Sulfate Reduction Process Research Articles

Re-circulation of Fe/persulfate regulated sludge fermentation products for sewage treatment: Focus on pollutant removal efficiency, microbial community and metabolic activity

Persulfate (PS)-based technologies have been demonstrated as efficient methods for enhancing the performance of waste activated sludge (WAS) anaerobic fermentation. Except for volatile fatty acids (VFAs), however, some exogenous substances would be also released during this process, which might affect its application as a carbon source for sewage treatment. To fill this knowledge gap, the feasibility of sludge fermentation liquid regulated by Fe/persulfate (PS) (PS-FL) as a carbon source for sewage treatment was investigated in this study. Results indicated that PS-FL exhibits distinct effects on the pollutants removal compared with commercial sodium acetate. It facilitates PO43−-P removal but slightly inhibited COD removal & denitrification, and sludge settleability was also decreased. The mechanistic analysis demonstrated that PS-FL could stimulate the enrichment of phosphorus-accumulating bacteria (i.e. Candidatus Accumulibacter) and the enhancement of their metabolic activities (i.e. PKK), thereby enhancing the biological PO43−-P removal. Moreover, Fe ions in PS-FL could combine with PO43−-P to form a precipitate and thus further contributed to PO43−-P removal. Conversely, the sulfate reduction process induced by SO42− in PS-FL inhibits denitrification by reducing the abundance of denitrifying bacteria (i.e. Dechloromonas) and metabolic activities (i.e. narG). Additionally, PS-FL also decreased the abundance of flocculation bacteria (i.e. Flavobacterium) and down-regulated the expression of functional genes responsible for COD removal, by which it exhibited certain negative effects on COD removal and sludge settleability. Overall, this work demonstrated that PS-FL can re-circulation as a carbon source for sewage treatment, which provides a new approach to recovering valuable carbon sources from WAS.

Anoxia-Related Biogeochemistry of North Indian Ocean

Complex interactions between microbial communities and geochemical processes drive the major element cycles and control the function of marine sediments as a dynamic reservoir of organic matter. Sulfate reduction is globally the dominant pathway of anaerobic mineralisation and is the main source of sulfide. The effective re-oxidation of this sulfide at the direct or indirect expense of oxygen is a prerequisite for aerobic life on our planet. Although largely hidden beneath the oxic sediment surface, the sulfur cycle is therefore critical for Earth’s redox state. This Geochemical Perspectives begins with a brief primer on the sulfur cycle of marine sediments and a description of my own scientific journey through nearly fifty years of studies of sulfur geochemistry and microbiology. Among the main objectives of these studies were to quantify the main processes of the sulfur cycle and to identify the microbial communities behind them. Radiotracers in combination with chemical analyses have thereby been used extensively for laboratory experiments, supported by diverse molecular microbiological methods. The following sections discuss the main processes of sulfate reduction, sulfide oxidation and disproportionation of the inorganic sulfur intermediates, especially of elemental sulfur and thiosulfate. The experimental approaches used enable the analysis of how environmental factors such as substrate concentration or temperature affect process rates and how concurrent processes of sulfate reduction and sulfide oxidation drive a cryptic sulfur cycle. The chemical energy of sulfide is used by chemolithotrophic bacteria, including fascinating communities of big sulfur bacteria and cable bacteria, and supports their dark CO2 fixation, which produces new microbial biomass. During the burial and aging of marine sediments, the predominant mineralisation processes change through a cascade of redox reactions, and the rate of organic matter degradation drops continuously over many orders of magnitude. The main pathways of anaerobic mineralisation and the age control of the organic matter turnover are discussed. In the deep methanic zone, only a few percent of the entire degradation process remains, which provides a small boost of substrate for sulfate reduction through the process of anaerobic methane oxidation. The stable isotopes of sulfur provide an additional tool to understand these diagenetic processes, whereby the combination of microbial isotope fractionation and open system diagenesis generate a differential diffusion flux of the isotopes. In relation to the organic carbon cycle of the seabed and the contribution of methane, the paper discusses the global sulfur budget and the role of sulfate reduction for organic matter mineralisation in different depth regions of the ocean - from coast to deep sea. The published estimates of these parameters are evaluated and compared. Finally, the paper looks at future perspectives with respect to gaps in our current understanding and the need for further studies.

