Oxidation-reduction Potential Research Articles

Regulation of nitrite-dependent anaerobic methane oxidation bacteria by available phosphorus and microbial communities in lake sediments of cold and arid regions

As global anthropogenic nitrogen inputs continue to rise, nitrite-dependent anaerobic methane oxidation (N-DAMO) plays an increasingly significant role in CH4 consumption in lake sediments. However, there is a dearth of knowledge regarding the effects of anthropogenic activities on N-DAMO bacteria in lakes in the cold and arid regions. Sediment samples were collected from five sampling areas in Lake Ulansuhai at varying depth ranges (0–20, 20–40, and 40–60 cm). The ecological characterization and niche differentiation of N-DAMO bacteria were investigated using bioinformatics and molecular biology techniques. Quantitative PCR confirmed the presence of N-DAMO bacteria in Lake Ulansuhai sediments, with 16S rRNA gene abundances ranging from 1.72 × 104 to 5.75 × 105 copies·g−1 dry sediment. The highest abundance was observed at the farmland drainage outlet with high available phosphorus (AP). Anthropogenic disturbances led to a significant increase in the abundance of N-DAMO bacteria, though their diversity remained unaffected. The heterogeneous community of N-DAMO bacteria was affected by interactions among various environmental characteristics, with AP and oxidation-reduction potential identified as the key drivers in this study. The Mantel test indicated that the N-DAMO bacterial abundance was more readily influenced by the presence of the denitrification genes (nirS and nirK). Network analysis revealed that the community structure of N-DAMO bacteria generated numerous links (especially positive links) with microbial taxa involved in carbon and nitrogen cycles, such as methanogens and nitrifying bacteria. In summary, N-DAMO bacteria exhibited sensitivity to both environmental and microbial factors under various human disturbances. This study provides valuable insights into the distribution patterns of N-DAMO bacteria and their roles in nitrogen and carbon cycling within lake ecosystems.

Effects of biochar immobilization of Serratia sp. F4 OR414381 on bioremediation of petroleum contamination and bacterial community composition in loess soil

Petroleum hydrocarbons pose a significant threat to human health and the environment. Biochar has increasingly been utilized for soil remediation. This study investigated the potential of biochar immobilization using Serratia sp. F4 OR414381 for the remediation of petroleum-contaminated soil through a pot experiment conducted over 90 days. The treatments in this study, denoted as IMs (maize straw biochar-immobilized Serratia sp. F4), degraded 82.5% of the total petroleum hydrocarbons (TPH), 59.23% of the aromatic, and 90.1% of the saturated hydrocarbon fractions in the loess soils. During remediation, the soil pH values decreased from 8.76 to 7.33, and the oxidation-reduction potential (ORP) increased from 156 to 229 mV. The treatment-maintained soil nutrients of the IMs were 138.94 mg/kg of NO3- -N and 92.47 mg/kg of available phosphorus (AP), as well as 11.29% of moisture content. The activities of soil dehydrogenase (SDHA) and catalase (CAT) respectively increased by 14% and 15 times compared to the CK treatment. Three key petroleum hydrocarbon degradation genes, including CYP450, AJ025, and xylX were upregulated following IMs treatment. Microbial community analysis revealed that a substantial microbial population of 1.01E+ 09 cells/g soil and oil-degrading bacteria such as Salinimicrobium, Saccharibacteria_genera_incertae_sedis, and Brevundimonas were the dominant genera in IMs treatment. This suggests that the biochar immobilized on Serratia sp. F4 OR414381 improves soil physicochemical properties and enhances interactions among microbial populations, presenting a promising and environmentally friendly approach for the stable and efficient remediation of petroleum-contaminated loess soil.

Evaluation of water ecological health of Yanhe River based on benthic fauna integrity index.

