate the variables, which significantly influence hydrogen sulfide concentrations, and to assess the risk of exposure to toxic hydrogen sulfide concentrations on swine farms. A generalized linear model was built to show the intertwining impact of different variables, and, on the basis of this model, sensitivity analysis, stress tests and Monte Carlo simulations were conducted to thoroughly assess the risk of exposure to dangerous hydrogen sulfide concentrations. Use of generalized linear models and risk assessment tools is a novelty in this context. The model results show that the most significant variables are the location of sample origin, manure disturbance, pig age, weight and diet. If hydrogen sulfide is measured outside a barn, the concentration is up to 47-times lower than inside a barn. Hydrogen sulfide concentration increases by a factor of 7 if manure is pumped during the observation period. Operations with growing pigs have the highest expected hydrogen sulfide concentrations in comparison to other pig age groups. Risk assessment analysis additionally reveals that certain combinations of variable values result in lethal hydrogen sulfide concentrations, and that the likelihood of such scenarios can reach 0.69%.

The influence of sulphate on the treatment of azo dye‐containing wastewater in an anaerobic‐microaerobic compartmentalized fixed‐bed bioreactor

AbstractA fixed bed reactor (FBR) comprised of an anaerobic zone (AZ) coupled to a micro‐aerated zone (MAZ) was used for the biological treatment of synthetic textile wastewater. The azo dye in the textile effluent is expected to be reduced to aromatic amines (decolouration) in AZ followed by biological degradation of the aromatic amines due to oxygen exposure in MAZ. We focused on assessing the effect of sulphate, a common component of textile wastewaters, on the degradation of the tetra‐azo dye Direct Black 22 (DB22). The influence of sulphide, a product of sulphate biological reduction, on the removal of aromatic amines, toxic by‐products of DB22 degradation, was also analyzed. The AZ and the MAZ were filled with expanded clay balls and polyurethane foam, respectively. The chemical oxygen demand and sulphate ratio (COD/SO4−2) in the feed started at 4.8 ± 0.2 and was later changed to 0.8 ± 0.1 by increasing the sulphate content. This change consequently increased DB22 removal efficiency from 38 ± 11% to 72 ± 6% in AZ and from 56 ± 7% to 75 ± 7% at MAZ, but also resulted in high sulphide concentration and reduced redox potential (ORP) at the MAZ inlet. However, the change negatively affected the degradation of aromatic amines in the MAZ. Aromatic amines were removed only at redox potential values higher than −228 mV and biogenic sulphide concentrations lower than 44 mg HS−/L.

Performance of Sulfide-Driven Fuel Cell Aerated by Venturi Tube Ejector

Hydrogen sulfide is frequently met in natural waters, like mineral springs, but mostly it is found in marine water with low renewal rate. The Black Sea has extremely high hydrogen sulfide content. It can be utilized in different ways, but the most promising one is direct conversion into electricity. This result can be attained by a sulfide-driven fuel cell (SDFC), converting sulfide to sulfate thus releasing electric energy up to 24 GJ/t. One of the most important problems is the mass transfer limitation on oxygen transfer in the cathode space of the fuel cell. This problem can be solved using a gas diffusion electrode or highly efficient saturation by oxygen in an ejector of the Venturi tube type. This work presents experimental data in laboratory-scale SDFC for sulfide conversion into sulfate, sulfite and polysulfide releasing different amounts of electric energy. Two types of aeration are tested: direct air blow and Venturi-tube ejector. Besides pure graphite, two catalysts, i.e., cobalt spinel and zirconia-doped graphite were tested as anodes. Experiments were carried out at initial sulfide concentrations from 50 to 300 mg/L. Sulfate, sulfite and thiosulfate ions were detected in the outlet solutions from the fuel cell. The electrochemical results show good agreement with the chemical analyses. Most of the results show attained high efficiencies of the fuel cell, i.e., up to 80%. The practical applications of this method can be extended for other purposes, like treatment of polluted water together with utilization as energy.

