Sulfate Reduction Process Research Articles

Achieving efficient autotrophic nitrogen removal in anaerobic membrane bioreactor plus membrane aerated biofilm reactor by regulating nutrient ratios.

It is feasible to integrate an anaerobic membrane bioreactor with a membrane aerated biofilm reactor to efficiently implement the sulfate reduction, simultaneous nitrification and autotrophic denitrification process. However, the effect of parameters on nutrient removal and environmental impacts of the process are unclear. In this study, the reactor performance was mainly influenced by the chemical oxygen demand to sulfate (COD/S) ratio and the ammonium to sulfate (N/S) ratio in long-term operation. Significant models were developed to optimize the two factors using the response surface methodology. Under optimal conditions (COD/S ratio of 2.5 and N/S ratio of 0.3), the system could remove above 86 % COD, 99 % ammonium, and 92 % total inorganic nitrogen. Moreover, this process could reduce energy consumption by 30 % and global warming potential by 50 % compared with traditional anaerobic/oxic activated sludge process. These findings provide guidance for the application of this technology in sulfate-containing municipal sewage treatment.

Synchronised removal of nitrogen and sulphate from rubber industrial wastewater by coupling of Sulfammox and sulphide-driven autotrophic denitrification in anaerobic membrane bioreactor.

Global rubber industry, growing 4-6 % annually with 13.76 million Mt of rubber produced in 2019, significantly impacts the economy. This study explores coupling sulfate-dependent ammonium oxidation (Sulfammox) and sulfide-driven autotrophic denitrification (SDAD) within an anaerobic membrane bioreactor (AnMBR) to treat high-strength natural rubber wastewater. Over 225 days, the AnMBR system achieved maximal chemical oxygen demand (COD), total nitrogen (TN), ammonium nitrogen (NH4+-N), and sulfate sulfur (SO42--S) removal efficiencies of 58 %, 31 %, 13 %, and 45 %, respectively. TN is predominantly removed through Sulfammox (accounting for 49 % of NH4+-N removal), SDAD, and conventional denitrification pathways. Sulfate removal is achieved via Sulfammox (responsible for 43 % of SO42--S removal), and Dissimilatory sulfate-reducing (DSR) processes (contributing 57 % of SO42--S removal). Microbial analysis identified Desulfovibrio and Sulfurospirillum as key microbes, while metagenomic analysis highlighted crucial sulfur and nitrogen cycling pathways. The findings support Sulfammox and SDAD as promising eco-friendly strategies for treating ammonia- and sulfate-rich industrial wastewater.

Petroleum evolution and its genetic relationship with the associated Jinding Pb[sbnd]Zn deposit in Lanping Basin, Southwest China

The spatial association of hydrocarbons with metalliferous ore deposits is found worldwide and is particularly common to MVT PbZn deposits. Heavy oil and bitumen are found in the Jinding PbZn deposit within the Lanping Basin, South China. However, the temporal and genetic associations between hydrocarbons and the deposit are still controversial. To this end, integrating Raman analysis, ReOs geochronology and transmission electron microscopy analysis of the bitumen and in situ S isotope analyses of the sulfide, the petroleum evolution of the Jinding reservoir and its genetic relationship with the PbZn deposits were discussed. Bitumen ReOs data from this study and published works indicate that the late Triassic shales underwent two distinct oil-generation events before mineralisation (~25 Ma), with initial oil generation occurring during the early Cretaceous (~116 Ma) and the second during the early Paleogene (ca. 68–59 Ma). These two ages agree with the modelled thermal history of the Jinding reservoir. Combining the oil-before-ore timing sequence, high metal abundance of the bitumen, two negative sulfur isotope peaks of the sulfide and high S/C atomic ratio of the bitumen from the Jinding deposit, the oil-containing aqueous solutions were considered as one metal carrier during the hydrocarbon migration and accumulation; further, bacterial sulfate reduction and thermo-chemically induced sulfate reduction processes could have participated in the supply of reduced sulfur for the PbZn deposit precipitation.