Yanhe River Basin is located in the hilly gully area of the Loess Plateau with serious soil erosion. Strong human activities in the middle and lower reaches lead to fragile ecological environment. Soil erosion status varies among different geomorphic units within the watershed (loess liang hilly and gully region, loess mao hilly and gully region, and broken platform region). In this study, we surveyed the benthic community from the Yanhe River Basin in April (spring) and October (autumn) of 2021. To evaluate the water ecological health status of the watershed and investigate the effects of different geomorphic units on the benthic integrity of the benthos, we constructed the benthic-index of biotical integrity (B-IBI) based on the biological data. We identified a total of 113 species of 73 genera in 4 phyla of benthic fauna, with aquatic insects as the dominant taxa in both seasons. Through screening 26 candidate indicators, we found that the spring B-IBI consisted of three indicators: relative abundance of individuals of dominant taxonomic units, family biotic index (FBI), and relative abundance of predator individuals, and that autumn B-IBI was composed of the number of taxonomic units of Ephemeroptera, FBI value, and the relative abundance of predator individuals. Results of the B-IBI evaluation showed that 83.3% of the sampling sites in the upper mainstem and tributaries were at a healthy condition, while only 28.6% sampling sites in the middle and lower mainstem and tributaries were at a healthy condition. In addition, the health status of the watershed was better in spring than in autumn. The Kruskal-Wallis nonparametric tests showed that benthic density, species number, and B-IBI percentile scores in the fragmented loess area were significantly higher in spring than in autumn, and significantly lower in autumn than in the loess liang hilly and gully region and loess mao hilly and gully region, being mainly caused by the increasing erosion due to the concentrated rainfall in wet season. Results of the redundancy analysis showed that key environmental factors affecting benthic community structure in spring were boulder substrate, chlorophyll-a, oxidation reduction potential, turbidity, conductivity, and dissolved oxygen, and were nitrate-nitrogen, oxidation reduction potential, and pH in autumn.

Interaction of cemented paste backfill (CPB) and circumneutral mine water during column experiments

Cemented paste backfill (CPB) is used as a support and filler material in underground mines. In underground conditions, before mine closure and flooding, surface and groundwaters with variable quality are in contact with CPB material, which may result in the leaching of harmful substances from the CPB. In this study, we used actual mine water from a gold mine to flush CPB in a laboratory test to simulate underground conditions and the environmental influence of CPB on groundwaters more realistically than before.Different CPB materials were treated with mine water in columns for nine months. The columns were drained and filled with new mine water batches four times during the experiment to simulate intermittent flushing underground. The dissolved elemental content, major cations, pH and oxidation-reduction potential (ORP) of the waters were measured, and the chemical results were analysed by performing geochemical modelling with the widely used geochemical code PHREEQC. X-ray tomography was also used to examine the internal structure of the CPB specimens.The results demonstrated that calcium and sulphate present in CPB parent materials leached into the mine water, which might cause a deterioration of CPB. In contrast, the concentrations of dissolved As, Sb and Ni decreased in the mine water when it was in contact with CPB materials. However, arsenic started to be re-released from the materials at the end of the nine-month experimental period. The geochemical modelling suggests that the removal of metals/metalloids from the mine water was driven by the surface complexation reactions on originally present and/or freshly precipitated metal (hydr)oxide minerals. A longer and modified testing period is needed to thoroughly examine the conditions under which these adsorbed elements start to release over time.

The influence of pH on the efficacy of oxidation-reduction potential (ORP) to predict chlorine disinfection of surrogate bacteria, Escherichia coli O157:H7 and Listeria monocytogenes in oxidant demand free conditions and fresh produce wash water