Plant Carbon Sources for Denitrification Enhancement and Its Mechanism in Constructed Wetlands: A Review

Nitrogen pollution in water bodies is a serious environmental problem worldwide. Plant carbonsource (PCS) enhanced denitrification in constructed wetlands (CWs) for wastewater with low chemical oxygen demand to total nitrogen (COD/N) has been one of the most exciting research topics. This paper summarized the related studies with VOSviewer software and found that the major interests were denitrification performance and mechanism in CWs. This article mainly focused on the PCSs’ characteristics, denitrification rate, the influences of key environmental and operational parameters, surface morphology variation, microbial community structure, and denitrification genes. Engineering prospects and existing problems were also introduced. PCSs’ degradation consumes DO and creates favorable conditions for denitrification. The COD/N of wastewater should be maintained at 4–5 by adding PCSs, thus improving denitrification performance and reducing nitrous oxide emission. Aerobic degradation, anaerobic fermentation, dissimilatory nitrate reduction to ammonium, and sulfate reduction processes may consume the carbon released by PCSs depending on the influent quality and environmental conditions. More attention should be paid to the reduction of greenhouse gases and emerging pollutants in CWs with PCSs.

ГЕОХИМИЯ РАННЕГО ДИАГЕНЕЗА ЛИМНОГЛЯЦИАЛЬНЫХ ОТЛОЖЕНИЙ НА ПРИМЕРЕ ОЗЕР НОРИЛО-ПЯСИНСКОЙ ВОДНОЙ СИСТЕМЫ (РОССИЙСКАЯ АРКТИКА)

For the first time, some features of the early diagenesis of bottom sediments of glacial lakes in the Arctic zone of Russia (Pyasino and Melkoe) were studied using long drilling cores. For the first time, the chemical composition of pore waters for the entire thickness of bottom sediments was determined for the lakes of the Russian Arctic. The enrichment of pore waters with biogenic compounds NO3 –, PO4 3– and dissolved organic carbon (DOC) is shown to be a consequence of microbiological destruction of organic matter (OM), as a result of which the labilest components of OM pass into the pore water, and reducing environment arises in the sediments. An increase in Fe, Mn, Al, As, B, Ba, Co, Mo, Ni, Si, Sr, V, Y concentrations in pore waters was found in comparison with supra-bottom water due to the diagenesis of bottom sediments. The role of OM in changes concerned with mineral composition of sediments and formation of authigenic minerals (pyrite, calcite) was shown. Sediments poor in OM are characterized by low concentrations of reduced forms of S (sulphur in the composition of Fe sulphides, H2S, thiosulphfates, etc.), which indicates a low intensity of bacterial sulfate reduction processes.

МЕТАН И СЕРОВОДОРОД В ДОННЫХ ОТЛОЖЕНИЯХ ВОДОХРАНИЛИЩ И ПРУДОВ БАССЕЙНА АЗОВСКОГО МОРЯ

Gas-geochemical studies of bottom sediments and water of Sokolovsky, Grushevsky, Artemovsky, Veselovsky, Proletarsky, Tsimlyansky reservoirs and other dammed reservoirs were carried out. Concentrations of CH4 and ΣH2S in sediments vary from 0.02 to 61.3 μg/g and from <0.01 to 8.36 mg/g of wet sediment, respectively. The highest concentrations of CH4 are observed in the deposits of the Artemovsky, Tsimlyansky and Veselovsky reservoirs, and ΣH2S – in the deposits of the Proletarian, Tsimlyansky and Grushevsky reservoirs. The distribution of CH4 and ΣH2S along the vertical profile of sediments is characterized, as a rule, by an increase in concentrations from the surface layer to the subsurface horizons, in which their maximum peak is recorded, after which the concentrations decrease. The difference between the distribution of ΣH2S and the distribution of CH4 is the more frequent fixation of maximum concentrations of ΣH2S in less deep layers of sediments. The percentage of CH4 from the sum of the studied reduced gases (the coefficient of methanization of КCH4) in sediments varies from 0.004 to 11.1 %, which indicates a significant dominance of the process of sulfate reduction over the process of methanogenesis. The closeness of the relationships of the concentrations of CH4 and ΣH2S between themselves and the values of КCH4, pH and Eh deposits is analyzed.