Modeling and forecasting biogas production from anaerobic digestion process for sustainable resource energy recovery

Anaerobic digestion (AD) is one of the most extensively accepted processes for organic waste cleanup, and production of both bioenergy and organic fertilizer. Numerous mathematical models have been conceived for modeling the anaerobic process.In this study, a new modified dynamic mathematical model for the simulation of the biochemical and physicochemical processes involved in the AD process for biogas production was proposed. The model was validated, and a sensitivity analysis based on the OAT approach (one-at-a-time) was carried out as a screening technique to identify the most sensitive parameters. The model was developed by updating the bio-chemical framework and including more details concerning the physico-chemical process. The fraction XP was incorporated into the model as a particulate inert product arising from biomass decay (inoculum). New components were included to distinguish between the substrate and inoculum, and a surface-based kinetics was used to model the substrate disintegration. Additionally, the sulfate reduction process and hydrogen sulfide production have been included. The model was validated using data extracted from the literature. The model's ability to generate accurate predictions was testified using statistical metrics. The model exhibited excellent performance in forecasting the parameters related to the biogas process, with measurements falling within a reasonable error margin. The relative absolute error (rAE) and root mean square error (RMSE) were both less than 5 %, indicating a high ability of the current model in comparison with the literature. Additionally, the scatter index (SI) was below 10 %, and the Nash-Sutcliffe efficiency (NES) approached one, which affirms the model's accuracy and reliability. Finally, the model was applied to investigate the performances of the AD of food waste (FW). The findings of this study support the robustness of the developed model and its applicability as a virtual platform to evaluate the efficiency of the AD treatment and to forecast biogas production and its quality, CO2 emission, and energy potential across various organic solid waste types.

Coupled transformation pathways of iron minerals and natural organic matter related to iodine mobilization in alluvial-lacustrine aquifer

The complex of natural organic matter (NOM) and iron minerals in sediment is the main host and source of groundwater iodine. However, the transformation pathways of the complex remain unclear. The groundwater and sediment from the Hetao Basin were collected in this study to analyze multi-isotopes, NOM molecular characteristics, and iron mineral phases. The results showed that high-iodine groundwater was mainly observed in the discharge area, where biodegradation of NOM, sulfate reduction and methanogenesis occurred. Compared to the shallow clayey sediments, the confined sandy sediments had lower iodine content, a lower fraction of crystalline iron oxides, and a higher fraction of carbonate associated Fe(II) minerals, suggesting that the release of sediment iodine in the aquifer is related to the transformation of sediment Fe(III) hydroxides/oxides. Moreover, the molecular features of high-iodine groundwater NOM and sandy sediment NOM were characterized by a higher proportion of refractory compounds, suggesting that the reductive transformation of sediment Fe(III) hydroxides/oxides is fueled by degradable organic compounds. The microbial Fe-reducing and/or sulfate-reducing processes cause the enrichment of groundwater iodine in the form of iodide via the transformation of iodine species. These findings provide new insights into the genesis of high-iodine groundwater.

Phase transformation of schwertmannite changes microbial iron and sulfate-reducing processes in flooded paddy soil and decreases arsenic accumulation in rice (Oryza sativa L.)

Rice (Oryza sativa L.) is known to accumulate inorganic arsenic (iAs) and dimethylarsenate (DMA) in its grains, which threatens both human health and rice yield. Although schwertmannite, a metastable Fe (Ⅲ)-oxyhydroxysulfate mineral with extremely high adsorption capacity for iAs, has been proposed to remediate paddy soil to decrease As accumulation in rice, it remains unclear whether the phase transformation of schwertmannite would occur in flooded paddy soil and how its phase transformation changes the soil microbial processes that impact the accumulation of iAs and DMA in grains. Here, we found that amending As-contaminated paddy soil with 0.5%–1% (w/w) schwertmannite decreased the accumulation of iAs and DMA in grains by 37.41%–43.29% and 50.60%–73.89%, respectively, even though schwertmannite has transformed to goethite and secondary FeS was formed in both rhizosphere and bulk soils. The phase transformation of schwertmannite released a considerable amount of SO42− into porewater, thereby increasing the abundances of both sulfate-reducing bacteria and the dsrB gene but decreasing the abundance of iron-reducing bacteria. This result suggested that schwertmannite phase transformation has promoted sulfate-reducing process and weakened iron-reducing process in flooded soil. Such promoted sulfate-reducing process and weakened iron-reducing process in paddy soil can decrease the reductive dissolution of As-bearing (oxyhydr)oxides, increase the formation of secondary FeS mineral for decreasing porewater As concentration, and strengthen the role of Fe plaque as a barrier for As absorption by rice. Additionally, the application of schwertmannite has decreased the abundance of arsM gene and weakened As methylation process in soil. Therefore, the effective decrease of iAs and DMA accumulation in rice grains by schwertmannite can not only be ascribed to the adsorption capacity of schwertmannite for As and the adsorption or incorporation of As by transformation products, but also contributed by the promoted sulfate-reducing process and the weakened iron-reducing process in flooded paddy soil.