Oxidation-reduction potential (ORP) is commonly used as a rapid measurement of the antimicrobial potential of free chlorine during industrial fresh produce washing. The current study tested the hypothesis that ORP can act as a “single variable” measurement of bacterial (vegetative and endospores) inactivation effectiveness with free chlorine irrespective of the water pH value. This situation has on occasion been assumed but never confirmed nor disproven. Chlorine-dosed pH 6.5 and 8.5 phosphate buffer solutions were inoculated with Escherichia coli (E. coli), Listeria innocua (L. innocua), or Bacillus subtilis (B. subtilis) endospores. ORP, free chlorine (FC), and log reduction were monitored after 5 s (for E. coli and L. innocua) and up to 30 min (for B. subtilis spores) of disinfection. Logistic and exponential models were developed to describe how bacteria reduction varied as a function of ORP at different pH levels. Validation tests were performed in phosphate buffered pH 6.5 and 8.5 cabbage wash water periodically dosed with FC, cabbage extract and a cocktail of Escherichia coli O157:H7 (E. coli O157:H7) and Listeria monocytogenes (L. monocytogenes). The built logistic and exponential models confirmed that at equal ORP values, the inactivation of the surrogate strains was not consistent across pH 6.5 and pH 8.5, with higher reductions at higher pH. This is the opposite of the well-known free chlorine-controlled bacterial inactivation, where the antibacterial effect is higher at lower pH. The validation test results indicated that in the cabbage wash water, the relationship between disinfection efficiency and ORP was consistent with the oxidant demand free systems. The study suggests that ORP cannot serve as a reliable single variable measurement to predict bacterial disinfection in buffered systems. When using ORP to monitor and control the antibacterial effectiveness of the chlorinated wash water, it is crucial to take into account (and control) the pH.

Synergistic Effect of Plasma-Activated Water with Micro/Nanobubbles, Ultraviolet Photolysis, and Ultrasonication on Enhanced Escherichia coli Inactivation in Chicken Meat

The use of integrated plasma-activated water (PAW) with micro/nanobubbles (MNBs), ultraviolet (UV) photolysis, and ultrasonication (US) for the synergistic efficiency of Escherichia coli inactivation in chicken meat was investigated. A 2k factorial design was employed to optimize the combined treatment parameters for pathogen disinfection in Design of Experiments (DOE) techniques. Its effectiveness was evaluated based on electrical conductivity (EC), oxidation–reduction potential (ORP), hydrogen peroxide (H2O2) concentration, and E. coli inactivation. The most significant impact on E. coli reduction was observed for MNBs, UV treatment time, and their interaction (MNBs and UV). Optimal E. coli inactivation (6 log10 CFU/mL reduction) was achieved by combining PAW with MNB and UV for 10 and 20 min, respectively. Integrating PAW with appropriate supplementary technologies enhanced E. coli inactivation by 97% compared to PAW alone. This novel approach provides a promising alternative for pathogen control in chicken meat, potentially improving food safety and shelf life in the poultry industry.

Processes and mechanisms in remediation of aqueous chromium contamination by sulfidated nano-scale zerovalent iron (S-nZVI): Experimental and computational investigations

Sulfidated nano-scale zerovalent iron (S-nZVI) has emerged as an advanced functional nanomaterial for efficiently remediating Cr(VI) contamination in aqueous environments. However, there is an insufficient understanding of its coherent process, removal pathway, and hydrochemical reactive mechanisms, presenting potential challenges for its future environmental applications. To address this gap, this study successfully synthesized S-nZVI through a chemical precipitation method and effectively applied it for the removal of Cr(VI). Additional characterization revealed that the removal of Cr(VI) followed a sequence of rapid chemisorption and intraparticle diffusion processes, concomitant with an increase in pH and a decrease in oxidation-reduction potential. The remediation mechanism encompassed a synergistic reduction of Cr(VI) to Cr(III) and simultaneous immobilization via Cr2FeO4 coprecipitation. The highest Cr(VI) removal capacity of 75 mg/g was attained during dynamic removal experiments in the sand column packed with S-nZVI. Further computational analysis, employing density functional theory calculations based on the experimental data, revealed the involvement of multiple molecular orbitals of Cr(VI) in the removal process. It also elucidated a step-by-step reduction pathway for Cr(VI) characterized by decreasing free energy. These findings provide evidence-based insights into Cr(VI) remediation using S-nZVI and can serve as valuable technical support for future environmental management of heavy metals.