An alternative electron-donor and highly thermo-assisted strategy for solar-driven water splitting redox chemistry towards efficient hydrogen production plus effective wastewater treatment

An alternative technology has been sought for highly efficient and sustainable hydrogen production and wastewater treatment worldwide. This paper is focused on the intersection of solar energy, wastewater treatment and hydrogen production. The solar thermo-assisted and electron-donor alternative strategy was conducted for water-splitting redox chemistry to target highly efficient hydrogen production and effective wastewater treatment. The thermodynamic calculation displays that the solar thermal application and shuttle sulfide electron donor alternative are favorable for the hydrogen production and sulfide-to-sulfate oxidation by the falling trend in the potential (from 1.5V to 0.6V). The curves revealed that high current peaks in the low potential range were dominated by the thermal-assisted process and the alternative of the oxidation half-reaction. The experiments illustrated that solar thermal utilization and sulfide donors were dominant factors for the high efficiencies. Under the outdoor sunlight, the high hydrogen production rate and sulfide conversion efficiency were experimentally achieved at rates of 0.25 mL/h H2 and 93% sulfide-to-sulfate oxidation, reasonably more than that of the direct electrochemical water splitting to hydrogen (nearly no evolution) under the same applied bias (＜1.2V). The system realized that one sustainable technology conducts simultaneously both highly efficient hydrogen production and highly effective water treatment.

Impact of methane seepage dynamics on the abundance of benthic foraminifera in gas hydrate bearing sediments: New insights from the South China Sea

The stable isotopic composition of benthic foraminifera tests is widely used to trace past methane release events. However, gaps in our knowledge on the ecology of benthic foraminifera at methane seeps impede the utility of test composition as proxy of methane emission histories and the influence of redox zonation on the local fauna. Here, we use sediment geochemistry and foraminiferal assemblages of a seep area of the South China Sea to reveal that seepage duration and intensity affect benthic foraminifera. Taxa tolerating eutrophic conditions like Uvigerina thrive at times of reduced seepage when aerobic methanotrophy is favored. In contrast, intense methane seepage leads to high sulfide levels, and a positioning of the sulfate-methane transition zone close to the seafloor. At these times, bottom waters may become oxygen depleted and benthic foraminifera will decline. This study provides (1) the means to understand how seepage dynamics control the distribution of benthic foraminifera and (2) new constraints on the use of foraminifera as paleoceanographic proxies, including possible mechanisms of mass mortality in the geological past.

CH3SH and H2S Sensing Properties of V2O5/WO3/TiO2 Gas Sensor

Resistive-type semiconductor-based gas sensors were fabricated for the detection of methyl mercaptan and hydrogen sulfide. To fabricate these sensors, V2O5/WO3/TiO2 (VWT) particles were deposited on interdigitated Pt electrodes. The vanadium oxide content of the utilized VWT was 1.5, 3, or 10 wt.%. The structural properties of the VWT particles were investigated by X-ray diffraction and scanning electron microscopy analyses. The resistance of the VWT gas sensor decreased with increasing methyl mercaptan and hydrogen sulfide gas concentrations in the range of 50 to 500 ppb. The VWT gas sensor with 3 wt.% vanadium oxide showed high methyl mercaptan and hydrogen sulfide responses and good gas selectivity against hydrogen at 300 °C.

