Oxygen Concentration Research Articles

Effect of high-flow nasal and buccal oxygenation on safe apnea time in children with open mouth: A randomized controlled trial.

High-flow nasal oxygenation is reported to prolong duration of apnea while maintaining adequate oxygen saturation with the mouth closed. Also, buccal oxygenation is known to have similar effects in obese adults. We compared the effect of these two methods on prolongation of acceptable apnea time in pediatric patients with their mouth open. Thirty-eight patients, aged 0-10 years were randomly allocated to either the high-flow nasal oxygenation group (n = 17) or the buccal oxygenation group (n = 21). After induction of anesthesia including neuromuscular blockade, manual ventilation was initiated until the expiratory oxygen concentration reached 90%. Subsequently, ventilation was paused, and the patient's head was extended, and mouth was opened. The HFNO group received 2 L·min-1·kg-1 of oxygen, and the BO group received 0.5 L·min-1·kg-1 of oxygen. We set a target apnea time according to previous literature. When the apnea time reached the target, we defined the case as "success" in prolongation of safe apnea time and resumed ventilation. When the pulse oximetry decreased to 92% before the target apnea time, it was recorded as "failure" and rescue ventilation was given. The success rate of safe apnea prolongation was 100% in the high-flow nasal oxygenation group compared to 76% in the buccal oxygenation group (p = .04). Oxygen reserve index, end-tidal or transcutaneous carbon dioxide partial pressure, and pulse oximetry did not differ between groups. High-flow nasal oxygenation is effective in maintaining appropriate arterial oxygen saturation during apnea even in children with their mouth open and is superior to buccal oxygenation. Buccal oxygenation may be a good alternative when high-flow nasal oxygenation is not available.

Facile One Pot Synthesis of Hybrid Core-Shell Silica-Based Sensors for Live Imaging of Dissolved Oxygen and Hypoxia Mapping in 3D Cell Models.

Fluorescence imaging allows for noninvasively visualizing and measuring key physiological parameters like pH and dissolved oxygen. In our work, we created two ratiometric fluorescent microsensors designed for accurately tracking dissolved oxygen levels in 3D cell cultures. We developed a simple and cost-effective method to produce hybrid core-shell silica microparticles that are biocompatible and versatile. These sensors incorporate oxygen-sensitive probes (Ru(dpp) or PtOEP) and reference dyes (RBITC or A647 NHS-Ester). SEM analysis confirmed the efficient loading and distribution of the sensing dye on the outer shell. Fluorimetric and CLSM tests demonstrated the sensors' reversibility and high sensitivity to oxygen, even when integrated into 3D scaffolds. Aging and bleaching experiments validated the stability of our hybrid core-shell silica microsensors for 3D monitoring. The Ru(dpp)-RBITC microparticles showed the most promising performance, especially in a pancreatic cancer model using alginate microgels. By employing computational segmentation, we generated 3D oxygen maps during live cell imaging, revealing oxygen gradients in the extracellular matrix and indicating a significant decrease in oxygen level characteristics of solid tumors. Notably, after 12 h, the oxygen concentration dropped to a hypoxic level of PO2 2.7 ± 0.1%.

Research on the mechanism of motor muscle control based on optical EEG images

The study of motor muscle control mechanisms can improve rehabilitation therapy and human-computer interaction technology. The limitations of traditional electroencephalography (EEG) limit the comprehensive understanding of motor muscle control mechanisms. Therefore, this study aims to explore the mechanism of motor muscle control based on optical EEG images, in order to expand the understanding of the process of motor control. The study selected optical EEG imaging technology as the main data acquisition tool. Optical EEG images have higher spatiotemporal resolution and can provide more detailed neural activity information. This technology combines optical imaging with EEG images to obtain spatiotemporal information of brain activity in a short period of time. The device is composed of multiple optical sensors and can measure blood oxygen concentration and neuronal activity in the cerebral cortex. Preprocess EEG image data using image processing and signal processing techniques, then use computational methods and algorithms to detect activated regions, and evaluate their relationships using correlation analysis and statistical methods. By comparing EEG image data and motor muscle activity data under different motor tasks. The research results show that optical EEG imaging technology can provide more detailed information on brain neural activity and accurately capture the activity patterns of different motor muscles. These results provide new perspectives and methods for further studying the control mechanisms of motor muscles.