Degradation of dissolved sulfide in water using multi-hole dielectric barrier discharge

Biogas obtained from livestock manure is used as fuel for solid oxide fuel cells. Although H2S is a typical biogas, it is a fatal disadvantage for fuel-cell power generation and, thus, must be removed. In this study, we proposed an effective method for sulfide removal from water using a multi-hole dielectric barrier discharge (DBD) system. In this system, active species, such as ozone, ultraviolet rays, hydroxyl radicals, and hydrogen peroxide, were simultaneously generated. Under optimal conditions, dissolved sulfide (initial concentration: 120 mg/L) was completely degraded within 10 min in air plasma and 6 min in oxygen plasma. Changes in the physical properties of the sulfide-treated water were confirmed by measuring the pH, oxidation-reduction potential, and dissolved oxygen. Results of the by-product analysis showed that sulfide was converted into sulfate by reacting with a large amount of ozone, and the active species were emitted from the multi-hole DBD system. In summary, multi-hole DBD technology has demonstrated merit as a water-contaminant purification technology and for the removal of dissolved sulfide.

Recovery of uranium from phosphate ore of Iran mine: Part II- solvent extraction of uranium from wet-process phosphoric acid

The current study in laboratory scale was aimed at developing an optimal two-stage extraction process for production of yellow cake from the phosphoric acid solution that was extracted from the Sheikh Habil phosphate rocks in central Iran. To attain an optimized extraction process, different mixtures of D2EHPA + TOPO + TBP were examined. A total extraction cycle including extraction, stripping and yellow cake precipitation was run to realistically evaluate the performances of the selected mixtures-conditions. As for optimization of the operational conditions, we exploited central composite design (CCD) method, that is a branch of the surface response methodology (RSM), and analyzed the results with standard statistical methods. The O/A (organic to aqueous ratio) = 2, 11 min extraction time, 5 wt% TOPO concentration, 10–15 wt% TBP concentration, 20 wt% D2EHPA concentration, 800 mv oxidation-reduction potential, and 25 °C temperature were obtained as optimum extraction parameters. The O/A = 15, 11 min stripping time, 50 wt% phosphoric acid concentration, 250 mv oxidation-reduction potential, and 40 °C temperature were obtained as optimum stripping parameters. Finally on the last uranium extraction from the H3PO4 strippant on the optimum conditions, the concentration of uranium was more than 4500 ppm with extraction efficiency near to 90 %. Scrubbing of organic phase was done by 2 wt% of sulfuric acid solution at 40 °C and precipitation of ammonium uranyl carbonate (AUC, (NH4)4UO2(CO3)3) was done with 2 M ammonium carbonate solution at an O/A ratio of 1/2 with efficiency more than 95 % in the uranium precipitation process.

THE COMPARISON OF OXIDATION EFFICIENCY OF REACTIVE OXYGEN SPECIES (ROS): PILOT SCALE OF MICROBUBBLE TECHNOLOGIES WITH OXYGEN CONCENTRATION

The objective of this study is to assess and compare the effectiveness of an oxidizing agent. Within the field of advanced oxidation processes (AOPs), ozone, a highly reactive gas, generates reactive oxygen species (ROS) as byproducts through chemical reactions. The study employed a dielectric barrier discharge (DBD) plasma generator to produce ozone gas. This study was carried out under different gas source conditions, including both air and oxygen. Additionally, the ROS produced as byproducts from the interaction between ozone gas and water were measured using oxidation-reduction potential (ORP) values. The ORP values exhibit strong foundational attributes for both ozone dissolution and ROS oxidation efficiency. To extend the interaction duration between ozone gas and water, a stone diffuser was utilized to introduce ozone gas into the water. This mechanism resulted in the creation of ozone microbubbles through a process known as cavitation. The results illustrate a positive relationship between the flow rate and ozone yield. This trend reached its highpoint with the highest observed ozone concentrations approximately 14.11 mg/L for oxygen and 4.55 mg/L for air both achieved at a flow rate of 11 L/min. Furthermore, the highest ozone concentrations were recorded at 15.17 mg/L for oxygen and 12.59 mg/L for air after a 10 min discharge period. Interestingly, ozone generated from oxygen feed gas exhibited a higher concentration yield than that from air feed gas. Moreover, the ORP value displayed a continuous increase with longer treatment times, eventually stabilizing at around the 15 min. This pattern corresponded to the water reaching its highest the ORP values approximately 821 mV for oxygen and 569 mV for air. In summary, this study emphasizes the potential benefits of utilizing ozone as an effective oxidant in both gaseous (ozone gas) and liquid (ROS) phases. It especially emphasizes the essential role played by the generation of ozone and ROS from an oxygen-fed gas source. Moreover, it highlights the significance of maintaining an optimal flow rate of 11 L/min and a discharge duration of 10 min for achieving the highest ozone concentration. Similarly, a treatment time of 15 min for the liquid phase is recommended to maximize ORP values. Both of these values indicate the highest potential advantages for producing an effective oxidant.