Lead electrowinning from methane sulfonic acid

Currently lead is produced by conventional pyrometallurgical smelting route which is suitable for high grade sulfide ores and concentrates. The hydrometallurgical recovery of lead through methane sulfonic acid (MSA) medium provides a “green” lead production route with a potentially lower cost. Electrowinning is the most feasible and economic way to produce lead metal in the hydrometallurgical route. The current challenge for lead electrowinning from methane sulfonate solution is to produce a smooth and dense lead deposit without the significant formation of PbO2 on an anode. The use of proper leveling agents is the key for production of high-quality electrolytic lead. Various additives were first investigated using a Hull cell and then by electrowinning. Aloe has the best leveling effect. The combination of aloe and glue can produce smooth and dense lead deposits. Several DSA anodes have been evaluated and some of them have an oxygen evolution overpotential low enough to prevent the formation of PbO2. Although the current efficiency of PbO2 on graphite can be reduced to 3.6% in the presence of H3PO4, graphite anodes were not stable and degraded after extended time of electrowinning. With the use of aloe and glue as smoothing agents and suitable DSA anodes, smooth and dense lead deposits can be produced without the formation of PbO2 on the anodes. Lead can be depleted to 3 g/L from the electrolyte at a high efficiency. The presence of 5 g/L Fe in the electrolyte resulted in a decrease of 2.1% in the lead current efficiency. Chloride at its level of 50 mg/L or less practically has no effect on lead electrowinning.

Rapid sulfur cycling in sediments from the Peruvian oxygen minimum zone featuring simultaneous sulfate reduction and sulfide oxidation

AbstractBacterial sulfate reduction (SR) is often determined by radiotracer techniques using 35S‐labeled sulfate. In environments featuring simultaneous sulfide oxidation, SR can be underestimated due to re‐oxidation of 35S‐sulfide. Recycling of 35S‐tracer is expected to be high in sediment with low concentrations of pore‐water sulfide and high abundance of giant filamentous sulfur‐oxidizing bacteria (GFSOB). Here, we applied a sulfide‐spiking method, originally developed for water samples, to sediments along a shelf‐slope transect (72, 128, 243, 752 m water depth) traversing the Peruvian oxygen minimum zone. Sediment spiked with unlabeled sulfide prior to 35S‐sulfate injection to prevent radiotracer recycling was compared to unspiked sediment. At stations characterized by low natural sulfide and abundant GFSOB (128 and 243 m), the method revealed 1–3 times higher SR rates in spiked sediment. Spiking had no effect on SR in sediment with high natural sulfide despite presence of GFSOB (72 m). Bioturbated sediment devoid of GFSOB (752 m) showed elevated SR in spiked samples, likely from artificial introduction of sulfidic conditions. Sulfide oxidation rates at the 128 and 243 m station, derived from the difference in SR between spiked and unspiked sediment, approximated rates of dissimilatory nitrate reduction to ammonium by GFSOB. Gross SR contributed considerably to benthic dissolved inorganic carbon fluxes at the three shallowest station, confirming that SR is an important process for benthic carbon respirations within the oxygen minimum zone. We recommend to further explore the spiking method to capture SR in sediment featuring low sulfide concentrations and high sulfur cycling by GFSOB.

Technology Focus: Intelligent Operations (May 2021)

