Oxidation-reduction Potential Research Articles

Study on the detection of active components in plasma-activated water and its storage stability

ABSTRACT In this study, the impact of different discharge time, discharge power, and storage time on the pH, oxidation-reduction potential (ORP), electrical conductivity (EC), H2O2, and the physicochemical properties and the stability at 4°C were evaluated. With the increase of plasma discharge time and discharge power, all the values increased except pH value. There were no significant changes in the values of pH, ORP, and EC for 30 days storage at 4°C (p > 0.05). The concentrations of NO3 −, NO2 −, and H2O2 exhibited significant changes (p < 0.05) after stored for 5 days. The plasma discharge time and discharge power showed significant effects on the physicochemical properties and activity of PAW. Moreover, the concentrations of NO3 − and NO2 − significantly affected the storage stability of PAW at 4°C.

Synthesis of Zn2+:LaMnO3 perovskites nanoparticles by facile co-precipitation approach: Physicochemical characteristics and supercapacitor application

This work has examined the impact of Zn2+ on the crystal architecture and electrochemical functionality of LaMnO3 perovskite nanoparticles. Crystalline parameters of the as-prepared samples were analyzed by X-ray Diffraction studies (XRD). Fourier transform infrared (FT-IR) measurements are utilized to detect the functional groups present in the sample. Raman spectroscopy technique was used to analyze the nature of the chemical bonds in the prepared material. The shape and elemental content of the produced nanomaterials were determined using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDAX). Brunauer-Emmett-Teller (BET) technique is used to study the porosity and surface area of the material. Electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and galvanostatic charge/discharge (GCD) is employed to study the surface resistivity, oxidation–reduction potential and super capacitance efficiency of the prepared electrode material.

Diagnostic value of oxidation-reduction potential for male infertility: a systematic review and meta-analysis.

In the last few years, studies have initially confirmed the diagnostic significance of oxidation-reduction potential (ORP) in male infertility patients. In this article, we used meta-analysis to clarify the role of ORP in the diagnosis of male infertility. PubMed, Embase, Web of Science, and Cochrane Library were searched by computer for relevant published literature. Quality assessment of the included literature was performed by Quality Assessment of Diagnostic Accuracy Studies (QUADAS) scale. Heterogeneity analysis of included studies was conducted using Metadisc 1.4 and Stata 12.0, and effective models for quantitative synthesis were selected based on heterogeneity results; the sensitivity and specificity of the synthesis were obtained using the software, and in order to reduce the effects of heterogeneity and thresholds, the information of sensitivity and specificity was integrated. We used the subject receiver operating characteristic (SROC) curve, area under the curve (AUC) and Q* index for comprehensive evaluation. Seven papers were eventually included in the study, and the results showed that ORP had a sensitivity of 0.81 [95% confidence interval (CI): 0.80-0.82] and specificity of 0.66 (95% CI: 0.63-0.69), an AUC of 0.8 and a Q* index of 0.74 for the diagnosis of male infertility. ORP has high sensitivity and specificity for diagnosing male infertility.

Improving the transfer of dissolved oxygen in a biological Fe2+ oxidation process using a venturi jet as an intensive aeration system

The low bio-production of Fe3+ as a leaching agent is one of the main limitations to implementing industrial bio-processes at feasibility conditions. The main limitation of the bio-oxidation process of Fe2+ is the low oxygen transfer to the aqueous phase because of the low oxygen solubility. This study assesses the effectiveness of the venturi jet as an innovative and intensive aeration device for overcoming the oxygen limitation in a continuous ferrous oxidation process in a fixed-bed reactor with immobilized acidithiobacillus ferrooxidans, in contrast to the conventional diffuser aeration device. Firstly, the influence of the airflow and the influence of the medium concentration were determined for the following parameters for both aeration devices; Volumetric mass transfer coefficient (kLa), Standard Oxygen Transfer Rate (SOTR), Standard Aeration Efficiency (SAE), and Standard Oxygen Transfer Efficiency (SOTE). Then, both aeration devices were compared in a continuous bio-oxidation process in an up-flow packed bio-reactor (UFPB). The system performance was assessed by monitoring temperature, pH, oxidation-reduction potential, and dissolved oxygen concentration for 69 days. Findings displayed that when aerating with the diffuser, the ferrous oxidation rate was restricted by the low dissolved oxygen availability, being about 1 ppm (1 mg L−1). Under these oxygen-limiting conditions, the maximum ferrous (Fe2+) oxidation rate was 9.09 g L−1 h−1. However, when aerating with the venturi jet, the dissolved oxygen concentration increased up to 2.70 mg L−1, achieving a maximum of 29.11 g L−1 h−1. So, this study has demonstrated that the change in the aeration device has resulted in an improvement in the process, achieving a 3.5-fold increase in the oxidation rate. Furthermore, the venturi jet offered additional advantages over the diffuser, such as requiring less power to deliver the same amount of air, being unaffected by jarosite precipitates, and not requiring a supply of compressed air.