Effective treatment of acid mine drainage by constructed wetland column: Coupling walnut shell and its biochar product as the substrates

Acid mine drainage (AMD) can cause severe risks to the surrounding environment and ecosystems because of its high metal content and acidity and thus should be disposed of properly. In this study, a novel constructed wetland (CW) model system was established by packing a mixture of walnut shell (WS) and its biochar product as substrates to treat AMD with a pH of 4.0. Sucrose and plant straw broth (PSB) were successively supplemented as external carbon sources to fuel the bacterial sulfate reduction (BSR) process. Heavy metals in the AMD were efficiently removed in the CW column (Cu > 99 %, Cd > 97 %, Zn > 94 %, Cr > 93 % and Fe > 76 %), and the pH increased from 4.0 to 6.5 despite an unsatisfactory sulfate removal efficiency (<40 %). Among the substrates, biochar exhibited a notably higher metal retention capacity, followed by WS. The relative abundance of sulfate-reducing bacteria (SRB) in the biochar substrate was the highest, followed by that in the WS. The cooperation of organic-degrading bacteria mainly consisting of Cellulomonas, Clostridium and Bacteroides and SRB consortia was responsible for biotic AMD treatment in the CW. A mixture of organic solid waste and biochar is a preferable filler candidate for CW systems treating AMD although further evaluation of its capacity under varying conditions is required.

In-Situ Sludge Reduction Performance and Mechanism in Sulfidogenic Anoxic-Oxic-Anoxic Membrane Bioreactors.

The excess sludge generated from the activated sludge process remains a big issue. Sustainable approaches that achieve in situ sludge reduction with satisfactory effluent quality deserve attention. This study explored the sludge reduction performance of sulfidogenic anoxic–oxic–anoxic (AOA) membrane bioreactors. The dynamics of the microbial community and metabolic pathways were further analyzed to elucidate the internal mechanism of sludge reduction. Compared with the conventional anoxic–oxic–oxic membrane bioreactor (MBRcontrol), AOAS150 (150 mg/L SO42− in the membrane tank) and AOAS300 (300 mg/L SO42− in the membrane tank) reduced biomass production by 40.39% and 47.45%, respectively. The sulfide reduced from sulfate could enhance the sludge decay rate and decrease sludge production. Extracellular polymeric substances (EPSs) destruction and aerobic lysis contributed to sludge reduction in AOA bioreactors. The relative abundance of Bacteroidetes (phylum), sulfate-reducing bacteria (SRB, genus), and Ignavibacterium (genus) increased in AOA bioreactors compared with MBRcontrol. Our metagenomic analysis indicated that the total enzyme-encoding genes involved in glycolysis, denitrification, and sulfate-reduction processes decreased over time in AOAS300 and were lower in AOAS300 than AOAS150 at the final stage of operation. The excess accumulation of sulfide in AOAS300 may inactive the functional bacteria, and sulfide inhibition induced sludge reduction.

3D modelling of long-term sulfide corrosion of copper canisters in a spent nuclear fuel repository

Copper canisters are a central component in the safety of the Finnish spent fuel repository concept (KBS-3), where the main corrodent potentially affecting the canister integrity is sulfide. In this study, a 3D numerical model is developed to assess the evolution of sulfide fluxes and the spatially resolved canister corrosion depths for the Finnish spent nuclear fuel repository concept. The backfilled tunnel and the disposal hole are implemented using repository geometries, with sulfide being produced at their interface with the rock (excavation damaged zone) by sulfate reducing bacteria (SRB). Recent experimental findings regarding the microbial sulfate reduction process as well as the scavenging of sulfide via iron (oxy)hydroxides are incorporated in the reactive transport model. Long-term simulations are performed, predicting a heterogeneous corrosion of the canister with a max. corrosion depth of 1.3 mm at the bottom corner after one million years. The evolution of sulfide fluxes shows two main phases, depending on the source of sulfate: first sulfate is supplied by the dissolution of gypsum from the bentonite barriers, followed by a steady, low-level supply from the groundwater. Sensitivity cases demonstrate that both the organic carbon and Fe(III) oxide contents in the bentonite are critical to the corrosion evolution, by being the main electron donor for SRB activities and the major sulfide scavenger in the bentonite, respectively. The backfilled tunnel contributes little to the flux of corrosive sulfide to the canister due to the attenuation by Fe(III)-oxides/hydroxides but induces a notable flux of sulfate into the disposal hole.

