High Sulfide Concentrations Research Articles

The effect of anaerobic remineralization of the seagrass Halophila stipulacea on porewater biogeochemistry in the Gulf of Aqaba

IntroductionSeagrasses form oxidizing microenvironments around their roots, creating complex and strong redox gradients, thus affecting the rates of microbial carbon mineralization in their surrounding sediments. Since seagrasses are continuously being lost worldwide, a deeper understanding of the changes that occur within different seagrass sediments following the disappearance of the plants is of ecological and global importance.MethodsWe conducted a slurry experiment with sediments that have different characteristics from the northern tip of Gulf of Aqaba; the different sediments included different compartments of the tropical seagrass Halophila stipulacea (old and young leaves, rhizomes, or roots). We measured the changes over time in dissolved inorganic carbon (DIC), alkalinity, ferrous iron (Fe2+), hydrogen sulfide (H2S), sulfate (SO42-), and sulphur isotope ratios in sulfate within water. These measurements were used to calculate the rate of remineralization of each seagrass compartment, allowing us to predict the potential effects of the disappearance of different H. stipulacea compartments on key microbial processes in the surrounding environment.ResultsWe show that H. stipulacea’s rhizomes had the fastest decomposition rates, followed by the young leaves, roots, and old leaves (which also indicates the preservation potential of old leaves).DiscussionHigh concentrations of hydrogen sulfide were detected only in the slurries containing rhizomes and young leaves. High sulfide concentrations can lead to seagrass mortality and cause a positive feedback loop where the loss of seagrass due to sulfide generates further sulfide accumulation. This positive feedback loop can also be further reinforced by the loss of burrowing fauna in the sediment. This emphasizes the importance of understanding the extent of different pathways of seagrass disappearance on the surrounding environment and other geochemical feedbacks.

Performance of electro-Fenton process for the treatment of synthetic sulphidic spent caustic waste stream generated from petroleum refineries

Sulphidic spent caustic (SSC) is an alkaline waste stream which is generated during caustic scrubbing of liquefied petroleum gas and ethylene products. Due to presence of high concentrations of sulphides and phenols, the waste stream requires proper treatment before mixing with the low strength wastewater streams produced from other refinery operations. Electrochemical process is an emerging treatment method that can work efficiently at ambient conditions. The present study reports performance of electro-Fenton (EF) process for the treatment of synthetic SSC wastewater (sulphides = 10 g L−1, phenol = 2 g L−1 and pH = 12.9). The EF runs were carried out for 2 h duration in a reactor equipped with iron electrodes. The effects of H2O2 dose (0.26–1.3 M), current density (1–20 mA cm−2), pH (4.5–12.9) and stirring speed (100–1000 rpm) were investigated on removal of pollutants. The H2O2 was rapidly consumed in initial 30 min during which the significant fraction of the pollutants was degraded or removed. The optimum conditions for EF process were found to be as follows: pH = 4.5, H2O2 dose = 1.05 M, current density = 5 mA cm−2 and stirring speed = 500 rpm. At these conditions, the maximum sulphide and phenol removals from the wastewater were 98% and 91%, respectively. The results will be helpful to the wastewater treatment plant operators worldwide dealing with high concentrations of such pollutants.

High risk concrete blocks from County Donegal: The geology of defective aggregate and the wider implications