Anaerobic co-digestion of food waste and excess sludge by humus composites: Characteristics and microbial community structure

Volatile fatty acids (VFA) produced during the anaerobic co-digestion (Co-AD) an Manual removal of impurities such as bones, fish spines, napkins, etc., after collection at the food waste collection sited hydrolysis of food waste (FW) and excess sludge (ES) are important factors affecting the stability of the digestion and biogas production. This study aimed to use humus composites (HS) to mediate the Co-AD system of FW and ES, investigate their effects on VFA conversion, and analyze the microbial community structure using high-throughput sequencing technology to reveal the mechanism of action of HS in mediating the Co-AD system from a microbial perspective. The amount of HS was positively correlated with the accumulation of VFA produced by the hydrolysis of co-digested substrates, and in the Co-AD system with 5.00 g/L HS, the accumulation of VFA increased by approximately 1.1 times, whereas the pH and oxidation reduction potential of the system tended to be in the benign range, offering a favoring condition for enhancing the stability of the system. The biogas production increased by 46.3 % compared with that of the blank group. HS significantly increased the relative abundance values of Synergistota, a mutualistic symbiont with acetic acid-producing bacteria, and Proteobacteria, a mutualistic symbiont with methanogenic bacteria, thus promoting VFA conversion and strengthening the Co-AD efficacy of FW and ES. This study provides a simple and effective method to improve the Co-AD efficacy of FW and ES, as well as a new approach for the anaerobic resource treatment of other organic solid wastes.

Physical and chemical characteristics of plasma-activated water generated by hybrid dielectric barrier discharge and gliding arc discharge

This research explores the synergistic application of Dielectric Barrier Discharge (DBD) and Gliding Arc Plasma Jet (GAPJ) in a Hybrid Plasma Discharge (HPD) setup for enhanced water activation. The HPD system demonstrated balanced and sustained generation of reactive oxygen and nitrogen species (RONS), maintaining efficiency at higher specific input energy (SIE) values. Comparative analyses with DBD and GAPJ systems highlighted the superior performance of the HPD system in generating RONS and modifying water’s molecular structure. Key observations included a decrease in water’s pH and an increase in oxidation-reduction potential, total dissolved solids, and conductivity, stabilizing beyond 5 l min−1 airflow and 10 min of treatment. UV−Vis spectroscopy identified nitrites, nitrates, hydrogen peroxide, and nitrous acid, while Raman spectroscopy captured shifts in vibrational modes, particularly in librational and O–H stretching bands. These changes correlated with alterations in reactive species concentrations and pH levels. Overall, the HPD system emerged as a versatile and efficient approach for generating plasma-activated water, suitable for applications in microbial deactivation, surface sterilization, and electrocatalytic process optimization, offering stable and continuous production of reactive species across a range of SIE values.

Mapping reservoir water quality from Sentinel-2 satellite data based on a new approach of weighted averaging: Application of Bayesian maximum entropy