Methane seepage intensity distinguish microbial communities in sediments at the Mid-Okinawa Trough

Shallow methane/sulfate transition zones in cold seeps are hotspots to study microbially mediated geochemical cycles due to high methane fluxes. However, our knowledge about the microbial communities in remote seafloor cold seep ecosystems with different methane seepage intensity is still sparse due to the challenge for sampling and visual observations. In this work, three remotely operated vehicle (ROV) video-guided push sediment cores were sampled from cold seep fields with different methane seepage intensity (low-intensity seepage, R5-C1; moderate-intensity seepage, R6-C2; high-intensity seepage, R6-C3) at the western slope of Mid-Okinawa Trough (Mid-OT) and subjected to high throughput sequencing of 16S rRNA genes for bacteria and archaea. Vesicomyid clams and white microbial mats are visible by video at R6-C3 with methane bubbles. The high relative abundances of anaerobic methanotrophic archaea (ANME-1, -2, and -3), δ-Proteobacteriacea and Campylobacteria in R6-C3 indicated that the processes of anaerobic methane oxidation (AOM), sulfate reduction and sulfur oxidation might occur in this active seeping site. In contrast, Bathyarchaeia, Nitrosopumilales, Sphingomonadales, and Burkholderiales were enriched in bubble-free sites, which commonly involved in the degradation of organic compounds. Principal coordinate analysis showed that both bacterial and archaeal communities were clustered according to sampling sites, also indicating the impact of methane seepage intensity on microbial communities. The co-occurrence network analysis revealed that microbes at the site with high methane fluxes mainly cooperated with each other to sustain the ecosystems, whereas competition enhanced at sites with low methane fluxes. Detection of thermophiles Thermoanaerobaculia and Hydrothermarchaeota may indicate microbial transmission from nearby hydrothermal vents, suggesting potential interactions between cold seepage and hydrothermal vent ecosystems. These results expand our knowledge about the composition and distribution of bacteria and archaea with different methane seepage intensity in cold seep field at the Mid-OT, contributing to the ongoing efforts in understanding carbon cycling in the cold seep ecosystems.

Spatial Variations of Aquatic Bacterial Community Structure and Co-Occurrence Patterns in a Coal Mining Subsidence Lake

Land subsidence caused by underground coal mining critically influences the structure and function of ecosystems in mining areas. However, knowledge on the aquatic bacterial community structure and interspecies interactions in subsidence lakes are still limited. To address this issue, we collected water samples from a coal mining subsidence lake and its connected river and investigated the spatial distribution and co-occurrence patterns of the bacterial community using 16S rRNA amplicon sequencing. The results revealed that the bacterial α-diversity in the subsidence lake was higher than that in the river. The bacterial community composition was also significantly different between the subsidence lake and its connected river. Total nitrogen explained 21.4% of the bacterial community composition variation, while sulfate explained 38.4% of the bacterial functional composition variation. Co-occurrence network analysis indicated that the modularity indices and stability of the microbial network in the subsidence lake were significantly higher than those in rivers, which presented more resistance to environmental disturbance. Keystone bacterial taxa in the subsidence lake and river included the Clostridiaceae 1 family, and the Shewanella, Flavobacterium, and Limnohabitans genera, which play vital roles in the carbon, sulfur, and nitrogen cycles. Moreover, functional analysis showed that assimilatory sulfate reduction processes had a major role in the sulfur cycle of the subsidence lake and its connected river ecosystem. Overall, our findings provide new insights into the microbial community structure and assembly in subsidence lakes and its connected river ecosystems, with significant implications for the responsible utilization of water resources and the promotion of sustainable development in mining areas.

Unraveling evolution histories of large hydrothermal systems via garnet U-Pb dating, sulfide trace element and isotopic analyses: A case study of Shuikoushan polymetallic ore field, South China