Флюидный режим образования вторичных доломитов в палеозойских карбонатных коллекторах Хасырейского месторождения (вал Гамбурцева)

The search for hydrocarbon deposits in the sediments of the Lower Paleozoic complex of the Timan-Pechora oil and gas province, which are associated with the main prospects for increasing reserves, is a relevant topic for research. It is necessary to understand the formation processes of carbonate reservoirs within the complex under consideration to develop a strategy for predicting the structure of the complex reservoirs. Obtaining data on the parameters of the fluid regime of the formation of secondary dolomites in the Paleozoic carbonate reservoirs of the Khasyrey field (Gamburtsev swell) was the aim of the study. We studied primary fluid inclusions in dolomite and anhydrite cements filling vuggy voids in reservoir rocks. We showed that the inclusions contained up to 10 vol. % of the gas phase, which was represented by methane and water vapor. The liquid phase was characterized by a substantially chloride-calcium composition, the salinity is 13.5–23.5 wt. % NaCl-eq. These data might indicate the formation of cavities and cements of secondary dolomites from moderate-temperature solutions of high salinity, which were formed as a result of mixing sedimentation (primary marine) waters and brines of hydrothermal vents. The products of evaporite dissolution in the presence of hydrocarbons and sulfate reduction processes were the most likely source and supplier of the fluids, both the formation of leaching caverns in the rock and the cements performing them. Fluids could enter the upper floors of the section from hydrothermal sources in the basement zones and lower horizons of the sedimentary cover through a system of faults and cracks during tectonic activation.

Reduced sulfur compound formation from a leachate-saturated zone under changing temperature conditions

In the leachate-saturation zone of landfills, sulfate reduction is influenced by temperature and electron donors. This study assessed sulfate reduction behaviors under varied electron donor conditions by establishing multiple temperature variation scenarios based on stable temperature fields within the leachate-saturation zone. The results showed that temperature variations altered the microbial community structure and significantly influenced the sulfate reduction process. A more pronounced effect was observed with a temperature difference of 30 °C compared to one of 10 °C. In addition, sulfate reduction was influenced by the presence of electron donors and acceptors. In the middle and low-temperature regions (35 °C and 25 °C), sulfate reduction reaction of acidic organic matter was more significant, while alcohol and saccharide organic substances were more effective in promoting sulfate reduction at high-temperature regions (55 °C). Notably, a 30 °C temperature difference within the leachate-saturation zone significantly altered the microbial community structure, which influenced the sulfate reduction behavior. In particular, Firmicutes and Synergistota played essential roles in mediating the variance in sulfate reduction efficiency with a 30 °C decrease and 30 °C increase, respectively. The results also revealed that temperature changes within landfills were influenced by leachate migration, therefore, controlling leachate recharge can help prevent secondary risks associated with sulfate reduction processes.

Biochar-Sulfate Reducing Bacteria synergy: A green approach for antimony removal and recovery from high-concentrated waters

Environments with elevated antimony (Sb) levels often result from industrial and mining activities, causing harm to ecosystems due to the inherent toxicity. Traditional treatments aim to eliminate or decrease Sb toxicity, yet they often result in the generation of secondary pollution. This study explores a novel approach for enhancing biological sulfate-reduction by biochar addition to cope with high Sb concentrations. Moreover, this research postulates sulfate-reduction bioprocess as a feasible alternative to obtain valuable antimony sulfide. The findings indicate that sulfate reduction effectively removes antimony, particularly at high concentrations, using a non-specialized inoculum. Biochar plays a pivotal role in enhancing sulfate-reduction rates, reducing lag-phase periods, and enriching the microorganisms responsible for sulfate reduction.Interestingly, lower concentrations of Sb(III) (5–40 mg/L) and Sb(V) (5–100 mg/L) exhibited a lower removal percentage compared to higher concentrations of Sb(III) (80–500 mg/L) and Sb(V) (200–1000 mg/L). This phenomenon was attributed to the excess sulfide hindering the equilibrium of the first-order reaction at lower concentrations, while at higher concentrations, the reaction proceeded more rapidly. A combination of biochemical and physicochemical reactions facilitated the removal of >95 % Sb(III) and >97 % Sb(V) using biochar.Furthermore, various taxa displayed a significant logarithmic rate of change in their abundance, influenced by the application of biochar or the introduction of distinct antimony species. The biogenic sulfide generated through the sulfate reduction process reacted with the Sb species, resulting in the precipitation of stibnite (Sb2S3), Na3SbS3, and Na3SbS4. These precipitates are considered crucial precursors in electronic applications.In conclusion, this study constitutes a pioneering exploration of elevated antimony (Sb) concentrations under sulfate-reducing conditions, significantly contributing to an advancement of knowledge in the application of biological processes.