In regions like Oman, which are characterized by aridity, enhancing the water quality discharged from reservoirs poses considerable challenges. This predicament is notably pronounced at Wadi Dayqah Dam (WDD), where meeting the demand for ample, superior water downstream proves to be a formidable task. Thus, accurately estimating and mapping water quality indicators (WQIs) is paramount for sustainable planning of inland in the study area. Since traditional procedures to collect water quality data are time-consuming, labor-intensive, and costly, water resources management has shifted from gathering field measurement data to utilizing remote sensing (RS) data. WDD has been threatened by various driving forces in recent years, such as contamination from different sources, sedimentation, nutrient runoff, salinity intrusion, temperature fluctuations, and microbial contamination. Therefore, this study aimed to retrieve and map WQIs, namely dissolved oxygen (DO) and chlorophyll-a (Chl-a) of the Wadi Dayqah Dam (WDD) reservoir from Sentinel-2 (S2) satellite data using a new procedure of weighted averaging, namely Bayesian Maximum Entropy-based Fusion (BMEF). To do so, the outputs of four Machine Learning (ML) algorithms, namely Multilayer Regression (MLR), Random Forest Regression (RFR), Support Vector Regression (SVRs), and XGBoost, were combined using this approach together, considering uncertainty. Water samples from 254 systematic plots were obtained for temperature (T), electrical conductivity (EC), chlorophyll-a (Chl-a), pH, oxidation–reduction potential (ORP), and dissolved oxygen (DO) in WDD. The findings indicated that, throughout both the training and testing phases, the BMEF model outperformed individual machine learning models. Considering Chl-a, as WQI, and R-squared, as evaluation indices, BMEF outperformed MLR, SVR, RFR, and XGBoost by 6%, 9%, 2%, and 7%, respectively. Furthermore, the results were significantly enhanced when the best combination of various spectral bands was considered to estimate specific WQIs instead of using all S2 bands as input variables of the ML algorithms.

Remediation of Sulfides in Produced Waters of the Oil and Gas Industry Using Hydrogen Peroxide

Produced waters are often treated in open lagoons where hydrogen sulfide (H2S) can off gas, posing a risk to human health and the environment. The aim of this study was to optimize a treatment process using hydrogen peroxide (H2O2) to oxidize H2S while minimizing off gassing. Samples of produced water from West Texas and laboratory-prepared waters utilizing sodium sulfide (Na2S) or biogenic polysulfides were oxidized with H2O2 alone or in combination with copper or iron catalysts, sodium hydroxide (NaOH), or a commercial sulfide oxidizer, HydroPower Green™. Sulfur speciation was measured using Hach test kits for sulfide/sulfate/sulfite and Dräger tubes for headspace H2S. HydroPower Green™ (HPG) helped to reduce H2S in the headspace of water samples; some of this was pH related as NaOH also worked, but not as well as HPG. The dose of peroxide necessary to oxidize sulfides to sulfate is a function of the oxidation-reduction potential (Eh) of the water and total sulfide concentration as well as pH; approximately a 1–4:1 ratio of peroxide to sulfide concentration was needed to oxidize sulfidic waters of pH 7–10 with half-lives under 30 min. Both copper and iron catalysts reduce H2O2 demand and the half-life of H2S. Peracetic acid (PAA) and copper (II) sulfate pentahydrate (CuSO4, 5H2O) were explored as biocides for controlling sulfate-reducing bacteria (SRBs) that produce H2S. An AquaSnap (Hygenia) test kit was employed to monitor relative microbial activity in a wetland porewater containing H2S. Microbial regrowth occurred after a few days using the highest dose of PAA; these results showed that PAA was being used by bacteria as a carbon source even after the initial substantial reduction in the microbial activity. CuSO4, 5H2O at a dose of 1 ppm prevented microbial regrowth. The recommended treatment process from this research is determined by jar testing with H2O2, a base for pH control, a biocide, and possibly a metal catalyst or other co-oxidants in order to achieve oxidation of sulfides without H2S release or the precipitation of metal carbonates or oxides.

Elucidating biogeochemical characterization of nitrogen in the vadose zone integrating geochemistry, microorganism, and numerical simulation

A thorough comprehension of nitrogen biogeochemical processes in the vadose zone is crucial for the effective prevention and remediation of soil-groundwater system contamination. Despite the growing research on this subject, the full scope of nitrogen biogeochemical characterization in different geological environments remains poorly understood. This study addresses this knowledge gap by integrating geochemical, microbiological and numerical simulation approaches to gain a deeper insight into nitrogen biogeochemistry in agriculture. Our findings indicate the biogeochemical behavior of nitrogen in the vadose zone is mediated by microorganisms, driven by hydraulics, influenced by geological conditions and environmental factors. Along the groundwater flow, NH4+-N was found to be heavily accumulated in the topsoil of 0–40 cm, while NO3−-N was transported and driven by hydrodynamics from both vertical and horizontal directions. Microbial diversity, species composition and functional microorganisms were significantly influenced by soil depth, rather than geomorphological types. Oxidation-reduction potential (ORP), total organic carbon (TOC), soil moisture (MOI), bicarbonate (HCO3−), and ferrous (Fe2+) were identified as the principal environmental factors that regulate nitrogen metabolism and the dominant biochemical processes, encompassing nitrogen fixation, nitrification, and denitrification. Driven by hydrodynamics, NH4+-N, NO2−-N and NO3−-N tend to form distinct biochemical reaction zones in the vertical vadose zone. These areas are dynamic and subject to geomorphologies. It should be noted that NO3−-N can migrate towards groundwater from the clayey sand in the Alluvial Plain, which presents a potential risk of groundwater contamination. The fissure structure of loess may serve as the major transport pathway for groundwater nitrogen contamination in the Loess Tableland. This finding highlights the importance of integrating microbiology, geochemistry and hydraulics to elucidate the biogeochemical processes of nitrogen in the vadose zone with a dynamic mindset.

