Sulfate Reduction Research Articles

Amorphous MoS2 from a machine learning inter-atomic potential.

Amorphous molybdenum disulfide has shown potential as a hydrogen evolution catalyst, but the origin of its high activity is unclear, as is its atomic structure. Here, we have developed a classical inter-atomic potential using the charge equilibration neural network method, and we have employed it to generate atomic models of amorphous MoS2 by melting and quenching processes. The amorphous phase contains an abundance of molybdenum and sulfur atoms in low coordination. Besides the 6-coordinated molybdenum typical of the crystalline phases, a substantial fraction displays coordinations 4 and 5. The amorphous phase is also characterized by the appearance of direct S-S bonds. Density functional theory shows that the amorphous phase is metallic, with a considerable contribution of the 4-coordinated molybdenum to the density of states at the Fermi level. S-S bonds are related to the reduction of sulfur, with the excess electrons spread over several molybdenum atoms. Moreover, S-S bond formation is associated with a distinctive broadening of the 3s states, which could be exploited for experimental characterization of the amorphous phases. The large variety of local environments and the high density of electronic states at the Fermi level may play a positive role in increasing the electrocatalytic activity of this compound.

Bacterial adhesion and corrosion behavior of different pure metals induced by sulfate reducing bacteria

The corrosion behaviors of four pure metals (Fe, Ni, Mo and Cr) in the presence of sulfate reducing bacteria (SRB) were investigated in enriched artificial seawater (EASW) after 14-day incubation. Metal Fe and metal Ni experienced weight losses of 1.96 mg cm−2 and 1.26 mg cm−2, respectively. In contrast, metal Mo and metal Cr exhibited minimal weight losses, with values of only 0.05 mg cm−2 and 0.03 mg cm−2, respectively. In comparison to Mo (2.2 × 106 cells cm−2) or Cr (1.4 × 106 cells cm−2) surface, the sessile cell counts on Fe (4.0 × 107 cells cm−2) or Ni (3.1 × 107 cells cm−2) surface was higher.

Remediation of heavy metal-contaminated estuarine sediments by strengthening microbial in-situ mineralization

The production of in-situ iron-sulfide minerals through sulfate reduction is commonly used to immobilize heavy metals in sediments and waste residues from abandoned non-ferrous mines. Ensuring a consistent supply of organic carbon sources, such as small molecular organic acids, under optimal reduction conditions, is essential for effective biomineralization. In this study, we developed a technique to enhance the biomineralization (iron-sulfide minerals) capacity of native sulfate-reducing bacteria to immobilize heavy metals, using the facultative anaerobic fermentation bacterium Bacillus coagulans to bind to waste olivine, providing small molecular organic acids required by sulfate-reducing bacteria while providing more reduction conditions for remediation systems.Our results showed that, compared with the control group (Control) and the group added with medium (Cul), the groups added with Bacillus coagulans (Cul + Bio) and the combination of Bacillus coagulans and olivine (Cul + Bio + Oli), significantly increased the overlying water pH value, pH remained above 8 in the final stage of remediation, and decreased the redox potential and sulfate concentration, ORP remained −80 mV, SO42− concentration below 600 mg/L at the end of remediation. The addition of Bacillus coagulans and olivine helped stabilize heavy metals Cu, Pb, Zn, and Cd by reducing their release into the liquid phase. Cd and Pb were found to be in more stable forms within the solid phase. In the Cul + Bio and Cul + Bio + Oli groups, sulfur primarily existed as more reductive FeS, accounting for 55% and 75% of the sulfur speciations, respectively. Desulfuromonadia, Desulfuromonas, Desulfofustis, and Geothermobacter have been identified in the Cul + Bio + Oli experimental group in high abundance and are capable of dissimilatory sulfate reduction. The combined application of microorganisms and waste olivine offers an effective strategy for remediating in-situ heavy metal-contaminated soils/sediments, thereby establishing a theoretical and practical foundation for employing microbial mineralization in the in-situ remediation of heavy metals in sediment.