Since 2019, geologists at Petrolab have tested concrete block samples from over 1800 properties in County Donegal and observed deterioration patterns based on the aggregate types used within those concrete blocks. Across these properties more than 25 aggregate types have been used within concrete block, with seven distinct types considered high risk when assessed against relevant standards. With respect to those considered high risk, elevated free mica and elevated reactive sulphides (predominantly pyrrhotite) contents appear to play a critical role, particularly in phyllite aggregates commonly found in defective blockwork. The particular concentration of both of these mineral groups is considered the main cause of the rapid degradation often observed with this aggregate type. Other high-risk aggregates have lower amounts of one or both of these mineral groups, but they are still present in concentrations that are cause for concern and associated in some instances with damaged property.These findings have important implications. Firstly, with two mineral groups to define risk, the extent of risk can be split depending on the concentrations of the different minerals with potentially different remedial pathways followed in each instance. Aggregates with high concentrations of both free mica and sulphides (predominantly pyrrhotite) will pose the highest risk, likely requiring the most significant intervention in the long-term, while aggregates with only free mica and low sulphide content will be lower risk. In support of this, none of the properties tested to date, where only free mica risk is present within the concrete samples, have gone on to display the most serious degradation category. This, coupled with the evidence of internal sulphate attack present within the most high-risk pyrrhotite-bearing aggregate, is further evidence of the importance of internal sulphate attack in the highest risk aggregates. For all seven aggregates of concern the authors provide general recommendations for remedial measures, or further research based on the findings of this study.Secondly, the risk window for affected properties appears wider than initially believed. It spans for at least two decades with a significant window encompassing structures built between 1995 and 2010. The currently recorded latest occurrence is 2015, but it is not clear from the current data that this latest occurrence reflects the last use of defective concrete block due to the inherent latency period between building construction and the time for degradation to set-in. Consequently, a long-term testing regime is necessary to provide confidence in property conveyancing within County Donegal for properties built within, and since, the defined risk window.

GSH-Triggered/Photothermal-Enhanced H2S Signaling Molecule Release for Gas Therapy.

Traditional treatment methods for tumors are inefficient and have severe side effects. At present, new therapeutic methods such as phototherapy, chemodynamic therapy, and gasodynamic therapy have been innovatively developed. High concentrations of hydrogen sulfide (H2S) gas exhibit cancer-suppressive effects. Herein, a Prussian blue-loaded tetra-sulfide modified dendritic mesoporous organosilica (PB@DMOS) was rationally constructed with glutathione (GSH)-triggered/photothermal-enhanced H2S signaling molecule release properties for gas therapy. The as-synthesized nanoplatform confined PB nanoparticles in the mesoporous structure of organosilica silica due to electrostatic adsorption. In the case of a GSH overexpressed tumor microenvironment, H2S gas was controllably released. And the temperature increases due to the photothermal effects of PB nanoparticles, further enhancing H2S release. At the same time, PB nanoparticles with excellent hydrogen peroxide catalytic performance also amplified the efficiency of tumor therapy. Thus, a collective nanoplatform with gas therapy/photothermal therapy/catalytic therapy functionalities shows potential promise in terms of efficient tumor therapy.

Mitigation of Mining Effects on the Environment

Editor’s note: The aim of the Geology and Mining series is to introduce early career professionals and students to various aspects of mineral exploration, development, and mining in order to share the experiences and insight of each author on the myriad of topics involved with the mineral industry and the ways in which geoscientists contribute to each. Abstract All human activities produce waste and affect our environment, including the solids and water involved during mining and metallurgical operations. The nature and characteristics of these impacts vary considerably depending on many factors, including the geology of the operation, type of mining and processing implemented, sensitivity of the local environment to the operation, and proximity to human settlements or sensitive environmental settings. Environmental challenges associated with mineral extraction and processing include impacts to land, air, water, soil, flora, fauna, and socioeconomic fabric. Mines can generate large land disturbances and can also result in sterilization of land through deposition of barren, nonreactive rock piles (termed waste) during production and after operation. Other mine waste piles can be chemically reactive and interact with precipitation and runoff, leading to metal and sulfate release into surface and ground water. Impacts on soils may result directly from weathering of mine waste or through interaction with affected waters. Interaction with the atmosphere may occur, with release of aerosol or airborne metals or minerals affecting air quality. In addition, the release of gases containing CO2, SOx, and NOx and halide gases can lead to acid rain or general lowering of air quality. These challenges can be predicted, quantified, and understood during the mine design and operations processes by application of geologic knowledge, geochemical and hydrogeological data, and mining experience. Such understanding can then identify appropriate solutions, including changes to operations through sequenced mining to reduce exposure of material with high metal or sulfide content; partial or full backfill of mine excavations; use of cemented waste backfill; modifications to water discharge designs; and treatment of water prior to discharge. A critical aspect of addressing environmental challenges and reducing environmental impact involves engagement with communities, government, and society. The confidence of society is essential to the delivery of long-term sustainable plans.