Species pool and soil properties in mangrove habitats influence the species-immigration process of diazotrophic communities across southern China.

Microbial immigration is an ecological process in natural environments; however, the ecological trade-off mechanisms that govern the balance between species extinction and migration are still lacking. In this study, we investigated the mechanisms underlying the migration of diazotrophic communities from soil to leaves across six natural mangrove habitats in southern China. The results showed that the diazotrophic alpha and beta diversity exhibited significant regional and locational variations. The diazotrophic species pool gradually increased from the leaves to nonrhizosphere soil at each site, exhibiting a vertical distribution pattern. Mantel test analyses suggested that climate factors, particularly mean annual temperature, significantly influenced the structure of the diazotrophic community. The diazotrophic community assembly was mainly governed by dispersal limitation in soil and root samples, whereas dispersal limitation and ecological drift were dominant in leaves. Partial least squares path modeling revealed that the species pool and soil properties, particularly the oxidation-reduction potential and pH, were closely linked to the species-immigration ratio of diazotrophic communities. Our study provides novel insights for understanding the ecological trait diversity patterns and spread pathways of functional microbial communities between below- and aboveground habitats in natural ecosystems.IMPORTANCEEnvironmental selection plays key roles in microbial transmission. In this study, we have provided a comprehensive framework to elucidate the driving patterns of the ecological trade-offs in diazotrophic communities across large-scale mangrove habitats. Our research revealed that Bradyrhizobium japonicum, Marinobacterium lutimaris, and Agrobacterium tumefaciens were more abundant in root-associated soil than in leaves by internal and external pathways. The nonrhizospheric and rhizospheric soil samples harbored the most core amplicon sequence variants, indicating that these dominant diazotrophs could adapt to broader ecological niches. Correlation analysis indicated that the diversities of the diazotrophic community were regulated by biotic and abiotic factors. Furthermore, this study found a lower species immigration ratio in the soil than in the leaves. Both species pool and soil properties regulate the species-immigration mechanisms of the diazotrophic community. These results suggest that substantial species immigration is a widespread ecological process, leading to alterations in local community diversity across diverse host environments.

Evaluation of low-cost sensors to integrate in a water quality monitor for real-time measurements.

Low-cost sensors integrated with the Internet of Things can enable real-time environmental monitoring networks and provide valuable water quality information to the public. However, the accuracy and precision of the values measured by the sensors are critical for widespread adoption. In this study, 19 different low-cost sensors, commonly found in the literature, from four different manufacturers are tested for measuring five water quality parameters: pH, dissolved oxygen, oxidation-reduction potential, turbidity, and temperature. The low-cost sensors are evaluated for each parameter by calculating the error and precision compared to a typical multiparameter probe assumed as a reference. The comparison was performed in a controlled environment with simultaneous measurements of real water samples. The relative error ranged from 0.33 to 33.77%, and most of them were 5%. The pH and temperature were the ones with the most accurate results. In conclusion, low-cost sensors are a complementary alternative to quickly detect changes in water quality parameters. Further studies are necessary to establish a guideline for the operation and maintenance of low-cost sensors.