The Shuikoushan ore field is one of the largest Pb-Zn-Au polymetallic magmatic hydrothermal system in South China and hosts a significant metallogenic potential. In this study, detailed garnet U-Pb dating, sulfide trace element and sulfur isotopic analyses were conducted to reveal the features during ore formation. Chronologically, garnet U–Pb dating yields ore-forming ages of 158.8 ± 1.4 Ma for the Yagongtang deposit, 158.8 ± 2.5 Ma for the Kangjiawan deposit and 154 ± 18 Ma for the Laoyachao deposit, respectively. The ore formation history in the Shuikoushan ore field can be subdivided into four stages, and five types of sphalerite (Sp0 to Sp4), and three types of pyrite (Py to Py2) from early to late are identified. The distinct compostions indicate that sphalerite and pyrite were formed by different trace/minor element substitution mechanisms and oxidation state, although sulfur isotopes indicate a consistent sulfur origin. Combined with previously published studies, this work demonstrates that the Shuikoushan ore field belongs to a prolonged hydrothermal system. Its mineralization was genetically correlated with the emplacement of granodiorite, and the thermochemical sulfate reduction (TSR) process (Stage 2) and bacterial sulfate reduction (BSR) process (Stage 3) dominated the evolution of sulfur and facilitated the participation of sulfides within the Shuikoushan ore field.

Cost-effective desulfurization of acid mine drainage with food waste as an external carbon source: A pilot-scale and long-term study

Sulfate reduction process can be a promising method for simultaneously removing sulfate , metals and metalloids from acid mine drainage (AMD). However, organic matter in AMD is far from enough for sulfate reduction, and an additional carbon source is required, which increases operation costs for AMD treatment. In this study, a two stage AMD treatment system was established (chemical precipitation - sulfate reduction), and food waste hydrolysate was utilized as a carbon source for AMD treatment. Simultaneous removal of sulfate, organics, metals and metalloids was observed in a pilot-scale (10 m 3 ) upflow anaerobic sludge bed (UASB) for over 400 days. Introducing of food waste hydrolysate (FWHS) was not harmful for sulfate reducers in UASB. Decomposition of refractory organic matter in AMD was enhanced after FWHS addition, which led to decreasing of COD concentration (50%) in effluents of UASB. Ten out of 17 organic matter in effluents was no longer detected after FWHS addition. Metals and metalloids from both AMD and FWHS were efficiently removed during the sulfate reduction process (97.7–100%). Volatile fatty acids (acetic and valeric acids) produced during the food waste hydrolysis could be utilized as carbon source for AMD treatment. Interactions among fermentative microbes , sulfate reducers, denitrifiers and methanogens enhanced carbon, sulfur and nitrogen removal in the UASB. Therefore, a cost-effective method for AMD and food waste cotreatment (3.6 kgSO 4 2− /kgTS food waste) was established in this study by reducing carbon source addition (100%), biomass production (93%), VFA production (54.5%) and sulfide emission (50%), which might be applied for AMD recycling at mining sites. • a two-step fermentation and sulfate reduction coupling process was established. • Food waste was used as carbon and nutrients source for acid mine drainage treatment. • Sulfate, carbon, metals and metalloids were efficiently removed (87.3–100%). • The established technology might be used for acid mine drainage treatment in mines.

A novel steady-state model to quantitively assess the effect of pH elevation by dissimilatory sulfate reduction process in acidic waters in mining areas

Acidic waters such as groundwater, drainage and lakes in mining area contain high-strength acids and metal ions, posing serious threats to aquatic ecosystems and human health. Dissimilatory sulfate reduction (DSR)-based processes are attractive technologies for remediating acidic waters because it produces alkalinity and sulfide for metal precipitation and acid neutralization. However, the effects of pH elevation achieved by DSR-based processes are case-sensitive and difficult to be quantitively assessed, which limits the application of DSR process for acidic water remediation. Therefore, in this study, a Sulfidogenic Acid mine water Remediation Model (SARM) considering the DSR process, weak acids balance, metal sulfide and hydroxide precipitations, and gas-liquid exchanges of H2S and CO2, was developed to quantitatively assess the effects of various environmental factors on the pH elevation by a DSR process in acidic waters. A long-term trial of a DSR reactor was conducted to calibrate and validate the SARM. The experimental results revealed that the DSR-based process is effective to relieve acidity. The calibrated SARM demonstrated the excellent performance to predict the pH variation in the DSR reactor, under the varied conditions of influent pH and organic concentration. The calibrated SARM was further validated with data collected from literatures, and the results verified that the proposed model is capable to accurately assess the effect of DSR process on acid neutralization and metal removals under various conditions in steady state. The model was employed to systematically evaluate the impacts of environmental factors on acid remediation within a DSR-based process. The results revealed that the background alkalinity plays an important role in acid neutralization. However, with an increase in sulfate reduction, biogenic sulfide and carbonate become the dominant buffering substances to neutralize acidity. Furthermore, the SARM was used to evaluate the applicability of the DSR-based process for the remediation of acidic waters by evaluating the sulfide production thresholds for acid neutralization and metal removal. The simulation results demonstrated that, the DSR-based process is recommended for the remediation of acidic waters with low background alkalinity. Collectively, the SARM proposed in this study was found to be a useful and efficient tool for quantitatively assessing the potential of DSR-based processes for neutralizing acidic waters, which is vital for biogeochemistry and environmental engineering research.