A self-sustaining effect induced by iron sulfide generation and reuse in pyrite-woodchip mixotrophic bioretention systems: An experimental and modeling study

Dual electron donor bioretention systems have emerged as a popular strategy to enhance dissolved nitrogen removal from stormwater runoff. Pyrite-woodchip mixotrophic bioretention systems showed a promoted and stabilized removal of dissolved nutrients under complex rainfall conditions, but the sulfate reduction process that can induce iron sulfide generation and reuse was overlooked. In this study, experiments and models were applied to investigate the effects of filler configuration and dissolved organic carbon (DOC) dissolution rate on treatment performance and iron sulfide generation in pyrite-woodchip bioretention systems. Key parameters govern that DOC dissolution and microbe-mediated processes were obtained by experiments. The water quality models that integrate one-dimensional constant flow, sorption and microbial transformation kinetics were used to predict the performance of bioretention systems. Results showed that the mixotrophic bioretention system with woodchip mixed in the vadose zone and pyrite in the saturated zone achieves a better performance in both nitrogen removal efficiency and by-product control. Comparably, woodchip and pyrite mixed in the saturated zone could encounter a high secondary pollution risk. The sensitivity coefficients of oxic/anoxic DOC dissolution rates to total nitrogen removal are 0.36 and -2.43 respectively. Iron sulfide generation was affected by DOC distribution and the competition between heterotrophic denitrifiers, autotrophic denitrifiers, and sulfate-reducing bacteria (SRB). DOC accumulation has an antagonistic effect on iron production and sulfate reduction. Extra DOC accumulation favors sulfate reduction while high DOC concentration inhibits pyrite-based denitrification and reduces Fe(III) production. The recycling of iron sulfide can improve the robustness and sustainability of bioretention systems.

Impacts of hydrodynamic disturbance on black blooms: An in-situ study in Lake Taihu

The occurrence of black blooms, a kind of black water phenomenon, mostly formed by the decomposition of cyanobacterial blooms poses a threat to both drinking water supplies and the survival of aquatic organisms. Meteorological and hydrological conditions play a crucial role in their formation, while the specific impact of hydrodynamic disturbances on the black blooms remains unclear. The aim of this study is to investigate in depth the impact of hydrodynamic disturbances on the formation and development of black blooms, as well as their effects on the microbiota in surface sediments during the process. During the occurrence of black blooms in Lake Taihu, in-situ water and surface sediment samples were collected. By combining studies of the changes in water quality and microbial communities, the potential driving mechanisms of hydrodynamic disturbances were analyzed. The results indicate that during the outbreak stage (MS), hydrodynamic disturbances drove the release of anaerobic byproducts in sediments (NH4+-N ≥ 0.5 mg/L, TN ≥ 2.03 mg/L, TP ≥ 0.15 mg/L), and varying levels of hydrodynamic disturbance led to significant differences in microbial communities (ANOSIM, R = 0.477, p < 0.05). This influenced the abundance of microorganisms with carbon and sulfur cycling functions in sediments, where stronger hydrodynamics promoted the coupling of carbon mineralization and fermentation processes, while weaker hydrodynamic disturbances facilitated the coupling of carbon mineralization and sulfate reduction processes. Additionally, hydrodynamic disturbances influenced the potential functions of sulfate-reducing bacteria (SRB) in sediments, altering the interactions between SRB and other microorganisms. This study, for the first time, investigated the impact of hydrodynamics on the formation of black blooms from the perspective of their interaction with microorganisms. These findings broaden our understanding of the significance of hydrodynamic disturbances during black bloom occurrences and contribute to our ability to predict the formation of black blooms through modeling.