Treatment of polluted river water using potential bioflocculant produced by Klebsiella pneumonia UKD24.

Chemically enhanced primary treatment (CEPT) is a rapid wastewater treatment process involving treating wastewater with two chemical-aided processes, coagulation, and flocculation. In the present study, a natural extracellular polymeric substance flocculant (EPSBF) produced by Klebsiella pneumonia UKD24, a bacterium isolated from the sewage treatment plant, and a synthetic polyacrylamide anionic polymer flocculant (PAM) were evaluated to treat polluted river water. The synthetic PAM showed immediate turbidity reduction after agitation, while the EPSBF expressed a rapid decrease in optical density. After 20 min of the settling period, the EPSBF showed reduced rates of turbidity, optical density, and chemical oxygen demand at 74.14 ± 5.2%, 89.37 ± 0.76%, and 87.21 ± 0.73%, respectively, while PAM showed 67.08 ± 4%, 85.68 ± 2%, and 86.57 ± 2%, respectively. EPSBF treatment significantly improved the water quality parameters in terms of total dissolved solids, total suspended solids, conductivity, and oxidation-reduction potential than PAM treatment. However, the EPSBF has shown a more water-holding capacity and relatively weak flock formation, producing more sludge volume than PAM. Furthermore, though the sludge produced by the EPSBF treatment had a higher moisture content, it showed shorter capillary suction time (CST). In contrast, sludge formed in PAM treatment had lower moisture content, but it exhibited prolonged CST value indicating that PAM treatment sludge showed slow dewaterability.

Spatial distribution characteristics and degradation mechanism of microorganisms in n-hexadecane contaminated vadose zone

The damage caused by petroleum hydrocarbon pollution to soil and groundwater environment is becoming increasingly significant. The vadose zone is the only way for petroleum hydrocarbon pollutants to leak from surface into groundwater. The spatial distribution characteristics of indigenous microorganisms in vadose zone, considering presence of capillary zones, have rarely been reported. To explore the spatial distribution characteristics of indigenous microorganisms in vadose zone contaminated by petroleum hydrocarbons, a one-dimensional column migration experiment was conducted using n-hexadecane as characteristic pollutant. Soil samples were collected periodically from different heights during experiment. Corresponding environmental factors were monitored online. The microbial community structure and spatial distribution characteristics of the cumulative relative abundance were systematically analyzed using 16S rRNA sequencing. In addition, the microbial degradation mechanism of n-hexadecane was analyzed using metabolomics. The results showed that presence of capillary zone had a strong retarding effect on n-hexadecane infiltration. Leaked pollutants were mainly concentrated in areas with strong capillary action. Infiltration and displacement of NAPL-phase pollutants were major driving force for change in moisture content (θ) and electric conductivity (EC) in vadose zone. The degradation by microorganisms results in a downward trend in potential of hydrogen (pH) and oxidation-reduction potential (ORP). Five petroleum hydrocarbon-degrading bacterial phyla and 11 degradable straight-chain alkane bacterial genera were detected. Microbial degradation was strong in the area near edge of capillary zone and locations of pollutant accumulation. Mainly Sphingomonas and Nocardioides bacteria were involved in microbial degradation of n-hexadecane. Single-end oxidation involved microbial degradation of n-hexadecane (C16H34). The oxygen consumed, hexadecanoic acid (C16H32O2) produced during this process, and release of hydrogen ions (H+) were the driving factors for reduction of ORP and pH. The vadose zone in this study considered presence of capillary zone, which was more in line with actual contaminated site conditions compared with previous studies. This study systematically elucidated vertical distribution characteristics of petroleum hydrocarbon pollutants and spatiotemporal variation characteristics of indigenous microorganisms in vadose zone considered presence of capillary zone. In addition, the n-hexadecane degradation mechanism was elucidated using metabolomics. This study provides theoretical support for development of natural attenuation remediation measures for petroleum-hydrocarbon-contaminated soil and groundwater.