Vertical Distribution Characteristics and Driving Factors of Bacterioplankton and Nitrogen Phosphorus Cycle Genes in Danjiangkou Reservoir

Danjiangkou Reservoir is a critical water source for the South-to-North Water Diversion Project, which harbors a diverse bacterioplankton community with varying depths, and the understanding of its nitrogen and phosphorus cycle and associated driving factors remains limited. In this study, we selected five ecological sites within Danjiangkou Reservoir and conducted metagenomics analysis to investigate the vertical distribution of bacterioplankton communities in the surface, middle, and bottom layers. Furthermore, we analyzed and predicted the function of nitrogen and phosphorus cycles, along with their driving factors. Our findings revealed the dominance of Proteobacteria, Actinobacteria, and Planctomycetes in the Danjiangkou Reservoir. Significant differences were observed in the structure of bacterioplankton communities across different depths, with temperature （T）, oxidation-reduction potential （ORP）, dissolved oxygen （DO）, and Chla identified as primary factors influencing the bacterioplankton composition. Analysis of nitrogen cycle functional genes identified 39 genes, including gltB, glnA, gltD, gdhA, NRT, etc., which were involved in seven main pathways, encompassing nitrogen fixation, nitrification, denitrification, and dissimilatory nitrate reduction. Phosphorus cycle function gene analysis identified 54 genes, including pstS, ppx-gppA, glpQ, ppk1, etc., primarily participating in six main pathways, including organic P mineralization, inorganic P solubilization, and regulatory. Cluster analysis indicated that different depths were significant factors influencing the composition and abundance of nitrogen and phosphorus cycle functional genes. The composition and abundance of nitrogen and phosphorus cycle functional genes in the surface and bottom layers differed and were generally higher than those in the middle layer. Deinococcus, Hydrogenophaga, Limnohabitans, Clavibacter, and others were identified as key species involved in the nitrogen and phosphorus cycle. Additionally, we found significant correlations between nitrogen and phosphorus cycle functional genes and environmental factors such as DO, pH, T, total dissolved solids （TDS）, electrical conductivity （EC）, and Chla. Furthermore, the content of these environmental factors exhibited depth-related changes in the Danjiangkou Reservoir, resulting in a distinct vertical distribution pattern of bacterioplankton nitrogen and phosphorus cycle functional genes. Overall, this study sheds light on the composition, function, and influencing factors of bacterioplankton communities across different layers of Danjiangkou Reservoir, offering valuable insights for the ecological function and diversity protection of bacterioplankton in this crucial reservoir ecosystem.

P-016 Prevalence of high oxidative stress and poor sperm DNA fragmentation levels in different groups of patients

Abstract Study question What is the prevalence of patients with high oxidation-reduction potential (ORP) and high sperm DNA fragmentation (SDF) in different patient groups with and without varicocele? Summary answer A large percentage of normozoospermic patients and patients who are normally considered of manageable in assisted reproduction show high SDF and/or high ORP. What is known already Standard semen analysis, even according to WHO criteria, is very limited in predicting male fertility potential. Oxidative stress is widely recognized as a major contributor to male infertility. Therefore, sperm DNA fragmentation (SDF) is increasingly recommended as additional test in diagnostics. High levels of oxidative stress and SDF have also been reported in patients with varicocele. Yet, SDF and oxidative stress tests are not routinely tested in ART laboratories. Apart from the cost and/or complexity of these tests, a reason for the lack of usage is the lack of knowledge of the prevalence. Study design, size, duration This is a retrospective analysis of data obtained from 2,946 patients attending the Department of Urology, Hamad Medical Corporation, Doha, Qatar, for fertility diagnosis from January to December 2018. For this analysis only patients (n = 773) who had a full data set for sperm DNA fragmentation (SDF) and seminal oxidative stress as measured by means of the oxidation-reduction potential (ORP) were included. Participants/materials, setting, methods Apart from SDF and ORP, standard semen parameters (ejaculate volume, sperm concentration, total and progressive motility, and normal sperm morphology), and the presence of varicocele were determined. Semen parameters were determined according to WHO 2010 criteria. SDF was tested using the Halosperm G2 test (Halotech DNA SL, Madrid, Spain), while ORP was determined using the MiOXSYS® (Aytu BioScience, Englewood, CO). Patients were categorized as normo-, oligo-, astheno-, and teratozoospermic. Main results and the role of chance The mean sperm concentration of the patients was 33.5 × 106 sperm/mL with a mean total motility of 50.3%. The overall percentage of patients with high (&amp;gt;20% SDF) SDF was 57.4% and those with high (≥1.34 mV/106 sperm/mL) ORP 63.4%. Varicocele was diagnosed in 14.0% of the patients. In normozoospermic patients, 26.8% had high SDF, whereas in the non-normozoospermic group this was 59.8% (P = 0.0108). In non-oligozoospermic (53.7%), non-asthenozoospermic (34.7%) and non-teratozoospermic (43.4%) groups, SDF was significantly higher. High ORP values were recorded in 35.7% of normozoospermic, 53.4% non-oligozoospermic, 47.2% of non-asthenozoospermic, and 49.7% of teratozoospermic patients. The difference between the prevalence of high ORP in the normozoospermic (35.7%) and the non-normozoospermic group is significant (P = 0.0063). When both tests (high SDF or high ORP) were considered, 50.0% of normozoospermic, 76.9% of non-oligozoospermic, 59.7% of non-asthenozoospermic, and 71.2% of non-teratozoospermic patients showed seminal pathology. High SDF was detected in 59.3% of varicocele patients, while 50.0% of varicocele patients had high ORP values. In patients without varicocele, 57.1%, 65.6%, and 82.7% had high SDF, high ORP, and high SDF or high ORP, respectively. These percentages were significantly (P &amp;lt; 0.0003) higher than for the corresponding normal groups. Limitations, reasons for caution Although the overall sample size of 773 is reasonably high, after sub-grouping the sample size is much smaller. Since this study only analyzed the SDF and ORP in patients attending and andrological outpatient clinic, the results could be different if patients in IVF and/or ICSI treatment cycles were analyzed. Wider implications of the findings This study highlights that complementation of semen analysis with SDF and oxidative stress testing will identify a large percentage of patients who would benefit from andrological treatment before assisted reproductive techniques (ART). This approach would result in better chances of these patients for successful ART. Trial registration number not applicable