Hypoxia-induced Factor-1α and its Role in Endometrial Cancer.

The transcription factor hypoxia inducible factor-1 (HIF-1) is one of the main factors in the cell's response to a lack of oxygen. Hypoxia is a typical feature of a growing cancerous tumor. Increased activity of HIF-1 is observed in many cancers, including endometrial cancer. HIF-1 functions as a heterodimer consisting of three subunits HIF-1α, HIF-2α, and HIF-3α and one subunit β. HIF-1α is a subunit that is sensitive to oxygen concentration and is constitutively expressed. The HIF-1α gene is highly polymorphic. Literature data suggest that single nucleotide polymorphisms (SNPs) of the HIF-1α gene may be risk factors for endometrial cancer. A better understanding of the molecular mechanisms of cancer development, progression and prognosis, including the role of SNPs, could lead to the development of new anti-cancer therapies.

Evaluation of Probiotics Ability to Enhance Population Density, Growth Rate, and Neonates Production of Moina micrura in Different Environmental Parameters

Salinity, light intensity, and oxygen concentration are key environmental factors that significantly affect biological processes and the composition and dispersion of Moina biomass. Evaluating the effectiveness of probiotic enrichment in improving population density, growth rate, and neonate production can provide valuable details on the effectiveness of probiotics in enhancing the resilience and viability of Moina micrura under suboptimal circumstances. The purpose of this research project is to assess the efficacy of two probiotics, Bacillus pocheonensis strain S2 and Lysinibacillus fusiformis strain A1, in improving the population density, growth rate, and reproductive output in M. micrura across various environmental conditions. Moina micrura were treated with each probiotic at a volume of 5 x 105 CFU/ml under different levels of salinity (0, 2, 4, and 6 ppt), light intensity (800, 1,000, 1,500, and 2,000 lux), and oxygen concentration (80, 70, 60, and 50%). The results indicated that M. micrura treated with L. fusiformis A1 at 0 ppt attained the highest population density (6 ± 0.90 Ind./ml), growth rate (0.355 ± 0.030 µ), and number of offspring production (5 ± 0.75 Ind./ml). The highest point of population density (5 ± 0.07 Ind./ml), growth rate (0.381 ± 0.002 µ) and number of offspring (7 ± 0.41 Ind./ml) of M. micrura were obtained while treated with B. pocheonensis S2 at light intensity of 1,500 lux. Similarly, the highest population density (5 ± 0.60 Ind./ml), growth rate (0.365 ± 0.190 µ), and offspring production (2 ± 0.25 Ind./ml) of M. micrura were observed during enrichment with B. pocheonensis S2 at 70% oxygen concentration. Therefore, these results suggested that the optimum conditions for enriching M. micrura with B. pocheonensis S2 are salinity of 0 ppt, 70% oxygen concentration, and a light intensity level of 1,500 lux.

Investigating how oxygen levels and particle size impact the thermodynamics of low temperature coal oxidation: A case study using weakly caking coal

Oxygen concentration and particle size play critical roles in the combustion of coal. Notably, the low temperature oxidation stage is considered pivotal for coal spontaneous combustion (CSC). In this study, we examined the exothermic oxidation of low-temperature weakly caking coal. We used a C80 microcalorimeter to assess the impact of different oxygen concentrations and particle sizes. For weakly caking coal during low-temperature oxidation, the heat flow (HF) curve decreases as oxygen concentration drops. The characteristic temperature increases, and the HF curve shows a noticeable lag. Under identical external conditions, decreasing the particle size of coal results in a reduced minimum floating coal thickness, lowers the oxygen concentration needed for CSC, increases the upper-limit of air leakage intensity, and makes the coal more susceptible to CSC. Reducing the particle size significantly increases the exothermic heat release during low-temperature oxidation, leading to a higher risk of CSC. These research results not only deepen the understanding of the law of coal spontaneous combustion, but also provide a scientific basis for improving the technical level of coal spontaneous combustion fire prevention and control.