Evaluating the effects of pH and temperature on sulphate-reducing bacteria and modelling of their effects in stirred bioreactors

ABSTRACT Sulphate (SO4) abundance in the earth’s crust contributes largely to industrial wastewater contamination lowering the pH, which exuberates the dissolution of metals forming acidic drainages. Biological sulphate reduction as a remediation process can be affected by factors such as pH, temperature and high sulphide concentrations. In this study, sulphate-reducing bacterial community enriched from mine wastewaters was applied in semi-automated bioreactors to assess the effects of these factors on microbial sulphate reduction capacities. Low pH (3.5) and temperature (10°C) were observed to promote the toxicity of sulphur-reduced species on the consortium while mesophilic temperature (25°C) and near neutral pH (6.2) were observed to induce optimum SO4 reduction attaining a maximum of 95% SO4 reduction. Obtained SO4 reduction dynamics data was then applied in formulating a unique non-competitive inhibition equation that models biogeochemical events during SO4 reduction under varied pH and temperature conditions and predicts the efficacy of a bioremediation system.

Substrate-dependent strategies to mitigate sulfate inhibition on microbial reductive dechlorination of polychlorinated biphenyls

Sulfate widely co-exists with polychlorinated biphenyls (PCBs) at various concentrations in the subsurface environment. Previous studies have suggested that sulfate often hampers microbial degradation of aliphatic chlorinated solvents such as chloroethenes. However, the impact of sulfate on microbial reductive dechlorination of aromatic PCBs and the underlying mechanisms have received limited attention. Likewise, strategies to mitigate such inhibition remain scarce. Here we found that the mechanisms and mitigation strategies of sulfate inhibition on PCB dechlorination were substrate-dependent. Under electron donor-limiting conditions, even a low concentration of sulfate (2 mM) resulted in a decreased PCB dechlorination rate by 88.7% in a co-culture comprising Dehalococcoides mccartyi CG1 and the sulfate-reducing bacterium Desulfovibrio desulfuricans F1, an inhibition which was attributed to the competition for electron donor between sulfate reduction and PCB dechlorination. As expected, re-amendment of 5 mM lactate effectively re-initiated PCB dechlorination. However, in the presence of a higher concentration of sulfate (5 mM), the PCB dechlorination rate in the co-culture was 77.7% lower than in the control, even with excessive electron donor supply. This inhibition was linked to high concentration of sulfide (∼5 mM) produced from sulfate reduction, as suggested by high availability of electron donor, recovery of dechlorination activity after removal of sulfide, and negligible influence of sulfate on PCB dechlorination in the axenic culture of D. mccartyi CG1. Indeed, sulfide (>5 mM) was found to directly suppress expression of PCB-dechlorinating reductive dehalogenase gene. The highest transcriptional level of pcbA1 was 2.9 ± 0.3 transcripts·cell−1 in the presence of ∼5 mM sulfide, which was increased to 37.4 ± 5.0 transcripts·cell−1 when sulfide was removed. Under this scenario, introduction of ferrous salts (5 mM) efficiently alleviated sulfide inhibition on PCB dechlorination. Interestingly, the augmentation of methanogens in the co-culture was also effective in mitigating sulfide inhibition on PCB dechlorination, offering a new approach to protect Dehalococcoides under sulfide stress. Collectively, these findings deepen our understanding of the influence of sulfate on microbial reductive dechlorination of PCBs and contribute to developing appropriate strategies based on geochemical conditions to alleviate sulfate inhibition during bioremediation of PCB-contaminated sites.

Failure analysis of corroded heat exchanger CuNi tubes from a geothermal plant

This study examined the premature failure of cupronickel (CuNi10Fe) tubes in a shell-and-tube heat exchanger after five months of service. An investigation to identify the root cause of the tube burst was carried out using macroscopic and microscopic inspection, chemical analysis, and mechanical analysis. The optical microscopy (OM) and scanning electron microscopy (SEM) evaluation revealed crack propagation characterized by pits and inclusions at the tube surface. This was due to the diffusion of hydrogen ions into the material from the hydrogen sulfide (H2S) rich geothermal environment. Furthermore, high tensile residual stresses of 172 MPa were recorded in the failed tube, leading to stress cracking in hydrogen-containing material. Additionally, the high sulfide content in corroded water and condensate samples suggests that the leading cause of tube rupture was through hydrogen embrittlement and sulfide stress cracking mechanism in the presence of hydrogen sulfide. Therefore, the use of laser cladding to protect tubes using functionally graded materials is recommended to mitigate degradation in aggressive environments, through careful material selection and additional water treatment to eliminate the contaminants.