The last year has seen people in many sectors unexpectedly confronting a new challenge—working remotely. Even before this, our industry has been trying to operate fields remotely (either partially or fully) and make operations smarter and more automated. Key drivers are to improve safety in operations, maximize production, and make operations more efficient. These efforts have been enabled by the rapidly changing technology landscape—in sophisticated acquisition and analysis of data and increased connectivity (from both fiber-optic and cellular networks). It also has been accelerated by the push across the industry to digitalize. We now acquire, process, and analyze much more detailed operations data and use the analysis to actively control wells and operations. This feature highlights recently presented papers that cover the following topics. How Digital Transformation Has Progressed. Paper OTC 30794 discusses similar efforts in other sectors, including marine/ship building and auto manufacturing. Paper SPE 200728 discusses use of a digital twin to improve operational efficiency in a mature brownfield setting (Brage Field in the Norwegian North Sea). Paper OTC 30488 describes extensible and scalable remote monitoring and control using a digital decision assistant. How Technology Has Enabled Data Acquisition and Analysis From Relatively New Sources [e.g., Distributed Temperature Sensing (DTS) or Distributed Acoustic Sensing]. Paper SPE 200826 describes seven DTS applications from around the world that monitor well integrity, stimulation, and injection profiles and identify gas, water, or sand production. Paper OTC 30442 and other papers from the Bokor field in Malaysia describe DTS data from fiber-optic cable behind casing in wells with smart completions. Papers IPTC 19574 and SPE 202349 show how pressure telemetry can enable wireless control of completions. The Path to Fully Remotely Operated Fields. Paper SPE 203461 discusses the design and execution of digitalization and remote operations in a new development area with high hydrogen sulfide (the Mender satellite field in the UAE). Paper SPE 202667 describes the applications for multiple autonomous robots controlled remotely. Digital transformation of work flows and operations clearly is happening across the industry and adding significant value. The next frontier on the digital transformation and Industry 4.0 journey might be to achieve step-change increases in oil and gas recovery factors. Recommended additional reading at OnePetro: www.onepetro.org. SPE 200728 - The Digitalization Journey of the Brage Digital Twin by Peter Kronberger, Wintershall, et al. OTC 30442 - Innovative Solution for IWAG Injection Monitoring Using Fiber-Optic Cable Cemented Behind Casing in an Intelligent Well: A First in Malaysia by Nur Faizah P. Mosar, Schlumberger, et al. SPE 202667 - Operations Room: A Key Component for Upscaling Robotic Solutions on Site by Jean-Michel Munoz, Total, et al. OTC 30488 - Machine-Learning-Enabled Digital Decision Assistant for Remote Operations by Vitor Alves da Cruz Mazzi, Intelie, et al. IPTC 19574 - Research and Application of Downhole Remote Wireless Control Technology Based on Gas Pressure Wave in Tubing by Mingge He, China National Petroleum Corporation, et al. SPE 202349 - Pressure Wave Downhole Communication Technique for Smart Zonal Water Injection by Quanbin Wang, China National Petroleum Corporation, et al.

Co-disposal of lignite fly ash and coal mine waste rock for neutralisation of AMD

Waste rocks (WRs) from a lignite-producing coalfield and fly ash (FA) produced from the same lignite have been investigated in this study with a primary objective to determine the potential for co-disposal of WRs and FA to reduce the environmental contamination. Mixing WRs with FA and covering WRs with FA have been investigated. Particle size effect caused ≤2 mm particles to produce low pH (~2) and metal-laden leachates, indicating higher sulphide minerals’ reactivity compared to larger particles (≤10 mm, pH ~ 4). Co-disposal of FA as mixture showed an instantaneous effect, resulting in higher pH (~3–6) and better leachate quality. However, acidity produced by secondary mineralisation caused stabilisation of pH at around 4.5–5. In contrast, the pH of the leachates from the cover method gradually increased from strongly acidic (pH ~ 2) to mildly acidic (pH ~ 4–5) and circumneutral (pH ~ 7) along with a decrease in EC and elemental leaching. Gradually increasing pH can be attributed to the cover effect, which reduces the oxygen diffusion, thus sulphide oxidation. FA cover achieved the pH necessary for secondary mineralisation during the leaching experiment. The co-disposal of FA as cover and/or mixture possesses the potential for neutralisation and/or slowing down AMD and improving leachate quality.

Earth-like Habitable Environments in the Subsurface of Mars.

In Earth's deep continental subsurface, where groundwaters are often isolated for >106 to 109 years, energy released by radionuclides within rock produces oxidants and reductants that drive metabolisms of non-photosynthetic microorganisms. Similar processes could support past and present life in the martian subsurface. Sulfate-reducing microorganisms are common in Earth's deep subsurface, often using hydrogen derived directly from radiolysis of pore water and sulfate derived from oxidation of rock-matrix-hosted sulfides by radiolytically derived oxidants. Radiolysis thus produces redox energy to support a deep biosphere in groundwaters isolated from surface substrate input for millions to billions of years on Earth. Here, we demonstrate that radiolysis by itself could produce sufficient redox energy to sustain a habitable environment in the subsurface of present-day Mars, one in which Earth-like microorganisms could survive wherever groundwater exists. We show that the source localities for many martian meteorites are capable of producing sufficient redox nutrients to sustain up to millions of sulfate-reducing microbial cells per kilogram rock via radiolysis alone, comparable to cell densities observed in many regions of Earth's deep subsurface. Additionally, we calculate variability in supportable sulfate-reducing cell densities between the martian meteorite source regions. Our results demonstrate that martian subsurface groundwaters, where present, would largely be habitable for sulfate-reducing bacteria from a redox energy perspective via radiolysis alone. We present evidence for crustal regions that could support especially high cell densities, including zones with high sulfide concentrations, which could be targeted by future subsurface exploration missions.