Performance Comparison of EGSB and IC Reactors for Treating High-Salt Fatty Acid Organic Production Wastewater

This study used the EGSB and IC reactors to treat the high-salt and high-concentration organic wastewater (high-salt fatty acid production wastewater) and compared their performances The experimental results showed that the optimal influent water quality thresholds for both bioreactors to treat this wastewater were a COD concentration of 18,000 mg/L and a sulfate ion concentration of about 8000 mg/L. The reactor operated well when C/S was greater than 2.8. In addition, the value of C/S should not be less than 1.5. This is due to that under this condition, the sulfate reduction process has a significant impact on the removal of COD, and MPB may be inhibited by sulfides. The organic load OLR should not be greater than 10 kgCOD/(m3·d). It was also found that the start-up time of the IC reactor with external circulation was slightly shorter, and the COD removal effect, gas production rate, and load tolerance were slightly better than those of the EGSB reactor, the best reflux ratio of the two reactors was 6:1. The appropriate rising flow rate was 0.4 m/h.

Effects of sulfate reduction processes on the trace element geochemistry of sedimentary pyrite in modern seep environments

Although it has been suggested that the trace element patterns of sedimentary pyrite can be affected by early diagenesis, detailed studies on modern marine environments addressing this hypothesis are scarce. Organoclastic sulfate reduction (OSR) and sulfate-driven anaerobic oxidation of methane (SD-AOM) are the dominant sulfate reduction processes in organic-rich and methane-rich marine sediments, and commonly result in the formation of authigenic pyrite. To better understand how OSR and SD-AOM affect the trace element geochemistry of pyrite, we applied laser ablation – inductively coupled plasma – mass spectrometry (LA-ICP-MS) to analyze trace element contents of pyrite from two methane-seep sites (DH-CL11 and HS148) of the South China Sea. The trace element data are complemented by the measurement of iron isotope compositions of authigenic pyrite. This new data set, supplemented by published sulfur isotope data, improves our understanding of the diagenetic processes during early diagenetic pyrite formation. High δ56Fe and δ34S values of pyrite reflect the dominance of SD-AOM within sulfate-methane transition zones (SMTZs) at both sites (i.e., from 705 to 767 cm below seafloor at site DH-CL11 and from 490 to 690 cm below seafloor at site HS148), whereas pyrite from shallow depth characterized by low δ56Fe values points to early OSR processes. Within the SMTZs, pyrite exhibits highly variable but overall high manganese (Mn) contents (12 to 732 mg/kg at site DH-CL11; 12 to 1145 mg/kg at site HS148), compared to OSR-derived pyrite from shallow depth. Similar to this pattern, pyrite formed at the SMTZ shows higher lead (Pb), zinc (Zn), copper (Cu), and vanadium (V) contents than pyrite formed at shallower depths above the SMTZ. Enrichments of these metals in pyrite forming at the SMTZ are best explained by enhanced reductive dissolution of iron and manganese (oxyhydr)oxides under sulfidic conditions induced by SD-AOM, and subsequent trace element incorporation into pyrite. Arsenic (As), molybdenum (Mo), and antimony (Sb) distributions in pyrite vary between the two study sites. Pyrite from shallow depth of site HS148 has high contents of all three elements, indicating effective immobilization of dissolved As, Mo, and Sb during pronounced OSR. In contrast, apparently less intense OSR at shallow depth of site DH-CL11 allowed for more dissolved As, Mo, and Sb to diffuse downward to greater depth, resulting in the enrichments of these elements in pyrite formed at or close to the SMTZ. Positive correlations between As and cobalt (Co), and between As and nickel (Ni) typify pyrite derived from both OSR and SD-AOM for both study sites, and As-rich pyrite from site DH-CL11 is characterized by a distinctly high Co/Ni ratio. Both patterns suggest that the presence of As affects the uptake of Co and Ni into pyrite. Our study documents that pyrite element contents in methane-rich environments are significantly influenced by different sulfate reduction processes during early diagenesis, allowing the differentiation of OSR-derived pyrite from SD-AOM-derived pyrite by means of trace element geochemistry.