Whole transcriptome sequencing revealed the gene regulatory network of hypoxic response in yak Sertoli cells

Yaks live in the Qinghai-Tibet Plateau for a long time where oxygen is scarce, but can ensure the smooth development of testis and spermatogenesis. The key lies in the functional regulation of the Sertoli cells under hypoxia. In this study, we sequenced yak Sertoli cells cultured in normal oxygen concentration (Normoxia) and treated with low oxygen concentration (Hypoxia) by whole transcriptomics, and screened out 194 differentially expressed mRNAs (DEmRNAs), 934 differentially expressed LncRNAs (DELncRNAs) and 129 differentially expressed miRNAs (DEmiRNAs). GO and KEGG analysis showed that these differential genes were mainly concentrated in PI3K-AKT, MAPK, RAS, and other signaling pathways, and were associated with glucose metabolism, tight junction, steroid hormone synthesis, cell fusion, and immunity of yak Sertoli cells. We constructed the gene interaction network of yak Sertoli cells in hypoxia and screened out the relationship pairs related to glucose metabolism and tight junction. The results suggested that the changes in energy metabolism, tight junction, and immune regulation of yak Sertoli cells under hypoxia might provide favorable conditions for spermatogenesis. This study provides data for further study on the role of non-coding RNA in testis development and spermatogenesis of yak.

Fish production, water quality, and the role of nitrification as an ammonia removal process in intensively aerated hybrid catfish ponds

AbstractSix 0.1‐ha earthen ponds with 45 kW/ha of aeration capacity were stocked with hybrid catfish (Ictalurus punctatus x I. furcatus) ranging from 15,000 to 90,000 fish ha−1 in 15,000 fish ha−1 increments to analyze the effect of nitrogen loading on ammonia accumulation and fish production. Minimum dissolved oxygen (DO) concentration was maintained above 3.0 mg O2 L−1 to prevent hypoxia‐induced appetite reduction. Stocking density did not impact survival but decreased average fish harvest weight and increased food conversion ratio (FCR). Gross production increased with stocking density and ranged from 7249 to 35,674 kg ha−1. Average total (TAN) and un‐ionized ammonia (NH3) were not different among stocking densities despite greater nitrogen inputs in ponds with higher feeding rates. Nitrite () and nitrate () concentrations were significantly higher in ponds with higher stocking densities, suggesting that nitrification increased with nitrogen loading. Phytoplankton assimilation of ammonia is the primary ammonia removal process in traditional catfish ponds with modest fish densities and feeding rates. However, in intensively aerated ponds with high feeding rates, nitrification can become an important process for ammonia removal. These data indicate that small earthen hybrid catfish ponds with high aeration capacities can increase catfish production without ammonia accumulating.

Formulation of a stable diesel microemulsion using eco-friendly ionic liquids and investigation of particle size and fuel properties as an alternative fuel

Ecofriendly ionic liquids (ILs) were synthesized through amidation of ricinoleic acid, the main fatty acid in castor oil, followed by a quaternization reaction to solubilize ethanol in IL/diesel blends at different ratios. As a result, stable and highly renewable, low viscous microemulsion biofuels with high oxygen content were prepared. The prepared fuel samples combine the advantages of green ionic liquids and microemulsion properties. The chemical structures of ILs were confirmed with the aid of NMR and FTIR spectroscopy. DLS analysis revealed that the ethanol particles ranged in size from 8 to 18.1 nm in all samples. As ILs ratios decrease in microemulsion from 37 to 69%, the ethanol particle sizes increase from 10 to 25%. Ethanol shows good solubilization in diesel and IL-1 is more effective than IL-2 in ethanol solubilization at low percentages of ethanol due to more oxygen atoms besides three hydroxyl groups. The ternary phase diagram indicated that the microemulsion area in the case of using IL-1 is larger than that of IL-2. The fuel properties of the prepared microemulsions are nearly close to those of neat diesel and fall within the permitted range of ASTM D975. The viscosity and density values at low ratios of ILs are found to be very close to the values of the neat diesel at different temperatures. The prepared samples show a slight decrease in cetane number and heating value compared to diesel. However, they have improved flash points, cloud points, sulfur content, and acid value. The particle sizes were checked every week and the prepared samples showed high stability with the aid of the synthesized ILs. Moreover, the prepared microemulsions stayed in a transparent appearance for more than a year and no phase separation was observed.

