Coupling of selenate reduction and pyrrhotite oxidation by indigenous microbial consortium in natural aquifer.

Pyrrhotite is ubiquitously found in natural environment and involved in diverse (bio)processes. However, the pyrrhotite-driven bioreduction of toxic selenate [Se(VI)] remains largely unknown. This study demonstrates that Se(VI) is successfully bioreduced under anaerobic condition with the participation of pyrrhotite for the first time. Completely removal of Se(VI) was achieved at initial concentration of 10 mg/L Se(VI) and 0.56 mL/min flow rate in continuous column experiment with indigenous microbial consortium and pyrrhotite. Variation in hydrochemistry and hydrodynamics affected Se(VI) removal performance. Se(VI) was reduced to insoluble Se(0) while elements in pyrrhotite were oxidized to Fe(III) and SO42-. Breakthrough study indicated that biotic activity contributed 81.4 ± 1.07% to Se(VI) transformation. Microbial community analysis suggested that chemoautotrophic genera (e.g., Thiobacillus) could realize pyrrhotite oxidation and Se(VI) reduction independently, while heterotrophic genera (e.g., Bacillus, Pseudomonas) contributed to Se(VI) detoxification by utilizing metabolic intermediates generated through Fe(II) and S(-II) oxidation, which were further verified by pure culture tests. Metagenomic and qPCR analyses indicated genes encoding enzymes for Se(VI) reduction (e.g., serA, napA and srdBAC), S oxidation (e.g., soxB) and Fe oxidation (e.g., mtrA) were upregulated. The elevated electron transporters (e.g., nicotinamide adenine dinucleotide, cytochrome c) promoted electron transfer from pyrrhotite to Se(VI). This study gains insights into Se biogeochemistry under the effect of Fe(II)-bearing minerals and provides a sustainable strategy for Se(VI) bioremediation in natural aquifer.

Soil indigenous microorganisms alleviate soluble vanadium release from industrial dusts.

Vanadium-bearing dusts from industrial processes release abundant toxic vanadium, posing imminent ecological and human health concerns. Although the precipitation of these dusts has been recognized as the main source of soil vanadium pollution, little is known regarding the interrelationships between industrial dusts and soil inherent compositions. In this study, the interactions between dusts from vanadium smelting and soil indigenous microorganisms were investigated. Soluble vanadium (V) [V(V)] released from industrial dusts was reduced by 41.5 ± 0.39% with soil addition, compared to water leaching. Reducible fraction accounted for the highest proportion (55.1 ± 1.73%) of vanadium speciation in the resultant soils, while residual vanadium fraction increased to 83.7 ± 3.22% in the leached dusts. Functional genera (e.g., Aliihoeflea, Actinotalea) that transformed V(V) to insoluble vanadium (IV) alleviated dissolved vanadium release. Nitrate/nitrite reduction and glutathione metabolisms contributed to V(V) immobilization primarily. Structural equation model analysis indicated that V(V) reducers had significant negative impacts on soluble V(V) in the leachate. This first-attempt study highlights the importance of soil microorganisms in immobilizing vanadium from industrial dusts, which is helpful to develop novel strategies to reduce their environmental risks associated to vanadium smelting process.

Microbial selenate detoxification linked to elemental sulfur oxidation: Independent and synergic pathways.

Elevated selenium levels in the environment, with soluble selenate [Se(VI)] as the common chemical species, pose a severe threat to human health. Anaerobic Se(VI) bioreduction is a promising approach for selenium detoxification, and various organic/inorganic electron donors have proved effective in supporting this bioprocess. Nevertheless, autotrophic Se(VI) bioreduction driven by solid inorganic electron donors is still not fully understood. This work is the first to employ elemental sulfur [S(0)] as electron donor to support Se(VI) bioreduction. A batch trial with mixed culture demonstrated the feasibility of this bioprocess, with Se(VI) removal efficiency of 92.4 ± 0.7% at an initial Se(VI) concentration of 10 mg/L within 36 h. Continuous column tests showed that increased initial concentration, flow rate, and introduction of NO3--N depressed Se(VI) removal. Se(VI) was mainly bioreduced to solid elemental Se with trace selenite in the effluent, while S(0) was oxidized to SO42-. Enrichment of Thiobacillus, Desulfurivibrio, and Sulfuricurvum combined with upregulation of genes serA, tatC, and soxB indicated Se(VI) bioreduction was coupled to S(0) oxidation. Thiobacillus performed S(0) oxidation and Se(VI) reduction independently. Intermediate metabolites as volatile fatty acids, hydrogen and methane from S(0) oxidation were utilized by heterotrophic Se(VI) reducers for Se(VI) detoxification, indicative of microbial synergy.

Hydrodynamics- and hydrochemistry-affected microbial selenate reduction in aquifer: Performance and mechanisms.