System performance and functional analysis for the methanogenic bioreactor of a two-phase anaerobic digestion system: The effect of influent sulfate

In this study, a lab-scale bioreactor was built to investigate the influence of sulfate on the overall performance, microbial community, and metabolic pathways in the methanogenic bioreactor of a two-phase anaerobic digestion system. The results demonstrated that by gradually cultivating the sludge of the methanogenic bioreactor, a chemical oxygen demand (COD) degradation efficiency of over 65% was achieved for sulfate contents from 10,000 mg/L to 30,000 mg/L. The sulfate reduction performance could only be maintained at a high level for influent COD/sulfate ratios no less than 1.88. In addition, the methane production rate (MPR) decreased from 0.92 L/L/d to 0.28 L/L/d, and the proportion of methane in biogas dropped from 51% to 33% when the influent sulfate exceeded 30,000 mg/L. High-throughput sequencing coupled with PICRUSt2 revealed that the dissimilatory sulfate process could be enhanced by sulfate within 30,000 mg/L. While an amount of greater than 5000 mg/L sulfate remarkably inhibited the assimilatory sulfate reduction process, and this inhibition was induced by the down-regulation of the cysNC, cysC, cysI and cysJ genes. For the methanogenic process, sulfate contents within 30,000 mg/L had no obvious impact on all of the acetoclastic, hydrogenotrophic, and methylotrophic methanogenesis processes, but serious suppression was observed for sulfate amounts greater than 30,000 mg/L. This inhibition primarily originated from the decrease in mcrA, mcrB, and mcrG genes that regulate the conversion of methylcoenzyme M to methane, the last step of all three methanogenesis pathways.

The ecological roles of assembling genomes for Bacillales and Clostridiales in coal seams

Biogenic coalbed methane is produced by biological processes mediated by synergistic interactions of microbial complexes in coal seams. However, the ecological role of functional bacteria in biogenic coalbed methane remains poorly understood. Here, we studied the metagenome assembled genomes (MAGs) of Bacillales and Clostridiales from coal seams, revealing further expansion of hydrogen and acetogen producers involved in organic matter decomposition. In this study, Bacillales and Clostridiales were dominant orders (91.85± 0.94%) in cultured coal seams, and a total of 16 MAGs from six families, including Bacillus, Paenibacillus, Staphylococcus, Anaerosalibacter, Hungatella and Paeniclostridium, were reconstructed. These microbial groups possessed multiple metabolic pathways (glycolysis/gluconeogenesis, pentose phosphate, β-oxidation, TCA cycle, assimilatory sulfate reduction, nitrogen metabolism and encoding hydrogenase) that provided metabolic substrates (acetate and/or H2) for the methanogenic processes. Therein, the hydrogenase-encoding gene and hydrogenase maturation factors were merely found in all the Clostridiales MAGs. β-oxidation was the main metabolic pathway involved in short-chain fatty acid degradation and acetate production, and most of these pathways were detected and exhibited different operon structures in Bacillales MAGs. In addition, assimilatory sulfate reduction and nitrogen metabolism processes were also detected in some MAGs, and these processes were also closely related to acetate production and/or organic matter degradation according to their operon structures and metabolic pathways. In summary, this study enabled a better understanding of the ecological roles of Bacillales and Clostridiales in biogenic methane in coal seams based on a combination of bioinformatic techniques.