Effect of alkaline leaching of phosphogypsum on sulfate reduction activity and bacterial community composition using different sources of anaerobic microbial inoculum

Phosphogypsum (PG), a by-product of the phosphate industry, is high in sulfate, (SO42−), which makes it an excellent substrate for sulfate-reducing bacteria (SRB) to produce hydrogen sulfide. This work aimed to optimize SO42− leaching from PG to achieve a high biological reduction of SO42− and generate high sulfide concentrations for subsequent use in the biological recovery of elemental sulfur. Five SRB consortia were isolated and enriched from: IS (Industrial sludges), MS (Marine sediments), WC (Winogradsky column), SNV (petroleum industry sediments) and PG (stored Phosphogypsum). The five consortia showed reduction activity when using PG leachate (with water) as source of SO42− and lactate, acetate, or glucose as the electron donor. The highest reduction rate (81.5 %) was registered using lactate and the IS consortium (81.5 %) followed by MS (79 %) and PG (71 %). To enhance the concentration of leached SO42− from PG for future utilization with the isolated consortia, PG was treated with NaOH solutions (2 % and 5 %). SO42− release of 97 % was achieved with a 5 % concentration and the resulting leachate was further diluted to target a SO42− concentration of 12.4 g·L−1 for utilization with the isolated consortia. Compared to water leachate, a significantly higher reduction rate was registered (2 g·L−1 of SO42) using the IS consortium, demonstrating limited inhibition effect of sulfide− concentration on SRB functionalities. Moreover, metagenomic analysis of the consortia revealed that using PG as a source of SO42− increased the abundance of Deltaproteobacteria, including known SRB like Desulfovibrio, Desulfomicrobium, and Desulfosporosinus, as well as novel SRB genera (Cupidesulfovibrio, Desulfocurvus, Desulfococcus) that showed, for the first time, significant potential as novel sulfate-reducers using PG as a SO42− source.

Dissolution Potential of Elemental Mercury in the Presence of Bisulfide and Implications for Mobilization.

Liquid elemental mercury (Hg0L) pollution can remain in soils for decades and, over time, will undergo corrosion, a process in which the droplet surface oxidizes soil constituents to form more reactive phases, such as mercury oxide (HgO). While these reactive coatings may enhance Hg migration in the subsurface, little is known about the transformation potential of corroded Hg0L in the presence of reduced inorganic sulfur species to form sparingly soluble HgS particles, a process that enables the long-term sequestration of mercury in soils and generally reduces its mobility and bioavailability. In this study, we investigated the dissolution of corroded Hg0L in the presence of sulfide by quantifying rates of aqueous Hg release from corroded Hg0L droplets under different sulfide concentrations (expressed as the S:Hg molar ratio). For droplets corroded in ambient air, no differences in soluble Hg release were observed among all sulfide exposure levels (S:Hg mole ratios ranging from 10-4 to 10). However, for droplets oxidized in the presence of a more reactive oxidant (hydrogen peroxide, H2O2), we observed a 10- to 25-fold increase in dissolved Hg when the oxidized droplets were exposed to low sulfide concentrations (S:Hg ratios from 10-4 to 10-1) relative to droplets exposed to high sulfide concentrations. These results suggest two critical factors that dictate the release of soluble Hg from Hg0L in the presence of sulfide: the extent of surface corrosion of the Hg0L droplet and sufficient sulfide concentration for the formation of HgS solids. The mobilization of Hg0L in porous media, therefore, largely depends on aging conditions in the subsurface and chemical reactivity at the Hg0L droplet interface.