Diagenetic history and porosity evolution of the Middle Permian clastic-carbonate mixed system, Indus Basin, Pakistan: Implications for reservoir development

This study deals with unraveling the diagenesis-induced porosity evolution in a mixed clastic-carbonate sequence of the Middle Permian Indus Basin, Pakistan. Multiple data sets including outcrop, petrography, cathodoluminescence, scanning electron microscopy (SEM), mineralogy, and geochemical isotopic compositions were integrated to establish a link between porosity evolution and diagenesis. The spatial thickness and facies variations of the strata at outcrop scale are inherently controlled by the underlying bathymetry of the basin with deepening westward trend. The low values of δ18O of the target strata, relative to average values of the Permian carbonate, hints to diagenetic alteration in the strata. The data sets used in this study reveal modification of the strata in four environments, that is, i) early marine diagenesis indicated by micritization, pervasive dolomitization and isopachous fibrous cements, followed by ii) meteoric dissolution, and iii) shallow burial diagenetic processes including the precipitation of blocky cement, compaction of skeletal and non-skeletal allochems, and stylolites, and iv) a deep burial environment, characterized by pressure solution, and micro-fractures. The clastic intervals host subangular to subrounded quartz grains, floating textures, and almost complete absence of deleterious clay minerals, consequently resulting in the preservation of primary porosity. The primary porosity of carbonate intervals is preserved in the form of intercrystalline and intracrystalline porosity. The secondary porosity evolved through various diagenetic phases in the form of fractures and dissolution. The diagenetic solution mediated by organic matter in carbonates may have experienced both bacterial decomposition and thermochemical sulfate reduction, precipitating sulfides within the pores. The plug porosity/permeability analyses generally suggest high porosity in the siliciclastic unit, and carbonates with wackestone fabric while lower values were observed for the inner shelf pure carbonate facies. However, both intervals show very low permeability values probably due to isolated moldic pores and intense micritization. Therefore, clastic intervals may provide an opportunity to serve as a moderate reservoir; however, the carbonate intervals possess very low permeability values and could generally be considered as low-moderate reservoir potential.

Ru Single Atom Dispersed on MoS2/MXene for Enhanced Sulfur Reduction Reaction in Lithium-Sulfur Batteries.

The high theoretical energy density (2600 Whkg-1) and low cost of lithium-sulfur batteries (LSBs) make them an ideal alternative for the next-generation energy storage system. Nevertheless, severe capacity degradation and low sulfur utilization resulting from shuttle effect hinder their commercialization. Herein, Single-atom Ru-doped 1T/2H MoS2 with enriched defects decorates V2C MXene (Ru-MoS2/MXene) produced by a new phase-engineering strategy employed as sulfur host to promote polysulfide adsorption and conversion reaction kinetics. The Ru single atom-doped adjusts the chemical environment of the MoS2/MXene to anchor polysulfide and acts as an efficient center to motivate the redox reaction. In addition, the rich defects of the MoS2 and ternary boundary among 1T/2H MoS2 and V2C accelerate the charge transfer and ion movements for the reaction. As expected, the Ru-MoS2/MXene/S cathode-based cell exhibits a high-rate capability of 684.3 mAh g-1 at 6 C. After 1000 cycles, the Ru-MoS2/MXene/S cell maintains an excellent cycling stability of 696 mAh g-1 at 2 C with a capacity degradation as low as 0.02% per cycle. Despite a high sulfur loading of 9.5mg cm-2 and a lean electrolyte-to-sulfur ratio of 4.3, the cell achieves a high discharge capacity of 726 mAh g-1.

Identification of Gut Microbiome Signatures Associated with Indole Pathway in Tryptophan Metabolism in Patients Undergoing Hemodialysis.