The elemental sulfur ore deposit of Salmerón: Las Minas de Hellín basin (Late Miocene, SE Spain)

Strata-bound elemental sulfur deposits occur in different circum-Mediterranean Miocene sedimentary successions containing evaporites and high amounts of organic matter. It is widely known that bacterial sulfate reduction processes are the triggering mechanisms involved in the origin of hydrogen sulfide and the subsequent native sulfur. However, in most of these sedimentary successions, there is controversy over whether elemental sulfur formed in the basin floor, as the same time as the sediments (biosyngenetic), or later, during diagenesis (bioepigenetic). Las Minas de Hellín basin, in the SE Spain, contains one of the largest elemental sulfur deposits in Europe. Based on data recovered from mining company (1903 -1960) and a borehole campaign performed by MINERSA between 1987 and 1988, two native sulfur ore bodies are recognized. The upper sulfur body is hosted by carbonates and diatom-rich levels, whereas the lower sulfur body, only exploited in underground mines now closed, is hosted by gypsum. This work shows a petrological and geochemical study of core samples from the upper sulfur body in the Salmerón area (Murcia), 500 m west of the widely exploited area of Las Minas de Hellín (Albacete). In Salmerón, elemental sulfur occurs as pseudomorphs after primary sedimentary gypsum as well as filling fractures and bed joints. The elemental sulfur replacement is also related to calcification and silicification of the sedimentary biomediated dolomite. The mineralization is considered bioepigenetic formed during early diagenesis. Contribution from hydrothermal waters circulating through adjacent faults are not ruled out.

Fluid flow and water/rock interaction during the Early Triassic evolution of the western Canada sedimentary basin as revealed by carbonate diagenesis

Diagenetic evolution of sedimentary basins, which is crucial to resource exploration and development, and carbon capture, utilization, and storage (CCUS), is mainly controlled by fluid influx associated with the regional tectonic and hydrogeologic setting of these basins. Therefore, petrographic and isotope geochemical studies integrated with geodynamics of sedimentary basins, fluid flow and transport hydrodynamics are insightful tools to reconstruct the regional history of paleofluid flow and their driving mechanisms. This study investigates carbonate diagenesis in the Lower Triassic Montney Formation of the Western Canadian Sedimentary Basin (WCSB) to constrain the origin of diagenetic fluids, their major flow systems, and their association with the tectonics and hydrogeology of the WCSB. Petrographic analysis shows various generations of early-to late-stage non-ferroan to ferroan calcite (C1–C3) and dolomite (D1-D4) cement. Bulk δ13C and δ18O values of carbonate cements range from −7.1 to +0.4‰ and −9.5 to −2.8‰ (VPDB), respectively, noticeably more depleted than those estimated for Early Triassic seawater. Their 87Sr/86Sr isotope ratio, 0.7108 to 0.7128, is significantly more radiogenic than Early Triassic seawater. These isotopic values confirm the extensive interaction of the Montney Formation pore water with hot basinal brines of Precambrian metasediments and siliciclastic strata, the influx of hydrothermal fluids, and high burial temperature in the basin. The 13C-depleted signature of these cements supports the contribution of organic carbon, from the breakdown and oxidation of organic matter and hydrocarbons via microbial and thermochemical sulfate reduction processes. The results of this study suggest that Montney Formation diagenesis was influenced by evolved Montney pore water interacting with fluids sourced from metasediments of the Cordillera thrust belt and topography-driven fluids from Columbian and Laramide tectonism. This study highlights the importance of an integrated approach to better understand changes in fluid compositions during diagenesis and reconstruction of basin-scale paleofluid flow systems in sedimentary basins.

Multiple geochemical and microbial processes regulated by redox and organic matter control the vertical heterogeneity of As and Cd in paddy soil

The heterogeneity of arsenic (As) and cadmium (Cd) in paddy soils seriously hinders the assessment of contamination status and prediction of rice uptake. Their vertical patterns across different environmental conditions and the underlying mechanisms remain largely unexplored. In this study, maximum vertical differences of bioavailable As and Cd within 0–30 cm depth in paddy soils were 4.1-fold and four orders of magnitude, respectively. The vertical patterns of As and Cd followed the vertical redox gradient in long-term reduced paddies, but were shaped by the vertical pH gradient derived from acidic wastewater irrigation in partly oxidized soils. Iron(III)- and sulfate-reducing bacteria played key roles in the formation of vertical pH gradient and the immobilization of As and Cd by iron (hydr)oxides and sulfides under varied redox conditions. Soil redox and organic matter determined the transition between these two mechanisms via regulating microbial iron(III) and sulfate reduction processes. The work proposes that soil vertical As and Cd patterns directly affect the accumulation of As and Cd in different rice cultivars with different vertical root patterns. This is the first study elucidating the controlling mechanisms governing the vertical As and Cd patterns in paddy fields, providing important references to identify, manage and remediate contaminated paddy fields.