Study on the performance of anodic desulfurization and cathodic denitrification coupled electricity generation in microbial fuel cell

Sulfide autotrophic denitrification microbial fuel cell was set up and the two reaction processes of desulfurization in anode chamber and denitrification in cathode chamber were separated to study nitrogen and sulfur removal effect and electricity generation capacity. The results showed that simultaneous desulfurization in anode chamber and nitrate removal in cathode chamber was feasible. The removal load of sulfide and nitrate almost increased with the increase of their concentrations under the experiment operation conditions. Higher sulfide concentration in a certain range was beneficial to generate electricity. The change of nitrate concentration in the cathode chamber had less effect on sulfide removal efficiency and electricity production performance of microbial fuel cell, which was mainly depended on the influent sulfide concentration in the anode chamber. The maximum sulfide and nitrate removal loads were 0.36 kg∙m−3∙d−1 and 0.07 kg∙m−3∙d−1 respectively, with a maximum power density of 144.03 mW∙m−3. The external resistance affected the quantities and varieties of reaction products in the anode chamber and the cathode chamber. Lower external resistance was beneficial to improve the efficiency of nitrate removal in the cathode chamber. The microbial community structure of the anode chamber in sulfide autotrophic denitrification MFC was similar to that of sulfide autotrophic denitrification SBR, whose main functional bacterial genera were Clostridium, Thiobacillus and Rhodobacteraceae. However, the functional bacteria in the cathode chamber were completely different, whose dominant bacteria included Thiobacillus, Bacillus, Flavobacteriaceae, Acinetobacter, Sphingomonas and Paracoccus. The research results provided a new idea and method for the sulfur- and nitrogen-containing wastewater treatment.

The Use of Construction Waste to Remediate a Thermally Active Spoil Heap

This article presents the results of experimental research on the possible use of construction and demolition waste (CDW) to improve the properties of unburnt tailings originating from the thermally active spoil heap in Heřmanice (Ostrava, Czech Republic). Mining activity anywhere in the world generally entails a lot of negative impacts on the environment, which are of a long-term nature. One of the most pressing challenges in the remediation of the consequences of mining activity is the thermal activity of spoil heaps associated with the high acidity of the tailings. Active acidity (pH/H2O), exchangeable acidity (pH/CaCl2), hydrolytic acidity (Ha), and elemental composition of tailings and CDW have been monitored. Based on an acidity study, it has been proven that compared to burnt tailings (pH/H2O = 8.4, pH/CaCl2 = 8.9 and Ha = 1.4 mmol kg−1), unburnt tailings show acidic properties (pH/H2O = 3.7, pH/CaCl2 = 3.6 and Ha = 205 mmol kg−1). The bioavailability of two selected potentially toxic elements (PTEs), namely Al and Fe, was examined based on the elemental composition. BCR sequential extraction analysis was used to determine their bioavailability. It has been proven that mixing CDW with tailings has a positive effect on the pH value, which has a positive effect on the further development of the entire site. The increase in the pH value is provably dependent on the amount of construction waste added, so it can be said that the increasing amount of construction waste will result in improved parameters of the burnt tailings. The results of the BCR analysis show that aluminum from the tailings will be released both from the reducible and oxidisable fractions, where it will be mainly bound to sulphides. The relatively high concentration of Fe in the oxidisable fraction (2002 mg Fe kg−1) suggests that Fe is bound to sulphides in the tailings, and it is due to the high residual pyrite and sulphide content in the dumped material, as expected. This work has found no limits where CDW no longer positively affects the acidity of unburnt tailings. For practical application, however, it is important that the mixture of CDW and tailings is properly mixed and then used for remediation.

Identification of Porphyry Deposit Based On Time Domain Induced Polarization Data Analysis in The Papua Region

Papua is one of the islands in Indonesia which has an abundance of economic metal mineralization in Indonesia. The types of mineralized deposits on the island of Papua are porphyry, skarn and epithermal, where porphyry deposits are identified in the study area, which were identified early by geological conditions. The geophysical approach is carried out using Time Domain Induced Polarization data analysis, TDIP measurements are carried out on an area of 2.24km2, with a total of 3 line oriented southeast-northwest along 3 km. Based on TDIP data analysis, there’s low resistivity anomaly correlates with high chargeability which is interpreted as a Potassic body at an elevation of 500m, while above it there are Serisitic-Clay-Chlorite and Serisitic-Clay-Pyrite alterations with high metal sulfide content up to 1100m elevation.