Exploration of plasma‐activated water (PAW) as a cleaning‐in‐place (CIP) solution for fouling removal and microbial reduction

AbstractThe rapid fouling and bacterial contamination of equipment, heat exchangers, and pipelines are major concerns in food manufacturing plants. The process of cleaning‐in‐place (CIP) in the food manufacturing industry involves hazardous chemicals such as sulfuric acid, chlorine, sodium hydroxide, and potassium hydroxide. This study aims to investigate the cleaning efficiency of a novel environment‐friendly solution, plasma‐activated water (PAW), for removing dairy and plant‐based fouling and for biofilm reduction. PAW was produced by exposing water to plasma, which is a partially ionized gas generated by applying electricity to air. PAW prepared in this study had a pH, electrical conductivity (EC), and oxidation–reduction potential (ORP) of 2.5 ± 0.1, 1170. 1 ± 202.2 μS/cm, and 589.0 ± 2.4 mV, respectively. Holding PAW at different temperatures (20–75°C) did not change pH, ORP, and EC significantly, while nitrite and nitrate concentrations in PAW did not show a consistent trend with temperature. The treatment time and temperature of PAW were optimized for cleaning fouled coupons (stainless‐steel type 304 and 316) using model fouling fluids (MFF) with dairy (whey) and plant‐based (oat) proteins using full‐factorial design. The optimized PAW combinations (15 min/75°C and 5 min/75°C) were found to be as effective for fouling removal as compared to CIP controls (conventional caustic and acid solutions). Optimized PAW also showed significant biofilm reduction of Listeria innocua on stainless‐steel coupons with/without fouling, with at least 4.4 log and 4.0 log reductions in L. innocua biofilms when attached to MFF‐whey and MFF‐oat, respectively.Practical applicationsPlasma‐activated water (PAW) can inactivate a wide spectrum of microorganisms on various food and food contact surfaces. We propose the use of environment‐friendly plasma‐activated water (PAW), which can be prepared on‐site and on‐demand for cleaning‐in‐place (CIP) operations in the food industry. The results of this study suggest the potential of PAW as a promising CIP alternative for cleaning and sanitizing surfaces soiled by fouling deposits in dairy and plant‐based industries.