Tracing sulfate sources in a tropical agricultural catchment with a stable isotope Bayesian mixing model

Sulfate (SO42−) is an essential anion in drinking water and a vital macronutrient for plant growth. However, elevated sulfate levels can impact ecosystem or human health and could be an important indicator of acid rock drainage or pollution. Therefore, monitoring SO42− sources and transport is important for water quality assessments. This study focused on exploring the sources and transformations of SO42− as well as estimating the proportional contribution of the potential SO42− pollutant sources to groundwater and surface water in a tropical river basin, the Densu River Basin. The study used major ions combined with stable sulfur and oxygen isotope compositions and a Bayesian isotope mixing model, MixSIAR. The major ion characteristics indicate that SO42− concentrations remain stable throughout the rainy and dry seasons but originate from diverse sources. The multi-isotope model (δ34SSO4, δ18OSO4) identified four potential SO42− sources: detergent, precipitation, sewage, and sulfate fertilizer. However, the δ34SSO4 and δ18OSO4 values of the fertilizer source signatures overlapped with those of precipitation and sewage. Nevertheless, the contributions from each source were disentangled using the MixSIAR model, which revealed sewage as the most dominant SO42− pollutant in the Densu Basin, accounting for ~47 % of sulfate in groundwater and ~ 56 % of sulfate in surface water. Sulfate fertilizer (~33 %) was the second most important source after sewage for groundwater, while detergent (~23 %) was the second most important source for surface water. The redox processes of bacterial sulfate reduction and sulfide oxidation were determined to have a minimal impact on the sulfur isotope fractionation within the basin. This study highlights the benefits of combining major ions, sulfur isotopes and the MixSIAR model for identifying sources of sulfate. This approach accounts for uncertainties in source contributions which allows for more robust and reliable apportionment of sulfate sources. The study emphasizes the need for effective waste management and pollution control measures to protect water quality and provides vital guidelines on how to partition sulfate sources on a large catchment scale and evidence for making pollution management decisions on water resources.

Solid bitumen Rhenium-Osmium (Re–Os) isotope geochronology and existing problems: Sampled of Sinian-Cambrian gas reservoir in Sichuan Basin, China

Understanding the key timings related to petroleum evolution is crucial for optimizing exploration targets and assessing oil/gas resources, attract petroleum geologists’ attention worldwide. Recently, hydrocarbon (oil and bitumen) Re–Os isotope dating has been innovatively applied to constrain the timing related to oil/gas generation, however, the resulting Re–Os isochron ages can be complex and challenging to interpret. This study utilizes various geochemical and geochronological data from Sinian to Cambrian natural gas reservoirs in the Sichuan Basin to reconstruct the hydrocarbon evolution process and discuss the significance of different bitumen Re–Os dating results. The gas accumulation in the Sinian-Cambrian reservoirs experienced four stages of evolution: (1) initial oil generation during the Ordovician to Silurian periods, (2) secondary oil generation during the Triassic period, (3) gas generation through thermal cracking of liquid oil from the Jurassic to Cretaceous periods, and (4) gas reservoir redistribution since the late Cretaceous. The Re–Os dates (ca. 485 Ma) of low maturity and biodegraded bitumen from the western Sichuan Basin record the oil generation during the Ordovician before the Caledonian tectonic event. The Re–Os dates (ca.184–128 Ma) of highly mature bitumen associated with MVT Pb–Zn deposits in northern Sichuan Basin provide insights into both liquid oil-cracking and thermochemical sulfate reduction (TSR) processes. The complex Re–Os dates (ca.414 Ma, ca.154 Ma) of highly mature bitumen from the central Sichuan Basin may represent different periods related to either oil or gas generation. Future studies should explore the genetic type, maturity, thermal cracking, or TSR degrees of bitumen to better understand the significance of Re–Os dates.

The different effects of molybdate on Hg(II) bio-methylation in aerobic and anaerobic bacteria.