Composition changes and micro explosion characteristics of burning droplets formed by combustion of micrometer iron wires

To analyze the composition changes during the combustion process of iron droplets using the energy balance equation, iron wires with diameters of tens of micrometers were burned to form temperature-stable iron droplets with diameters of hundreds of micrometers. High-speed two-color imaging pyrometry was employed to measure the spatially resolved surface temperature and volume changes of the droplets under varying oxygen concentrations. Experimental results showed that the droplet's temperature stabilized between the melting points of wüstite and iron. Quantitative analysis revealed the presence of bubbles within the droplets, primarily sourced from the oxidation of carbon in the iron to carbon dioxide. Simulation results of the droplet combustion process revealed that at the experimental combustion temperatures, the transport of oxygen in molten iron oxides was the rate-limiting step. The gas responsible for micro-explosions originates from the release of dissolved excess oxygen before the solidification of molten iron oxides, with rough estimates indicating that the mass of the released gas is only 0.02% to 0.03% of the droplet mass. The impact of reaction kinetics parameters on the simulation results, as well as the role of the micro-explosion mechanism in the self-sustained combustion of iron wires, were also discussed.

Minimal transcriptional regulation of horizontally transferred photosynthesis genes in phototrophic bacterium Gemmatimonas phototrophica.

Horizontal gene transfer is one of the main mechanisms by which bacteria acquire new genes. However, it represents only the first step as the transferred genes have also to be functionally and regulatory integrated into the recipient's cellular machinery. Gemmatimonas phototrophica, a member of bacterial phylum Gemmatimonadota, acquired its photosynthesis genes via distant horizontal gene transfer from a purple bacterium. Thus, it represents a unique natural experiment, in which the entire package of photosynthesis genes was transplanted into a distant host. We show that G. phototrophica lacks the regulation of photosynthesis gene expressions in response to oxygen concentration and light intensity that are common in purple bacteria. This restricts its growth to low-light habitats with reduced oxygen. Understanding the regulation of horizontally transferred genes is important not only for microbial evolution but also for synthetic biology and the engineering of novel organisms, as these rely on the successful integration of foreign genes.

Establishment of NK Cell Natural Immunotherapy for Cancer Prevention and Treatment Using the Natural Terpenes Derived from Forest Phytoncide

The active ingredient of forest phytoncide has many remarkable biological activities, especially in the aspect of anti-tumor. It can activate NK cells, increase the number of NK cells and the expression level of anti-cancer protein in NK cells, induce the self-apoptosis of cancer cells, and help the human body effectively complete the cellular immune anti-cancer mechanism. If we replace ordinary air with natural forest air as a new pressurizing medium and input it into the hyperbaric oxygen chamber, after being processed by hyperbaric oxygen chamber oxygen production technology, the high pressure oxygen of forest phytoncide is generated. At this time, the high pressure oxygen inhaled into the body is different from natural forest air or ordinary air. The fundamental difference is that the high pressure oxygen inhaled into the body at this time contains both high concentration of oxygen and high concentration of phytoncide, moreover the phytoncide concentration and oxygen concentration are much higher than the natural forest air or ordinary air. After it is inhaled by the human body into the alveoli, it can reach the peripheral blood through the pulmonary circulation and systemic circulation, and the high concentration of the active component terpene of phytoncide has an opportunity to directly contact NK cells and fully play the biological activity of activating NK cells. The high pressure oxygen that enters the alveoli simultaneously with phytoncide gas also passes through the pulmonary and systemic circulation, reaches the peripheral blood, Oxygen is released from the oxygenated hemoglobin, passes through the cell membrane and enters the mitochondria in the cells to provide sufficient energy for the physiological activities of NK cells. By applying this basic principle, we can establish a satisfactory NK cell natural immunotherapy for cancer prevention and treatment that can be accepted by humanity in the long run.