Regeneration of ozone decomposition catalysts by elimination of O22- from oxygen vacancies

The deactivation of ozone decomposition catalysts is a big drawback for its industrial application, and the existing gas phase regeneration methods are not universally applicable while the operability conditions are harsh. Thus, there is a pressing need to develop a mild and universal regeneration approach. Based on the fact that the deactivation of ozone decomposition catalysts is mainly due to the accumulation of O22- in the surface oxygen vacancies, increasing the catalyst metal valence state. Herein, we propose a liquid phase method by elimination of O22- from oxygen vacancies for regenerating inactivated ozone decomposition catalysts. This method worked well for regenerating ozone decomposition catalysts by using the reducing solution with oxidation reduction potential (ORP) less than −163 mV. Experimental results indicate that even after ten cycles of deactivation and regeneration, surficial oxygen vacancies and metal valence states of the ozone decomposition catalyst e.g. MnFe0.25Ox can be well restored and the ozone conversion rate decreased by less than 5 %.

Low-dose natural clay Kaolin promotes the growth of submerged macrophytes and alters the rhizosphere microorganism community: Implications for lake restoration

Sediment properties have a crucial effect on the growth and recovery of aquatic plants in lakes. Addition of various chemical substances has been proposed to reinforce the recovery of plants after a nutrient loading reduction. However, the effects of such sediment amendments on plant growth, especially those from rhizosphere microorganisms, is limited. We added Kaolin clay to sediments in different concentrations to explore its impact on the growth of Vallisneria natans and Ottelia acuminate and the concurrent shift in rhizosphere microorganisms using high-throughput sequencing technology. We found that the addition of low doses (10 % and 20 % in mass ratio) of Kaolin significantly modified sediment conditions (oxidation reduction potential and pH), with implications also for the composition, diversity, and stability of rhizosphere microorganisms. LEfSe analysis revealed that low-dose addition of Kaolin increased the abundances of functional microbial groups that benefit plant nutrient absorption and enhance plant stress resistance, such as Spirillaceae, Rhodocyclaceae, and Burkholderiales. Moreover, low doses of Kaolin significantly promoted the photosynthesis and nutrient absorption of submerged macrophytes, thereby facilitating plant growth. A structural equation model (SEM) indicated that the direct impact of Kaolin on the growth of submerged plants was relatively minor, while the indirect effect through modulation of rhizosphere microorganisms was important. Our study suggests that low doses of Kaolin may be used to promote the growth of submerged macrophytes when lakes with a high organic content in the sediment are recovering after nutrient loading reduction.

Biogeochemical changes during supercritical CO2–H2O-coal-microorganism interaction

A 100-day scCO2-H2O-coal-microorganism interaction experiment was conducted in this study to explore the biogeochemical changes during the supercritical CO2 (scCO2) storage in deep water-bearing coal seams. Compared to a control experiment without microorganisms, the presence of microorganisms resulted in a slightly increase in pH but a marked reduction in oxidation-reduction potential (ORP). An increase in Fe2+ ions and decrease in SO42− ions in the experimental group were found to be closely related to microbial mediation, potentially leading to an increase in secondary pyrite. Networked biofilms and N-acetyl-L-leucine as a leucine derivative were only appeared in the experimental group, indicating microbial growth and metabolism. Microbial activities increased the dissolved organic carbon (DOC), accelerated the accumulation of aromatic organic compounds, and diminished macromolecular organic compounds. After scCO2 injection, microbial number and diversity exhibited a sharp decline and gradual recovery. The dominant Clostridium sensu stricto 13 (>50%), Desulfohalotomaculum (>20%) and norank Desulfallas-Sporotomaculum (>9%) may play important roles in the biogeochemical processes of Fe and S through cooperative relationships. Microbial communities resisted scCO2-H2O stress through diversified defense strategies such as spore formation, enhanced leucine metabolism level, and extracellular polymeric substances (EPS) secretion. The recovery of the number and activity of methanogens indicated potential for the biomethanation of sequestered CO2.

Nano zero valent iron stimulated acetaldehyde oxidation, electron transfer, and RBO pathway for enhanced medium-chain carboxylic acids production