Microbiota tryptophan metabolism and the biosynthesis of indole derivatives play an important role in homeostasis and pathogenesis in the human body and can be affected by the gut microbiota. However, studies on the interplay between gut microbiota and tryptophan metabolites in patients undergoing dialysis are lacking. This study aimed to identify the gut microbiota, the indole pathway in tryptophan metabolism, and significant functional differences in ESRD patients with regular hemodialysis. We performed the shotgun metagenome sequencing of stool samples from 85 hemodialysis patients. Using the linear discriminant analysis effect size (LEfSe), we examined the composition of the gut microbiota and metabolic features across varying concentrations of tryptophan and indole metabolites. Higher tryptophan levels promoted tyrosine degradation I and pectin degradation I metabolic modules; lower tryptophan levels were associated with glutamate degradation I, fructose degradation, and valine degradation modules. Higher 3-indoxyl sulfate concentrations were characterized by alanine degradation I, anaerobic fatty acid beta-oxidation, sulfate reduction, and acetyl-CoA to crotonyl-CoA. Contrarily, lower 3-indoxyl sulfate levels were related to propionate production III, arabinoxylan degradation, the Entner-Doudoroff pathway, and glutamate degradation II. The present study provides a better understanding of the interaction between tryptophan, indole metabolites, and the gut microbiota as well as their gut metabolic modules in ESRD patients with regular hemodialysis.

Endophytic bacterial diversity in the latex-bearing caulosphere of Hevea brasiliensis Müll. Arg.

Rubber trees are a commercial cash crop, and the milky latex or polyisoprene they produce is the natural source of rubber. Little is known about the bacterial populations found in active zone of latex-bearing caulosphere. We employed a tailored cloud microbial bioinformatic approach for the identification and potential hypothetical ecological roles of an uncultured endophytic hidden bacterial community in the active zone of the latex-bearing caulosphere of Hevea brasiliensis. Small pieces of slivers were collected from healthy plant from the village: Belonia, South Tripura, rubber plantation in Northeastern India. These uncultured bacteria were identified using the V3-V4 hypervariable amplicon region of the 16S rDNA gene. A total of 209,586 contigs have been generated. EasyMAP Version 1.0, a cloud-based microbial bioinformatics tool with an integrated QIIME2 pipeline, was used to analyze contigs. We detected 15 phyla and 91 OTUs (operational taxonomic units). Proteobacteria (73.5%) was the most enriched phylum, followed by Firmicutes (13.8%), Bacteroidetes (5.2%), and Actinobacteria (3.2%). Ammonia oxidizers, sulfate reducers, dehalogenation, chitin degradation, nitrite reducers, and aromatic hydrocarbon degraders were the most prevalent functional categories in the active zones of caulosphere. Furthermore, Gammaproteobacteria (49.2%) and Erwinia (29.19%) were the most abundant classes and genera of endophytic bacterial communities. Thus, the presence of a substantial amount of phosphate-solubilizing Gammaproteobacteria (PSB) may stimulate growth, increase plant resilience, suppress disease, and aid in the rubber and sugar breakdown. This is the first report of microbial endophytes associated with Hevea caulosphere.

Properties of silver and copper nanoparticles obtained by the methods of «green» chemistry

Signifcant challenges for the modern international community are population growth and climate change, and the latest technologies are helping to solve them. These include nanotechnologies that are capable of positively influencing the quality of agricultural products, minimising the negative impact of pesticides on the environment and human health, and increasing production productivity and food safety. Nanotechnology helps to minimise waste by producing more efcient products, leading to the development of precision agriculture and efcient resource management. Minimising the production of hazardous substances, reducing energy consumption in green nanotechnology and almost no toxic chemicals make green nanomaterials widely used and desirable in various felds of human activity. Traditional and new methods for the formation of nanosized materials are considered, with an emphasis on their advantages and disadvantages. Extra- and intracellular ways of nanoparticle formation, as well as ascending and descending methods are described. The aim of the work was to establish the possibility of green synthesis of CuO nanoparticles using peppermint and lemon balm extracts. The plant extracts were prepared by ethanol extraction from the leaves in an extractor. The extract was separated from the plant material by fltering through flter paper. Copper nanoparticles were synthesised by the reduction of copper sulphate in the presence of peppermint or lemon balm extract, which acted as both a reducing agent and a nanoparticle stabiliser. The paper shows the possibility of synthesising copper oxide nanoparticles by the method using peppermint (Mentha piperita) and lemon (Melissa ofcinalis L.) balm leaf extracts. The TEM morphological study of Cu0 metal nanoparticles in the volume of polymeric nanocomposites and those created by the green synthesis method showed that the average size of copper (Cu0) nanoparticles is 3.5 and 12.2 nm, respectively. It was found that the thermo-chemical method of creating nanocomposites is cheap and accessible, but causes the formation of small metal nanoparticles, in contrast to the polymeric nanocomposite created by the green synthesis method, which is environmentally friendly and occurs at low temperatures. Key words: nanobiotechnology, nanoparticles, environmentally friendly products, nanoparticles, copper oxide, silver particles.