Insights into processes and consequent metal(loid) behavior in dredged estuarine sediments upon electrokinetic treatment

The use and reuse of natural and waste materials after treatment has become increasingly crucial as a means of achieving sustainable and environmentally-friendly solutions, and is part of a broader trend towards embracing circular economy principles. This study aims to understand the behavior of different elements (metal(loid)s and non-metals) and minerals during and after electrokinetic remediation (EKR) and to develop an effective approach to monitor its progress and overcome unwanted occurrences. In this regard, estuarine sediments, collected from Tancarville (Seine River estuary, France), were electrokinetically treated using a 64 L laboratory reactor; treatment was done 8 h per day for 21 days. The physico-chemical properties (pH, electric conductivity, and oxido-reduction potential) and current were monitored during treatment. The spatial evolution of the physico-chemical, physical (grain size distribution), mineral (mainly carbonates), organic, and elemental (As, Ca, Cl, Mg, Na, Pb, Sr, Zn, and Zr) characteristics was studied to assess the treatment efficiency. The results showed that the acidic conditions in the anodic sediments caused the dissolution of carbonates (calcite, dolomite, and aragonite), resulting in a considerable reduction in As, Zn, and Pb. Additionally, Cl as well as electric conductivity were significantly reduced from most sediments, which is essential in agricultural practices. Furthermore, materials had precipitated and settled in the anolyte and catholyte chambers, which acted as sorbents for elements that were released from the sediments (mainly Zn and As). Finally, three distinct phases occurred during treatment and were mainly linked to the current intensity and electric conductivity on the one hand, and the dissolution of carbonates and metal(loid) release on the other. This approach can be used to treat sediments and other media to improve the overall efficiency of remediation processes and create an end product with desired characteristics.

Association of Endogenous Seminal L-Carnitine Levels with Post-Thaw Semen Parameters in Humans

Cryopreservation of semen is a useful tool for male fertility preservation. Some evidence for a beneficial effect of L-carnitine supplementation of freezing media on cryopreserved semen samples has been reported. Here, we examined the association of endogenous levels of seminal L-carnitine with post-thaw semen parameters. We also investigated the effect of freezing medium supplemented with L-carnitine on sperm characteristics, related to endogenous seminal L-carnitine levels. Semen analyses were performed on 125 fresh samples, and after standard cryopreservation and with L-carnitine as a supplement. Participants were categorized into two groups based on the median levels of endogenous seminal L-carnitine: low L-carnitine (≤38.8 µg/ml) and high L-carnitine (>38.8 µg/ml). After standard cryopreservation, semen samples with high L-carnitine levels showed higher rapid progressive, progressive and total sperm motility and a reduced seminal static oxidation–reduction potential (ORP) level than samples with low L-carnitine levels. Only in post-thaw samples with low L-carnitine levels, there was an increase in the amount of sperm neck midpiece defects, compared to the fresh samples. Cryopreservation with L-carnitine had the most beneficial effect on rapid progressive sperm motility in samples with high endogenous L-carnitine levels. In conclusion, L-carnitine has a beneficial impact on sperm characteristics in post-thaw samples both as an endogenous component in seminal plasma and as a supplement in the freezing medium, by improving sperm motility and reducing seminal oxidative stress.