Nano zero-valent iron (NZVI) has been shown to effectively enhance the chain elongation (CE) process, addressing the issue of limited yield of medium-chain carboxylic acids (MCCA) from organic wastewater. However, the specific impact of NZVI on the metabolism of CE bacteria (CEB) is not well understood. In this study, it was aimed to investigate the mechanism by which an optimal concentration of NZVI influences CE metabolism, particularly in relation to ethanol oxidation, electron transfer, and MCCA synthesis. This was achieved through single-factor influence experiments and metagenomic analysis. The results showed that the addition of 1 g/gVSS NZVI achieved the highest MCCA yield (n-caproic acid + n-octanoic acid) at 2.02 g COD/L, which was 4.9 times higher than the control. This improvement in MCCA production induced by NZVI was attributed to several factors. Firstly, NZVI facilitated the oxidation of acetaldehyde, leading to its reduced accumulation in the system (from 18.4 % to 5.8 %), due to the optimized chemical environment created by NZVI corrosion, including near-neutral pH and a more reductive oxidation–reduction potential (ORP). Additionally, the inherent conductivity property of NZVI and the additional Fe ions released during corrosion improved the electron transfer efficiency between CEB. Lastly, both the composition of microbial communities and the abundance of unique enzyme genes confirmed the selective stimulation of NZVI on the reverse β-oxidation (RBO) pathway. These findings provide valuable insights into the role of NZVI in CEB metabolism and its potential application for enhancing MCCA production in CE bioreactors.

Tomato yield and soil chemical properties influenced by low–molecular–weight organic acids in calcareous soil

&lt;p&gt;Calcareous soils have restrictive characteristics that limit and pose a challenge for crop production; in this environment, plants can exude low-molecular-weight organic acids (LMWOAs). This study aimed to verify the influence of exogenously applied LMWOAs in calcareous soils on tomato yield and the chemical characteristics of soil and leachate. &lt;em&gt;Solanum lycopersicum&lt;/em&gt; L. seedlings were grown in pots containing calcareous soil in a greenhouse, fertilized by drip irrigation with Steiner nutrient solution in which the treatments 0.1 mM citric acid (CA), 0.1 mM oxalic acid (OA), 0.01 mM salicylic acid (SA) and a control without LMWOAs (T0) were prepared, applied during the whole growth cycle. The experiment was repeated four times, with twenty replicates per treatment, under a completely randomized design. The yield per plant was quantified, while pH and microbial respiration (RMS) were measured in the soil. The pH, electrical conductivity (EC), oxidation-reduction potential (ORP), carbonate (CO&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;2–&lt;/sup&gt;), and bicarbonate (HCO&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;–&lt;/sup&gt;) contents were quantified in the leachates. SA application reduced the soil pH (8.75). SA and CA improved the fruit yield per plant by 11% and 33%, respectively (p &amp;lt; 0.05). CA induced a 1.7% reduction in leachate pH (p &amp;lt; 0.05) and a 15.9% increase in HCO&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;–&lt;/sup&gt; content (p &amp;lt; 0.05). SA decreased EC and CO&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;2–&lt;/sup&gt; concentrations by 8.9 and 23.1% (p &amp;lt; 0.05), but increased HCO&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;–&lt;/sup&gt; content by 23.1 % (p &amp;lt; 0.05). The use of LMWOAs as a strategy in the management of calcareous soils can promote favorable conditions for tomato yield per plant.&lt;/p&gt;

Evaluating Natural Source Zone Depletion and Enhanced Source Zone Depletion in laboratory columns via soil redox continuous sensing and microbiome characterization

To optimally employ Natural Source Zone Depletion (NSZD) and Enhanced Source Zone Depletion (ESZD) at sites impacted by light non-aqueous phase liquids (LNAPL), monitoring strategies are required. Emerging use of subsurface oxidation-reduction potential (ORP) sensors shows promise for tracking redox evolution, which reflects ongoing biogeochemical processes. However, further understanding of how soil redox dynamics relate to subsurface microbial activity and LNAPL degradation pathways is needed. In this work, soil ORP sensors and DNA and RNA sequencing-based microbiome analysis were combined to elucidate NSZD and ESZD (biostimulation via periodic sulfate addition and biosparging) processes in columns containing LNAPL-impacted soils from a former petroleum refinery. Results show expected relationships between continuous soil redox and active microbial communities. Continuous data revealed spatial and temporal detail that informed interpretation of the hydrocarbon biodegradation data. Redox increases were transient for sulfate addition, and sequencing revealed how hydrocarbon concentration and composition impacted microbiome structure and naphthalene degradation. Periodic biosparging did not result in fully aerobic conditions suggesting observed biodegradation improvements could be explained by alternative anaerobic metabolisms (e.g., iron reduction due to air oxidizing reduced iron). Collectively, data suggest combining continuous redox sensing with microbiome analysis provides insights beyond those possible with either monitoring tool alone.