A quantitative analysis on thermochemical sulfate reduction products of two model compounds: Implications for reaction mechanism and alteration process of hydrocarbons

Thermochemical sulfate reduction (TSR) is an important redox reaction that markedly alters hydrocarbons in deep reservoirs. Although the major achievements that involve reaction mechanism, process, and geochemical characteristics were attained in the last 50 years, a quantitative TSR model that includes major products was not built, which restricts the understanding of the reaction mechanism and the generation process of hydrocarbons in TSR. In this study, two series of thermal simulation experiments of the TSR involving n-octadecane (n-C18) and n-dodecylbenzene (C12B) with MgSO4 and H2O in a confined gold-tube system were conducted, and all the major products in different phases, particularly oxygen-containing compounds, were quantitatively analyzed. The results indicated that the high-molecular-weight (HMW) oxygenated compounds in heavy products were predominated by ketones, followed by alcohol and acids, and the low-molecular-weight (LMW) organic acids in water mainly comprised acetic acids, followed by formic acid and propionic acid. Both oxygen-containing compounds prompted the TSR process but in different ways. The accumulation of HMW oxygenated compounds in the non-autocatalytic stages was essential for initiating the catalyzed reaction of TSR. In addition, the oxygenated compounds of hydrocarbons enhance polarity, making hydrocarbons easier to contact with HSO4− or [MgSO4] CIP. The LMW organic acids possibly prompted the TSR process by acidifying the water and thus facilitating the formation of HSO4− and [MgSO4] CIP. The oxidation reaction during TSR possibly converted HMW oxygenated compounds to LMW organic acids and CO2. The quantitative analysis of products in TSR revealed that TSR destroyed the hydrocarbons more rapidly but in a different way from thermal cracking and that the generation process of hydrocarbon types in TSR was in the following order: heavy hydrocarbon, gaseous hydrocarbon/light hydrocarbon/solid bitumen, and gaseous hydrocarbon/solid bitumen. Compared with oil cracking, the TSR promoted the oil reservoir to rapidly progress to more mature stages. The hydrocarbon precursor and reaction extent affected the generation process and the character of all products in the TSR. These results can provide an improved understanding of the TSR mechanism and process and be useful in the evaluation of petroleum potential for TSR-altered oils.

Iodine-doped carbon nanotubes boosting the adsorption effect and conversion kinetics of lithium-sulfur batteries

Compared with lithium-ion batteries (LIBs), lithium-sulfur batteries (LSBs), based on electrochemical reactions involving multi-step 16-electron transformations provide higher specific capacity (1672 mAh g−1) and specific energy (2600 Wh kg−1), exhibiting great potential in the field of energy storage. However, the inherent insulation of sulfur, slow electrochemical reaction kinetics and detrimental shuttle-effect of lithium polysulfides (LiPSs) restrict the development of LSBs in practical applications. Herein, the iodine-doped carbon nanotubes (I-CNTs) is firstly reported as sulfur host material to the enhance the adsorption-conversion kinetics of LSBs. Iodine doping can significantly improve the polarity of I-CNTs. Iodine atoms with lone pair electrons (Lewis base) in iodine-doped CNTs can interact with lithium cations (Lewis acidic) in LiPSs, thereby anchoring polysulfides and suppressing subsequent shuttling behavior. Moreover, the charge transfer between iodine species (electron acceptor) and CNTs (electron donor) decreases the gap band and subsequently improves the conductivity of I-CNTs. The enhanced adsorption effect and conductivity are beneficial for accelerating reaction kinetics and enhancing electrocatalytic activity. The in-situ Raman spectroscopy, quasi in-situ electrochemical impedance spectroscopy (EIS) and Li2S potentiostatic deposition current–time (i-t) curves were conducted to verify mechanism of complex sulfur reduction reaction (SRR). Owing to above advantages, the I-CNTs@S composite cathode exhibits an ultrahigh initial capacity of 1326 mAh g−1 as well as outstanding cyclicability and rate performance. Our research results provide inspirations for the design of multifunctional host material for sulfur/carbon composite cathodes in LSBs.