In nature, methylmercury (MeHg) is primarily generated through microbial metabolism, and the ability of bacteria to methylate Hg(II) depends on both bacterial properties and environmental factors. It is widely known that, as a metabolic analog, molybdate can inhibit the sulfate reduction process and affect the growth and methylation of sulfate-reducing bacteria (SRB). However, after it enters the cell, molybdate can be involved in various intracellular metabolic pathways as a molybdenum cofactor; whether fluctuations in its concentration affect the growth and methylation of aerobic mercury methylating strains remains unknown. To address this gap, aerobic γ-Proteobacteria strains Raoultella terrigena TGRB3 (B3) and Pseudomonas putida TGRB4 (B4), as well as an obligate anaerobic δ-Proteobacteria strain of the SRB Desulfomicrobium escambiense CGMCC 1.3481 (DE), were used as experimental strains. The growth and methylation ability of each strain were analyzed under conditions of 500 ng·L-1 Hg(II), 0 and 21% of oxygen, and 0, 0.25, 0.50, and 1 mM of MoO4 2-. In addition, in order to explore the metabolic specificity of aerobic strains, transcriptomic data of the facultative mercury-methylated strain B3 were further analyzed in an aerobic mercuric environment. The results indicated that: (a) molybdate significantly inhibited the growth of DE, while B3 and B4 exhibited normal growth. (b) Under anaerobic conditions, in DE, the MeHg content decreased significantly with increasing molybdate concentration, while in B3, MeHg production was unaffected. Furthermore, under aerobic conditions, the MeHg productions of B3 and B4 were not influenced by the molybdate concentration. (c) The transcriptomic analysis showed several genes that were annotated as members of the molybdenum oxidoreductase family of B3 and that exhibited significant differential expression. These findings suggest that the differential expression of molybdenum-binding proteins might be related to their involvement in energy metabolism pathways that utilize nitrate and dimethyl sulfoxide as electron acceptors. Aerobic bacteria, such as B3 and B4, might possess distinct Hg(II) biotransformation pathways from anaerobic SRB, rendering their growth and biomethylation abilities unaffected by molybdate.

Barite Replacement as a Key Factor in the Genesis of Sediment-Hosted Zn-Pb±Ba and Barite-Sulfide Deposits: Ore Fluids and Isotope (S and Sr) Signatures from Sediment-Hosted Zn-Pb±Ba Deposits of Iran

Iran hosts more than 350 Precambrian to Cenozoic sediment-hosted Zn-Pb±Ba and barite-sulfide deposits, including shale-hosted massive sulfide (SHMS, also called SEDEX) and Irish-type and Mississippi Valley-type (MVT) mineralization, and barite is a common mineral in these deposits. In the SHMS deposits, barite is typically found as fine-grained disseminations in thin laminae. In these deposits, the sulfide laminae often occur as diagenetic replacements and as bands containing authigenic and diagenetic barite and pyrite framboids. In the Irish-type Zn-Pb-Ba and stratabound barite-sulfide deposits, barite exhibits various textures, including fine-grained disseminated barite, banded zebra textures, veins, and massive barite lenses. In some of the giant Irish-type deposits, as well as in the stratabound barite-sulfide mineralization, the main stratabound sulfide ore is developed within a barite envelope and is characterized by the replacement of barite and pyrite by chalcopyrite, galena, and sphalerite. In the MVT deposits, the formation of barite is often related to dolomitization, and sulfide mineralization involves the replacement of the dolomitized carbonate rocks, as well as associated barite. Fluid inclusion studies on the Irish-type deposits indicate that the temperatures and salinities of the sulfide-forming fluids are higher compared to those of the barite-forming fluids. Fluid inclusion analyses of coarse-grained barites from Irish and MVT deposits reveal their hydrothermal origin. The δ3⁴S values of sulfide minerals (pyrite, sphalerite, and galena) in Irish-type deposits exhibit a broad range of low values (mostly −28 to +5‰), primarily revealing a process of bacterial sulfate reduction (BSR). However, the textures (replacement, colloform, and banded) and more positive sulfur isotope values (+1 to +36‰) in the SHMS Zn-Pb deposits suggest that bacterial sulfate reduction (BSR) plays a less significant role. We suggest that thermochemical sulfate reduction (TSR) connected to the direct replacement of barite plays a more relevant role in providing sulfur for the sulfide mineralization in the SHMS, barite-sulfide, and MVT deposits. Based on the textual evidence, sulfur isotopic data, and fluid inclusion studies, barite has been identified as a key controller for the subsequent Zn-Pb mineralization by providing a suitable host and significant sulfur contribution in the sediment-hosted Zn-Pb and stratabound barite-sulfide deposits. This implies that diagenetic barite might be a precursor to all types of sediment-hosted Zn-Pb mineralization.