The influence of oxygen partial pressure on the properties of sputtered vertical NiO/β-Ga2O3 heterojunction diodes

In this work we present studies on the influence of oxygen partial pressure on the properties of sputtered vertical NiO/β-Ga2O3 heterojunction diodes. Obtained results shows substantial effect of oxygen partial pressure on the electrical properties of NiO/β-Ga2O3 heterojunction diodes. The diodes with NiO layers deposited in pure Ar shows Schottky-like I-V characteristics with low ideality factor of 1.05 and barrier height of 1.27 eV as well as low turn-on voltage close to 1V. On the other hand, diodes with NiO layer deposited in oxygen containing atmosphere shows typical p-n diode characteristics. The best electrical characteristics i.e. low on-state resistance of 2.85 mΩcm2, lack of defects and low ideality factor down to 1.07 at RT along with high breakdown voltage close to 900V without any junction termination, were obtained for diodes with NiO layers deposited at 50 % oxygen content. We have demonstrated that by optimization of oxygen partial pressure, the properties of NiO/β-Ga2O3 heterojunction diodes can be tuned and excellent electrical performance in terms of low-on state resistance, high breakdown voltage, low-leakage current and low ideality factor, can be obtained.

Enhancing the electrochemical performance of semicoke‐based hard carbon anode through oxidation‐crosslinking strategy for low‐cost sodium‐ion batteries

AbstractSemicoke, a coal pyrolysis product, is a cost‐effective and high‐yield precursor for hard carbon used as anode in sodium‐ion batteries (SIBs). However, as a thermoplastic precursor, semicoke inevitably graphitizes during high‐temperature carbonization, so it is not easy to form the hard carbon structure. Herein, we propose an oxidation‐crosslinking strategy to realize fusion‐to‐solid‐state pyrolysis of semicoke. The semicoke is first preoxidized using a modified alkali‐oxygen oxidation method to enrich its surface with carboxyl groups, which are localization points and the cross‐linking reactions occur with citric acid to build the semicoke precursor with homogeneous and abundant ‐C‐(O)–O‐ groups (up to 21 at% oxygen content). The ‐C‐(O)–O‐ groups effectively prevent the rearrangement of carbon microcrystals in semicoke during carbonization, resulting in the formation of an abundant pseudographite structure with larger carbon interlayer spacing and micropores. The optimized semicoke‐based hard carbon shows both a high initial Coulombic efficiency of 81% and a specific capacity of 307 mAh g−1, with low‐voltage plateau capacity increased to 2.5 times, compared to that of the unmodified semicoke carbon. By the combination of detailed discharge curves and in situ X‐ray diffraction analysis, the plateau capacity of semicoke‐based hard carbon is mainly derived from interlayer intercalation of Na+ ion. The proposed oxidation‐crosslinking strategy can contribute to the usage of low‐cost and high‐performance hard carbons in advanced SIBs.

Industrial equipment optimization for combustion performance enhancement: a real-world case study

To address the issue of high NOx emission from the combustion chamber, this work optimized the industrial machine structure to enhance the combustion performance. The analysis results indicated that the flue gas recirculation (FGR) could effectively reduce the combustion temperature and the distribution of high-temperature regions in the machine chamber, thereby suppressing NOx formation without affecting the gas velocity inside the chamber. Based on the simulation analysis, the FGR technology was applied to modifying the machine structure and evaluated the modification effect in real-world application. It is found that after adding FGR, the oxygen content at the furnace outlet decreased from 13.8% to 10.5%, the NOx emission from the furnace decreased from 80 mg/m3 to 18 mg/m3, and the natural gas consumption decreased by more than 17%. These results demonstrate a significant impact on energy saving and emission reduction after optimizing the machine structure, which can provide a reference basis for subsequent researchers in this field.