Multi-proxy record of the Austrian Upper Triassic Polzberg Konservat-Lagerstätte in light of the Carnian Pluvial Episode

We present a multi-proxy investigation of a lower Carnian basinal succession from Polzberg in the Northern Calcareous Alps (Lower Austria). A section comprising a unique Konservat-Lagerstätte was studied based on bio- and chemostratigraphy along with geophysical methods, yielding a detailed and robust stratigraphic calibration of the Polzberg succession. The Polzberg section revealed the paleoceanographic history and helped to identify a global climatic reversal, the Carnian Pluvial Episode. The age of the Upper Triassic Reingraben formation in the Northern Calcareous Alps is refined as the Austrotrachyceras austriacum Zone within the lower Carnian (Julian 2). Ammonoids and conodonts provide a detailed biostratigraphic subdivision that serves as a basis for analyses of the faunal distribution and the paleoenvironmental evolution of the Upper Triassic Reifling Basin. The succession includes lithological and facies changes similar to those of coeval units in the Tethys. The Carnian was characterized by a weak (~ 1‰) positive δ13C trend, punctuated by a negative shift during the lower Carnian corresponding to the initiation of the Carnian Pluvial Episode, a period representing the onset of early/late Carnian transitional global greenhouse conditions. Organic maturity parameters and the conodont alteration index (CAI) show that the thermal overprint of the Polzberg section is low. Biomarker proxies suggest that the organic matter of the uppermost Göstling formation is a mixture of marine and terrestrial material deposited in a dysoxic environment. Within the overlaying Reingraben formation, the amount of marine biomass decreased gradually upwards. Oxygen-depleted conditions, probably due to water-column stratification, continued during deposition of the Reingraben formation. Bacterial sulfate reduction played a major role in organic matter degradation.

The Chemical Composition of some Waters from Slacks in Rameswaram Island, Madras State

Analyses of pH, total dissolved solids, CO,, HCO3, Cl, SO4, Ca, Mg, Na and K are presented for water samples from dune slacks in Rameswaram Island. Comparison of these analyses has been attempted with well waters from the area, sea water and world average fresh water. It is inferred that these slacks are under the influence of sea water but ion-exchange process similar to those in arid alkali soils appear to be responsible for Ca/HCO3 ratios of less than unity and Na/Cl and Mg/Cl ratios greater than those in sea water. Exceptionally high Na2Co3 and NaHCO3, contents in one of the slack waters is explained on the basis of sulphate reduction due to favourable conditions developed locally there.

Water Composition, Biomass, and Species Distribution of Vascular Plants in Lake Agmon-Hula (LAH) (1993–2023) and Nearby Surroundings: A Review

A significant change to the land cover in the Hula Valley was carried out during the 1950s: A swampy area densely covered by aquatic vegetation and the old shallow lake Hula were drained. The natural shallow lake and swamps land cover were converted into agricultural development land use in two stages: (1) Drainage that was accomplished in 1957; (2) Implementation of the renovated hydrological system structure, including the newly created shallow Lake Agmon-Hula (LAH), was completed in 2007. The long-term data record of the restored diversity of the submerged and emerged aquatic plant community, and its relation to water quality in the newly created shallow Lake Agmon-Hula LAH, was statistically evaluated. Internal interactions within the LAH ecosystem between aquatic plants and water quality, including nitrification, de-nitrification, sedimentation, photosynthetic intensity, and plant biomass and nutrient composition, were statistically evaluated. The plant community in LAH maintains a seasonal growth cycle of onset during late spring–summer and dieback accompanied by decomposed degradation during fall–early winter. The summer peak of aquatic plant biomass and consequent enhancement of photosynthetic intensity induces a pH increase during daytime and carbonate precipitation. Nevertheless, the ecosystem is aerobic and sulfate reduction and H2S concentration are negligible. The Hula reclamation project (HP) is aimed at the improvement of eco-tourism’s integration into management design. The vegetation research confirms habitat enrichment.

Reaction Mechanism Catalyzed by the Dissimilatory Sulfite Reductase - The Role of the Siroheme-[4FeS4] Cofactor.