Electron Acceptor Availability Shapes Anaerobically Methane Oxidizing Archaea (ANME) Communities in South Georgia Sediments.

Anaerobic methane oxidizing archaea (ANME) mediate anaerobic oxidation of methane (AOM) in marine sediments and are therefore important for controlling atmospheric methane concentrations in the water column and ultimately the atmosphere. Numerous previous studies have revealed that AOM is coupled to the reduction of different electron acceptors such as sulfate, nitrate/nitrite or Fe(III)/Mn(IV). However, the influence of electron acceptor availability on the in situ ANME community composition in sediments remains largely unknown. Here, we investigated the electron acceptor availability and compared the microbial in situ communities of three methane-rich locations offshore the sub-Antarctic island South Georgia, by Illumina sequencing and qPCR of mcrA genes. The methanic zone (MZ) sediments of Royal Trough and Church Trough comprised high sulfide concentrations of up to 4 and 19 mM, respectively. In contrast, those of the Cumberland Bay fjord accounted for relatively high concentrations of dissolved iron (up to 186 μM). Whereas the ANME community in the sulfidic sites Church Trough and Royal Trough mainly comprised members of the ANME-1 clade, the order-level clade “ANME-1-related” (Lever and Teske, 2015) was most abundant in the iron-rich site in Cumberland Bay fjord, indicating that the availability of electron acceptors has a strong selective effect on the ANME community. This study shows that potential electron acceptors for methane oxidation may serve as environmental filters to select for the ANME community composition and adds to a better understanding of the global importance of AOM.

Modeling of Thermal-Hydrological-Chemical (THC) Processes During Waste Rock Weathering Under Permafrost Conditions

The oxidation of sulfide minerals such as pyrite present in waste rock results in elevated sulfate, enhanced metal loadings and in many cases low pH conditions. Recently, many mines have opened in remote areas, including regions subject to permafrost conditions. In these regions, freeze-thaw cycles and the possible development of permafrost in mine waste add to the complexity of weathering processes, drainage volumes and mass loadings. To assess weathering in these waste rock piles, the reactive transport code MIN3P-HPC has been enhanced by implementing constitutive relationships related to freeze-thaw cycles that control flow patterns, solute transport, generation and transport of heat, as well as geochemical reactions and their rates. Simulations of a hypothetical pyrite-rich waste rock pile placed onto natural permafrost were conducted under reference climate conditions. Additionally, the effect of a warming climate was also studied through a sensitivity analysis. The simulation results indicate a potentially strong coupled effect of sulfide mineral weathering rates and a warming climate on the evolution and persistence of permafrost within waste rock piles and the release of acidic drainage. For relatively low sulfide mineral oxidation rates, the simulations indicate that permafrost can develop within waste rock piles, even under warming climate conditions. However, the results for low reactivity also show that mass loadings can increase by &amp;gt;50% in response to a slight warming of climate (3°C), relative to reference climate conditions. For the chosen reference reaction rates, permafrost develops under reference climate conditions in the simulated waste rock pile; however, permafrost cannot be maintained for a marginally warmer climate, leading to internal heating of the pile and substantially increased production of acidic drainage (&amp;gt;550%). For high reaction rates, the simulations suggest that internal heating takes place irrespective of climate conditions. Evaluation of thermal covers indicates that significant reductions of mass loadings can be achieved for piles with low and reference reactivity (91–99% in comparison to uncovered piles), but also suggest that thermal covers can be ineffective for piles with high sulfide content and reactivity. Together, these simulations provide insights into the complex interactions controlling waste rock weathering in cold-region climates.