Optimization of sulfate reduction and methanogenesis via phase separation in a two-phase internal circulation reactor for the treatment of high-sulfate organic wastewater

To enhance the performance of the internal circulation (IC) reactor when treating high-sulfate organic wastewater, a laboratory-scale two-phase IC reactor with distinct phase separation capabilities was designed, and the sulfate reduction and methanogenesis processes were optimized by segregating the reactor into two specialized reaction zones. The results demonstrated that the first and second reaction areas of the two-phase IC reactor could be maintained at 4.5–6.0 and 7.5–8.5, respectively, turning them into the specialized phase for sulfate reduction and methanogenesis. Through phase separation, the two-phase IC reactor achieved a COD degradation and sulfate reduction efficiency of more than 80% when the influent sulfate concentration exceeded 5,000 mg/L, which were 32.32% and 16.04% higher than that before phase separation. Functional analyses indicated a greater activity of both the dissimilatory and assimilatory sulfate reduction pathways in the acidogenic phase, largely due to a rise in the relative abundance of the genera Desulfovibrio, Bacteroides, and Lacticaseibacillus, the primary carriers of sulfate reduction functional genes. In contrast, all the acetoclastic, hydrogenotrophic, and methylotrophic methanogenesis pathways were inhibited in the acidogenic phase but thrived in the methanogenic phase, coinciding with shifts in the genus Methanothrix, which harbors the mcrA, mcrB, and mcrG genes essential for the final transformation step of all three methanogenesis pathways.

Coupled redox cycling of arsenic and sulfur regulates thioarsenate enrichment in groundwater

High‑arsenic groundwater is influenced by a combination of processes: reductive dissolution of iron minerals and formation of secondary minerals, metal complexation and redox reactions of organic matter (OM), and formation of more migratory thioarsenate, which together can lead to significant increases in arsenic concentration in groundwater. This study was conducted in a typical sulfur- and arsenic-rich groundwater site within the Datong Basin to explore the conditions of thioarsenate formation and its influence on arsenic enrichment in groundwater using HPLC-ICPMS, hydrogeochemical modeling, and fluorescence spectroscopy. The shallow aquifer exhibited a highly reducing environment, marked by elevated sulfide levels, low concentrations of Fe(II), and the highest proportion of thioarsenate. In the middle aquifer, an optimal ∑S/∑As led to the presence of significant quantities of thioarsenate. In contrast, the deep aquifer exhibited low sulfide and high Fe(II) concentration, with arsenic primarily originating from dissolved iron minerals. Redox fluctuations in the sediment driven by sulfur‑iron minerals generated reduced sulfur, thereby facilitating thioarsenate formation. OM played a crucial role as an electron donor for microbial activities, promoting iron and sulfate reduction processes and creating conditions conducive to thioarsenate formation in reduced and high‑sulfur environments. Understanding the process of thioarsenate formation and the influencing factors is of paramount importance for comprehending the migration and redistribution of arsenic in groundwater systems.

Mineralogical and geochemical studies on the Qianjiadian deposit, Songliao Basin, NE China: Insights into multiple metallogenic processes in the sandstone-type uranium deposit

Sandstone-type uranium deposits usually exhibit a range of metallogenic mechanisms. To gain insights into the nature, genetic relationships, and mineralization mechanisms of uranium and associated minerals, representative samples from the Qianjiadian uranium deposit in the Songliao Basin were investigated through detailed mineralogical, elemental geochemical, and in-situ sulfur isotopic analyses. The results provided invaluable information on the various stages of uranium mineralization. During the early diagenetic stage, uranium mineralization occurred in the local organic matter (OM)-enriched sites (TOC = 0.70 ∼ 2.05 %) in the Yaojia Formation. The paragenetic relationship revealed that uranium was firstly precipitated as pitchblende along with the biogenetic framboidal pyrite (δ34S values ranging from −44.1 ‰ to −1.8 ‰) through bacterial sulfate reduction (BSR) process. Simultaneously, organic acids generated through biodegradation of OM caused an acidic fluid condition and subsequent dissolution of feldspars, resulting in the production of kaolinite intergrowth with pitchblende. During the late diagenetic stage, the ore-forming fluid turned alkaline, leading to the conversion of pitchblende into coffinite, with elevated elements such as Si, P, Ca, Zr, and Y in the altered phase. In addition to the contribution of OM and sulfate-reducing bacteria (SRB), pyrite was confirmed as a reducing agent manifested by its replacement by uranium minerals and the Fe-oxide produced along the boundaries. The diagenetic uranium enrichment is mainly hosted in the gray sandstone that experienced reduced alteration of deep hydrocarbons, resulting in pervasive kaolinization and promotion of reduction potential. A significant amount of uranium was fixed by adsorption, as evidenced by the rare observation of independent uranium minerals, but the higher whole-rock U content (U = 133.5 ∼ 394.0 ppm) and the detection of U signal in micro-XRF analysis and EPMA data (U content in representative kaolinite ranges from bld to 0.74 wt%). Overall, the formation of sandstone-type uranium deposits is a long-term and multi-stage process. The early enriched uranium during synsedimentary-diagenetic stages is non-negligible and can even result in an appreciable amount of mineralization, further serving as an important source for the subsequent secondary enrichment.