Exogenous Hydrogen Sulfide Induces A375 Melanoma Cell Apoptosis Through Overactivation of the Unfolded Protein Response.

Melanomas are highly malignant and rapidly develop drug resistance due to dysregulated apoptosis. Therefore, pro-apoptotic agents could be effective for the management of melanoma. Hydrogen sulfide is ubiquitous in the body, and exogenous hydrogen sulfide has been reported to show inhibitory and pro-apoptotic effects on cancer cells. However, whether high concentrations of exogenous hydrogen sulfide have pro-apoptotic effects on melanoma and its mechanisms remain unknown. Hence, this study aimed to explore the pro-apoptotic effects and mechanisms of exogenous hydrogen sulfide on the A375 melanoma cell line treated with a hydrogen sulfide donor (NaHS). The cell proliferation test, flow cytometric analysis, Hoechst 33258 staining, and Western blotting of B-cell lymphoma 2 and cleaved caspase-3 were used to explore the pro-apoptotic effects of hydrogen sulfide on A375 cells. The transcriptional profile of NaHS-treated A375 cells was further explored via high-throughput sequencing. Western blotting of phosphorylated inositol-requiring enzyme 1α (p-IRE1α), phosphorylated protein kinase R-like ER kinase (p-PERK), phosphorylated eukaryotic translation initiation factor 2α (p-eIF2α), C/EBP homologous protein, glucose-regulating protein 78, IRE1α, PERK, and eIF2α was performed to verify the changes in the transcriptional profile. NaHS inhibited A375 melanoma cell proliferation and induced apoptosis. The endoplasmic reticulum stress unfolded protein response and apoptosis-associated gene expression was upregulated in NaHS-treated A375 melanoma cells. The overactivation of the unfolded protein response and increase in endoplasmic reticulum stress was verified at the protein level. Treatment with NaHS increased endoplasmic reticulum stress, which triggered the overactivation of the unfolded protein response and ultimately lead to melanoma cell apoptosis. The pro-apoptotic effect of NaHS suggests that it can be explored as a potential therapeutic agent in melanoma.

Engineering Approach Uses Underbalanced Coiled-Tubing Drilling

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 210978, “Novel Engineering Approach Using Underbalanced Coiled-Tubing Drilling Solutions for Tight Sour Gas Carbonate,” by Mohamed Osama Abd El Meguid, Ayman El Shahat, and Ali Sulaiman Bin Sumaida, ADNOC, et al. The paper has not been peer reviewed. _ Because of declining reservoir pressures in some of its onshore gas carbonate fields, the operator initiated a three-well underbalanced coiled-tubing drilling (UBCTD) campaign in its onshore Asab and Bab fields, with two wells to be drilled in Asab and one in Bab. Because of the high hydrogen sulfide (H2S) content, a closed-loop system—the first one successfully implemented in the Middle East, according to the authors—was implemented. The complete paper discusses the design and planning involved in the drilling of these three wells, the operational challenges encountered, and mitigations used. Introduction One of the operator’s main objectives was to increase production while safely maintaining or minimizing operating costs. One method of achieving these goals is the use of coiled tubing (CT) to drill formations in underbalanced mode. The Asab and Bab fields are southwest of Abu Dhabi. Both fields have high H2S and CO2 content, with a bottomhole temperature of approximately 260–270°F. The candidate wells were drilled conventionally until the top of the reservoir section; then, the UBCTD package was moved to drill the reservoir section in underbalanced mode. The typical well completions, from top to bottom, include the following: - 5.5-in. tubing - 4.5-in. tubing - 7-in. liner - 100 ft of 6-in. openhole Project Objectives Because of safety and logistical constraints, the project would use a closed-loop system and recirculate the drilling fluid, thus avoiding high water consumption. Also, the system needed to be designed to safely handle H2S in return fluids. UBCTD using a closed-loop system has been performed elsewhere but not in a high-H2S and high-CO2 environment. Trajectory Design and Tubing Forces Trajectory design is an important part of drilling operations; reservoir targets given by geologists and reservoir engineers must be met. To expose more drilling footage in producing formations and to increase overall productivity, the geologists provide formation-top coordinates so that the drilling engineer knows how to proceed as drilling progresses through the reservoir subunits. When the well trajectory was designed in the discussed case, the CT engineer input planned well surveys into software so that the CT forces could be analyzed. Because these predrilled wells had never had CT interventions, the friction coefficient was unknown and the outcome of the software could have been very different from that observed while drilling. Friction coefficients from other conventional CT operations within the UAE, as well as those from other CT drilling operations in the region, were reviewed and then used for analysis. With the lowest friction coefficient of 0.3 for open hole, the target drilling length could not be achieved. Project planning required a solution to enable the lateral to meet the proposed objectives.