The present work is another part of our investigation on the pathway of dissimilatory sulfate reduction and covers a theoretical study on the reaction catalyzed by dissimilatory sulfite reductase (dSIR). dSIR is the terminal enzyme involved in this metabolic pathway, which uses the siroheme-[4Fe4S] cofactor for six-electron reduction of sulfite to sulfide. In this study we use a large cluster model containing siroheme-[4Fe4S] cofactor and protein residues involved in the direct interactions with the substrate, to get insight into the most feasible reaction mechanism and to understand the role of each considered active site component. In combination with earlier studies reported in the literature, our results lead to several interesting insights. One of the most important conclusions is that the reaction mechanism consists of three steps of two-electron reduction of sulfur and the probable role of the siroheme-[4Fe4S] cofactor is to ensure the delivery of packages of two electrons to the reactant.

Construction and catalysis role of a kinetic promoter based on lithium-insertion technology and proton exchange strategy for lithium-sulfur batteries

The high theoretical energy density and specific capacity of lithium-sulfur (Li-S) batteries have garnered considerable attention in the prospective market. However, ongoing research on Li-S batteries appears to have encountered a bottleneck, with unresolved key technical challenges such as the significant shuttle effect and sluggish reaction kinetics. This investigation explores the catalytic efficacy of three catalysts for Li-S batteries and elucidates the correlation between their structure and catalytic impacts. The results suggest that the combined utilization of lithium-insertion technology and a proton exchange approach for δ-MnO2 can optimize its electronic structure, resulting in an optimal catalyst (H/Li inserted δ-MnO2, denoted as HLM) for the sulfur reduction reaction. The replacement of Mn sites in δ-MnO2 with Li atoms can enhance the structural stability of the catalyst, while the introduction of H atoms between transition metal layers contributes to the satisfactory catalytic performance of HLM. Theoretical calculations demonstrate that the bond length of Li2S4 adsorbed by the HLM molecule is elongated, thereby facilitating the dissociation process of Li2S4 and enhancing the reaction kinetics in Li-S batteries. Consequently, the Li-S battery utilizing HLM as a catalyst achieves a high areal specific capacity of 4.2 mAh cm−2 with a sulfur loading of 4.1 mg cm−2 and a low electrolyte/sulfur (E/S) ratio of 8 μL mg−1. This study introduces a methodology for designing effective catalysts that could significantly advance practical developments in Li-S battery technology.

Monolayers APS3 (A = Cr, Co) as cathode hosts for lithium/sodium-sulfur batteries with enhanced electrochemical performance

Metal-sulfur batteries (M–S batteries, M = Li, Na), because of their high energy density and low cost, are expected to become the next-generation energy storage systems. However, their commercial applications are impeded by the poor conductivity of polysulfides, the “shuttle effect” of soluble M2Sn (n = 4, 6, 8), and the slow reaction kinetics. In this work, we perform first-principles calculations to find that the two-dimensional APS3 (A = Cr, Co) monolayers are effective sulfur host materials for high-performance M–S batteries. The metallic electronic structures of APS3 can accelerate electron transfer in reaction processes. The shuttle effect is inhibited by moderate binding strength between APS3 and M2Sn. Remarkably, APS3, as a bifunctional electrocatalyst, can greatly reduce the rate-limiting step of sulfur reduction reaction (SRR) and the decomposition barriers of Li2S/Na2S. We further explored the effect of strain engineering on the catalytic activity of APS3 for SRR and found that the battery performance can be regulated by varying the applied strains ranging from −2 % to 5 %. These findings provide a new direction for the design of highly efficient catalysts for M–S batteries.