Selenate [Se(VI)] with higher content in groundwater will be harmful for human beings. Hence, effective treatment for Se(VI) in aquifer should be conducted reasonably. Microbial reduction of Se(VI) to elemental selenium with weak movability and toxicity has attracted significant attention due to its high efficiency and no secondary contamination. However, hydrodynamic and hydrochemical influences with corresponding mechanisms during Se(VI) bioreduction are still not clear. In this study, influences of flow rate, initial Se(VI) and organic concentrations, coexisting nitrate were evaluated. Se(VI) removal efficiency and capacity reached 96.42 ± 6.82% and 41.28 ± 3.41 (g/m3·d) with flow rate of 0.56 mL/min, initial Se(VI) and chemical organic demand concentrations of 10 mg/L and 400 mg/L. Dechloromonas and Pseudomonas were presumably contributed to Se(VI) reduction, with upregulated serA and tatC genes. Solid Se0 was identified as the final product from Se(VI) reduction. These results will be beneficial for the further comprehending of Se(VI) remediation in aquifer.

Taoren-dahuang herb pair reduces eicosanoid metabolite shifts by regulating ADORA2A degradation activity in ischaemia/reperfusion injury rats.

ETHNOPHARMACOLOGICAL RELEVANCE: Peach kernel (taoren: TR) is the dried mature seed of peach, Prunus persica (L.) Batsch, which belongs to the Rosaceae family. Rhubarb (dahuang: DH) is the dried root and rhizome of rhubarb (Rheum palmatum L., Rheum officinale Baill., or Rheum tanguticum Maxim. ex Balf.). TR-DH (TD) is a traditional Chinese medicine herb pair that promotes blood circulation and removes blood stasis. In recent years, TD has shown definite benefits in the cardio-cerebrovascular system, but its specific mechanism is not very clear. AIM OF STUDY: The purpose of this study was to explore the mechanism by which TD affects cerebral ischaemia/reperfusion (I/R) injury and to optimize the mixture ratio. METHODS: The affected metabolic pathways in rat brain tissues after I/R were analysed by network pharmacology and verified with animal pharmacological experiments. RESULTS: TD had a certain therapeutic effect on cerebral I/R injury. TD with a TR:DH ratio of 1:1 had the best therapeutic effect. Metabolic pathway analysis showed that the protective mechanism of TD against I/R injury involves mainly regulation of brain tissue ADORA2A protein levels and action on the arachidonic acid (AA) pathway. CONCLUSION: TD can ameliorate cerebral I/R injury by regulating ADORA2A degradation in the AA metabolic pathway to attenuate AA metabolic dysfunction and the inflammatory response.

Simultaneous purifying of Hg0, SO2, and NOx from flue gas by Fe3+/H2O2: the performance and purifying mechanism.

Hg0, SO2, and NOx result in heavily global environmental pollution and serious health hazards. Up to now, how to efficiently remove mercury with SO2 and NOx from flue gas is still a tough task. In this study, series of high oxidizing Fenton systems were employed to purify the pollutants. The experimental results showed that Fe3+/H2O2 was more suitable to purify Hg0 than Fe2+/H2O2 and Cu2+/H2O2. The optimal condition includes Fe3+ concentration of 0.008 mol/L, Hg0 inlet concentration of 40 µg/m3, solution temperature of 50 °C, pH of 3, H2O2 concentration of 0.7 mol/L, and O2 percentage of 6%. When SO2 and NOx were taken into account under the optimal condition, Hg0 removal efficiency could be enhanced to 91.11% while the removal efficiency of both NOx and SO2 was slightly declined, which was consistent to the analysis of purifying mechanism. The removal efficiency of Hg0 was stimulated by accelerating the conversion of Fe2+ to Fe3+, which resulted from the existence of SO2 and NOx. The results of this study suggested that simultaneously purifying Hg0, SO2, and NOx from flue gas is feasible.

Purification of Hg0 from flue gas by wet oxidation method and its mechanism: a review.

The vast majority of Hg2+ can be removed while elemental mercury (Hg0) can hardly be removed due to its characteristic of high volatility and insolubility in water. Till now, how to oxidize Hg0 to Hg2+ is the key for the purification of Hg0, especially when there are others pollutants, such as HCl, SO2, and NOx. In this review, the method and mechanism of Hg0 purification from flue gas by H2O2, KMnO4, NaClO2, and O3 are reviewed comprehensively. It is concluded that the oxidation of Hg0 mainly depends on the electronic supply efficiency from the solution. The Fenton reagent, composed of H2O2 and metal cations, is superior to O3 and the solution of KMnO4 and NaClO2. Moreover, HCl, SO2, and NOx in the flue gas can influence the oxidation and purification mechanism of Hg0. It is found that HCl in flue gas had obvious auxo-action on the oxidation of mercury, and SO2 and NOx have different effects on the oxidation of Hg0 with the change of compositions and concentration of pollutants in the flue gas. In general, SO2 and NOx can slightly promote the oxidation of Hg0 due to the synergistic effect.