Enhanced sulfide removal by gas stripping in a novel reactor for anaerobic wastewater treatment.

Removal of sulfide by gas stripping using biogas produced in an internal phase-separated reactor (IPSR) was evaluated during anaerobic treatment. The IPSR consisted of upper and lower segments with a gas-liquid partitioning (GLP) valve between the sections. Wastewater was fed to the upper segment in the first stage and then to the lower segment in the second stage. The GLP valve separated the liquid phase from the gaseous phase and supplied biogas from the lower segment to the upper segment. The IPSR and a control reactor were fed with synthetic wastewater and operated in parallel under an organic loading rate of 12 kg COD/(m3 day) at 35 °C. The sulfide concentration increased to 400-600 mg S/L, which is above the previously reported 50% inhibition level for methanogenic activity. The IPSR showed higher H2S removal performance than the control reactor and removed approximately twice the H2S as the control reactor at 400 mg S/L, indicating that it can be used for the stable treatment of wastewater containing high concentrations of sulfide.

A new extremophile ostracod crustacean from the Movile Cave sulfidic chemoautotrophic ecosystem in Romania

Sulfidic cave ecosystems are remarkable evolutionary hotspots that have witnessed adaptive radiation of their fauna represented by extremophile species having particular traits. Ostracods, a very old group of crustaceans, exhibit specific morphological and ecophysiological features that enable them to thrive in groundwater sulfidic environments. Herein, we report a peculiar new ostracod species Pseudocandonamovilaensis sp. nov. thriving in the chemoautotrophic sulfidic groundwater ecosystem of Movile Cave (Romania). The new species displays a set of homoplastic features specific for unrelated stygobitic species, e.g., triangular carapace in lateral view with reduced postero-dorsal part and simplification of limb chaetotaxy (i.e., loss of some claws and reduction of secondary male sex characteristics), driven by a convergent or parallel evolution during or after colonization of the groundwater realm. P.movilaensis sp. nov. thrives exclusively in sulfidic meso-thermal waters (21 °C) with high concentrations of sulphides, methane, and ammonium. Based on the geometric morphometrics-based study of the carapace shape and molecular phylogenetic analyses based on the COI marker (mtDNA), we discuss the phylogenetic relationship and evolutionary implication for the new species to thrive in groundwater sulfidic groundwater environments.

Origin and hydrochemical evolution of confined groundwater in Shanghai, China

Confined groundwater is an indispensable resource for the urban security of Shanghai, China, where multi-layer aquifer structures and human activities create a complex groundwater environment. An understanding of the hydrochemical characteristics and evolutionary mechanisms of groundwater is necessary for its protection and effective utilization and will be explored in this study. A total of 87 groundwater samples were collected from five confined aquifers. Hydrochemistry analysis methods such as Durov diagram, Gibbs model and Saturation index were used to determine the origin and hydrochemical evolution of the confined groundwater. The results show that the samples have two different origins, marine–continental and continental, which have different hydrochemical characteristics. Cl− content of 7.5 meq L−1 was used as a demarcation index for the two origins. The groundwater with a marine–continental-origin is dominated by ancient seawater from which Na+ and Cl− are derived, whereas Ca2+, Mg2+, and HCO3− are derived mainly from carbonate dissolution. Groundwater with a continental-origin is dominated by the effects of water–rock interaction, where major ions are derived mainly from silicate weathering and carbonate dissolution. In both types of groundwater, SO42− is mainly derived from insoluble sulfides that are present in low quantities, whereas SO42− in the few samples with high insoluble sulfide content is derived from human activities. Cation exchange is another controlling factor regarding the hydrochemical composition of groundwater, and water from the two origins have different reaction modes as follows: reverse cation exchange is dominant in marine–continental groundwater, whereas positive cation exchange is more common in continental groundwater. Over the past century, saline water has been flowing into the groundwater funnel region due to human activities, which has resulted in changes in the hydrochemical composition. The recent influx of fresh groundwater and artificial recharge has caused groundwater salinization and mineral re-dissolution.