ГИПОКСИЯ И АНОКСИЯ В ГДАНЬСКОЙ ВПАДИНЕ БАЛТИЙСКОГО МОРЯ В 2021–2023 гг.

The central part of Gdansk Deep experienced summer-autumn dissolved oxygen minima within 2021–2023, while along the periphery of the Deep no seasonality was detected. Intrusions of transformed North Sea waters with a low oxygen content can partially aerate the bottom layer and cause anoxic waters to detach from the bottom. In the near-slope southeastern part of the Deep, in autumn-winter storm conditions, amplitude vertical fluctuations in oxygen concentration can occur – from the rise of hypoxic waters above the halocline, to the complete elimination of hypoxia as a result of near-slope downwelling, which acts as an “oxygen pump”. The hydrological and hydrochemical characteristics of intrusions of transformed North Sea waters penetrating into the Gdansk Basin and influencing the dynamics of the nepheloid layer of biogeochemical origin, arising at the boundary of oxidizing and reducing conditions, have been clarified.

The Comparative Impact of Liberal Versus Conservative Oxygenation in Critically Ill COVID-19 Patients: A Retrospective Study.

Objectives Whether a higher or lower partial pressure of oxygen (PaO2) could impact outcomes in patients with coronavirus disease 2019 (COVID-19) remains a matter of debate. So, we planned this retrospective analysis to determine if a higher or lower partial pressure of oxygen in blood had any effect on outcomes in COVID-19 patients. Material and method The records of COVID-19 patients from the beginning of 2020 to the end of 2022 were scanned. Patients were sub-grouped into two groups based on the partial pressure of oxygen (PaO2) values on arterial blood gas (ABG), i.e., high PaO2group,PaO2 value of 80-100 mm Hg, and low PaO2group,PaO2 value of 60-80 mm Hg for the first 48 hours after the initiation of oxygenation and/or mechanical ventilation. The two groups were compared in terms of partial pressure of oxygen in arterial blood to the fraction of inspiratory oxygen (FiO2) concentration (P/F ratio), Sequential Organ Failure Assessment (SOFA) score at presentation and after 48 hours, and clinical outcomes, including mortality, time of mortality, extubation, acute kidney injury (AKI), and change in Glasgow Coma Scale (GCS). Results SOFA score was significantly higher in the low PaO2 group as compared to the high PaO2 group both at baseline (4.59 {1.79} versus 5.51 {1.15}; p-value: 0.005) and at 48 hours (3.06 {1.39} versus 5.11 {2.13}; p-value: 0.007). However, the change in SOFA score over 48 hours did not achieve statistical significance (-1.000 {0.97} versus 0.53 {2.34}; p-value: 0.257). Out of a total of 37 patients, 21 patients died in the high PaO2 group, while 18 patients died in the low PaO2 group. Conclusion Our study highlights that targeting either low or high arterial oxygen content while considering oxygen therapy for COVID-19 patients did not significantly alter the outcomes.

Promoting metal oxides–zeolite electron interaction on MnCeOx/HY catalyst for boosting nitrogen oxides reduction

The MnOx-CeO2 metal oxides are considered as promising alternative catalysts for selective catalytic reduction with NH3 (NH3-SCR) to remove NOx due to its excellent low temperature performance. However, their strong oxidative ability can lead to NH3 over-oxidation, narrowing the active temperature range and reducing N2 selectivity. Moreover, their weak surface acidity hampers medium to high-temperature activity and alkali metal resistance. Hence, in this study, MnCeOx metal oxides were coupled with HY zeolite to create MnCeOx/HY, demonstrating excellent NH3-SCR performance. The high dispersion of metal oxides on the zeolite surface and their close integration promoted strong electron interaction, effectively reducing oxygen vacancies and surface adsorbed oxygen concentrations. Consequently, the oxidative ability of active metal oxides was appropriately weakened, suppressing undesirable side reactions. MnCeOx/HY also notably suppressed NO adsorption and nitrate formation, promoting the catalytic reaction solely through the E-R mechanism and enhancing N2 selectivity. The abundant strong acid sites on the zeolite surface facilitates NH3 adsorption at moderate to high temperatures, notably expanding the active temperature window. Furthermore, the acid sites of HY zeolite serve as sacrificial sites, preferentially reacting with alkali metals, thus exhibiting excellent resistance to alkali metal poisoning on MnCeOx/HY. Combining with the DFT results, the structure-activity relationships in this study also reveal the importance of the effective synergy between acid sites and redox sites for optimal catalytic performance, offering valuable insights into the development of highly active and alkali-resistant denitrification catalysts.