Behaviours of methane metabolism and community dynamics of methane anaerobic oxidation microbes on carbonate rocks with long-term cultivation in cold seep environment

The anaerobic oxidation of methane (AOM) and sulfate reduction processes in cold seep environments can control methane emission sources and thus mitigate the pressure of increasing global greenhouse gas concentrations. The surfaces of carbonate rocks in cold seep host an abundance of microorganisms that participate in AOM reactions. Investigating the metabolism and conversion of methane by these microbes is instrumental in advancing the exploration and utilization of deep-sea methane energy. Previous studies primarily focused on in-situ investigations of microbial communities on carbonate rocks in cold seep environments, while the dynamic balance of carbonate mineralization caused by microbial community changes and the characteristics of methane consumption in carbonate samples remains unclear. In this study, we used methane as the sole carbon source, enriched and cultured carbonate samples under high pressure, and monitored the community dynamics regularly. The results demonstrated that methane consumption and metabolic pathways played a crucial role in influencing community succession and carbonate mineralization. AOM processes, coupled with sulfate reduction and nitrate reduction, which are dominated by ANME-2c, facilitate the precipitation of calcium carbonate. Conversely, the acetate production process, dominated by ANME-1, may hinder the efficiency of calcium carbonate mineralization. Additionally, the impact of bacterial groups in the enrichment process, through the production of extracellular enzymes, organic acid pathways, and the expression of carbonic anhydrase pathways on carbonate mineralization, should not be disregarded. These findings highlight the significance of diverse pathway methane metabolism in the dynamics of methane consumption, deep-sea microbial communities, carbonate kinetics, and marine biological carbon sequestration processes.

Biostimulation of sulfate reduction for in-situ metal(loid) precipitation at an industrial site in Flanders, Belgium

A 30-month pilot study was conducted to evaluate the potential of in-situ metal(loid) removal through biostimulation of sulfate-reducing processes. The study took place at an industrial site in Flanders, Belgium, known for metal(loid) contamination in soil and groundwater. Biostimulation involved two incorporations of an organic substrate (emulsified vegetable oil) as electron donor and potassium bicarbonate to raise the pH of the groundwater by 1–1.5 units. The study focused on the most impacted permeable fine sand aquifer (8–9 m below groundwater level) confined by layers of non-permeable clay. The fine sands exhibited initially oxic conditions (50–200 mV), an acidic pH of 4.5 and sulfate concentrations ranging from 600 to 800 mg/L. At the central monitoring well, anoxic conditions (−200 to −400 mV) and a pH of 5.9 established shortly after the second substrate and reagent injection. Over the course of 12 months, there was a significant decrease in the concentration of arsenic (from 2500 to 12 μg/L), nickel (from 360 to <2 μg/L), zinc (from 78,000 to <2 μg/L), and sulfate (from 930 to 450 mg/L). Low levels of metal(loid)s were still present after 34 months (end of study). Mineralogical analysis indicated that the precipitates formed were amorphous in nature. Evidence for biologically driven metal(loid) precipitation was provided by compound specific stable isotope analysis of sulfate. In addition, changes in microbial populations were assessed using next-generation sequencing, revealing stimulation of native sulfate-reducing bacteria. These results highlight the potential of biostimulation for long-term in situ metal(loid) plume treatment/containment.