Utilization of rice straw as an inhibitor of strength deterioration of sulfide-rich cemented paste backfill

Cemented paste backfill (CPB) has been a practical approach for mining waste management, underground goaf treatment, and green mining. Strength deterioration because of high sulfide content (SC) is a severe challenge for sulfide-rich CPB. To investigate the influence of rice straw (RS) on the strength of sulfide-rich CPB, RS was utilized as an inhibitor of strength deterioration. RS dosage (RSD), RS length (RSL), and sulfide content (SC) were chosen as the factors, and two stages of the experiment were carried out. It was found that high SC produced pores, cracks, and loose microstructure of CPB, resulting in the strength deterioration of sulfide-rich CPB. The 90-day uniaxial compressive strength (90 d-UCS) was the maximum of the UCS of sulfide-rich CPB. The hydration products and microstructural characteristics observed by XRD and scanning electron microscopy (SEM) illustrated that RS has the effect of bridging and water retention. Accordingly, adding RS improved the long-term strength of sulfide-rich CPB. The optimal RSD, RSL, and SC for 90 d-UCS of sulfide-rich CPB were obtained through the response surface methodology approach. The optimal conditions within the experimental range of this study for maximum 90 d-UCS of CPB with high SC (17 wt%) were RSD of 0.032 wt% and RSL of 0.28 cm, producing a 90 d-UCS of 5.14 MPa.

Investigations into hydrogen sulfide-induced suppression of neuronal activity in vivo and calcium dysregulation in vitro.

Acute exposure to high concentrations of hydrogen sulfide (H2S) leads to sudden death and, if survived, lingering neurological disorders. Clinical signs include seizures, loss of consciousness, and dyspnea. The proximate mechanisms underlying H2S-induced acute toxicity and death have not been clearly elucidated. We investigated electrocerebral, cardiac and respiratory activity during H2S exposure using electroencephalogram (EEG), electrocardiogram (EKG) and plethysmography. H2S suppressed electrocerebral activity and disrupted breathing. Cardiac activity was comparatively less affected. To test whether Ca2+ dysregulation contributes to H2S-induced EEG suppression, we developed an in vitro real-time rapid throughput assay measuring patterns of spontaneous synchronized Ca2+ oscillations in cultured primary cortical neuronal networks loaded with the indicator Fluo-4 using the fluorescent imaging plate reader (FLIPR-Tetra®). Sulfide >5 ppm dysregulated synchronous calcium oscillation (SCO) patterns in a dose-dependent manner. Inhibitors of NMDA and AMPA receptors magnified H2S-induced SCO suppression. Inhibitors of L-type voltage gated Ca2+ channels and transient receptor potential channels prevented H2S-induced SCO suppression. Inhibitors of T-type voltage gated Ca2+ channels, ryanodine receptors, and sodium channels had no measurable influence on H2S-induced SCO suppression. Exposures to > 5 ppm sulfide also suppressed neuronal electrical activity in primary cortical neurons measured by multi-electrode array (MEA), an effect alleviated by pretreatment with the nonselective transient receptor potential channel inhibitor, 2-APB. 2-APB also reduced primary cortical neuronal cell death from sulfide exposure. These results improve our understanding of the role of different Ca2+ channels in acute H2S-induced neurotoxicity and identify transient receptor potential channel modulators as novel structures with potential therapeutic benefits.