Effect of Humic Acid Fertilizer on Mercury Release from Greenhouse Soils

The elemental mercury (Hg0) release characteristics from the Hg-contaminated soil applied with Humic acid fertilizer (HAF) in the greenhouse were identified. The adsorption features of mercuric ion (Hg2+) on HAF under different reaction times and pH were investigated to elucidate the influencing mechanism of HAF on soil Hg0 release. Besides, the microstructure of HAF loading with Hg2+ was characterized by using Fourier transform infrared spectroscopy (FTIR) and scanning electron micrograph-energy dispersive spectrometry–EDS). The results showed that with the increasing HAF dosage, soil oxidation-reduction potential (Eh), and organic matter (SOM) content, as well as the decreasing soil pH, the soil Hg0 release fluxes showed a decreasing tendency. The soil pH, Eh, SOM, and total Hg content are the key factors that can affect the soil Hg0 release fluxes. The interior air temperature, light intensity, soil moisture, and soil temperature have little impact on soil Hg0 release fluxes when the greenhouse soil is applied with HAF. The HAF can immobilize Hg2+ and reduce its activity by surface precipitation and specific adsorption, then affecting the soil Hg0 release fluxes. The results of this study provide a basis for the application of HAF to reduce soil Hg0 release fluxes in the greenhouse of Hg-contaminated areas.

Application of Slightly Acidic Electrolyzed Water as a Potential Sanitizer in the Food Industry

The food industry has extensively explored postharvest microbial control, seeking viable technologies to ensure food safety. Although numerous chlorine-based commercial sanitizers serve this purpose, many are plagued by constraints such as instability and diminished disinfectant efficacy. These issues arise from exposure to organic matter in wash water, light, or air. As an innovative and promising alternative, slightly acidic electrolyzed water (SAEW) has emerged, captivating attention for its robust sterilization potential and eco-friendliness in agricultural and food sectors. SAEW generated via electrolysis of a diluted hydrochloric acid (HCl) solution with concentrations ranging from 2 to 6% or aqueous solution of sodium chloride (NaCl) in a nonmembrane electrolytic chamber is reported to possess equivalent antimicrobial properties as strong acidic electrolyzed water (StAEW). In contrast to traditional chlorine sanitizers, SAEW leaves less chlorine residue on sanitized foods such fresh-cut fruit and vegetables, meat, poultry, and aquatic products due to its low available chlorine concentration (ACC). Its near neutral pH of 5 to 6.5 not only renders it environmentally benign but also mitigates the production of chlorine gas, a contrast to low pH conditions seen in StAEW generation. The bactericidal effect of SAEW against various strains of foodborne pathogens is widely believed and accepted to be due to the combined action of high oxidation-reduction-potential (ORP) reactions and undissociated hypochlorite/hypochlorous acid (HOCl). Consequently, a burgeoning interest surrounds the potential of SAEW for sanitation in the food industry, offering an alternative to address shortcomings in sodium hypochlorite solutions and even StAEW. It has been hypothesized from a number of studies that SAEW treatment can increase the quality and nutritional value of harvested fruits, which in turn may enhance their ability to be stored. Therefore, SAEW is not only a promising sanitizer in the food industry but also has the potential to be an efficient strategy for encouraging the accumulation of bioactive chemicals in plants, especially if it is used extensively. This review encapsulates the latest insights concerning SAEW, encompassing its antimicrobial effectiveness, sanitization mechanism, advantages vis-à-vis other sanitizers, and plausible applications across the food industry.

Smart Strategic Management for the Cold Plasma Process Using ORP Monitoring and Total Organic Carbon Correlation

Assessing oxidation–reduction potential (ORP) is of paramount importance in the efficient management of wastewater within both chemical and biological treatment processes. However, despite its critical role, insufficient information exists about how reactive chemical species generated by cold plasma (CP) in chemical treatment are associated with ORP and air flow rate. Therefore, we aim to identify the correlation between ORP and the removal of organic pollutants when using CP treatment. Additionally, we introduce a machine-learning-based operation to predict removal efficiency in the CP process. Results reveal a significant correlation of over 0.9 between real-time ORP and total organic carbon (TOC), which underscores the efficacy of ORP as a key parameter. This approach made it possible to control OH radical generation by regulating the air flow rate of the CP. This study posits that smart management facilitated by machine learning has the potential to enhance the economic viability of CP feasibility while maintaining overall treatment performance.