Enhancing the performance of microalgal-bacterial systems with sodium bicarbonate: A step forward to carbon neutrality of municipal wastewater treatment

The microalgal-bacterial granular sludge (MBGS) process, enhanced with sodium bicarbonate (NaHCO3), offers a sustainable alternative for wastewater treatment aiming for carbon neutrality. This study demonstrates that NaHCO3, which can be derived from the flue gases and alkaline textile wastewater, significantly enhances pollutant removal and biomass production. Optimal addition of NaHCO3 was found to achieve an inorganic-to-organic carbon ratio of 1.0 and a total carbon-to-nitrogen ratio of 5.0. Metagenomic analysis and structural equation modeling showed that NaHCO3 addition increased dissolved oxygen concentrations and pH levels, creating a more favorable environment for key microbial communities, including Proteobacteria, Chloroflexi, and Cyanobacteria. Confocal laser scanning microscopy further confirmed enhanced interactions between Cyanobacteria and Proteobacteria/Chloroflexi, facilitating the MBGS process. These microbes harbored functional genes (gap2, GLU, and ppk) critical for removing organics, nitrogen, and phosphorus. Carbon footprint analysis revealed significant reductions in CO2 emissions by the NaHCO3-added MBGS process in representative countries (China, Australia, Canada, Germany, and Morocco), compared to the conventional activated sludge process. These findings highlight the effectiveness of NaHCO3 in optimizing MBGS process, establishing it as a key strategy in achieving carbon-neutral wastewater treatment globally.

Multiple effects of iron oxides on the adsorption and oxidation of dissolved organic matter by manganese oxides

Adsorptive fractionation and oxidation of dissolved organic matter (DOM) on manganese (Mn) oxide surfaces alter the molecular composition and stability of DOM, but the impact of iron (Fe) oxides on the coupled adsorption-oxidation processes of DOM by Mn oxides is largely unknown. In this study, the underlying mechanisms of molecular transformation of DOM on birnessite (Bir) in the presence of ferrihydrite (Fh), with varying Fh/Bir mass ratios, were investigated at both molecular levels and microscopic scales with a suite of characterization techniques, including Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) and spherical aberration corrected scanning transmission electron microscopy (Cs-STEM). We found that higher Fh/Bir mass ratio impeded the adsorption of DOM by birnessite and the reductive dissolution of birnessite to release dissolved Mn, and the impediment on the reductive dissolution of birnessite was proportional to Fh/Bir mass ratio. Overall, during the interactions of DOM with ferrihydrite and birnessite, phenolic compounds were preferentially adsorbed by Fe and Mn minerals, and compounds with higher oxygen contents and polymeric substances were formed. FT-ICR-MS analysis further suggested that higher Fh/Bir mass ratio inhibited the occurrence of aromatic ring-opening and carboxylation of substituted groups on aromatic rings, but promoted polymerization of phenolic compounds. Cs-STEM analysis revealed that DOM distributions on ferrihydrite, birnessite, and their mixtures were regulated by their microscopic structures and reactivity. Compared with aromatic carbon (C), carboxylic and phenolic C were more likely to associate with birnessite. Our results highlighted the significance of organo-mineral associations with the mixed minerals in regulating the distribution and reactivity of organic C. This study has provided molecular evidences for molecular transformation of DOM mediated by both Mn and Fe oxides, which contributed to advancing our understanding on coupled reactions of organic C at the mineral–water interfaces in the environment.