Electron delocalization-enhanced sulfur reduction kinetics on an MXene-derived heterostructured electrocatalyst

Electron delocalization-enhanced sulfur reduction kinetics on an MXene-derived heterostructured electrocatalyst

The mechanism of microbial sulfate reduction in high concentration sulfate wastewater enhanced by maifanite

Excessive sulfate levels in water bodies pose a dual threat to the ecological environment and human health. The microbial removal of sulfate encounters challenges, particularly in environments with high sulfate concentrations, where the gradual accumulation of sulfide hampers microbial activity. This study focuses on elucidating the mechanisms underlying the enhancement of microbial sulfate reduction in high-concentration sulfate wastewater through a comparative analysis of maifanite and zeolite biostimulants. The investigation reveals that zeolite primarily facilitates microbial growth by providing attachment sites, while maifanite augments sulfate-reducing bacteria (SRB) activity through the release of active substances such as Mo, Ca, and Cu. The addition of maifanite proves instrumental in enhancing microbial activity, manifesting as increased microbial load and protein production, augmented extracellular polymer generation, accelerated electron transfer, and facilitated microbial growth and biofilm formation. Noteworthy is the observation that the combined application of maifanite and zeolite exhibited a synergistic effect, resulting in a 167 % and 68 % increase in sulfate reduction rate compared to the utilization of maifanite (0.12 d−1) or zeolite (0.19 d−1) in isolation. Within this synergistic context, the relative abundance of Desulfobacteraceae reaches a peak of 15.4 %. The outcomes of this study corroborate the distinct promotion mechanisms of maifanite and zeolite in microbial sulfate reduction, offering novel insights into the application of maifanite in the context of high-concentration sulfate removal.

Response of microbial communities and biogeochemical cycling functions to sediment physicochemical properties and microplastic pollution under damming and water diversion projects

Understanding the interactions among flow-sediment, microorganisms, and biogeochemical cycles is crucial for comprehending the ecological response mechanisms of dams and water diversion. This study focused on the spatial patterns of carbon, nitrogen, phosphorus, and sulfur (CNPS) cycle functional genes in the water resource for the middle route of the South-to-North Water Diversion Project in China, specifically the Danjiangkou Reservoir (comprising the Han and Dan reservoirs). The investigation incorporated sediment physicochemical properties and microplastic pollution. Numerous microbial species were identified, revealing that microbial communities demonstrated sensitivity to changes in sedimentary mud content. The communities exhibited greater β diversity due to finer sediment particles in the Han Reservoir (HR), whereas in the Dan Reservoir (DR), despite having higher sediment nutrient content and MPs pollution, did not display this pattern. Regarding the composition and structure of microbial communities, the study highlighted that sediment N and P content had a more significant influence compared to particle size and MPs. The quantitative microbial element cycling (QMEC) results confirmed the presence of extensive chemolithotrophic microbes and strong nitrogen cycle activity stemming from long-term water storage and diversion operations. The denitrification intensity in the HR surpassed that of the DR. Notably, near the pre-dam area, biological nitrogen fixation, phosphorus removal, and sulfur reduction exhibited noticeable increases. Dam construction refined sediment, fostering the growth of different biogeochemical cycling bacteria and increasing the abundance of CNPS cycling genes. Furthermore, the presence of MPs exhibited a positive correlation with S cycling genes and a negative correlation with C and N cycling genes. These findings suggest that variations in flow-sediment dynamics and MPs pollution have significant impact the biogeochemical cycle of the reservoir.

Effect of coastal hypoxia on bacterial diversity as elucidated through 16S rRNA amplicon sequencing

The formation of oxygen-depleted zones in the bottom waters is one of the most widespread phenomena in coastal areas. Upwelling episodes along India’s west coast due to the southwest monsoon increase biological productivity, further lowering the dissolved oxygen in the upwelled waters, which intensifies annually between June and October. Here, we have determined the changes in the microbial community in response to the varying oxygen levels and other physicochemical parameters at the Candolim Time Series Station using high-throughput sequencing. Amplicon Sequence Variants across all the samples collected in different seasons were mostly affiliated to the phyla Proteobacteria, Actinobacteria, Bacteroidetes, Verrucomicrobia, Chloroflexi, Firmicutes and Planctomycetes, with the most dominant being Proteobacteria (21-41%). Statistical analysis revealed that microbial diversity differed significantly with changing DO, ammonia, nitrate and nitrite concentrations during different seasons. The microbial community shift due to seasonal hypoxia results in the differential biogeochemical cycling of essential nutrients, with certain years seeing redox conditions up to sulphate reduction while certain years seeing only nitrogen loss. Future global warming scenarios will serve as a big challenge for understanding the role of microbial diversity and its implications in the cycling of natural elements.