Unveiling salinity-driven shifts in microbial community composition across compartments of naturally saline inland streams

Riverine environments host diverse microbial communities, exhibiting distinctive assemblies at both microscopic and macroscopic levels. Despite the complexity of microbial life in rivers, the underlying factors that shape the community structure across different compartments remain elusive. Herein, we characterized microbial community composition of biofilm and planktonic (water column) compartments in five naturally saline inland streams and a freshwater stream to examine changes in microbial communities following salinization via sequencing of the microbial 16S rRNA gene. Significant differences in specific conductivity, oxidation–reduction potential, dissolved oxygen, and pH among the sampled streams were measured, as were significant differences in the microbial community composition between the planktonic and biofilm. The bacterial families Bacillaceae, Vicinamibacterceae, and Micrococcaceae were significantly more abundant in the biofilm compartment, while Methylophilaceae, Alcaligenaceae, Spirosomaceae, Burkholderiaceae, and Comamonadaceae were more abundant in the planktonic compartment. In addition, salinity (based on specific conductivity) influenced the microbial community composition in both compartments, with higher sensitivity of the planktonic compartment. Increases in the bacterial families Shewanellaceae, Marinomonadaceae, and Saccharospirillaceae or loss of Anaeromyxobacteraceae could be indicative of increased salinity within inland streams. Our results suggest that monitoring of microbial assemblages of freshwater ecosystems could be used as early warning signs of increased salinization levels.

New insights for simultaneous nutrient removal enhancement and greenhouse gas emissions reduction of constructed wetland by optimizing its redox environment through manganese oxide addition

Manganese oxide (MnOx) is receiving increased interest in the nutrient removal of constructed wetlands (CWs); however, its service effectiveness for simultaneous greenhouse gas (GHG) emissions reduction is still vague. In this study, three vertical flow CWs, i.e., volcanics (CCW), manganese sand uniformly mixing with volcanics (Mn-CW) and MnOx doped volcanics (MnV-CW), were constructed to investigate the underlying mechanisms of MnOx on nutrient removal enhancement and greenhouse gas (GHG) emissions reduction. The results showed that the MnOx doped volcanics optimized the oxidation–reduction potential surrounding the substrate (-164.0 ∼ +141.1 mv), and resulted in the lowest GHG emissions (CO2-equivalent) from MnV-CW, 16.8–36.5 % lower than that of Mn-CW and CCW. This was mainly ascribed to mitigation of N2O produced during the NO3−-N reduction process, according to results of 15N stable isotope labeling. Analysis of the microbial community structure revealed that due to the optimized redox conditions through chemical doping of MnOx on volcanics, the abundance of microbe involved in denitrification and Mn-oxidizing process in the MnV-CW was significantly increased at genus level, which led to a higher Mn cycling efficiency between biogenic MnOx and Mn2+, and enhanced denitrification efficiency and N2O emission reduction. This study would help to understand and provide a preferable reference for future applications for manganese-based CW.

Behaviour of redox-sensitive elements (Ti, As, V and Fe) in clay pit samples with and without Al normalization

Natural clay minerals, because of their physical and chemical characteristics are good adsorbents of metals. Among metals, heavy metals are often investigated, but redox-sensitive metals are increasingly getting attention. Redox-sensitive elements were measured in clay pit samples from a clay mine in Bosnia and Herzegovina. For the purpose of analysis, a 23 m deep clay pit core sample was taken, and it was randomly subsampled to give 45 clay pit samples from different depths. The pH, electrical conductivity (EC), oxidation–reduction potential (ORP) and redox-sensitive elements contents were measured. Amounts of redox-sensitive metals and aluminium were measured with an inductively coupled plasma optical emission spectrophotometry instrument. For statistical evaluation, maximum, minimum, average, median, Pearson's prior correlation, correlation applying Al normalization and centred log-ratio (clr) transformation were calculated. When justified, principal component analysis (PCA) was also performed. The results show acidic pH and oxidative ORP. EC varied significantly through the sediment. The element concentrations lie in the sequence: Fe > Ti > V > As. There is a significant change in correlations with and without Al normalization. The highest difference was found for Ti and V (coefficient of correlation ( r ) value ranging from −0.553 to 0.835). Correlations and PCA after clr transformation showed mainly strong negative correlations, meaning that redox-sensitive elements behave differently in clay samples. Supplementary material: Graphical abstract is available at https://doi.org/10.6084/m9.figshare.c.7014329